Vehicle steering system control device

Abstract

To provide a vehicle steering system control device that can realize desired input-output transmission characteristics while suppressing deviation of a turning angle caused by disturbance from a road surface.SOLUTION: A vehicle steering system control device includes a turning angle control unit configured to generate, based on a turning angle target value as a target value of a turning angle of a turning wheel, a motor current command value as a control target value for a current supplied to a turning motor. The turning angle control unit includes: a feedforward compensation unit 710 configured to improve followability of the turning angle for the turning angle target value; a feedback compensation unit 720 configured to control the motor current command value based on a deviation between an output value of the feedforward compensation unit 710 and an actual turning angle θt_act; and a disturbance observer 730 configured to estimate a disturbance component d acting on an inertia system including the turning motor and to remove the disturbance component d from the motor current command value.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a control device for a steering system for a vehicle. [Background technology]

[0002] One type of vehicle steering system is the steer-by-wire (SBW) system, which mechanically separates a steering mechanism (Force Feedback Actuator: FFA) with a steering wheel operated by the driver from a road wheel actuator (Road Wheel Actuator: RWA) that steers the steered wheels. In an SBW system, the steering mechanism and the road wheel actuator are electrically connected via an electronic control unit (ECU). Steering wheel operation is transmitted to the road wheel actuator via an electrical signal to steer the steered wheels, and the road wheel actuator generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates a steering reaction force using a reaction actuator equipped with a reaction motor, and the road wheel actuator steers the steered wheels using a steering actuator equipped with a steering motor. The reaction actuator and the road wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction actuator is transmitted to the driver via the column shaft and the road wheel.

[0003] In SBW systems, where the steering mechanism and the turning mechanism are mechanically separated, it is necessary to suppress deviations in the turning angle caused by disturbances from the road surface. Patent Document 1 listed below discloses a configuration in which torque that affects the pinion angle is estimated as disturbance torque and converted into torque applied to the steering shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-203499 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional technology, the feedforward manipulated variable is calculated by multiplying the second-order time derivative of the pinion angle command value by the inertia coefficient. Since the inertia coefficient is generally a constant value, feedforward control may not be performed appropriately depending on the frequency, and it may not be possible to set appropriate input / output transfer characteristics.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control device for a vehicle steering system that can achieve desired input / output transmission characteristics while suppressing deviations in the steering angle caused by disturbances from the road surface. [Means for solving the problem]

[0007] In order to achieve the above object, a control device for a vehicle steering system according to one aspect of the present invention is a control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with the steering angle of a steering wheel, and comprises a steering angle control unit that generates a motor current command value that is a control target value of current to be supplied to the steering motor, based on a steering angle target value that is a target value for the steering angle of the steered wheels, and the steering angle control unit comprises a feedforward compensation unit that improves the tracking of the steering angle with respect to the steering angle target value, a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is the actual turning angle of the steered wheels, and a disturbance observer that estimates disturbance components acting on an inertial system including the steering motor and removes the disturbance components from the motor current command value.

[0008] According to the above configuration, deviations in the steering angle caused by disturbances from the road surface can be suppressed by the disturbance observer, and desired input / output transfer characteristics can be achieved by the feedforward compensation section.

[0009] In a desirable aspect of the control device for a vehicle steering system, when Gm is a target transfer characteristic of a control system that inputs the steering angle target value and outputs the actual steering angle, and Gref is a transfer characteristic of a control system that inputs an output value of the feedforward compensation unit and outputs the actual steering angle, it is preferable that the feedforward compensation unit outputs a value obtained by applying transfer characteristic Gm / Gref to the steering angle target value.

[0010] According to the above configuration, the transfer characteristic of the feedforward compensation unit can be set using the target transfer characteristic Gm to be realized in the steering angle control unit and the transfer characteristic Gref that can be derived by simulation, thereby improving the ability to follow the target transfer characteristic Gm realized in the steering angle control unit.

[0011] In a desirable aspect of the control device for a vehicle steering system, when Gm is a target transfer characteristic of a control system that inputs the steering angle target value and outputs the actual steering angle, Gref is a transfer characteristic of the control system that inputs the output value of the feedforward compensation unit and outputs the actual steering angle, and P is a transfer characteristic of the control system that inputs the output value of the feedback compensation unit and outputs the actual steering angle, it is preferable that the feedforward compensation unit outputs a first value to which the target transfer characteristic Gm is applied to the steering angle target value and outputs a second value to which transfer characteristic Gm / P is applied to the steering angle target value, the feedback compensation unit controls the motor current command value based on a deviation between the first value and the actual steering angle, and the disturbance observer controls the motor current command value based on a value obtained by adding the second value and the output value of the feedback compensation unit.

[0012] According to the above configuration, the transfer characteristic of the feedforward compensation unit can be set using the target transfer characteristic Gm to be realized in the steering angle control unit and the transfer characteristic P that can be derived by simulation. This makes it possible to improve the follow-up ability of the steering angle control unit to the target transfer characteristic Gm.

[0013] In a desirable aspect of the control device for a vehicle steering system, it is preferable that the disturbance observer includes a filter having predetermined high-frequency attenuation characteristics, generates an inverse model of the inertial system by applying the filter to the inverse characteristics of a plant model, which are the transfer characteristics of the inertial system, converts an output value of the disturbance observer into torque, subtracts the filtered value from a value obtained by multiplying the actual steering angle by the inverse model to calculate a torque estimate of the disturbance component, converts the torque estimate into a current to calculate a current estimate of the disturbance component, and removes a value obtained by multiplying the current estimate by a compensation gain from the output value of the feedback compensation unit to output the result as the motor current command value.

[0014] According to the above configuration, disturbances acting on the inertial system can be removed.

[0015] In a desirable aspect of the control device for a vehicle steering system, it is preferable that the disturbance observer includes a filter having predetermined high-frequency attenuation characteristics, generates an inverse model of a plant model which is the transfer characteristic of the inertial system, subtracts a value obtained by torque-converting an output value of the disturbance observer from a value obtained by multiplying the actual steering angle by the inverse model, calculates a torque estimate of the disturbance component by applying the filter, converts the torque estimate into a current to calculate a current estimate of the disturbance component, removes a value obtained by multiplying the current estimate by a compensation gain from the output value of the feedback compensation unit, and outputs the result as the motor current command value.

[0016] According to the above configuration, disturbances acting on the inertial system can be removed.

[0017] In a desirable aspect of the control device for a vehicle steering system, it is preferable that the disturbance observer includes a filter having predetermined high-frequency attenuation characteristics, converts the inverse characteristics of a plant model, which is the transfer characteristic of the inertial system, into a current, and further applies the filter to generate an inverse model of the inertial system, subtracts the value obtained by applying the filter to the output value of the disturbance observer from a value obtained by multiplying the actual steering angle by the inverse model to calculate a current estimated value of the disturbance component, and removes the value obtained by multiplying the current estimated value by a compensation gain from the output value of the feedback compensation unit to output it as the motor current command value.

[0018] According to the above configuration, disturbances acting on the inertial system can be removed.

[0019] In a desirable aspect of the control device for a vehicle steering system, it is preferable that the disturbance observer includes a filter having predetermined high-frequency attenuation characteristics, generates an inverse model of the inertial system by converting the inverse characteristics of a plant model, which is the transfer characteristic of the inertial system, into a current, subtracts the output value of the disturbance observer from a value obtained by multiplying the actual steering angle by the inverse model, applies the filter to calculate a current estimate of the disturbance component, removes a value obtained by multiplying the current estimate by a compensation gain from the output value of the feedback compensation unit, and outputs the result as the motor current command value.

[0020] According to the above configuration, disturbances acting on the inertial system can be removed.

[0021] In a preferred embodiment of the control device for a vehicle steering system, the feedback compensation unit is preferably configured by a PID controller.

[0022] In a preferred embodiment of the control device for a vehicle steering system, the feedback compensation unit is preferably configured as a PD controller. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a control device for a vehicle steering system that can realize desired input / output transfer characteristics while suppressing deviations in the steering angle caused by disturbances from the road surface. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing the hardware configuration of the ECU. [Figure 3] FIG. 3 is a diagram showing an example of a basic control block configuration of a control device in an SBW system. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of the steering angle control unit according to the embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a block diagram including a steering angle control unit and a controlled object. [Figure 6] FIG. 6 is a block diagram showing a modified example of the disturbance observer. [Figure 7] FIG. 7 is a Bode diagram showing an example of a target transfer characteristic realized in the steering angle control unit. [Figure 8] FIG. 8 is a diagram showing an example of a simplified block diagram of FIG. [Figure 9] FIG. 9 is a diagram showing a modification of the block diagram shown in FIG. [Figure 10] FIG. 10 is a diagram showing a modification of the block diagram shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0026] 1 is a block diagram showing an example of an outline of a SBW system equipped with a control device according to the present disclosure. The SBW system includes a reaction force device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

[0027] The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft (steering shaft, handle shaft) 2, which is found in general electric power steering devices, and instead transmits the driver's operation of the steering wheel 1 as an electrical signal, specifically the steering angle θh output from the reaction force device 30, as an electrical signal.

[0028] The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotational speed of the reaction force motor 31. The reaction force device 30 transmits the vehicle's motion state, which is transmitted from the steered wheels 5L, 5R, to the driver as a steering reaction force. The reaction force motor 31 applies the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

[0029] The reaction force device 30 further includes a steering angle sensor 33 and a torque sensor 34. The steering angle sensor 33 detects the steering angle θh of the steering wheel 1. The torque sensor 34 detects the steering torque Th of the steering wheel 1. Hereinafter, the steering angle θh detected by the steering angle sensor 33 will also be referred to as the "actual steering angle θh_act," and the steering torque Th detected by the torque sensor 34 will also be referred to as the "actual steering torque Th_act."

[0030] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point, which is the limit of possible steering, is provided on the column shaft 2. That is, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0031] The steering device 40 includes a steering motor 41, a speed reduction mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 44 that converts the rotational motion of the steering motor 41 into linear motion. The steering device 40 drives the steering motor 41 in accordance with the steering angle θh, and the resulting drive force is applied to the pinion rack mechanism 44 via the speed reduction mechanism 42, and the drive force is passed through the tie rods 3a and 3b to steer the steerable wheels 5L and 5R. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steerable wheels 5L and 5R. Instead of the steering angle θt of the steerable wheels 5L and 5R, for example, the motor angle of the steering motor 41 or the position of the rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 will also be referred to as the "actual steering angle θt_act."

[0032] In order to cooperatively control the reaction force device 30 and the steering device 40, the control device 50 generates a voltage control command value Vref1 for driving and controlling the reaction force motor 31 and a voltage control command value Vref2 for driving and controlling the steering motor 41 based on information such as the steering angle θh and the turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

[0033] The control device 50 is supplied with power from the battery 12 and receives an ignition key signal via the ignition key 11. A CAN (Controller Area Network) 20 that transmits and receives various vehicle information is also connected to the control device 50, and the vehicle speed Vs can also be received from the CAN 20. Furthermore, a non-CAN 21 that transmits and receives communications other than the CAN 20, analog / digital signals, radio waves, etc. can also be connected to the control device 50.

[0034] Specifically, the control device 50 is, for example, an ECU (Electronic Control Unit) mounted on a vehicle. The ECU is mainly composed of a CPU (including an MCU, an MPU, etc.). FIG. 2 is a schematic diagram showing the hardware configuration of the ECU. As shown in FIG. 2, the control device 50 includes a control computer (Electronic Control Unit, hereinafter also referred to as "ECU") 110.

[0035] ECU 110 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an EEPROM (Electrically Erasable Programmable ROM) 104, etc., which are connected to a bus 105. CPU 101 executes a control program stored in ROM 102. Reaction force device 30 and steering device 40 are cooperatively controlled by a control program executed mainly by ECU 110. Note that control device 50 may be configured as a single ECU, or may include a reaction force control ECU that controls reaction force device 30 and a steering control ECU that controls steering device 40.

[0036] The ROM 102 is used as a memory for storing the control program and control data used when the control program is executed, and the RAM 103 is used as a work memory for running the control program.

[0037] The EEPROM 104 is a nonvolatile memory that can retain its contents even after power is cut off, and stores control data and the like used by the CPU 101 to execute a control program. The various data stored in the EEPROM 104 is used in the control program loaded in the RAM 103 after power is turned on to the ECU 110, and is overwritten in the EEPROM 104 at a predetermined timing. Note that, although an EEPROM is used as the nonvolatile memory here, the present invention is not limited to this, and other nonvolatile memories such as a FLASH-ROM (registered trademark) or an SDRAM may also be used.

[0038] FIG. 3 is a diagram showing an example of a basic control block configuration of a control device for a SBW system. In FIG. 3, reaction force device 30 includes, in addition to reaction force motor 31 and the above-mentioned configuration, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. Furthermore, turning device 40 includes, in addition to turning motor 41 and the above-mentioned configuration, a PWM control unit 47, an inverter 48, and a motor current detector 49. Control device 50 implements the control blocks of reaction force control system 60, which controls reaction force device 30, and steering control system 70, which controls steering device 40. Reaction force control system 60 and steering control system 70 cooperate to control reaction force device 30 and steering device 40. Note that when control device 50 is configured to include a reaction force control ECU and a steering control ECU, reaction force control system 60 may be implemented by the reaction force control ECU, and steering control system 70 may be implemented by the steering control ECU. In this case, reaction force control system 60 in the following description may be read as a reaction force control ECU, and turning control system 70 may be read as a turning control ECU.

[0039] Each control block in reaction force control system 60 is realized by a reaction force control program executed in ECU 110. Also, each control block in turning control system 70 is realized by a turning control program executed in ECU 110. Note that some or all of the control blocks of control device 50 may be realized by hardware. Also, a mode in which control device 50 includes PWM control section 37, inverter 38, motor current detector 39, PWM control section 47, inverter 48, and motor current detector 49 may be used.

[0040] As shown in Fig. 3, control device 50 includes, as control blocks, steering torque target value generation section 200, road surface reaction force adaptive torque compensation value generation section 220, steering torque control section 400, current control section 500, turning angle target value generation section 600, turning angle control section 700, and current control section 800. Steering torque target value generation section 200, road surface reaction force adaptive torque compensation value generation section 220, steering torque control section 400, and current control section 500 are control blocks that make up reaction force control system 60. Turning angle target value generation section 600, turning angle control section 700, and current control section 800 are control blocks that make up steering control system 70.

[0041] The reaction force control system 60 performs control such that the actual steering torque Th_act detected by the torque sensor 34 follows the steering torque target value Th_ref, which is the target value of the steering torque of the reaction force device 30.

[0042] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0043] The steering torque control unit 400 generates a reaction force motor current command value Ih_ref, which is a control target value of the current to be supplied to the reaction force motor 31. The steering torque control unit 400 generates a current command value such that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero, and an output limiting unit limits the output of the current command value between upper and lower limits, thereby calculating the reaction force motor current command value Ih_ref.

[0044] The current control unit 500 controls the current of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the reaction force motor current command value Ih_ref output from the steering torque control unit 400 and the actual current value (motor current value) Ih_act of the reaction force motor 31 detected by the motor current detector 39 approaches zero.

[0045] In the reaction force device 30, the reaction force motor 31 is controlled and driven via a PWM control unit 37 and an inverter 38 based on the voltage control command value Vh_ref.

[0046] The steering control system 70 performs control such that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

[0047] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0048] Steering angle control unit 700 generates steering motor current command value It_ref, which is a control target value for the current supplied to steering motor 41. Steering angle control unit 700 calculates steering motor current command value It_ref so that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero. A more specific configuration example of the steering angle control unit according to the embodiment will be described later with reference to FIG. 4. In FIG. 3, some components of the specific configuration shown in FIG. 4 are omitted.

[0049] Current control unit 800 controls the current of steering motor 41. Current control unit 800 calculates a voltage control command value Vt_ref such that deviation It_err between steering motor current command value It_ref output from steering angle control unit 700 and actual current value (motor current value) It_act of steering motor 41 detected by motor current detector 49 approaches zero.

[0050] In the steering device 40, the steering motor 41 is controlled and driven via a PWM control unit 47 and an inverter 48 based on the voltage control command value Vt_ref.

[0051] In this embodiment, steering torque control section 400, current control section 500, turning angle target value generation section 600, turning angle control section 700 and current control section 800 may be configured in any way as long as they are able to realize the respective controls in reaction force control system 60 or turning control system 70, and are not limited by the configuration of each of these control blocks. Below, a specific configuration of turning angle control section 700 according to this embodiment will be described with reference to Fig. 4.

[0052] Fig. 4 is a block diagram showing an example of the configuration of a steering angle control unit according to the embodiment. As shown in Fig. 4, steering angle control unit 700 according to the present embodiment comprises, as main components, a feedforward (FF) compensation unit 710, a feedback (FB) compensation unit 720, and a disturbance observer 730.

[0053] Feedforward compensation section 710 is made up of a filter (FF filter) for improving the ability of actual turning angle θt_act to follow target turning angle value θt_ref. Feedforward compensation section 710 performs filter processing on target turning angle value θt_ref.

[0054] Feedback compensation section 720 is configured, for example, by a PID controller that performs PID control so that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero. Feedback compensation section 720 is not limited to a PID controller, and may be configured, for example, by a PD controller.

[0055] Disturbance observer 730 estimates disturbance components acting on the control target (Plant) of steering angle control section 700 and removes them from the output value of feedback compensation section 720. Plant shown in FIG.

[0056] FIG. 5 is a diagram showing an example of a block diagram including a steering angle control unit and a controlled object. A plant model, which is a transfer characteristic of the plant, can be expressed by the following equation (1). In the following equation (1), J t denotes the inertia coefficient of the plant, and C tindicates the viscosity coefficient of Plant.

[0057] 1 / (J t s 2 +C t s)···(1)

[0058] The disturbance observer 730 includes a second-order LPF (Low Pass Filter). The transfer characteristic of the LPF is expressed by the following equation (2).

[0059] 1 / (T d s+1) 2 ···(2)

[0060] In the LPF having the transfer characteristic shown in the above equation (2), it is possible to adjust the disturbance compensation band in the disturbance observer 730. Specifically, by increasing the cutoff frequency, it is possible to widen the disturbance compensation band to the high frequency side.

[0061] In the example shown in FIG. 5, the disturbance observer 730 calculates the inverse characteristic J of the plant model shown in the above equation (1). t s 2 +C t s, the LPF with the transfer characteristic shown in the above equation (2) is applied to the inverse model of Plant (J t s 2 +C t s) / (T d s+1) 2Disturbance observer 730 converts the output value by multiplying it by coefficient Kt, and then subtracts the value obtained by applying an LPF with the transfer characteristics shown in equation (2) above from the value obtained by multiplying actual steering angle θt_act by the inverse model of Plant to calculate a torque estimate value Td_est of the disturbance component. Disturbance torque estimate value Td_est is then divided by coefficient Kt to perform current conversion to calculate a current estimate value Id_est of the disturbance component, and current estimate value Id_est is multiplied by compensation gain Kobs and subtracted from output value It_ref0 of feedback compensation section 720 to output the result It_ref0-Kobs×Id_est as steering motor current command value It_ref. Note that compensation gain Kobs is set to a value between 0 and 1. The order of the LPF is not limited to second order, and any LPF of second order or higher having predetermined high-frequency attenuation characteristics will suffice. Furthermore, by using an LPF with a second-order or higher transfer characteristic, the components within the disturbance compensation band of the Plant inverse model can be optimized.

[0062] FIG. 6 is a block diagram showing a modified example of the disturbance observer. In the modified example shown in FIG. t ' and C t ' can be expressed by the following equations (3) and (4), respectively.

[0063] J t '=J t / Kt···(3)

[0064] C t '=C t / Kt···(4)

[0065] The disturbance observer 730a calculates the inverse characteristic J of the plant model shown in the above equation (1). t s 2 +C t s is converted into a current using the above equations (3) and (4), and then an LPF with the transfer characteristics shown in the above equation (2) is applied to obtain the inverse model of Plant (J t s 2 +C t s) / (T d s+1) 2Disturbance observer 730a calculates a current estimate value Id_est of the disturbance component by subtracting a value obtained by applying an LPF with the transfer characteristic shown in equation (2) above to the output value from a value obtained by multiplying actual turning angle θt_act by the Plant inverse model, and then multiplies current estimate value Id_est by compensation gain Kobs and outputs the result It_ref0-Kobs×Id_est, which is removed from output value It_ref0 of feedback compensation section 720, as turning motor current command value It_ref.

[0066] The disturbance component d acting on the Plant can be removed by the disturbance observers 730 and 730a described above. Note that the configurations of the disturbance observers 730 and 730a shown in Figures 5 and 6 are merely examples, and the present invention is not limited to these.

[0067] Fig. 7 is a Bode diagram showing an example of a target transfer characteristic realized in the steering angle control unit. Fig. 7 shows a second-order LPF characteristic as an example of the target transfer characteristic Gm, which is a target value of the transfer characteristic of a control system that inputs the steering angle target value θt_ref and outputs the actual steering angle θt_act. The cutoff frequency fc in the target transfer characteristic Gm is set to, for example, about 5 [Hz] to 15 [Hz].

[0068] Figure 8 is a diagram showing an example of a block diagram that simplifies Figure 5. In the following description, the transfer characteristic of feedforward compensation section 710 is defined as Gff, the transfer characteristic of feedback compensation section 720 as Gfb, the transfer characteristic of a control system that inputs output value θt_ref0 of feedforward compensation section 710 and outputs actual steering angle θt_act as Gref, and the transfer characteristic of the control system that inputs output value It_ref0 of feedback compensation section 720 and outputs actual steering angle θt_act as P. Transfer characteristic Gref and transfer characteristic P can be derived by simulation.

[0069] The transfer characteristic Gff of the feedforward compensation unit 710 can be expressed by the following equation (5) which is indicated by the target transfer characteristic Gm and the transfer characteristic Gref which can be derived by simulation.

[0070] Gff=Gm / Gref (5)

[0071] On the other hand, when the transfer characteristic of the control system having the steering angle target value θt_ref as an input and the actual steering angle θt_act as an output is defined as Gref', the transfer characteristic Gref' is equivalent to the target transfer characteristic Gm, as shown in the following equation (6).

[0072] Gref'=Gff×Gref=(Gm / Gref)×Gref=Gm...(6)

[0073] That is, in the block diagram shown in FIG. 8, feedforward compensation section 710 outputs a value θt_ref0 obtained by applying the transfer characteristic shown in equation (5) above to steering angle target value θt_ref, and feedback compensation section 720 performs control based on the deviation θt_err between output value θt_ref0 of feedforward compensation section 710 and actual steering angle θt_act.

[0074] 8 and the above-described formula (5), the transfer characteristic of feedforward compensation section 710 can be set using target transfer characteristic Gm to be realized in steering angle control section 700 and transfer characteristic Gref that can be derived by simulation. This makes it possible to improve the ability to follow target transfer characteristic Gm realized in steering angle control section 700.

[0075] The transfer characteristic Gref can be expressed by the following equation (7).

[0076] Gref=Gfb×P / (1+Gfb×P)···(7)

[0077] Applying the above formula (7) to the above formula (5) gives the following formula (8).

[0078] Gff=Gm(1+Gfb) / Gfb×P=Gm / Gfb×P+Gm...(8)

[0079] Therefore, the block diagram shown in Fig. 8 can be expressed as Fig. 9. Fig. 9 is a diagram showing a modification of the block diagram shown in Fig. 8.

[0080] In the block diagram shown in Fig. 9, the transfer characteristic Gfb of the feedback compensation unit 720 is included in the transfer characteristic of the feedforward compensation unit 710. Here, when the block diagram shown in Fig. 9 is modified, it can be expressed as shown in Fig. 10. Fig. 10 is a diagram showing a modified example of the block diagram shown in Fig. 9.

[0081] In the modified example shown in FIG. 10, the input / output characteristics of a control system that inputs target steering angle value θt_ref and outputs output value It_ref0 of feedback compensation section 720 can be expressed by the following equations (9) to (13).

[0082] It_ref0 =It_ref1+It_ref2 (9)

[0083] It_ref1=(Gm / P)×θt_ref···(10)

[0084] It_ref2=Gfb×(θt_ref1-θt_act)···(11)

[0085] θt_ref1=Gm×θt_ref (12)

[0086] It_ref0 =(Gm / P)×θt_ref+Gfb×(Gm×θt_ref-θt_act) ···(13)

[0087] 10, feedforward compensation section 710a outputs value θt_ref1 (first value) obtained by applying target transfer characteristic Gm to steering angle target value θt_ref, and feedback compensation section 720a performs control based on deviation θt_err between output value θt_ref1 (first value) of feedforward compensation section 710a and actual steering angle θt_act. Also, feedforward compensation section 710a outputs value It_ref1 (second value) obtained by applying transfer characteristic Gm / P to steering angle target value θt_ref, and disturbance observer 730 (730a) performs control based on value It_ref0 obtained by adding output value It_ref1 (second value) of feedforward compensation section 710a and output value It_ref2 of feedback compensation section 720a.

[0088] 10 and the above equations (9) to (13), the transfer characteristic of feedforward compensation section 710a can be set using target transfer characteristic Gm to be realized in steering angle control section 700 and transfer characteristic P that can be derived by simulation. This makes it possible to improve the ability to follow target transfer characteristic Gm realized in steering angle control section 700.

[0089] It should be noted that the drawings used in the above-described embodiments are conceptual diagrams for qualitatively explaining the present disclosure, and are not intended to be limiting. Furthermore, while the above-described embodiment is an example of a preferred embodiment of the present disclosure, the present disclosure is not limited thereto, and various modifications can be made within the scope of the gist of the present disclosure. [Explanation of symbols]

[0090] 1 handle 2 column axis 3a, 3b tie rod 5L,5R steered wheels 10 Vehicle speed sensor 11 Ignition key 12 Battery 30 Reaction Device 31 Reaction motor 32 Reduction mechanism 33 Steering angle sensor 34 Torque sensor 35 Stopper (rotation limiting mechanism) 40 Steering gear 41 Steering motor 42 Reduction mechanism 43 Angle Sensor 44 Pinion rack mechanism 50 Control device 60 Reaction Force Control System 70 Steering control system 101 CPU(Central Processing Unit) 102 ROM (Read Only Memory) 103 RAM (Random Access Memory) 104 EEPROM (Electrically Erasable Programmable ROM) 105 Bus 110 ECU 200 Steering torque target value generation unit 400 Steering torque control unit 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 710,710a Feedforward compensation section 720, 720a Feedback compensation section 730,730a Disturbance observer 800 Current control section

Claims

1. A control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with a steering angle of a steering wheel, a steering angle control unit that generates a motor current command value that is a control target value of a current to be supplied to the steering motor based on a steering angle target value that is a target value of the steering angle of the steered wheels, The steering angle control unit a feedforward compensation unit for improving the tracking of the steering angle with respect to the target steering angle value; a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is an actual steering angle of the steered wheels; a disturbance observer that estimates a disturbance component acting on an inertial system including the steering motor and removes the disturbance component from the motor current command value; Equipped with When the target transfer characteristic of the control system that inputs the steering angle target value and outputs the actual steering angle is Gm, the transfer characteristic of the control system that inputs the output value of the feedforward compensation unit and outputs the actual steering angle is Gref, and the transfer characteristic of the control system that inputs the output value of the feedback compensation unit and outputs the actual steering angle is P, The feedforward compensation unit outputting a first value to which the target transfer characteristic Gm is applied to the steering angle target value, and outputting a second value to which a transfer characteristic Gm / P is applied to the steering angle target value; The feedback compensation unit controlling the motor current command value based on a deviation between the first value and the actual steering angle; The disturbance observer controlling the motor current command value based on a value obtained by adding the second value and the output value of the feedback compensation unit; A control device for a vehicle steering system.

2. A control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with a steering angle of a steering wheel, a steering angle control unit that generates a motor current command value that is a control target value of a current to be supplied to the steering motor based on a steering angle target value that is a target value of the steering angle of the steered wheels, The steering angle control unit a feedforward compensation unit for improving the tracking of the steering angle with respect to the target steering angle value; a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is an actual steering angle of the steered wheels; a disturbance observer that estimates a disturbance component acting on an inertial system including the steering motor and removes the disturbance component from the motor current command value; Equipped with The disturbance observer a filter having a predetermined high-frequency attenuation characteristic; applying the filter to the inverse characteristics of a plant model, which is a transfer characteristic of the inertial system, to generate an inverse model of the inertial system; converting an output value of the disturbance observer into a torque, and further subtracting the filtered value from a value obtained by multiplying the actual steering angle by the inverse model to calculate a torque estimation value of the disturbance component; converting the torque estimation value into a current to calculate a current estimation value of the disturbance component; a value obtained by multiplying the current estimation value by a compensation gain is removed from the output value of the feedback compensation unit, and the result is output as the motor current command value; A control device for a vehicle steering system.

3. A control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with a steering angle of a steering wheel, a steering angle control unit that generates a motor current command value that is a control target value of a current to be supplied to the steering motor based on a steering angle target value that is a target value of the steering angle of the steered wheels, The steering angle control unit a feedforward compensation unit for improving the tracking of the steering angle with respect to the target steering angle value; a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is an actual steering angle of the steered wheels; a disturbance observer that estimates a disturbance component acting on an inertial system including the steering motor and removes the disturbance component from the motor current command value; Equipped with The disturbance observer a filter having a predetermined high-frequency attenuation characteristic; generating an inverse model of a plant model that is a transfer characteristic of the inertial system; a value obtained by converting the output value of the disturbance observer into a torque value is subtracted from a value obtained by multiplying the actual steering angle by the inverse model, and the filter is further applied to calculate a torque estimation value of the disturbance component; converting the torque estimation value into a current to calculate a current estimation value of the disturbance component; a value obtained by multiplying the current estimation value by a compensation gain is removed from the output value of the feedback compensation unit, and the result is output as the motor current command value; A control device for a vehicle steering system.

4. A control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with a steering angle of a steering wheel, a steering angle control unit that generates a motor current command value that is a control target value of a current to be supplied to the steering motor based on a steering angle target value that is a target value of the steering angle of the steered wheels, The steering angle control unit a feedforward compensation unit for improving the tracking of the steering angle with respect to the target steering angle value; a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is an actual steering angle of the steered wheels; a disturbance observer that estimates a disturbance component acting on an inertial system including the steering motor and removes the disturbance component from the motor current command value; Equipped with The disturbance observer a filter having a predetermined high-frequency attenuation characteristic; converting the inverse characteristics of a plant model, which is the transfer characteristics of the inertial system, into a current, and then applying the filter to generate an inverse model of the inertial system; a value obtained by applying the filter to the output value of the disturbance observer, and subtracting the result from a value obtained by multiplying the actual steering angle by the inverse model to calculate a current estimate value of the disturbance component; a value obtained by multiplying the current estimation value by a compensation gain is removed from the output value of the feedback compensation unit, and the result is output as the motor current command value; A control device for a vehicle steering system.

5. A control device for a vehicle steering system equipped with a steering motor that steers steered wheels in accordance with a steering angle of a steering wheel, a steering angle control unit that generates a motor current command value that is a control target value of a current to be supplied to the steering motor based on a steering angle target value that is a target value of the steering angle of the steered wheels, The steering angle control unit a feedforward compensation unit for improving the tracking of the steering angle with respect to the target steering angle value; a feedback compensation unit that controls the motor current command value based on a deviation between an output value of the feedforward compensation unit and an actual steering angle that is an actual steering angle of the steered wheels; a disturbance observer that estimates a disturbance component acting on an inertial system including the steering motor and removes the disturbance component from the motor current command value; Equipped with The disturbance observer a filter having a predetermined high-frequency attenuation characteristic; converting the inverse characteristics of a plant model, which is a transfer characteristic of the inertial system, into a current to generate an inverse model of the inertial system; subtracting an output value of the disturbance observer from a value obtained by multiplying the actual steering angle by the inverse model, and further applying the filter to calculate a current estimate value of the disturbance component; a value obtained by multiplying the current estimation value by a compensation gain is removed from the output value of the feedback compensation unit, and the result is output as the motor current command value; A control device for a vehicle steering system.

6. When the target transfer characteristic of a control system that receives the target steering angle value as an input and outputs the actual steering angle is Gm, and the transfer characteristic of the control system that receives the output value of the feedforward compensation unit as an input and outputs the actual steering angle is Gref, The feedforward compensation unit a value obtained by applying a transfer characteristic Gm / Gref to the steering angle target value; The control device for a vehicle steering system according to any one of claims 2 to 5.

7. When the target transfer characteristic of the control system that inputs the steering angle target value and outputs the actual steering angle is Gm, the transfer characteristic of the control system that inputs the output value of the feedforward compensation unit and outputs the actual steering angle is Gref, and the transfer characteristic of the control system that inputs the output value of the feedback compensation unit and outputs the actual steering angle is P, The feedforward compensation unit outputting a first value to which the target transfer characteristic Gm is applied to the steering angle target value, and outputting a second value to which a transfer characteristic Gm / P is applied to the steering angle target value; The feedback compensation unit controlling the motor current command value based on a deviation between the first value and the actual steering angle; The disturbance observer controlling the motor current command value based on a value obtained by adding the second value and the output value of the feedback compensation unit; The control device for a vehicle steering system according to any one of claims 2 to 5.

8. The feedback compensation unit is configured with a PID controller. The control device for a vehicle steering system according to any one of claims 1 to 5.

9. The feedback compensation unit is configured with a PD controller. The control device for a vehicle steering system according to any one of claims 1 to 5.

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