JP4456018B2 - Vehicle steering device - Google Patents

Description

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

  In recent years, the development of this type of steering-by-wire steering apparatus has been actively carried out. For example, Patent Document 1 below detects a steering angle and a vehicle speed, calculates a transmission ratio that decreases as the steering angle increases and increases as the vehicle speed increases, and divides the steering angle by this transmission ratio, 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 wheel angle, and correcting the calculated turning angle according to the difference between the calculated target yaw rate and the detected actual yaw rate, the vehicle behavior state Steering control that takes into account is also realized.

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

  However, in any of the above conventional devices, the steering angle and the steering torque, which are the operation input values for the steering wheel by the driver for steering the vehicle, are detected, and the front wheels are detected using these detected steering angles and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, 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 Therefore, the driver felt uncomfortable and it was difficult to drive the vehicle.

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

  In any of the above-described conventional devices, the front wheel is steered to the determined steered angle by driving the steered actuator according to the detected steering angle. At this time, humans cannot perceive the speed at which the front wheels are steered to the steered angle determined by the driving of the steered actuator, that is, the steered angular speed obtained by time differentiation of the steered angle. It is a physical quantity. Therefore, by setting the turning angular speed to be large, the steering response of the front wheels to the steering wheel operation by the driver becomes good.For example, when driving at high speed, the steering wheel is suddenly operated by the driver. Thus, the turning behavior of the vehicle may become unstable, which may make it difficult to drive the vehicle.

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

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

  The present invention is based on the above discovery, and its purpose is to turn the vehicle in accordance with human perception characteristics in response to the operation of the steering wheel by the driver and to prevent a sudden change in the turning behavior of the vehicle. Another object of the present invention is to provide a vehicle steering apparatus that facilitates driving of the vehicle.

  In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. A steering-by-wire vehicle steering apparatus comprising: a steering control device that drives and controls the steering actuator to steer the steered wheels; and the steering control device is operated by a driver's operation input to the steering handle. An operation input value detecting means for detecting a value and a vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and is in a predetermined exponential relationship or a power relationship with the operation input value for the steering wheel. A motion state quantity calculating means for calculating a predicted motion state quantity of the vehicle using the detected operation input value, and the vehicle moves with the calculated expected motion state quantity. A turning angle calculation means for calculating a target turning angle of the steered wheel necessary for the purpose using the calculated expected motion state quantity, and the steered wheel steers to the calculated target turning angle. A turning angular speed limiting means for limiting a turning angular speed of the steered wheels in a changing process to be equal to or less than a maximum turning angular speed at which the vehicle can stably turn, and the calculated target turning angle and the maximum turning angle. The present invention resides in that the steering actuator is configured to control the steering actuator according to the steering angular speed and to steer the steered wheel to the calculated target steered angle.

  In this case, the turning angle speed limiting means calculates a restricted turning angle for limiting the turning angular speed of the steered wheels in the changing process using the maximum turning angular speed. And the absolute value of the transient turning angle in the changing process sequentially calculated by the turning angle calculation means and the absolute value of the limited turning angle calculated by the restriction turning angle calculation means. If the absolute value of the transitional turning angle is larger than the absolute value of the limited turning angle, the target control turning angle for controlling the turning of the steered wheels in the changing process using the limited turning angle. And determining the transitional turning angle as the target control turning angle if the absolute value of the transient turning angle is equal to or smaller than the absolute value of the limit turning angle. It is good to comprise with a determination means.

  Further, in this case, when the steered control device further shifts from the changing process to the maintaining process maintained at the target steered angle by the steered wheels being steered by the steered control means. Or, when shifting from the maintenance process to the change process, provided is a filter processing means for filtering the change of the turning angle of the steered wheels in the change process with respect to time and gradually changing the turning angle. It is good to configure. Here, for example, when the difference between the absolute value of the turning angle of the steered wheel and the absolute value of the target turning angle in the changing process is less than a predetermined value, the filter processing means performs the filtering process. Execute.

  Further, in this case, the expected motion state quantity is, for example, 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 handle may be further provided.

  Further, the operation input value detecting means can be constituted by, for example, a displacement amount sensor for detecting the displacement amount of the steering handle. In this case, the motion state amount calculating means gives the detected displacement amount to the steering handle. It is good to comprise by the operation force conversion means which converts into the operation force to be performed, and the movement state amount conversion means which converts the converted operation force into the expected movement state amount.

  Further, the operation input value detection means can be constituted by, for example, an operation force sensor that detects an operation force applied to the steering wheel. In this case, the motion state quantity calculation means is the detected operation force. It is good to comprise with the exercise state quantity conversion means which converts into the said estimated exercise state quantity. Then, the motion state quantity conversion means may convert the operating force into a predicted motion state quantity that is in a power relation with the operating force.

  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. Then, based on the converted expected motion state quantity, a target turning angle of a steered wheel necessary for the vehicle to move with the expected motion state quantity is calculated, and the calculated turning angle is converted to the calculated target turning angle. The steering wheel is 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 the expected motion state quantity changes exponentially or exponentially with respect to the operation input value to the steering wheel, the driver perceives the motion state quantity that matches human perception characteristics. While the steering wheel can be operated. The lateral acceleration and yaw rate can be sensed tactilely by the driver in contact with each part in the vehicle. Further, the turning curvature can be visually perceived by the driver due to changes in the situation within the field of view of the vehicle. As a result, according to the present invention, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

  Further, in the present invention configured as described above, the steered actuator is driven and controlled so that the steered wheels are steered to the calculated target steered angle. More specifically, the steered wheel is driven and controlled so that the steered actuator has a target steered angle required for the vehicle to move with an expected motion state quantity that is exponentially or exponentially related to an operation input value to the steering wheel. Is steered. Therefore, the target turning angle is also calculated with an exponential relationship or a power relationship with respect to the operation input value for the steering wheel. Thereby, for example, when a large operation input value is input by the driver, the change in the target turning angle with respect to the change in the operation input value becomes large, the turning behavior of the vehicle changes suddenly, and the steering stability deteriorates. It is possible. However, the turning angular speed when the steered wheels are steered by driving the steering actuator (for example, the turning angular speed obtained by differentiating the turning angle with respect to time) is the maximum turning speed at which the vehicle can stably turn. Since the speed is limited to the steering angular speed or less, the steered wheels can be prevented from turning suddenly. Therefore, the vehicle can always be turned with a stable turning behavior in response to the operation of the steering wheel by the driver, and the driver can perceive good steering stability.

  More specifically, in the changing process in which the steered wheels are steered to the target steered angle, the absolute value of the transient steered angle that changes exponentially or exponentially to the target steered angle, and the maximum The absolute value of the limited turning angle calculated using the turning angular speed of If the absolute value of the transient turning angle is larger than the absolute value of the limited turning angle, the turning behavior of the vehicle is abruptly disturbed by turning the steered wheels to the limiting turning angle in the changing process. This can be prevented. At this time, since the steered wheels are steered at the maximum steered angular speed at which the vehicle can turn stably, the steerable response to the driver's steering wheel operation can be ensured satisfactorily. On the other hand, if the absolute value of the transitional turning angle is less than or equal to the absolute value of the limit turning angle, stable turning behavior of the vehicle can be achieved by turning the steered wheels to the transitional turning angle in the course of change. Can be ensured, and the steering wheel can be operated while perceiving an amount of motion state that matches human perception characteristics. Therefore, the driver can drive the vehicle without worrying that the turning behavior of the vehicle becomes unstable when operating the steering wheel, that is, turning the vehicle.

  Further, in the present invention configured as described above, when the turning state of the steered wheels shifts from the changing process to the maintaining process or from the maintaining process to the changing process, in particular, the absolute value of the current steered wheel turning angle. When the difference between the absolute value of the target turning angle and the target turning angle is less than a predetermined value, the turning angle of the steered wheels in the changing process is filtered. For this reason, the transition of the steered state of the steered wheels can be performed extremely smoothly. Accordingly, it is possible to effectively prevent a sudden transition from the change process (the steered wheel steering operation state) to the maintenance process (the steered wheel steer stop state) or the maintenance process to the change process. For this reason, generation | occurrence | production of the unnecessary yaw rate accompanying the transition of the steered state of a steered wheel can be prevented. Therefore, the driver can drive the vehicle without worrying about the unstable turning behavior of the vehicle, so that the driving of the vehicle is simplified.

  Hereinafter, a vehicle steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vehicle steering apparatus according to this 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, a lateral acceleration sensor 34, and a yaw rate sensor 35.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ) Is output. Note that the steering angle θ and the actual turning angle δ are expressed by setting the neutral position of the steering wheel 11 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 yaw rate sensor 35 detects and outputs the actual yaw rate γ of the vehicle. Note that the actual lateral acceleration G and the actual yaw rate γ also represent the leftward acceleration as positive and the rightward acceleration as negative.

  These sensors 31 to 35 are connected to the electronic control unit 36. The electronic control unit 36 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operations of the reaction force actuator 13 and the turning actuator 21 by executing programs. Drive circuits 37 and 38 for driving the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 36, respectively. In the drive circuits 37 and 38, current detectors 37a and 38a for detecting a drive current flowing in the electric motors in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 37a and 38a is fed back to the electronic control unit 36 in order to control the drive of both electric motors.

  Next, the operation of the embodiment configured as described above will be described with reference to the functional block diagram of FIG. 2 showing the functions realized by computer program processing in the electronic control unit 36. The electronic control unit 36 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 calculating a target turning angle δro and correcting the target turning angle δro to determine a corrected target turning angle δd, and a maximum turning angular velocity at which the vehicle can stably turn. Based on the left and right front wheels FW1 and FW2, the steering control unit 60 controls the steering.

  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. Is calculated, the target reaction force torque Thf is calculated, and the target reaction force is calculated when a rotation operation in which the absolute value of the detected steering angle θ is reduced (hereinafter, this rotation operation is referred to as a return operation). Calculate the torque Thr. In the following description, these target reaction torques Thf and Thr are collectively referred to simply as target reaction torque Th.

  Here, the detection of the cutting operation and the return operation will be described. Now, considering the case where the steering handle 11 is turned rightward, the detected steering angle θ output from the steering angle sensor 31 is a negative value. In this state, when the steering handle 11 is rotated, if the time differential value dθ / dt of the detected steering angle θ is a negative value, it is detected that the driver has made a cutting operation, and the time differential value dθ If / dt 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 rotated, if the time differential value dθ / dt is a positive value, it is detected that the driver has performed a cutting operation, and the time differential value dθ / dt is If the value is negative, it is detected that the driver has performed a return operation.

  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 these operations are detected at the same time that the driver performs a cutting operation or a return operation, 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, frequent switching of the calculation process causes a problem that, for example, the reaction force perceived by the driver via the steering wheel 11 varies greatly.

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

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

  Here, a1 in the formula 1 and a2 in the formula 3 are constants representing the slope of the linear function described above. In addition, To and K1 in the equations 2 and 4 are both constants. In particular, the constant To is the minimum steering torque that can be perceived by the driver. The constant K1 will be described in detail when explaining the sensory adaptation control unit 50 described later. Further, the steering angle θ in the equations 1 to 4 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constants a1 and a2 and the constant To are set to negative values. In addition, 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, it is a hysteresis term for configuring a hysteresis characteristic between the cutting operation and the returning operation. The hysteresis term Mh1 is determined based on the ratio of the reaction force torque Tzf at the time of the cutting operation and the reaction force torque Tzr at the time of the return operation at the time when a certain steering angle θ is detected, and is expressed as the following Expression 5. .
Mh1 = np · (Kp · Tzf) ... Formula 5
In Equation 5, Kp is a minimum change sensitivity with respect to the reaction force torque Tzf (corresponding to a Weber ratio related to torque described later), and np is a predetermined coefficient for the minimum change sensitivity.

  Thus, by calculating the hysteresis term Mh1, the steering angle θ at the time when the cutting operation is changed to the returning operation is maintained. For this reason, the turning amount of the steering handle 11 in the cutting operation and the turning amount of the steering handle 11 in the returning operation can be made substantially the same, and in particular, the convergence of the steering handle 11 during the returning operation can be ensured satisfactorily. it can. In the present embodiment, the hysteresis term Mh1 is derived so as not to include the steering angle θ as shown in the formula 5, but instead of or in addition to this, for example, including 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 or the reaction force torque Tzr is calculated according to the equation 1 or the equation 3. As a result, even when the steering handle 11 is rotated across the neutral position, since the equation 1 or the equation 3 is a function passing through the origin “0”, the reaction force torque Tzf and the reaction force Torque Tzr changes continuously. 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 the neutral position, the leftward cutting operation is performed, so that the displacement-torque conversion unit 41 changes from “0” to a linear function according to the above equation 1. Calculate the 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 change continuously. Accordingly, even when the steering handle 11 is turned over the neutral position, in other words, even when the detected steering angle θ is reversed, the reaction force torques Tzf and Tzr are applied to the steering handle 11 very smoothly. It can be granted and the driver does not feel uncomfortable. In the calculation of the reaction force torque Tzf or the reaction force torque Tzr, a characteristic conversion table as shown in FIG. 3 in which the reaction force torques Tzf and Tzr with respect to the steering angle θ are stored in place of the calculations of the above equations 1-5. You may make it calculate using. In the following description, reaction force torque Tzf and reaction force torque Tzr are collectively referred to as reaction force torque Tz.

  The reaction force torque Tz calculated in this way is supplied to the torque addition unit 42. The torque addition unit 42 adds the other reaction force torque input from the steering system to the supplied reaction force torque Tz, and obtains the target reaction force torque Th that the driver perceives via the steering handle 11. calculate. Therefore, the torque adding unit 42 is calculated from the steering angular velocity-friction torque converting unit 43, the steering angular velocity-viscosity torque converting unit 44, and the yaw rate-self-alignment torque converting unit 45 (hereinafter referred to as the yaw rate-SAT converting unit 45). Input the reaction torque. In addition, since the calculation method of each reaction force torque which each of these conversion parts 43,44,45 calculates is not directly related to this invention, the detailed description is abbreviate | omitted and it demonstrates easily below.

  The steering angular velocity-friction torque converter 43 calculates a friction torque Mtdnw caused by friction between the steering handle 11 and another member (for example, a steering column). This friction torque Mtdnw is the magnitude of the rotational operation speed of the steering wheel 11 by the driver, that is, the time differential value dθ / dt of the detected steering angle θ (hereinafter, this time differential value dθ / dt is referred to as the steering angular velocity dθ / dt). And is calculated with hysteresis characteristics. Therefore, the friction torque Mtdnw with respect to the steering angular velocity dθ / dt is calculated using a conversion table having characteristics as shown in FIG. The steering angular velocity-viscous torque converter 44 calculates a viscous torque Mtd that is generated when the steering handle 11 is turned. This viscous torque Mtd is calculated in proportion to the steering angular velocity dθ / dt. Therefore, the viscous torque Mtd with respect to the steering angular velocity dθ / dt is calculated using a conversion table having characteristics as shown in FIG. Further, the yaw rate-SAT conversion unit 45 calculates the self-alignment torque Msat input to the steering wheel 11 due to the friction between the left and right front wheels FW1, FW2 and the road surface. The yaw rate-SAT conversion unit 45 inputs the actual yaw rate γ detected by the yaw rate sensor 35, and uses a conversion table having characteristics as shown in FIG. 6 in which the self-alignment torque Msat with respect to the input actual yaw rate γ is stored. calculate.

  When the friction torque Mtdnw, the viscous torque Mtd, and the self-alignment torque Msat calculated in this way are input, the torque adding unit 42 applies to the supplied reaction force torque Tz (that is, reaction force torques Tzf and Tzr). Add up the input reaction torques. As a result, the torque adding unit 42 calculates the target reaction force torque Thf during the cutting operation and the target reaction force torque Thr during the return operation as the reaction force applied to the steering handle 11. Then, the torque adding unit 42 supplies the calculated target reaction force torque Th (that is, the target reaction force torque Thf, Thr) to the drive control unit 46.

  The drive control unit 46 inputs a drive current that flows from the drive circuit 37 to the electric motor in the reaction force actuator 13, and feedback-controls the drive circuit 37 so that a drive current corresponding to the target reaction force torque Th flows to the electric motor. To do. By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force corresponding to the target reaction force torque Th to the steering handle 11 via the steering input shaft 12.

  Thus, the driver feels a reaction force corresponding to the calculated target reaction torque Th from the steering handle 11, in other words, while applying a steering torque equal to the target reaction torque Th to the steering handle 11. The steering handle 11 is turned. At this time, in particular, if the detected steering angle θ is equal to or greater than the predetermined steering angle θz, the relationship between the steering angle θ and the target reaction force torque Th follows the above-mentioned Weber-Hefner law. The steering handle 11 can be rotated while receiving a sense suitable for human perception characteristics from the steering handle 11.

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 Various functions can be adopted as long as the functions are continuously connected to the exponential functions of Equations 7 and 9, respectively.
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 as the following Expression 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 above equation 10, as in the calculation of the reaction force torques Tzf and Tzr described above. As a result, the steering torque Tdf calculated according to the above-mentioned 6 and 7 and the steering torque Tdr calculated according to the above-mentioned formulas 8 and 9 are continuously connected, so that a smooth transition from the cutting operation to the returning operation can be achieved. Further, when the detected steering angle θ is less than the steering angle θz, the steering torque Tdf or the steering torque Tdr is calculated according to the equation 6 or the equation 8. Therefore, the steering torques Tdf and Tdr can be converged to “0”, and the steering torque Tdf and the steering torque Tdr are changed continuously (smoothly) even when the steering handle 11 is rotated across the neutral position. can do. In this case as well, instead of the calculations of the above formulas 6 to 10, the steering torques Tdf and Tdr are converted using the characteristic conversion table shown in FIG. 3 in which the steering torque Tdf and the steering torque Tdr with respect to the steering angle θ are stored. May be calculated. In the following description, the steering torque Tdf and the steering torque Tdr are collectively referred to as the steering torque Td.

The steering torque Td calculated in this way (that is, steering torque Tdf, Tdr) is supplied to the torque-lateral acceleration conversion unit 52. 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 = c1 · Td (| Td | <Tg) Equation 11
Gdf = C · Td ^K2 (Tg ≦ | Td |) Equation 12
Gdr = c2 · Td−Mh2 (| Td | <Tg) Equation 13
Gdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 14

  However, c1 in the equation 11 and c2 in the equation 13 are constants representing the slope of a linear function, and C and K2 in the equations 12 and 14 are constants. Further, the steering torque Td in the expressions 11 to 14 represents the absolute value of the steering torque Td calculated using the expressions 6 to 10 (that is, the steering torques Tdf and Tdr). If the torque Td is positive, the constants c1, c2 and the constant C are positive values. If the calculated steering torque Td is negative, the constants c1, c2 and the constant C are changed to the positive constants c1, c2 and the constant. A negative value representing the same absolute value as C.

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 with respect to the steering torque Td (corresponding to a Weber ratio related to torque 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.

  In this way, by calculating the hysteresis term Mh2, the expected lateral acceleration Gdf calculated according to the equation 11 or 12 and the expected lateral acceleration Gdr calculated according to the equation 13 or 14 are continuously connected. Therefore, the expected lateral acceleration Gdf can be smoothly switched to the expected lateral acceleration Gdr, and conversely, the expected lateral acceleration Gdr can be smoothly switched to the expected lateral acceleration Gdf. Further, by calculating the hysteresis term Mh2 in accordance with Equation 15, the expected lateral accelerations Gdf and Gdr at the time of change between the cutting operation and the returning operation are maintained. For this reason, as will be described later, the left and right front wheels FW1 and FW2 steered to the corrected target turning angle δd (static target turning angle δro) calculated based on the expected lateral accelerations Gdf and Gdr are, for example, roads Therefore, it is possible to prevent the turning angle from changing due to disturbance (such as fluctuations in self-alignment torque) input from the vehicle, and it is possible 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 expression 11 and the expression 13 are functions passing through the origin “0”, the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are prevented from becoming discontinuous.

  That is, if the driver expects the expected lateral acceleration, for example, a lateral acceleration that changes from the right direction to the left direction, the torque-lateral acceleration conversion unit 52 is linearly set to “0” according to Equation 13 above. The expected lateral acceleration Gdr that converges is calculated, and the expected lateral acceleration Gdf that increases linearly from “0” is calculated according to the above equation 11. 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 with respect to changes in vehicle behavior. In this case as well, instead of calculating the above formulas 11 to 15, the expected lateral acceleration Gdf, Gdr is obtained by using a conversion table having characteristics as shown in FIG. 7 in which the expected lateral acceleration Gdf, Gdr with respect to the steering torque Td is stored. May be calculated. In the following description, the expected lateral acceleration Gdf and the expected lateral acceleration Gdr are collectively referred to as the expected lateral acceleration Gd.

Here, Formula 12 applied at the time of the cutting operation will be described. The expression 14 applied during the return operation is configured in the same manner except that the steering torque Td in the expression 12 is expressed by the steering torque (Td−Mh2), and therefore the expression 12 will be described in detail. Thus, the description thereof is omitted. When the steering torque Td (specifically, the steering torque Tdf) is deleted using the expression 7, the following expression 16 is obtained.
Gdf = C · (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1 · K2 · θ) = Go · exp (K1 · K2 · θ)
In Expression 16, Go is a constant C · To ^K2 , and Expression 16 indicates that the expected lateral acceleration Gdf varies exponentially with respect to the steering angle θ of the steering wheel 11 by the driver. Note that the expected lateral acceleration Gdr changes exponentially with respect to the steering angle θ by modifying the equation 14 in the same manner as the transformation from the equation 12 to the equation 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 Tdf 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.

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

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

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

On the other hand, when the formula 7 is differentiated and the formula 7 is considered in the differentiated formula, the following formula 17 is established.
ΔT = To · exp (K1 · θ) · K1 · (dθ / dt) = T · K1 · (dθ / dt) Equation 17
When this equation 17 is modified and the Weber ratio ΔT / T related to the torque obtained by the above experiment is Kt, the following equation 18 is established.
K1 = ΔT / (T · (dθ / dt)) = Kt / (dθ / dt) Equation 18

If the maximum steering torque is Tmax, the following equation 19 is established from the equation 7.
Tmax = To · exp (K1 · θmax) Equation 19
If this equation 19 is modified, the following equation 20 is established.
K1 = log (Tmax / To) / θmax Equation 20
Then, the following equation 21 is derived from the equations 18 and 20.
dθ / dt = Kt / K1 = Kt · θmax / log (Tmax / To) ... Equation 21
In Equation 21, 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. It is. Since these values Kt, θmax, Tmax, and To are all constants determined by experiments and the system, the steering angular velocity dθ / dt can be calculated according to the equation (21). Further, a predetermined value (coefficient) K1 can be calculated based on the equation 18 using the steering angular velocity dθ / dt and the Weber ratio Kt.

In addition, when the formula 12 is differentiated and the formula 12 is considered in the differentiated formula, the following formula 22 is established.
ΔG = C · K2 · T ^K2-1 · ΔT = G · K2 · ΔT / T Equation 22
When Expression 22 is modified and the Weber ratio ΔT / T related to the torque obtained by the above experiment is Kt and the Weber ratio ΔF / F related to the lateral acceleration is Ka, the following Expressions 23 and 24 are established.
ΔG / G = K2 · ΔT / T Equation 23
K2 = Ka / Kt ... Formula 24
In Equation 24, 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 (for example, α and β). Therefore, these Weber ratios Kt, Using Ka, the coefficient K2 can also be calculated based on Equation 24 above.

Further, if the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following expression 25 is derived from the expression 12.
C = Gmax / Tmax ^K2 Equation 25
In Equation 25, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 24. 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 experiment and system, the parameters K1, K2, and C can be determined in advance by calculation. Accordingly, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction torques Tzf and Tzr and the steering torques Tdf and Tdr that match the driver's perceptual characteristics using the above equations 1 to 15. 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. The turning angle conversion unit 53 calculates the target turning angle δro 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 δro with respect to the expected lateral acceleration Gd. This table causes the vehicle to run in a steady circular turn by turning the steering handle 11 at a constant steering angular velocity dθ / dt while changing the vehicle speed V, thereby turning the steering angle δ and lateral acceleration of the left and right front wheels FW1, FW2. G is a set of data collected by actually measuring G in advance. Then, the turning angle conversion unit 53 calculates a target turning angle δro corresponding to the input expected lateral acceleration Gd and the detected vehicle speed V input from the vehicle speed sensor 33 with reference to this table. Since the calculated target turning angle δro is calculated for a vehicle that makes a steady circular turn, it will be referred to as a static target turning angle δro in the following description. Further, the lateral acceleration G (expected lateral acceleration Gd) and the static target turning angle δro stored in the table are both positive, but the expected lateral acceleration Gd supplied from the turning angle conversion unit 53 is negative. If so, the output static target turning angle δro is also negative.

Since the static target turning angle δro is a function of the vehicle speed V and the lateral acceleration G, instead of referring to the table, the following equation 26 is calculated as a vehicle motion equation for steady circular turning Can also be calculated.
δro = L · (1 + A · V ² ) · Gd / V ² Equation 26
However, L in the formula 26 is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

The static target turning angle δro calculated according to Equation 26 is supplied to the turning angle correction unit 54. The turning angle correction unit 54 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also receives the actual lateral acceleration G detected by the lateral acceleration sensor 34. And the turning angle correction | amendment part 54 performs the calculation of following formula 27, correct | amends the static target turning angle (delta) ro input, and the correction target as a target turning angle which steers the right-and-left front wheel FW1, FW2. The turning angle δd is calculated.
δd = δro + K3 · (Gd−G) Equation 27
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 Δd increases. Further, when the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the absolute value of the corrected target turning angle δd 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 calculated with higher accuracy.

  The static target turning angle δro and the corrected target turning angle δd calculated as described above are supplied to the turning control unit 60. In the turning control unit 60, the gradient limit calculating unit 61 calculates the gradient limiting target turning angle δr1 for limiting the turning angular speed of the left and right front wheels FW1 and FW2, and moderates the behavior change accompanying the turning of the vehicle. Therefore, the target turning angle δr as the target control turning angle is determined. Hereinafter, the calculation of the gradient limit calculation unit 61 will be described in detail.

The static target turning angle δro of the left and right front wheels FW1 and FW2 for realizing the expected lateral acceleration Gd expected by the driver can be calculated according to the equation 26. At this time, if the maximum value of the expected lateral acceleration Gd is Gmax and the turning angle for generating the maximum value Gmax is δmax, the equation 26 can be modified as shown in the following equation 28.
δmax = L · (1 + A · V ² ) · Gmax / V ² Equation 28
According to Expression 28, when the maximum value Gmax of the expected lateral acceleration Gd expected by the driver is set to a constant value, the turning angle δmax becomes a function with respect to the detected vehicle speed V, and as the detected vehicle speed V increases. The steered angle δmax decreases, and as the detected vehicle speed V decreases, the steered angle δmax increases. In other words, as the detected vehicle speed V increases, the steered area of the left and right front wheels FW1, FW2 for generating the same expected lateral acceleration Gd decreases, and as the detected vehicle speed V decreases, the same expected lateral acceleration The steering area of the left and right front wheels FW1, FW2 for generating Gd is increased.

Further, the static target turning angle δro expressed by the equation 26 can be expressed as a relationship with the steering angle θ as shown in the following equation 29 by being transformed using the equation 16.
δro = (L · (1 + A · V ² ) / V ² ) · Go · exp (K1 · K2 · θ) Equation 29
Considering the case where the vehicle speed V is constant for easy understanding, the static target turning angle δro is exponential with respect to the change in the steering angle θ of the steering wheel 11 according to the equation 29. To change. Therefore, the static target turning angle δro has a non-linear characteristic that protrudes downward with respect to a change in the steering angle θ. Therefore, now considering the case where the driver rotates the steering handle 11 at a constant steering angular velocity dθ / dt (hereinafter, this rotating operation is referred to as a static rotating operation), the steering handle 11 is in the neutral position. When the turning operation is performed in the vicinity, the change in the static target turning angle δro with respect to the change in the steering angle θ is small, and when the steering handle 11 is turned at a position away from the neutral position, the static with respect to the change in the steering angle θ is reduced. The change in the target turning angle δro becomes extremely large.

  For this reason, when the driver rotates the steering handle 11 in the vicinity of the neutral position, the left and right front wheels FW1 and FW2 turn slowly with respect to the turning operation of the steering handle 11. On the other hand, when the driver rotates the steering handle 11 at a position away from the vicinity of the neutral position, in particular, the steering handle 11 is rotated at a position near the maximum steering angle θmax (hereinafter, this vicinity position is referred to as an end vicinity position). The left and right front wheels FW1, FW2 are steered sharply with respect to the turning operation of the steering handle 11.

  The change characteristic of the static target turning angle δro with respect to the steering angle θ also changes depending on the detected vehicle speed V. That is, as described above, according to the equation 28, when the same expected lateral acceleration Gd (maximum value Gmax) is generated, the steered area of the left and right front wheels FW1, FW2 as the detected vehicle speed V increases. As the detected vehicle speed V decreases, the steered area of the left and right front wheels FW1, FW2 increases. In particular, in a situation where the detected vehicle speed V decreases and the steered region increases, a static target that changes exponentially with respect to a change in the steering angle θ when the steering handle 11 is turned near the end position. The change in the turning angle δro becomes extremely large. As a result, as the detected vehicle speed V decreases, the left and right front wheels FW1, FW2 tend to steer sharply with respect to the turning operation of the steering handle 11, and the behavior of the vehicle is disturbed, making driving difficult.

  Furthermore, the change characteristic of the static target turning angle δro with respect to the steering angle θ described above is a turning operation (hereinafter referred to as “steering angular velocity dθ / dt”) that is different from that in the case of the static turning operation of the steering handle 11. This rotation operation appears more prominently when it is called a dynamic rotation operation. This will be described in detail below.

  Generally, the driver drives the vehicle by a dynamic turning operation of the steering handle 11. That is, the driver starts the turning operation of the steering handle 11 at a large steering angular velocity dθ / dt, and ends the turning operation of the steering handle 11 at a small steering angular velocity dθ / dt. At this time, since the steering angle sensor 31 detects and outputs the steering angle θ at a predetermined short time interval, when the steering angular velocity dθ / dt changes in a series of turning operations of the steering handle 11, The static target turning angle δro calculated using the detected steering angle θ according to the equation 29 is a discrete (discontinuous) value in time series. In other words, when the steering angular velocity dθ / dt changes in a series of turning operations of the steering handle 11, the calculated static target turning angle δro dynamically changes with respect to the steering angular velocity dθ / dt. It becomes like this.

  More specifically, as described above, the static target turning angle δro changes exponentially with respect to the steering angle θ, and therefore the steering angular velocity dθ / dt particularly at the position near the end of the steering handle 11 is If it is large, the change gradient value dδro / dt of the static target turning angle δro per minute control time t increases, and the time constant decreases. On the other hand, when the steering angular velocity dθ / dt is small, the change gradient value dδro / dt is small and the time constant is large. Thus, the change gradient value dδro / dt of the static target turning angle δro differs depending on the magnitude of the steering angular velocity dθ / dt. Here, in the steering-by-wire type steering apparatus, the left and right front wheels FW1 and FW2 are steered by driving the steered actuator 21 in accordance with the turning operation of the steering handle 11 by the driver. That is, the steering actuator 21 controls the left and right front wheels FW1 and FW2 according to the steering angular velocity dθ / dt of the steering handle 11 to a limit steering angular velocity dδ / dt (hereinafter referred to as the steering angular velocity) preset in the system. Steering is performed at a speed less than or equal to the steering performance limit speed dδ / dt. For this reason, the turning actuator 21 has a larger turning performance limit speed dδ / dt than the change gradient value dδro / dt of the static target turning angle δro that changes in accordance with the magnitude of the steering angular speed dθ / dt. In this case, the left and right front wheels FW1, FW2 are steered at a turning angular velocity corresponding to the change gradient value dδro / dt. On the other hand, when the turning performance limit speed dδ / dt is smaller than the change gradient value dδro / dt, the left and right front wheels FW1, FW2 are turned at the turning performance limit speed dδ / dt. This will be described with reference to FIG.

  FIG. 9 shows a change in the turning angle δ when the turning operation of the steering handle 11 is started at the point s (time t = 0) and is returned after a predetermined time has elapsed. When the driver performs a turning operation with a large steering angular velocity dθ / dt (hereinafter, this turning operation is referred to as fast steering), the change gradient value dδro / dt of the static target turning angle δro is: It changes as shown by a thin alternate long and short dash line in FIG. However, since the change gradient value dδro / dt has a larger value than the turning performance limit speed dδ / dt of the turning actuator 21, the turning actuator 21 sets the left and right front wheels FW1, FW2 to the turning performance limit. Turn at speed dδ / dt. Therefore, in this case, the left and right front wheels FW1 and FW2 are steered to the static target turning angle δro according to a straight line passing through the points s and a as shown by the thick dashed line in FIG.

  When the driver performs a turning operation with a relatively large steering angular velocity dθ / dt (hereinafter, this turning operation is referred to as a relatively fast steering), the change gradient value dδro of the static target turning angle δro. / Dt changes as shown by a thin solid line in FIG. In this case, as shown by a thick solid line in FIG. 9, the steering actuator 21 has left and right front wheels at a turning angular velocity corresponding to the change gradient value dδro / dt of the static target turning angle δro up to point d. FW1 and FW2 are steered, and then the left and right front wheels FW1 and FW2 are steered to the point b at the steerability limit speed dδ / dt. Further, when the driver performs a turning operation with a small steering angular velocity dθ / dt (hereinafter, this turning operation is referred to as slow steering), the steered actuator 21 is indicated by a thick broken line in FIG. Further, the left and right front wheels FW1, FW2 are steered from the point s to the point c at a turning angular velocity corresponding to the change gradient value dδro / dt.

  In this way, the steering actuator 21 moves the left and right front wheels FW1, FW2 so as to follow the change gradient value dδro / dt of the static target turning angle δro with a turning angular speed equal to or less than the turning performance limit speed dδ / dt. Steer. However, when the preset turning performance limit speed dδ / dt of the turning actuator 21 is large, the left and right front wheels FW1, FW2 are steered sharply. As a result, the turning behavior of the vehicle, in other words, steering stability is improved. There are cases where it cannot be secured properly. Therefore, the gradient limit calculation unit 61 gently changes the behavior of the vehicle to generate the expected lateral acceleration Gd anticipated by the driver, that is, limits the turning angular velocity of the left and right front wheels FW1 and FW2 and sets the target turning angle δd. The gradient limit target turning angle δr1 for gently turning to is calculated. Hereinafter, the calculation of the gradient limited target turning angle Δr1 will be described in detail.

The gradient limit calculation unit 61 calculates the gradient limit target turning angle δr1 according to the following equation 30.
δr1 = δr1 _(n−1) + dδa / dt Equation 30
Here, δr1 _(n−1) in the equation 30 is the gradient limited target turning angle δr1 calculated at the time of the previous program execution, and dδa / dt is when turning the left and right front wheels FW1, FW2. This is the maximum turning angular velocity at which the vehicle can turn stably, and is expressed by the following equation (31).
dδa / dt <(dδ / dt) · Kd Equation 31
However, Kd in the formula 31 is a predetermined coefficient, which is a positive coefficient of 1 or less. The coefficient Kd may be calculated as a function of the vehicle speed V. In this case, the coefficient Kd may have a characteristic that changes greatly as the vehicle speed V increases and changes small as the vehicle speed V decreases. As a result, the left and right front wheels FW1 and FW2 are quickly steered as the vehicle speed V increases, and the left and right front wheels FW1 and FW2 are gradually steered as the vehicle speed V decreases.

  Then, when the gradient limit calculating unit 61 calculates the gradient limited target turning angle δr1 according to the equations 30 and 31, the gradient limit calculating unit 61 compares it with the static target turning angle δro calculated according to the equation 26, and the corrected target turning angle δd. The target turning angle δr in the changing process up to is determined. That is, the gradient limit calculation unit 61 determines the static target turning angle δro as the target turning angle δr if the calculated gradient limiting target turning angle δr1 is equal to or greater than the input static target turning angle δro. On the other hand, if the gradient restricted target turning angle Δr1 is less than the static target turning angle Δro, the gradient restricted target turning angle Δr1 is determined as the target turning angle Δr.

Specifically, using FIG. 10, the gradient limit calculation unit 61 inputs the static target turning angle δro _(n−1) calculated according to the equation 26 at a predetermined control time t−1. The gradient limited target turning angle δr1 _(n−1) calculated in accordance with the equations 30 and 31 is compared. In this comparison, if the static target turning angle δro _(n−1) is larger than the gradient limited target turning angle δr1 _{(n −1)} , the change gradient value of the static target turning angle δro _(t−1) dδro / dt is larger than the maximum turning angular velocity dδa / dt. Therefore, the gradient limit calculation unit 61 limits the change gradient value dδro / dt of the static target turning angle δro _(t−1) by the maximum turning angular velocity dδa / dt, so that the target at the control time t−1 is set. The turning angle δr _(n−1) is determined as the gradient limited target turning angle δr1 _(n−1) . Similarly, the target turning angle Δr at the control time t is determined as the gradient limited target turning angle Δr1. The target turning angle δr determined in this way is supplied to the filter processing calculation unit 62.

In the steering control of the left and right front wheels FW1 and FW2, the filter processing calculation unit 62 generates an unnecessary yaw rate that is generated in accordance with the transition from the changing process up to the corrected target turning angle δd to the maintaining process at the corrected target turning angle δd. In order to suppress this, the target turning angle δr is filtered. Specifically, as described above, when the steering handle 11 is turned by the driver, the left and right front wheels FW1 and FW2 generate the expected lateral acceleration Gd expected by the driver as shown in FIG. The steering is controlled up to the corrected target turning angle δd. And if it changes to the point a, b, and c in FIG. 9, the steering operation of the left and right front wheels FW1, FW2 is finished and maintained at the corrected target turning angle δd. At this time, at points a, b, and c, the operating state of the left and right front wheels FW1, FW2 suddenly changes to a stopped state, so the driver may perceive an unnecessary yaw rate. For this reason, the filter processing calculation unit 62 makes the turning operation immediately before the turning angle δ (that is, the target turning angle δr) of the left and right front wheels FW1, FW2 reaches the corrected target turning angle δd. According to the following equation 32, a filter target turning angle δrf obtained by filtering the target turning angle δr that changes to the corrected target turning angle δd is calculated.
δrf = δr _(n−1) + B · (δd−δr _(n−1) ) Equation 32
However, B in the formula 32 is a predetermined constant.

Here, the filter processing calculation unit 62 inputs the actual turning angle δ, that is, the target turning angle δr from the turning angle sensor 32, and in the relationship between the actual turning angle δ and the corrected target turning angle δd. When the following equation 33 is satisfied, the target turning angle δr is filtered.
δd−δr <Ksf Equation 33
Here, δd in the equation 33 is a corrected target turning angle calculated according to the equation 27, and Ksf is a predetermined positive coefficient for determining the starting point of the filtering process. The coefficient Ksf may also be calculated as a function of the vehicle speed V. In this case, it is preferable that the coefficient Ksf has a characteristic that changes greatly as the vehicle speed V increases and changes slightly as the vehicle speed V decreases. Thereby, even when the vehicle speed V changes, an unnecessary yaw rate can be effectively suppressed.

  The calculation of the filter processing calculation unit 62 will be specifically described with reference to FIG. 11. The filter processing calculation unit 62 inputs the actual turning angle δ from the turning angle sensor 32. Then, the filter processing calculation unit 62 compares the corrected target turning angle δd with the input actual turning angle δ, that is, the target turning angle δr according to the equation 33. As a result of this comparison, if the difference between the corrected target turning angle δd and the input target turning angle δr is equal to or greater than the predetermined coefficient Ksf, the filter processing calculation unit 62 is expected to expect the target turning angle δr from the driver. Since the corrected target turning angle δd for generating the lateral acceleration Gd has not yet been reached, the filter process is not executed. Therefore, the filter processing calculation unit 62 supplies the target turning angle δr as it is to the drive control unit 63 described later as the filter target turning angle δrf. On the other hand, if the difference between the corrected target turning angle δd and the input actual turning angle δ (target turning angle δr) is less than the predetermined coefficient Ksf, the filter processing calculation unit 62 paraphrases the above Expression 33. For example, since the target turning angle δr is close to the corrected target turning angle δd, the target turning angle δr is filtered according to the equation 32 to calculate the filter target turning angle δrf. As a result, in the turning operation of the left and right front wheels FW1, FW2, it is possible to smoothly shift from the changing process up to the corrected target turning angle δd to the maintaining process at the corrected target turning angle δd, and the driver does not need the yaw rate. Can be effectively suppressed.

  Then, the filter target turning angle δrf determined as described above is supplied to the drive control unit 63. The drive control unit 63 inputs the actual turning angle δ detected by the turning angle sensor 32, and the left and right front wheels FW1, FW2 are the target turning angle δrf (target turning angle δr), in other words, the maximum turning angular velocity dδa / The rotation of the electric motor in the turning actuator 21 is feedback-controlled so that the turning is performed to the corrected target turning angle δd with a turning angular velocity of dt or less. The drive control unit 63 also receives a drive current flowing from the drive circuit 38 to the same electric motor, and feedback-controls the drive circuit 38 so that a drive current having a magnitude corresponding to the steering torque appropriately flows to the same 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 δd by the displacement of the rack bar 24 in the axial direction.

  As can be understood from the above description, according to this embodiment, when the left and right front wheels FW1 and FW2 are steered in response to the turning operation of the steering handle 11 by the driver, the steered control unit 60 is used. Thus, the vehicle is steered at a turning angular velocity equal to or less than the maximum turning angular velocity dδa / dt. As a result, steep turning of the left and right front wheels FW1 and FW2 due to the dynamic turning operation of the steering handle 11 is suppressed, and unnecessary yaw rate is generated when the steering operation state of the left and right front wheels FW1 and FW2 is switched. Can be suppressed. Therefore, the driver can drive without worrying about the unstable turning behavior of the vehicle due to the turning operation of the steering handle 11, which makes the driving of the vehicle simple and always good. Steering stability can be perceived.

  That is, as shown by the one-dot chain line in FIG. 12, when the driver rotates the steering handle 11 by fast steering, the gradient limit calculation unit 61 calculates the target turning angle δr according to the equation 30. The gradient limited target turning angle δr1 is adopted. Thereby, the left and right front wheels FW1, FW2 are steered at the maximum steered angular velocity dδa / dt. At this time, by appropriately setting the predetermined coefficient Kd in the equation 31, the target turning angle δr that can effectively prevent the sharp turning of the left and right front wheels FW1 and FW2 can be determined. A stable vehicle behavior at the time can be ensured. Further, since the target turning angle δr becomes the corrected target turning angle δd at the point a ′ by being filtered by the filter processing calculation unit 62, the operating state and the stop state in the turning operation of the left and right front wheels FW1, FW2 Can be smoothly transitioned. This effectively suppresses the driver from perceiving an unnecessary yaw rate. Therefore, the driver can perceive good steering stability.

  Further, as shown by a solid line in FIG. 12, when the driver rotates the steering handle 11 by relatively fast steering, the gradient limit calculation unit 61 statically sets the target turning angle δr up to the point d ′. The target steering angle δro is adopted and the gradient limited target turning angle δr1 is adopted from the point d ′, whereby the left and right front wheels FW1, FW2 are steered at a maximum turning angular velocity dδa / dt or less. For this reason, steep steering of the left and right front wheels FW1, FW2 can be effectively prevented, and stable vehicle behavior can be ensured when the vehicle turns. Further, even in this relatively fast steering, the target turning angle δr becomes the corrected target turning angle δd at the point b ′ by being filtered by the filter processing calculation unit 62, so that the driver can set an unnecessary yaw rate. Perception can be effectively prevented. Therefore, also in this case, the driver can perceive good steering stability. Furthermore, as indicated by a broken line in FIG. 12, when the driver rotates the steering handle 11 by slow steering, the gradient limit calculation unit 61 sets the static target turning angle δro as the target turning angle δr. In addition, the target turning angle δr is filtered by the filter processing calculation unit 62. Thereby, since the target turning angle δr becomes the corrected target turning angle δd at the point c ′, it is effective for the driver to perceive an unnecessary yaw rate while ensuring stable behavior of the vehicle at the time of vehicle turning. Can be prevented.

  In the above description, the turning operation immediately before the turning angle δ (that is, the target turning angle δr) of the left and right front wheels FW1 and FW2 reaches the corrected target turning angle δd has been described. However, as is apparent from the above equations 32 and 33, the steering wheel 11 is returned or cut from a state where the turning angle δ of the left and right front wheels FW1 and FW2 is maintained at the corrected target turning angle δd, that is, from a stopped state. Even when the operation state is shifted to the operating state again, the filter processing calculation unit 62 filters the target turning angle δr. As a result, even when the steering operation of the left and right front wheels FW1 and FW2 is switched from the stopped state (maintenance process) to the operating state (change process), the driver can smoothly shift the yaw rate that is unnecessary. Perception can be effectively prevented. Therefore, the driver can perceive good steering stability.

  In the sensory adaptation control unit 50, the torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd that changes exponentially (or exponentially) with respect to the steering torque Td (steering torque Tdf, Tdr). To do. As a result, when the vehicle turns by turning the left and right front wheels FW1 and FW2, the driver is given the expected lateral acceleration Gd as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. The expected lateral acceleration Gd changes exponentially (or exponentially) with respect to the steering angle θ of the steering wheel 11, so that the driver can determine the amount of motion state that matches human perception characteristics. The steering handle 11 can be operated while perceiving. 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 first modification of the above embodiment in which the yaw rate is adopted as the motion state quantity will be described. In the first modification, the computer program executed by the electronic control unit 36 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 above embodiment, but a torque-yaw rate conversion unit 55 is provided instead of the torque-lateral acceleration conversion unit 52 in the above embodiment. ing.

The torque-yaw rate conversion unit 55 is supplied with the steering torques Tdf and Tdr calculated from the displacement-torque conversion unit 51. In this first modification as well, the torque-yaw rate conversion unit 55 performs 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. The torque-yaw rate converter 55 calculates the expected yaw rate γdf that the driver expects by turning the steering wheel 11 according to the following equations 34 and 35, and the expected yaw rate γdr that is expected by the return operation according to the following equations 36 and 37. calculate. Here, the following Expression 34 or Expression 36 is a linear function of the steering torque Td as in the above embodiment, and is a function in which the expected yaw rates γdf and γdr are “0” when the steering torque Td is “0”. Further, the following formula 35 or 37 is a power function of the steering torque Td as in the above embodiment, and is continuously connected to the following formulas 34 and 36 at a predetermined value Tg.
γdf = c1 · Td (| Td | <Tg) Equation 34
γdf = C · Td ^K2 (Tg ≦ | Td |) Equation 35
γdr = c2 · Td−Mh2 (| Td | <Tg) Equation 36
γdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 37
However, c1 in the equation 34 and c2 in the equation 34 are constants representing the slope of the linear function, and C and K2 in the equations 35 and 37 are constants. Further, the steering torque Td in the equations 34 to 37 represents the absolute value of the steering torque Td (that is, the steering torques Tdf and Tdr) calculated by using the equations 6 to 10, and the calculated steering. If the torque Td is negative, the constants c1, c2 and the constant C are set to negative values having the same absolute value as the positive constants c1, c2 and the constant C.

Further, Mh2 in the expressions 36 and 37 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. Therefore, in other words, it is a hysteresis term in order to constitute a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh2 is determined based on the ratio between 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 by the following equation 38.
Mh2 = nq · (Kq · Td) Equation 38
However, Kq in the equation 38 is a Weber ratio with respect to the steering torque Td, and nq is a predetermined coefficient for the minimum change sensitivity. In the first modified example, the hysteresis term Mh2 is derived without including the steering angle θ as in the equation 38, but instead of or in addition to this, for example, including the steering angle θ. It is also possible to derive so as to depend on the steering angle θ.

  In this way, by calculating the hysteresis term Mh2, the expected yaw rate γdf calculated according to the equation 34 or 35 and the expected yaw rate γdr calculated according to the equation 36 or 37 are continuously connected. Therefore, it is possible to smoothly switch from the expected 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 38, 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 δd calculated based on the expected yaw rates γdf and γdr are rotated by, for example, disturbance input from the road. It is possible to prevent the steering angle from changing, and to maintain the behavior of the vehicle as expected by the driver.

  Further, when the steering torque Td is less than the predetermined value Tg, the expected yaw rate γdf and the expected yaw rate γdr are calculated according to the above equations 34 and 36. As a result, even when the steering handle 11 is rotated across the neutral position, since the equation 34 and the equation 36 are functions passing through the origin “0”, the expected yaw rate γdf and the expected yaw rate γdr Is prevented from becoming discontinuous.

  In other words, when the value is less than the predetermined value Tg, both the expression 33 and the expression 35 are functions that pass through the origin “0”. For this reason, if the driver expects the yaw rate changing from the right direction to the left direction as the expected yaw rate, for example, the torque-yaw rate conversion unit 55 converges to “0” in a linear function according to the equation 34. The expected yaw rate γdr is calculated, and the expected yaw rate γdf that increases linearly from “0” according to the above equation 34 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. In this case as well, instead of calculating the equations 34 to 38, the expected yaw rates γdf and γdr are calculated using a conversion table having characteristics as shown in FIG. 14 storing the expected yaw rates γdf and γdr with respect to the steering torque Td. You may make it do.

  The expected yaw rates γdf and γdr calculated by the torque-yaw rate conversion unit 55 are supplied to the turning angle conversion unit 56. The steered angle conversion unit 56 executes the calculation described later in the same way regardless of the expected yaw rates γdf and γdr supplied from the torque-yaw rate conversion unit 55. γdf and γdr are collectively described as the expected yaw rate γd. The turning angle conversion unit 56 calculates the target turning angle δro of the left and right front wheels FW1 and FW2 necessary for generating 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 δro with respect to the expected yaw rate γd This table turns the steering wheel 11 at a constant steering angular velocity dθ / dt while changing the vehicle speed V, thereby turning the vehicle in a steady circle, turning the left and right front wheels FW1, FW2 turning angle δ, yaw rate γ, Is a set of data collected by actually measuring in advance. Then, the turning angle conversion unit 56 refers to this table and calculates a target turning angle δro corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33. Since the target turning angle δro calculated using the table shown in FIG. 15 is also calculated for a vehicle that makes a steady circular turn, it will be referred to as a static target turning angle δro in the following description. If the yaw rate γ (expected yaw rate γd) and the static target turning angle δro stored in the table are both positive, but the expected yaw rate γd supplied from the torque-yaw rate converting unit 55 is negative. The output static target turning angle δro is also negative.

Since the static target turning angle δro is a function of the vehicle speed V and the yaw rate γ, instead of referring to the table, by executing the calculation of the following equation 39 as a vehicle motion equation when making a steady circular turn Can also be calculated.
δro = L · (1 + A · V ² ) · γd / V Equation 39
However, L in the formula 39 is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

The static target turning angle δro calculated according to Equation 39 is supplied to the turning angle correction unit 54. The turning angle correction unit 54 receives the expected yaw rate γd from the torque-yaw rate conversion unit 55 and also receives the actual yaw rate γ detected by the yaw rate sensor 35. Then, similarly to the above embodiment, the turning angle correction unit 54 executes the calculation of the following equation 40, corrects the input static target turning angle δro, and calculates the corrected target turning angle δd. .
δd = δro + K4 · (γd−γ) Equation 40
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 δd becomes larger. When the actual yaw rate γ exceeds the expected yaw rate γd, the absolute value of the corrected target turning angle δd is corrected to be smaller. By this correction, the turning angle δ of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd is more accurately ensured.

  The static target turning angle δro calculated in this way is supplied to the turning control unit 60 as in the above embodiment. As a result, the gradient limit calculation unit 61 calculates the gradient limit target turning angle δr1 for limiting the turning angular velocity of the left and right front wheels FW1, FW2, and the target for making the behavior change accompanying the turning of the vehicle moderate. Determine the turning angle δr. That is, also in this first modification, when the steering actuator 21 steers the left and right front wheels FW1, FW2 with a large steering performance limit speed dδ / dt, the behavior of the vehicle may not be ensured properly. Therefore, the gradient limit calculation unit 61 calculates the gradient limit target turning angle δr1 for gently turning the left and right front wheels FW1 and FW2 according to the equations 30 and 31.

  Then, when the gradient limit calculating unit 61 calculates the gradient limited target turning angle δr1 according to the equations 30 and 31, the gradient limit calculating unit 61 compares the target turning angle δr with the static target turning angle δro calculated according to the equation 39. decide. That is, as in the above embodiment, the gradient limit calculation unit 61 sets the static target turning angle δro as the target turning angle δr if the gradient limited target turning angle δr1 is equal to or larger than the static target turning angle δro. decide. On the other hand, if the gradient restricted target turning angle Δr1 is less than the static target turning angle Δro, the gradient restricted target turning angle Δr1 is determined as the target turning angle Δr. The target turning angle δr determined in this way is supplied to the filter processing calculation unit 62.

  In the same manner as in the above embodiment, the filter processing calculation unit 62 is configured to reduce the turning operation immediately before the turning angle δ of the left and right front wheels FW1 and FW2 reaches the corrected target turning angle δd. The target turning angle δr is filtered according to 33 to calculate the filter target turning angle δrf. In other words, the filter processing calculation unit 62 receives the actual turning angle δ (that is, the target turning angle δr) from the turning angle sensor 32, and the actual turning angle that is input as the corrected target turning angle δd according to the equation 33. δ (target turning angle δr) is compared. As a result of this comparison, if the difference between the corrected target turning angle δd and the target turning angle δr is equal to or larger than the predetermined coefficient Ksf, the filter processing calculation unit 62 determines that the target turning angle δr is expected by the driver. Since the corrected target turning angle δd for generating the angle has not yet been reached, the filter process is not executed. Therefore, the filter processing calculation unit 62 supplies the target turning angle δr as it is to the drive control unit 63 as the filter target turning angle δrf. On the other hand, if the difference between the corrected target turning angle δd and the target turning angle δr is less than the predetermined coefficient Ksf, the filter processing calculation unit 62 holds the expression 33, and therefore the target turning angle according to the expression 32. The filter target turning angle δrf is calculated by filtering δr. As a result, in the turning operation of the left and right front wheels FW1, FW2, it is possible to smoothly shift from the changing process up to the corrected target turning angle δd to the maintaining process at the corrected target turning angle δd, and the driver does not need the yaw rate. Can be effectively reduced.

  Further, other program processes executed by the electronic control unit 36 are the same as those in the above embodiment. And in the functional block diagram of FIG. 13, the same code | symbol as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  And also in the 1st modification demonstrated above, the effect similar to the said embodiment can be anticipated. In the first modification, when the vehicle turns by turning the left and right front wheels FW1 and FW2, the turning is expected to give the driver a “physical quantity of the given stimulus” according to the Weber-Hefner law. The yaw rate γd is given. Since it changes exponentially with respect to the steering angle θ, the driver can operate the steering wheel 11 while perceiving a motion state quantity that matches human perception characteristics. . As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Next, a description will be given of a second modification of the above embodiment using a turning curvature instead of the lateral acceleration as the motion state quantity in the above embodiment. Also in the second modified example, the vehicle steering device is configured as shown in FIG. 1 as in the above embodiment. However, the computer program executed by the electronic control unit 36 is slightly different from that in the above embodiment.

  In the second modification, the computer program executed by the electronic control unit 36 is shown by the functional block diagram of FIG. In this case, the displacement-torque converter 51 functions in the sensory adaptation control unit 50 in the same manner as in the above embodiment, but a torque-turning curvature converter 57 is provided instead of the torque-lateral acceleration converter 52 in the above embodiment. ing.

  The torque-turning curvature conversion unit 57 is supplied with the steering torques Tdf and Tdr calculated from the displacement-torque conversion unit 51. In this second modified example, the torque-turning curvature converting unit 57 similarly performs the calculation described later regardless of the steering torque Tdf, Tdr supplied from the displacement-torque converting unit 51. Therefore, in the following description, the steering torques Tdf and Tdr are collectively described as the steering torque Td. Then, the torque-turning curvature conversion unit 57 calculates the expected turning curvature ρdf that the driver expects by the turning operation of the steering handle 11 in accordance with the following formulas 41 and 42, and the expected turning curvature ρdr that is expected by the return operation: Calculate according to equations 43 and 44.

At this time, the torque-turning curvature conversion unit 57 calculates the expected turning curvatures ρdf and ρdr according to the following formulas 41 and 43 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 42 and 44. Here, the following equation 41 or 43 is a linear function equation of the steering torque Td as in the above-described embodiment, and is a function in which the expected turning curvatures ρdf and ρdr are “0” when the steering torque Td is “0”. . The following formulas 42 and 44 are power functions of the steering torque Td as in the above embodiment, and are continuously connected to the following formulas 41 and 43 at a predetermined value Tg.
ρdf = c1 · Td (| Td | <Tg) Equation 41
ρdf = C · Td ^K2 (Tg ≦ | Td |) Equation 42
ρdr = c2 · Td−Mh2 (| Td | <Tg) Equation 43
ρdr = C · (Td−Mh2) ^K2 (Tg ≦ | Td |) Equation 44
However, c1 in the equation 41 and c2 in the equation 43 are constants representing the slope of a linear function, and C and K2 in the equations 42 and 44 are constants. Further, the steering torque Td in the equations 41 to 44 represents the absolute value of the steering torque Td (that is, the steering torques Tdf and Tdr) calculated by using the equations 6 to 9, and the calculated steering torque. If the torque Td is positive, the constants c1, c2 and the constant C are positive values. If the calculated steering torque Td is negative, the constants c1, c2 and the constant C are changed to the positive constants c1, c2 and the constant. A negative value having the same absolute value as C.

Further, Mh2 in the equations 43 and 44 represents the calculated expected turning curvature ρdf and expected turning curvature ρdr continuously when the turning operation of the steering handle 11 by the driver is changed from the cutting operation to the returning operation. In other words, the hysteresis term is used to construct a hysteresis characteristic between the cutting operation and the returning operation. This hysteresis term Mh2 is determined based on the ratio of the expected turning curvature ρdf at the time of the cutting operation and the expected turning curvature ρdr at the time of the return operation at the time when a certain steering torque Td is supplied, and is expressed as the following Expression 45. The
Mh2 = nq · (Kq · Td) Equation 45
In Equation 45, 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 second modified example, the hysteresis term Mh2 is derived so as not to include the steering angle θ as in Expression 45, but instead of or in addition to this, for example, the steering angle θ is included. It is also possible to derive so as to depend on the steering angle θ.

  Thus, by calculating the hysteresis term Mh2, the expected turning curvature ρdf calculated according to the equation 41 or 42 and the expected turning curvature ρdr calculated according to the equation 43 or 44 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 45, the expected turning curvatures ρdf and ρdr at the time of change between the cutting operation and the returning operation are maintained. For this reason, as will be described later, the left and right front wheels FW1 and FW2 steered to the corrected target turning angle δd calculated based on the expected turning curvatures ρdf and ρdr are caused by, for example, disturbance input from the road. It is possible to prevent the turning angle from changing, and to maintain the behavior of the vehicle expected by the driver.

  Further, when the steering torque Td is less than the predetermined value Tg, the expected turning curvature ρdf and the expected turning curvature ρdr are calculated according to the equations 41 and 43, so that the steering handle 11 is turned over the neutral position. Even in this case, since the equation 41 and the equation 43 are functions passing through the origin “0”, the expected turning curvature ρdf and the expected turning curvature ρdr are prevented from becoming discontinuous. In this case as well, instead of the calculations of the equations 41 to 45, the expected turning curvature ρdf, using the conversion table having the characteristics as shown in FIG. ρdr may be calculated.

  The expected turning curvatures ρdf and ρdr calculated by the torque-turning curvature conversion unit 57 are supplied to the turning angle conversion unit 58. In addition, in the following description, the turning angle conversion unit 58 performs the calculation described later in the same manner regardless of the expected turning curvatures ρdf and ρdr supplied from the torque-turning curvature conversion unit 56. The expected turning curvatures ρdf and ρdr are collectively described as the expected turning curvature ρd. The turning angle conversion unit 58 calculates the target turning angle δro of the left and right front wheels FW1, 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 δro with respect to the expected turning curvature ρd. This table turns the steering wheel 11 at a constant steering angular velocity dθ / dt while changing the vehicle speed V, thereby turning the vehicle in a steady circle, turning the left and right front wheels FW1, FW2 turning angle δ and turning curvature ρ. Is a set of data collected by actually measuring in advance. Then, the turning angle conversion unit 58 refers to this table and calculates a target turning angle δro corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33. Since the target turning angle δro calculated using the table shown in FIG. 18 is also calculated for a vehicle that makes a steady circular turn, it is also referred to as a static target turning angle δro in the following description. Further, although the turning curvature ρ (expected turning curvature ρd) and the static target turning angle δro stored in the table are both positive, the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 57 is If it is negative, the output static target turning angle δro is also negative.

Since the static target turning angle δro is a function of the vehicle speed V and the turning curvature ρ, instead of referring to the table, the calculation of the following equation 46 is performed as a vehicle motion equation in a steady circular turning. Can also be calculated.
δro = L · (1 + A · V ² ) · ρd Equation 46
However, L in the formula 46 is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

The static target turning angle δro calculated according to the equation 46 is supplied to the turning angle correction unit 54. The turning angle correction unit 54 in the second modification also inputs the vehicle speed V detected by the vehicle speed sensor 33 and the yaw rate γ detected by the yaw rate sensor 35. Then, the turning angle correction unit 54 calculates the actual turning curvature ρ by executing the calculation of the following equation 47 using the input vehicle speed V and yaw rate γ.
ρ = G / V ² or ρ = γ / V Equation 47
Further, the turning angle correction unit 54 receives the expected turning curvature ρd from the torque-turning curvature converting unit 57, and uses the inputted expected turning curvature ρd and the actual turning curvature ρ calculated according to the equation 47, the following equation 48 Execute the operation. Then, the turning angle correction unit 54 corrects the input static target turning angle δro and calculates the corrected target turning angle δd.
δd = δd + K5 · (ρd−ρ) Equation 48
However, the coefficient K5 is a predetermined positive constant, and when the actual turning curvature ρ is less than the expected turning curvature ρd, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle δd becomes larger. When the actual turning curvature ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δd is corrected to be smaller. By this correction, the turning angle δ of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd is more accurately ensured.

  The static target turning angle δro calculated in this way is supplied to the turning angular velocity limit control unit 60 as in the above embodiment. As a result, the gradient limit calculation unit 61 calculates the gradient limit target turning angle δr1 for limiting the turning angular velocity of the left and right front wheels FW1, FW2, and the target for making the behavior change accompanying the turning of the vehicle moderate. Determine the turning angle δr. That is, also in the second modification, when the steering actuator 21 steers the left and right front wheels FW1 and FW2 with a large steering performance limit speed dδ / dt, the behavior of the vehicle may not be properly secured. Therefore, the gradient limit calculation unit 61 secures the expected turning curvature ρd expected by the driver and sets the gradient limit target turning angle δr1 for gently turning the left and right front wheels FW1 and FW2 in the above formulas 30 and 31. Calculate according to

  Then, when the gradient limit calculating unit 61 calculates the gradient limited target turning angle δr1 according to the equations 30 and 31, it compares with the static target turning angle δro calculated according to the equation 46, and the target turning angle δr. To decide. That is, as in the above embodiment, the gradient limit calculation unit 61 sets the static target turning angle δro as the target turning angle δr if the gradient limited target turning angle δr1 is equal to or larger than the static target turning angle δro. decide. On the other hand, if the gradient restricted target turning angle Δr1 is less than the static target turning angle Δro, the gradient restricted target turning angle Δr1 is determined as the target turning angle Δr. The target turning angle δr determined in this way is supplied to the filter processing calculation unit 62.

  In the same manner as in the above embodiment, the filter processing calculation unit 62 is configured to reduce the turning operation immediately before the turning angle δ of the left and right front wheels FW1 and FW2 reaches the corrected target turning angle δd. The target turning angle δr is filtered according to 33 to calculate the filter target turning angle δrf. In other words, the filter processing calculation unit 62 receives the actual turning angle δ (that is, the target turning angle δr) from the turning angle sensor 32, and the actual turning angle that is input as the corrected target turning angle δd according to the equation 33. δ (target turning angle δr) is compared. As a result of this comparison, if the difference between the corrected target turning angle δd and the target turning angle δr is equal to or greater than a predetermined coefficient Ksf, the filter processing calculation unit 62 calculates the expected turning curvature that the target turning angle δr is expected by the driver. Since the correction target turning angle δd for generating ρd has not yet been reached, the filtering process is not executed. Therefore, the filter processing calculation unit 62 supplies the target turning angle δr as it is to the drive control unit 63 as the filter target turning angle δrf. On the other hand, if the difference between the corrected target turning angle δd and the target turning angle δr is less than the predetermined coefficient Ksf, the filter processing calculation unit 62 holds the expression 33, and therefore the target turning angle according to the expression 32. The filter target turning angle δrf is calculated by filtering δr. As a result, in the turning operation of the left and right front wheels FW1, FW2, it is possible to smoothly shift from the changing process up to the corrected target turning angle δd to the maintaining process at the corrected target turning angle δd, and the driver does not need the yaw rate. Can be effectively reduced.

  Further, other program processes executed by the electronic control unit 36 are the same as those in the above embodiment. And in the functional block diagram of FIG. 16, the same code | symbol as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  And also in the 2nd modification demonstrated above, the effect similar to the said embodiment can be anticipated. In this third modification, when the vehicle turns by turning the left and right front wheels FW1 and FW2, the turn is expected to give the driver a “physical quantity of the given stimulus” according to the Weber-Hefner law. A turning curvature ρd is given. Since it changes exponentially with respect to the steering angle θ, the driver can operate the steering wheel 11 while perceiving a motion state quantity that matches human perception characteristics. . As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Next, a third modification example in which the steering torque T is used as the operation input value of the steering handle 11 will be described. In the third modified example, as shown by a broken line in FIG. 1, a steering torque sensor 39 that is assembled to the steering input shaft 12 and detects the steering torque T applied to the steering handle 11 is provided. Other configurations are the same as those in the above embodiment, but the computer program executed by the electronic control unit 36 is slightly different from that in the above embodiment.

  In the case of the third modified example, 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 above embodiment. -Instead of the steering torque Td calculated by the torque conversion unit 51, the expected lateral acceleration Gd is calculated by executing the calculations of Expressions 11 to 15 using the steering torque T detected by the steering torque sensor 39. In this case as well, the expected lateral acceleration Gd may be calculated using a table representing the characteristics shown in FIG. Other program processes executed by the electronic control unit 36 are the same as those in the above embodiment.

  According to the third modification, the steering torque T as the driver's operation input value for the steering handle 11 is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52. The converted expected lateral acceleration Gd is determined as the static target turning angle δro by the turning angle conversion unit 53 and is corrected to the corrected target turning angle δd by the turning angle correction unit 54. The static target turning angle δro is supplied to the gradient limit calculation unit 61 and is compared with the gradient limit target turning angle δr1 calculated by the calculation unit 61 to determine the target turning angle δr. The determined target turning angle δr is supplied to the filter processing calculation unit 62, and is filtered by the calculation unit 62 to determine the filter target turning angle δrf. Then, the drive control unit 63 inputs the actual turning angle δ detected by the turning angle sensor 32, and the left and right front wheels FW1 and FW2 are turned at the target turning angle δrf, in other words, at the maximum turning angular velocity dδa / dt or less. The rotation of the electric motor in the turning actuator 21 is feedback-controlled so that the turning is performed to the corrected target turning angle δd by the angular velocity.

  Thereby, the left and right front wheels FW1, FW2 are steered to the target turning angle δd. In this case as well, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected lateral acceleration Gd changes exponentially with respect to the steering torque T. Therefore, the steering handle 11 can be turned according to human perceptual characteristics. Accordingly, also in this third modified example, as in the case of the above-described 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 above embodiment is expected.

  Furthermore, the vehicle steering control according to the above embodiment and the vehicle steering control according to the third modification may be switchable. That is, when both the steering angle sensor 31 and the steering torque sensor 39 are provided and the expected lateral acceleration Gd is calculated using the target steering torque Td calculated by the displacement-torque conversion unit 51 as in the above embodiment, It is also possible to switch between the case where the expected lateral acceleration Gd is calculated using the steering torque T detected by the steering torque sensor 39 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.

  Furthermore, the implementation of the present invention is not limited to the above-described embodiment and the first to third modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the embodiment and each modification, 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.

  Moreover, in the said embodiment and each modification, by rotating the steering output shaft 22 using the steering actuator 21, the left and right front wheels FW1 and FW2 were steered. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 24 using the steered actuator 21.

It is the schematic of the steering apparatus of the vehicle which concerns on embodiment and each modification of this invention. It is a functional block diagram functionally showing the computer program processing performed in the electronic control unit of FIG. 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 angular velocity and friction torque. It is a graph which shows the relationship between steering angular velocity and viscous torque. It is a graph which shows the relationship between a yaw rate and a self-alignment 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 static target turning angle. It is a figure for demonstrating the change with respect to the steering angular velocity of the steering angle at the time of turning left and right front wheels according to a static target turning angle. It is a figure for demonstrating determination of the target turning angle in a change process. It is a figure for demonstrating the filter process of a target turning angle. It is a figure for demonstrating the change with respect to the steering angular velocity of the steering angle at the time of determining a target turning angle and performing filter processing. FIG. 9 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a first modification of the present invention. It is a graph which shows the relationship between steering torque and estimated yaw rate. It is a graph which shows the relationship between an expected yaw rate and a target turning angle. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a second modification 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 left and right wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction force actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, DESCRIPTION OF SYMBOLS 33 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Yaw rate sensor, 36 ... Electronic control unit, 39 ... Steering torque sensor, 40 ... Reaction force control part, 41 ... Displacement-torque conversion part, 42 ... Torque addition part, 50 ... sensory adaptation control unit, 51 ... displacement-torque conversion unit, 52 ... torque-lateral acceleration conversion unit, 53, 56, 58 ... turning angle conversion unit, 54 ... turning angle correction unit, 55 ... torque-yaw rate conversion unit , 57 ... torque-turning curvature conversion unit, 60 ... steering control unit, 61 ... gradient limit calculation unit, 62 ... filter processing calculation unit, 63 ... drive control unit

Claims (8)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
The estimated motion state quantity of the vehicle, which represents the motion state of the vehicle perceived by the driver in relation to the turning of the vehicle and has a predetermined exponential relationship or a power relationship with the operation input value to the steering wheel, is detected. Motion state quantity calculating means for calculating using the manipulated input value;
A turning angle calculation means for calculating a target 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;
Steering angular speed limiting means for limiting the steering angular speed of the steered wheels in a changing process in which the steered wheels steer to the calculated target steered angle to a maximum steered angular speed at which the vehicle can stably turn. When,
The steering control unit is configured to control the steering actuator in accordance with the calculated target turning angle and the maximum turning angular velocity to turn the steered wheels to the calculated target turning angle. A steering-by-wire vehicle steering apparatus characterized by the above. In the steering apparatus for a steering-by-wire vehicle according to claim 1,
The turning angular velocity limiting means,
Limiting turning angle calculation means for calculating a limiting turning angle for limiting the turning angular speed of the steered wheels in the changing process using the maximum turning angular speed;
Comparing the absolute value of the transient turning angle in the changing process sequentially calculated by the turning angle calculation means with the absolute value of the limiting turning angle calculated by the restricted turning angle calculation means, If the absolute value of the transient turning angle is larger than the absolute value of the limited turning angle, the limited turning angle is determined as a target control turning angle for turning control of the steered wheels in the changing process. In addition, if the absolute value of the transient turning angle is equal to or less than the absolute value of the limit turning angle, target control turning angle determination means for determining the transient turning angle as the target control turning angle A steering-by-wire vehicle steering apparatus characterized by comprising: In the steering apparatus for a steering-by-wire vehicle according to claim 1,
The steering control device, and
When the steered wheel is steered by the steer control means, when the transition process shifts from the change process to the maintenance process maintained at the target turning angle, or when the transition process shifts from the maintenance process to the change process. Further, there is provided a filter processing means for filtering a change in the turning angle of the steered wheels in the changing process with respect to time so as to change the turning angle gradually. Steering device. In the steering device for a steering-by-wire vehicle according to claim 3,
The filter processing means executes the filter processing when a difference between an absolute value of a turning angle of the steered wheels and an absolute value of the target turning angle in the changing process is less than a predetermined value. A steering-by-wire vehicle steering apparatus. In the steering apparatus for a steering-by-wire vehicle according to claim 1,
The operation input value detection means includes a displacement amount sensor that detects the displacement amount of the steering wheel,
The motion state quantity calculating means includes an operation force conversion means for converting the detected displacement amount into an operation force applied to the steering handle, and an exercise state for converting the converted operation force into the expected motion state quantity. A steering-by-wire type vehicle steering apparatus characterized by comprising a quantity conversion means. In the steering apparatus for a steering-by-wire vehicle according to claim 1,
The operation input value detection means includes an operation force sensor that detects an operation force applied to the steering handle,
A steering-by-wire steering apparatus for a vehicle according to claim 1, wherein the motion state quantity calculating means comprises a motion state quantity conversion means for converting the detected operating force into the expected motion state quantity. In the steering apparatus for a steering-by-wire vehicle according to claim 1,
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 device for a steering-by-wire vehicle according to claim 1, 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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