Vehicle steering system control device

Abstract

To provide a control device for a vehicle steering system capable of conveying appropriate self-aligning-torque (SAT) feeling to a driver.SOLUTION: A control device for a vehicle steering system controls a reaction force device for applying torque to a steering member by using a reaction force actuator, and a turning device for turning a turning member by using a turning actuator. The control device for the vehicle steering system comprises: a target steering torque generation section for generating a basic target steering torque on the basis of at least a steering angle of the steering member; and a self-aligning torque correction section for calculating a corrected target steering torque. The self-aligning torque correction section comprises: a self-aligning torque estimation section for calculating a self-aligning torque estimated value by using at least a turning angle of the turning member and a rotation angle of the turning actuator; and a correction value determination section for determining the corrected target steering torque from the self-aligning torque estimated value. The control device for the vehicle steering system calculates a steering current command value for drive-controlling the reaction force actuator on the basis of the basic target steering torque and the corrected target steering torque.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control device for a vehicle steering system such as a steer-by-wire (SBW) system in which a steering mechanism and a turning mechanism are mechanically separated, and more particularly to a control device for a vehicle steering system that controls a reaction force device that applies a steering reaction force and a turning device that steers steered wheels. [Background technology]

[0002] One of the vehicle steering systems is the steer-by-wire (SBW) system, in which a steering mechanism connected to a steering wheel, which is a steering member operated by the driver, and a steering mechanism that steers the steered wheels, which are steered members, are mechanically separated. In the SBW system, the operation of the steering wheel is transmitted to a steering device, which is a steering mechanism, by an electric signal to steer the steered wheels, and a steering reaction force to give the driver an appropriate steering feel is generated by a reaction device, which is a steering mechanism. The reaction device generates a steering reaction force by a reaction motor, and the steering device steers the steered wheels by a steering motor. The reaction device and the steering wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction device is transmitted to the driver via the column shaft and the steering wheel.

[0003] In the SBW system, a system has been proposed in which a reaction force corresponding to the self-aligning torque (SAT) is added to the steering reaction force generated by the reaction force device so that a feeling caused by the self-aligning torque (SAT) (hereinafter referred to as "SAT feeling") is conveyed to the driver in order to convey road surface information during driving to the driver as a steering feeling. For example, International Publication No. 2019 / 167661 (Patent Document 1) proposes an SBW system that applies torsion angle control to control the torsion angle of the torsion bar to follow a value corresponding to the steering angle, etc., in order to provide an appropriate steering torque based on the driver's steering feeling. In this SBW system, a target steering torque, which is a target value of the steering torque, is generated according to the steering angle of the steering wheel, a target torsion angle, which is a target value of the torsion angle, is obtained based on the target steering torque, a motor current command value is calculated by feedback control based on the target torsion angle and the torsion angle, and the reaction motor is driven and controlled by the motor current command value. In order to convey the SAT feeling to the driver, the SAT is estimated from the steering angle of the steered wheels, etc., and a torque signal calculated from the estimated SAT is added to the target steering torque. The steered wheels are driven by applying the driving force of a drive motor (steered motor) to a pinion rack mechanism via a gear, and the SAT is estimated based on an equation of motion derived from the balance of torque generated around a shaft (pinion shaft) that connects the gear and the pinion rack mechanism during this driving. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167661 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in the SBW system of Patent Document 1, the SAT is estimated based on the equation of motion related to the torque generated around the pinion shaft. However, when the drive motor is driven, torque acts on the mechanical structure between the motor drive shaft and the pinion shaft of the drive motor (for example, a reduction mechanism such as a worm gear), which may cause deformation of the mechanical structure between the motor drive shaft and the pinion shaft. Since the SAT estimation in Patent Document 1 does not take such deformation of the mechanical structure into consideration, the torque generated by the drive motor may affect the SAT estimation. In particular, gear backlash, torsion between the motor drive shaft and the pinion shaft, etc. may affect the SAT estimation via the generated torque.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for a vehicle steering system that can convey an appropriate SAT feeling to the driver. [Means for solving the problem]

[0007] The present invention relates to a control device for a vehicle steering system that controls a reaction force device that applies torque to a steering member using a reaction force actuator, and a steering device that steers the steering member using a steering actuator, and the above object of the present invention is achieved by comprising a target steering torque generation unit that generates a basic target steering torque based on at least the steering angle of the steering member, and a self-aligning torque correction unit that calculates a corrected target steering torque, the self-aligning torque correction unit including a self-aligning torque estimating unit that calculates a self-aligning torque estimated value using at least the steering angle of the steering member and the rotational angle of the steering actuator, and a correction value determination unit that determines the corrected target steering torque from the self-aligning torque estimated value, and calculating a steering current command value for driving and controlling the reaction force actuator, based on the basic target steering torque and the corrected target steering torque.

[0008] The above object of the present invention is to provide a steering control unit which calculates a steering current command value for controlling the driving of the steering actuator in accordance with the steering angle, and the self-aligning torque estimating unit calculates the self-aligning torque estimated value by using the steering angle, the rotation angle, and steering drive information related to drive control of the steering actuator, or the self-aligning torque estimating unit calculates the self-aligning torque estimated value by using a first viscous torque calculated from the steering angular velocity calculated from the steering angle, a first inertia torque calculated from the steering angular acceleration calculated from the steering angular velocity, a second viscous torque calculated from the rotation angular velocity calculated from the rotation angle, a second inertia torque calculated from the rotation angular acceleration calculated from the rotation angular velocity, and an actuator torque calculated from the steering drive information, or the self-aligning torque estimating unit calculates the self-aligning torque estimated value by using a first viscous torque calculated from the steering angular velocity calculated from the steering angle, a first inertia torque calculated from the steering angular acceleration calculated from the rotation angular velocity, and an actuator torque calculated from the steering drive information, or the self-aligning torque estimating unit uses the steering current command value or a value of a current supplied to the steering actuator as the steering drive information, or the self-aligning torque estimating unit calculates the self-aligning torque estimated value by using a first viscous torque calculated from the steering angular velocity calculated from the steering angle, a first inertia torque calculated from the steering angular acceleration calculated from the rotation angular velocity, and an actuator torque calculated from the steering drive information, the self-aligning torque estimation unit calculates the self-aligning torque estimated value using a steering angle and the rotation angle, or the self-aligning torque estimating unit calculates the self-aligning torque estimated value using a viscous torque calculated from a steering angular velocity calculated from the steering angle, an inertia torque calculated from a steering angular acceleration calculated from the steering angular velocity, and a drive torque calculated based on a difference between the steering angle and the rotation angle, or the correction value determination unit has a characteristic that as the magnitude of the self-aligning torque estimated value increases, the magnitude of the corrected target steering torque increases and the rate at which the magnitude of the corrected target steering torque increases decreases, or the characteristic of the correction value determination unit changes according to a vehicle speed, or the self-aligning torque correction unit further includes a filter processing unit that reduces noise included in the self-aligning torque estimated value and inputs the self-aligning torque estimated value with the noise reduced to the correction value determination unit, or the reaction force device has a torsion bar,This can be more effectively achieved by further providing a conversion unit that converts the target steering torque calculated from the basic target steering torque and the corrected target steering torque into a target torsion angle, and a torsion angle control unit that calculates the steering current command value so that the torsion angle of the torsion bar follows the target torsion angle. Effect of the Invention

[0009] According to the control device for a vehicle steering system of the present invention, the SAT is estimated using the rotational angle of the steering actuator in addition to the steering angle of the steering member, thereby improving the accuracy of SAT estimation and enabling an appropriate SAT feeling to be conveyed to the driver. [Brief description of the drawings]

[0010] [Figure 1] 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to the present invention. [Diagram 2] FIG. 4 is a structural diagram showing an example of the arrangement of various sensors on a column shaft. [Diagram 3] 1 is a block diagram showing a configuration example (first embodiment) of the present invention. [Figure 4] 4 is a block diagram showing an example of the configuration of a target steering torque generating unit; FIG. [Diagram 5] 4A and 4B are diagrams illustrating an example of the configuration of a base map section and an example of characteristics of a base map. [Figure 6] FIG. 4 is a diagram showing an example of a characteristic of a damper gain map. [Figure 7] FIG. 2 is a diagram for explaining steering further / returning. [Figure 8] 11 is a diagram showing an example of characteristics of a hysteresis correction unit. FIG. [Figure 9] 4 is a block diagram showing a configuration example of a SAT correction unit. [Figure 10] 1 is an image diagram showing torque generated around a pinion shaft and a motor drive shaft. FIG. [Figure 11] 3 is a block diagram showing a configuration example (first embodiment) of a SAT estimation unit. FIG. [Figure 12] FIG. 4 is a diagram showing an example of a characteristic of a correction value map. [Figure 13] FIG. 4 is a block diagram showing a configuration example of a torsion angle control unit. [Figure 14] FIG. 2 is a block diagram showing a part of a configuration example of the present invention when a three-phase brushless motor is used. [Figure 15] 4 is a block diagram showing an example of the configuration of a target steering angle generating unit; FIG. [Figure 16] 13 is a diagram showing an example of setting upper and lower limit values ​​in a limiting section. FIG. [Figure 17] 4 is a flowchart showing an operation example (first embodiment) of the present invention. [Figure 18] 5 is a flowchart showing an example of the operation of a target steering torque generating unit. [Figure 19] 13 is a flowchart showing an operation example of a SAT correction unit. [Figure 20] 5 is a flowchart showing an example of the operation of a target steering angle generating unit. [Figure 21] 11 is a block diagram showing an example of inserting a phase compensation unit; FIG. [Figure 22] FIG. 13 is a block diagram showing a configuration example (second embodiment) of a SAT estimation unit. [Diagram 23] FIG. 4 is a diagram showing an example of a characteristic of a torque determination map. [Figure 24] FIG. 11 is a block diagram showing a configuration example (third embodiment) of the present invention. [Diagram 25] FIG. 13 is a block diagram showing a configuration example (fourth embodiment) of the present invention. [Figure 26] 13 is a flowchart showing a part of an operation example (fourth embodiment) of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention is a control device for a vehicle steering system that controls a reaction device and a steering device, and in order to add a reaction force corresponding to a self-aligning torque (SAT) to the steering reaction force generated by the reaction device, a corrected target steering torque obtained from an estimated value of the SAT is added to a basic target steering torque generated based on at least a steering angle. Then, the SAT is estimated using at least the steering angle of the steering member and the rotation angle of the steering actuator based on an equation of motion around a pinion shaft in the steering device and an equation of motion around a drive shaft of the steering actuator. In the SAT estimation, steering drive information, which is information related to the drive control of the steering actuator, can also be used. In this way, by estimating the SAT using the steering angle and the rotation angle, the accuracy of the SAT estimation is improved, and an appropriate SAT feeling can be created as road surface information. By creating the SAT feeling, the feeling when slipping while driving on a low μ road such as a rainy road surface or an icy road surface can be conveyed as a steering feeling. In other words, the understeer state can be conveyed to the driver.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] First, a configuration example of an SBW system including a control device according to the present invention will be described.

[0014] Fig. 1 is a diagram showing an example of the configuration of an SBW system. The SBW system includes a reaction device 30 constituting a steering mechanism having a steering wheel which is a steering member operated by the driver, a steering device 40 constituting a steering mechanism which steers the steered wheels which are steered members, and a control device 50 which controls both devices. The SBW system does not have an intermediate shaft which is mechanically connected to a column shaft (steering shaft, handle shaft) 2 which is provided in a general electric power steering device, and instead transmits the operation of the steering wheel 1 by the driver as an electric signal, specifically, the steering angle θh output from the reaction device 30 as an electric signal.

[0015] The reaction force device 30 includes a reaction force motor 31 and a speed reducing mechanism 32 that reduces the rotational speed of the reaction force motor 31, and transmits the vehicle's motion state transmitted from the steered wheels 5L, 5R to the driver as a reaction force (torque) generated by the reaction force motor 31. The reaction force device 30 further includes a steering angle sensor 33 and an angle sensor 34 that are provided on the column shaft 2. The steering angle sensor 33 and the angle sensor 34 are specifically disposed on the column shaft 2 as shown in Fig. 2. That is, the steering angle sensor 33 is provided on the upper part of the column shaft 2, and detects the steering angle θh. A torsion bar 2A is inserted in the column shaft 2, and an upper angle sensor 34A is provided on the steering wheel 1 side of the column shaft 2 with the torsion bar 2A in between, and a lower angle sensor 34B is provided on the opposite side of the column shaft 2 to the steering wheel 1 with the torsion bar 2A in between, as angle sensors 34, with the upper angle sensor 34A detecting a steering wheel angle θ1 and the lower angle sensor 34B detecting a column angle θ2. The steering wheel angle θ1 and the column angle θ2 are input to a torsion angle calculation unit 35, which calculates a torsion angle Δθ of the torsion bar using the following equation 1.

[0016]

number

[0017] The steering device 40 includes a steering motor 41, a speed reducing mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 45 that converts the rotational motion into linear motion, and the speed reducing mechanism 42 and the pinion rack mechanism 45 are connected by a pinion shaft 43. The steering motor 41 is driven in accordance with changes in the steering angle θh, and the driving force is applied to the pinion rack mechanism 45 via the speed reducing mechanism 42 and the pinion shaft 43, and the steered wheels 5L, 5R are steered via the tie rods 3a, 3b. A rotation angle sensor 46 is disposed near the steering motor 41 and detects the motor angle (rotation angle) θm of the steering motor 41. An angle sensor 44 is disposed near the pinion rack mechanism 45 and detects the steering angle θt of the steered wheels 5L, 5R. The position of the rack or the like may be used as the steering angle θt. Also, a ball screw mechanism or the like may be used instead of the pinion rack mechanism as a mechanism for converting the rotational motion of steering motor 41 into linear motion. The steering actuator is made up of steering motor 41, reduction mechanism 42, etc., but only steering motor 41 may be called the steering actuator.

[0018] In order to cooperatively control the reaction force device 30 and the turning 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 turning 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. 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 information about the vehicle is 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.

[0019] The control device 50 has a CPU (including an MCU, an MPU, etc.), and the cooperative control of the reaction force device 30 and the steering device 40 is mainly executed by a program inside the CPU. An example of a configuration for performing the control (first embodiment) is shown in FIG. 3. In FIG. 3, the reaction force device 30 is equipped with a reaction force motor 31, a steering angle sensor 33, an angle sensor 34, a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39, the steering device 40 is equipped with a steering motor 41, an angle sensor 44, a rotation angle sensor 46, a PWM control unit 47, an inverter 48, and a motor current detector 49, and the other components are realized by the control device 50. Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may be equipped with a RAM (random access memory), a ROM (read only memory), etc., for storing data, programs, etc. Furthermore, the control device 50 may include some or all of the PWM control unit 37, the inverter 38, the motor current detector 39, the PWM control unit 47, the inverter 48, and the motor current detector 49.

[0020] The control device 50 has a configuration for controlling the reaction device 30 (hereinafter referred to as the "reaction force control system") and a configuration for controlling the steering device 40 (hereinafter referred to as the "steering control system"), and the reaction force control system 60 and the steering control system 70 work together to control the reaction device 30 and the steering device 40.

[0021] The reaction force control system 60 includes a target steering torque generating unit 100, an SAT correcting unit 200, a past value holding unit 250, a converting unit 300, a torsion angle control unit 400, a current control unit 500, an adding unit 510, and a subtracting unit 520, and performs control so that the torsion angle of the torsion bar 2A follows the target torsion angle. The target steering torque generating unit 100 generates a basic target steering torque TrefA based on the steering angle θh and the vehicle speed Vs, and the SAT correcting unit 200 estimates the SAT to obtain a corrected target steering torque TrefB. The adding unit 510 adds the basic target steering torque TrefA and the corrected target steering torque TrefB, and outputs the result as the target steering torque Tref. The target steering torque Tref is converted into a target torsion angle Δθref by the converting unit 300. The target torsion angle Δθref is input to a torsion angle control unit 400 together with the torsion angle Δθ, and the torsion angle control unit 400 calculates a steering current command value Imc such that the torsion angle Δθ becomes the target torsion angle Δθref. Then, a subtraction unit 520 calculates a deviation I1 (=Imc-Imr) between the steering current command value Imc and the current value (motor current value) Imr of the reaction force motor 41 detected by a motor current detector 39, and a current control unit 500 determines a voltage control command value Vref1 based on the deviation I1. In the reaction force device 30, the reaction force motor 31 is driven and controlled via a PWM control unit 37 and an inverter 38 based on the voltage control command value Vref1.

[0022] Steering control system 70 comprises target steering angle generation section 600, steering angle control section 700, current control section 800 and subtraction section 810, and performs control such that steering angle θt follows target steering angle θtref. Target steering angle generation section 600 generates target steering angle θtref based on steering angle θh, and target steering angle θtref is input to steering angle control section 700 together with steering angle θt, and steering angle control section 700 calculates steering current command value Imct such that steering angle θt becomes target steering angle θtref. Subtraction section 810 then calculates deviation I2 (=Imct-Imd) between steering current command value Imct and current value (motor current value) Imd of steering motor 41 detected by motor current detector 49, and current control section 800 determines voltage control command value Vref2 based on deviation I2. The steering angle θt and the steering current command value Imct are also input to SAT correction section 200 and past value holding section 250 of reaction force control system 60. In steering device 40, the driving of steering motor 41 is controlled via PWM control section 47 and inverter 48 based on voltage control command value Vref2. Note that target steering angle generation section 600 and steering angle control section 700 form a steering control section.

[0023] Each part of the reaction force control system 60 will now be described in detail.

[0024] The target steering torque generating unit 100 generates a basic target steering torque TrefA based on the steering angle θh and the vehicle speed Vs. An example of the configuration of the target steering torque generating unit 100 is shown in Fig. 4. The target steering torque generating unit 100 includes a basic map unit 110, a differentiation unit 120, a damper gain unit 130, an additional steering / returning determination unit 140, a hysteresis correction unit 150, a multiplication unit 160, and addition units 170 and 180. The steering angle θh is input to the basic map unit 110, the differentiation unit 120, the additional steering / returning determination unit 140, and the hysteresis correction unit 150, and the vehicle speed Vs is input to the basic map unit 110 and the damper gain unit 130.

[0025] The basic map unit 110 has a basic map, and outputs a torque signal Tref_a using the basic map with the vehicle speed Vs as a parameter. The torque signal Tref_a is used to generate a basic reaction force. The basic map is adjusted by tuning, and for example, as shown in FIG. 5(A), the torque signal Tref_a increases as the magnitude |θh| of the steering angle θh increases, and also increases as the vehicle speed Vs increases. That is, the reaction force increases as the magnitude of the steering angle θh increases and as the vehicle speed Vs increases. In FIG. 5(A), the sign unit 111 outputs the sign (+1, -1) of the steering angle θh to the multiplication unit 112, and the magnitude of the torque signal Tref_a is obtained from the magnitude of the steering angle θh using the map, and the magnitude is multiplied by the sign of the steering angle θh to obtain the torque signal Tref_a. Alternatively, as shown in Fig. 5(B), a map may be constructed according to positive and negative steering angles θh, in which case the manner of change may be different depending on whether the steering angle θh is positive or negative. Also, although the basic map shown in Fig. 5 is vehicle speed sensitive, it does not have to be vehicle speed sensitive.

[0026] The differentiation unit 120 differentiates the steering angle θh to calculate the steering angular velocity ωh, and the steering angular velocity ωh is input to the steering / returning determination unit 140 and the multiplication unit 160. In addition, in the calculation of the steering angular velocity ωh, a low-pass filter (LPF) process may be appropriately performed to reduce the influence of high-frequency noise, or a differentiation operation and LPF process may be performed using a high-pass filter (HPF) and gain. The steering angular velocity ωh may be calculated by performing a differentiation operation and LPF process on the handle angle θ1 detected by the upper angle sensor or the column angle θ2 detected by the lower angle sensor, instead of the steering angle θh. The motor angular velocity of the steering motor 41 may be used instead of the steering angular velocity ωh. In this case, the differentiation unit 120 is not necessary.

[0027] The damper gain unit 130 multiplies the steering angular velocity ωh by a damper gain D G The multiplier 160 outputs the damper gain D G The steering angular velocity ωh multiplied by is input to the adder 170 as a torque signal Tref_b.G is calculated according to the vehicle speed Vs by using a vehicle speed-sensitive damper gain map included in the damper gain unit 130. The damper gain map has a characteristic that gradually increases as the vehicle speed Vs increases, as shown in FIG. 6. G By multiplying the steering angle velocity ωh by θh and compensating for the target steering torque proportional to the steering angle velocity ωh, a viscous feeling can be provided, and when the steering wheel is turned from a turned state to a released state, the steering wheel can be made to converge without oscillation, improving system stability. The damper gain map may be variable according to the steering angle θh.

[0028] The steering / returning determination unit 140 determines whether the steering is further turned or turned back based on the positive / negative relationship of the steering angle θh and the steering angular velocity ωh, as shown in FIG. 7, for example, and outputs the steering state STs, which is the determination result, to the hysteresis correction unit 150. The determination of steering further or turned back may be performed using the steering torque. That is, as shown in JP 2003-170856 A, when the sign of the steering torque and the sign of the steering torque change rate are the same and the absolute value of the steering torque change rate is equal to or greater than a predetermined value, it may be determined as further turning, and when the sign of the steering torque and the sign of the steering torque change rate are opposite to each other and the absolute value of the steering torque change rate is equal to or greater than a predetermined value, it may be determined as returning. Alternatively, the steering torque and the steering angular velocity ωh may be used, and when the signs of the steering torque and the steering angular velocity ωh are the same, it may be determined as further turning, and when the signs are opposite to each other, it may be determined as returning.

[0029] The hysteresis correction unit 150 calculates the torque signal Tref_c based on the steering angle θh and the steering state STs according to the following formula 2. In the following formula 2, x=θh, y=Tref_c, a>1, c>0, and A hys is the hysteresis width.

[0030]

number

[0031]

number

[0032] Any positive number greater than 1 can be used as "a." For example, when Napier's constant "e" is used, numbers 2 and 3 become numbers 4 and 5 below.

[0033]

number

[0034]

number

[0035] In addition, the coefficient A which represents the output width of the hysteresis characteristic hys The coefficient c representing the roundness may be made variable depending on the vehicle speed Vs and / or the steering angle θh.

[0036] The torque signals Tref_b and Tref_c are added in an adder 170, and further, the torque signal Tref_a is added to the addition result in the adder 170 in an adder 180, and the addition result in the adder 180 is output as a basic target steering torque TrefA.

[0037] Past value holding section 250 holds steering current command value Imct calculated by steering angle control section 700 for use in SAT estimation by SAT correction section 200. It holds steering current command value Imct output from steering angle control section 700, and determines a past steering current command value Imctp based on the held steering current command value Imct for use in SAT estimation by SAT correction section 200 in the next calculation cycle, and outputs it to SAT correction section 200. For example, as the past steering current command value Imctp at time point t, the steering current command value Imct at time point t-1, which is the previous calculation cycle, is used. Alternatively, n steering current command values ​​Imct from time point t-1 to tn may be held, and an average value of the n steering current command values ​​Imct may be used as the past steering current command value Imctp at time point t. Note that past value holding section 250 may be incorporated into SAT correction section 200. In particular, when using the steering current command value Imct at time point t-1, it is sufficient to temporarily hold the steering current command value Imct in a register or the like.

[0038] SAT correction section 200 estimates the SAT using the steering angle, motor angle and a steering current command value which is one piece of steering drive information, specifically, using the steering angle θt, motor angle θm of steering motor 41 and past steering current command value Imctp output from past value holding section 250, and determines corrected target steering torque TrefB from the estimated value and vehicle speed Vs. An example of the configuration of SAT correction section 200 is shown in Fig. 9. SAT correction section 200 includes a SAT estimating section 210, a filter processing section 220 and a correction value determining section 230, and the steering angle θt, motor angle θm and past steering current command value Imctp are input to SAT estimating section 210, and the vehicle speed Vs is input to correction value determining section 230.

[0039] The SAT estimation unit 210 estimates the SAT based on an equation of motion regarding the rotational motion around the pinion shaft 43 (hereinafter referred to as the "first equation of motion") and an equation of motion regarding the rotational motion around the motor drive shaft (not shown) of the steering motor 41 which connects the reduction mechanism 42 in the steering device 40 (hereinafter referred to as the "second equation of motion").

[0040] When the steering motor 41 is driving, as shown in FIG. 10(A), around the pinion shaft 43, an inertia torque (first inertia torque) and a viscous torque (first viscous torque) caused by changes in the steering angle θt, a driving torque generated based on the driving of the steering motor 41, and the SAT are generated, and since these are balanced, the first equation of motion is expressed as the following equation 6.

[0041]

number

[0042] As shown in FIG. 10(B), around the motor drive shaft, inertia torque (second inertia torque) and viscous torque (second viscous torque) due to changes in motor angle θm, drive torque, and motor torque (actuator torque) due to steering motor 41 are generated, and since these are balanced, the second equation of motion is expressed as follows:

[0043]

number

[0044] By solving the above equation 6 for fg and substituting it into equation 7 to solve for Tsat, we obtain the following equation 8.

[0045]

number

[0046] An example of the configuration of SAT estimation unit 210 is shown in Fig. 11. SAT estimation unit 210 shown in Fig. 11 is configured based on the above equation 8, and estimates the SAT using the steering angle θt, the motor angle θm, and the past steering current command value Imctp.

[0047] Angular velocity calculation unit 212b calculates the turning angular velocity by differential processing with respect to the turning angle θt, and multiplies the turning angular velocity by a viscosity coefficient Cp in block 214b to calculate the first viscous torque. Angular acceleration calculation unit 213b calculates the turning angular acceleration by differential processing with respect to the turning angular velocity, and multiplies the turning angular acceleration by a moment of inertia Jp in block 215b to calculate the first inertia torque. Angular velocity calculation unit 212a calculates the motor angular velocity by differential processing with respect to the motor angle θm, and multiplies the motor angular velocity by a viscosity coefficient Cm in block 214a to calculate the second viscous torque. Angular acceleration calculation unit 213a calculates the motor angular acceleration by differential processing with respect to the motor angular velocity, and multiplies the motor angular acceleration by a moment of inertia Jm in block 215a to calculate the second inertia torque. Conversion unit 211a multiplies past turning current command value Imctp by a torque constant to calculate motor torque Tm. Subtraction unit 216a subtracts the second inertia torque and the second viscous torque from motor torque Tm, conversion unit 211b multiplies the subtraction result by reduction gear ratio Ng, and subtraction unit 216b subtracts the first inertia torque and the first viscous torque from the multiplication result to calculate SAT, which is output as SAT estimated value Tsat.

[0048] Filter processing unit 220 performs a filter process to reduce noise contained in SAT estimated value Tsat. The filter process is performed using, for example, a first-order lag LPF, but is not limited to this. The SAT estimated value Tsat after the filter process is output as SAT estimated value Tst. Note that filter processing unit 220 may be omitted when noise reduction is realized by other means or when the superimposed noise is small. Also, the characteristics of SAT estimating unit 210 and the characteristics of filter processing unit 220 may be expressed by transfer functions, respectively, and a transfer function for calculating SAT estimated value Tst may be derived by integrating the two transfer functions, and the SAT estimated value Tst may be obtained from the steering angle θt, the motor angle θm, and the past steering current command value Imctp in a configuration corresponding to the transfer function. In this case, SAT estimating unit 210 and filter processing unit 220 are integrated.

[0049] The correction value determination unit 230 determines the corrected target steering torque TrefB from the SAT estimated value Tst and the vehicle speed Vs. The correction value determination unit 230 has a map (hereinafter, referred to as a "correction value map") that predetermines the relationship between the SAT estimated value and the corrected target steering torque, and uses the correction value map to determine the corrected target steering torque TrefB with the vehicle speed Vs as a parameter. As the correction value map, for example, a map with characteristics as shown in FIG. 12 is used. That is, when the magnitude (absolute value) of the SAT estimated value increases, the magnitude of the corrected target steering torque also increases, but the rate of increase (slope) becomes smaller as the magnitude of the SAT estimated value increases. That is, as the magnitude of the SAT estimated value increases, the magnitude of the corrected target steering torque increases gradually. In addition, the corrected target steering torque also changes depending on the vehicle speed, and as the vehicle speed increases, the magnitude of the corrected target steering torque also increases. Note that the relationship between the SAT estimated value and the corrected target steering torque may be defined by a function, a table, or the like, instead of a map. Also, the correction value map shown in FIG. 12 is vehicle speed sensitive, but it does not have to be vehicle speed sensitive.

[0050] An adder 510 adds the basic target steer torque TrefA and the corrected target steer torque TrefB, and outputs the addition result as the target steer torque Tref.

[0051] The conversion unit 300 has a characteristic of the reciprocal "1 / Kt" of the spring constant Kt of the torsion bar 2A, and converts the target steering torque Tref into a target torsion angle Δθref.

[0052] The torsion angle control unit 400 receives the target torsion angle Δθref and the torsion angle Δθ, and calculates a steering current command value Imc such that the torsion angle Δθ becomes the target torsion angle Δθref. A desired steering reaction force is realized by controlling the torsion angle Δθ to follow a value corresponding to the steering angle θh.

[0053] 13 is a block diagram showing a configuration example of the torsion angle control unit 400, which includes gain units 420, 440, and 470, an integrator 450, a differentiator 460, subtractors 410 and 480, and an adder 430, and calculates a steering current command value Imc using a target torsion angle Δθref and a torsion angle Δθ by a derivative-first type PID (proportional-integral-differential) control (PI-D control). The target torsion angle Δθref is added and input to the subtractor 410, and the torsion angle Δθ is subtracted and input to the subtractor 410 and also input to the differentiator 460.

[0054] The subtraction unit 410 calculates an angle deviation dΔθ between the target torsion angle Δθref and the torsion angle Δθ, and the angle deviation dΔθ is input to gain units 420 and 440. The gain unit 420 multiplies the angle deviation dΔθ by a proportional gain Kp, and the multiplication result is input to the addition unit 430 as a command value signal Imc1. The gain unit 440 multiplies the angle deviation dΔθ by an integral gain Ki, and the multiplication result is input to the integration unit 450 where it is integrated (1 / s), and the integration result is input to the addition unit 430 as a command value signal Imc2. The addition unit 430 adds the command value signals Imc1 and Imc2, and the sum, that is, the command value signal Imc3, is added and input to the subtraction unit 480. Differentiation unit 460 which has received the torsion angle Δθ differentiates (s) the torsion angle Δθ, the differentiation result is input to gain unit 470 and multiplied by differential gain Kd, and the multiplication result is input to subtraction unit 480 as command value signal Imc4 for subtraction. Subtraction unit 480 subtracts command value signal Imc4 from command value signal Imc3, and the subtraction result is output as steering current command value Imc.

[0055] The control in the torsion angle control unit 400 is not limited to PI-D control, and may be any commonly used control such as PI (proportional integral) control, P (proportional) control, PID control, IP control (proportional precedence type PI control), model matching control, model reference control, etc. In addition, a limiter that limits the maximum value of the steering current command value Imc may be provided downstream of the torsion angle control unit 400. A current command value for suppressing steering wheel vibration may be added to the steering current command value Imc output from the torsion angle control unit 400.

[0056] The steering current command value Imc is added to and input to a subtraction unit 520, which calculates a deviation I1 from the motor current value Imr that is fed back. A current control unit 500 receives the deviation I1, performs current control by PI control or the like, and outputs a current-controlled voltage control command value Vref1.

[0057] The voltage control command value Vref1 is sent to the reaction force device 30 and input to a PWM control unit 37 to calculate the duty, and the reaction force motor 31 is PWM-driven via an inverter 38 by a PWM signal from the PWM control unit 37. The motor current value Imr of the reaction force motor 31 is detected by a motor current detector 39 and fed back to a subtraction unit 520 of the reaction force control system 60.

[0058] For example, a three-phase brushless motor can be used as the reaction force motor 31. Here, the configuration from the subtraction unit 520 to the reaction force device 30 in the case where a three-phase brushless motor is used as the reaction force motor 31 will be described.

[0059] 14 shows an example of the above configuration, in which the subtraction unit 520 is composed of subtraction units 520a and 520b and has a dq-axis current command value calculation unit 515 disposed in front of it, an angular velocity calculation unit 530 and a three-phase / two-phase conversion unit 540 are added to the reaction force control system 60, the motor current detector 39 is composed of motor current detectors 39a, 39b and 39c, and a rotation angle sensor 36 is added to the reaction force device 30. Note that the steering angle sensor 33 and the angle sensor 34 are provided but are not shown.

[0060] The rotation angle sensor 36 detects the motor angle θe of the reaction force motor 31. The motor angle θe is an electrical angle, and is input to the angular velocity calculation unit 530, the three-phase / two-phase conversion unit 540, and the current control unit 500.

[0061] The angular velocity calculation unit 530 calculates the motor angular velocity ωe by differential processing of the motor angle θe. The motor angular velocity ωe is input to the dq-axis current command value calculation unit 515.

[0062] The dq-axis current command value calculation unit 515 uses the steering current command value Imc and the motor angular velocity ωe to calculate the d-axis steering current command value Idmc and the q-axis steering current command value Iqmc, which are current command values ​​in the dq rotating coordinate system. The d-axis steering current command value Idmc and the q-axis steering current command value Iqmc are calculated by, for example, a method executed by a dq-axis current command value calculation unit described in Japanese Patent No. 5282376. The steering assist current command value in the same publication corresponds to the steering current command value. In this case, when the motor angular velocity relative to the mechanical angle of the reaction force motor 31 is required, it is calculated based on the motor angular velocity ωe relative to the electrical angle using the relationship "electrical angle = P / 2 × mechanical angle (P is the number of magnetic poles of the motor)".

[0063] Three-phase / two-phase conversion unit 540 converts the motor current values ​​(U-phase motor current value Iumr, V-phase motor current value Ivmr, and W-phase motor current value Iwmr) flowing through each phase of reaction force motor 31 detected by motor current detectors 39a, 39b, and 39c, respectively, into two-phase current values ​​using motor angle θe. Specifically, the three-phase motor current values ​​are converted into two-phase current values, d-axis motor current value Idmr and q-axis motor current value Iqmr, according to the following equation 9.

[0064]

number

[0065] The current control unit 500 includes PI control units 501 and 502 and a two-phase / three-phase conversion unit 503 .

[0066] The PI control unit 501 obtains a d-axis voltage control command value Vdref1 by PI control based on the deviation Id1 between the d-axis steering current command value Idmc and the d-axis motor current value Idmr. Similarly, the PI control unit 502 obtains a q-axis voltage control command value Vqref1 by PI control based on the deviation Iq1 between the q-axis steering current command value Iqmc and the q-axis motor current value Iqmr. Note that the control in the PI control units 501 and 502 is not limited to PI control, and other commonly used control such as PID control may be used as long as it controls the motor current value to follow the steering current command value.

[0067] The two-phase / three-phase converter 503 converts the two-phase voltage control command values ​​consisting of the d-axis voltage control command value Vdref1 and the q-axis voltage control command value Vqref1 into three-phase voltage control command values ​​using the motor angle θe. Specifically, the two-phase voltage control command values ​​are converted into three-phase voltage control command values, that is, a U-phase voltage control command value Vuref1, a V-phase voltage control command value Vvref1, and a W-phase voltage control command value Vwref1, according to the following equation 10.

[0068]

number

[0069] Each part of the steering control system 70 will now be described in detail.

[0070] The target turning angle generating section 600 generates the target turning angle θtref based on the steering angle θh. An example of the configuration of the target turning angle generating section 600 is shown in Fig. 15. The target turning angle generating section 600 includes a limiting section 610, a rate limiting section 620, and a correcting section 630.

[0071] The limiting unit 610 limits the upper and lower limit values ​​of the steering angle θh and outputs the steering angle θh1. By limiting the upper and lower limit values ​​of the steering angle θh, when the steering angle θh becomes an abnormal value due to data corruption in RAM caused by a hardware error or a communication error, the output of an abnormal value is suppressed. As shown in FIG. 16, an upper limit value and a lower limit value for the steering angle are set in advance, and when the input steering angle θh is equal to or greater than the upper limit value, the upper limit value is output as the steering angle θh1. When the input steering angle θh is equal to or greater than the lower limit value, the lower limit value is output as the steering angle θh1. Note that the limiting unit 610 can be omitted when the steering angle does not become an abnormal value or when the output of an abnormal value is suppressed by other means.

[0072] In order to prevent a sudden change in the steering angle when a very abrupt steering operation is performed or when the steering angle becomes an abnormal value as described above, the rate limiting unit 620 sets a limit value for the amount of change in the steering angle θh1, applies a limit, and outputs the steering angle θh2. For example, the difference from the steering angle θh1 of one sample before is set as the amount of change, and when the absolute value of the amount of change is greater than a predetermined value (limit value), the steering angle θh1 is added or subtracted so that the absolute value of the amount of change becomes the limit value, and is output as the steering angle θh2, and when it is equal to or less than the limit value, the steering angle θh1 is output as the steering angle θh2 as it is. By applying a limit to the amount of change in the steering angle θh1, a sudden change in the target turning angle is prevented, and unstable behavior of the vehicle is suppressed. Note that instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to apply a limit, and a limit may be applied to the rate of change or the rate of difference instead of the amount of change. Also, in cases where the steering angle does not change suddenly, or where a sudden change is avoided by other means, the rate limiting unit 620 can be omitted.

[0073] Correction unit 630 corrects steering angle θh2 and outputs target steering angle θtref. For example, like basic map unit 110 in target steering torque generation unit 100, a map that defines the characteristics of target steering angle θtref with respect to the magnitude |θh2| of steering angle θh2 is used to obtain target steering angle θtref from steering angle θh2. Alternatively, target steering angle θtref may be obtained by simply multiplying steering angle θh2 by a predetermined gain. Also, the relationship between steering angle θh2 and target steering angle θtref may be changed based on vehicle speed Vs. For example, the steering angle ratio when vehicle speed Vs is large is changed to be smaller than the steering angle ratio when vehicle speed Vs is small. The steering angle ratio refers to the amount of change in target steering angle θtref with respect to the amount of change in steering angle θh2. In general, when the vehicle speed Vs is high, it is desirable to reduce the steering ratio in order to improve straight-line stability, and when the vehicle speed Vs is low, it is desirable to increase the steering ratio so that a large steering angle θt can be obtained with a slight steering operation. By changing the steering ratio according to the vehicle speed Vs, it is possible to achieve both of these conflicting characteristics.

[0074] The steering angle control unit 700 has a configuration and operation similar to that of the torsion angle control unit 400, and uses the target steering angle θtref and the steering angle θt through PI-D control to calculate the steering current command value Imct such that the steering angle θt follows the target steering angle θtref.

[0075] Subtraction unit 810, current control unit 800, PWM control unit 47, inverter 48 and motor current detector 49 have the same configurations and operate in the same manner as subtraction unit 520, current control unit 500, PWM control unit 37, inverter 38 and motor current detector 39, respectively. Furthermore, when a three-phase brushless motor is used as steering motor 41, the configuration from subtraction unit 810 to steering device 40 will be the same as the configuration from subtraction unit 520 to reaction force device 30 shown in FIG.

[0076] In such a configuration, an operation example of this embodiment will be described with reference to the flowcharts of FIGS.

[0077] When operation begins, steering angle θh, vehicle speed Vs, torsion angle Δθ, turning angle θt and motor angle θm are detected or calculated (step S10), and steering angle θh is input to target steering torque generation unit 100 and target turning angle generation unit 600, vehicle speed Vs is input to target steering torque generation unit 100 and SAT correction unit 200, torsion angle Δθ is input to torsion angle control unit 400, turning angle θt is input to SAT correction unit 200 and turning angle control unit 700, and motor angle θm is input to SAT correction unit 200.

[0078] The target steering torque generating unit 100, to which the steering angle θh and the vehicle speed Vs are input, generates a basic target steering torque TrefA (step S20). An example of the operation of the target steering torque generating unit 100 will be described with reference to the flowchart of FIG.

[0079] The steering angle θh input to the target steering torque generation unit 100 is input to the basic map unit 110, the differentiation unit 120, the steering / returning determination unit 140 and the hysteresis correction unit 150, and the vehicle speed Vs is input to the basic map unit 110 and the damper gain unit 130 (step S21).

[0080] The basic map unit 110 uses the basic map shown in FIG. 5(A) or (B) to generate a torque signal Tref_a according to the steering angle θh and the vehicle speed Vs, and outputs the signal to the adder 180 (step S22).

[0081] The differentiation unit 120 differentiates the steering angle θh to output the steering angle velocity ωh (step S23), and the damper gain unit 130 calculates the damper gain D according to the vehicle speed Vs using the damper gain map shown in FIG. G (Step S24), and the multiplier 160 outputs the steering angular velocity ωh and the damper gain D G The torque signal Tref_b is calculated by multiplying the signal by ωh and output to the adder 170 (step S25). The steering angular velocity ωh is also input to the further steering / returning determination unit 140.

[0082] The further steering / returning determination unit 140 determines further steering / returning from the steering angle θh and the steering angular velocity ωh according to the characteristics shown in FIG. 7, and outputs the steering state STs, which is the determination result, to the hysteresis correction unit 150 (step S26).

[0083] The hysteresis correction unit 150 performs hysteresis correction for the steering angle θh by switching between the calculations according to Equation 4 and Equation 5 according to the steering state STs (step S27), generates a torque signal Tref_c, and outputs it to the adder 170 (step S28). hys , c, x1, and y1 are set and stored in advance, but b and b' may be calculated in advance from equation 5, and b and b' may be stored instead of x1 and y1.

[0084] The torque signals Tref_b and Tref_c are added by an adder 170, and the torque signal Tref_a is added to the result of this addition by an adder 180, and the result of this addition is output as the basic target steer torque TrefA (step S29). The basic target steer torque TrefA is input to an adder 510.

[0085] SAT correction unit 200 receives vehicle speed Vs, steering angle θt, and motor angle θm, and also receives past steering current command value Imctp from past value holding unit 250, and determines corrected target steering torque TrefB (step S30). An example of the operation of SAT correction unit 200 will be described with reference to the flowchart in Fig. 19. Note that zero is set as the initial value of past steering current command value Imctp.

[0086] SAT correction section 200 inputs the input past turning current command value Imctp, turning angle θt, and motor angle θm to SAT estimation section 210, and inputs vehicle speed Vs to correction value determination section 230, respectively.

[0087] SAT estimation section 210 calculates the turning angular velocity from the turning angle θt in angular velocity calculation section 212b, and further calculates the turning angular acceleration via angular acceleration calculation section 213b, calculates the motor angular velocity from the motor angle θm in angular velocity calculation section 212a, and further calculates the motor angular acceleration via angular acceleration calculation section 213a, and calculates motor torque Tm from past turning current command value Imctp in conversion section 211a, and calculates SAT estimated value Tsat based on Equation 8 using these values, and further multiplication in conversion section 211b and blocks 214b, 215b, 214a, and 215a, and subtraction in subtraction sections 216b and 216a (step S31). SAT estimated value Tsat is input to filter processing section 220.

[0088] The filter processing unit 220 performs filtering using an LPF on the SAT estimate value Tsat to obtain a SAT estimate value Tst (step S32). The SAT estimate value Tst is input to the correction value determination unit 230.

[0089] The correction value determination unit 230, to which the vehicle speed Vs and the SAT estimated value Tst are input, determines the corrected target steering torque TrefB by using a correction value map having the characteristics shown in Fig. 12 (step S33). The corrected target steering torque TrefB is input to the addition unit 510.

[0090] The addition unit 510 receives the basic target steer torque TrefA and the corrected target steer torque TrefB, adds them together, and outputs the addition result to the conversion unit 300 as the target steer torque Tref (step S40).

[0091] The conversion unit 300 converts the target steering torque Tref into a target torsion angle Δθref (step S50), and the target torsion angle Δθref is input to the torsion angle control unit 400.

[0092] The torsion angle control unit 400 receives the torsion angle Δθ together with the target torsion angle Δθref, performs PI-D control using the configuration shown in FIG. 13, and calculates the steering current command value Imc (step S60).

[0093] The steering current command value Imc is added to and input to the subtraction unit 520, which calculates a deviation I1 from the motor current value Imr detected by the motor current detector 39 (step S70). The deviation I1 is input to the current control unit 500, which calculates a voltage control command value Vref1 by current control (step S80). Thereafter, the reaction force motor 31 is controlled to be driven based on the voltage control command value Vref1 via the PWM control unit 37 and the inverter 38 (step S90).

[0094] On the other hand, target turning angle generating section 600, to which steering angle θh has been input, generates target turning angle θtref (step S100). An example of the operation of target turning angle generating section 600 will be described with reference to the flowchart of FIG.

[0095] The steering angle θh input to target turning angle generation section 600 is input to limiting section 610. Limiting section 610 limits the upper and lower limits of steering angle θh using preset upper and lower limits (step S101), and outputs this to rate limiting section 620 as steering angle θh1. Rate limiting section 620 limits the amount of change in steering angle θh1 using preset limiting values ​​(step S102), and outputs this to correction section 630 as steering angle θh2. Correcting section 630 corrects steering angle θh2 to find target turning angle θtref (step S103). Target turning angle θtref is input to turning angle control section 700.

[0096] The steering angle control section 700 receives the steering angle θt together with the target steering angle θtref, and determines the steering current command value Imct by PI-D control (step S110).

[0097] The steering current command value Imct is held in past value holding section 250 (step S120), and is also added and input to subtraction section 810. Subtraction section 810 calculates a deviation I2 between the steering current command value Imct and the motor current value Imd detected by motor current detector 49 (step S130). The deviation I2 is input to current control section 800, which calculates a voltage control command value Vref2 by current control (step S140). Thereafter, based on the voltage control command value Vref2, driving of steering motor 41 is controlled via PWM control section 47 and inverter 48 (step S150).

[0098] The order of data input and calculations in FIGS. 17 to 20 can be changed as appropriate.

[0099] In the above embodiment, the target steering torque generating unit 100 includes the damper gain unit 130 and the hysteresis correction unit 150. However, when the effect of the damper gain and / or the effect of the hysteresis correction are realized by another means, or when the reduction of the amount of calculation is important, the damper gain unit 130 and / or the hysteresis correction unit 150 and the components related thereto may be omitted. Also, a phase compensation unit 190 that performs phase compensation may be inserted before or after the basic map unit 110. That is, the configuration of the region R surrounded by the dashed line in FIG. 4 may be configured as shown in FIG. 21(A) or (B). In the phase compensation unit 190, phase lead compensation is set as phase compensation, and for example, when phase lead compensation is performed by a first-order filter with a numerator cutoff frequency of 1.0 Hz and a denominator cutoff frequency of 1.3 Hz, a refreshing feel can be realized. The target steering torque generating unit 100 is not limited to the above configuration as long as it is configured based on the steering angle.

[0100] Other embodiments of the present invention will be described below. In each of the following embodiments, the same components as those in the other embodiments described above are denoted by the same reference numerals, and the description thereof will be omitted in part or in whole.

[0101] Although the SAT estimation unit 210 in the first embodiment estimates the SAT based on the formula 8 derived from the first and second equations of motion, it is also possible to estimate the SAT using only the first equation of motion. That is, by solving the formula 6 above for Tsat, the following formula 11 is obtained.

[0102]

number

[0103] A configuration example (second embodiment) of the SAT estimating section corresponding to the above is shown in Fig. 22. SAT estimating section 210A in the second embodiment is configured based on the above formula 11, and estimates SAT using steering angle θt and motor angle θm. Compared with SAT estimating section 210 in the first embodiment shown in Fig. 11, past steering current command value Imctp is not input, and conversion sections 211a and 211b, angular velocity calculation section 212a, angular acceleration calculation section 213a, blocks 214a and 215a and subtraction section 216a are not present, and instead torque determination section 217 is arranged. Also, since past steering current command value Imctp is not used, past value holding section 250 is not required.

[0104] The torque determination unit 217 determines the driving torque fg based on the steering angle θt and the motor angle θm. The torque determination unit 217 determines the driving torque fg by using a map (hereinafter referred to as the "torque determination map") with characteristics as shown in FIG. 23, for example. That is, the motor angle θm is converted into a value for the pinion shaft based on the reduction ratio Ng, and the driving torque fg is determined by using a torque determination map in which the driving torque fg is determined in advance for the deviation between the steering angle θt and the motor angle (θm / Ng) converted into the pinion shaft. The torque determination map has a characteristic that the magnitude of the driving torque fg gradually increases from zero as the magnitude of the deviation increases from zero. Note that the characteristic of the torque determination map may be a characteristic in which the driving torque fg changes linearly, that is, in proportion to the deviation. In this case, instead of using the map, the deviation may be multiplied by a gain to calculate the driving torque fg.

[0105] In the SAT estimation unit 210A, the viscous torque and inertia torque are calculated by the angular velocity calculation unit 212b, the angular acceleration calculation unit 213b, and the blocks 214b and 215b, and the viscous torque and inertia torque are subtracted by the subtraction unit 216b from the driving torque fg determined by the torque determination unit 217, and the subtraction result is output as the SAT estimated value Tsat.

[0106] Compared with the operation of the first embodiment, the operation of the second embodiment is the same as that of the first embodiment except that the operation of the SAT estimation unit (step S31 in the flowchart shown in FIG. 19) changes as described above and the operation of the past value holding unit 250 (step S120 in the flowchart shown in FIG. 17) is eliminated.

[0107] In the first embodiment, SAT estimation section 210 calculates motor torque Tm from past steering current command value Imctp, but it can also calculate it from motor current value Imd, which is the current value of steering motor 41, instead of past steering current command value Imctp. In the first embodiment, the steering current command value and the motor current value are considered to be approximately equal, and SAT is estimated using the steering current command value. However, there may be a deviation between the two values ​​due to time delay, error, etc., and this deviation may be reflected in the motor torque calculation and further in the SAT estimation, which may affect the transmission of the SAT feeling. Therefore, by using the motor current value instead of the steering current command value, the effect can be reduced.

[0108] A configuration example (third embodiment) of the present invention corresponding to the above is shown in Fig. 24. Compared to the first embodiment shown in Fig. 3, reaction force control system 60B in control device 50B in the third embodiment does not have past value holding section 250, and motor current value Imd detected by motor current detector 49 is input to SAT correction section 200, instead of past steering current command value Imctp.

[0109] In the SAT correction section 200, the motor current value Imd is used as the turning drive information, and the SAT is estimated using the turning angle θt, the motor angle θm, and the motor current value Imd.

[0110] Compared to the operation of the first embodiment, the operation of the third embodiment is such that the operation of the past value holding unit 250 is eliminated, and the motor current value Imd detected by the motor current detector 49 is input to the SAT correction unit 200 in addition to the subtraction unit 810, and the only difference between the operation of the SAT correction unit 200 and that of the first embodiment is that the other operations are the same.

[0111] Incidentally, in the second embodiment as well, SAT estimation may be performed using the motor current value Imd instead of the past turning current command value Imctp.

[0112] In the above-mentioned embodiments (first to third embodiments), the reaction force control system controls the torsion angle to follow the target torsion angle, but the control in the reaction force control system is not limited to this, and the reaction force control system may control the steering torque to follow the target steering torque. Fig. 25 shows a configuration example (fourth embodiment) in which the reaction force control system in the first embodiment controls the steering torque to follow the target steering torque.

[0113] In the reaction force control system 60C in the control device 50C in the fourth embodiment, compared to the first embodiment shown in FIG. 3, the torsion angle control unit 400 is replaced with a torque control unit 900, the conversion unit 300 is eliminated, and a steering torque calculation unit 950 is added.

[0114] The steering torque calculation unit 950 converts the torsion angle Δθ calculated by the torsion angle calculation unit 35 into a steering torque (torque of the torsion bar) Tt. For example, the steering torque Tt is calculated by multiplying the torsion angle Δθ by the spring constant Kt of the torsion bar 2A. The steering torque Tt can also be detected by using a torque sensor disclosed in, for example, JP 2008-216172 A.

[0115] The torque control unit 900 has a configuration and operation similar to that of the torsion angle control unit 400, and uses the target steering torque Tref and the steering torque Tt through PI-D control to calculate a steering current command value Imc such that the steering torque Tt follows the target steering torque Tref.

[0116] An operation example of the fourth embodiment will be described with reference to the flowchart of Fig. 26. Fig. 26 shows only the operations that are different from the operation example of the first embodiment shown in Fig. 17.

[0117] The torsion angle Δθ calculated in step S10 in the flowchart shown in FIG. 17 is input to the steering torque calculation unit 950, and the target steering torque Tref generated in step S40 is input to the torque control unit 900.

[0118] The steering torque calculation unit 950 multiplies the torsion angle Δθ by the spring constant Kt to calculate the steering torque Tt (step S50A). The steering torque Tt is input to the torque control unit 900.

[0119] The torque control unit 900 obtains the steering current command value Imc by PI-D control for the target steering torque Tref and the steering torque Tt (step S60A). After that, the process proceeds to step S70.

[0120] In the second and third embodiments, the reaction force control system may also perform control such that the steering torque follows the target steering torque.

[0121] In the above-mentioned embodiments (first to fourth embodiments), one control device has a reaction force control system and a steering control system, but a control device having only a reaction force control system and a control device having only a steering control system may be provided. In this case, the control devices transmit and receive data by communication. The SBW system shown in FIG. 1 does not have a mechanical connection between the reaction force device 30 and the steering device 40, but the present invention is also applicable to an SBW system having a mechanical torque transmission mechanism that mechanically connects the column shaft 2 and the steering mechanism with a clutch or the like when an abnormality occurs in the system. In such an SBW system, when the system is normal, the clutch is turned off to release the mechanical torque transmission, and when the system is abnormal, the clutch is turned on to enable the mechanical torque transmission. Furthermore, although the reaction force device 30 has a torsion bar, it is not limited to a torsion bar as long as the mechanism has an arbitrary spring constant between the handle 1 and the reaction force motor 31.

[0122] The figures used above are conceptual diagrams for qualitatively explaining the present invention, and the present invention is not limited to these. Also, the above-mentioned embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment, and various modifications can be made without departing from the scope of the present invention. [Explanation of symbols]

[0123] 1 Handle 2 Column shaft (steering shaft, handle shaft) 2A Torsion bar 10 Vehicle speed sensor 30 Reaction Device 31 Reaction motor 32, 42 Reduction mechanism 33 Steering angle sensor 34, 44 Angle sensor 35 Torsion angle calculation section 36, 46 Rotation angle sensor 37, 47 PWM control unit 38, 48 inverter 39, 49 Motor current detector 40 Steering gear 41 Steering motor 43 Pinion shaft 50, 50B, 50C Control device 60, 60B, 60C Reaction force control system 70 Steering control system 100 Target steering torque generating unit 110 Basic Map Section 130 Damper gain section 140 Turning further / returning judgment section 150 Hysteresis compensation section 190 Phase compensation section 200 SAT correction section 210, 210A SAT Estimation Section 211a, 211b conversion section 212a, 212b, 530 Angular velocity calculation section 213a, 213b Angular acceleration calculation section 217 Torque determination unit 220 Filter processing section 230 Correction value determination unit 250 Past value storage unit 300 Converter 400 Torsion angle control unit 500, 800 Current control section 501, 502 PI control unit 503 2-phase / 3-phase conversion unit 515 dq axis current command value calculation unit 540 3-phase / 2-phase converter 600 Target steering angle generation unit 610 Restrictions 620 Rate Limiter 630 Correction Unit 700 Steering angle control unit 900 Torque control section 950 Steering torque calculation unit

Claims

1. A control device for a vehicle steering system that controls a reaction device that applies torque to a steering member using a reaction actuator and a steering device that steers the steering member using a steering actuator, a target steering torque generation unit that generates a basic target steering torque based on at least a steering angle of the steering member; a self-aligning torque correction unit that calculates a corrected target steering torque, the self-aligning torque correction unit includes a self-aligning torque estimating unit that calculates a self-aligning torque estimated value using at least a steering angle of the steering member and a rotation angle of the steering actuator, and a correction value determining unit that determines the corrected target steering torque from the self-aligning torque estimated value, the self-aligning torque estimating unit calculates the self-aligning torque estimated value using a first viscosity torque calculated from a steering angular velocity calculated from the steering angle, a first inertia torque calculated from a steering angular acceleration calculated from the steering angular velocity, a second viscosity torque calculated from a rotational angular velocity calculated from the rotation angle, a second inertia torque calculated from a rotational angular acceleration calculated from the rotational angular velocity, and an actuator torque related to drive control of the steering actuator, A control device for a vehicle steering system, comprising: a control device for controlling a steering current command value for driving the reaction force actuator, the control device being configured to calculate a steering current command value for driving the reaction force actuator based on the basic target steering torque and the corrected target steering torque.

2. a steering control unit that calculates a steering current command value for driving and controlling the steering actuator in accordance with the steering angle, 2. The control device for a vehicle steering system according to claim 1, wherein the self-aligning torque estimating section uses the steering current command value or a value of a current supplied to the steering actuator as the steering drive information.

3. A control device for a vehicle steering system, the control device controlling a reaction device that applies torque to a steering member using a reaction actuator, and a steering device that steers the steering member using a steering actuator, comprising: a target steering torque generation unit that generates a basic target steering torque based on at least a steering angle of the steering member; a self-aligning torque correction unit that calculates a corrected target steering torque, the self-aligning torque correction unit includes a self-aligning torque estimating unit that calculates a self-aligning torque estimated value using at least a steering angle of the steering member and a rotation angle of the steering actuator, and a correction value determining unit that determines the corrected target steering torque from the self-aligning torque estimated value, the self-aligning torque estimation unit calculates the self-aligning torque estimation value using a viscous torque calculated from a steering angular velocity calculated from the steering angle, an inertia torque calculated from a steering angular acceleration calculated from the steering angular velocity, and a drive torque calculated based on either the steering angle or the rotation angle, A control device for a vehicle steering system, comprising: a control device for controlling a steering current command value for driving the reaction force actuator, the control device being configured to calculate a steering current command value for driving the reaction force actuator based on the basic target steering torque and the corrected target steering torque.

4. The correction value determination unit, 4. The control device for a vehicle steering system according to claim 1, wherein the control device has a characteristic that, as the magnitude of the self-aligning torque estimation value increases, the magnitude of the corrected target steering torque increases and the rate at which the magnitude of the corrected target steering torque increases decreases.

5. 5. The control device for a vehicle steering system according to claim 4, wherein the characteristic of the correction value determination unit changes according to the vehicle speed.

6. The self-aligning torque correction unit The self-aligning torque estimation device further includes a filter processor that reduces noise contained in the self-aligning torque estimation value.

6. The control device for a vehicle steering system according to claim 1, wherein the self-aligning torque estimated value in which the noise has been reduced is input to the correction value determination section.

7. The reaction device has a torsion bar, a conversion unit that converts a target steering torque calculated from the basic target steering torque and the corrected target steering torque into a target torsion angle; 7. The control device for a vehicle steering system according to claim 1, further comprising a torsion angle control unit that calculates the steering current command value so as to cause the torsion angle of the torsion bar to follow the target torsion angle.

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