JP2009292214A - Vehicle steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the changing of a rigid impression of a vehicle steering system, given to a driver steering a steering wheel 18, due to a change in steering frequency while maintaining the impression at a sufficiently high level. <P>SOLUTION: The vehicle steering system includes a transmission ratio variable mechanism 22 disposed on a steering force transmission mechanism 12 linking a steering wheel 18 with steered wheels 30 and a steering control device 14 for controlling operations of the transmission ratio variable mechanism 22. The transmission ratio variable mechanism 22 has an actuator which outputs an output rotation angle obtained by adding an actuator angle to an input rotation angle by the drive of a motor. The steering control device 14 has a compensator which outputs a desired value of a torque to be generated by the motor according to the input of a control deviation between a desired actuator angle and a detected actuator angle. The compensator has frequency characteristics including a gain rising region in which a gain rises as a frequency falls and a constant gain region in which the gain remains constant within a frequency band lower than the gain rising region. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a transmission ratio variable mechanism provided in a steering force transmission mechanism that connects a steering wheel and a steered wheel, and a control unit that controls the operation of the transmission ratio variable mechanism. It has an actuator that adds an actuator angle to the input rotation angle by driving to output an output rotation angle, and changes the transmission ratio between the input rotation angle and the output rotation angle, and the control unit has a compensator, The present invention relates to a vehicle steering apparatus that controls driving of a motor in accordance with a control deviation between a target actuator angle and a detected actuator angle.

  Conventionally, a vehicle steering apparatus has been considered in which a transmission ratio variable mechanism is provided in a steering force transmission mechanism that connects a steering wheel and a steered wheel. Such a vehicle steering apparatus includes a control unit that controls the operation of the transmission ratio variable mechanism, and the transmission ratio variable mechanism changes the transmission ratio in the steering force transmission mechanism by the driving force of the motor.

  For example, Patent Document 1 describes a steering apparatus in which an input shaft and an output shaft are connected via a transmission ratio variable mechanism, a steering handle is connected to the input shaft, and an output shaft is connected to a rack shaft. Has been. The transmission ratio variable mechanism includes a gear mechanism that connects the input shaft and the output shaft, and drives the gear mechanism with a motor to change the transmission ratio between the steering angle of the steering wheel and the turning angle of the wheel. It has a function. A steering control device that performs drive control of the transmission ratio variable mechanism includes a transmission ratio setting unit, a switching unit, a compensator, a motor drive circuit, and the like, and includes a transmission ratio set by the transmission ratio setting unit and an input angle sensor. Based on the detected input angle, the output angle target value is set, and the deviation between the set output angle target value and the output angle detected by the output angle sensor is output to the compensator. A proportional gain, differentiator, differential gain, integrator and integral gain are provided, and a target current value to be given to the motor is determined.

  Patent Document 2 discloses a vehicle steering apparatus including a transmission ratio variable device that varies a transmission ratio between a steering angle of a steering wheel and a steering angle of a steered wheel, and an IFSECU that controls the operation of the transmission ratio variable device. Is described. The transmission ratio variable device includes a differential mechanism that couples a first shaft and a second shaft, and a motor that drives the differential mechanism. The differential mechanism includes a pair of circular splines that are coaxially arranged, A wave gear mechanism comprising a flex spline meshed with each spline inside the spline and a wave generator for rotating the meshing portion is employed.

Japanese Patent No. 3344464 JP 2007-313928 A

  In the case of the steering device described in Patent Document 1, the compensator includes an integrator, so that the gain of the compensator increases as the steering frequency of the steering wheel decreases. For this reason, as the steering wheel is steered at a lower frequency, the angle deviation with respect to the target turning angle of the wheel becomes smaller and the turning angle with respect to the steering angle becomes larger. As a result, the restoring torque called self-aligning torque increases and the steering reaction force also increases, that is, the responsiveness increases. On the other hand, when the steering handle is steered at a high frequency, the angle deviation with respect to the target turning angle becomes large, and the turning angle with respect to the steering angle becomes small. As a result, the restoring torque is reduced and the steering reaction force is also reduced, that is, the responsiveness is lowered. In other words, when the steering wheel is steered at a low frequency, the rigidity of the steering force transmission mechanism felt by the driver is increased, and when the steering handle is steered at a high frequency, the rigidity of the steering force transmission mechanism felt by the driver is increased. Becomes lower. For this reason, since the feeling of rigidity changes depending on the steering frequency, the driver feels uncomfortable, that is, the driver's steering feeling deteriorates.

  On the other hand, it is also conceivable to omit the integrator from the compensator and control the transmission ratio variable device by PD control. In this case, the steering frequency is less than a certain frequency and the gain is affected by the change in frequency. May be constant. Since the actual steerable frequency band is below a certain frequency, if the gain can be made constant below a certain frequency, there will be no practical problem. Therefore, when the transmission ratio variable device is controlled by PD control as described above, there is a possibility that the rigidity feeling when the driver steers the steering wheel can be prevented from changing due to a change in the steering frequency. is there. However, in this case, the gain in a constant gain range may be low, and the angle control of the steering force transmission mechanism cannot be performed with high accuracy, and the rigidity may be lowered.

  It is an object of the present invention to suppress a change in rigidity due to a change in steering frequency while sufficiently increasing the rigidity when a driver steers a steering wheel in a vehicle steering apparatus.

  A vehicle steering apparatus according to the present invention includes a transmission ratio variable mechanism provided in a steering force transmission mechanism that connects a steering wheel and a steered wheel, and a control unit that controls the operation of the transmission ratio variable mechanism. The variable mechanism includes an actuator that adds an actuator angle to an input rotation angle by driving a motor to output an output rotation angle, and changes a transmission ratio between the input rotation angle and the output rotation angle. The compensator has a compensator that controls the drive of the motor according to the control deviation between the target actuator angle and the detected actuator angle. The compensator outputs the target torque generated by the motor according to the input of the control deviation. The frequency characteristic of the vehicle has a gain increase region where the gain increases as the frequency decreases, and a gain constant region where the gain is constant in a frequency band lower than the gain increase region. It is the use steering apparatus.

  According to the above-described vehicle steering apparatus, the frequency characteristics of the compensator included in the control unit are a gain increase region where the gain increases as the frequency decreases, and a constant gain constant in a frequency band lower than the gain increase region. The gain of the compensator can be made constant at least in part of the steerable frequency band that is below a certain frequency, and even if the steering frequency changes, the angular deviation with respect to the target rotation angle does not change. Can be. For this reason, the magnitude of the turning angle of the steered wheels with respect to the steering angle can be prevented from changing due to a change in the steering frequency in at least a part of the steerable frequency band, and the steering reaction force can also be prevented from changing. As a result, since the rate of change of the steering reaction force with respect to the steering angle does not change, it is possible to suppress a change in the feeling of rigidity when the driver steers the steering wheel. In addition, since the gain in the constant gain region can be easily increased, the angle control of the steering force transmission mechanism can be performed with high accuracy, and the rigidity can be sufficiently increased.

  In the vehicle steering apparatus according to the present invention, preferably, the steering angle detecting means for detecting the steering angle of the steering handle and the motor rotation for detecting the rotation angle of the motor, which is a relative rotation angle with respect to the steering angle of the steering handle. An angle detection unit, and the control unit calculates a detection actuator angle from a setting unit that sets a target actuator angle according to a running state of the vehicle and a detected value of the steering angle, and a detected value of the rotation angle of the motor. Detection actuator angle calculation means.

  Further, in the vehicle steering apparatus according to the present invention, preferably, the setting means includes a target actuator according to an angle setting coefficient set by a detected value of the vehicle speed representing a traveling state of the vehicle and a detected value of the steering angle. Set the corner.

  In the vehicle steering apparatus according to the present invention, preferably, the actuator includes a motor and a gear transmission whose gear ratio changes according to the rotational angular velocity of the motor.

  In the vehicle steering apparatus according to the present invention, preferably, at least a part of the constant gain region is in the steering frequency band.

  In the vehicle steering apparatus according to the present invention, preferably, the control unit changes the frequency band of the constant gain region in the frequency characteristics of the compensator according to the vehicle speed.

  According to the above-described vehicle steering device, the angle deviation with respect to the target rotation angle changes according to the vehicle speed of the vehicle, so that the rigidity feeling can be changed according to the vehicle speed. In addition, it is possible to suppress a change in rigidity due to a change in steering frequency at the same vehicle speed.

  In the vehicle steering apparatus according to the present invention, preferably, the control unit increases the gain in the constant gain region when the vehicle speed is high to be higher than the gain in the constant gain region when the vehicle speed is low.

  According to the above vehicle steering device, the angle deviation with respect to the target rotation angle when the vehicle speed is high can be further reduced, and the rigidity can be increased. Moreover, when the vehicle speed is high, the practical upper limit of the frequency band that can be steered is lower than when the vehicle speed is low, so when the vehicle speed is high, the upper limit frequency of the constant gain region is low. It is difficult to cause practical problems.

  According to the vehicle steering device of the present invention, it is possible to suppress a change in the rigidity due to a change in the steering frequency while sufficiently increasing the rigidity when the driver steers the steering wheel. For this reason, it is possible to realize a vehicle steering apparatus that makes it difficult for the driver to feel uncomfortable during steering.

[First Embodiment]
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. 1 to 4 show a first embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a steering apparatus that is a vehicle steering apparatus according to the present embodiment. FIG. 2 is a schematic sectional view of an actuator constituting the steering device of FIG. FIG. 3 is a block diagram illustrating a configuration of a steering control device that constitutes the steering device of FIG. 1. FIG. 4 is a diagram illustrating the frequency characteristics of the compensator of FIG. 3 using the relationship between frequency and gain.

  As shown in FIG. 1, the steering device 10 according to the present embodiment includes a steering force transmission mechanism 12, a steering control device 14 that is a control unit, and a vehicle speed sensor 16. The steering force transmission mechanism 12 includes an input shaft 20 to which a steering handle 18 is coupled, an output shaft 24 connected to the input shaft 20 via a transmission ratio variable mechanism 22, and a rack and pinion type in which the output shaft 24 is engaged. Gear device 26, a rack shaft 28 engaged with the gear device 26, and steered wheels 30 connected to the left and right sides of the rack shaft 28. That is, the steering force transmission mechanism 12 connects the steering handle 18 and the steered wheels 30 so that the steering force can be transmitted. Further, the input shaft 20 and the output shaft 24 constitute a steering shaft. Further, the steering control device 14 controls the operation of the transmission ratio variable mechanism 22.

As shown in FIG. 2, the transmission ratio variable mechanism 22 includes an actuator 32 that connects the input shaft 20 and the output shaft 24. The actuator 32 includes a motor 34 and a wave gear device 36 that is a gear transmission. That is, the actuator 32 includes a motor housing 38 coupled and fixed to the input shaft 20, a coupling member 40 coupled and fixed to the output shaft 24, a motor 34 supported on the inner side of the motor housing 38, the motor housing 38 and the coupling. And a wave gear device 36 provided inside the member 40. The rotation shaft 42 of the motor 34 is coaxial with the central axes of the motor housing 38 and the connecting member 40.

  The wave gear device 36 includes a wave generator 44 fixed to the outer diameter side of the rotating shaft 42 of the motor 34, a ball bearing outside the wave generator 44, and a flex spline 46 that is a metal elastic body with teeth formed on the outer periphery. And a pair of circular splines 48 and 50 fixed to the inner peripheral surfaces of the motor housing 38 and the connecting member 40, respectively, and the number of teeth of the lower circular spline 50 is made larger than the number of teeth of the upper circular spline 48. ing.

  When the wave generator 44 is rotated by the rotation of the motor 34, the flex spline 46 is elastically deformed and the meshing position with the circular splines 48 and 50 is sequentially moved, and the rotation of the wave generator 44 is transmitted to the circular splines 48 and 50. . Since the number of teeth of the lower circular spline 50 is larger than the number of teeth of the upper circular spline 48, the wave gear device 36 acts as a speed reducer.

  Further, since the rotation angle of the input shaft 20 becomes the input rotation angle of the actuator 32 and the rotation angle of the output shaft 24 becomes the output rotation angle of the actuator 32, the actuator 32 is driven by the motor 34 to rotate the input shaft 20. That is, the actuator angle is added to the steering angle, the rotation angle of the output shaft 24 is output, and the transmission ratio between the rotation angle of the input shaft 20 and the rotation angle of the output shaft 24 is changed. In such a wave gear device 36, the torque of the steering handle 18 (FIG. 1) and the torque of the motor 34 are respectively input from the motor housing 38 side and the rotating shaft 42 side of the motor 34 which are the input side. It is used as a 2-input 1-output type in which output torque is output from the connecting member 40 side, which is the output side. According to the wave gear device 36, the gear ratio between the rotation of the steering handle 18 and the rotation of the output shaft 24, that is, the gear ratio of the wave gear device 36 is added to the steering angle or the steering angular velocity of the steering handle 18. It changes according to the rotation angle or rotation angular velocity of 34.

  Returning to FIG. 1, the input shaft 20 is provided with a steering angle sensor 52 which is a steering angle detection means for detecting the steering angle of the steering handle 18. A signal representing the detected value of the steering angle, which is a detection signal of the steering angle sensor 52, is input to the steering control device 14. Further, a motor angle sensor 54 is provided which is a motor rotation angle detection means for detecting the rotation angle of the motor 34 (FIG. 2), which is a relative rotation angle with respect to the rotation angle of the steering handle 18. That is, the stator constituting the motor 34 is fixed to the motor housing 38 (FIG. 2), and when the steering handle 18 rotates, the stator also rotates. However, the motor angle sensor 54 rotates relative to the steering angle of the steering handle 18. The rotation angle of the motor 34, which is an angle, is detected. A signal representing a detected value of the rotation angle, which is a detection signal of the motor angle sensor 54, is also input to the steering control device 14. A detection signal from a vehicle speed sensor 16 that detects the speed of the vehicle is also input to the steering control device 14.

  The steering control device 14 controls the operation of the transmission ratio variable mechanism 22 by controlling the drive of the motor 34 (FIG. 2) based on the input of each detection signal. Next, the configuration of the steering control device 14 will be described with reference to FIG. In the following description, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

As shown in FIG. 3, the steering control device 14 includes a microcomputer having a CPU, a memory, and the like, and is a setting means, that is, a target actuator angle calculation unit 56, a detection actuator angle calculation means 58, a compensator 60, And a motor drive circuit 62. The target actuator angle calculation unit 56 includes a storage unit that stores data representing a map that defines the relationship between the vehicle speed V and the angle setting coefficient K _{H. The} target actuator angle calculation unit 56 calculates a map from the vehicle speed V detected by the vehicle speed sensor 16. By performing a map search using the data to be represented, the angle setting coefficient K _H corresponding to the vehicle speed V is set.

Further, the target actuator angle calculation unit 56 sets the target actuator angle θ _AR of the actuator 32 from the steering angle θ _H detected by the steering angle sensor 52 and the angle setting coefficient K _{H according} to the following equation.

θ _AR = K _H θ _H (1)

That is, the target actuator angle calculation unit 56 represents the target actuator angle θ _AR in accordance with the angle setting coefficient K _H set by the detected value of the vehicle speed V and the detected value θ _H of the steering angle, which represents the running state of the vehicle. Set. In other words, the target actuator angle calculation unit 56 sets the target actuator angle θ _AR according to the traveling state of the vehicle and the detected value of the steering angle.

The detected actuator angle calculation means 58 calculates the detected actuator angle θ _A of the actuator 32 from the rotation angle (θ _H −θ _M ) of the motor 34 detected by the motor angle sensor 54, θ _A = (θ _H −θ _M ) / R. Here, θ _M is the absolute rotation angle of the motor 34. R is a constant uniquely determined from the number of teeth of each of the gears of the wave gear device 36, such as the circular splines 48, 50, and is larger than 1 (R> 1). Is).

On the other hand, the relationship represented by the following equation is established among the steering angle θ _H , the actuator angle θ _A, and the rotation angle θ _P of the output shaft 24 that is the steering shaft on the steered wheel 30 side.

θ _P = θ _H + θ _A (2)

That is, the actuator 32 is driven by the motor 34, by adding an actuator angle theta _A steering angle theta _H is the input rotation angle is output rotation angle, and outputs the rotation angle theta _P of the output shaft 24. As is clear from the above equations (1) and (2), the transmission ratio from the steering angle θ _H to the rotation angle θ _P of the output shaft 24 is (1 + K _H ).

Further, a control deviation e (= θ _AR −θ _A ) between the target actuator angle θ _AR obtained by the target actuator angle calculation unit 56 and the detected actuator angle θ _A obtained by the detected actuator angle calculation means 58 is obtained. Input to the compensator 60. Compensator 60 from the control deviation e, using the transfer function C (s), and outputs the generated torque target value T _M of the motor 34 by the following equation.

T _M = C (s) e (3)
That is, the compensator 60 outputs the generated torque target value T _M of the motor 34 in response to the input of the control deviation e.

  In particular, in the case of the present embodiment, the compensator 60 includes a proportional gain, a differentiator, a differential gain, and a phase delay compensation unit, and does not include an integrator. That is, the transfer function C (s) of the compensator 60 is expressed by the following equation.

Here, G _P is a proportional gain, G _D is a differential gain, ω _D is a lower corner frequency, and ω _N is an intermediate corner frequency.

  Since the transfer function C (s) is set in this way, the frequency characteristic of the compensator 60 is expressed as shown in FIG. In FIG. 4, the solid line P represents the frequency characteristic of the compensator 60 in the present embodiment, and the alternate long and short dash line Q represents the frequency characteristic of the compensator in the comparative example. The compensator of the comparative example is the compensator 60 of the present embodiment and does not include the delay compensation unit, and includes a proportional gain, a differentiator, a differential gain, an integrator, and an integral gain. In the steering control device having such a compensator of the comparative example, the drive of the motor is controlled by PID control.

As is clear from FIG. 4, in the present embodiment, the frequency characteristic of the compensator 60 is a constant gain region 64 where the gain is constant at a frequency equal to or lower than the lower corner frequency ω _D. That is, the lower corner frequency ω _D is the upper limit frequency of the constant gain region 64. Further, the lower corner frequency ω _D is matched with the upper limit of the steering frequency band, which is a frequency region in which normal steering is possible when the driver steers the steering wheel 18. However, the lower corner frequency ω _D can be set to a frequency higher than the upper limit of the steering frequency band. In any case, with this configuration, the gain becomes constant even when the frequency changes within the steering frequency band. The steering frequency band is, for example, about 5 Hz or less. For example, the upper limit of the steering frequency band is 5 Hz.

Returning to FIG. 3, the generated torque target value T _M of the motor 34 output from the compensator 60 is output to the motor drive circuit 62. The motor drive circuit 62, based on the generated torque target value T _M, and outputs a control signal to the motor 34, as generated torque of the motor 34 approaches the generated torque target value T _M, and controls the driving of the motor 34 , actuator angle is so close to the target actuator angle θ _AR. Thus, the steering control device 14 controls the drive of the motor 34 according to the control deviation e between the target actuator angle θ _AR and the detected actuator angle θ _A.

As is clear from FIG. 4, the frequency characteristics of the compensator 60 include a gain increase region 66 where the gain increases as the frequency decreases, and a gain constant region 64 in a frequency band lower than the gain increase region 66. Have. The steering frequency band is within the range of the constant gain region 64 as described above. Note that at least part of the constant gain region 64 only needs to be in the steering frequency band, and the lower corner frequency ω _D can be set to a frequency lower than the upper limit of the steering frequency band.

According to the steering device 10 of this embodiment, the frequency characteristics of the compensator 60 included in the steering control device 14 are lower than the gain increasing region 66 where the gain increases as the frequency decreases, and the gain increasing region 66. And a constant gain region 64 having a constant gain in the frequency band. For this reason, the gain of the compensator can be made constant in at least a part of the steering frequency band that is equal to or lower than a certain frequency, and even if the steering frequency changes when the steering wheel 18 is steered by the driver, the angle deviation with respect to the target rotation angle Can be prevented from changing. For this reason, the magnitude of the turning angle of the steered wheels 30 with respect to the steering angle θ _H can be prevented from changing regardless of changes in the steering frequency in at least a part of the steering frequency band, and the self-aligning torque can be changed. In addition, the steering reaction force can be prevented from changing. Therefore, since neither change rate of change of the steering reaction force to the steering angle theta _H, it is possible to suppress the driver to change the stiffness feeling when steering the steering wheel 18. In addition, since the gain in the constant gain region 64 can be easily increased, the angle control of the steering force transmission mechanism 12 can be performed with high accuracy, and the rigidity can be sufficiently increased. As a result, it is possible to suppress a change in the sense of rigidity due to a change in the steering frequency while sufficiently increasing the sense of rigidity when the driver steers the steering handle 18. For this reason, it is possible to realize the steering device 10 that makes it difficult for the driver to feel uncomfortable during steering.

Next, the effects of the present embodiment will be described using FIGS. 5 to 8 in comparison with a comparative example. FIG. 5A shows the time lapse of the steering angle θ _H when the steering wheel reciprocates at a constant period in the steering device of the comparative example, and FIG. 5B shows the time lapse of the actuator angle θ _{A in} the same manner. the time course of c) is also the steering reaction force T _H, illustrates respectively. FIG. 6 is a diagram illustrating a relationship between the steering angle θ _H and the steering reaction force T _H in the comparative example. 7A shows the time lapse of the steering angle θ _H when the steering wheel reciprocates at a constant period in the steering device of the present embodiment, and FIG. 7B shows the time lapse of the actuator angle θ _{A in} the same manner. , the time course of same steering reaction force T _H is (c), it illustrates respectively. FIG. 8 is a diagram showing the relationship between the steering angle θ _H and the steering reaction force T _H in the present embodiment.

The steering device of the comparative example having the relationship of the steering angle θ _H , the actuator angle θ _A , and the steering reaction force T _H as shown in FIGS. 5 and 6 has the frequency characteristic represented by the one-dot chain line Q in FIG. The other configuration is the same as that of the steering device 10 of the present embodiment. That is, the steering device of the comparative example controls the drive of the motor by PID control. For this reason, in the steering frequency band, the gain decreases as the frequency increases, and the gain changes depending on the frequency. 5 and 6, the solid lines R1, R2, R3, and T reciprocate the steering handle 18 at a low frequency, and the broken lines S1, S2, S3, and U reciprocate the steering handle 18 at a high frequency. Represents each. As shown in FIGS. 5B and 5C, when the steering wheel 18 is reciprocated at a low frequency in the comparative example, the gain of the compensator is high, so the amplitude of the actually generated actuator angle θ _A is large. Accordingly, the steering reaction force T _H also increases. In contrast, when reciprocating steering wheel 18 at high frequencies, the gain of the compensator is lower, the amplitude of the actuator angle theta _A is reduced, along with this, also small steering reaction force T _H . That is, as shown in FIG. 6, in the case of the comparative example, the relationship of the steering reaction force T _{H with} respect to the steering angle θ _H changes depending on the steering frequency, so that the rigidity feeling when the driver steers the steering handle 18 is changed. Changes and the driver tends to feel uncomfortable during steering.

On the other hand, the steering device 10 of the present embodiment having the relationship of the steering angle θ _H , the actuator angle θ _A , and the steering reaction force T _H as shown in FIGS. 7 and 8 is the solid line P in FIG. As shown in FIG. 8, the steering frequency band has a constant gain region 64 where the gain is constant regardless of the change in frequency. In FIG. 7, the solid lines V1, V2, and V3 represent the case where the steering handle 18 reciprocates at a low frequency, and the broken lines W1, W2, and W3 represent the case that the steering handle 18 reciprocates at a high frequency. In FIG. 8, a solid line T1 represents that the relationship between the steering angle θ _H and the steering reaction force T _H is the same when the steering frequency is both high and low.

As is apparent from FIG. 7, in the case of the present embodiment, the amplitude of the actually generated actuator angle θ _{A and} the amplitude of the steering reaction force T _H are respectively determined regardless of the change in the steering frequency. Be the same. Further, as is apparent from FIG. 8, the relationship of the steering reaction force T _{H with} respect to the steering angle θ _H does not change due to a change in the steering frequency. For this reason, it is possible to suppress the change in the sense of rigidity due to the change in the steering frequency, and it is possible to realize the steering device 10 that makes it difficult for the driver to feel uncomfortable during steering.

  In the present embodiment, the gear transmission provided in the actuator 32 is described as the wave gear device 36. However, this gear transmission uses a structure other than the wave gear device 36, such as a planetary gear device. You can also When the planetary gear device is used, the input shaft 20 and the output shaft 24 are connected to any two elements of the ring gear, the carrier, and the sun gear constituting the planetary gear device, respectively, and the remaining elements of the motor 34 are connected. The rotating shaft 42 is connected. For this reason, the transmission ratio between the input rotation angle and the output rotation angle of the actuator 32 is changed by driving the motor 34.

[Second Embodiment]
9 to 11 show a second embodiment of the present invention. FIG. 9 is a block diagram showing the configuration of the steering control device that constitutes the steering device that is the vehicle steering device of the present embodiment. FIG. 10 is a diagram illustrating the relationship between the upper limit frequency in the constant gain region and the vehicle speed. FIG. 11 is a diagram illustrating the frequency characteristics of the compensator using the relationship between frequency and gain. FIG. 12 is a diagram showing the relationship between the steering angle θ _H and the steering reaction force T _H in two examples of the case where the vehicle speed is low and the case where the vehicle speed is high.

As shown in FIG. 9, the steering control device 14 a included in the steering apparatus of the present embodiment has a constant gain region upper limit setting unit 68, and detects a detection signal representing the vehicle speed V from the vehicle speed sensor 16 as a constant gain region upper limit. This is input to the setting unit 68. The constant gain region upper limit setting unit 68 sets the upper limit frequency ω _D of the constant gain regions 64a and 64b (FIG. 11) according to the vehicle speed V. In other words, map data representing the relationship between the vehicle speed V and the constant gain upper limit frequency ω _D as shown in FIG. 10 is stored in the storage unit of the steering control device 14. In the following description, the same elements as those shown in FIG.

As shown in FIG. 10, when the vehicle speed V is less than or equal to a certain value V1, the gain constant region upper limit frequency ω _D is set to a constant value, and the vehicle speed V is between V1 and V2 and the gain constant region upper limit is increased. Reduce frequency ω _D linearly. Further, the vehicle speed V is V2 or more, and the gain constant region upper limit frequency ω _D is set to a constant value. The constant gain region upper limit setting unit 68 reads map data representing the relationship between the vehicle speed V and the constant gain region 64 upper limit frequency ω _D from the storage unit, and searches the map from the vehicle speed V input from the vehicle speed sensor 16. Then, the gain constant region upper limit frequency ω _D is output to the compensator 60.

In the first embodiment, the compensator 60 has a transfer function C (s) expressed by the above equation (4) and a lower corner frequency according to the output of the constant gain region upper limit setting unit 68. However, the certain gain constant region upper limit frequency ω _D is changed according to the vehicle speed V. In this case, the intermediate corner frequency ω _N is a constant value regardless of the vehicle speed V. Therefore, when the vehicle speed V is between V1 and V2, the gain constant region upper limit frequency ω _D decreases as the vehicle speed V increases, and ω _N / ω _D increases.

Because of this configuration, the frequency characteristic of the compensator 60 is expressed as shown in FIG. In FIG. 11, the solid line P1 represents the case where the vehicle speed V is low, that is, the gain constant region upper limit frequency ω _DL is high, and the alternate long and short dash line P2 is that the vehicle speed V is high, that is, the gain constant region upper limit frequency ω _DH is higher than ω _DL . Represents a low case.

Further, in the case of the present embodiment, the constant gain region upper limit frequency ω _DL at the vehicle speed _VL is matched with the upper limit of the steering frequency band. However, the gain constant region upper limit frequency ω _DL can be set to a frequency higher than the upper limit of the steering frequency band. In any case, with this configuration, the gain G2 is constant even when the frequency changes in the steering frequency band. Further, when the vehicle speed V is low, the frequency band range of the constant gain region 64a is larger than when the vehicle speed V is high. Further, as shown in FIG. 11, the gain G1 in the constant gain region 64b when the vehicle speed V is high is higher than the gain G2 in the constant gain region 64a when the vehicle speed V is low (G1> G2).

  Thus, since the steering control device 14 changes the frequency band of the constant gain region 64 in the frequency characteristics of the compensator 60 according to the vehicle speed V, the angle deviation with respect to the target rotation angle changes according to the vehicle speed V of the vehicle. . For this reason, a feeling of rigidity can be changed according to the vehicle speed V. In addition, it is possible to suppress a change in the feeling of rigidity due to a change in the steering frequency at the same vehicle speed V.

Further, since the steering control device 14 sets the gain G1 in the constant gain region 64b when the vehicle speed V is high to be higher than the gain G2 in the constant gain region 64a when the vehicle speed V is low, the vehicle speed V of the vehicle is high. In this case, the angle deviation with respect to the target rotation angle can be reduced, and the rigidity can be increased. That is, as shown in FIG. 12, in the two examples with different vehicle speeds V, the relationship between the steering angle θ _H and the steering reaction force T _H is different. In FIG. 12, the case where the vehicle speed V is low is represented by a solid line L1, and the case where the vehicle speed V is high is represented by a broken line L2. Thus, when the vehicle speed V is low, whereas the rate of increase of the steering reaction force T _H to the steering angle theta _H is small when the vehicle speed V is high, the steering reaction force T _H to the steering angle theta _H The rate of increase of will increase. For this reason, when the vehicle speed V is high, the sense of rigidity when the steering handle 18 is steered can be further increased. Moreover, when the vehicle speed V is high, the practical upper limit of the steering frequency band is lower than when the vehicle speed V is low. The reason for this configuration is that when the vehicle speed V is high, the possibility that the steering handle 18 is steered at a high frequency is practically lower than when the vehicle speed V is low. For this reason, according to the present embodiment, when the vehicle speed V is high, the problem that the feeling of rigidity changes depending on the steering frequency in spite of the fact that the upper limit frequency ω _DH of the constant gain region 64b is low, It can be difficult to occur.

Further, when the vehicle speed V is low, the upper limit frequency of the steering frequency band is practically high, but in the present embodiment, in consideration thereof, the upper limit frequency ω _{DL of the} constant gain region 64a when the vehicle speed V is low. Therefore, practical problems can be hardly caused. Further, when the vehicle speed is low, is higher, in any case, regardless of the frequency of the steering in the vehicle speed V is constant, does not change the relationship of the steering reaction force T _H to the steering angle theta _H within the steering frequency band. Since other configurations and operations are the same as those in the first embodiment, the same parts are denoted by the same reference numerals, and overlapping illustrations and descriptions are omitted.

In the present embodiment, the relationship between the vehicle speed V and the constant gain region upper limit frequency ω _D is as shown in FIG. 10 when the vehicle speed V is V1 or less and when the vehicle speed V is V2 or more. Thus, the constant gain upper limit frequency ω _D is constant, but the present embodiment is not limited to such a configuration. For example, as represented by a one-dot chain line S in FIG. 10, the constant gain region upper limit frequency ω _D can be linearly decreased as the vehicle speed V increases in the entire range below the vehicle speed V3.

1 is a schematic configuration diagram of a steering device that is a vehicle steering device according to a first embodiment of the present invention. It is a schematic sectional drawing of the actuator which comprises the steering apparatus of FIG. It is a block diagram which shows the structure of the steering control apparatus which comprises the steering apparatus of FIG. It is a figure which shows the frequency characteristic of the compensator which comprises the steering control apparatus of FIG. 1 using the relationship between a frequency and a gain. (A) shows the time lapse of the steering angle θ _H when the steering wheel is reciprocated at a constant period in the steering device of the comparative example, (b) shows the time lapse of the actuator angle θ _A , and (c) shows the same. the time course of the steering reaction force T _H, illustrates respectively. In Comparative Example, a diagram showing the relation between the steering angle theta _H and the steering reaction force T _H. (A) is the time lapse of the steering angle θ _H when the steering wheel is reciprocated at a constant period in the steering device of the first embodiment, and (b) is the time lapse of the actuator angle θ _A ( the time course of c) is also the steering reaction force T _H, illustrates respectively. In the first embodiment, a diagram showing the relation between the steering angle theta _H and the steering reaction force T _H. It is a block diagram which shows the structure of the steering control apparatus which comprises the steering apparatus which is a steering apparatus for vehicles of the 2nd Embodiment of this invention. In 2nd Embodiment, it is a figure which shows the relationship between the upper limit frequency of a gain fixed area | region, and a vehicle speed. In 2nd Embodiment, it is a figure which shows the frequency characteristic of a compensator using the relationship between a frequency and a gain. In the second embodiment, the relationship between the steering angle theta _H and the steering reactive force T _H, illustrates by two examples of the case and when the vehicle speed is low high.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Steering device, 12 Steering force transmission mechanism, 14, 14a Steering control device, 16 Vehicle speed sensor, 18 Steering handle, 20 Input shaft, 22 Transmission ratio variable mechanism, 24 Output shaft, 26 Gear device, 28 Rack shaft, 30 Steering wheel , 32 Actuator, 34 Motor, 36 Wave gear device, 38 Motor housing, 40 Connecting member, 42 Rotating shaft, 44 Wave generator, 46 Flex spline, 48, 50 Circular spline, 52 Steering angle sensor, 54 Motor angle sensor, 56 Target actuator angle calculation unit, 58 detection actuator angle calculation means, 60 compensator, 62 motor drive circuit, 64, 64a, 64b constant gain region, 66 gain increase region, 68 constant gain region upper limit setting unit.

Claims (7)

A transmission ratio variable mechanism provided in a steering force transmission mechanism that connects the steering wheel and the steered wheel;
A control unit for controlling the operation of the transmission ratio variable mechanism,
The transmission ratio variable mechanism includes an actuator that adds an actuator angle to an input rotation angle by driving a motor to output an output rotation angle, and changes a transmission ratio between the input rotation angle and the output rotation angle.
The control unit includes a compensator, and controls driving of the motor according to a control deviation between the target actuator angle and the detected actuator angle.
The compensator outputs the target torque generated by the motor according to the control deviation input.
A vehicular steering apparatus characterized in that the frequency characteristic of the compensator has a gain increase region where the gain increases as the frequency decreases, and a gain constant region where the gain is constant in a frequency band lower than the gain increase region. The vehicle steering apparatus according to claim 1,
Steering angle detection means for detecting the steering angle of the steering wheel;
Motor rotation angle detection means for detecting the rotation angle of the motor, which is a relative rotation angle with respect to the steering angle of the steering wheel,
The control unit
Setting means for setting a target actuator angle according to the running state of the vehicle and the detected value of the steering angle;
And a detection actuator angle calculation means for calculating a detection actuator angle from a detection value of the rotation angle of the motor. The vehicle steering apparatus according to claim 2,
The setting device sets a target actuator angle according to an angle setting coefficient set by a detected value of a vehicle speed representing a running state of the vehicle and a detected value of a steering angle, and a vehicle steering apparatus. The vehicle steering apparatus according to any one of claims 1 to 3,
The actuator
A motor,
And a gear transmission that changes a gear ratio in accordance with a rotational angular velocity of the motor. The vehicle steering apparatus according to any one of claims 1 to 4, wherein:
A steering apparatus for a vehicle, wherein at least a part of the constant gain region is in a steering frequency band. In the vehicle steering device according to any one of claims 1 to 5,
The control unit changes the frequency band of the constant gain region in the frequency characteristics of the compensator in accordance with the vehicle speed. The vehicle steering apparatus according to claim 6,
The control unit is configured to make the gain in the constant gain region when the vehicle speed is high higher than the gain in the constant gain region when the vehicle speed is low.

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