Vehicle steering system control device

Abstract

To provide a control device of a vehicular steering system that can suppress increase in mechanical load and consumption power in a steering terminal of a steering wheel.SOLUTION: A rotation restricting mechanism is provided in a steering terminal of a steering wheel. A control device of a vehicular steering system comprises a steering torque control part 400 that generates a first current command value on the basis of a steering torque target value. The steering torque control part 400 comprises, at the steering terminal, a current compensation gain calculating part 440 that derives current compensation gain Gi for restricting a current command value Iref_a, and an output restricting part 430 that restricts the current command value Iref_a and generates a motor current command value Ih_ref for driving a motor for reaction force, on the basis of the current compensation gain Gi.SELECTED DRAWING: Figure 7

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, in which a steering mechanism (FFA: Force Feedback Actuator) having a steering wheel operated by the driver and a road wheel actuator (RWA: Road Wheel Actuator) that steers the steered wheels are mechanically separated. In the SBW system, the steering mechanism and the road wheel actuator are electrically connected via an electronic control unit (ECU). The 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 the steering reaction force using a reaction force actuator equipped with a reaction force motor, and the road wheel actuator steers the steered wheels using a steering actuator equipped with a steering motor. The reaction force actuator and the road wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction force actuator is transmitted to the driver via the column shaft and the road wheel (see, for example, Patent Document 1).

[0003] In such SBW systems, it is necessary to limit the steering operation by the driver so that the steering angle of the steering mechanism does not exceed the steerable range of the steering mechanism. For example, a technology has been disclosed that increases the steering reaction force when the steering angle exceeds a steering angle threshold, thereby limiting the steerable range (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-175770 [Patent Document 2] International Publication No. 2019 / 193976 Summary of the Invention [Problem to be solved by the invention]

[0005] In a SBW system in which the steering mechanism and the turning mechanism are mechanically separated, the control device controls the actual steering torque so that it follows a steering torque target value corresponding to the steering angle. The steering mechanism may also be provided with a stopper at the steering end, which is the mechanical steering limit. In such a configuration, if the driver performs further steering at the steering end (for example, steering further right after steering to the right), excessive actual steering torque may be generated due to torsion occurring between the upper and lower ends of the column shaft. In this case, the rotation of the lower end of the column shaft where the stopper is provided is limited by the stopper. This causes a deviation between the actual steering torque and the steering torque target value generated based on the steering angle of the steering wheel provided on the upper end of the column shaft. This causes a steering force (steering assist force) acting in the opposite direction to the steering reaction force to be applied by the reaction force motor. This may place an excessive mechanical load on the steering mechanism, including the stopper. Therefore, the steering mechanism may need to be enlarged in order to ensure its strength. Furthermore, when rotation is inhibited, excessive current may flow through the reaction motor, which may result in increased power consumption by the reaction motor and ECU.

[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 suppress increases in mechanical load and power consumption at the steering end. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a control device for a vehicle steering system according to one embodiment of the present invention is a control device for a vehicle steering system having a rotation limiting mechanism provided at a steering terminal of a steering wheel, a reaction motor that applies a steering reaction force to the steering wheel in accordance with the steering angle of the steering wheel, and a steering motor that steers steered wheels in accordance with the steering angle of the steering wheel, and is equipped with a steering torque target value generation unit that generates a steering torque target value that is a target value of steering torque for obtaining the steering reaction force, and a steering torque control unit that generates a first current command value based on the steering torque target value, and the steering torque control unit is equipped with a current compensation gain calculation unit that derives a current compensation gain that limits the first current command value at the steering terminal, and an output limiting unit that generates a second current command value for driving the reaction motor based on the current compensation gain.

[0008] With the above configuration, it is possible to reduce the mechanical load on the steering mechanism including the rotation limiting mechanism at the steering terminal end. Also, it is possible to limit the current flowing through the reaction force motor at the steering terminal end, thereby suppressing an increase in power consumption of the reaction force motor and the ECU constituting the control device.

[0009] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering torque, which is the actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold, and determines that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering torque becomes less than a second torque threshold that is smaller than the first torque threshold.

[0010] According to the above configuration, it is possible to determine whether or not the steering end point has been reached using the actual steering torque, which is the actual steering torque of the steering wheel, as a parameter.

[0011] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering torque, which is the actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold and a predetermined first time has elapsed, and that after determining that the steering end point has been reached, the actual steering torque becomes less than a second torque threshold that is smaller than the first torque threshold and a predetermined second time has elapsed, and that the steering end point has been missed.

[0012] According to the above configuration, when further steering and return steering are repeated at the steering terminal end, it is possible to prevent the second current command value from being frequently switched.

[0013] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering angle, which is the actual steering angle of the steering wheel, is equal to or greater than a first steering angle threshold, and determines that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold.

[0014] According to the above configuration, it is possible to determine whether or not the steering end point has been reached using the actual steering angle, which is the actual steering angle of the steering wheel, as a parameter.

[0015] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold and a predetermined first time has elapsed, and that after determining that the steering end point has been reached, the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold and a predetermined second time has elapsed, and that the steering end point has been missed.

[0016] According to the above configuration, when further steering and return steering are repeated at the steering terminal end, it is possible to prevent the second current command value from being frequently switched.

[0017] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering torque, which is the actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold and the actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold, and determines that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering torque becomes less than a second torque threshold that is smaller than the first torque threshold or the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold.

[0018] According to the above configuration, it is possible to determine whether or not the steering end point has been reached using the actual steering torque, which is the actual steering torque of the steering wheel, and the actual steering angle, which is the actual steering angle of the steering wheel, as parameters.

[0019] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering torque, which is the actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold and the actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold, and a predetermined first time period has elapsed, and that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering torque becomes less than a second torque threshold that is smaller than the first torque threshold, or the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold, and a predetermined second time period has elapsed.

[0020] According to the above configuration, when further steering and return steering are repeated at the steering terminal end, it is possible to prevent the second current command value from being frequently switched.

[0021] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold and the actual steering angular velocity, which is the actual steering angular velocity of the steering wheel, becomes equal to or less than a first steering angular velocity threshold, and determines that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering angle becomes less than a second steering angle threshold which is smaller than the first steering angle threshold, or the actual steering angular velocity becomes greater than a second steering angular velocity which is larger than the first steering angular velocity threshold.

[0022] According to the above configuration, it is possible to determine whether or not the steering end point has been reached using the actual steering angle, which is the actual steering angle of the steering wheel, and the actual steering angular velocity, which is the actual steering angular velocity of the steering wheel, as parameters.

[0023] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit determines that the steering end point has been reached when the actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold and the actual steering angular velocity, which is the actual steering angular velocity of the steering wheel, becomes equal to or less than a first steering angular velocity threshold, and a predetermined first time has elapsed, and that the steering end point has been missed when, after determining that the steering end point has been reached, the actual steering angle becomes less than a second steering angle threshold which is smaller than the first steering angle threshold, or the actual steering angular velocity becomes greater than a second steering angular velocity which is larger than the first steering angular velocity threshold, and a predetermined second time has elapsed.

[0024] According to the above configuration, when further steering and return steering are repeated at the steering terminal end, it is possible to prevent the second current command value from being frequently switched.

[0025] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit, when it determines that the steering end point has been reached, transitions the current compensation gain from a first gain to a second gain smaller than the first gain, and, when it determines that the steering end point has been missed, transitions the current compensation gain from the second gain to the first gain.

[0026] According to the above configuration, it is possible to determine whether or not the steering has reached the end point and change the second current command value.

[0027] As a desirable aspect of the control device for a vehicle steering system, it is preferable that the current compensation gain calculation unit, when it determines that the steering end point has been reached, monotonically decreases the current compensation gain from a first gain to a second gain smaller than the first gain at a predetermined first time change rate, and, when it determines that the steering end point has been missed, monotonically increases the current compensation gain from the second gain to the first gain at a predetermined second time change rate.

[0028] According to the above configuration, it is possible to make the change in the second current command value gentle when the current compensation gain switches between the first gain and the second gain.

[0029] In a preferred embodiment of the control device for a vehicle steering system, the output limiting unit preferably generates the second current command value by multiplying the first current command value by the current compensation gain.

[0030] According to the above configuration, it is possible to generate the second current command value by limiting the first current command value by the current compensation gain.

[0031] In a preferred embodiment of the control device for a vehicle steering system, the output limiting unit preferably limits a lower limit value of the second current command value.

[0032] According to the above configuration, it is possible to suppress a sudden change in the second current command value at the steering terminal end.

[0033] In a preferred embodiment of the control device for a vehicle steering system, the output limiting unit includes a comparison unit that compares a third current command value, obtained by multiplying the first current command value by the current compensation gain, with a predetermined current command value lower limit value, and the comparison unit outputs the third current command value as the second current command value when the third current command value is greater than the current command value lower limit value, and outputs the current command value lower limit value as the second current command value when the third current command value is equal to or less than the current command value lower limit value.

[0034] According to the above configuration, when the third current command value is equal to or less than the current command lower limit value, the second current command value is limited to the current command lower limit value.

[0035] In a preferred embodiment of the control device for a vehicle steering system, the output limiting unit preferably limits an upper limit value and a lower limit value of the second current command value.

[0036] According to the above configuration, it is possible to suppress unnecessary fluctuations in the second current command value due to noise or the like.

[0037] In a preferred aspect of the control device for a vehicle steering system, the output limiting unit includes a first comparing unit that compares the first current command value with a predetermined current command value upper limit value, and a second comparing unit that compares a third current command value, which is an output value of the first comparing unit, with a predetermined current command value lower limit value, and the first comparing unit outputs the first current command value when the first current command value is equal to or less than the current command value upper limit value, and outputs the current command value upper limit value when the first current command value is greater than the current command value lower limit value, and the second comparing unit outputs the third current command value as the second current command value when the third current command value is greater than the current command value lower limit value, and outputs the current command value lower limit value as the second current command value when the third current command value is equal to or less than the current command value lower limit value.

[0038] According to the above configuration, when the first current command value is greater than the current command lower limit value, the third current command value is limited to the current command upper limit value, and when the third current command value is equal to or less than the current command lower limit value, the second current command value is limited to the current command lower limit value.

[0039] In a preferred aspect of the control device for a vehicle steering system, the output limiting unit includes a current command upper limit generating unit that generates the current command upper limit, and the current command upper limit generating unit preferably monotonically increases the current command upper limit from the current command lower limit to a predetermined current command maximum value as the current compensation gain increases.

[0040] According to the above configuration, the upper limit of the current command value can be set according to the current compensation gain. [Effects of the Invention]

[0041] According to the present invention, it is possible to provide a control device for a vehicle steering system that can suppress an increase in mechanical load and power consumption at the steering terminal. [Brief explanation of the drawings]

[0042] [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 an example of the configuration of a torque sensor. [Figure 3] FIG. 3 is a schematic diagram showing the hardware configuration of the ECU. [Figure 4] FIG. 4 is a diagram illustrating an example of a basic control block configuration of a control device according to the present disclosure. [Figure 5] FIG. 5 is a region diagram for explaining the steering direction in the present disclosure. [Figure 6A] FIG. 6A is a conceptual diagram showing the change over time in the steering wheel angle θ1 when the steering wheel is turned further to the right from the center position at a constant speed in the control block configuration shown in FIG. [Figure 6B]FIG. 6B is a conceptual diagram showing the change over time in the column angle θ2 when the steering wheel is turned further to the right from the center position at a constant speed in the control block configuration shown in FIG. [Figure 6C] FIG. 6C is a conceptual diagram showing the change over time in the steering torque target value Th_ref when the steering wheel is turned further to the right at a constant speed from the center position in the control block configuration shown in FIG. [Figure 6D] FIG. 6D is a conceptual diagram showing the change over time in actual steering torque Th_act when the steering wheel is turned further right from the center position at a constant speed in the control block configuration shown in FIG. [Figure 6E] FIG. 6E is a conceptual diagram showing the change over time in the torque difference ΔTh between the steering torque target value Th_ref and the actual steering torque Th_act when the steering wheel is further steered to the right at a constant speed from the center position in the control block configuration shown in FIG. [Figure 6F] FIG. 6F is a conceptual diagram showing the change over time of the motor current command value Ih_ref when the steering wheel is turned further right from the center position at a constant speed in the control block configuration shown in FIG. [Figure 7] FIG. 7 is a block diagram showing an example of the configuration of the steering torque control unit according to the first embodiment. [Figure 8] FIG. 8 is a block diagram illustrating an example of the configuration of the current compensation gain calculation unit according to the first embodiment. [Figure 9] FIG. 9 is a conceptual diagram showing a specific example of the operation of the current compensation gain calculation unit according to the first embodiment. [Figure 10] FIG. 10 is a conceptual diagram showing a first modified example of a specific operation example of the current compensation gain calculation unit according to the first embodiment. [Figure 11] FIG. 11 is a conceptual diagram showing a second modified example of a specific operation example of the current compensation gain calculation unit according to the first embodiment. [Figure 12] FIG. 12 is a block diagram showing an example of the configuration of a steering torque control unit according to the second embodiment. [Figure 13] FIG. 13 is a block diagram illustrating an example of the configuration of a current compensation gain calculation unit according to the second embodiment. [Figure 14] FIG. 14 is a conceptual diagram showing a specific example of the operation of the current compensation gain calculation unit according to the second embodiment. [Figure 15] FIG. 15 is a block diagram showing an example of the configuration of a steering torque control unit according to the third embodiment. [Figure 16] FIG. 16 is a block diagram illustrating an example of the configuration of a current compensation gain calculation unit according to the third embodiment. [Figure 17A] FIG. 17A is a conceptual diagram illustrating a specific example of the operation of the current compensation gain calculation unit according to the third embodiment. [Figure 17B] FIG. 17B is a conceptual diagram showing a first modified example of a specific operation example of the current compensation gain calculation unit according to the third embodiment. [Figure 17C] FIG. 17C is a conceptual diagram showing a second modified example of a specific operation example of the current compensation gain calculation unit according to the third embodiment. [Figure 17D] FIG. 17D is a conceptual diagram showing a third modified example of a specific operation example of the current compensation gain calculation unit according to the third embodiment. [Figure 18] FIG. 18 is a block diagram showing an example of the configuration of a steering torque control unit according to the fourth embodiment. [Figure 19] FIG. 19 is a block diagram illustrating an example of the configuration of a current compensation gain calculation unit according to the fourth embodiment. [Figure 20A] FIG. 20A is a conceptual diagram showing a specific example of the operation of the current compensation gain calculation unit according to the fourth embodiment. [Figure 20B] FIG. 20B is a conceptual diagram showing a first modified example of a specific operation example of the current compensation gain calculation unit according to the fourth embodiment. [Figure 20C] FIG. 20C is a conceptual diagram showing a second modified example of a specific operation example of the current compensation gain calculation unit according to the fourth embodiment. [Figure 20D] FIG. 20D is a conceptual diagram showing a third modified example of a specific operation example of the current compensation gain calculation unit according to the fourth embodiment. [Figure 21] FIG. 21 is a block diagram illustrating an example of the configuration of an output limiting unit according to the fifth embodiment. [Figure 22]FIG. 22 is a block diagram illustrating an example of the configuration of an output limiting unit according to the sixth embodiment. [Figure 23] FIG. 23 is a block diagram illustrating an example of an internal configuration of a current command value upper limit generating unit according to the sixth embodiment. [Figure 24] FIG. 24 is a diagram illustrating an example of input / output characteristics of the current command upper limit generating unit according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0043] 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.

[0044] 1 is a block diagram showing an example of an outline of an SBW system equipped with a control device according to the present disclosure, which 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.

[0045] 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.

[0046] 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.

[0047] 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."

[0048] Fig. 2 is a schematic diagram showing an example of the configuration of a torque sensor. As shown in Fig. 2, the torque sensor 34 includes an upper angle sensor 34A and a lower angle sensor 34B arranged on either side of a torsion bar 2A inserted in the column shaft 2, and a torque calculation unit 36. The upper angle sensor 34A is arranged on the steering wheel 1 side of the column shaft 2 and detects the steering wheel angle θ1. The lower angle sensor 34B is arranged on the reduction mechanism 32 side of the column shaft 2 and detects the column angle θ2.

[0049] When the driver steers the steering wheel 1, a twist occurs in the torsion bar 2A, and a torsion angle Δθ occurs between the steering wheel angle θ1 detected by the upper angle sensor 34A and the column angle θ2 detected by the lower angle sensor 34B (Δθ=θ1−θ2). The torque calculation unit 34C calculates the actual steering torque Th_act according to the torsion angle Δθ. The configuration of the torque sensor 34 is not limited to the embodiment shown in FIG. 2.

[0050] In the present disclosure, a stopper (rotation limiting mechanism) 35 that physically sets a steering end point, which is the limit of steering possible, is provided on the lower end side of the column shaft 2. That is, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

[0051] 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." The steering device 40 is not limited to the above-described embodiment, and may be of a ball screw type, an electronically controlled hydraulic type, or the like.

[0052] 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.

[0053] 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.

[0054] 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. 3 is a schematic diagram showing the hardware configuration of the ECU. Cooperative control of the reaction force device 30 and the steering device 40 is mainly executed by a program inside the CPU of the ECU.

[0055] Fig. 4 is a diagram showing an example of a basic control block configuration of a control device according to the present disclosure. In Fig. 4, reaction force device 30 includes, in addition to reaction force motor 31 and the above-described 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-described 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.

[0056] Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may include, for example, a RAM (random access memory) or a ROM (read only memory) for storing data, programs, etc., as shown in Fig. 3. The control device 50 may also include a PWM control unit 37, an inverter 38, a motor current detector 39, a PWM control unit 47, an inverter 48, and a motor current detector 49.

[0057] As shown in Fig. 4, control device 50 includes, as control blocks, steering torque target value generation section 200, 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, 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.

[0058] 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.

[0059] The steering torque target value generating section 200 generates a steering torque target value Th_ref.

[0060] The steering torque control unit 400 generates a motor current command value Ih_ref, which is a control target value of the current to be supplied to the reaction force motor 31. In the present disclosure, the steering torque control unit 400 calculates the motor current command value Ih_ref such that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero. Alternatively, the steering torque control unit 400 may receive the torsion angle Δθ of the torsion bar 2A and calculate the motor current command value Ih_ref such that the torsion angle Δθ approaches zero.

[0061] 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 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.

[0062] 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.

[0063] 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.

[0064] A steering angle target value generating section 600 generates a steering angle target value θt_ref based on the steering angle θh.

[0065] Steering angle control unit 700 generates 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 motor current command value It_ref such that deviation θt_err between steering angle target value θt_ref and actual steering angle θt_act approaches zero.

[0066] 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 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.

[0067] 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.

[0068] In this embodiment, steering torque control unit 400, current control unit 500, steering angle target value generation unit 600, steering angle control unit 700, and current control unit 800 may be configured to realize each control in reaction force control system 60 or steering control system 70, and are not limited by the configuration of each of these control blocks.

[0069] Here, the steering direction in the present disclosure will be described. Fig. 5 is a region diagram for explaining the steering direction in the present disclosure. In Fig. 5, the horizontal axis represents the steering angle, and the vertical axis represents the steering angular velocity.

[0070] Area A ((θh, ωh) = (+, +)) shown in FIG. 5 indicates that the steering wheel 1 has been turned to the right (θh>0) and has been turned further to the right (ωh>0) (hereinafter also referred to as "rightward steering"). Area B ((θh, ωh) = (+, -)) shown in FIG. 5 indicates that the steering wheel 1 has been turned to the right (θh>0) and has been turned back to the left (ωh<0) (hereinafter also referred to as "leftward steering"). Area C ((θh, ωh) = (-, -)) shown in FIG. 5 indicates that the steering wheel 1 has been turned to the left (θh<0) and has been turned further to the left (ωh<0) (hereinafter also referred to as "leftward steering"). Area D ((θh, ωh) = (-, +)) shown in Figure 5 indicates that the steering wheel 1 is turned to the left (θh < 0) and then turned back to the right (ωh > 0) (hereinafter also referred to as "right return steering"). Also, in Figure 5, on the steering angle θh axis (ωh = 0) it is indicated that the steering wheel 1 is neither turned further nor turned back ((θh, ωh) = (θh, 0)), and on the steering angular velocity ωh axis (θh = 0) it is indicated that the steering wheel 1 is in the center position ((θh, ωh) = (0, ωh)).

[0071] 6A to 6F are conceptual diagrams showing the time changes of each parameter when the steering wheel is steered further to the right at a constant speed from the center position in the control block configuration shown in FIG. 4. FIG. 6A shows the time change of the steering wheel angle θ1. FIG. 6B shows the time change of the column angle θ2. FIG. 6C shows the time change of the steering torque target value Th_ref. FIG. 6D shows the time change of the actual steering torque Th_act. FIG. 6E shows the time change of the torque difference ΔTh between the steering torque target value Th_ref and the actual steering torque Th_act. FIG. 6F shows the time change of the motor current command value Ih_ref. FIGS. 6A to 6F show an example in which the steering wheel 1 is steered further to the right at a constant speed from the center position, and the steering is limited by the stopper 35 at time t_st. Here, as shown in FIG. 6B, θ2_end, where the column angle θ2 is limited, is set to the steering end position.

[0072] In the period up to time t_st, the actual steering torque Th_act follows the steering torque target value Th_ref with a substantially constant torque difference ΔT (see FIG. 6E). At this time, the torque difference ΔT (=Th_ref-Th_act) is a positive value. Also, the motor current command value Ih_ref is a positive value, and at this time, a steering reaction force that resists the further right steering is generated in the steering wheel 1 via the column shaft 2.

[0073] When the column angle θ2 reaches the steering end position θ2_end at time t_st and the steering wheel 1 is further steered, the torsion angle Δθ (=θ1-θ2_end) of the torsion bar 2A increases, and the actual steering torque Th_act output from the torque sensor 34 increases (see FIG. 6D). As a result, the actual steering torque Th_act deviates from the steering torque target value Th_ref, and the torque difference ΔTh between the steering torque target value Th_ref and the actual steering torque Th_act changes from a positive value to a negative value (see FIG. 6E).

[0074] At this time, the time change (ΔIh_ref) of the motor current command value Ih_ref turns negative (see Figure 6F), and when the motor current command value Ih_ref becomes negative after time t_re, the steering reaction force that resists the increased right steering is lost, and instead, a steering force (steering assist force) that assists the increased right steering is applied by the reaction force motor 31.

[0075] 4, when further steering is continued at the steering end, a steering force (steering assist force) that assists the further steering is applied by the reaction force motor 31. This may result in an excessive mechanical load being applied to the steering mechanism including the stopper 35 provided at the steering end. Furthermore, with the rotation of the lower end of the column shaft 2 (column angle θ2) inhibited by the stopper 35, an excessive current may flow in the reaction force motor 31, which may result in an increase in power consumption of the reaction force motor 31 and the ECU that constitutes the control device 50.

[0076] A specific configuration and operation for suppressing an increase in mechanical load and power consumption at the steering terminal will be described below.

[0077] (Embodiment 1) Fig. 7 is a block diagram showing an example of the configuration of the steering torque control unit according to embodiment 1. As shown in Fig. 7, the steering torque control unit 400 according to this embodiment includes a subtraction unit 410, a PID control unit 420, an output limiting unit 430, and a current compensation gain calculation unit 440.

[0078] The steering torque control unit 400 receives the steering torque target value Th_ref output from the steering torque target value generation unit 200 and the actual steering torque Th_act detected by the torque sensor 34.

[0079] A subtraction unit 410 calculates a deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act. A PID control unit 420 performs PID control so that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act, which is the calculation result of the subtraction unit 410, approaches zero, and outputs a current command value Iref_a. In the present disclosure, the current command value Iref_a corresponds to a "first current command value."

[0080] The actual steering torque Th_act is input to the current compensation gain calculation unit 440. Based on the actual steering torque Th_act, the current compensation gain calculation unit 440 derives a current compensation gain Gi for suppressing an increase in mechanical load and power consumption at the steering terminal end.

[0081] The output limiting unit 430 is a component that performs output limiting on the current command value Iref_a output from the PID control unit 420 based on the current compensation gain Gi derived by the current compensation gain calculation unit 440. In the present embodiment, the output limiting unit 430 is, for example, a multiplier. The output limiting unit 430 multiplies the current command value Iref_a output from the PID control unit 420 by the current compensation gain Gi derived by the current compensation gain calculation unit 440 to calculate the motor current command value Ih_ref. As a result, the motor current command value Ih_ref in which an increase in mechanical load and power consumption at the steering end is suppressed can be obtained. In the present disclosure, the motor current command value Ih_ref corresponds to the "second current command value".

[0082] FIG. 8 is a block diagram showing a configuration example of the current compensation gain calculation unit according to Embodiment 1. The current compensation gain calculation unit 440 includes a first determination unit 450, a second determination unit 460, and a gain control unit 470.

[0083] The first determination unit 450 derives a first steering end determination flag value Fr1 based on the actual steering torque Th_act.

[0084] Specifically, in the present embodiment, a first torque threshold value Tth1 with respect to the absolute value |Th_act| of the actual steering torque Th_act (hereinafter also simply referred to as "actual steering torque |Th_act|") is set in the first determination unit 450. The first torque threshold value Tth1 is stored, for example, in the ROM of the ECU that constitutes the control device 50.

[0085] When the actual steering torque |Th_act| is less than the first torque threshold value Tth1 (|Th_act| < Tth1), the first determination unit 450 sets the first steering end determination flag value Fr1 to "0" (Fr1 = 0), and when the actual steering torque |Th_act| is greater than or equal to the first torque threshold value Tth1 (Tth1 ≤ |Th_act|), the first determination unit 450 sets the first steering end determination flag value Fr1 to "1" (Fr1 = 0). The first torque threshold value Tth1 can be set, for example, to 7 to 10 [Nm].

[0086] The second determination unit 460 derives a second steering end determination flag value Fr2 based on the actual steering torque Th_act.

[0087] Specifically, in the present embodiment, a second torque threshold value Tth2 for the actual steering torque |Th_act| is set in the second determination unit 460. The second torque threshold value Tth2 is set to a value smaller than the first torque threshold value Tth1 set in the first determination unit 450. The second torque threshold value Tth2 is stored, for example, in the ROM of the ECU that constitutes the control device 50.

[0088] When the actual steering torque |Th_act| is less than the second torque threshold value Tth2 (|Th_act| < Tth2), the second determination unit 460 sets the second steering end determination flag value Fr2 to "1" (Fr2 = 1). When the actual steering torque |Th_act| is greater than or equal to the second torque threshold value Tth2 (Tth2 ≤ |Th_act|), the second determination unit 460 sets the second steering end determination flag value Fr2 to "0" (Fr2 = 0). The second torque threshold value Tth2 can be set to, for example, 4 to 5 [Nm].

[0089] The gain control unit 470 derives a current compensation gain Gi based on the first steering end determination flag value Fr1 derived by the first determination unit 450 and the second steering end determination flag value Fr2 derived by the second determination unit 460.

[0090] Specifically, when the first steering end determination flag value Fr1 derived by the first determination unit 450 changes from "0" to "1", the gain control unit 470 determines that it is at the steering end and transitions the current compensation gain Gi from the first gain (here, "1") to a second gain smaller than the first gain (here, "0"). Also, when the second steering end determination flag value Fr2 derived by the second determination unit 460 changes from "0" to "1", the gain control unit 470 determines that it has missed the steering end and transitions the current compensation gain Gi from the second gain (here, "0") to the first gain (here, "1").

[0091] Hereinafter, a specific operation example of the current compensation gain calculation unit 440 according to Embodiment 1 will be described in detail with reference to FIG. 9. FIG. 9 is a conceptual diagram showing a specific operation example of the current compensation gain calculation unit according to Embodiment 1.

[0092] In FIG. 9, the time changes of the actual steering torque |Th_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when transitioning from the cut-in steering to the cut-back steering at the steering end are illustrated.

[0093] When the actual steering torque |Th_act| becomes equal to or greater than the second torque threshold value Tth2 (Tth2 ≤ |Th_act| < Tth1) at time t1 when the cut-in steering is being performed, the second steering end determination flag value Fr2 changes from "1" to "0".

[0094] At the subsequent time t2, when the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≤ |Th_act|), the first steering end determination flag value Fr1 changes from "0" to "1". At this time, the gain control unit 470 determines that the steering wheel position is at the steering end, and transitions the current compensation gain Gi from "1" to "0". As a result, in the subsequent output limiting unit 430 (see FIG. 7), the current compensation gain Gi "0" derived by the current compensation gain calculation unit 440 is multiplied by the current command value Iref_a output from the PID control unit 420, and the motor current command value Ih_ref becomes "0".

[0095] After time t2, the steering state transitions from the cut-in steering to the cut-back steering. When the actual steering torque |Th_act| becomes less than the first torque threshold value Tth1 (Tth2 ≤ |Th_act| < Tth1) at time t3 when the cut-back steering is being performed, the first steering end determination flag value Fr1 changes from "1" to "0".

[0096] When the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 (|Th_act| < Tth2) at the subsequent time t4, the second steering end determination flag value Fr2 changes from "0" to "1". At this time, the gain control unit 470 determines that the steering end has been missed and transitions the current compensation gain Gi from "0" to "1". As a result, in the subsequent output limiting unit 430 (see FIG. 7), the current compensation gain Gi "1" derived by the current compensation gain calculation unit 440 is multiplied by the current command value Iref_a output from the PID control unit 420, and the current command value Iref_a is output as the motor current command value Ih_ref.

[0097] That is, in the present embodiment, using the actual steering torque Th_act as a parameter, during the increased steering, after the actual steering torque |Th_act| becomes greater than or equal to the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) and then transitions to the return steering, until the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 which is smaller than the first torque threshold value Tth1 (|Th_act| < Tth). The motor current command value Ih_ref is limited to 0 [A] assuming that the steering wheel position is at the steering end. Thereby, the mechanical load applied to the steering mechanism including the stopper 35 at the steering end can be reduced. Also, the current flowing through the reaction force motor 31 at the steering end can be limited, and an increase in the power consumption of the reaction force motor 31 and the ECU constituting the control device 50 can be suppressed.

[0098] Here, as a comparative example, when there is one torque threshold value for the actual steering torque |Th_act|, when the actual steering torque |Th_act| is near the torque threshold value, the motor current command value Ih_ref may oscillate between 0 [A] and the current command value Iref_a. In the present embodiment, after the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) in the increasing steering operation and then transitions to the returning steering operation, until the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 that is smaller than the first torque threshold value Tth1 (|Th_act| < Tth2), assuming that the steering wheel position is at the steering end, the motor current command value Ih_ref is restricted. Thereby, it is possible to prevent the motor current command value Ih_ref from oscillating at the steering end.

[0099] FIG. 10 is a conceptual diagram showing a first modification example of a specific operation example of the current compensation gain calculation unit according to Embodiment 1.

[0100] In the first modification example shown in FIG. 10, the time changes of the actual steering torque |Th_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when the increasing steering operation and the returning steering operation are repeated at the steering end are illustrated.

[0101] In the first modification example shown in FIG. 10, when the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) and the period during which the first steering end determination flag value Fr1 maintains "1" becomes equal to or greater than the first time threshold value tth1, it is determined that the steering wheel position is at the steering end, and the current compensation gain Gi is transitioned from "1" to "0".

[0102] Specifically, as shown in FIG. 10, at time t6, the first steering end determination flag value Fr1 becomes "1", and at time t7 after the first time threshold value tth1 has elapsed, the current compensation gain Gi is transitioned from "1" to "0". The first time threshold value tth1 can be set, for example, to 0.5 to 1.0 [sec].

[0103] Also, in the first modification example shown in FIG. 10, when the actual steering torque |Th_act| is less than the second torque threshold value Tth2 (|Th_act| < Tth2) and the period during which the second steering end determination flag value Fr2 maintains "1" is equal to or greater than the second time threshold value tth2, it is determined that the steering end has been missed, and the current compensation gain Gi is transitioned from "0" to "1".

[0104] Specifically, as shown in FIG. 10, at time t11, the second steering end determination flag value Fr2 becomes "1", and at time t12 after the elapse of the second time threshold value tth2, the current compensation gain Gi is transitioned from "0" to "1". The second time threshold value tth2 can be set, for example, to 0.1 to 0.2 [sec].

[0105] Thereby, when repeatedly performing overshoot steering and return steering at the steering end, it is possible to prevent the motor current command value Ih_ref from frequently switching between the current command value Iref_a and 0 [A].

[0106] Note that the first time threshold value tth1 and the second time threshold value tth2 may be the same value or different values respectively.

[0107] FIG. 11 is a conceptual diagram showing a second modification example of a specific operation example of the current compensation gain calculation unit according to Embodiment 1.

[0108] In the second modification example shown in FIG. 11, similar to the first modification example described above, the time changes of the actual steering torque |Th_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when repeatedly performing overshoot steering and return steering at the steering end are illustrated.

[0109] In the second modification example shown in FIG. 11, when the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≦ |Th_act|) and the period during which the first steering end determination flag value Fr1 maintains "1" becomes equal to or greater than the first time threshold value tth1, it is determined that the steering wheel position is at the steering end, and the current compensation gain Gi is monotonically decreased from "1" to "0" at a predetermined first time change rate.

[0110] Specifically, as shown in FIG. 11, at time t6, the first steering end determination flag value Fr1 becomes "1", and the current compensation gain Gi is monotonically decreased from "1" to "0" until a predetermined period tl1 elapses from time t7 after the first time threshold value tth1 has elapsed.

[0111] Also, in the first modification example shown in FIG. 11, when the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 (|Th_act| < Tth2) and the period during which the second steering end determination flag value Fr2 maintains "1" becomes equal to or greater than the second time threshold value tth2, it is determined that the steering end has been missed, and the current compensation gain Gi is monotonically increased from "0" to "1" at a predetermined second time change rate.

[0112] Specifically, as shown in FIG. 11, at time t11, the second steering end determination flag value Fr2 becomes "1", and the current compensation gain Gi is transitioned from "0" to "1" until a predetermined period tl2 elapses from time t_{12} after the second time threshold value tth2 has elapsed.

[0113] Thereby, it is possible to gently change the motor current command value Ih_ref when the current compensation gain Gi switches between the first gain (here, "1") and the second gain (here, "0").

[0114] The first time change rate and the second time change rate may be the same value with only the sign reversed, or may be different values. Also, the first time change rate and the second time change rate may be fixed values, or may be values that change while the current compensation gain Gi is being monotonically decreased or increased.

[0115] (Embodiment 2) Fig. 12 is a block diagram showing an example of the configuration of a steering torque control unit according to embodiment 2. Fig. 13 is a block diagram showing an example of the configuration of a current compensation gain calculation unit according to embodiment 2. Note that components having the same functions as those in embodiment 1 described above are given the same reference numerals, and description thereof will be omitted.

[0116] In the first embodiment, the parameter for determining whether the steering wheel position is at the steering terminal end is the actual steering torque Th_act, but in this embodiment, a configuration will be described in which the steering terminal end is determined using the actual steering angle θh_act as a parameter.

[0117] The steering torque control unit 400a receives the steering torque target value Th_ref output from the steering torque target value generation unit 200, the actual steering torque Th_act detected by the torque sensor 34, and the actual steering angle θh_act detected by the steering angle sensor 33.

[0118] The actual steering angle θh_act is input to the current compensation gain calculation unit 440a, which derives a current compensation gain Gi based on the actual steering angle θh_act to suppress increases in mechanical load and power consumption at the steering terminal.

[0119] The first determination unit 450a derives a first steering terminal end determination flag value Fr1 based on the actual steering angle θh_act.

[0120] Specifically, in this embodiment, the first determination unit 450a is set with a first steering angle threshold θth1 for the absolute value |θh_act| of the actual steering angle θh_act (hereinafter also simply referred to as "actual steering angle |θh_act|"). The first steering angle threshold θth1 is stored in, for example, a ROM of an ECU constituting the control device 50.

[0121] The first judgment unit 450a sets the first steering end judgment flag value Fr1 to "0" (Fr1 = 0) when the actual steering angle |θh_act| is less than the first steering angle threshold θth1 (|θh_act| < θth1), and sets the first steering end judgment flag value Fr1 to "1" (Fr1 = 0) when the actual steering angle |θh_act| is greater than or equal to the first steering angle threshold θth1 (θth1 ≦ |θh_act|).

[0122] The second determination unit 460a derives a second steering terminal end determination flag value Fr2 based on the actual steering angle θh_act.

[0123] Specifically, in this embodiment, second determination unit 460a sets a second steering angle threshold θth2 for actual steering angle |θh_act|. Second steering angle threshold θth2 is set to a value smaller than first steering angle threshold θth1 set in first determination unit 450a. Second steering angle threshold θth2 is stored in, for example, a ROM of an ECU constituting control device 50.

[0124] The second judgment unit 460a sets the second steering end judgment flag value Fr2 to "1" (Fr2 = 1) when the actual steering angle |θh_act| is less than the second steering angle threshold θth2 (|θh_act| < θth2), and sets the second steering end judgment flag value Fr2 to "0" (Fr2 = 0) when the actual steering angle |θh_act| is greater than or equal to the second steering angle threshold θth2 (θth2 ≦ |θh_act|).

[0125] A specific example of the operation of the current compensation gain calculation unit 440a according to the second embodiment will be described in detail below with reference to Fig. 14. Fig. 14 is a conceptual diagram showing a specific example of the operation of the current compensation gain calculation unit according to the second embodiment.

[0126] FIG. 14 illustrates the time changes of the actual steering angle |θh_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when transitioning from further steering to return steering at the steering end.

[0127] When the actual steering angle |θh_act| becomes equal to or greater than the second steering angle threshold θth2 (θth2≦|θh_act|<θth1) at time t1 when further steering is being performed, the second steering terminal determination flag value Fr2 changes from “1” to “0”.

[0128] At the next time t2, when the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|), the first steering end determination flag value Fr1 changes from “0” to “1.” At this time, the gain control unit 470 determines that the steering wheel position is at the steering end terminal, and changes the current compensation gain Gi from “1” to “0.” As a result, in the output limiting unit 430 (see FIG. 12) at the subsequent stage, the current command value Iref_a output from the PID control unit 420 is multiplied by the current compensation gain Gi “0” derived by the current compensation gain calculation unit 440a, and the motor current command value Ih_ref becomes “0.”

[0129] After time t2, the steering state transitions from increasing steering to returning steering. When the actual steering angle |θh_act| becomes less than the first steering angle threshold θth1 (θth2≦|θh_act|<θth1) at time t3 while returning steering is being performed, the first steering end determination flag value Fr1 changes from “1” to “0.”

[0130] At the following time t4, when the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2), the second steering end determination flag value Fr2 changes from "0" to "1." At this time, the gain control unit 470 determines that the steering end has been missed, and changes the current compensation gain Gi from "0" to "1." As a result, in the output limiting unit 430 (see FIG. 12) at the subsequent stage, the current command value Iref_a output from the PID control unit 420 is multiplied by the current compensation gain Gi "1" derived by the current compensation gain calculation unit 440a, and the current command value Iref_a is output as the motor current command value Ih_ref.

[0131] That is, in this embodiment, the actual steering angle θh_act is used as a parameter, and during further steering, after the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|), and the steering wheel transitions to return steering, the steering wheel position is considered to be at the steering terminal end until the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2), which is smaller than the first steering angle threshold θth1, and the motor current command value Ih_ref is limited to 0 [A]. This makes it possible to reduce the mechanical load applied to the steering mechanism including the stopper 35 at the steering terminal end. Furthermore, it is possible to limit the current flowing to the reaction force motor 31 at the steering terminal end, and to suppress an increase in power consumption of the reaction force motor 31 and the ECU constituting the control device 50.

[0132] Although omitted in this embodiment, a specific example of the operation of the current compensation gain calculation unit according to the second embodiment may be the same as the first modified example of the first embodiment or the second modified example of the first embodiment.

[0133] That is, for example, when the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|) and the period during which the first steering end determination flag value Fr1 maintains "1" becomes equal to or greater than the first time threshold tth1, the gain control unit 470 may determine that the steering position is at the steering end and transition the current compensation gain Gi from "1" to "0", and when the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2) and the period during which the second steering end determination flag value Fr2 maintains "1" becomes equal to or greater than the second time threshold tth2, the gain control unit 470 may determine that the steering end has been missed and transition the current compensation gain Gi from "0" to "1".

[0134] Further, for example, when the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|) and the period during which the first steering end determination flag value Fr1 maintains "1" becomes equal to or greater than the first time threshold tth1, the gain control unit 470 may determine that the steering wheel position is at the steering end and monotonically decrease the current compensation gain Gi from "1" to "0" at a predetermined first time change rate, and when the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2) and the period during which the second steering end determination flag value Fr2 maintains "1" becomes equal to or greater than the second time threshold tth2, the gain control unit 470 may determine that the steering end has been missed and monotonically increase the current compensation gain Gi from "0" to "1" at a predetermined second time change rate.

[0135] (Embodiment 3) Fig. 15 is a block diagram showing an example of the configuration of a steering torque control unit according to embodiment 3. Fig. 16 is a block diagram showing an example of the configuration of a current compensation gain calculation unit according to embodiment 3. Note that components having the same functions as those in the above-described embodiments are given the same reference numerals, and description thereof will be omitted.

[0136] In the third embodiment, a configuration will be described in which the actual steering torque Th_act and the actual steering angle θh_act are used as parameters for determining whether the steering wheel position is at the steering end terminal.

[0137] As in embodiment 2, the steering torque control unit 400b receives as input the steering torque target value Th_ref output from the steering torque target value generation unit 200, the actual steering torque Th_act detected by the torque sensor 34, and the actual steering angle θh_act detected by the steering angle sensor 33.

[0138] The actual steering torque Th_act and the actual steering angle θh_act are input to the current compensation gain calculation unit 440b, which derives a current compensation gain Gi based on the actual steering torque Th_act and the actual steering angle θh_act to suppress increases in mechanical load and power consumption at the steering terminal.

[0139] The first determination unit 450b derives a first steering end determination flag value Fr1 based on the actual steering torque Th_act and the actual steering angle θh_act.

[0140] Specifically, in the present embodiment, a first torque threshold value Tth1 for the actual steering torque |Th_act| and a first steering angle threshold value θth1 for the actual steering angle |θh_act| are set in the first determination unit 450b. The first torque threshold value Tth1 and the first steering angle threshold value θth1 are stored, for example, in the ROM of the ECU that constitutes the control device 50.

[0141] When the actual steering torque |Th_act| is less than the first torque threshold value Tth1 (|Th_act| < Tth1) or the actual steering angle |θh_act| is less than the first steering angle threshold value θth1 (|θh_act| < θth1), the first determination unit 450b sets the first steering end determination flag value Fr1 to "0" (Fr1 = 0). When the actual steering torque |Th_act| is greater than or equal to the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) and the actual steering angle |θh_act| is greater than or equal to the first steering angle threshold value θth1 (θth1 ≤ |θh_act|), the first steering end determination flag value Fr1 is set to "1" (Fr1 = 0).

[0142] The second determination unit 460b derives a second steering end determination flag value Fr2 based on the actual steering torque Th_act and the actual steering angle θh_act.

[0143] Specifically, in the present embodiment, a second torque threshold value Tth2 for the actual steering torque |Th_act| and a second steering angle threshold value θth2 for the actual steering angle |θh_act| are set in the second determination unit 460b. The second torque threshold value Tth2 is set to a value smaller than the first torque threshold value Tth1 set in the first determination unit 450b. The second steering angle threshold value θth2 is set to a value smaller than the first steering angle threshold value θth1 set in the first determination unit 450b. The second torque threshold value Tth2 and the second steering angle threshold value θth2 are stored, for example, in the ROM of the ECU that constitutes the control device 50.

[0144] When the actual steering torque |Th_act| is less than the second torque threshold value Tth2 (|Th_act| < Tth2), or when the actual steering angle |θh_act| is less than the second steering angle threshold value θth2 (|θh_act| < θth2), the second steering end determination flag value Fr2 is set to "1" (Fr2 = 1). When the actual steering torque |Th_act| is greater than or equal to the second torque threshold value Tth2 and the actual steering angle |θh_act| is greater than or equal to the second steering angle threshold value θth2 (θth2 ≤ |θh_act|), the second steering end determination flag value Fr2 is set to "0" (Fr2 = 0).

[0145] Hereinafter, a specific operation example of the current compensation gain calculation unit 440b according to Embodiment 3 will be described in detail with reference to FIGS. 17A, 17B, 17C, and 17D. FIG. 17A is a conceptual diagram showing a specific operation example of the current compensation gain calculation unit according to Embodiment 3. FIG. 17B is a conceptual diagram showing a first modification example of the specific operation example of the current compensation gain calculation unit according to Embodiment 3. FIG. 17C is a conceptual diagram showing a second modification example of the specific operation example of the current compensation gain calculation unit according to Embodiment 3. FIG. 17D is a conceptual diagram showing a third modification example of the specific operation example of the current compensation gain calculation unit according to Embodiment 3.

[0146] In FIGS. 17A, 17B, 17C, and 17D, the time changes of the actual steering torque |Th_act|, the actual steering angle |θh_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when transitioning from the over-steering to the return-steering at the steering end are illustrated.

[0147] When, at time t2 during the oversteering operation, the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) and the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold value θth1 (θth1 ≤ |θh_act|), the first steering end determination flag value Fr1 changes from "0" to "1". At this time, the gain control unit 470 determines that the steering wheel position is at the steering end and transitions the current compensation gain Gi from "1" to "0". As a result, in the subsequent output limiting unit 430 (see FIG. 15), the current compensation gain Gi "0" derived by the current compensation gain calculation unit 440b is multiplied by the current command value Iref_a output from the PID control unit 420, and the motor current command value Ih_ref becomes "0".

[0148] After time t2, the steering state transitions from oversteering to return steering. When, at time t4 during the return steering operation, the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 (|Th_act| < Tth2) or the actual steering angle |θh_act| becomes less than the second steering angle threshold value θth2 (|θh_act| < θth2), the second steering end determination flag value Fr2 changes from "0" to "1". At this time, the gain control unit 470 determines that the steering end has been missed and transitions the current compensation gain Gi from "0" to "1". As a result, in the subsequent output limiting unit 430 (see FIG. 15), the current compensation gain Gi "1" derived by the current compensation gain calculation unit 440b is multiplied by the current command value Iref_a output from the PID control unit 420, and the current command value Iref_a is output as the motor current command value Ih_ref.

[0149] That is, in the present embodiment, with the actual steering torque Th_act and the actual steering angle θh_act as parameters, during the cut-in steering, after the actual steering torque |Th_act| becomes equal to or greater than the first torque threshold value Tth1 (Tth1 ≤ |Th_act|) and the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold value θth1 (θth1 ≤ |θh_act|), and after transitioning to the return steering, until the actual steering torque |Th_act| becomes less than the second torque threshold value Tth2 (|Th_act| < Tth2) or the actual steering angle |θh_act| becomes less than the second steering angle threshold value θth2 which is smaller than the first steering angle threshold value θth1 (|θh_act| < θth2), the motor current command value Ih_ref is restricted to 0 [A] on the assumption that the steering wheel position is at the steering end. Thereby, the mechanical load applied to the steering mechanism including the stopper 35 at the steering end can be reduced. Also, the current flowing through the reaction force motor 31 at the steering end can be restricted, and an increase in the power consumption of the reaction force motor 31 and the ECU constituting the control device 50 can be suppressed.

[0150] Although omitted in the present embodiment, as a specific operation example of the current compensation gain calculation unit according to Embodiment 3, it may be in the same manner as the first modification example of Embodiment 1 or the second modification example of Embodiment 1.

[0151] That is, for example, when the actual steering torque |Th_act| is greater than or equal to the first torque threshold value Tth1 (Tth1 ≤ |Th_act|), the actual steering angle |θh_act| is greater than or equal to the first steering angle threshold value θth1 (θth1 ≤ |θh_act|), and the period during which the first steering end determination flag value Fr1 maintains "1" is greater than or equal to the first time threshold value tth1, it is determined that the steering wheel position is at the steering end, and the current compensation gain Gi is transitioned from "1" to "0". When the actual steering torque |Th_act| is less than the second torque threshold value Tth2 (|Th_act| < Tth2), or the actual steering angle |θh_act| is less than the second steering angle threshold value θth2 (|θh_act| < θth2), and the period during which the second steering end determination flag value Fr2 maintains "1" is greater than or equal to the second time threshold value tth2, it may be determined that the steering end has been missed, and the current compensation gain Gi is transitioned from "0" to "1".

[0152] Also, for example, when the actual steering torque |Th_act| is greater than or equal to the first torque threshold value Tth1 (Tth1 ≤ |Th_act|), the actual steering angle |θh_act| is greater than or equal to the first steering angle threshold value θth1 (θth1 ≤ |θh_act|), and the period during which the first steering end determination flag value Fr1 maintains "1" is greater than or equal to the first time threshold value tth1, it is determined that the steering wheel position is at the steering end, and the current compensation gain Gi is monotonically decreased from "1" to "0" at a predetermined first time change rate. When the actual steering torque |Th_act| is less than the second torque threshold value Tth2 (|Th_act| < Tth2), or the actual steering angle |θh_act| is less than the second steering angle threshold value θth2 (|θh_act| < θth2), and the period during which the second steering end determination flag value Fr2 maintains "1" is greater than or equal to the second time threshold value tth2, it may be determined that the steering end has been missed, and the current compensation gain Gi is monotonically increased from "0" to "1" at a predetermined second time change rate.

[0153] (Embodiment 4) Fig. 18 is a block diagram showing an example of the configuration of a steering torque control unit according to embodiment 4. Fig. 19 is a block diagram showing an example of the configuration of a current compensation gain calculation unit according to embodiment 4. Note that components having the same functions as those in the above-described embodiments are given the same reference numerals, and description thereof will be omitted.

[0154] In the fourth embodiment, a configuration will be described in which the actual steering angle θh_act and the actual steering angular velocity ωh_act are used as parameters for determining whether the steering wheel position is at the steering end terminal.

[0155] As in the second and third embodiments, the steering torque control unit 400c receives the steering torque target value Th_ref output from the steering torque target value generation unit 200, the actual steering torque Th_act detected by the torque sensor 34, and the actual steering angle θh_act detected by the steering angle sensor 33.

[0156] The actual steering angle θh_act is input to the current compensation gain calculation unit 440c. The actual steering angle θh_act is differentiated by a differentiation unit 480 of the current compensation gain calculation unit 440c to derive the actual steering angular velocity ωh_act. The current compensation gain calculation unit 440c derives a current compensation gain Gi for suppressing increases in mechanical load and power consumption at the steering terminal based on the actual steering angle θh_act and the actual steering angular velocity ωh_act. Note that the actual steering angular velocity ωh_act is not limited to being derived by differentiating the actual steering angle θh_act.

[0157] The first determination unit 450c derives a first steering terminal end determination flag value Fr1 based on the actual steering angle θh_act and the actual steering angular velocity ωh_act.

[0158] Specifically, in the present embodiment, the first determination unit 450c is set with a first steering angle threshold θth1 for the actual steering angle |θh_act| and a first steering angular velocity threshold ωth1 for the absolute value |ωh_act| of the actual steering angular velocity ωh_act (hereinafter also simply referred to as "actual steering angular velocity |ωh_act|"). The first steering angle threshold θth1 and the first steering angular velocity threshold ωth1 are stored in, for example, a ROM of an ECU constituting the control device 50.

[0159] The first judgment unit 450c sets the first steering terminal determination flag value Fr1 to "0" (Fr1 = 0) when the actual steering angle |θh_act| is less than the first steering angle threshold θth1 (|θh_act| < θth1) or the actual steering angular velocity |ωh_act| is greater than the first steering angular velocity threshold ωth1 (ωth < |ωh_act|), and sets the first steering terminal determination flag value Fr1 to "1" (Fr1 = 0) when the actual steering angle |θh_act| is greater than the first steering angle threshold θth1 (θth1 ≦ |θh_act|) and the actual steering angular velocity |ωh_act| is less than the first steering angular velocity threshold ωth1 (|ωh_act| ≦ ωth1).

[0160] The second determination unit 460c derives a second steering terminal end determination flag value Fr2 based on the actual steering angle θh_act and the actual steering angular velocity ωh_act.

[0161] Specifically, in the present embodiment, second determination unit 460c is set with a second steering angle threshold θth2 for the actual steering angle |θh_act| and a second steering angular velocity threshold ωth2 for the actual steering angular velocity |ωh_act|. The second steering angle threshold θth2 is set to a value smaller than the first steering angle threshold θth1 set in first determination unit 450b. The second steering angular velocity threshold ωth2 is set to a value larger than the first steering angular velocity threshold ωth1 set in first determination unit 450c. The second steering angle threshold θth2 and the second steering angle threshold θth2 are stored, for example, in a ROM of an ECU constituting control device 50.

[0162] The second judgment unit 460c sets the second steering terminal determination flag value Fr2 to "1" (Fr2 = 1) when the actual steering angle |θh_act| is less than the second steering angle threshold θth2 (|θh_act| < θth2) or when the actual steering angular velocity |ωh_act| is greater than the second steering angular velocity threshold ωth2 (ωth2 < |ωh_act|), and sets the second steering terminal determination flag value Fr2 to "0" (Fr2 = 0) when the actual steering angle |θh_act| is greater than or equal to the second steering angle threshold θth2 (θth2 ≦ |θh_act|) and the actual steering angular velocity |ωh_act| is less than or equal to the second steering angular velocity threshold ωth2 (|ωh_act| ≦ ωth2).

[0163] A specific operation example of the current compensation gain calculation unit 440c according to the fourth embodiment will be described in detail below with reference to FIGS. 20A, 20B, 20C, and 20D. FIG. 20A is a conceptual diagram showing a specific operation example of the current compensation gain calculation unit according to the fourth embodiment. FIG. 20B is a conceptual diagram showing a first modified example of the specific operation example of the current compensation gain calculation unit according to the fourth embodiment. FIG. 20C is a conceptual diagram showing a second modified example of the specific operation example of the current compensation gain calculation unit according to the fourth embodiment. FIG. 20D is a conceptual diagram showing a third modified example of the specific operation example of the current compensation gain calculation unit according to the fourth embodiment.

[0164] Figures 20A, 20B, 20C, and 20D illustrate examples of the time changes of the actual steering angle |θh_act|, the actual steering angular velocity |ωh_act|, the first steering end determination flag value Fr1, the second steering end determination flag value Fr2, and the current compensation gain Gi when transitioning from further steering to return steering at the steering end.

[0165] At time t2 when further steering is being performed, when the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|) and the actual steering angular velocity |ωh_act| becomes equal to or less than the first steering angular velocity threshold ωth1 (|ωh_act|≦ωth1), the first steering end determination flag value Fr1 changes from “0” to “1.” At this time, the gain control unit 470 determines that the steering wheel position is at the steering end end, and changes the current compensation gain Gi from “1” to “0.” As a result, in the output limiting unit 430 (see FIG. 18) at the subsequent stage, the current command value Iref_a output from the PID control unit 420 is multiplied by the current compensation gain Gi “0” derived by the current compensation gain calculation unit 440c, and the motor current command value Ih_ref becomes “0.”

[0166] After time t2, the steering state transitions from increasing steering to returning steering, and at time t4 when returning steering is being performed, if the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2) or the actual steering angular velocity |ωh_act| becomes greater than the second steering angular velocity threshold ωth2 (ωth2<|ωh_act|), the second steering terminal end determination flag value Fr2 changes from "0" to "1." At this time, gain control unit 470 determines that the steering terminal end has been missed, and transitions current compensation gain Gi from "0" to "1." As a result, in the output limiting unit 430 (see Figure 18) in the subsequent stage, the current command value Iref_a output from the PID control unit 420 is multiplied by the current compensation gain Gi "1" derived by the current compensation gain calculation unit 440c, and the current command value Iref_a is output as the motor current command value Ih_ref.

[0167] That is, in this embodiment, with the actual steering angle θh_act and the actual steering angular velocity ωh_act as parameters, during further steering, after the actual steering angle |θh_act| becomes equal to or greater than the first steering angle threshold θth1 (θth1≦|θh_act|) and the actual steering angular velocity |ωh_act| becomes equal to or less than the first steering angular velocity threshold ωth1 (|ωh_act|≦ωth1) and then transitions to return steering, the steering wheel position is considered to be at the steering end point until the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2) which is smaller than the first steering angle threshold θth1, or the actual steering angular velocity |ωh_act| becomes greater than the second steering angular velocity threshold ωth2 (ωth2<|ωh_act|), and the motor current command value Ih_ref is limited to 0 [A]. This reduces the mechanical load on the steering mechanism including the stopper 35 at the steering terminal end. Also, the current flowing to the reaction force motor 31 at the steering terminal end can be limited, thereby suppressing an increase in power consumption of the reaction force motor 31 and the ECU constituting the control device 50.

[0168] Although omitted in this embodiment, a specific example of the operation of the current compensation gain calculation unit according to the fourth embodiment may be the same as the first modified example of the first embodiment or the second modified example of the first embodiment.

[0169] That is, when the actual steering angle |θh_act| becomes equal to or larger than the first steering angle threshold θth1 (θth1≦|θh_act|), and the actual steering angular velocity |ωh_act| becomes equal to or smaller than the first steering angular velocity threshold ωth1 (|ωh_act|≦ωth1), and the period during which the first steering terminal determination flag value Fr1 is maintained at “1” becomes equal to or larger than the first time threshold tth1, the gain control unit 470 determines that the steering wheel position is at the steering terminal end and changes the current compensation gain Gi from “1” to “0.” Alternatively, when the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2), or the actual steering angular velocity |ωh_act| becomes greater than the second steering angular velocity threshold ωth2 (ωth2<|ωh_act|), and the period during which the second steering end determination flag value Fr2 is maintained at "1" becomes equal to or longer than the second time threshold tth2, it may be determined that the steering end has been missed and the current compensation gain Gi may be transitioned from "0" to "1".

[0170] Further, for example, when the actual steering angle |θh_act| becomes equal to or larger than the first steering angle threshold θth1 (θth1≦|θh_act|), and the actual steering angular velocity |ωh_act| becomes equal to or smaller than the first steering angular velocity threshold ωth1 (|ωh_act|≦ωth1), and the period during which the first steering end determination flag value Fr1 is maintained at “1” becomes equal to or larger than the first time threshold tth1, the gain control unit 470 determines that the steering wheel position is at the steering end and monotonically changes the current compensation gain Gi from “1” to “0” at a predetermined first time change rate. Alternatively, when the actual steering angle |θh_act| becomes less than the second steering angle threshold θth2 (|θh_act|<θth2), or the actual steering angular velocity |ωh_act| becomes greater than the second steering angular velocity threshold ωth2 (ωth2<|ωh_act|), and the period during which the second steering end determination flag value Fr2 is maintained at "1" becomes equal to or greater than the second time threshold tth2, it may be determined that the steering end has been missed and the current compensation gain Gi may be monotonically increased from "0" to "1" at a predetermined second time change rate.

[0171] (Embodiment 5) Fig. 21 is a block diagram showing a configuration example of an output limiting unit according to embodiment 5. In each of the above-described embodiments, an example has been described in which the output limiting unit 430 is a multiplier, but by using the configuration shown in Fig. 21, it is possible to suppress a sudden fluctuation in the motor current command value Ih_ref at the steering terminal end.

[0172] Specifically, the output limiting unit 430 a according to the fifth embodiment includes a sign extracting unit 431 , an absolute value calculating unit 432 , a multiplying unit 433 , a current command value lower limit setting unit 434 , a comparing unit 435 , and a multiplying unit 436 .

[0173] The sign extraction unit 431 extracts the sign of the current command value Iref_a output from the PID control unit 420. Specifically, for example, the value of the current command value Iref_a is divided by the absolute value of the current command value Iref_a. As a result, the sign extraction unit 431 outputs "1" when the sign of the current command value Iref_a is "+", and outputs "-1" when the sign of the current command value Iref_a is "-". Specifically, the sign extraction unit 431 generates, for example, a sign function Sgn(Iref_a) of the current command value Iref_a.

[0174] The absolute value calculation unit 432 performs absolute value processing on the current command value Iref_a. The current command value |Iref_a| that has been subjected to absolute value processing in the absolute value calculation unit 432 is input to the multiplication unit 433. The multiplication unit 433 outputs a current command value |Iref_a|×Gi obtained by multiplying the current command value |Iref_a| by a current compensation gain Gi. In the present disclosure, the current command value |Iref_a|×Gi corresponds to a "third current command value."

[0175] A lower limit value Iref_lower_lim for the current command value |Iref_a| is set in the current command value lower limit value setting unit 434. The current command value lower limit value Iref_lower_lim is stored in the ROM of the ECU constituting the control device 50, for example.

[0176] The comparison unit 435 performs a comparison operation between the current command value |Iref_a|×Gi and the current command value lower limit value Iref_lower_lim. Specifically, the comparison unit 435 outputs the current command value |Iref_a|×Gi when the following formula (1) is satisfied, and outputs the current command value lower limit value Iref_lower_lim when the following formula (2) is satisfied.

[0177] |Iref_a|×Gi>Iref_lower_lim···(1)

[0178] |Iref_a|×Gi≦Iref_lower_lim···(2)

[0179] A multiplication unit 436 multiplies the output value of the comparison unit 435 by a sign function Sgn(Iref_a) of the current command value Iref_a, and outputs the result as a motor current command value Ih_ref.

[0180] Due to the configuration of the output limiting unit 430a according to the fifth embodiment, the lower limit of the motor current command value |Ih_ref| is limited to the current command value lower limit value Iref_lower_lim regardless of the current compensation gain Gi, thereby making it possible to suppress abrupt fluctuations in the motor current command value Ih_ref at the steering end point.

[0181] (Embodiment 6) 22 is a block diagram showing a configuration example of an output limiting unit according to embodiment 6. Note that components having the same functions as those in embodiment 5 described above are given the same reference numerals and descriptions thereof will be omitted.

[0182] In the fifth embodiment, the lower limit value of the motor current command value |Ih_ref| is limited to the current command value lower limit value Iref_lower_lim. In the present embodiment, however, a mode in which the upper limit value of the motor current command value |Ih_ref| is further limited according to the current compensation gain Gi will be described.

[0183] Specifically, the output limiting unit 430b according to the sixth embodiment includes a sign extraction unit 431, an absolute value calculation unit 432, a current command value lower limit value setting unit 434, a multiplication unit 436, a current command value upper limit value generation unit 437, a first comparison unit 438, and a second comparison unit 439.

[0184] The current compensation gain Gi and the current command value lower limit Iref_lower_lim are input to the current command value upper limit generator 437. Fig. 23 is a block diagram showing an example of the internal configuration of the current command value upper limit generator according to the sixth embodiment.

[0185] Furthermore, a maximum value Iref_lim_max for the current command value |Iref_a| is set in the current command value upper limit value generating unit 437. The maximum current command value Iref_lim_max is stored, for example, in the ROM of the ECU constituting the control device 50. In the present disclosure, the lower limit current command value Iref_lower_lim is set, for example, to about 10[%] of the maximum current command value Iref_lim_max.

[0186] The current command value upper limit value generator 437 generates a current command value upper limit value Iref_upper_lim according to the current compensation gain Gi. In the current command value upper limit value generator 437 having the configuration shown in Fig. 23, the current command value upper limit value Iref_upper_lim is expressed by the following equation (3).

[0187] Iref_upper_lim=(Iref_lim_max-Iref_lower_lim)×Gi+Iref_lower_lim···(3)

[0188] The current command value upper limit generating unit 437 may calculate the current command value upper limit Iref_upper_lim using the above equation (3), or may store the input / output characteristics obtained by the above equation (3) as a map and derive the current command value upper limit Iref_upper_lim based on the map. Fig. 24 is a diagram showing an example of the input / output characteristics of the current command value upper limit generating unit according to the sixth embodiment.

[0189] The first comparing unit 438 performs a comparison operation between the current command value |Iref_a| and the current command value upper limit value Iref_upper_lim. Specifically, the first comparing unit 438 outputs the current command value |Iref_a| when the following formula (4) is satisfied, and outputs the current command value upper limit value Iref_upper_lim when the following formula (5) is satisfied.

[0190] |Iref_a|≦Iref_upper_lim···(4)

[0191] |Iref_a|>Iref_upper_lim···(5)

[0192] The second comparing unit 439 performs a comparison operation between the output value Comp_a of the first comparing unit 438 and the current command value lower limit value Iref_lower_lim. Specifically, the comparing unit 435 outputs the output value Comp_a of the first comparing unit 438 when the following formula (6) is satisfied, and outputs the current command value lower limit value Iref_lower_lim when the following formula (7) is satisfied. In the present disclosure, the output value Comp_a of the first comparing unit 438 corresponds to the "third current command value."

[0193] Comp_a>Iref_lower_lim···(6)

[0194] Comp_a≦Iref_lower_lim···(7)

[0195] A multiplication unit 436 multiplies the output value of the second comparison unit 439 by a sign function Sgn(Iref_a) of the current command value Iref_a, and outputs the result as a motor current command value Ih_ref.

[0196] The configuration of the output limiting unit 430b according to the sixth embodiment limits the upper limit of the motor current command value |Ih_ref| to the current command value upper limit value Iref_upper_lim according to the current compensation gain Gi, thereby making it possible to suppress unnecessary fluctuations in the motor current command value Ih_ref due to noise or the like.

[0197] 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]

[0198] 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 200 Steering torque target value generation unit 400, 400a, 400b, 400c Steering torque control section 410 Subtraction section 420 PID control unit 430, 430a, 430b Output limiter 431 Code extraction part 432 Absolute value calculation unit 433 Multiplication section 434 Current command lower limit setting unit 435 Comparison Section 436 Multiplication Unit 437 Current command upper limit value generation unit 438 First Comparison Section 439 Second Comparison Section 440, 440a, 440b, 440c Current compensation gain calculation unit 450, 450a, 450b, 450c First Judgment Section 460,460a,460b,460c 2nd judgment section 470 Gain control section 500 Current control section 600 steering angle target value generation unit 700 Steering angle control unit 800 Current control section

Claims

1. A control device for a vehicle steering system, comprising a steering mechanism having a reaction force motor that applies a steering reaction force to a steering wheel in accordance with the steering angle of the steering wheel, and a steering mechanism having a steering motor that steers steered wheels in accordance with the steering angle of the steering wheel, a rotation limiting mechanism that limits the rotation of the steering wheel while the steering mechanism and the turning mechanism are mechanically separated is provided at the steering end of the steering wheel, a steering torque target value generating unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force; a steering torque control unit that generates a first current command value based on the steering torque target value; Equipped with The steering torque control unit a current compensation gain calculation unit that detects that the rotation of the steering wheel is limited by the rotation limiting mechanism and derives a current compensation gain that limits the first current command value; an output limiting unit that generates a second current command value by limiting the first current command value based on the current compensation gain, and outputs the second current command value as a motor current command value for driving the reaction force motor; Equipped with A control device for a vehicle steering system.

2. The current compensation gain calculation unit When an actual steering torque, which is an actual steering torque of the steering wheel, is equal to or greater than a first torque threshold, it is determined that the rotation of the steering wheel is limited by the rotation limiting mechanism, and determining that the steering end point has been missed when the actual steering torque becomes less than a second torque threshold value that is smaller than the first torque threshold value after determining that the rotation of the steering wheel has been limited by the rotation limiting mechanism.

2. The control device for a vehicle steering system according to claim 1.

3. The current compensation gain calculation unit determining that the rotation of the steering wheel is limited by the rotation limiting mechanism when an actual steering torque, which is an actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold and a predetermined first time period has elapsed; After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering torque becomes less than a second torque threshold that is smaller than the first torque threshold and a predetermined second time period has elapsed, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

4. The current compensation gain calculation unit When an actual steering angle, which is an actual steering angle of the steering wheel, is equal to or greater than a first steering angle threshold, it is determined that the rotation of the steering wheel is limited by the rotation limiting mechanism, and determining that the steering end point has been missed when the actual steering angle becomes less than a second steering angle threshold value that is smaller than the first steering angle threshold value after determining that the rotation of the steering wheel has been limited by the rotation limiting mechanism.

2. The control device for a vehicle steering system according to claim 1.

5. The current compensation gain calculation unit When an actual steering angle, which is an actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold and a predetermined first time period has elapsed, it is determined that rotation of the steering wheel has been limited by the rotation limiting mechanism, After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold and a predetermined second time period has elapsed, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

6. The current compensation gain calculation unit determining that the rotation of the steering wheel is limited by the rotation limiting mechanism when an actual steering torque, which is an actual steering torque of the steering wheel, is equal to or greater than a first torque threshold value and an actual steering angle, which is an actual steering angle of the steering wheel, is equal to or greater than a first steering angle threshold value; After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering torque becomes less than a second torque threshold value that is smaller than the first torque threshold value, or if the actual steering angle becomes less than a second steering angle threshold value that is smaller than the first steering angle threshold value, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

7. The current compensation gain calculation unit determining that the rotation of the steering wheel is limited by the rotation limiting mechanism when an actual steering torque, which is an actual steering torque of the steering wheel, becomes equal to or greater than a first torque threshold value, and an actual steering angle, which is an actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold value, and a predetermined first time period has elapsed; After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering torque becomes less than a second torque threshold value that is smaller than the first torque threshold value, or the actual steering angle becomes less than a second steering angle threshold value that is smaller than the first steering angle threshold value, and a predetermined second time period has elapsed, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

8. The current compensation gain calculation unit determining that the rotation of the steering wheel is limited by the rotation limiting mechanism when an actual steering angle, which is an actual steering angle of the steering wheel, is equal to or greater than a first steering angle threshold and an actual steering angular velocity, which is an actual steering angular velocity of the steering wheel, is equal to or less than a first steering angular velocity threshold; After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering angle becomes less than a second steering angle threshold value that is smaller than the first steering angle threshold value, or if the actual steering angular velocity becomes greater than a second steering angular velocity that is greater than the first steering angular velocity threshold value, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

9. The current compensation gain calculation unit determining that the rotation of the steering wheel has been limited by the rotation limiting mechanism when an actual steering angle, which is the actual steering angle of the steering wheel, becomes equal to or greater than a first steering angle threshold, and an actual steering angular velocity, which is the actual steering angular velocity of the steering wheel, becomes equal to or less than a first steering angular velocity threshold, and a predetermined first time period has elapsed; After determining that the rotation of the steering wheel is limited by the rotation limiting mechanism, if the actual steering angle becomes less than a second steering angle threshold that is smaller than the first steering angle threshold, or the actual steering angular velocity becomes greater than a second steering angular velocity that is larger than the first steering angular velocity threshold, and a predetermined second time period has elapsed, it is determined that the steering end point has been missed.

2. The control device for a vehicle steering system according to claim 1.

10. The current compensation gain calculation unit when it is determined that the rotation of the steering wheel is limited by the rotation limiting mechanism, the current compensation gain is transitioned from a first gain to a second gain smaller than the first gain; when it is determined that the steering end point has been missed, the current compensation gain is transitioned from the second gain to the first gain; The control device for a vehicle steering system according to any one of claims 1 to 9.

11. The current compensation gain calculation unit when it is determined that the rotation of the steering wheel is limited by the rotation limiting mechanism, the current compensation gain is monotonically decreased from a first gain to a second gain smaller than the first gain at a predetermined first time change rate; when it is determined that the steering end point has been missed, the current compensation gain is monotonically increased from the second gain to the first gain at a predetermined second time change rate; The control device for a vehicle steering system according to any one of claims 1 to 9.

12. The output limiting unit multiplying the first current command value by the current compensation gain to generate the second current command value; The control device for a vehicle steering system according to any one of claims 1 to 11.

13. The output limiting unit limiting a lower limit value of the second current command value; The control device for a vehicle steering system according to any one of claims 1 to 11.

14. The output limiting unit a comparison unit that compares a third current command value obtained by multiplying the first current command value by the current compensation gain with a predetermined current command value lower limit value, The comparison unit When the third current command value is greater than the current command lower limit value, the third current command value is output as the second current command value; When the third current command value is equal to or less than the current command lower limit value, the current command lower limit value is output as the second current command value. The control device for a vehicle steering system according to claim 13.

15. The output limiting unit limiting an upper limit value and a lower limit value of the second current command value; The control device for a vehicle steering system according to any one of claims 1 to 12.

16. The output limiting unit a first comparison unit that compares the first current command value with a predetermined current command value upper limit; a second comparison unit that compares a third current command value, which is an output value of the first comparison unit, with a predetermined lower limit value of the current command value; Equipped with The first comparison unit When the first current command value is equal to or less than the current command value upper limit, the first current command value is output; When the first current command value is greater than the current command lower limit value, the current command upper limit value is output; The second comparison unit When the third current command value is greater than the current command lower limit value, the third current command value is output as the second current command value; When the third current command value is equal to or less than the current command lower limit value, the current command lower limit value is output as the second current command value. The control device for a vehicle steering system according to claim 15.

17. The output limiting unit a current command value upper limit generating unit that generates the current command value upper limit, The current command value upper limit value generation unit monotonically increasing the current command value upper limit value from the current command value lower limit value to a predetermined current command value maximum value as the current compensation gain increases; The control device for a vehicle steering system according to claim 16.

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