JP4410630B2 - Vehicle steering device - Google Patents

Description

  The present invention relates to a steering wheel operated by a driver to steer a vehicle, a steering actuator for steering a steered wheel, and a steered wheel by driving and controlling the steered actuator according to the operation of the steering handle. The present invention relates to a steering device for a steering-by-wire vehicle including a steering control device that steers the vehicle.

  In recent years, the development of this type of steering-by-wire steering apparatus has been actively carried out. For example, Patent Document 1 below detects a steering angle and a vehicle speed, calculates a transmission ratio that decreases as the steering angle increases and increases as the vehicle speed increases, and divides the steering angle by this transmission ratio to thereby calculate the front wheel A steering device is shown in which a turning angle (amount of displacement of the rack shaft) is calculated and the front wheels are turned to the calculated turning angle. Further, in this steering device, the steering response and followability of the front wheels are improved by correcting the calculated turning angle in accordance with the steering speed obtained by time-differentiating the detected steering angle. Further, by calculating the target yaw rate using the detected vehicle speed and the detected steering wheel angle, and correcting the calculated turning angle according to the difference between the calculated target yaw rate and the detected actual yaw rate, the vehicle behavior state Steering control that takes into account is also realized.

Further, in Patent Document 2 below, the steering torque and the steering angle of the steering wheel are detected, two turning angles that increase as the steering torque and the steering wheel steering angle increase are calculated, and these calculated turning angles are added. A steering device is shown in which the front wheels are steered at the steered angle. In this steering apparatus, the vehicle speed is also detected, the both turning angles are corrected based on the detected vehicle speed, and the turning characteristics are changed according to the vehicle speed.
JP 2000-85604 A Japanese Patent Laid-Open No. 11-124047

  However, in any of the above conventional devices, the steering angle and the steering torque, which are the operation input values for the steering wheel by the driver for steering the vehicle, are detected, and the front wheels are detected using these detected steering angles and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, although the steering control of these front wheels has removed the mechanical connection between the conventional steering wheel and the steered wheel, the steering method of the front wheel with respect to the steering wheel operation is as follows: The basic technical idea of determining the steering angle of the front wheels according to the force is exactly the same, and in these steering methods, the steering angle of the front wheels is not determined according to human sensory characteristics So it was difficult to drive the vehicle.

  That is, in the conventional apparatus, the turning angle that cannot be perceived by the driver is determined directly in response to the operation of the steering wheel, and the vehicle turns by turning the front wheels according to the turning angle. . The driver senses the lateral acceleration, yaw rate, and turning curvature of the vehicle resulting from the turning of the vehicle by touch or vision, and feeds back to the operation of the steering wheel to turn the vehicle in a desired manner. In other words, since the turning angle of the front wheels with respect to the steering wheel operation by the driver is a physical quantity that cannot be perceived by humans, the turning angle directly determined by the driver's steering operation is the driver's perception. It was not determined according to the characteristics, and this made it difficult to drive the vehicle.

  In the above-described conventional device, in particular, when the vehicle is traveling (moving) at a low speed, the driver may not be able to perceive the lateral acceleration, the yaw rate, and the turning curvature caused by the turning of the vehicle. In this case, since the turning angle of the front wheels is a physical quantity that cannot be perceived by humans, the driver needs to operate the steering wheel based on the experience so far. In particular, when a vehicle equipped with a conventional mechanically-coupled steering device is switched to a vehicle equipped with a steering-by-wire steering device, the steering characteristics cannot be acquired. For this reason, a sense of incongruity occurs between the driver's perceptual characteristics and the steering characteristics, making it difficult to drive the vehicle.

  Further, in the above-described conventional device, the determined turning angle is corrected according to the difference between the target yaw rate calculated using the detected vehicle speed and the detected steering wheel angle, and the detected actual yaw rate. The steering angle is simply corrected in consideration of the behavior state of the vehicle, and the steering angle is not determined according to the yaw rate that the driver will perceive by operating the steering wheel. Therefore, in this case as well, the turning angle determined for the driver's steering operation is not determined in accordance with the driver's perceptual characteristics, making it difficult to drive the vehicle.

  In order to cope with the above problem, the present inventors have worked on research on a vehicle steering apparatus that can steer a vehicle in accordance with human perceptual characteristics in response to an operation of a steering wheel by a driver. Regarding such human perceptual characteristics, according to Weber-Fechner's law, it is said that the human sensory quantity is proportional to the logarithm of the physical quantity of the given stimulus. In other words, if the physical quantity of a stimulus given to a human being is changed exponentially or exponentially with respect to the human operating quantity, the relationship between the operating quantity and the physical quantity can be matched to the human perceptual characteristics. it can. The present inventors applied the Weber-Hefner's law to the steering operation of the vehicle, and discovered the following.

  When driving the vehicle, the vehicle turns by operating the steering handle, and the vehicle's motion state quantities such as lateral acceleration, yaw rate, and turning curvature change as the vehicle turns. And it feels more visually. Therefore, if the vehicle motion state quantity that can be perceived by the driver is changed exponentially or by a power function in response to the driver's operation on the steering wheel, the driver can adjust to the perceptual characteristics. The vehicle can be driven by operating the steering wheel.

  The present invention is based on the above discovery, and an object of the present invention is to provide a steering-by-wire vehicle steering device that facilitates driving of the vehicle by steering the vehicle in accordance with human perceptual characteristics.

In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. A steering-by-wire vehicle steering apparatus comprising: a steering control device that drives and controls the steering actuator to steer the steered wheels; and the steering control device is operated by a driver's operation input to the steering handle. An operation input value detecting means for detecting a value and a vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and is in a predetermined exponential relationship or a power relationship with the operation input value for the steering wheel. A motion state quantity calculating means for calculating a predicted motion state quantity of the vehicle using the detected operation input value, and the vehicle moves with the calculated expected motion state quantity. First turning angle calculation means for calculating a first turning angle of the steered wheels necessary for the purpose using the calculated expected motion state quantity in the exponential relationship or power relationship, and the operation input value detection A second turning angle calculation means for calculating a second turning angle of the steered wheel that is proportional to the operation input value detected by the means, and a first turning angle calculated by the first turning angle calculation means. the ratio rate of the second turning angle with increasing the ratio of the second turning angle is changed when the running distance of the vehicle is small that is calculated by the second turning angle calculating means, and the modified Ratio changing means for calculating the turning angle by adding the first turning angle and the second turning angle based on the ratio, and controlling the turning actuator according to the calculated turning angle to control the turning. The steering wheel is constituted by a steering control means for steering the steered wheel to the calculated steering angle.

In this case, includes a vehicle speed detecting means for detecting a vehicle speed of vehicles, the ratio changing means is for changing the ratio in accordance with the vehicle speed detected by the vehicle speed detecting means, the detected vehicle speed When the ratio is small, the ratio of the second turning angle may be increased. In addition, the second turning angle calculation means calculates the second turning angle near the neutral position of the steering handle based on the proportional relationship when the vehicle speed detected by the vehicle speed detection means is less than a predetermined vehicle speed. It is good to calculate based on the predetermined relationship which becomes a small variation | change_quantity compared with the variation | change_quantity with respect to the said operation input value of the calculated 2nd steering angle. The predetermined relationship used by the second turning angle calculation means may be a predetermined exponent relationship with the operation input value.

Another feature of the present invention is that a steering handle operated by a driver to steer the vehicle, a steering actuator for turning a steered wheel, and the steering according to an operation of the steering handle. In a steering-by-wire vehicle steering apparatus including a steering control device that drives and controls an actuator to steer a steered wheel, the steering control device detects an operation input value of a driver for the steering handle. An operation input value detection means; a first operation force calculation means for calculating a first operation force applied to the steering wheel, which is exponentially related to the operation input value detected by the operation input value detection means; A second operating force calculation unit that calculates a second operating force that is proportional to the operation input value detected by the operation input value detection unit and that is applied to the steering wheel; The first operating force and the second operating force ratio between the second operating force calculated by said second operating force calculating means when the operation input value for the steering wheel is small, which is calculated by the first operating force calculation means A ratio changing means for calculating the operating force applied to the steering wheel by adding the first operating force and the second operating force based on the changed ratio, and turning the vehicle Representing the motion state of the vehicle that can be perceived by the driver in relation to the vehicle, and the predicted motion state amount of the vehicle having a predetermined exponential relationship or a power relationship with the operation force applied to the steering wheel. The motion state quantity calculating means for calculating using the operation force, and the turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity are the calculated exponential relation or power relation. Ah Steering angle calculation means for calculating using the predicted motion state quantity, and a steering wheel for controlling the steering actuator according to the calculated steering angle to steer the steered wheel to the calculated steering angle. It is also composed of rudder control means.

In this case, includes a vehicle speed detecting means for detecting a vehicle speed of vehicles, the ratio changing means is for changing the ratio in accordance with the vehicle speed detected by the vehicle speed detecting means, the detected vehicle speed When the ratio is small, the ratio of the second operating force may be increased. Further, the second operating force calculation means compares the second operating force in the vicinity of the neutral position of the steering wheel with a change amount of the second operating force calculated based on the proportional relationship with respect to the operation input value. It is good to calculate based on the predetermined relationship which becomes a small change amount. The predetermined relationship used by the second operating force calculation means may be a predetermined exponent relationship with the operation input value.

  Another feature of the present invention is that the operation input value detecting means is constituted by, for example, a displacement amount sensor for detecting the displacement amount of the steering handle, and the motion state amount calculating means is the detected displacement amount. It is good to comprise the operation force conversion means which converts into the operation force given to the steering wheel, and the movement state quantity conversion means which converts the converted operation force into the expected movement state quantity. Further, the operation input value detection means is constituted by, for example, an operation force sensor that detects and outputs an operation force input to the steering handle, and the motion state quantity calculation means is configured to use the detected operation force as the operation force. It is good to comprise at the exercise state quantity conversion means which converts into an estimated exercise state quantity.

  In these cases, the expected motion state quantity is, for example, any one of the lateral acceleration, the yaw rate, and the turning curvature of the vehicle. Further, in this vehicle steering device, a reaction force device for applying a reaction force to the operation of the steering wheel may be further provided.

  In the present invention configured as described above, an operation input value (for example, a steering angle or an operation force) input to the steering wheel represents a motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle. Thus, it is converted into a predicted motion state quantity (lateral acceleration, yaw rate, turning curvature, etc.) of the vehicle that has a predetermined exponential relationship or a power relationship with the operation input value for the steering wheel. Then, the first turning angle of the steered wheels necessary for the vehicle to move with the expected movement state quantity is calculated based on the converted expected movement state quantity, and is proportional to the operation input value. The second turning angle at is calculated. Then, the ratio between the first turning angle and the second turning angle is changed according to the vehicle speed and the travel distance, the turning angle is calculated, and the steered wheels are steered to the calculated turning angle.

  When changing the ratio, when the vehicle speed is high or the mileage is large and the driver has sufficiently mastered the steering characteristics of the steering device, the ratio of the first turning angle is increased so that the steered wheels become the first one. It is steered to the steered angle. Therefore, when the vehicle turns at the first turning angle, the driver is given the expected motion state quantity as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. The expected motion state quantity changes exponentially or exponentially with respect to the operation input value to the steering wheel, in other words, the operation input value. The steering wheel can be operated while perceiving the amount of motion state. The lateral acceleration and yaw rate can be sensed tactilely by the driver in contact with each part in the vehicle. Further, the turning curvature can be visually perceived by the driver due to changes in the situation within the field of view of the vehicle. As a result, according to the present invention, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

  Further, when changing the ratio, when the vehicle speed is low or the mileage is short and the driver has not sufficiently mastered the steering characteristics of the steering device, the ratio of the second turning angle is increased to increase the turning wheel. Is steered to the second steered angle. Therefore, when the vehicle turns at the second turning angle, the driver can turn the vehicle at a turning angle proportional to a steering input value (for example, a steering angle or an operating force) to the steering handle. Even if the acquisition of characteristics is insufficient, the vehicle can be easily turned based on experience with a conventional mechanically coupled steering device.

  In particular, when the vehicle speed is less than a predetermined vehicle speed, for example, by reducing the amount of change with respect to the operation input value of the second turning angle near the neutral position of the steering wheel according to a predetermined exponential function, Can be prevented from vibrating. That is, when the amount of change in the second turning angle that is proportional to the operation input value is large near the neutral position of the steering wheel, the steered wheels cannot be smoothly returned to the straight running position. For this reason, when the driver returns the steering handle to the neutral position, the steered wheel may be steered to the straight position suddenly. In this case, there is a possibility that the steered wheel steers across the straight traveling position. As a result, the steered wheel vibrates to the left and right in the vicinity of the straight traveling position, and then the vibration stops. On the other hand, by reducing the amount of change in the second turning angle with respect to the operation input value, the steered wheels can be smoothly (slowly) steered to the straight running position when the steering handle is returned to the neutral position. Therefore, vibration in the left-right direction of the steered wheels can be effectively prevented.

  Further, in the present invention configured as described above, based on the steering angle input to the steering wheel, the second operating force that is proportional to the first operating force that is in the exponential relationship is calculated, and the vehicle speed and the input are input. The operation force is calculated by changing the ratio of the first operation force and the second operation force according to the steering angle. This calculated operating force represents the vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and the expected motion of the vehicle that has a predetermined exponential or exponential relationship with the operation input value to the steering wheel. It is converted into a state quantity (lateral acceleration, yaw rate, turning curvature, etc.). Then, the turning angle of the steered wheels necessary for the vehicle to move with the expected motion state quantity is calculated based on the converted expected motion state quantity, and the steered wheels are steered to the calculated turning angle. Is done.

  For this reason, when the vehicle speed is high or the steering angle is large, by increasing the ratio of the first operating force, the operating force changes exponentially with respect to the steering angle. The steering wheel can be operated in a state that matches human perception characteristics. Accordingly, the driver can operate the steering wheel while perceiving the operating force that changes exponentially as the “physical quantity of the applied stimulus” according to the Weber-Hefner law, and thus the driving of the vehicle is simplified.

  Here, the magnitudes of the first operating force and the second operating force at the same steering angle are considered. Assuming that the first operating force and the second operating force can be changed up to the maximum preset operating force of the vehicle with respect to the magnitude of the steering angle, the second operating force The force is greater than the first operating force. Therefore, for example, the expected motion state quantities calculated based on the first operating force and the second operating force are calculated based on the first operating force when calculated based on the second operating force. As a result, the turning angle is also calculated to be larger. In other words, by increasing the operating force with respect to the steering angle, it is possible to turn quickly (that is, without turning delay) to the turning angle of the steered wheels requested by the driver. For this reason, when the vehicle speed is low or the operation input value (for example, the steering angle) is small, the steering delay time can be reduced by increasing the ratio of the second operation force, and the mechanical connection is established. Steering characteristics close to those of the conventional steering device can be obtained. Therefore, the driver can easily turn the vehicle based on the experience with the conventional mechanically connected steering device even if the acquisition of the steering characteristics is insufficient.

  Further, for example, by reducing the amount of change with respect to the operation input value of the second operating force in the vicinity of the neutral position of the steering wheel according to a predetermined exponential function, vibration in the turning direction of the steering wheel can be prevented. That is, if the amount of change in the second operating force that is proportional to the operation input value is large near the neutral position of the steering wheel, the steering wheel cannot be smoothly (gradually) returned to the neutral position. For this reason, when the driver returns the steering wheel to the neutral position, the steering wheel may be suddenly turned to the neutral position. In this case, there is a possibility that the steering handle rotates over the neutral position. As a result, the steering handle vibrates left and right in the vicinity of the neutral position, and then the vibration stops. On the other hand, by reducing the amount of change in the second operating force with respect to the operation input value near the neutral position, the steering handle can be smoothly returned to the neutral position. It can be effectively prevented.

  In addition, another feature of the present invention is that, in addition to the above-described configuration, the motion state quantity detecting means for detecting an actual motion state quantity that is the same type as the expected motion state quantity and represents the actual motion state of the vehicle, and the calculation. And a correction means for correcting the calculated turning angle in accordance with a difference between the estimated motion state quantity and the detected actual motion state quantity. According to this, the steered wheels are steered more accurately to the steered angle required for the vehicle to move with the calculated expected motion state quantity. As a result, the driver can operate the steering wheel while perceiving the amount of motion state that accurately matches the human perceptual characteristics, so that the driving of the vehicle is further simplified.

a. First Embodiment Hereinafter, a vehicle steering apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vehicle steering apparatus according to the first embodiment.

  The steering apparatus includes a steering handle 11 as an operation unit that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to a reaction force actuator 13 including an electric motor and a speed reduction mechanism. The reaction force actuator 13 applies a reaction force to the turning operation of the steering handle 11 by the driver.

  In addition, the steering device includes a steering actuator 21 including an electric motor and a speed reduction mechanism. The turning force by the turning actuator 21 is transmitted to the left and right front wheels FW1 and FW2 via the turning output shaft 22, the pinion gear 23, and the rack bar 24. With this configuration, the rotational force from the steering actuator 21 is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the rotation of the pinion gear 23. Due to the displacement in the axial direction, the left and right front wheels FW1, FW2 are steered left and right.

  Next, an electric control device that controls the rotation of the reaction force actuator 13 and the turning actuator 21 will be described. The electric control device includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ) Is output. Note that the steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as positive and rightward acceleration as negative.

  These sensors 31 to 34 are connected to the electronic control unit 35. The electronic control unit 35 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operations of the reaction force actuator 13 and the turning actuator 21 by executing programs. Drive circuits 36 and 37 for driving the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  Next, the operation of the first embodiment configured as described above will be described with reference to the functional block diagram of FIG. 2 showing functions realized by computer program processing in the electronic control unit 35. The electronic control unit 35 includes a reaction force control unit 40 for controlling the application of the reaction force to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's sensory characteristics based on the turning operation of the steering handle 11. A sensory adaptation control unit 50 for determining the target turning angle δd and a steering control unit 60 for controlling the steering of the left and right front wheels FW1, FW2 based on the target turning angle δd.

  When the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering handle 11, and uses the detected steering angle θ as the reaction force control unit 40 and the sense. Each is output to the matching control unit 50. In the reaction force control unit 40, when the steering handle 11 is turned by the driver, a turning operation that increases the absolute value of the detected steering angle θ (hereinafter, this turning operation is referred to as a cutting operation) is performed. The reaction force torque Tzf is calculated when the detected steering angle θ is smaller, and the reaction force torque Tzr is calculated when the rotation operation in which the absolute value of the detected steering angle θ is reduced (hereinafter, this rotation operation is referred to as a return operation). Calculate

  Here, the detection of the cutting operation and the return operation will be described. Now, considering the case where the steering handle 11 is turned rightward, the detected steering angle θ output from the steering angle sensor 31 is a negative value. In this state, when the steering handle 11 is turned, if the time differential value θ ′ of the detected steering angle θ is a negative value, it is detected that the driver has performed a cutting operation, and the differential value θ ′. If is a positive value, it is detected that a return operation has been performed by the driver. On the other hand, when the case where the steering handle 11 is rotated to the left is considered, the detected steering angle θ output from the steering angle sensor 31 is a positive value. In this state, when the steering handle 11 is turned, if the time differential value θ ′ of the detected steering angle θ is a positive value, it is detected that the driver has performed a cutting operation, and the differential value θ ′. If is a negative value, it is detected that a return operation has been performed by the driver.

  Further, when detecting the cutting operation and the returning operation, as will be described in detail later, calculation processing such as reaction force application control processing and target turning angle determination processing is switched and executed in accordance with the detected cutting operation or returning operation. Therefore, a dead zone is provided between the cutting operation and the returning operation. That is, if the driver performs a cutting operation or a return operation and simultaneously detects these operations, for example, even when the driver rotates the steering handle 11 in the left-right direction for fine adjustment. Each time, the calculation process is switched. As described above, when the calculation process is frequently switched, there arises a problem that, for example, the reaction force perceived by the driver via the steering wheel 11 varies. On the other hand, by providing a dead zone for the detection of the cutting operation and the returning operation, it is possible to prevent the cutting operation or the returning operation from being frequently detected due to the fine adjustment of the driver. Is solved. Here, as the dead zone, for example, a detection time until the cutting operation and the return operation are detected can be adopted, and the detection time may be set longer than the detection time of the cutting operation. . Thereby, in particular, the calculation frequency of a reaction force torque Tzr, which will be described later, is reduced along with the return operation, and the uncomfortable feeling that the driver learns via the steering handle 11 can be reduced.

Next, the calculation of the displacement-torque conversion unit 41 will be specifically described from the case where the cutting operation is performed. If the absolute value of the detected steering angle θ of the steering handle 11 is less than the positive predetermined steering angle θz, the displacement-torque conversion unit 41 calculates a reaction force torque Tzf that is a linear function of the steering angle θ according to the following equation 1. If the absolute value of the detected steering angle θ is equal to or greater than the positive predetermined steering angle θz, the reaction force torque Tzf that is an exponential function of the steering angle θ is calculated according to the following equation 2. Here, the linear function of the following formula 1 and the exponential function of the following formula 2 are continuously connected at the steering angle θz. For example, the origin “0” at the steering angle θz in the exponential function of the following formula 2 Can be employed as a linear function of Equation 1 below. The following formula 1 is not limited to a linear function, and the reaction torque Tzf is “0” when the steering angle θ is “0”, and continuously with the exponential function of the following formula 2. Various functions can be employed as long as they are connected functions.
Tzf = a1 ・ θ (| θ | <θz)… Formula 1
Tzf ＝ To ・ exp (K1 ・ θ) (θz ≦ | θ |)

On the other hand, when the return operation is performed, the displacement-torque conversion unit 41 determines that the primary value of the steering angle θ according to the following equation 3 if the absolute value of the detected steering angle θ of the steering handle 11 is less than the positive predetermined steering angle θz. A reaction force torque Tzr, which is a function, is calculated. If the absolute value of the detected steering angle θ is greater than or equal to a predetermined positive steering angle θz, a reaction force torque Tzr that is an exponential function of the steering angle θ is calculated according to the following equation 4. The linear function of the following formula 3 and the exponential function of the following formula 4 in this return operation are also continuously connected at the steering angle θz, as in the above-described formulas 1 and 2 of the cutting operation. A tangent line passing through the origin “0” at the steering angle θz in the exponential function of the following formula 4 can be adopted as a linear function of the following formula 3. Also in this case, the following equation 3 is not limited to a linear function, and the reaction torque Tzr becomes “0” when the steering angle θ is “0”, and the exponential function of the following equation 4 Various functions can be adopted as long as the functions are continuously connected to each other.
Tzr = a2 ・ θ−Mh1 (| θ | <θz) Equation 3
Tzr ＝ To ・ exp (K1 ・ θ) −Mh1 (θz ≦ | θ |) Equation 4

  Here, a1 in the formula 1 and a2 in the formula 3 are constants representing the slope of the linear function described above. In addition, To and K1 in the equations 2 and 4 are both constants. In particular, the constant To is the minimum steering torque that can be perceived by the driver. The constant K1 will be described in detail when explaining the sensory adaptation control unit 50 described later. Further, the steering angle θ in the equations 1 to 4 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constants a1 and a2 and the constant To are set to negative values. If the detected steering angle θ is negative, the constants a1 and a2 and the constant To are positive values having the same absolute value as the negative constants a1 and a2 and the constant To.

Further, Mh1 in the equations 3 and 4 indicates that the calculated reaction force torque Tzf and reaction force torque Tzr are continuously obtained when the turning operation of the steering handle 11 by the driver is changed from the cutting operation to the returning operation. In other words, the hysteresis term is used to construct a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh1 is determined based on the ratio of the reaction force torque Tzf during the cutting operation and the reaction force torque Tzr during the return operation at the time when a certain steering angle θ is detected, and is expressed by the following equation (5). The
Mh1 = np · (Kp · Tzf) ... Formula 5
However, Kp in Equation 5 is a minimum change sensitivity (Weber ratio) with respect to a reaction torque Tzf described later, and np is a predetermined coefficient for the minimum change sensitivity.

  Since the hysteresis term Mh1 is calculated in this way, the reaction force torque Tzf calculated according to the equation 1 or 2 and the reaction force torque Tzr calculated according to the equation 3 or 4 are continuously connected. The driver can smoothly change from the cutting operation to the returning operation, and the driver does not feel uncomfortable. Since the hysteresis term Mh1 is calculated according to the above equation 5, the steering angle θ at the time when the cutting operation is changed to the returning operation is maintained. The amount of rotation of the steering wheel 11 can be made substantially the same, and in particular, the convergence of the steering handle 11 during the return operation can be ensured satisfactorily. In the present embodiment, the hysteresis term Mh1 is derived so as not to include the steering angle θ as shown in Equation 5, but instead of or in addition, for example, the hysteresis term Mh1 includes the steering angle θ. It is also possible to derive so as to depend on the steering angle θ.

  Further, when the detected steering angle θ is less than the steering angle θz, the reaction force torque Tzf and the reaction force torque Tzr are calculated according to the above formulas 1 and 3, whereby the steering handle 11 rotates across the neutral position. Even when the operation is performed, since the equations 1 and 3 are functions passing through the origin “0”, the reaction force torque Tzf and the reaction force torque Tzr are prevented from becoming discontinuous. Specifically, for example, consider a case where the driver performs a turning operation of the steering handle 11 to the right by the steering angle θz or more and then returns to the left (that is, the neutral position). At this time, the absolute value of the detected steering angle θ decreases with the return operation of the steering handle 11 to the left, and the displacement-torque conversion unit 41 calculates the reaction force torque Tzr according to Equation 3 below the steering angle θz. To do. When the absolute value of the detected steering angle θ becomes “0”, that is, when the steering handle 11 is turned to the neutral position, the displacement-torque converter 41 calculates the reaction torque Tzr as “0”.

  When the steering handle 11 is further rotated leftward beyond this neutral position, a leftward cutting operation is performed, so that the displacement-torque conversion unit 41 changes from “0” in a linear function according to the above equation 1. Calculate reaction torque Tzf. At this time, since the equation 3 for calculating the reaction force torque Tzr for the return operation and the equation 1 for calculating the reaction force torque Tzf for the cutting operation are both functions passing through the origin “0”, the returning operation (or the cutting) In the case of changing from an operation) to a cutting operation (or a return operation), the calculated reaction force torque Tzr and reaction force torque Tzf do not become discontinuous. Therefore, when the steering handle 11 is operated across the neutral position, in other words, even when the detected steering angle θ is reversed between positive and negative, the reaction torques Tzf and Tzr can be applied to the steering handle 11 very smoothly. The driver never feels uncomfortable. Further, the reaction torques Tzf and Tzr can be converged to “0” according to the above formulas 1 and 3, so that the vibration in the turning direction near the neutral position of the steering handle 11, that is, when the steering angle θ is near “0”. Can be prevented. In the calculation of the reaction force torque Tzf or the reaction force torque Tzr, the characteristic conversion as shown in FIG. 3 in which the reaction force torques Tzf and Tzr with respect to the steering angle θ are stored in place of the calculation of the equations 1-5. You may make it calculate using a table.

  The calculated reaction force torque Tzf or reaction force torque Tzr is supplied to the drive control unit 42. The drive control unit 42 receives a drive current that flows from the drive circuit 36 to the electric motor in the reaction force actuator 13, and the drive circuit so that a drive current corresponding to the reaction force torque Tzf or the reaction force torque Tzr flows to the electric motor. 36 is feedback controlled. By driving control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force torque Tzf or a reaction force torque Tzr to the steering handle 11 via the steering input shaft 12.

  Therefore, for example, when the driver turns the steering handle 11 from the neutral position, when the detected steering angle θ is less than the steering angle θz, the reaction force torque Tzf that changes in a linear function calculated according to the equation 1 is used. While feeling, and when the detected steering angle θ is equal to or larger than the steering angle θz, the steering handle 11 is turned while feeling the reaction force torque Tzf that changes exponentially calculated according to the above equation 2. On the other hand, for example, when the driver returns the steering handle 11 from a steering position where the detected steering angle θ is equal to or greater than the steering angle θz, the hysteresis term Mh1 is calculated according to the equation 5 and calculated according to the equation 4. While sensing the reaction force torque Tzr that varies exponentially, and when the detected steering angle θ is less than the steering angle θz, the hysteresis term Mh1 is calculated according to the above equation 5 and linearly calculated according to the above equation 3. The steering handle 11 is turned while feeling the changing reaction force torque Tzr.

  In this way, the driver feels the calculated reaction force torque Tzf or reaction force torque Tzr from the steering handle 11, in other words, applies a steering torque equal to these reaction force torque Tzf or reaction force torque Tzr to the steering handle. 11, the steering handle 11 is rotated. At this time, when the detected steering angle θ is equal to or larger than the steering angle θz, the relationship between the steering angle θ and the reaction force torque Tzf or the reaction force torque Tzr follows the above-mentioned Weber-Hefner law. The steering handle 11 can be rotated while receiving a sense from 11 that matches human perception characteristics.

On the other hand, when the steering angle θ input to the sensory adaptation control unit 50 is being turned by the driver, the displacement-torque conversion unit 51 performs steering torque Tdf according to the following formulas 6 and 7 similar to the above formulas 1 and 2. Calculate Further, when the driver is performing a return operation, the displacement-torque converter 51 calculates the steering torque Tdr according to the following equations 8 and 9 similar to the equations 3 and 4. Also in the calculation of the steering torques Tdf and Tdr, Equations 6 and 8 are not limited to linear functions. When the steering angle θ is “0”, the steering torques Tdf and Tdr are “0”, and As long as the functions are continuously connected to the exponential functions of Equations 7 and 9, various functions can be adopted.
Tdf = a1 · θ (| θ | <θz) (6)
Tdf = To · exp (K1 · θ) (θz ≦ | θ |) Equation 7
Tdr = a2 ・ θ−Mh1 (| θ | <θz)… Equation 8
Tdr = To · exp (K1 · θ) −Mh1 (θz ≦ | θ |) Equation 9

Also in this case, a1 in the equation 6 and a2 in the equation 8 are constants representing the slope of the linear function described above. In addition, To and K1 in the expressions 7 and 9 are constants similar to the expressions 2 and 4. Further, the steering angle θ in the equations 6 to 9 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constants a1 and a2 and the constant To are positive. If the detected steering angle θ is negative, the constants a1 and a2 and the constant To are negative values having the same absolute value as the positive constants a1 and a2 and the constant To. Further, Mh1 in the equations 8 and 9 is a hysteresis term for constituting a hysteresis characteristic between the cutting operation and the returning operation, as in the equations 3 and 4. This hysteresis term Mh1 is also determined based on the ratio between the steering torque Tdf at the time of the cutting operation and the steering torque Tdr at the time of the return operation at the time when a certain steering angle θ is detected, and is expressed by the following equation (10).
Mh1 = np · (Kp · Tdf) Equation 10
However, as in Equation 5, Kp in Equation 10 is the minimum change sensitivity (Weber ratio) with respect to the steering torque Tdf, and np is a predetermined coefficient for the minimum change sensitivity.

  Also in the calculation of the steering torques Tdf and Tdr, as in the calculation of the reaction force torques Tzf and Tzr described above, the hysteresis term Mh1 is calculated according to the above equation 10, so that the steering torque calculated according to the above equations 6 and 7 is obtained. Since Tdf and the steering torque Tdr calculated according to the equations 8 and 9 are continuously connected, the cutting operation can be smoothly changed to the returning operation. Further, when the detected steering angle θ is less than the steering angle θz, the steering torque Tdf and the steering torque Tdr are calculated according to the equations 6 and 8, so that the steering torques Tdf and Tdr can be converged to “0”. In addition, the steering torque Tdf and the steering torque Tdr can be changed continuously (smoothly) even if the steering handle 11 is rotated across the neutral position. In this case as well, instead of the calculations of the above formulas 6 to 10, the steering torques Tdf and Tdr are converted using the characteristic conversion table shown in FIG. 3 in which the steering torque Tdf and the steering torque Tdr with respect to the steering angle θ are stored. May be calculated.

  The steering torques Tdf and Tdr calculated in this way are supplied to the torque-lateral acceleration conversion unit 52. The torque-lateral acceleration conversion unit 52 performs the calculation described later in the same manner regardless of the steering torques Tdf and Tdr supplied from the displacement-torque conversion unit 51. The torques Tdf and Tdr will be collectively described as the steering torque Td. The torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gdf that the driver expects by the turning operation of the steering wheel 11 according to the following equations 11 and 12, and calculates the expected lateral acceleration Gdr that is expected by the return operation by the following equation 13: , 14 according to the calculation.

At this time, the torque-lateral acceleration conversion unit 52 calculates the expected lateral accelerations Gdf and Gdr according to the following formulas 11 and 13 if the absolute value of the steering torque Td is less than the positive predetermined value Tg, and the absolute value of the steering torque Td. If the value is equal to or greater than the positive predetermined value Tg, the calculation is performed according to the following equations 12 and 14. Here, the following Expression 11 or Expression 13 is a linear function expression of the steering torque Td, and is a function in which the expected lateral accelerations Gdf and Gdr are “0” when the steering torque Td is “0”. Further, the following formulas 12 and 14 are power functions of the steering torque Td, and are continuously connected to the following formulas 11 and 13 at a predetermined value Tg.
Gdf = b1 · Td (| Td | <Tg) Equation 11
Gdf = C · Td ^K2 (Tg ≦ | Td |) Equation 12
Gdr = b2 · Td−Mh2 (| Td | <Tg) Equation 13
Gdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 14

  However, b1 in the formula 11 and b2 in the formula 13 are constants representing the slope of a linear function, and C and K2 in the formulas 12 and 14 are constants. Further, the steering torque Td in the equations 11 to 14 represents the absolute value of the steering torque Td calculated using the equations 6 to 10 (that is, the steering torques Tdf and Tdr), and the calculated steering torque. If Td is positive, the constants b1, b2 and constant C are positive values. If the calculated steering torque Td is negative, the constants b1, b2 and constant C are changed to the positive constants b1, b2 and constant C. A negative value having the same absolute value as

Further, Mh2 in the above formulas 13 and 14 indicates that the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are continuously calculated when the turning operation of the steering handle 11 by the driver is changed from the cutting operation to the returning operation. In other words, the hysteresis term is used to construct a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh2 is determined based on the ratio between the expected lateral acceleration Gdf at the time of the cutting operation and the expected lateral acceleration Gdr at the time of the return operation at the time when a certain steering torque Td is supplied, and is expressed as the following Expression 15. The
Mh2 = nq · (Kq · Td) Equation 15
In Equation 15, Kq is a minimum change sensitivity (Weber ratio) with respect to a steering torque Td described later, and nq is a predetermined coefficient for the minimum change sensitivity. In the present embodiment, the hysteresis term Mh2 is derived so as not to include the steering angle θ as shown in the above formula 15. However, instead of or in addition to this, for example, the hysteresis term Mh2 includes the steering angle θ. It is also possible to derive so as to depend on the steering angle θ.

  Since the hysteresis term Mh2 is calculated in this way, the expected lateral acceleration Gdf calculated according to Equation 11 or Equation 12 and the expected lateral acceleration Gdr calculated according to Equation 13 or Equation 14 are continuously connected. , The expected lateral acceleration Gdf can be smoothly switched to the expected lateral acceleration Gdr, and conversely, the expected lateral acceleration Gdr can be smoothly switched to the expected lateral acceleration Gdf. Further, by calculating the hysteresis term Mh2 in accordance with Equation 15, the expected lateral accelerations Gdf and Gdr at the time of change between the cutting operation and the returning operation are maintained. Therefore, as will be described later, the left and right front wheels FW1 and FW2 steered to the corrected target turning angle δda calculated based on the expected lateral accelerations Gdf and Gdr are, for example, caused by disturbances input from the road. It is possible to prevent the turning angle δ from changing, and to maintain the behavior of the vehicle as expected by the driver.

  Further, when the steering torque Td is less than the predetermined value Tg, the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are calculated according to the above equations 11 and 13, whereby the steering handle 11 is turned over the neutral position. Even in this case, since the expression 11 and the expression 13 are functions passing through the origin “0”, the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are prevented from becoming discontinuous.

  In other words, when the value is less than the predetermined value Tg, both the expression 11 and the expression 13 are functions passing through the origin “0”. For this reason, if the driver expects the expected lateral acceleration, for example, a lateral acceleration that changes from the right direction to the left direction, the torque-lateral acceleration conversion unit 52 is linearly “0” according to the equation (13). And the expected lateral acceleration Gdf that increases linearly from “0” according to the above equation 11 is calculated. Therefore, the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are continuous at “0”, and when the perceived direction of the expected lateral acceleration changes, in other words, even when the detected steering angle θ reverses positively and negatively, the expected lateral acceleration Gdf The lateral acceleration Gdf, Gdr can be switched, and the driver does not feel uncomfortable. In this case as well, instead of the calculations of Equations 11 to 15, the expected lateral acceleration Gdf, Gdf, Gdr, which stores the expected lateral acceleration Gdf, Gdr with respect to the steering torque Td, is stored. Gdr may be calculated.

Here, Formula 12 applied at the time of the cutting operation will be described. The expression 14 applied during the return operation is configured in the same manner except that the steering torque Td in the expression 12 is expressed by the steering torque (Td−Mh2), so the expression 12 will be described in detail. Therefore, the description is omitted. When the steering torque Td is eliminated using the equation 7, the following equation 16 is obtained.
Gdf = C · (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1 · K2 · θ) = Go · exp (K1 · K2 · θ)
In Expression 16, Go is a constant C · To ^K2 , and Expression 16 indicates that the expected lateral acceleration Gdf varies exponentially with respect to the steering angle θ of the steering wheel 11 by the driver. Note that the expected lateral acceleration Gdr changes exponentially with respect to the steering angle θ by modifying the equation 14 using the equation 9 in the same manner as the transformation from the equation 12 to the equation 16 described above. The expected lateral acceleration Gdf is a physical quantity that can be perceived by the driver when a part of the body of the driver touches a predetermined part in the vehicle, and follows the Weber-Hefner law described above. Accordingly, if the driver can turn the steering handle 11 while perceiving a lateral acceleration equal to the expected lateral acceleration Gdf when the steering torque Td is equal to or greater than the predetermined value Tg, the turning operation of the steering handle 11 is performed. And the vehicle steering can be made to correspond to human perceptual characteristics.

Thus, the expected lateral acceleration Gdf shown in the equation 12 (that is, the equation 16) changes exponentially with respect to the steering angle θ, which is the operation amount of the steering wheel 11, and thus human perception. It suits the characteristics. Furthermore, the simplest method for the turning operation of the steering handle 11 by the driver is to turn the steering handle 11 at a constant speed ω (θ = ω · t). The acceleration Gdf changes exponentially with respect to time t as shown in the following equation (17). Therefore, it will be understood that if the steering handle 11 can be rotated while perceiving a lateral acceleration equal to the expected lateral acceleration Gdf, the driver can easily rotate the steering handle 11.
Gdf = Go · exp (K0 · ω · t) (Equation 17)
However, K0 is a constant having a relationship of K0 = K1 · K2.

  Further, as shown in Equation 11, when the steering torque Td is less than the predetermined value Tg, the expected lateral acceleration Gdf changes in a linear function. This is because when the steering torque Td is less than the predetermined value Tg, that is, when the steering angle θ is maintained near “0” (near the neutral position of the steering wheel 11), the expected lateral acceleration Gdf, When Gdr is calculated, the expected lateral accelerations Gdf and Gdr do not converge to “0”, which is not realistic. However, as described above, if the steering handle 11 is in the vicinity of the neutral position, that is, if the steering torque Td is less than the predetermined value Tg, the expected lateral acceleration Gdf, Gdr is calculated according to the above formulas 11 and 13, whereby the steering handle 11 is Since the expected lateral accelerations Gdf and Gdr converge to “0” when rotated in the neutral position direction, this problem is solved.

  Next, how to determine the parameters K1, K2, and C (predetermined values K1, K2, and C) used in Expressions 1 to 16 will be described. In the description of how to determine the parameters K1, K2, and C, the steering torques Tdf and Tdr and the expected lateral accelerations Gdf and Gdr in the expressions 1 to 16 are handled as the steering torque T and the lateral acceleration G. According to the Weber-Hefner law described above, “the ratio ΔS / S between the minimum physical quantity change ΔS perceivable by humans and the physical quantity S at that time is constant regardless of the value of the physical quantity S, and the ratio ΔS / S is called the Weber ratio. The present inventors confirmed that the above-mentioned Weber-Hefner's law is established with respect to steering torque and lateral acceleration, and in order to determine the Weber ratio, the following experiments were conducted for men and women, age, and driving of the vehicle. I went to various people with different histories.

  Regarding the steering torque, a torque sensor is assembled to the steering handle of the vehicle, and an inspection torque is applied to the steering handle from the outside and the inspection torque is changed in various manners against this inspection torque. We measured the ability of the human to adjust the steering torque to adjust the steering handle so that it does not rotate by applying an operating force to the steering handle. That is, under the above situation, when the detected steering torque at a certain time is T, and the minimum steering torque change amount that can perceive a change from the detected steering torque T is ΔT, the ratio value ΔT / T, that is, Weber The ratio was measured for various humans. According to the results of this experiment, the Weber ratio ΔT / T is almost constant for various humans regardless of the direction of operation of the steering wheel, the state of the hand holding the steering wheel, and the magnitude and direction of the inspection torque. The value α was obtained.

  Regarding the lateral acceleration, a wall member is provided on the side of the driver's seat, and a force sensor for detecting the pressing force of the human shoulder is assembled to the wall member to allow the human to grasp the steering handle and to the wall member force sensor. The wall is applied to the wall member with the inspection force from the outside in the lateral direction, and the wall is against the inspection force while changing the inspection force in various modes. We adjusted the lateral force adjustment ability of the human to push the member so that the wall member does not move, that is, maintain the posture. That is, when F is the detection force that can withstand lateral force from the outside at a certain time and maintain the posture under the above situation, and ΔF is the minimum force change amount that can perceive the change from the detection force F The ratio value ΔF / F, that is, the Weber ratio was measured for various humans. According to the results of this experiment, the Weber ratio ΔF / F was a substantially constant value β for various people regardless of the magnitude and direction of the reference force applied to the wall member.

On the other hand, when the equation 7 is differentiated and the equation 7 is considered in the differentiated equation, the following equation 18 is established.
ΔT = To · exp (K1 · θ) · K1 · Δθ = T · K1 · Δθ
When the equation 18 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is set to Kt, the following equation 19 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ Equation 19

If the maximum steering torque is Tmax, the following equation 20 is established from the above equation 7.
Tmax = To · exp (K1 · θmax) ... Equation 20
If the equation 20 is modified, the following equation 21 is established.
K1 = log (Tmax / To) / θmax Equation 21
Then, the following equation 22 is derived from the equations 19 and 21.
Δθ = Kt / K1 = Kt · θmax / log (Tmax / To)
In Equation 22, Kt is the Weber ratio of the steering torque T, θmax is the maximum value of the steering angle, Tmax is the maximum value of the steering torque, and To corresponds to the minimum steering torque that can be perceived by humans. Since these values Kt, θmax, Tmax, and To are all constants determined by experiments and systems, the differential value Δθ is calculated using the equation (22). A predetermined value (coefficient) K1 can also be calculated based on the equation 19 using the differential value Δθ and the Weber ratio Kt.

Further, when differentiating the expression 12 and considering the expression 12 in the differentiated expression, the following expression 23 is established.
ΔG = C · K2 · T ^K2-1 · ΔT = G · K2 · ΔT / T Equation 23
When Expression 23 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is set to Kt and the Weber ratio ΔF / F related to the lateral acceleration is set to Ka, the following Expressions 24 and 25 are established.
ΔG / G = K2 · ΔT / T Equation 24
K2 = Ka / Kt ... Formula 25
In this equation 25, Kt is the Weber ratio related to the steering torque, and Ka is the Weber ratio related to the lateral acceleration, both of which are given as constants. Therefore, using these Weber ratios Kt and Ka, the above equation is used. Based on 25, the coefficient K2 can also be calculated.

If the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following expression 26 is derived from the expression 12.
C = Gmax / Tmax ^K2 Equation 26
In Equation 26, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 25. Therefore, a constant (coefficient) C can also be calculated.

  As described above, the maximum value θmax of the steering angle θ, the maximum value Tmax of the steering torque T, the maximum value Gmax of the lateral acceleration G, the minimum steering torque To, the minimum sensed lateral acceleration Go, the Weber ratio Kt regarding the steering torque T, and the lateral If the Weber ratio Ka relating to acceleration is determined by experiments and systems, the coefficients K1, K2, and C in the equations 1 to 16 can be determined in advance by calculation. Accordingly, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction force torques Tzf and Tzr, the steering torques Tdf and Tdr that match the driver's perceptual characteristics using the equations 1-16. And the expected lateral acceleration Gdf, Gdr can be calculated.

  Returning to the description of FIG. 2 again, the expected lateral accelerations Gdf and Gdr calculated by the torque-lateral acceleration conversion unit 52 are supplied to the turning angle conversion unit 53. In addition, in the following description, the turning angle conversion unit 53 performs the calculation described later in the same manner regardless of the expected lateral acceleration Gdf, Gdr supplied from the torque-lateral acceleration conversion unit 52. The estimated lateral acceleration Gdf and Gdr are collectively described as the estimated lateral acceleration Gd. The turning angle conversion unit 53 calculates a target turning angle δd as a first turning angle of the left and right front wheels FW1 and FW2 necessary for generating the expected lateral acceleration Gd, and a compensated target turning angle δdh described later. Is calculated. And the turning angle conversion part 53 has a table which shows the change characteristic of the target turning angle (delta) d with respect to estimated lateral acceleration Gd which changes according to the vehicle speed V, as shown in FIG.

  This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the lateral acceleration G of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 53 refers to this table and calculates a target turning angle δd corresponding to the input expected lateral acceleration Gd and the detected vehicle speed V input from the vehicle speed sensor 33. The lateral acceleration G (expected lateral acceleration Gd) and the target turning angle δd stored in the table are both positive, but the expected lateral acceleration Gd supplied from the torque-lateral acceleration converting unit 52 is negative. If so, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the lateral acceleration G as shown in the following equation 27, it can be calculated by executing the calculation of the following equation 27 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · Gd / V ² Equation 27
However, L in the formula 27 is a predetermined value indicating the wheelbase length, and A is a predetermined value.

  Thus, by calculating the target turning angle δd so as to generate the expected lateral acceleration Gd based on the reaction force torque Tz (steering torque Td) perceived by the driver via the steering handle 11, the driving is calculated. The person can operate the steering wheel 11 while perceiving the expected lateral acceleration Gd expected by the person. For this reason, since the vehicle can be driven in a state adapted to the driver's steering sensation, the driving of the vehicle equipped with the steering-by-wire type steering device is simplified.

  By the way, for example, when the vehicle is traveling at a low speed, such as a low-speed traveling at the time of entering the garage, the driver may not perceive the expected lateral acceleration Gd expected by the turning operation of the steering handle 11. Thus, when the vehicle is traveling (moving) at a low speed, the driver simply turns the vehicle based on the rotation stroke of the steering handle 11, that is, the steering angle θ. In this turning, the actual turning angle δ can be increased with respect to the steering angle θ, for example, by making the actual turning angle δ proportional to the steering angle θ of the steering handle 11. It can be in a state suitable for human steering feeling.

  In other words, when the vehicle is traveling (moving) at a low speed, as described above, the expected lateral acceleration Gd based on the steering torque Td (reaction torque Tz) that changes exponentially with respect to the steering angle θ. When the target turning angle δd is determined based on the determined expected lateral acceleration Gd, the driver must move the steering wheel 11 to a larger steering angle θ in the desired direction. You may not be able to turn, and you may feel uncomfortable. On the other hand, there is a high possibility that the driver feels a sense of incongruity when he / she changes to a vehicle equipped with the steering-by-wire steering device described above. It is thought that it will be gradually resolved.

For this reason, the present inventors can obtain a more appropriate actual turning angle δ when the vehicle is traveling (moving) at a low speed or according to how the driver learns the steering characteristics of the steering device. In addition, a function for calculating the compensated target turning angle δdh by compensating the target turning angle δd calculated by the above equation 27 (hereinafter, this function is referred to as a turning angle compensation function) is introduced. Hereinafter, the turning angle compensation function will be described in detail. This turning angle compensation function calculates a compensation target turning angle δdh based on the magnitude of the vehicle speed V of the vehicle and how the driver acquires steering characteristics, and is expressed by the following equation (28).
δdh = KRt10 ・ (KRt00 ・ δd + KRt01 ・ (δl / θmax) ・ θ) + KRt11 ・ ((δl / θmax) ・ θ)
However, KRt00, KRt01, KRt10 and KRt11 are predetermined correction coefficients. The relationship shown in the following equation 29 is established between the correction coefficient KRt00 and the correction coefficient KRt01, and the relationship shown in the following equation 30 is established between the correction coefficient KRt10 and the correction coefficient KRt11.
KRt00 + KRt01 = 1 ... Formula 29
KRt10 + KRt11 = 1 ... Equation 30

  Here, in particular, with regard to the correction coefficient KRt01 and the correction coefficient KRt11, the correction coefficient KRt01 is a coefficient for correcting the vehicle speed characteristics, and the correction coefficient KRt11 is a coefficient for correcting the driver's steering characteristic acquisition level, respectively. It has the characteristics shown in (a) and (b). Specifically, as shown in FIG. 6A, the correction coefficient KRt01 has a characteristic that changes according to the vehicle speed V detected by the vehicle speed sensor 33, and the value is less than a predetermined vehicle speed. The correction coefficient is “1”, and the value changes to “0” at a predetermined vehicle speed or higher. On the other hand, as shown in FIG. 6B, the correction coefficient KRt11 is a correction coefficient that changes with a specification that uniformly decreases from a value “1” to a value “0” according to a predetermined set value. . Here, as the predetermined set value, for example, a travel distance when an ignition switch (not shown) is turned on can be adopted, and the driver becomes accustomed to the steering characteristics of the steering device as the travel distance increases. That is, it can be regarded that the steering characteristic is acquired. In this case, the correction coefficient KRt11 uniformly decreases to the value “0” as the travel distance increases.

Further, δl in the equation 28 is a target turning angle of the left and right front wheels FW1 and FW2 necessary to generate the maximum lateral acceleration Gdμ that can be taken with the friction coefficient μ of the road surface. It is calculated according to the following equation 31 which is a function.
δl = L · (1 + A · V ² ) · Gdμ / V ² Equation 31
However, also in Expression 31, L is a predetermined value indicating the wheelbase length, and A is a predetermined value, as in Expression 27. The road surface friction coefficient μ may be calculated based on a known method, for example, based on the detected slip ratio of each wheel. Further, with respect to the vehicle speed V, for example, a filter for limiting the change gradient of the vehicle speed V may be provided in order to reduce the influence of wheel slip and the disconnection of the vehicle speed sensor 33 during acceleration of the vehicle. .

  Then, the compensation target turning angle δdh is calculated as follows according to the equation 28 according to the detected vehicle speed V and the driver's steering characteristic acquisition level. That is, when the vehicle speed V is high and the set value (travel distance) is large, the correction coefficient KRt01 is set to “0” as shown in FIG. 6A, and the correction coefficient KRt11 is also shown in FIG. The value is set to “0” as shown in b). Therefore, according to the equations 29 and 30, the value of the correction coefficient KRt00 is “1”, and the value of the correction coefficient KRt10 is “1”. Thereby, the compensated target turning angle δdh based on the equation 28 becomes equal to the target turning angle δd calculated according to the equation 27, and the steering characteristic according to the above-mentioned Weber-Hefner law can be obtained. , Driving becomes easy.

  When the vehicle speed V is low and the set value (travel distance) is extremely small, the correction coefficient KRt01 is set to “1” as shown in FIG. 6A, and the correction coefficient KRt11 is also set in FIG. As shown in (b), the value is substantially “1”. Therefore, according to the equations 29 and 30, the value of the correction coefficient KRt00 is “0”, and the value of the correction coefficient KRt10 is “0”. As a result, the compensation target turning angle δdh based on the equation 28 becomes (δl / θmax) · θ as the second turning angle, which is proportional to the steering angle θ. Accordingly, even when the driver turns the vehicle at a low speed based on the rotation stroke of the steering handle 11, the actual steering angle δ with respect to the steering angle θ is large, so that the driver can steer in a state suitable for human steering feeling. The handle 11 can be rotated. Even if the driving distance is very small and the driver's steering characteristics are still insufficient, the vehicle can be driven very easily without feeling uncomfortable by making the relationship proportional to the steering angle θ. Can be swiveled.

  Further, when the vehicle speed V is large and the set value (travel distance) is extremely small, or when the vehicle speed V is small and the set value (travel distance) is large, the compensation target turning angle δdh based on the equation 28 is (δl / θmax) · θ, which is proportional to the steering angle θ. Therefore, even when the driver turns the vehicle based on the rotation stroke of the steering handle 11 at a low speed, the compensated target turning angle δdh is proportional to the steering angle θ, so that the driver is in a state suitable for a human steering sense. The steering handle 11 can be rotated. In particular, the value of the correction coefficient KRt11 is uniformly reduced from “1” to “0” according to the travel distance of the vehicle. Therefore, depending on how the driver acquires the steering characteristics, KRt11 · The ((δl / θmax) · θ) term decreases to “0”. For this reason, after fully learning the steering characteristics of the steering device, the driver perceives the steering characteristics according to Weber-Hefner's law when the vehicle speed V is high, and the steering angle when the vehicle speed V is low. A steering characteristic proportional to θ is perceived. Therefore, good steering characteristics can be obtained in any vehicle speed range, and driving can be simplified.

  Further, when the vehicle speed V is large to some extent and the set value (travel distance) is large to some extent, the correction coefficients KRt00, KRt01, KRt10, and KRt11 have values of “1” to “0” (“0” to “1”, respectively). )). Thereby, the compensated target turning angle δdh calculated according to the equation 28 is set to a value larger than the target turning angle δd calculated according to the equation 27. Therefore, the driver can obtain the optimum steering characteristics according to the vehicle speed V and the learning characteristics of the steering characteristics, and can simplify the driving.

The compensation target turning angle δdh calculated as described above is supplied to the turning angle correction unit 61 of the turning control unit 60. The turning angle correction unit 61 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation 32. The compensation target turning angle δdh input after execution is corrected, and the corrected target turning angle δda is calculated.
δda = δdh + K3 · (Gd−G) Equation 32
However, the coefficient K3 is a positive constant determined in advance, and when the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K3 is corrected so that the absolute value of the corrected target turning angle Δda becomes larger. When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd are more accurately ensured.

  The calculated corrected target turning angle δda is supplied to the drive control unit 62. The drive control unit 62 inputs the actual turning angle δ detected by the turning angle sensor 32, and electrically drives the turning actuator 21 so that the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda. Feedback control of motor rotation. The drive control unit 62 also inputs a drive current that flows from the drive circuit 37 to the electric motor, and feedback-controls the drive circuit 37 so that a drive current having a magnitude corresponding to the steering torque appropriately flows to the electric motor. To do. By the drive control of the electric motor in the steering actuator 21, the rotation of the electric motor is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the pinion gear 23. Then, due to the displacement of the rack bar 24 in the axial direction, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda.

  As can be understood from the above description of the operation, according to the first embodiment, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is obtained by the steering torque Tdf or the hysteresis term Mh1 by the displacement-torque converter 51. It is converted into the applied steering torque Tdr. The converted steering torques Tdf and Tdr are converted by the torque-lateral acceleration conversion unit 52 into the expected lateral acceleration Gdr to which the expected lateral acceleration Gdf or the hysteresis term Mh2 is given. Then, the turning angle conversion unit 53 appropriately changes the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11 as ratios according to the vehicle speed V and the set value (travel distance), and the expected lateral accelerations Gdf, Gdr A compensation target turning angle Δdh consisting of (Δl / θmax) · θ proportional to the steering angle θ required for generation and the steering angle θ is calculated. The calculated compensation target turning angle δdh is corrected to the corrected target turning angle δda by the turning angle correction unit 61, and the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda by the drive control unit 62. The

  Then, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is large or the mileage is large and the driver has sufficiently mastered the steering characteristics of the steering device, for example, target steering By increasing the ratio of the angle δd, that is, by setting the correction coefficients KRt00 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on the target turning angle δd. Therefore, when the vehicle turns with the corrected target turning angle δda, the driver is given the expected lateral accelerations Gdf and Gdr as “physical quantities of the given stimulus” according to the Weber-Hefner's law. . The expected lateral accelerations Gdf and Gdr are exponential functions with respect to the steering angle θ by transforming Expression 12 into Expression 16 with respect to the steering torque Td (reaction torque Tz) applied to the steering wheel 11. Therefore, the driver can operate the steering wheel 11 while perceiving a motion state amount that matches human perceptual characteristics. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is low or the mileage is short and the driver has not sufficiently mastered the steering characteristics of the steering device, for example, ( By increasing the ratio of δl / θmax) · θ, that is, by setting the correction coefficients KRt01 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on (δl / θmax) · θ. Therefore, when the vehicle turns with the corrected target turning angle δda, the driver can turn the vehicle at a turning angle proportional to the steering angle θ with respect to the steering handle 11, and thus the steering characteristics are not sufficiently learned. Even so, the vehicle can be easily turned based on experience with a conventional mechanically coupled steering device.

  In the first embodiment, the steering that compensates the target turning angle δd in order to eliminate the uncomfortable feeling that the driver learns when the vehicle travels (moves) at low speed or when the steering characteristic is not sufficiently learned. An angle compensation function was introduced, and the compensation target turning angle δdh having a proportional relationship with the steering angle θ input by the driver was calculated. As a result, the vehicle turns according to the linear steering characteristics with respect to the rotation stroke of the steering handle 11 of the driver, so that even if the vehicle moves at a low speed or the steering characteristics are not sufficiently learned, I didn't feel uncomfortable.

  By the way, when the driver needs a large actual turning angle, the driver may feel a sense of discomfort as described above due to a time delay until the actual turning angle δ with respect to the steering angle θ of the steering wheel 11 is generated. There is. In other words, the target turning angle δd in the first embodiment described above is the expected lateral acceleration Gd (exponential function) that changes exponentially with respect to the steering torque Td (that is, the steering torque Tdf, Tdr) according to the equation 27. That is, it is calculated based on the expected lateral acceleration (Gdf, Gdr). Further, the steering torque Td (steering torques Tdf, Tdr) is calculated so as to change exponentially with respect to the steering angle θ as the operation input value by the driver according to the expressions 7 and 9 above the predetermined value Tg. Is done. For this reason, when the driver needs a large actual turning angle, the steering handle 11 must be rotated more than the conventional mechanically connected steering device. Depending on the driver, the driver may feel uncomfortable. Therefore, if the steering torque Td (steering torque Tdf, Tdr) is increased with respect to the steering angle θ as an operation input value by the driver, particularly when driving at low speed (moving), the driver needs The time delay until the actual turning angle δ is generated can be reduced. Hereinafter, a first modification of the first embodiment will be described in detail.

In this first modification, the steering torque Td (steering torque Tdf, Tdr) as the first operating force supplied from the displacement-torque converter 51 to the torque-lateral acceleration converter 52 is largely compensated to compensate the steering torque. A function for calculating Tdh (compensated steering torque Tdfh, Tdrh) (hereinafter referred to as a torque compensation function) is introduced. Hereinafter, the torque compensation function will be described in detail. This torque compensation function calculates a compensation steering torque Tdh based on the magnitude of the vehicle speed V of the vehicle and the change characteristic of the steering angle θ, and is expressed by the following equation 33 at the time of the cutting operation, and at the time of the return operation. It is represented by the following formula 34.
Tdfh = KRs10 • (KRs00 • Tdf + KRs01 • (Tmax / θmax) • θ) + KRs11 • (Tmax / θmax) • θ
Tdrh = KRs10 • (KRs00 • Tdr + KRs01 • (Tmax / θmax) • θ) + KRs11 • (Tmax / θmax) • θ
However, KRs00, KRs01, KRs10 and KRs11 are predetermined correction factors. The relationship shown in the following equation 35 is established between the correction coefficient KRs00 and the correction coefficient KRs01, and the relationship shown in the following equation 36 is established between the correction coefficient KRs10 and the correction coefficient KRs11.
KRs00 + KRs01 = 1 ... Formula 35
KRs10 + KRs11 = 1 ... Formula 36

  Here, in particular, regarding the correction coefficient KRs01 and the correction coefficient KRs11, the correction coefficient KRs01 is a coefficient for correcting the steering delay characteristic based on the vehicle speed characteristic, and the correction coefficient KRs11 is a coefficient for correcting the change characteristic of the steering angle θ. These have the characteristics shown in FIGS. 7A and 7B, respectively. More specifically, as shown in FIG. 7A, the correction coefficient KRs01 has a characteristic that changes according to the vehicle speed V detected by the vehicle speed sensor 33, and the value is less than a predetermined vehicle speed. A correction coefficient that is “1” and that changes to a predetermined value at a predetermined vehicle speed or higher. On the other hand, as shown in FIG. 7B, the correction coefficient KRs11 is “1” when the steering angle θ input by the driver is less than the predetermined steering angle θz, and is greater than or equal to the predetermined steering angle θz. A correction coefficient whose value changes to a predetermined value. The predetermined value may be set as a numerical value between “0” and “1”. Here, the reason why the correction coefficient KRs11 is set to “1” when the angle is less than the predetermined steering angle θz is that the steering torques Tdf and Tdr change in a linear function according to the formulas 6 and 8 below the predetermined steering angle θz. It is.

  The compensated steering torque Tdh is calculated as follows according to the equations 33 and 34 in accordance with the detected vehicle speed V and the steering angle θ. That is, when the vehicle speed V is high and the steering angle θ is equal to or greater than the steering angle θz, the correction coefficient KRs01 is set to a predetermined value as shown in FIG. As shown in (b), the value is set to a predetermined value. For this reason, the correction coefficient KRs00 and the correction coefficient KRs10 are determined according to the expressions 35 and 36. Thereby, the compensation steering torque Tdh (compensation steering torque Tdfh, Tdrh) supplied from the displacement-torque conversion unit 51 to the torque-lateral acceleration conversion unit 52 is the steering torque Td input by the driver via the steering handle 11. Since the calculation is compensated to be larger than (steering torque Tdf, Tdr), the time delay until the actual turning angle δ required by the driver is generated can be reduced.

  When the vehicle speed V is small and the steering angle θ is less than the steering angle θz, the correction coefficient KRs01 is set to “1” as shown in FIG. 7A, and the correction coefficient KRs11 is also shown in the figure. The value is set to “1” as shown in FIG. Therefore, the value of the correction coefficient KRs00 becomes “0” and the value of the correction coefficient KRs10 also becomes “0” in accordance with the above equations 35 and 36. As a result, the compensated steering torque Tdh (compensated steering torque Tdfh, Tdrh) based on the equations 33 and 34 is (Tmax / θmax) · θ as the second operating force, and is proportional to the steering angle θ. . By obtaining this proportional relationship, for example, when the steering handle 11 is rotated to the maximum steering angle θmax, it is possible to shorten the time until the maximum steering torque Tmax is generated. Therefore, the driver can linearly change the actual turning angle δ with respect to the steering angle θ of the steering handle 11, and can obtain a steering characteristic that matches human perception characteristics. Thereby, the driver can turn the vehicle very easily without feeling uncomfortable.

  The compensated steering torque Tdh (compensated steering torque Tdfh, Tdrh) calculated as described above is supplied to the torque-lateral acceleration converter 52. The torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd (expected lateral acceleration Gdf, Gdr) according to the above equations 11 to 15 using the supplied compensation steering torque Tdh. Even in this case, the expected lateral acceleration Gd (expected lateral acceleration Gdf, Gdr) can be calculated using the conversion table having the characteristics shown in FIG. Then, the calculated expected lateral acceleration Gd is supplied to the turning angle conversion unit 53, the target turning angle δd is calculated according to the equation 27, and the calculated target turning angle δd is calculated by the turning control unit 60. The correction target turning angle δda is calculated by being corrected by the turning angle correction unit 61. Therefore, since the expected lateral acceleration Gd (expected lateral acceleration Gdf, Gdr) is calculated based on the compensated steering torque Tdh, the steering delay is eliminated, and the uncomfortable feeling felt by the driver as in the first embodiment is eliminated. Can do.

  Next, a second modification of the first embodiment in which the steering torque T is used as the operation input value of the steering handle 11 will be described. In the second modified example, as indicated by a broken line in FIG. 1, the steering torque assembled to the steering input shaft 12 and input to the steering handle 11 is detected, and the detected steering torque is used as the steering torque T. A steering torque sensor 38 for detection is provided. Other configurations are the same as those in the first embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the first embodiment.

  In the case of this second modification, in the functional block diagram of FIG. 2 representing the computer program, the displacement-torque conversion unit 51 is not provided, and the torque-lateral acceleration conversion unit 52 is used in the first embodiment. The estimated lateral accelerations Gdf and Gdr are calculated using the steering torque T detected by the steering torque sensor 38 instead of the steering torques Tdf and Tdr calculated by the displacement-torque converter 51 in FIG. That is, the steering torque T output from the steering torque sensor 38 is calculated and output in the same manner as in the equations 6 to 10 according to the cutting operation or the return operation with respect to the input steering torque. The calculation similar to ˜16 is executed to determine the expected lateral accelerations Gdf and Gdr. In this case as well, the expected lateral accelerations Gdf and Gdr may be calculated using a table representing the characteristics shown in FIG. The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment.

  According to the second modification, the steering torque T as the driver's operation input value for the steering handle 11 is changed to the expected lateral acceleration Gdr to which the expected lateral acceleration Gdf or the hysteresis term Mh2 is given by the torque-lateral acceleration conversion unit 52. The left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δda necessary for generating the expected lateral accelerations Gdf and Gdr by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62. The Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering wheel 11, and the expected lateral accelerations Gdf and Gdr with respect to the steering torque T are exponential functions (formula 12 is transformed into formula 16). Therefore, the driver changes the expression 14 in an exponential manner in the same manner, so that the driver feels the reaction force according to Weber-Hefner's law, and the steering wheel 11 according to the human perceptual characteristic. Can be rotated. Therefore, also in this modified example, as in the case of the first embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the lateral acceleration according to the Weber-Hefner's law. Since the vehicle can be turned, the same effect as in the case of the first embodiment is expected.

  Furthermore, the vehicle steering control according to the first embodiment and the vehicle steering control according to the second modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 38 are provided, and the estimated lateral acceleration Gd is calculated using the steering torque Td calculated by the displacement-torque conversion unit 51 as in the first embodiment. It is also possible to switch between the case where the expected lateral acceleration Gd is calculated using the steering torque T output by the steering torque sensor 38 and to make it usable. In this case, the switching may be performed automatically according to the driver's intention or according to the motion state of the vehicle.

In the first embodiment, the turning angle correction unit 61 corrects the target turning angle δd according to the difference Gd−G between the expected lateral acceleration Gd and the actual lateral acceleration G. However, instead or in addition, the turning angle correction unit 61 corrects the target turning angle δd according to the difference γd−γ between the expected yaw rate γd corresponding to the expected lateral acceleration Gd and the actual yaw rate γ. It may be. In this case, the expected yaw rate γd is calculated by the calculation of Expression 37 below using the expected lateral acceleration Gd and the vehicle speed V.
γd = Gd / V Equation 37

Then, the corrected target turning angle δda is calculated based on the following equation 38 using the calculated expected yaw rate γd and the actual yaw rate γ detected by the yaw rate sensor 39 as indicated by a broken line in FIG. That's fine.
δda = δd + K4 · (γd−γ) Equation 38
However, the coefficient K4 is a predetermined positive constant, and when the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K4 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd are more accurately ensured.

b. Second Embodiment In the first embodiment, the reaction force torques Tzf and Tzr are calculated according to the equations 1 to 5, and the steering torques Tdf and Tdr are calculated according to the equations 6 to 10. That is, when the steering angle θ of the steering wheel 11 is less than the predetermined steering angle θz, the reaction force torques Tzf, Tzr and the steering torques Tdf, Tdr are linear function equations that pass through the origin “0” (the aforementioned equations 1, 3, 6, and 8). ), And in accordance with the exponential function formula (the above formulas 2, 4, 7 and 9) based on Weber-Hefner's law at a predetermined steering angle θz or more. In particular, by calculating the reaction force torques Tzf, Tzr and the steering torques Tdf, Tdr in the vicinity of the neutral position according to a linear function equation, vibration in the turning direction of the steering handle 11 can be effectively prevented. In other words, the steering handle 11 can be maintained at the neutral position by the reaction force torques Tzf and Tzr and the steering torques Tdf and Tdr determined by the magnitudes of the gradients a1 and a2 of the linear function equation, and vibration in the rotational direction can be generated. It can be effectively prevented. Furthermore, the linear function formula and the exponential function formula were implemented so as to be continuously connected at a predetermined steering angle θz. As a result, the reaction force torques Tzf and Tzr perceived by the driver and the steering torques Tdf and Tdr applied by the driver to the steering wheel 11 are changed from a linear function change to an exponential function change or an exponential function change. Even when switching to a linear function change, the driver does not feel discomfort.

  By the way, the exponential function formula based on the Weber-Hefner law in the first embodiment is an exponential function formula determined depending on the constant K1 calculated by the formula 21 as described above, and the identification number K1. Is determined based on a vehicle steering system (for example, a maximum steering angle θmax). Therefore, depending on the steering system of the vehicle, it is possible to increase the values of the reaction torques Tzf and Tzr and the steering torques Tdf and Tdr calculated by the exponential function formula. When the function formulas are continuously connected at a predetermined steering angle θz, the slopes (ie, the slopes a1 and a2) of the connected linear function formulas become large. For this reason, when the driver starts the turning operation from the neutral position of the steering handle 11, the driver perceives larger reaction force torques Tzf and Tzr, in other words, applies larger steering torques Tdf and Tdr to the steering handle 11. It is necessary to rotate while applying.

  Further, since the larger reaction force torques Tzf and Tzr are applied to the steering handle 11, for example, when the steering handle 11 is turned by a slight amount, the steering wheel 11 is returned to the neutral position direction by the larger reaction force torque. Vibration in the rotation direction is likely to occur. This is particularly noticeable when the vehicle is traveling at a low speed and the driver rotates the steering handle 11 greatly. Therefore, a second embodiment that facilitates the turning operation of the steering handle 11 from the neutral position and can prevent vibration in the turning direction of the steering handle 11 near the neutral position will be described in detail below. In the second embodiment, the configuration is the same as that of the first embodiment, and only the calculation formulas of the reaction force torques Tzf and Tzr and the steering torques Tdf and Tdr by the displacement-torque converters 41 and 51 are different. . Therefore, the detailed description regarding a structure is abbreviate | omitted.

Also in the second embodiment, when the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ that is the rotation angle of the steering handle 11, and the detected steering angle θ. Are output to the reaction force control unit 40 and the sensory adaptation control unit 50, respectively. Then, the displacement-torque conversion unit 41 of the reaction force control unit 40 calculates the reaction force torque Tzf according to the following equation 39 if the steering handle 11 is turned by the driver, and if the return operation is performed, the following equation 40 is obtained. The reaction torque Tzr is calculated according to
Tzf ＝ KRs0 ・ To ・ exp (K1 ・ θ) ＋ KRs1 ・ (KRm0 ・ To ・ (exp (K1 ・ θ) −1) + KRm1 ・ (Tmax / θmax) ・ θ)
Tzf = KRs0 • (To • exp (K1 • θ) −Mh1) + KRs1 • (KRm0 • (To • (exp (K1 • θ) −1) −Mh1) + KRm1 • (Tmax / θmax) • θ)
However, KRs0, KRs1, KRm0, and KRm1 in the equations 39 and 40 are predetermined coefficients (weighting factors), and Mh1 in the equation 40 is a hysteresis for configuring the hysteresis characteristics as in the first embodiment. Term.

Here, the relationship shown in the following equation 41 is established between the coefficient KRs0 and the coefficient KRs1, and the relationship shown in the following equation 42 is established between the coefficient KRm0 and the coefficient KRm1.
KRs0 + KRs1 = 1 ... Formula 41
KRm0 + KRm1 = 1 ... Formula 42
The coefficient KRs0 and the coefficient KRm0 have change characteristics as shown in FIGS. 8A and 8B according to the vehicle speed V detected by the vehicle speed sensor 33. Specifically, as shown in FIG. 8A, the coefficient KRs0 is “0” when the detected vehicle speed V is less than the predetermined vehicle speed V1, and is equal to or higher than the predetermined vehicle speed V1 and less than the predetermined vehicle speed V2. Is a coefficient (weighting coefficient) at which the value changes to “1” and the value is set to “1” at a predetermined vehicle speed V2 or higher. On the other hand, as shown in FIG. 8B, the coefficient KRm0 is “1” when the detected vehicle speed V is less than the predetermined vehicle speed V1, and the value is greater than or equal to the predetermined vehicle speed V1 and less than the predetermined vehicle speed V2. This is a coefficient (weighting coefficient) that changes to “0” and that is set to “0” when the vehicle speed is V2 or higher.

Thus, when the coefficient KRs0 and the coefficient KRm0 change according to the detected vehicle speed V, the reaction force torque Tzf or the reaction force torque Tzr calculated according to the equation 39 or the equation 40 is as follows. That is, if the detected vehicle speed V is less than the predetermined vehicle speed V1, the coefficient KRs0 is set to “0”, and the coefficient KRs1 is set to “1” according to the equation 41. On the other hand, if the detected vehicle speed V is less than the predetermined vehicle speed V1, the coefficient KRm0 is set to “1”, and the coefficient KRm1 is set to “0” according to the equation 42. As a result, when the detected vehicle speed V is less than the predetermined vehicle speed V1 (during low speed driving), the equations 39 and 40 are expressed by the following equations 43 and 44, respectively, and the reaction force torques Tzf and Tzr according to the equations 43 and 44 Is calculated.
Tzf = To · (exp (K1 · θ) −1) Equation 43
Tzr = To · (exp (K1 · θ) −1) −Mh1 Equation 44
The reaction force torques Tzf and Tzr calculated according to the equations 43 and 44 are calculated to be “0” if the steering angle θ of the steering wheel 11 is “0”, that is, the neutral position. Further, when the steering handle 11 is turned from the neutral position or returned to the neutral position, the reaction force torques Tzf and Tzr applied in the vicinity of the neutral position change exponentially and gradually. The reaction torques Tzf and Tzr imparted to 11 are reduced.

  For this reason, in addition to the reaction force torques Tzf and Tzr being not applied at the neutral position of the steering wheel 11, the amount of change in the reaction force torques Tzf and Tzr near the neutral position (the slope of the linear function equation in the first embodiment). The vibration in the turning direction of the steering handle 11 can be prevented by reducing (equivalently a1 and a2). Further, when the cutting operation is started from the neutral position, the reaction force torque Tzf perceived by the driver is reduced, so that the steering torque applied to the steering handle 11 by the driver is also reduced. Therefore, even when the constant K1 is set to be large according to the vehicle steering system, the driver can turn the steering handle 11 very easily.

If the detected vehicle speed V is equal to or higher than the predetermined vehicle speed V2, the coefficient KRs0 is set to “1”, and the coefficient KRs1 is set to “0” according to the equation 41. As a result, when the detected vehicle speed V is equal to or higher than the predetermined vehicle speed V2 (during high-speed driving), the equations 39 and 40 are expressed by the following equations 45 and 46, respectively, and the reaction force torques Tzf and Tzr Is calculated.
Tzf = To · exp (K1 · θ)… Formula 45
Tzr = To · (exp (K1 · θ) −Mh1) Equation 46
The reaction torques Tzf and Tzr calculated according to the equations 45 and 46 are calculated based on Weber-Hefner's law, as in the first embodiment. As a result, during high-speed traveling, the driver can turn the steering handle 11 in a state that matches human perceptual characteristics. Further, the reaction force torques Tzf and Tzr calculated according to the equations 45 and 46 during high speed traveling are calculated as To if the steering wheel 11 is in the neutral position, that is, the steering angle θ is “0”. In this way, by applying the reaction force torque To to the steering handle 11 in the neutral position, it is possible to satisfactorily ensure the straight running stability of the vehicle during high speed traveling.

  That is, when the reaction force torque To is applied at the neutral position, the steering handle 11 is returned to the neutral position direction by the applied reaction force torque To when the steering handle 11 is slightly rotated in the left-right direction from the neutral position. It is. Thereby, for example, when the steering handle 11 is turned in the left-right direction which is not intended by the driver, the steering handle 11 is automatically returned to the neutral position. Further, the steering handle 11 in the neutral position is maintained in the state by the reaction force torque To. Therefore, it is possible to satisfactorily ensure the straight running stability of the vehicle when traveling at high speed.

  When the detected vehicle speed V is equal to or higher than the predetermined vehicle speed V1 and lower than the predetermined vehicle speed V2, the coefficients KRs0, KRs1, KRm0 and KRm1 are continuously between “0” to “1” (“1” to “0”). Changes. Thus, when the detected vehicle speed V is equal to or higher than the predetermined vehicle speed V1 and lower than the predetermined vehicle speed V2 (during medium speed traveling), the reaction force torques Tzf and Tzr are calculated according to the above formulas 39 and 40. In this way, the coefficients KRs0, KRs1, KRm0 and KRm1 of the equations 39 and 40 change continuously, in other words, the weight of each term of the equations 39 and 40 changes continuously, so that the driver feels uncomfortable. The steering handle 11 can be turned without having to remember. This will be specifically described below.

  First, changes in reaction force torques Tzf and Tzr accompanying changes in coefficient KRm0 and coefficient KRm1 will be described. When the detected vehicle speed V increases to a predetermined vehicle speed V1 or more, the coefficient KRm0 decreases from “1” to “0” as shown in FIG. It increases from “0” to “1”. Thus, as the detected vehicle speed V increases, the reaction force torques Tzf and Tzr are expressed as To · (exp (K1 · θ) -1) or To · ((exp (K1 · θ) − 1) The weight of −Mh1) is continuously reduced, and the weight of (Tmax / θmax) · θ is continuously increased.

  Next, changes in reaction torques Tzf and Tzr accompanying changes in coefficient KRs0 and coefficient KRs1 will be described. When the detected vehicle speed V increases to a predetermined vehicle speed V1 or more, as shown in FIG. 8A, the value of the coefficient KRs0 increases from “0” to “1”, and the coefficient KRs1 The value decreases from “1” to “0”. Thereby, as the detected vehicle speed V increases, KRm0 · To · (exp (K1 · θ) −1) + KRm1 · (Tmax / θmax) · θ in the above equations 39 and 40 with respect to the reaction force torques Tzf and Tzr. Or the weight of KRm0 · (To · (exp (K1 · θ) -1) -Mh1) + KRm1 · (Tmax / θmax) · θ decreases continuously and To · exp (K1 · θ) or To · exp The weight is calculated by increasing the weight of (K1 · θ) −Mh1 continuously.

  As described above, the coefficients KRs0, KRs1, KRm0, and KRm1 continuously change during medium speed traveling (specifically, the coefficients KRs0 and KRm1 increase), and thus are calculated according to the above equations 43 and 44 during low speed traveling. The reaction force torques Tzf, Tzr and the reaction force torques Tzf, Tzr calculated according to the above formulas 45, 46 during high speed running are continuously changed. Therefore, the weights of the terms of the equations 39 and 40, that is, the coefficients KRs0, KRs1, KRm0, and KRm1 continuously change according to the detected vehicle speed V, and the amount of turning operation of the steering wheel 11 by the driver, that is, the steering angle θ. By calculating the reaction force torques Tzf and Tzr based on the change in the driving force, the driver can smoothly rotate the steering handle 11 without feeling uncomfortable in the rotating operation of the steering handle 11 when traveling at a medium speed.

  Also in the second embodiment, the calculated reaction force torque Tzf or reaction force torque Tzr is supplied to the drive control unit 42 as in the first embodiment. And the drive control part 42 inputs the drive current which flows into the electric motor in the reaction force actuator 13 from the drive circuit 36, and the drive current corresponding to reaction force torque Tzf or reaction force torque Tzr flows into the same electric motor. The drive circuit 36 is feedback controlled. Accordingly, the driver can perceive the reaction torques Tzf and Tzr as described above via the steering handle 11.

On the other hand, when the steering angle θ input to the sensory adaptation control unit 50 is turned by the driver, the displacement-torque conversion unit 51 calculates the steering torque Tdf according to the following equation 47 similar to the equation 39. Further, when the driver is performing a return operation, the displacement-torque converter 51 calculates the steering torque Tdr according to the following equation 48 similar to the equation 40.
Tdf = KRs0 · To · exp (K1 · θ) + KRs1 · (KRm0 · To · (exp (K1 · θ) -1) + KRm1 · (Tmax / θmax) · θ)
Tdf ＝ KRs0 ・ (To ・ exp (K1 ・ θ) −Mh1) + KRs1 ・ (KRm0 ・ (To ・ (exp (K1 ・ θ) −1) −Mh1) + KRm1 ・ (Tmax / θmax) ・ θ)
However, KRs0, KRs1, KRm0 and KRm1 in the equations 47 and 48 are also predetermined coefficients (weighting factors) that change according to the detected vehicle speed V similar to the equations 39 and 40, and Mh1 in the equation 48 is It is a hysteresis term for constituting a hysteresis characteristic as in the first embodiment.

  Also in the calculation of the steering torques Tdf and Tdr, the coefficients KRs0, KRs1, KRm0, and KRm1 are calculated according to the equations 41 and 42 as in the calculation of the reaction force torques Tzf and Tzr described above. As a result, the steering torques Tdf and Tdr are calculated according to an exponential function (corresponding to the equations 43 and 44) passing through the origin “0” during low-speed traveling, and an exponential function based on the Weber-Hefner law (described above) during high-speed traveling. (Corresponding to equations 45 and 46). When the vehicle travels at medium speed, the coefficients KRs0, KRs1, KRm0, and KRm1 continuously change (specifically, the coefficients KRs0, KRm1 increase). 48, the steering torques Tdf and Tdr calculated during low speed running and the steering torques Tdf and Tdr calculated during high speed running are continuously changed.

The steering torques Tdf and Tdr calculated in this way are supplied to the torque-lateral acceleration conversion unit 52 as in the first embodiment. Then, the torque-lateral acceleration conversion unit 52 calculates expected lateral accelerations Gdf, Gdr according to the following formulas 49, 50 based on the supplied steering torques Tdf, Tdr.
Gdf = C ・ Tdf ^K2 ... Formula 49
Gdr = C ・ (Tdr−Mh2) ^K2 (Formula 50)
However, the formulas 49 and 50 are configured in the same manner as the formulas 12 and 14 in the first embodiment, and Mh2 in the formula 50 is the same between the cutting operation and the return operation as in the first embodiment. This is a hysteresis term for configuring the hysteresis characteristic. Then, the torque-lateral acceleration conversion unit 52 calculates the expected lateral accelerations Gdf and Gdr according to the formulas 49 and 50, and supplies them to the turning angle conversion unit 53. As described above, when the expected lateral accelerations Gdf and Gdr are supplied from the torque-lateral acceleration conversion unit 52, the turning angle conversion unit 53 calculates the compensated target turning angle δdh as in the first embodiment. .

  As can be understood from the above description, according to the second embodiment, when the vehicle speed is less than the predetermined vehicle speed V1, the reaction force in the vicinity of the neutral position of the steering wheel 11 according to the exponential function shown in the equations 43 and 44. By reducing the amount of change of the torque Tzf, Tzr (steering torque Tdf, Tdr) with respect to the steering angle θ, it is possible to prevent the steering handle 11 from vibrating in the rotational direction. That is, the steering handle 11 can be smoothly returned to the neutral position by reducing the amount of change in the reaction torque Tzf, Tzr (steering torque Tdf, Tdr) with respect to the steering angle θ in the vicinity of the neutral position. 11 can be effectively prevented from vibrating in the rotating direction.

c. Third Embodiment In the first modification of the first embodiment, the turning angle conversion unit 53 calculates the compensated target turning angle δdh by compensating the target turning angle δd with the turning angle compensation function. Carried out. As a result, when the vehicle speed V is small, the compensated target turning angle δdh is proportional to the steering angle θ, and even if the driver is still insufficient in learning the steering characteristics, the driver feels uncomfortable. The vehicle can be turned easily.

  By the way, in the first embodiment, the compensation target turning angle δdh calculated when the vehicle speed V is low is a linear function equation represented by (δl / θmax) · θ, and is determined by the steering system of the vehicle. It depends on the maximum value θmax of the steering angle θ. Therefore, in the vehicle steering system in which the maximum value θmax is set small, the slope of the linear function equation, that is, δl / θmax increases, and as a result, the amount of change in the compensation target turning angle δdh may become steep. . Further, when the slope of the linear function formula increases, for example, when the left and right front wheels FW1 and FW2 vibrate in the left and right direction when the left and right front wheels FW1 and FW2 are returned in the straight travel position direction according to the driver's return operation. As a result, the straight running stability near the straight running position may deteriorate. Accordingly, a third embodiment in which the amount of change in the compensation target turning angle δdh near the straight traveling position is moderately described below. The configuration of the third embodiment is the same as that of the first embodiment, and only the calculation formula of the compensation target turning angle δdh by the turning angle conversion unit 53 is different. Therefore, detailed description regarding the configuration is omitted.

In the third embodiment, the expected lateral accelerations Gdf and Gdr calculated from the torque-lateral acceleration conversion unit 52 in the same manner as the first modification of the first embodiment are supplied to the turning angle conversion unit 53. The turning angle conversion unit 53 calculates the target turning angle δd according to the equation 27 based on the supplied expected lateral accelerations Gdf and Gdr. Then, the turning angle conversion unit 53 compensates the target turning angle δd calculated according to the following formula 51, and calculates the compensated target turning angle δdh.
δdh = KRt0 ・ δd + KRt1 ・ (KRm00 ・ (exp (KRM ・ θ) −1) + KRm01 ・ (δmax / θmax) ・ θ)
However, KRt0, KRt1, KRm00, and KRm01 are predetermined correction coefficients. The relationship shown in the following formula 52 is established between the correction coefficient KRt0 and the correction coefficient KRt1, and the relationship shown in the following formula 53 is established between the correction coefficient KRm00 and the correction coefficient KRm01.
KRt0 + KRt1 = 1 ... Formula 52
KRm00 + KRm01 = 1 ... Formula 53
Further, δmax in the formula 51 is the maximum value that the left and right front wheels FW1, FW2 can steer, and KRM is a predetermined constant.

  Here, in particular, with regard to the correction coefficient KRt0 and the correction coefficient KRm00, the correction coefficient KRt0 is a coefficient for correcting the vehicle speed characteristic, and the correction coefficient KRm00 is a coefficient for correcting the steering characteristic of the vehicle. ) And (b). More specifically, as shown in FIG. 9A, the correction coefficient KRt0 has a characteristic that changes according to the vehicle speed V detected by the vehicle speed sensor 33, and the value is less than a predetermined vehicle speed. This is a correction coefficient that is set to “0” and that changes to “1” at a predetermined vehicle speed or higher. On the other hand, the correction coefficient KRm00 has a characteristic that changes according to the steering angle θ detected by the steering angle sensor 31, as shown in FIG. 9B. That is, when the steering angle is less than the predetermined steering angle θ1, the value is “1”. When the steering angle is greater than the predetermined steering angle θ1 and less than the predetermined steering angle θ2, the value changes to “0”. This is a correction coefficient whose value is “0”.

Then, the compensation target turning angle δdh is calculated according to the equation 51 according to the detected vehicle speed V as follows. That is, when the detected vehicle speed V is less than the predetermined vehicle speed, the correction coefficient KRt0 is set to “0”, and the correction coefficient KRt1 is set to “1” according to the equation 52. As a result, when the detected vehicle speed V is less than the predetermined vehicle speed, the equation 51 is expressed by the following equation 54, and the compensated target turning angle δdh is calculated according to the equation 54.
δdh = KRm00 · (exp (KRM · θ) −1) + KRm01 · (δmax / θmax) · θ Equation 54
When the detected vehicle speed V is less than the predetermined vehicle speed and the steering angle θ of the steering wheel 11 is less than the predetermined steering angle θ1, the correction coefficient KRm00 is set to “1” and according to the above equation 53. The correction coefficient KRm01 is set to “0”. Therefore, the formula 54 is represented by the following formula 55, and the compensation target turning angle δdh is calculated according to the formula 55.
δdh = exp (KRM · θ) −1) Equation 55
The compensated target turning angle δdh calculated according to the equation 55 is calculated as “0” (straight forward position) when the steering angle θ of the steering wheel 11 is “0” (neutral position). When the steering handle 11 is turned or returned in the vicinity of the neutral position, the compensation target turning angle δdh changes gently exponentially. Therefore, the amount of change in the compensation target turning angle δdh (corresponding to the slope δl / θmax of the linear function equation in the first embodiment) near the straight position of the left and right front wheels FW1, FW2 is small (slowly). Further, it is possible to prevent left and right front-wheel FW1 and FW2 vibrations in the left-right direction in the vicinity of the rectilinear position.

When the detected vehicle speed V is less than the predetermined vehicle speed and the steering angle θ of the steering wheel 11 is equal to or larger than the predetermined steering angle θ2, the correction coefficient KRm00 is set to “0” and according to the above equation 53. The correction coefficient KRm01 is set to “1”. For this reason, the equation 54 is expressed by the following equation 56, and the compensation target turning angle δdh is calculated according to the equation 56.
δdh = (δmax / θmax) · θ Equation 56
The compensation target turning angle δdh calculated according to the equation 56 is proportional to the steering angle θ, as in the first modification of the first embodiment. By obtaining this proportional relationship, the driver can linearly change the actual turning angle δ with respect to the steering angle θ of the steering handle 11, and obtain a steering characteristic that matches human perception characteristics. it can. Therefore, the driver can turn the vehicle very easily without feeling uncomfortable.

  Further, when the detected vehicle speed V is less than the predetermined vehicle speed, when the steering angle θ of the steering wheel 11 is not less than the predetermined steering angle θ1 and less than the predetermined steering angle θ2, the correction coefficient KRm00 and the correction coefficient KRm01 are It changes continuously between “1” to “0” (“0” to “1”). For this reason, the compensation target turning angle δdh is calculated according to the equation 54. In this case, according to the change of the steering angle θ of the steering wheel 11, the compensation target turning angle δdh calculated according to the equation 55 and the compensation target turning angle δdh calculated according to the equation 56 are continuously obtained. Be changed. For this reason, the driver can turn the steering handle 11 without feeling uncomfortable with the change.

  On the other hand, when the detected vehicle speed V is equal to or higher than the predetermined vehicle speed, the correction coefficient KRt0 is set to “1”, and the correction coefficient KRt1 is set to “0” according to the above equation 52. Thus, when the detected vehicle speed V is equal to or higher than the predetermined vehicle speed, the compensated target turning angle δdh becomes equal to the target turning angle δd for generating the expected lateral accelerations Gdf and Gdr. The steering characteristics according to the above are perceived. Therefore, when driving at a high speed, the driver can easily turn the vehicle while perceiving a steering characteristic that matches the human perceptual characteristic.

  As can be understood from the above description, in the third embodiment, when the vehicle speed is less than the predetermined vehicle speed, the compensation target turning angle δdh in the vicinity of the neutral position of the steering wheel 11 is determined according to the exponential function shown in the equation 55. By reducing the amount of change with respect to the steering angle θ, it is possible to prevent the left and right front wheels FW1, FW2 from vibrating in the left-right direction. That is, by reducing the amount of change in the compensation target turning angle δdh with respect to the steering angle θ, the left and right front wheels FW1 and FW2 are smoothly and gently turned to the straight-ahead position when the steering handle is returned to the neutral position. Therefore, the left and right front wheels FW1, FW2 can be effectively prevented from vibrating in the left-right direction. In the third embodiment, the steering-by-wire type steering device in which the driver rotates the steering handle 11 according to the Weber-Hefner law has been described in detail. However, the conventional system does not depend on the Weber-Hefner law. The present invention can also be applied to a steering-by-wire steering apparatus. Even in this case, the same effect can be expected by gradually turning the turning angle of the steered wheels (corresponding to the left and right front wheels FW1 and FW2) according to the equation 78 in the vicinity of the neutral position of the steering handle.

d. Fourth Embodiment Next, a fourth embodiment of the present invention using a yaw rate instead of the lateral acceleration as the motion state quantity in the first embodiment will be described. In the fourth embodiment, as indicated by a broken line in FIG. 1, instead of the lateral acceleration sensor 34 in the first embodiment, an actual yaw rate γ that is a motion state quantity that can be perceived by the driver is detected and output. A yaw rate sensor 39 is provided.

  In the fourth embodiment, the computer program executed by the electronic control unit 35 is shown by the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment, but instead of the torque-lateral acceleration conversion unit 52 in the first embodiment, a torque-yaw rate conversion unit. 54 is provided.

  The torque-yaw rate conversion unit 54 is supplied with the steering torques Tdf and Tdr calculated from the displacement-torque conversion unit 51. In the fourth embodiment as well, the torque-yaw rate conversion unit 54 executes the calculation described later in the same manner regardless of the steering torques Tdf, Tdr supplied from the displacement-torque conversion unit 51. In the following description, the steering torques Tdf and Tdr are collectively described as the steering torque Td. Then, the torque-yaw rate conversion unit 54 calculates the expected yaw rate γdf that the driver expects by the turning operation of the steering handle 11 according to the following equations 57 and 58, and calculates the expected yaw rate γdr that is expected by the return operation by the following equations 59, Calculate according to 60.

At this time, the torque-yaw rate converter 54 calculates the expected yaw rates γdf and γdr according to the following formulas 57 and 59 if the absolute value of the steering torque Td is less than the positive predetermined value Tg, and the absolute value of the steering torque Td is If the positive predetermined value Tg or more, the calculation is performed according to the following equations 58 and 60. Here, the following expression 57 or 59 is a linear function expression of the steering torque Td as in the first embodiment, and the expected yaw rates γdf and γdr are “0” when the steering torque Td is “0”. is there. The following formulas 58 and 60 are power functions of the steering torque Td as in the above embodiment, and are continuously connected to the following formulas 57 and 59 at a predetermined value Tg.
γdf = b1 · Td (| Td | <Tg) Equation 57
γdf ＝ C ・ Td ^K2 (Tg ≦ | Td |) Equation 58
γdr = b2 · Td−Mh2 (| Td | <Tg)
γdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 60

  However, b1 in the formula 57 and b2 in the formula 59 are constants representing the slope of a linear function, and C and K2 in the formulas 58 and 60 are constants. Further, the steering torque Td in the equations 57-60 represents the absolute value of the steering torque Td calculated using the equations 6-10 (that is, the steering torque Tdf, Tdr), and the calculated steering torque. If Td is positive, the constants b1, b2 and constant C are positive values. If the calculated steering torque Td is negative, the constants b1, b2 and constant C are changed to the positive constants b1, b2 and constant C. A negative value having the same absolute value as

Mh2 in the above formulas 59 and 60 continuously connects the calculated expected yaw rate γdf and the expected yaw rate γdr when the turning operation of the steering handle 11 by the driver is changed from the cutting operation to the returning operation. That is, it is a hysteresis term for configuring a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh2 is determined based on the ratio of the expected yaw rate γdf at the time of the cutting operation and the expected yaw rate γdr at the time of the return operation at the time when a certain steering torque Td is supplied, and is expressed as the following equation 61.
Mh2 = nq · (Kq · Td) ... Formula 61
In Equation 61, Kq is a Weber ratio with respect to the steering torque Td, and nq is a predetermined coefficient for the minimum change sensitivity. In this embodiment as well, the hysteresis term Mh2 is derived without including the steering angle θ as in the formula 61, but instead of or in addition, for example, the hysteresis term Mh2 includes the steering angle θ. It is also possible to derive so as to depend on the steering angle θ.

  Thus, by calculating the hysteresis term Mh2, the expected yaw rate γdf calculated according to the equation 57 or 58 and the expected yaw rate γdr calculated according to the equation 59 or 60 are continuously connected. It is possible to smoothly switch from the yaw rate γdf to the expected yaw rate γdr, and conversely from the expected yaw rate γdr to the expected yaw rate γdf. Further, by calculating the hysteresis term Mh2 according to the equation 61, the expected yaw rates γdf and γdr at the time of change between the cutting operation and the return operation are maintained. Therefore, as will be described later, the left and right front wheels FW1, FW2 steered to the corrected target turning angle δda calculated based on the expected yaw rates γdf, γdr, The change in the steering angle δ can be prevented, and the behavior of the vehicle expected by the driver can be maintained.

  Further, when the steering torque Td is less than the predetermined value Tg, the expected yaw rate γdf and the expected yaw rate γdr are calculated according to the equations 57 and 59, so that the steering handle 11 is rotated across the neutral position. Even in this case, since the expression 57 and the expression 59 are functions passing through the origin “0”, the expected yaw rate γdf and the expected yaw rate γdr are prevented from becoming discontinuous.

  That is, when the value is less than the predetermined value Tg, both of the expressions 57 and 59 are functions that pass through the origin “0”. For this reason, if the driver expects the expected yaw rate, for example, a yaw rate that changes from the right to the left, the torque-lateral acceleration converter 52 converges to “0” in a linear function according to the equation 59 above. The expected yaw rate γdr is calculated, and the expected yaw rate γdf that increases linearly from “0” is calculated according to the equation 57. Therefore, the expected yaw rate γdf and the expected yaw rate γdr are continuous at “0”, and the expected yaw rate γdf, γdr can be switched, and the driver does not feel uncomfortable. In this case as well, instead of calculating the equations 57 to 61, the expected yaw rates γdf and γdr are calculated using a conversion table having characteristics as shown in FIG. 11 storing the expected yaw rates γdf and γdr with respect to the steering torque Td. You may make it do.

  The expected yaw rates γdf and γdr calculated by the torque-yaw rate conversion unit 54 are supplied to the turning angle conversion unit 55. The steered angle conversion unit 55 performs the calculation described later in the same manner regardless of the expected yaw rates γdf and γdr supplied from the torque-yaw rate conversion unit 54. γdf and γdr are collectively described as the expected yaw rate γd. The turning angle conversion unit 55 calculates the target turning angle δd as the first turning angle of the left and right front wheels FW1 and FW2 necessary for generating the expected yaw rate γd, and calculates the compensated target turning angle δdh. Is.

  And the turning angle conversion part 55 has a table which changes according to the vehicle speed V and shows the change characteristic of the target turning angle (delta) d with respect to estimated yaw rate (gamma) d, as shown in FIG. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and yaw rate γ of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 55 calculates the target turning angle δd corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33 with reference to this table. Further, the yaw rate γ (expected yaw rate γd) and the target turning angle δd stored in the table are both positive, but if the expected yaw rate γd supplied from the torque-yaw rate converting unit 54 is negative, the output The target turning angle δd to be performed is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the yaw rate γ as shown in the following formula 62, it can be calculated by executing the calculation of the following formula 62 instead of referring to the table. .
δd = L · (1 + A · V ² ) · γd / V Equation 62
However, also in the formula 62, L is a predetermined value indicating the wheel base, and A is a predetermined value.

  Thus, by calculating the target turning angle δd so as to generate the expected yaw rate γd that is expected based on the reaction force torque Tz (steering torque Td) perceived by the driver via the steering handle 11, the driver Can perceive the expected yaw rate γd expected by the user and can operate the steering handle 11. For this reason, since the vehicle can be driven in a state adapted to the driver's steering sensation, the driving of the vehicle equipped with the steering-by-wire type steering device is simplified.

  By the way, also in the fourth embodiment, for example, when the vehicle is traveling at a low speed such as a low-speed traveling at the time of entering the garage, the driver uses the expected yaw rate γd estimated by the turning operation of the steering handle 11. May not perceive. Thus, when the vehicle is traveling (moving) at a low speed, the driver simply turns the vehicle based on the rotation stroke of the steering handle 11, that is, the steering angle θ. In this turning, the actual turning angle δ can be increased with respect to the steering angle θ, for example, by making the actual turning angle δ proportional to the steering angle θ of the steering handle 11. It can be in a state suitable for human steering feeling.

  In other words, when the vehicle is traveling (moving) at a low speed, as described above, the expected yaw rate γd is based on the steering torque Td (reaction torque Tz) that exponentially changes with respect to the steering angle θ. When the target turning angle δd is determined based on the calculated expected yaw rate γd, the driver turns the vehicle in a desired direction unless the steering wheel 11 is rotated to a larger steering angle θ. You may not be able to do so and feel uncomfortable. On the other hand, there is a high possibility that the driver feels a sense of incongruity when he / she changes to a vehicle equipped with the steering-by-wire steering device described above. It is thought that it will be gradually resolved.

For this reason, also in the fourth embodiment, as in the first embodiment, the vehicle is more appropriate in accordance with the case where the vehicle is traveling (moving) at a low speed or according to the degree of acquisition of the steering characteristics of the steering device by the driver. A compensated target turning angle δdh is calculated by introducing a turning angle compensation function to compensate for the target turning angle δd calculated by the equation 62 so that the actual turning angle δ can be obtained. Hereinafter, the turning angle compensation function will be described in detail. This turning angle compensation function also calculates the compensation target turning angle δdh based on the magnitude of the vehicle speed V of the vehicle and the driver's ability to acquire steering characteristics, as in the first embodiment. expressed.
δh = KRt10 · (KRt00 · γd + KRt01 · (δl / θmax) · θ) + KRt11 · ((δl / θmax) · θ) ... Equation 63
However, KRt00, KRt01, KRt10, and KRt11 are predetermined correction coefficients similar to those in the first embodiment. The relationship shown in the following equation 64 is established between the correction coefficient KRt00 and the correction coefficient KRt01, and the relationship shown in the following equation 65 is established between the correction coefficient KRt10 and the correction coefficient KRt11.
KRt00 + KRt01 = 1 ... Formula 64
KRt10 + KRt11 = 1 ... Formula 65

Here, in particular, as for the correction coefficient KRt01 and the correction coefficient KRt11, as in the first embodiment, the correction coefficient KRt01 is a coefficient for correcting the vehicle speed characteristic, and the correction coefficient KRt11 corrects the driver's steering characteristic acquisition level. These coefficients have the characteristics shown in FIGS. 6A and 6B, respectively. Further, δl in the equation 63 is a target turning angle of the left and right front wheels FW1 and FW2 necessary for generating the maximum yaw rate γdμ that can be taken with the friction coefficient μ of the road surface, and is a function of the vehicle speed V and the yaw rate γ. It is calculated according to a certain formula 66 below.
δl = L · (1 + A · V ² ) · γdμ / V Equation 66
However, also in this equation 66, as in the above equation 62, L is a predetermined value indicating the wheelbase length, and A is a predetermined value.

  Then, the compensation target turning angle δdh is calculated as follows according to the equation 63 in accordance with the detected vehicle speed V and the driver's steering characteristic acquisition level. That is, when the vehicle speed V is high and the set value (travel distance) is large, the correction coefficient KRt01 is set to “0” as shown in FIG. 6A, and the correction coefficient KRt11 is also shown in FIG. The value is set to “0” as shown in b). Therefore, the value of the correction coefficient KRt00 is “1” and the value of the correction coefficient KRt10 is “1” in accordance with the equations 64 and 65. Thereby, the compensated target turning angle δdh based on the equation 63 becomes equal to the target turning angle δd calculated according to the equation 62, and the steering characteristic according to the above-mentioned Weber-Hefner law can be obtained. , Driving becomes easy.

  When the vehicle speed V is low and the set value (travel distance) is extremely small, the correction coefficient KRt01 is set to “1” as shown in FIG. 6A, and the correction coefficient KRt11 is also set in FIG. As shown in (b), the value is substantially “1”. Therefore, according to the equations 64 and 65, the value of the correction coefficient KRt00 is “0”, and the value of the correction coefficient KRt10 is “0”. As a result, the compensation target turning angle δdh based on the equation 63 becomes (δl / θmax) · θ as the second turning angle, which is proportional to the steering angle θ. Therefore, even when the driver turns the vehicle based on the turning stroke of the steering handle 11 without perceiving the expected yaw rate γd at a low speed, the actual turning angle δ with respect to the steering angle θ is large. The steering handle 11 can be rotated in a state adapted to the steering sensation. Even if the driving distance is very small and the driver's steering characteristics are still insufficient, the vehicle can be driven very easily without feeling uncomfortable by making the relationship proportional to the steering angle θ. Can be swiveled.

  Further, when the vehicle speed V is large and the set value (travel distance) is extremely small, or when the vehicle speed V is small and the set value (travel distance) is large, the compensation target turning angle δdh based on the equation 63 is (δl / θmax) · θ, which is proportional to the steering angle θ. Accordingly, even when the driver turns the vehicle at a low speed based on the rotation stroke of the steering handle 11, the actual steering angle δ with respect to the steering angle θ is large, so that the driver can steer in a state suitable for human steering feeling. The handle 11 can be rotated. In particular, the value of the correction coefficient KRt11 is uniformly reduced from “1” to “0” according to the travel distance of the vehicle. Therefore, according to the driver's steering characteristic acquisition level, the correction coefficient KRt11 · The ((δl / θmax) · θ) term decreases to “0”. For this reason, after fully learning the steering characteristics of the steering device, the driver perceives the steering characteristics according to Weber-Hefner's law when the vehicle speed V is high, and the steering angle when the vehicle speed V is low. A steering characteristic proportional to θ is perceived. Therefore, good steering characteristics can be obtained in any vehicle speed range, and driving can be simplified.

  Further, when the vehicle speed V is large to some extent and the set value (travel distance) is large to some extent, the correction coefficients KRt00, KRt01, KRt10, and KRt11 have values of “1” to “0” (“0” to “1”, respectively). )). Thus, the compensated target turning angle δdh calculated according to the equation 63 is set to a value larger than the target turning angle δd calculated according to the equation 62. Therefore, the driver can obtain the optimum steering characteristics according to the vehicle speed V and the learning characteristics of the steering characteristics, and can simplify the driving.

The calculated compensation target turning angle δdh is supplied to the turning angle correction unit 63 of the turning control unit 60. The turning angle correction unit 63 receives the expected yaw rate γd from the torque-yaw rate conversion unit 54 and also the actual yaw rate γ detected by the yaw rate sensor 39, and executes the calculation of the following equation 67. The corrected target turning angle δda is calculated by correcting the input compensation target turning angle δdh.
δda = δd + K5 · (γd−γ) Equation 67
However, the coefficient K5 is a predetermined positive constant. When the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angle δ of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd is more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment. In the functional block diagram of FIG. 10, the same reference numerals as those in FIG.

  Also in the fourth embodiment described above, the steering angle θ as an operation input value of the driver with respect to the steering handle 11 is changed to the steering torque Tdr to which the steering torque Tdf or the hysteresis term Mh1 is applied by the displacement-torque converter 51. Converted. Further, the converted steering torques Tdf and Tdr are converted by the torque-yaw rate conversion unit 54 into the expected yaw rate γdr to which the expected yaw rate γdf or the hysteresis term Mh2 is given. Then, the turning angle conversion unit 55 appropriately changes the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11 as ratios according to the vehicle speed V and the set value (travel distance) to generate the expected yaw rates γdf and γdr. A compensation target turning angle δdh consisting of (δl / θmax) · θ proportional to the steering angle θ required for the above and the steering angle θ is calculated. The calculated compensation target turning angle δdh is corrected to the corrected target turning angle δda by the turning angle correction unit 63, and the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda by the drive control unit 62. The

  Then, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is large or the mileage is large and the driver has sufficiently mastered the steering characteristics of the steering device, for example, target steering By increasing the ratio of the angle δd, that is, by setting the correction coefficients KRt00 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on the target turning angle δd. Therefore, when the vehicle turns with the corrected target turning angle δda, the driver is given the expected yaw rates γdf and γdr as the “physical quantities of the applied stimulus” according to the Weber-Hefner law. The expected yaw rates γdf and γdr are exponential functions with respect to the steering torque Td (reaction force torque Tz) applied to the steering wheel 11 (by transforming Equations 58 and 60 in the same manner as transforming Equation 12 into Equation 16). Therefore, the driver can operate the steering wheel 11 while perceiving a motion state amount that matches human perception characteristics. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is low or the mileage is short and the driver has not sufficiently mastered the steering characteristics of the steering device, for example, ( By increasing the ratio of δl / θmax) · θ, that is, by setting the correction coefficients KRt01 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on (δl / θmax) · θ. Therefore, when the vehicle turns with the corrected target turning angle δda, the driver can turn the vehicle at a turning angle proportional to the steering angle θ with respect to the steering handle 11, and thus the steering characteristics are not sufficiently learned. Even so, the vehicle can be easily turned based on experience with a conventional mechanically coupled steering device.

  Also in the fourth embodiment, as in the first embodiment, in order to eliminate the uncomfortable feeling that the driver learns when the vehicle travels (moves) at a low speed or when the steering characteristics are not sufficiently learned. Then, a turning angle compensation function for compensating the turning angle δd was introduced, and the compensation turning angle δdh having a proportional relationship with the steering angle θ input by the driver was calculated. As a result, the vehicle turns according to the linear steering characteristics with respect to the rotation stroke of the steering handle 11 of the driver, so that even if the vehicle moves at a low speed or the steering characteristics are not sufficiently learned, I didn't feel uncomfortable.

  By the way, also in the said 4th Embodiment, until the actual turning angle (delta) with respect to steering angle (theta) with respect to the steering wheel 11 generate | occur | produces the driver's uncomfortable feeling mentioned above, when a driver | operator requires a big actual turning angle. It may be felt by the time delay. That is, the target turning angle δd in the fourth embodiment is an expected yaw rate γd (that is, exponential function) that changes exponentially with respect to the steering torque Td (ie, the steering torque Tdf, Tdr) according to the equation 62 (that is, Calculated based on the expected yaw rate (γdf, γdr). Further, the steering torque Td (steering torques Tdf, Tdr) is calculated so as to change exponentially with respect to the steering angle θ as the operation input value by the driver according to the expressions 7 and 9 above the predetermined value Tg. Is done. For this reason, when the driver needs a large actual turning angle, the steering handle 11 must be rotated more than the conventional mechanically coupled steering device. This makes the driver feel uncomfortable. Therefore, also in the fourth embodiment, the steering torque Td (steering torque Tdf, Tdr) is increased with respect to the steering angle θ as the operation input value by the driver, particularly during low-speed traveling (movement). Then, the time delay until the actual turning angle δ required by the driver is generated can be reduced. Hereinafter, modified examples of the fourth embodiment will be described in detail.

  Also in the modification according to the fourth embodiment, a torque compensation function similar to that of the first embodiment of the first embodiment is introduced and supplied from the displacement-torque converter 51 to the torque-yaw rate converter 54. Compensation steering torque Tdh (compensation steering torque Tdfh, Tdrh) is calculated by greatly compensating steering torque Td (steering torque Tdf, Tdr) as one operating force.

  The calculated compensated steering torque Tdh (compensated steering torque Tdfh, Tdrh) is supplied to the torque-yaw rate converter 54. The torque-yaw rate conversion unit 54 calculates the expected yaw rate γd (expected yaw rate γdf, γdr) according to the equations 57 to 61 using the supplied compensation steering torque Tdh. Also in this case, it is possible to calculate the expected yaw rate γd (expected yaw rate γdf, γdr) using the conversion table having the characteristics shown in FIG. Then, the calculated expected yaw rate γd is supplied to the turning angle conversion unit 55, and the target turning angle δd is calculated according to the equation 62, and the calculated target turning angle δd is changed to the turning of the turning control unit 60. The correction target turning angle δda is calculated by being corrected by the steering angle correction unit 63. Therefore, since the expected yaw rate γd (expected yaw rate γdf, γdr) is calculated based on the compensated steering torque Tdh, the steering delay is eliminated, and the uncomfortable feeling that the driver feels as in the second embodiment can be eliminated. .

e. Fifth Embodiment Next, a fifth embodiment of the present invention using a turning curvature instead of the lateral acceleration as the motion state quantity in the first embodiment will be described. The fifth embodiment is also configured as shown in FIG. 1 as in the first embodiment. However, the computer program executed by the electronic control unit 35 is slightly different from the case of the first embodiment.

  In the fifth embodiment, the computer program executed by the electronic control unit 35 is shown by the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment, but instead of the torque-lateral acceleration conversion unit 52 in the first embodiment, a torque-curvature conversion unit. 56 is provided.

  The torque-curvature conversion unit 56 is supplied with the steering torques Tdf and Tdr calculated from the displacement-torque conversion unit 51. In the fifth embodiment as well, the torque-curvature conversion unit 56 executes the calculation described later in the same manner regardless of the steering torque Tdf, Tdr supplied from the displacement-torque conversion unit 51. In the following description, the steering torques Tdf and Tdr are collectively described as the steering torque Td. Then, the torque-curvature conversion unit 56 calculates the expected turning curvature ρdf by the driver's turning operation of the steering handle 11 according to the following formulas 68 and 69, and calculates the expected turning curvature ρdr expected by the return operation by the following formulas 70 and 71. Calculate according to

At this time, the torque-curvature conversion unit 56 calculates the expected turning curvatures ρdf and ρdr according to the following formulas 68 and 70 if the absolute value of the steering torque Td is less than the positive predetermined value Tg, and the absolute value of the steering torque Td. If is a positive predetermined value Tg or more, calculation is performed according to the following formulas 69 and 71. Here, the following expression 68 or 70 is a linear function expression of the steering torque Td as in the first embodiment, and the functions for which the expected turning curvatures ρdf and ρdr are “0” when the steering torque Td is “0”. It is. The following formulas 69 and 71 are power functions of the steering torque Td as in the first embodiment, and are continuously connected to the following formulas 68 and 70 at a predetermined value Tg.
ρdf = b1 · Td (| Td | <Tg) Equation 68
ρdf = C · Td ^K2 (Tg ≦ | Td |) Equation 69
ρdr = b2 · Td−Mh2 (| Td | <Tg) Equation 70
ρdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 71

  However, b1 in the formula 68 and b2 in the formula 70 are constants representing the slope of a linear function, and C and K2 in the formulas 69 and 71 are constants. The steering torque Td in the equations 68 to 71 represents the absolute value of the steering torque Td calculated using the equations 6 to 10 (that is, the steering torques Tdf and Tdr), and the calculated steering torque. If Td is positive, the constants b1, b2 and constant C are positive values. If the calculated steering torque Td is negative, the constants b1, b2 and constant C are changed to the positive constants b1, b2 and constant C. A negative value having the same absolute value as

Further, Mh2 in the above formulas 70 and 71 represents the calculated expected turning curvature ρdf and expected turning curvature ρdr continuously when the turning operation of the steering handle 11 by the driver is changed from the cutting operation to the returning operation. In other words, the hysteresis term is used to construct a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh2 is determined based on the ratio of the expected turning curvature ρdf at the time of the cutting operation and the expected turning curvature ρdr at the time of the return operation at the time when a certain steering torque Td is supplied, and is expressed as the following Expression 72. The
Mh2 = nq · (Kq · Td) ... Formula 72
In the equation 72, Kq is a Weber ratio with respect to the steering torque Td, and nq is a predetermined coefficient for the minimum change sensitivity. In the present embodiment, the hysteresis term Mh2 is derived without including the steering angle θ as in the equation 72, but instead of or in addition, for example, the hysteresis term Mh2 includes the steering angle θ. It is also possible to derive so as to depend on the steering angle θ.

  Since the hysteresis term Mh2 is thus calculated, the expected turning curvature ρdf calculated according to the equation 68 or 69 and the expected turning curvature ρdr calculated according to the equation 70 or 71 are continuously connected. Thus, it is possible to smoothly switch from the expected turning curvature ρdf to the expected turning curvature ρdr, and conversely from the expected turning curvature ρdr to the expected turning curvature ρdf. Further, by calculating the hysteresis term Mh2 according to the equation 72, the expected turning curvatures ρdf and ρdr at the time of change between the cutting operation and the returning operation are maintained. For this reason, as will be described later, the left and right front wheels FW1 and FW2 steered to the corrected target turning angle δda calculated based on the expected turning curvatures ρdf and ρdr are caused by, for example, a disturbance input from the road. It is possible to prevent the turning angle δ from changing, and to maintain the behavior of the vehicle as expected by the driver.

  Further, when the steering torque Td is less than the predetermined value Tg, the expected turning curvature ρdf and the expected turning curvature ρdr are calculated according to the formula 68 and the formula 70, so that the steering handle 11 is turned over the neutral position. Even in this case, since the expression 68 and the expression 70 are functions passing through the origin “0”, the expected turning curvature ρdf and the expected turning curvature ρdr are prevented from becoming discontinuous.

  That is, when the value is less than the predetermined value Tg, both of the formula 68 and the formula 70 are functions that pass through the origin “0”. For this reason, if the driver expects the expected turning curvature to change from the right direction to the left direction, for example, the torque-curvature conversion unit 56 linearly becomes “0” according to the above equation 70. The convergent expected turning curvature ρdr is calculated, and the expected turning curvature ρdf that increases linearly from “0” according to the equation 68 is calculated. Therefore, the expected turning curvature ρdf and the expected turning curvature ρdr are continuous at “0”, and when the perceived direction of the expected turning curvature changes, in other words, even when the detected steering angle θ reverses positive and negative, it is expected to be extremely smooth. The turning curvature ρdf, ρdr can be switched, and the driver does not feel uncomfortable. In this case as well, instead of the calculation of the equations 68 to 72, the expected turning curvature ρdf, using the conversion table having the characteristics as shown in FIG. 14 storing the expected turning curvature ρdf, ρdr with respect to the steering torque Td. ρdr may be calculated.

  The expected turning curvatures ρdf and ρdr calculated by the torque-curvature conversion unit 56 are supplied to the turning angle conversion unit 57. The steered angle conversion unit 57 executes the calculation described later in the same way regardless of the expected turning curvatures ρdf and ρdr supplied from the torque-curvature conversion unit 56. The turning curvatures ρdf and ρdr are collectively described as the expected turning curvature ρd. The turning angle conversion unit 57 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected turning curvature ρd, and calculates the compensated target turning angle δdh.

  And the turning angle conversion part 57 has a table which changes according to the vehicle speed V, and shows the change characteristic of the target turning angle (delta) d with respect to estimated turning curvature (rho) d as shown in FIG. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the turning curvature ρ of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 57 refers to this table and calculates a target turning angle δd corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33. The turning curvature ρ (expected turning curvature ρd) and the target turning angle δd stored in the table are both positive, but the expected turning curvature ρd supplied from the turning angle conversion unit 57 is negative. In this case, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the turning curvature ρ as shown in the following equation 73, the target turning angle δd can be calculated by executing the operation of the following equation 73 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 73
However, also in the equation 73, L is a predetermined value indicating the wheelbase length, and A is a predetermined value.

  In this way, by calculating the target turning angle δd so as to generate the expected turning curvature ρd based on the reaction force torque Tz (steering torque Td) perceived by the driver via the steering handle 11, driving is performed. The person can perceive the expected turning curvature ρd expected by the person and can operate the steering handle 11. For this reason, since the vehicle can be driven in a state adapted to the driver's steering sensation, the driving of the vehicle equipped with the steering-by-wire type steering device is simplified.

  By the way, also in the fifth embodiment, for example, when the vehicle is traveling at a low speed such as a low-speed traveling at the time of entering the garage, the driver is simply based on the turning stroke of the steering handle 11, that is, the steering angle θ. Turn the vehicle. In this turning, the actual turning angle δ can be increased with respect to the steering angle θ, for example, by making the actual turning angle δ proportional to the steering angle θ of the steering handle 11. It can be in a state suitable for human steering feeling.

  In other words, when the vehicle is traveling (moving) at a low speed, as described above, the expected turning curvature ρd based on the steering torque Td (reaction torque Tz) that changes exponentially with respect to the steering angle θ. When the target turning angle δd is determined based on the determined expected turning curvature ρd, the driver does not turn the steering handle 11 to a larger steering angle θ in the desired direction of the vehicle. You may not be able to turn, and you may feel uncomfortable. On the other hand, it is highly likely that the driver feels a sense of incongruity at the beginning of changing to a vehicle equipped with the steering-by-wire steering device according to the present invention, so that the driver gets used to the steering characteristic of the steering device, that is, acquires the steering characteristic. It is thought that it will be gradually solved.

For this reason, in the fifth embodiment as well, as in the first embodiment, the vehicle is more appropriate in accordance with the case where the vehicle is traveling (moving) at a low speed or depending on how the driver acquires the steering characteristics of the steering device. In order to obtain the actual turning angle δ, the turning angle compensation function is introduced to compensate the target turning angle δd calculated by the above equation 73 to calculate the compensated target turning angle δdh. Hereinafter, the turning angle compensation function in the fifth embodiment will be described in detail. This turning angle compensation function also calculates the compensation target turning angle δdh based on the magnitude of the vehicle speed V of the vehicle and the driver's acquisition of steering characteristics as in the first embodiment. expressed.
δh = KRt10 · (KRt00 · ρd + KRt01 · (δl / θmax) · θ) + KRt11 · ((δl / θmax) · θ)
However, KRt00, KRt01, KRt10, and KRt11 are predetermined correction coefficients similar to those in the first embodiment. The relationship shown in the following formula 75 is established between the correction coefficient KRt00 and the correction coefficient KRt01, and the relationship shown in the following formula 76 is established between the correction coefficient KRt10 and the correction coefficient KRt11.
KRt00 + KRt01 = 1 ... Formula 75
KRt10 + KRt11 = 1 ... Formula 76

Here, in particular, as for the correction coefficient KRt01 and the correction coefficient KRt11, as in the first embodiment, the correction coefficient KRt01 is a coefficient for correcting the vehicle speed characteristic, and the correction coefficient KRt11 corrects the driver's steering characteristic acquisition level. These coefficients have the characteristics shown in FIGS. 6A and 6B, respectively. Further, δl in the equation 74 is a target turning angle of the left and right front wheels FW1 and FW2 necessary for generating the maximum turning curvature ρdμ that can be taken with the road friction coefficient μ, and is a function of the vehicle speed V and the yaw rate γ. Is calculated according to the following equation 77.
δl = L · (1 + A · V ² ) · ρdμ Equation 77
However, in this formula 77 as well, as in the formula 73, L is a predetermined value indicating the wheelbase length, and A is a predetermined value.

  Then, the compensation target turning angle δdh is calculated as follows according to the equation 74 according to the detected vehicle speed V and the driver's steering characteristic acquisition level. That is, when the vehicle speed V is high and the set value (travel distance) is large, the correction coefficient KRt01 is set to “0” as shown in FIG. 6A, and the correction coefficient KRt11 is also shown in FIG. The value is set to “0” as shown in b). Therefore, the value of the correction coefficient KRt00 is “1” and the value of the correction coefficient KRt10 is “1” in accordance with the formulas 75 and 76. Thereby, the compensation target turning angle δdh based on the equation 74 becomes equal to the target turning angle δd as the first turning angle calculated according to the equation 73, and the steering according to the above-mentioned Weber-Hefner law is performed. The characteristics can be obtained and the operation becomes simple.

  When the vehicle speed V is low and the set value (travel distance) is extremely small, the correction coefficient KRt01 is set to “1” as shown in FIG. 6A, and the correction coefficient KRt11 is also set in FIG. As shown in (b), the value is substantially “1”. Therefore, the value of the correction coefficient KRt00 is “0” and the value of the correction coefficient KRt10 is “0” in accordance with the formulas 75 and 76. Thus, the compensation target turning angle δdh based on the equation 74 is (δl / θmax) · θ as the second turning angle, and is in a relationship proportional to the steering angle θ. Accordingly, even when the driver turns the vehicle at a low speed based on the rotation stroke of the steering handle 11, the actual steering angle δ with respect to the steering angle θ is large, so that the driver can steer in a state suitable for human steering feeling. The handle 11 can be rotated. Even if the driving distance is very small and the driver's steering characteristics are still insufficient, the vehicle can be driven very easily without feeling uncomfortable by making the relationship proportional to the steering angle θ. Can be swiveled.

  Further, when the vehicle speed V is large and the set value (travel distance) is extremely small, or when the vehicle speed V is small and the set value (travel distance) is large, the compensation target turning angle δdh based on the equation 74 is (δl / θmax) · θ, which is proportional to the steering angle θ. Accordingly, even when the driver turns the vehicle at a low speed based on the rotation stroke of the steering handle 11, the actual steering angle δ with respect to the steering angle θ is large, so that the driver can steer in a state suitable for human steering feeling. The handle 11 can be rotated. In particular, the correction coefficient KRt11 is uniformly reduced from “1” to “0” according to the travel distance of the vehicle. Therefore, the correction coefficient KRt11 in the equation 74 depends on how the driver acquires the steering characteristics. The ((δl / θmax) · θ) term decreases to “0”. For this reason, after fully learning the steering characteristics of the steering device, the driver perceives the steering characteristics according to Weber-Hefner's law when the vehicle speed V is high, and the steering angle when the vehicle speed V is low. A steering characteristic proportional to θ is perceived. Therefore, good steering characteristics can be obtained in any vehicle speed range, and driving can be simplified.

  Further, when the vehicle speed V is large to some extent and the set value (travel distance) is large to some extent, the correction coefficients KRt00, KRt01, KRt10, and KRt11 have values of “1” to “0” (“1” to “0”, respectively). )). Thus, the compensated target turning angle δdh calculated according to the equation 74 is set to a value larger than the target turning angle δd calculated according to the equation 73. Therefore, the driver can obtain the optimum steering characteristics according to the vehicle speed V and the learning characteristics of the steering characteristics, and can simplify the driving.

The calculated compensation target turning angle δdh is supplied to the turning angle correction unit 64 of the turning control unit 60. The turning angle correction unit 64 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 56 and also receives the actual turning curvature ρ from the turning curvature calculation unit 65. The turning curvature calculation unit 65 uses the lateral acceleration G detected by the lateral acceleration sensor 34, the yaw rate γ detected by the yaw rate sensor 39, and the vehicle speed V detected by the vehicle speed sensor 33, and the following equation 78 By executing this calculation, the actual turning curvature ρ is calculated and output to the turning angle correction unit 64.
ρ = G / V ² or ρ = γ / V Equation 78

Then, the turning angle correction unit 64 calculates the corrected target turning angle δda by correcting the input compensation target turning angle δdh by executing the following equation 79.
δda = δdh + K7 · (ρd−ρ) Equation 79
However, the coefficient K7 is a predetermined positive constant, and when the actual turning curvature ρ is less than the expected turning curvature ρ, the coefficient K7 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. When the actual turning station rate ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd are more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment. And in the functional block diagram of FIG. 13, the same code | symbol as FIG. 2 of the said 1st Embodiment is attached | subjected, and the description is abbreviate | omitted.

  Also in the fifth embodiment described above, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is changed to the steering torque Tdr to which the steering torque Tdf or the hysteresis term Mh1 is given by the displacement-torque converter 51. Converted. The converted steering torques Tdf and Tdr are converted by the torque-turning curvature converting unit 56 into the expected turning curvature ρdr to which the expected turning curvature ρdf or the hysteresis term Mh2 is given. Then, the turning angle conversion unit 57 appropriately changes the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11 as ratios according to the vehicle speed V and the set value (travel distance), and the expected turning curvatures ρdf, ρdr A compensation target turning angle Δdh consisting of (Δl / θmax) · θ proportional to the steering angle θ required for generation and the steering angle θ is calculated. The calculated compensation target turning angle δdh is corrected to the corrected target turning angle δda by the turning angle correction unit 63, and the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda by the drive control unit 62. The

  Then, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is large or the mileage is large and the driver has sufficiently mastered the steering characteristics of the steering device, for example, target steering By increasing the ratio of the angle δd, that is, by setting the correction coefficients KRt00 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on the target turning angle δd. Therefore, when the vehicle turns with this corrected target turning angle δda, the driver is given the expected turning curvatures ρdf and ρdr as the “physical quantities of the given stimulus” according to the Weber-Hefner law. . The expected turning curvatures ρdf and ρdr are exponential functions with respect to the steering torque Td (reaction torque Tz) applied to the steering wheel 11 (formulas 69 and 71 are transformed in the same way as transforming formula 12 into formula 16). Therefore, the driver can operate the steering wheel 11 while perceiving a motion state amount that matches human perception characteristics. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, when changing the values of the correction coefficients KRt00, KRt01, KRt10, and KRt11, when the vehicle speed V is low or the mileage is short and the driver has not sufficiently mastered the steering characteristics of the steering device, for example, ( By increasing the ratio of δl / θmax) · θ, that is, by setting the correction coefficients KRt01 and KRt11 to “1”, the steered wheels are steered to the corrected target turning angle δda based on (δl / θmax) · θ. Therefore, when the vehicle turns with the corrected target turning angle δda, the driver can turn the vehicle at a turning angle proportional to the steering angle θ with respect to the steering handle 11, and thus the steering characteristics are not sufficiently learned. Even so, the vehicle can be easily turned based on experience with a conventional mechanically coupled steering device.

  Also in the fifth embodiment, as in the first embodiment, in order to eliminate the uncomfortable feeling that the driver learns when the vehicle travels (moves) at a low speed or when the steering characteristics are not sufficiently learned. Then, a turning angle compensation function that compensates the target turning angle δd was introduced, and the compensation target turning angle δdh having a proportional relationship with the steering angle θ input by the driver was calculated. As a result, the vehicle turns according to the linear steering characteristics with respect to the rotation stroke of the steering handle 11 of the driver, so that even if the vehicle moves at a low speed or the steering characteristics are not sufficiently learned, I didn't feel uncomfortable.

  By the way, also in the said 5th Embodiment, the driver | operator's discomfort mentioned above is until the actual turning angle (delta) with respect to the steering angle (theta) of the steering wheel 11 generate | occur | produces, when a driver | operator requires a big actual turning angle. It may be felt by the time delay. That is, the target turning angle δd in the fifth embodiment is a predicted turning curvature ρd (exponentially) that changes exponentially with respect to the steering torque Td (ie, the steering torque Tdf, Tdr) according to the equation 73. That is, it is calculated based on the expected turning curvature (ρdf, ρdr). Further, the steering torque Td (steering torques Tdf, Tdr) is calculated so as to change exponentially with respect to the steering angle θ as the operation input value by the driver according to the expressions 7 and 9 above the predetermined value Tg. Is done. For this reason, when the driver needs a large actual turning angle, the steering handle 11 must be rotated more than the conventional mechanically coupled steering device. This makes the driver feel uncomfortable. Therefore, also in the fifth embodiment, the steering torque Td (steering torques Tdf, Tdr) is increased with respect to the steering angle θ as an operation input value by the driver, particularly during low-speed travel (movement). If so, the time delay until the actual turning angle δ required by the driver is generated can be reduced. Hereinafter, modified examples of the fifth embodiment will be described in detail.

  Also in the modification according to the fifth embodiment, the same torque compensation function as that of the first modification of the first embodiment is introduced and supplied from the displacement-torque conversion unit 51 to the torque-yaw rate conversion unit 54. The steering torque Td (steering torque Tdf, Tdr) as the first operating force is greatly compensated to calculate the compensated steering torque Tdh (compensated steering torque Tdfh, Tdrh).

  The calculated compensated steering torque Tdh (compensated steering torque Tdfh, Tdrh) is supplied to the torque-turning curvature converting unit 56. The torque-turning curvature conversion unit 56 calculates the expected turning curvature ρd (expected turning curvatures ρdf, ρdr) according to the equations 74 to 77 using the supplied compensation steering torque Tdh. Even in this case, the expected turning curvature ρd (expected turning curvatures ρdf, ρdr) can be calculated using the conversion table having the characteristics shown in FIG. Then, the calculated expected turning curvature ρd is supplied to the turning angle conversion unit 57, the target turning angle δd is calculated according to the equation 73, and the calculated target turning angle δd is calculated by the turning control unit 60. The correction target turning angle δda is calculated by being corrected by the turning angle correction unit 64. Therefore, since the expected turning curvature ρd (expected turning curvatures ρdf, ρdr) is calculated based on the compensated steering torque Tdh, the steering delay is eliminated, and the uncomfortable feeling that the driver learns as in the fifth embodiment is eliminated. Can do.

d. Other Modifications Further, the present invention is not limited to the first to fifth embodiments and these modifications, and various modifications can be made without departing from the object of the present invention. .

  For example, in the first to fifth embodiments and the modifications thereof, the steering handle 11 that is turned to steer the vehicle is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  In the first to fifth embodiments and the modifications thereof, the left and right front wheels FW1 and FW2 are steered by rotating the steered output shaft 22 using the steered actuator 21. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 23 using the steered actuator 13.

  Further, in the first to fifth embodiments and the modifications thereof, the lateral acceleration, the yaw rate, and the turning curvature are each independently used as the motion state quantity of the vehicle that can be perceived by humans. However, the vehicle steering control may be performed by switching the amount of motion state of these vehicles by a selection operation by the driver or by automatically switching according to the traveling state of the vehicle. When switching automatically according to the running state of the vehicle, for example, the turning curvature is used as the motion state quantity when the vehicle is running at low speed, the yaw rate is used as the motion state quantity when the vehicle is running at medium speed, and the vehicle is running at high speed. Sometimes, lateral acceleration is used as the motion state quantity. According to this, appropriate steering control of the vehicle is performed according to the running state of the vehicle, and the driving of the vehicle becomes easier.

It is the schematic of the steering apparatus of the vehicle common to 1st thru | or 3rd embodiment of this invention. FIG. 2 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the first embodiment of the present invention. It is a graph which shows the relationship between a steering angle and a steering torque. It is a graph which shows the relationship between steering torque and estimated lateral acceleration. It is a graph which shows the relationship between a prospective lateral acceleration and a target turning angle. It is a functional block diagram functionally showing the computer program processing. (A) is a graph showing the change of the correction coefficient KRt01 with respect to the vehicle speed, and (b) is a graph showing the change of the correction coefficient KRt11 with respect to the set value (travel distance). (A), (b) is related with the modification which concerns on this invention, (a) shows the change with respect to the vehicle speed of the correction coefficient KRs01, (b) is a graph which shows the change with respect to the steering angle of the correction coefficient KRs11. FIG. 5A is a graph showing a change of the coefficient KRs0 with respect to the vehicle speed, and FIG. 5B is a graph showing a change of the coefficient KRm0 with respect to the vehicle speed according to the second embodiment of the present invention. FIG. 5A is a graph showing a change of the correction coefficient KRt0 with respect to the vehicle speed, and FIG. 5B is a graph showing a change of the correction coefficient KRm00 with respect to the steering angle according to the third embodiment of the present invention. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a fourth embodiment of the present invention. It is a graph which shows the relationship between steering torque and estimated yaw rate. It is a graph which shows the relationship between an expected yaw rate and a target turning angle. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a fifth embodiment of the present invention. It is a graph which shows the relationship between steering torque and prospective turning curvature. It is a graph which shows the relationship between a prospective turning curvature and a target turning angle.

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, 33 DESCRIPTION OF SYMBOLS ... Vehicle speed sensor 34 ... Lateral acceleration sensor 35 ... Electronic control unit 38 ... Steering torque sensor 39 ... Yaw rate sensor 40 ... Reaction force control part 50 ... Sensory adaptation control part 51 ... Displacement-torque conversion part 52 ... torque-lateral acceleration conversion unit, 53, 55, 57 ... turning angle conversion unit, 54 ... torque-yaw rate conversion unit, 56 ... torque-turning curvature conversion unit, 60 ... steering control unit, 61, 63, 64 ... Steering angle correction unit

Claims (13)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
The estimated motion state quantity of the vehicle, which represents the motion state of the vehicle perceived by the driver in relation to the turning of the vehicle and has a predetermined exponential relationship or a power relationship with the operation input value to the steering wheel, is detected. Motion state quantity calculating means for calculating using the manipulated input value;
A first turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity is calculated using the calculated expected motion state quantity in the exponential relationship or power relationship. Turning angle calculation means,
Second turning angle calculation means for calculating a second turning angle of the steered wheels that is proportional to the operation input value detected by the operation input value detection means;
Wherein the ratio ratio of the second turning angle calculated by the first steering angle and the second steering angle calculating means is calculated by the first steering angle calculating means when the travel distance of the vehicle is smaller first thereby changing the ratio of 2 turning angle is increased to a ratio changing means for calculating a turning angle by adding the first turning angle and the second steering angle based on the ratio obtained by the change,
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device. A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
The estimated motion state quantity of the vehicle, which represents the motion state of the vehicle perceived by the driver in relation to the turning of the vehicle and has a predetermined exponential relationship or a power relationship with the operation input value to the steering wheel, is detected. Motion state quantity calculating means for calculating using the manipulated input value;
A first turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity is calculated using the calculated expected motion state quantity in the exponential relationship or power relationship. Turning angle calculation means,
Second turning angle calculation means for calculating a second turning angle of the steered wheels that is proportional to the operation input value detected by the operation input value detection means;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
The vehicle speed detected by the vehicle speed detecting means is small as a ratio between the first turning angle calculated by the first turning angle calculating means and the second turning angle calculated by the second turning angle calculating means. Sometimes the ratio of the second turning angle is increased and changed, and the ratio changing means for calculating the turning angle by adding the first turning angle and the second turning angle based on the changed ratio; ,
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device. The second turning angle calculation means includes
When the vehicle speed detected by the vehicle speed detecting means is less than a predetermined vehicle speed, the operation input of the second turning angle calculated based on the proportional relationship is calculated based on the second turning angle near the neutral position of the steering handle. 3. A steering-by-wire vehicle steering apparatus according to claim 2 , wherein calculation is performed based on a predetermined relationship that results in a small change amount compared to a change amount with respect to the value. 4. The steering-by-wire vehicle steering apparatus according to claim 3 , wherein the predetermined relationship used by the second turning angle calculation means is a predetermined exponential relationship with the operation input value. 5. A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
First operating force calculating means for calculating a first operating force applied to the steering wheel, which is exponentially related to the operation input value detected by the operation input value detecting means;
Second operating force calculation means that calculates a second operating force that is proportional to the operation input value detected by the operation input value detection means and that is applied to the steering wheel;
The ratio between the first operating force calculated by the first operating force calculating means and the second operating force calculated by the second operating force calculating means is the second operation when the operation input value for the steering wheel is small. A ratio changing means for increasing and changing the force ratio, and adding the first operating force and the second operating force based on the changed ratio to calculate the operating force applied to the steering wheel;
A vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and a predicted motion state amount of the vehicle that is in a predetermined exponential relationship or a power relationship with the operation force applied to the steering handle, A motion state quantity calculating means for calculating using the calculated operation force;
Steering angle calculation for calculating the turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity using the calculated expected motion state quantity in the calculated exponential relationship or power relationship Means,
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device. A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
First operating force calculating means for calculating a first operating force applied to the steering wheel, which is exponentially related to the operation input value detected by the operation input value detecting means;
Second operating force calculation means that calculates a second operating force that is proportional to the operation input value detected by the operation input value detection means and that is applied to the steering wheel;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
When the vehicle speed detected by the vehicle speed detecting means is small, the ratio between the first operating force calculated by the first operating force calculating means and the second operating force calculated by the second operating force calculating means is A ratio changing means for increasing and changing the ratio of the two operating forces, and adding the first operating force and the second operating force based on the changed ratio to calculate the operating force applied to the steering wheel;
A vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and a predicted motion state amount of the vehicle that is in a predetermined exponential relationship or a power relationship with the operation force applied to the steering handle, A motion state quantity calculating means for calculating using the calculated operation force;
Steering angle calculation for calculating the turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity using the calculated expected motion state quantity in the calculated exponential relationship or power relationship Means,
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device. The second operating force calculation means includes
The second operating force in the vicinity of the neutral position of the steering wheel is based on a predetermined relationship in which the amount of change is smaller than the amount of change of the second operating force calculated based on the proportional relationship with respect to the operation input value. The steering device for a steering-by-wire vehicle according to claim 5 or 6 to be calculated. 8. The steering-by-wire vehicle steering apparatus according to claim 7 , wherein the predetermined relationship used by the second operating force calculation means is a predetermined exponential relationship with the operation input value. In the steering device for a steering-by-wire vehicle according to any one of claims 1 , 2, 5, and 6 ,
The operation input value detection means includes a displacement amount sensor that detects the displacement amount of the steering wheel,
The motion state quantity calculating means includes an operation force conversion means for converting the detected displacement amount into an operation force applied to the steering handle, and an exercise state for converting the converted operation force into the expected motion state quantity. A steering-by-wire vehicle steering apparatus comprising a quantity conversion means. In the steering device for a steering-by-wire vehicle according to any one of claims 1 , 2, 5, and 6 ,
The operation input value detection means includes an operation force sensor that detects and outputs an operation force input to the steering handle, and
A steering-by-wire vehicle steering apparatus, wherein the motion state quantity calculating means is composed of motion state quantity conversion means for converting the detected operating force into the expected motion state quantity. The steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 10 ,
The predicted motion state quantity is a steering-by-wire vehicle steering apparatus that is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle. The steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 11 , further comprising:
A motion state quantity detection means for detecting an actual motion state quantity that is the same type as the calculated expected motion state quantity and represents the actual motion state of the vehicle;
A steering-by-wire type vehicle characterized by comprising correction means for correcting the calculated turning angle in accordance with a difference between the calculated expected motion state quantity and the detected actual motion state quantity. Steering device. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 12 ,
A steering-by-wire vehicle steering apparatus, comprising a reaction force device that applies a reaction force to the operation of the steering wheel.

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