JP4280669B2 - 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 for steering the vehicle.

  In recent years, the development of this type of steering-by-wire steering system 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, thereby dividing the front wheel A steering device is shown in which a turning angle (amount of rack shaft displacement) 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 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 device, the vehicle speed is also detected, and both turning angles are corrected based on the detected vehicle speed, so that 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 the detected steering angle and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, the steering control of these front wheels, although the mechanical connection between the conventional steering wheel and the steered wheels is removed, 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 due to the turning of the vehicle by touch or vision, and feeds back to the operation of the steering handle 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 that is 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.

  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. This is merely correction of the turning angle in consideration of the behavior state of the vehicle, and does not determine the turning angle according to the yaw rate that the driver will perceive by operating the steering wheel. Accordingly, 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.

  Further, in a steering-by-wire type steering apparatus such as the above-described conventional apparatus, application of reaction force to the steering wheel and turning of the steered wheels are controlled by an actuator. For this reason, the torque and the turning angle acting on the steering shaft may change due to the rotational speed of the steering wheel, the vehicle speed, or a disturbance input from the road, and the behavior of the vehicle may be disturbed along with this change. . This is considered to be because, for example, the current command value for the electric motor for driving the actuator is uniquely determined based on the torque acting on the steering shaft, the vehicle speed, and the like.

  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 a steering wheel operation 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 is changed exponentially or exponentially with respect to the human's manipulated variable, the relationship between the manipulated variable and the physical quantity can be matched to the human perceptual characteristics. it can. The present inventors have applied the Weber-Hefner's law to the steering operation of a vehicle and discovered the following.

  When driving a 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 the driver senses the motion state quantity of the vehicle. 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 facilitate steering of the vehicle by steering the vehicle in accordance with human perceptual characteristics and to obtain a vehicle behavior expected by the driver in a favorable manner. An object of the present invention is to provide a vehicle steering apparatus.

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. the anticipated motion state quantity of the vehicle, and motion state quantity calculating means that size in accordance with the operation input value is calculated by applying a hysteresis to be determined, it is the calculated The turning angle calculation means for calculating the turning angle of the steered wheels necessary for the vehicle to move with the expected movement state quantity using the calculated expected movement state quantity, and the calculated turning angle Accordingly, the steering actuator is configured to be configured with a steering control means that steers the steered wheel to the calculated steered angle.

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. When the operation input value detected by the operation input value detection means and the operation input value detection means is less than a predetermined value, the operation input value is calculated based on a predetermined relationship with respect to the operation input value. The operation force is applied to the steering wheel, and when the operation input value is greater than or equal to a predetermined value, the operation input value is calculated based on a predetermined exponent relationship and the operation input value is calculated. An operation input value converting means for converting an input value into an operation force applied to the steering handle, and an operation input value for the steering handle representing a motion state of the vehicle that can be perceived by the driver in relation to turning of the vehicle. Motion state quantity calculation for calculating a predicted motion state quantity of a vehicle having a predetermined exponential relationship or power relation with the operation input value converted by the operation input value conversion means by adding hysteresis to the operation force Means, a turning angle calculation means for calculating a 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, and There is also a configuration in which the turning actuator is controlled according to the calculated turning angle and the turning control means for turning the turning wheel to the calculated turning angle .

  In this case, the predetermined relationship with respect to the operation input value may include a relationship in which the operation force is approximately 0 when the detected operation input value is approximately 0. The predetermined relationship with respect to the operation input value and the predetermined relationship between the operation input value and the predetermined exponent may be continuously connected to each other at the predetermined value of the operation input value. Furthermore, the predetermined relationship with respect to the operation input value may be, for example, a proportional relationship in which the operation input value and the operation force are proportional.

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. Operation input value detection means, and operation determination means for determining a cutting operation in which the absolute value of the operation input value increases and a return operation in which the absolute value of the operation input value decreases with respect to the driver's operation on 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, and is an exponential relationship or a power that is predetermined with the operation input value to the steering wheel. When the change from the cutting operation to the returning operation is determined by the operation determining means, or when the change from the returning operation to the cutting operation is determined by the operation determining unit. In addition, the motion state quantity calculating means for calculating the operation input value by adding hysteresis, and the turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity, A turning angle calculation means for calculating using the calculated expected motion state quantity, and controlling the turning actuator according to the calculated turning angle to turn the turning wheel to the calculated turning angle. It is also composed of a steering control means for steering. Also, in this case, the operation discriminating unit, said return operation is set larger the discrimination predetermined value to determine the relative discriminating predetermined value for determining the turning operation, the turning operation or the returning operation It is good to discriminate.

  In these cases, the expected motion state quantity is, for example, any one of a lateral acceleration, a yaw rate, and a 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.

  Further, the operation input value detecting means may be constituted by a displacement amount sensor for detecting the displacement amount of the steering wheel, for example. The operation input value detection means may be constituted by an operation force sensor that detects and outputs an operation force input to the steering wheel, for example.

  In the present invention configured as described above, first, the operation input value of the driver with respect to the steering wheel represents the motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle. 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 power relationship with the value. At this time, the expected motion state quantity of the vehicle is calculated by adding a hysteresis characteristic to the operation input value. Then, based on the converted expected motion state quantity, the turning angle of the steered wheel necessary for the vehicle to move with the expected motion state quantity is calculated, and the steered wheel is added to the calculated turning angle. Steered. Therefore, when the vehicle turns by turning the steered wheels, the driver is given the expected motion state quantity as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. Since it changes exponentially or exponentially with respect to the operation input value, the driver can operate the steering wheel while perceiving the amount of motion state that matches human perception characteristics. 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.

  Also, hysteresis characteristics are given to the operation input value or the operation force converted from the operation input value, and the expected motion state quantity of the vehicle is calculated, for example, disturbance (for example, from the road surface via the steered wheels). Thus, even if the steering wheel is unintentionally turned by the driver due to the rotational force transmitted to the steering wheel, the amount of motion state expected by the driver is ensured. Thereby, since the state where the steered wheels are steered to the steered angle necessary for the vehicle to move with the expected motion state quantity is maintained, disturbance of the vehicle behavior can be satisfactorily suppressed.

  Further, the hysteresis level to be applied is determined according to the operation input value or the operation force converted from the operation input value, thereby providing an optimum hysteresis characteristic for the steering wheel operation of the driver. Can do. For this reason, the driver does not feel discomfort regarding the steering wheel operation or the vehicle behavior resulting from the steering wheel operation. Furthermore, it is possible to set a large predetermined determination value for determining the return operation with respect to the predetermined determination value for determining the cutting operation, and to discriminate between the cutting operation and the return operation and to provide hysteresis characteristics. Accordingly, for example, it is possible to suppress the frequent turning of the steering handle by the driver, more specifically, the frequent application of hysteresis characteristics accompanying the minute returning operation by the driver. Therefore, the driver does not feel discomfort due to frequent changes between the cutting operation and the returning operation.

  When the operation input value of the driver for the steering wheel is less than a predetermined value, the operation force (for example, steering torque) applied to the steering wheel is calculated based on a predetermined relationship with the operation input value. When the value is equal to or greater than the predetermined value, the operation force applied to the steering wheel is calculated based on the operation input value and a predetermined exponent relationship. In this calculation, the predetermined relationship with respect to the operation input value can include a relationship in which the operation force is approximately 0 when the detected operation input value is approximately 0. When the value is “0”, that is, when the steering wheel is in the neutral position, the operating force can be set to “0”.

  Thereby, for example, when the steering handle is rotated in the neutral position direction, the operation force can be uniformly converged to “0”, and vibration in the rotation direction near the neutral position is generated. Can be prevented. Further, by making the predetermined relationship with respect to the operation input value a proportional relationship in which the operation input value and the operation force are proportional, the operation force is continuously converged to “0” with respect to the operation input value. Can do. Furthermore, since the predetermined relationship with respect to the operation input value and the operation input value and the predetermined exponent relationship are continuously connected to each other at the predetermined value of the operation input value, these two relationships are set to the predetermined value. When switching between, it changes smoothly. As a result, the driver does not feel uncomfortable due to this switching.

  In addition, another feature of the present invention is that, in addition to the above-described configuration, the motion state quantity detection 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 wheel is steered more accurately to the steered angle necessary 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). ). 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 a program. 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 reaction force applied to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's perceptual 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 in the case where the absolute value of the detected steering angle θ is reduced (hereinafter referred to as the return operation), and the reaction force torque Tzr is calculated. Calculate

  Here, detection of the cutting operation and the return operation will be described. 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 rotated, 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 is being 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 wheel 11 is less than the positive predetermined value Tg, the displacement-torque converter 41 calculates and detects the reaction force torque Tzf, which is a linear function of the steering angle θ, according to the following equation 1. If the absolute value of the steering angle θ is equal to or greater than the positive predetermined value Tg, 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 is a linear function 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 value Tg. A certain reaction force torque Tzr is calculated. If the absolute value of the detected steering angle θ is equal to or greater than a predetermined positive value Tg, 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 thus calculated, 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. Further, 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, so that the turning amount of the steering handle 11 in the cutting operation and the steering handle in the returning operation are maintained. The amount of rotation of the steering wheel 11 can be made substantially the same, and in particular, the convergence of the steering wheel 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 the above formula 5. However, instead of or in addition to this, 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 torque Tzr for the return operation and the equation 1 for calculating the reaction force torque Tzf for the cutting operation are both functions that pass through the origin “0”, the returning operation (or the cutting operation) ) To a cutting operation (or return operation), the calculated reaction force torque Tzr and reaction force torque Tzf do not become discontinuous. Accordingly, 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. In the calculation of the reaction force torque Tzf or the reaction force torque Tzr, the characteristic conversion as shown in FIG. 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 inputs 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 the drive control of the electric motor in the reaction force actuator 13, the electric motor applies reaction force torque Tzf or reaction force torque Tzr to the steering handle 11 via the steering input shaft 12.

  Accordingly, for example, when the driver turns the steering handle 11 from the neutral position, the reaction torque Tzf that changes in a linear function calculated according to the above equation 1 is obtained when the detected steering angle θ is less than the steering angle θz. Further, when the detected steering angle θ is equal to or greater than the steering angle θz, the steering handle 11 is rotated 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 the steering position where the detected steering angle θ is equal to or larger 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 changes 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.

  Thus, 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, the hysteresis term Mh1 is calculated according to the equation 10 as in the calculation of the reaction force torques Tzf and Tzr described above, whereby the steering torque calculated according to the 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 equations 6 to 10, steering torques Tdf, Tdr are used by using a conversion table having characteristics as shown in FIG. 3 storing the steering torque Tdf and the steering torque Tdr with respect to the steering angle θ. 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 torque Tdf, 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 expected by the driver by the turning operation of the steering wheel 11 according to the following equations 11 and 12, and calculates the expected lateral acceleration Gdr 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 according to the 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 vehicle behavior 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 equations 11 and 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 that pass 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 to the left, the torque-lateral acceleration conversion unit 52 is linearly “0” according to the above 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−Mh), 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 expression 14 in the same manner as the modification from the expression 12 to the expression 16. 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 can be seen 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) (17)
However, K0 is a constant having a relationship of K0 = K1 · K2.

  Further, as shown in Expression 14, 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 Gd is calculated according to the above equations 11 and 13, whereby the steering handle 11 is When the vehicle is rotated in the direction, the expected lateral accelerations Gdf and Gdr converge to “0”, so 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 17 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 equations 1 to 17 are handled as the steering torque T and the lateral acceleration G. According to the aforementioned Weber-Hefner law, “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, in the above situation, the value of the ratio ΔT / T, that is, Weber, where T is the detected steering torque at a certain time and ΔT is the minimum amount of change in steering torque that can be perceived as a change from the detected steering torque T. 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, under the above situation, when F is the detection force that can withstand lateral force from the outside at a certain time and maintain the posture, and ΔF is the minimum force change amount that can perceive the change from the detection force F The ratio value ΔF / F, 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, they can be calculated using the differential value Δθ and 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 converters 41 and 51 and the torque-lateral acceleration converter 52, the reaction torques Tzf and Tzd, steering torques Tdf and Tdr that match the driver's perceptual characteristics are obtained 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 accelerations Gdf and 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 the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected lateral acceleration Gd, and changes according to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the target turning angle δd with respect to the expected lateral acceleration Gd. 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. Further, 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 turning angle conversion unit 53 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 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 a wheel base, and A is a predetermined value.

The calculated target turning angle δd 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 (28). The target turning angle δd input after execution is corrected, and the corrected target turning angle δda is calculated.
δda = δd + K3 · (Gd−G) Equation 28
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. The left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda by the displacement of the rack bar 24 in the axial direction.

  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 left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected lateral accelerations Gdf, Gdr by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62. . Thus, by providing the hysteresis terms Mh1 and Mh2, it is possible to provide hysteresis characteristics between the cutting operation and the returning operation, and for example, a disturbance (for example, transmitted from the road surface to the steering handle 11 via the steered wheels). The expected lateral accelerations Gdf and Gdr expected by the driver are ensured even when the steering handle 11 is unintentionally turned by the driver. This maintains the state in which the left and right front wheels FW1, FW2 are steered at the corrected target turning angle δda required for the vehicle to move with the expected lateral acceleration Gdf, Gdr, and thus suppresses disturbance in vehicle behavior. can do.

  In addition, since the hysteresis terms Mh1 and Mh2 are determined according to the steering torques Tdf and Tdr, optimum hysteresis characteristics can be given to the operation of the steering wheel 11 by the driver. For this reason, the driver does not feel discomfort regarding the operation of the steering handle 11 or the vehicle behavior resulting from the operation of the steering handle 11. Furthermore, it is possible to set the detection time for determining the return operation to be longer (longer) than the detection time for determining the cutting operation, and to distinguish between the cutting operation and the returning operation and to provide hysteresis characteristics. Thereby, for example, it is possible to suppress the frequent turning of the steering handle 11 by the driver, more specifically, the frequent application of the hysteresis characteristic accompanying the minute returning operation by the driver. Therefore, the driver does not feel discomfort due to frequent changes between the cutting operation and the returning operation.

  Further, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the above formulas 1 and 3 and the above formulas 6 and 8. It is possible to prevent the occurrence of vibration in the rotational direction near the neutral position of the handle 11, that is, when the steering angle θ is near “0”.

  Since the steering torque Td is equal to the reaction force torque Tz, the steering torque Td is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13 and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law. The actual lateral acceleration G generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the actual lateral acceleration G is controlled to be equal to the expected lateral acceleration Gd. Further, this expected lateral acceleration Gd is also a power function with respect to the steering torque Td calculated from the steering angle θ input by the driver (exponential function with respect to the steering angle θ by transforming Expression 12 into Expression 16). To change. Accordingly, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perceptual characteristic while feeling the lateral acceleration according to the Weber-Hefner law. 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.

  Next, a 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 this modified example, as indicated by a broken line in FIG. 1, the steering torque that is assembled to the steering input shaft 12 and input to the steering handle 11 is detected, and the detected steering torque is output as the steering torque T. A steering torque sensor 38 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 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 the displacement in the first embodiment. -Expected 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 torque converter 51. That is, the steering torque T output from the steering torque sensor 38 is output by executing the same calculation 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 this modification, the steering torque T as the driver's operation input value for the steering handle 11 is 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. The turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62 turn the left and right front wheels FW1 and FW2 to the corrected target turning angle δda necessary for generating the expected lateral accelerations Gdf and Gdr. In this case as well, 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 the Weber-Hefner's law and the steering wheel 11 according to the human perceptual characteristic. Can be rotated. Accordingly, 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 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 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 following equation 29 using the expected lateral acceleration Gd and the vehicle speed V.
γd = Gd / V Equation 29

Then, the corrected target turning angle δda is calculated based on the following equation 30 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 30
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. When the actual yaw rate γ exceeds the expected yaw rate γd, the absolute value of the corrected target turning angle δda is corrected. 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 Next, a second 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 second 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 second 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 this second 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 wheel 11 according to the following equations 31 and 32, and the expected yaw rate γdr that is expected by the return operation becomes the following equations 33, 34 according to the calculation. At this time, the torque-yaw rate converter 54 calculates the expected yaw rates γdf and γdr according to the following equations 31 and 33 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 32 and 34. Here, the following Expression 31 or Expression 33 is a linear function expression of the steering torque Td as in the first embodiment, and is a function in which the expected yaw rates γdf and γdr are “0” when the steering torque Td is “0”. is there. The following equations 32 and 34 are power functions of the steering torque Td as in the above embodiment, and are continuously connected to the following equations 31 and 33 at a predetermined value Tg.
γdf = b1 · Td (| Td | <Tg) Equation 31
γdf = C · Td ^K2 (Tg ≦ | Td |) Equation 32
γdr = b2 · Td−Mh2 (| Td | <Tg) Equation 33
γdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 34
However, b1 in the equation 31 and b2 in the equation 33 are constants representing the slope of a linear function, and C and K2 in the equations 32 and 34 are constants. Further, the steering torque Td in the equations 31 to 34 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

Mh2 in the above formulas 33 and 34 continuously connects the estimated yaw rate γdf and the expected yaw rate γdr calculated 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 Expression 35.
Mh2 = nq · (Kq · Td) Equation 35
In Equation 35, Kq is the 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 above Expression 35, 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 yaw rate γdf calculated according to the equation 31 or 32 and the expected yaw rate γdr calculated according to the equation 33 or 34 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 35, the expected yaw rates γdf and γdr 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 yaw rates γdf and γdr are actually rotated by a disturbance input from the road, for example. 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 31 and 33, so that the steering handle 11 is rotated across the neutral position. Even in this case, since the equation 31 and the equation 33 are functions passing through the origin “0”, the expected yaw rate γdf and the expected yaw rate γdr are prevented from becoming discontinuous.

  In other words, when the value is less than the predetermined value Tg, both the formula 31 and the formula 33 are functions that pass through the origin “0”. For this reason, if the driver expects the expected yaw rate, for example, the yaw rate changing from the right direction to the left direction, the torque-lateral acceleration conversion unit 52 converges to “0” in a linear function according to the equation 33. The expected yaw rate γdr is calculated, and the expected yaw rate γdf that increases linearly from “0” according to the equation 31 is calculated. Therefore, the expected yaw rate γdf and the expected yaw rate γdr are continuous at “0”, and when the perceived direction of the expected yaw rate changes, in other words, even when the detected steering angle θ reverses positive and negative, the expected yaw rate γdf, γdr can be switched, and the driver does not feel uncomfortable. Also in this case, instead of the calculations of the above equations 31 to 35, the expected yaw rates γdf and γdr are calculated using the conversion table having the characteristics as shown in FIG. 4 in which the expected yaw rates γdf and γdr with respect to the steering torque Td are stored. 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 of the left and right front wheels FW1 and FW2 necessary to generate the expected yaw rate γd, and changes according to the vehicle speed V as shown in FIG. A table representing a change characteristic of the target turning angle δd with respect to the expected yaw rate γd; This table is a set of data collected by actually measuring the turning angle δ and the yaw rate γ of the left and right front wheels FW1 and FW2 while running the vehicle while changing the vehicle speed V. 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. The yaw rate γ (estimated 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 converter 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 equation 36, it can be calculated by executing the calculation of the following equation 36 instead of referring to the table. .
δd = L · (1 + A · V ² ) · γd / V Equation 36
However, also in the equation 36, L is a predetermined value indicating the wheel base, and A is a predetermined value.

The calculated target turning angle δd 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 Expression 37. The corrected target turning angle δda is calculated by correcting the input target turning angle δd.
δda = δd + K5 · (γd−γ) Equation 37
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. When the actual yaw rate γ exceeds the expected yaw rate γd, the absolute value of the corrected target turning angle δda is corrected. 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. 6, the same reference numerals as those in FIG. 2 of the first embodiment are given, and the description thereof is omitted.

  Also in the second 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. In addition, the yaw rate γdf or the yaw rate γdr to which the hysteresis term Mh2 is added is converted. Then, the left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δda necessary for generating the expected yaw rates γdf and γdr by the turning angle conversion unit 55, the turning angle correction unit 63, and the drive control unit 62. In this way, by providing the hysteresis terms Mh1 and Mh2, it is possible to provide hysteresis characteristics between the cutting operation and the returning operation. For example, disturbance (for example, transmitted from the road surface to the steering handle 11 via the steered wheels). The expected yaw rates γdf and γdr expected by the driver are secured even if the steering handle 11 is unintentionally turned by the driver. This maintains the state in which the left and right front wheels FW1 and FW2 are steered at the corrected target turning angle δda necessary for the vehicle to move at the expected yaw rates γdf and γdr, and thus suppresses the disturbance of the vehicle behavior. be able to.

  In addition, since the hysteresis terms Mh1 and Mh2 are determined according to the steering torques Tdf and Tdr, optimum hysteresis characteristics can be given to the operation of the steering wheel 11 by the driver. For this reason, the driver does not feel discomfort regarding the operation of the steering handle 11 or the vehicle behavior resulting from the operation of the steering handle 11. Furthermore, it is possible to set the detection time for determining the return operation to be longer (longer) than the detection time for determining the cutting operation, and to distinguish between the cutting operation and the returning operation and to provide hysteresis characteristics. Thereby, for example, it is possible to suppress the frequent turning of the steering handle 11 by the driver, more specifically, the frequent application of the hysteresis characteristic accompanying the minute returning operation by the driver. Therefore, the driver does not feel discomfort due to frequent changes between the cutting operation and the returning operation.

  Also in this case, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the equations 1 and 3, so that the steering handle 11 is neutral. It is possible to prevent the occurrence of vibration in the rotation direction near the position, that is, when the steering angle θ is near “0”.

  Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and is exponential with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the yaw rate γ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the yaw rate γ is controlled to be equal to the expected yaw rate γd. A power function with respect to the steering torque Td calculated from θ (exponential function with respect to the steering angle θ by modifying the equations 32 and 34 in the same manner as the transformation from the equation 12 to the equation 16 in the first embodiment). ). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

  Further, the turning angle correction unit 63 generates an actual yaw rate γ in which the actual yaw rate γ actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11. As a result, the driver can operate the steering wheel 11 while perceiving a yaw rate that more accurately matches the human perceptual characteristics, so that the vehicle can be driven more easily. Further, the specific effects are the same except that the lateral acceleration of the first embodiment is changed to the yaw rate.

  In the second embodiment, as in the case of the first embodiment, the steering torque T can be used as the operation input value of the steering handle 11. Also in this modified example, as indicated by a broken line in FIG. 1, a steering torque sensor 38 that is assembled to the steering input shaft 12 and outputs the steering torque input to the steering handle 11 as the steering torque T is provided. Then, the displacement-torque converter 51 is omitted, and the torque-yaw rate converter 54 replaces the steering torques Tdf and Tdr calculated by the displacement-torque converter 51 with the steering torque detected by the steering torque sensor 38. The expected yaw rate γdf or the yaw rate γdr with the hysteresis term Mh2 is calculated using T. That is, the steering torque T output from the steering torque sensor 38 is output by executing the same calculation 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 ˜35 is executed to determine the expected yaw rates γdf and γdr. In this case as well, the expected yaw rates γdf and γdr 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 second embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected yaw rates γdf and γdr by the torque-yaw rate conversion unit 54, and the turning angle conversion unit 55 and the turning angle correction are performed. The left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected yaw rate γd by the unit 63 and the drive control unit 62. At this time, the output steering torque T is output by executing the same calculation as in the equations 6 to 10 with respect to the input steering torque. Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected yaw rates γdf and γdr with respect to the steering torque T are exponential functions (from Equation 12 in the first embodiment). The driver changes according to human perceptual characteristics while feeling a reaction force according to Weber-Hefner's law. The steering handle 11 can be turned. Therefore, also in this modified example, as in the case of the second embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the yaw rate according to the Weber-Hefner's law. Therefore, the same effect as in the case of the second embodiment can be expected.

  Furthermore, the vehicle steering control according to the second embodiment and the vehicle steering control according to the modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 38 are provided, and the estimated yaw rate γd is calculated using the target steering torque Td calculated by the displacement-torque conversion unit 51 as in the second embodiment. It is also possible to switch between the case where the expected yaw rate γd 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 second embodiment, the turning angle correction unit 63 corrects the target turning angle δd according to the difference γd−γ between the expected yaw rate γd and the actual yaw rate γ. However, instead of or in addition to this, the turning angle correction unit 61 corrects the target turning angle δd according to the difference Gd−G between the expected lateral acceleration Gd corresponding to the expected yaw rate γd and the actual lateral acceleration G. You may do it. In this case, the expected lateral acceleration Gd is calculated by the following equation 38 using the expected yaw rate γd and the vehicle speed V.
Gd = γd · V Equation 38

Then, the corrected target turning angle δda is calculated based on the following equation 39 using the calculated expected lateral acceleration Gd and the actual lateral acceleration G detected by the newly provided lateral acceleration sensor 34 (see FIG. 1). You just have to do it.
δda = δd + K6 (Gd−G) Equation 39
However, the coefficient K6 is a predetermined positive constant, and when the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K6 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.

c. Third Embodiment Next, a third 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 third 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 third 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 third embodiment as well, the torque-curvature conversion unit 56 executes the calculation described later in the same manner regardless of the steering torques Tdf and 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 40 and 41, and calculates the expected turning curvature ρdr expected by the return operation by the following formulas 42 and 43. 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 40 and 42 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 equal to or greater than a predetermined positive value Tg, the calculation is performed according to the following equations 41 and 43. Here, the following equation 40 or equation 42 is a linear function equation of the steering torque Td as in the first embodiment, and the functions of the expected turning curvatures ρdf and ρdr are “0” when the steering torque Td is “0”. It is. The following formulas 41 and 43 are power functions of the steering torque Td as in the above embodiment, and are continuously connected to the following formulas 40 and 42 at a predetermined value Tg.
ρdf = b1 · Td (| Td | <Tg) Equation 40
ρdf = C · Td ^K2 (Tg ≦ | Td |) Equation 41
ρdr = b2 · Td−Mh2 (| Td | <Tg) Equation 42
ρdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 43
However, b1 in the equation 40 and b2 in the equation 42 are constants representing the slope of a linear function, and C and K2 in the equations 41 and 43 are constants. Further, the steering torque Td in the equations 40 to 43 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

In addition, Mh2 in the formulas 42 and 43 is obtained by continuously calculating the expected turning curvature ρdf and the expected turning curvature ρdr 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 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 44. The
Mh2 = nq · (Kq · Td) ... Formula 44
In Equation 44, Kq is the 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 44, but 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 thus calculated, the expected turning curvature ρdf calculated according to the equation 40 or 41 and the expected turning curvature ρdr calculated according to the equation 42 or 43 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 44, the expected turning curvatures ρdf and ρdr 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 turning curvatures ρdf and ρdr 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 vehicle behavior 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 in accordance with the formula 40 and the formula 42, whereby the steering handle 11 is turned over the neutral position. Even in this case, since the expression 40 and the expression 42 are functions passing through the origin “0”, the expected turning curvature ρdf and the expected turning curvature ρdr are prevented from becoming discontinuous.

  In other words, when the value is less than the predetermined value Tg, both the formula 40 and the formula 42 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 changes to “0” according to the equation 42. The convergent expected turning curvature ρdr is calculated, and the expected turning curvature ρdf that increases linearly from “0” according to the above equation 40 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 40 to 44, the expected turning curvature ρdf, using the conversion table having the characteristics as shown in FIG. 4 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 changes according to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the target turning angle δd with respect to the expected turning curvature ρd. 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 converter 57 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 with reference to this table. The turning curvature ρ (expected turning curvature ρd) and the target turning angle δd stored in the table are both positive, but the expected lateral acceleration γd 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 formula 45, it can be calculated by executing the calculation of the following formula 45 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 45
However, also in the formula 45, L is a predetermined value indicating the wheel base, and A is a predetermined value.

The calculated target turning angle δd 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 46 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 46

And the turning angle correction | amendment part 64 performs the calculation of following formula 47, correct | amends the input target turning angle (delta) d, and calculates corrected target turning angle (delta) da.
δda = δd + K7 · (ρd−ρ) Equation 47
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. In the functional block diagram of FIG. 9, the same reference numerals as those in FIG. 2 of the first embodiment are given, and the description thereof is omitted.

  Also in the third 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 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 left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δda necessary for generating the expected turning curvatures ρdf and ρdr by the turning angle conversion unit 57, the turning angle correction unit 64, and the drive control unit 62. . In this way, by providing the hysteresis terms Mh1 and Mh2, it is possible to provide hysteresis characteristics between the cutting operation and the returning operation. For example, disturbance (for example, transmitted from the road surface to the steering handle 11 via the steered wheels). Even when the steering handle 11 is unintentionally turned by the driver, the expected turning curvatures ρdf and ρdr expected by the driver are ensured. As a result, the state in which the left and right front wheels FW1, FW2 are steered at the corrected target turning angle δda necessary for the vehicle to move with the expected turning curvatures ρdf, ρdr is maintained, so that the disturbance of the vehicle behavior is well suppressed. can do.

  In addition, since the hysteresis terms Mh1 and Mh2 are determined according to the steering torques Tdf and Tdr, optimum hysteresis characteristics can be given to the operation of the steering wheel 11 by the driver. For this reason, the driver does not feel discomfort regarding the operation of the steering handle 11 or the vehicle behavior resulting from the operation of the steering handle 11. Furthermore, it is possible to set the detection time for determining the return operation to be longer (longer) than the detection time for determining the cutting operation, and to distinguish between the cutting operation and the returning operation and to provide hysteresis characteristics. Thereby, for example, it is possible to suppress the frequent turning of the steering handle 11 by the driver, more specifically, the frequent application of the hysteresis characteristic accompanying the minute returning operation by the driver. Therefore, the driver does not feel discomfort due to frequent changes between the cutting operation and the returning operation.

  Further, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the above formulas 1 and 3, so the vicinity of the neutral position of the steering handle 11 That is, it is possible to prevent the occurrence of vibration in the rotation direction when the steering angle θ is near “0”.

  Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and is exponential with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the turning curvature ρ generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the turning curvature ρ is controlled to be equal to the expected turning curvature ρd. ρd is also a power function with respect to the steering torque Td calculated from the steering angle θ (similar to the transformation from the formula 12 to the formula 16 in the first embodiment, the formulas 41 and 43 are transformed to the steering angle θ. Change exponentially). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

  Further, the turning angle correction unit 64 turns with an actual turning curvature ρ in which the actual turning curvature ρ actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11. As a result, the driver can operate the steering wheel 11 while perceiving a turning curvature that more accurately matches the human perceptual characteristics, and thus the driving of the vehicle is further simplified. Further, the specific effects are the same except that the lateral acceleration of the first embodiment is changed to the yaw rate.

  In the third embodiment, as in the case of the first embodiment, the steering torque T can be used as the operation input value of the steering handle 11. Also in this modified example, as indicated by a broken line in FIG. 1, a steering torque sensor 38 that is assembled to the steering input shaft 12 and outputs the steering torque input to the steering handle 11 as the steering torque T is provided. Then, the displacement-torque converter 51 is omitted, and the torque-curvature converter 56 replaces the steering torques Tdf and Tdr calculated by the displacement-torque converter 51 with the steering torque output by the steering torque sensor 38. Expected turning curvatures ρdf and ρdr are calculated by executing the operations of the above-described equations 40 to 44 using T. That is, the steering torque T output from the steering torque sensor 38 is output by executing the same calculation 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 ˜44 is executed to determine the expected turning curvatures ρdf and ρdr. In this case as well, the expected turning curvatures ρdf and ρdr 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 third embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected turning curvatures ρdf and ρdr by the torque-curvature conversion unit 56, and the turning angle conversion unit 57 and the turning angle are converted. By the correction unit 64 and the drive control unit 62, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected turning curvature ρd. Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected turning curvature ρd with respect to the steering torque T is a power function (from the expression 12 in the first embodiment). This is a more exponential change that transforms Equations 41 and 43 as well as the transformation to 16, so that the driver can steer according to human perceptual characteristics while feeling the reaction force according to Weber-Hefner's law The handle 11 can be rotated. Therefore, also in this modified example, as in the case of the third embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the turning curvature according to the Weber-Hefner's law. Since the vehicle can be turned, the same effect as in the case of the third embodiment is expected.

  Furthermore, the vehicle steering control according to the third embodiment and the vehicle steering control according to the modification may be switchable. That is, when both the steering angle sensor 31 and the steering torque sensor 38 are provided and the expected turning curvature ρd is calculated using the target steering torque Td calculated by the displacement-torque converter 51 as in the third embodiment. It is also possible to switch between using the steering torque T output by the steering torque sensor 38 and calculating the expected turning curvature ρd. 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 third embodiment, the turning angle correction unit 64 corrects the target turning angle δd according to the difference ρd−ρ between the expected turning curvature ρd and the actual turning curvature ρ. However, instead of or in addition to this, as in the case of the first embodiment, the turning angle correction unit 61 determines that the difference Gd− between the expected lateral acceleration Gd and the actual lateral acceleration G corresponding to the expected turning curvature ρ. The target turning angle δd may be corrected according to G. In this case, the expected lateral acceleration Gd is calculated by the following equation 48 using the expected turning curvature ρd and the vehicle speed V.
Gd = ρd · V ² Formula 48

Similarly to the case of the second embodiment, the turning angle correction unit 61 sets the target turning angle δd according to the difference γd−γ between the expected yaw rate γd corresponding to the expected turning curvature ρ and the actual yaw rate γ. You may make it correct | amend. In this case, the expected yaw rate γd is calculated by the following equation 49 using the expected turning curvature ρd and the vehicle speed V.
γd = ρd · V Equation 49

d. Other Modifications Furthermore, the implementation of the present invention is not limited to the first to third embodiments and their modifications, and various modifications can be made without departing from the object of the present invention. .

  For example, in the first to third 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 third 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 third embodiments and the modifications thereof, the lateral acceleration, the yaw rate, and the turning curvature are each independently used as the vehicle motion state quantity 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. FIG. 9 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the second 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 the third 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 (12)

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;
A vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and an operation input value for the steering handle and a predicted motion state amount of the vehicle that is in a predetermined exponential relationship or a power relationship with the operation input value. A motion state quantity calculating means for calculating by adding a hysteresis whose size is determined according to a value;
A turning angle calculation means for calculating a 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;
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;
With respect to the driver's operation on the steering wheel, an operation determination means for determining a cutting operation in which the absolute value of the operation input value increases and a return operation in which the absolute value of the operation input value decreases;
The operation determination represents 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 has a predetermined exponential relationship or a power relationship with the operation input value to the steering wheel. When a change from the cutting operation to the returning operation is determined by the means, or when a change from the returning operation to the cutting operation is determined, a hysteresis is applied to the operation input value. A motion state quantity calculating means for calculating;
A turning angle calculation means for calculating a 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;
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. In the steering device for a steering-by-wire vehicle according to claim 2 ,
The operation determining means sets the determination predetermined value for determining the return operation larger than the determination predetermined value for determining the cutting operation, and determines the cutting operation or the returning operation. A steering-by-wire vehicle steering apparatus. 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;
When the operation input value detected by the operation input value detection means is less than a predetermined value, the operation input value is calculated based on a predetermined relationship and the operation input value is given to the steering wheel. When the operation input value is equal to or greater than a predetermined value, the operation input value is calculated based on a predetermined exponential relationship and the operation input value is converted into an operation force applied to the steering wheel. Operation input value conversion means to perform,
A vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and an operation input value for the steering handle and a predicted motion state amount of the vehicle that is in a predetermined exponential relationship or a power relationship with the operation input value. An exercise state quantity calculating means for applying a hysteresis to the operation force converted from the operation input value by the value converting means,
A turning angle calculation means for calculating a 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;
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. In the steering device for a steering-by-wire vehicle according to claim 4 ,
The steering-by-wire vehicle steering apparatus according to claim 1, wherein the predetermined relationship with respect to the operation input value includes a relationship in which the operation force is approximately 0 when the detected operation input value is approximately 0. In the steering device for a steering-by-wire vehicle according to claim 4 or 5 ,
The steering-by-wire system is characterized in that the predetermined relationship with respect to the operation input value and the operation input value and the predetermined exponent relationship are continuously connected to each other at the predetermined value of the operation input value. Vehicle steering device. In the steering device for a steering-by-wire vehicle according to any one of claims 4 to 6 ,
The steering-by-wire vehicle steering apparatus according to claim 1, wherein the predetermined relationship with respect to the operation input value is a proportional relationship in which the operation input value and the operation force are proportional. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 7 ,
A steering-by-wire vehicle steering apparatus in which the operation input value detection means is constituted by a displacement amount sensor that detects a displacement amount of the steering wheel. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 3 ,
A steering-by-wire type vehicle steering apparatus in which the operation input value detecting means includes an operation force sensor that detects and outputs an operation force input to the steering wheel. The steering device for a steering-by-wire vehicle according to any one of claims 1 to 9 ,
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 10 , 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. The steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 11 , further comprising:
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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