Steer-by-wire steering reaction device

Abstract

To provide a steer-by-wire steering reaction force device capable of minimizing an influence of vehicle characteristics and easily setting target steering reaction force.SOLUTION: There is provided a steer-by-wire steering reaction force device 1 comprising shaft force estimation means 15 which estimates shaft force of a steering actuator based upon a current value of the steering actuator for turning a turning wheel, and normative steering force setting means 16 which sets normative steering force based upon the shaft force that the shaft force estimation means 15 estimates. The steer-by-wire steering reaction force device 1 controls a current to be supplied to a steering reaction force actuator imparting reaction force torque to a steer-by-wire operator so that steering torque of the steer-by-wire operator reaches the normative steering force set by the normative steering force setting means 16.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steer-by-wire steering reaction force device. [Background technology]

[0002] Steer-by-wire steering devices have been known in the past in which the steered wheels are not mechanically connected to an operator (for example, a steering wheel or lever) operated by a driver. For example, as disclosed in Patent Document 1 below, a steer-by-wire system is known that sets a target steering reaction force (target steering reaction torque) based on a deviation signal corresponding to the deviation between a target steering angle and an actual steering angle, and feedback controls the current flowing through a reaction motor so that the actual steering torque detected based on the output value of a steering torque sensor matches the target steering reaction torque. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4908049 Summary of the Invention [Problem to be solved by the invention]

[0004] In the past, the reaction force corresponding to the deviation between the target steering angle and the actual steering angle differed for each vehicle, so a reaction force map or the like had to be set for each vehicle. This required a lot of development effort and left room for improvement.

[0005] An object of the present invention is to provide a steer-by-wire steering reaction force device that can easily set a target steering reaction force while minimizing the influence of vehicle characteristics. [Means for solving the problem]

[0006] (1) The present invention comprises an axial force estimation means for estimating the axial force of a steering actuator based on a current value of the steering actuator that steers steered wheels, and a standard steering force setting means for setting a standard steering force based on the axial force estimated by the axial force estimation means, and controls the current supplied to a steering reaction force actuator that imparts a reaction torque to the operator so that the steering torque of a steer-by-wire operator becomes the standard steering force set by the standard steering force setting means.

[0007] (2) In the present invention, in the above (1), the axial force estimation means may estimate friction of the steering actuator based on a motor speed of the steering actuator, and correct the axial force of the steering actuator based on the estimated friction.

[0008] (3) In the present invention described above in (2), the axial force estimation means may correct the axial force of the steering actuator based on a viscosity correction value determined based on a motor speed of the steering actuator.

[0009] (4) In the present invention, in the above (2) or (3), the axial force estimation means may correct the axial force of the steering actuator based on an inertia correction value determined based on a motor speed of the steering actuator.

[0010] (5) In the present invention, in any one of the above (1) to (4), the standard steering force setting means may calculate a friction correction value based on a motor angle of the steering reaction force actuator, and may correct the basic reaction force calculated based on the axial force estimated by the axial force estimation means based on the calculated friction correction value.

[0011] (6) In any one of the above (1) to (5), the present invention may be such that the standard steering force setting means determines a damping correction value based on the motor angular velocity of the steering reaction force actuator, and corrects the basic reaction force determined based on the axial force estimated by the axial force estimation means based on the determined damping correction value. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a steer-by-wire steering reaction force device that can easily set a target steering reaction force while minimizing the influence of vehicle characteristics. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an example of a steer-by-wire system to which a steering reaction force device for steer-by-wire according to an embodiment of the present invention is applied; [Figure 2] 1 is a schematic block diagram showing the configuration of a steer-by-wire steering reaction force device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a schematic block diagram showing the configuration of an axial force estimation means. [Figure 4] FIG. 4 is a schematic block diagram showing the configuration of a standard steering force setting means. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

[0015] 1 is a schematic diagram showing an example of a steer-by-wire system to which a steering reaction force device for steer-by-wire according to one embodiment of the present invention is applied. As shown in this figure, a steer-by-wire system 2 to which a steering reaction force device for steer-by-wire according to this embodiment is applied includes a steering wheel (operator) 3 operated by a driver, a steering angle sensor 4 that detects the steering angle of the steering wheel 3, a steering reaction force actuator 5 that applies a steering reaction force (reaction torque) to the steering wheel 3, a steering torque sensor 6 that detects the steering torque acting on the steering wheel 3, a rack shaft 10 connected to left and right wheels (steerable wheels) 7 via knuckle arms 8 and tie rods 9, a steering actuator 11 that drives the rack shaft 10 in the axial direction to steer the wheels 7, a vehicle speed sensor 12 that detects the vehicle speed, a steering angle sensor 13 that detects the steering angle of the wheels from the axial position of the rack shaft 10, and a control device (ECU) 14 that controls the steering reaction force actuator 5 and the steering actuator 11. A steer-by-wire steering reaction force device 1 of the present invention is applied to this steer-by-wire 2. Specifically, the ECU 14 has a steering device (not shown) that controls the steering actuator 11 based on detection signals from the steering angle sensor 4, the vehicle speed sensor 12, etc., and the steer-by-wire steering reaction force device 1 of the present invention that controls the steering reaction force actuator 5. In this embodiment, the steering reaction force actuator 5 and the steering actuator 11 are motors.

[0016] 2 is a schematic block diagram showing the configuration of a steer-by-wire steering reaction force device according to one embodiment of the present invention. The steer-by-wire steering reaction force device 1 includes an axial force estimation means 15 that estimates the axial force of the steering actuator 11 based on the current value of the steering actuator 11 that steers the wheels 7, and a normative steering force setting means 16 that sets a normative steering force based on the axial force estimated by the axial force estimation means 15.

[0017] Fig. 3 is a schematic block diagram showing the configuration of the axial force estimation means. The axial force estimation means 15 estimates the axial force based on the actual current value, which is the value of the current flowing through the steering actuator 11, and the motor speed of the steering actuator 11. That is, as shown in Fig. 3, the actual current value of the steering actuator 11 and the motor speed of the steering actuator 11 are input to the axial force estimation means 15.

[0018] The actual current value of the steering actuator 11 is input to the low-pass filter 17. The low-pass filter 17 removes high-frequency components. The actual current value from which the high-frequency components have been removed by the low-pass filter 17 is input to the conversion unit 18. The conversion unit 18 generates an axial force corresponding to the input actual current value. The axial force generated by the conversion unit 18 is input to the subtractor 19.

[0019] Furthermore, the axial force generated by the conversion unit 18 is input to a friction estimating unit 20. In addition to the axial force generated by the conversion unit 18, the motor speed of the steering actuator 11 is also input to this friction estimating unit 20. The friction estimating unit 20 estimates the friction of the steering actuator 11 based on the axial force generated by the conversion unit 18 and the motor speed of the steering actuator 11. The friction estimated by the friction estimating unit 20 is input to a friction correcting unit 21. The friction correcting unit 21 calculates a friction correction value by multiplying the friction estimated by the friction estimating unit 20 by a friction correction gain. The friction correction value calculated by the friction correcting unit 21 is input to an adder 22.

[0020] On the other hand, the motor speed of the steering actuator 11 is input not only to the friction estimator 20 described above but also to a low-pass filter 23. The low-pass filter 23 removes high-frequency components. The motor speed from which the high-frequency components have been removed by the low-pass filter 23 is input to a viscosity corrector 24. The viscosity corrector 24 calculates a viscosity correction value by multiplying the motor speed from which the high-frequency components have been removed by the low-pass filter 23 by a viscosity correction gain. The viscosity correction value calculated by the viscosity corrector 24 is input to an adder 25.

[0021] The motor speed of the steering actuator 11 is input not only to the friction estimator 20 and low-pass filter 23 described above, but also to a differentiator 26. The differentiator 26 calculates the motor acceleration by differentiating the motor speed of the steering actuator 11. The motor acceleration calculated by the differentiator 26 is input to a low-pass filter 27. The low-pass filter 27 removes high-frequency components. The motor acceleration from which the high-frequency components have been removed by the low-pass filter 27 is input to an inertia correction unit 28. The inertia correction unit 28 calculates an inertia correction value by multiplying the motor acceleration from which the high-frequency components have been removed by the low-pass filter 27 by an inertia correction gain. The inertia correction value calculated by the inertia correction unit 28 is input to an adder 25.

[0022] As described above, the adder 25 receives as input the viscosity correction value from the viscosity correction unit 24 and the inertia correction value from the inertia correction unit 28. The adder 25 adds the viscosity correction value and the inertia correction value together to generate a first sum. The first sum from the adder 25 is input to the adder 22. As described above, the adder 22 receives as input the friction correction value from the friction correction unit 21. The adder 22 adds the first sum and the friction correction value together to generate a second sum. The second sum from the adder 22 is input to the subtractor 19. As described above, the subtractor 19 receives as input the axial force generated by the conversion unit 18. The subtractor 19 subtracts the second sum from the axial force generated by the conversion unit 18 to generate an estimated axial force of the steering actuator 11. In this way, the axial force estimation means 15 estimates the axial force of the steering actuator 11.

[0023] The axial force estimating means 15 subtracts a second addendum including the friction estimated by the friction estimating unit 20 from the axial force generated by the converting unit 18. Therefore, the axial force estimating means 15 can estimate the friction of the steering actuator 11 based on the motor speed of the steering actuator 11, and correct the axial force of the steering actuator 11 based on the estimated friction. Furthermore, the axial force estimating means 15 subtracts a second addendum including a viscosity correction value from the axial force generated by the converting unit 18. Therefore, the axial force estimating means 15 can correct the axial force of the steering actuator 11 based on the viscosity correction value calculated based on the motor speed of the steering actuator 11. Furthermore, the axial force estimating means 15 subtracts a second addendum including an inertia correction value from the axial force generated by the converting unit 18. Therefore, the axial force estimating means 15 can correct the axial force of the steering actuator 11 based on the inertia correction value calculated based on the motor speed of the steering actuator 11.

[0024] Fig. 4 is a schematic block diagram showing the configuration of the normative steering force setting means. The normative steering force setting means 16 sets the normative steering force based on the axial force estimated by the axial force estimating means 15, the motor angular velocity of the steering reaction force actuator 5, and the motor angle of the steering reaction force actuator 5. That is, as shown in Figs. 2 and 4, the normative steering force setting means 16 receives the axial force estimated by the axial force estimating means 15, the motor angular velocity of the steering reaction force actuator 5, and the motor angle of the steering reaction force actuator 5. In this embodiment, the normative steering force setting means 16 has a reference characteristic unit 29, a steering angular velocity element unit 30, a steering angle element unit 31, and an adder 32.

[0025] The estimated axial force estimated by the axial force estimation means 15 is input to the reference characteristics section 29. The reference characteristics section 29 generates a reference weight corresponding to the input estimated axial force by referring to a map 33 in which the horizontal axis represents the estimated axial force and the vertical axis represents the reference weight. The reference weight generated by the reference characteristics section 29 is input to an adder 32.

[0026] The motor angular velocity of the steering reaction force actuator 5 is input to the steering angular velocity element unit 30. The steering angular velocity element unit 30 has a map 34 in which the horizontal axis represents the motor angular velocity and the vertical axis represents the damping correction value. The steering angular velocity element unit 30 converts the input motor angular velocity into a damping correction value. The damping correction value from the steering angular velocity element unit 30 is input to an adder 32.

[0027] The motor angle of the steering reaction force actuator 5 is input to the steering angle element unit 31. The steering angle element unit 31 has a map 35 in which the horizontal axis represents the motor angle and the vertical axis represents the friction correction value. The steering angle element unit 31 converts the input motor angle into a friction correction value. The friction correction value from the steering angle element unit 31 is input to an adder 32.

[0028] The adder 32 adds the reference weight, damping correction value, and friction correction value. The result of the addition in the adder 32 becomes a reference steering force characteristic 36. In this way, the reference steering force setting means 16 generates the reference weight, damping correction value, and friction correction value in the reference characteristic section 29, the steering angle velocity element section 30, and the steering angle element section 31, respectively, and sets the reference steering force by adding the generated reference weight, damping correction value, and friction correction value.

[0029] The normative steering force setting means 16 adds a damping correction value to the reference weight. Therefore, the normative steering force setting means 16 determines a damping correction value based on the motor angular velocity of the steering reaction force actuator 5, and can correct the basic reaction force determined based on the axial force estimated by the axial force estimation means 15 based on the determined damping correction value. Furthermore, the normative steering force setting means 16 adds a friction correction value to the reference weight. Therefore, the normative steering force setting means 16 determines a friction correction value based on the motor angle of the steering reaction force actuator 5, and can correct the basic reaction force determined based on the axial force estimated by the axial force estimation means 15 based on the determined friction correction value.

[0030] As shown in FIG. 2, the standard steering force from standard steering force setting means 16 is input to subtractor 37. Steering torque detected by steering torque sensor 6 is input to subtractor 37. Subtractor 37 subtracts the steering torque detected by steering torque sensor 6 from the standard steering force (standard steering torque) set by standard steering force setting means 16. The result of subtraction in subtractor 37 is input to LQR control unit 38. LQR control unit 38 performs LQR control on the result of subtraction in subtractor 37 to generate a command current value, which is the value of a current to be passed to steering reaction force actuator 5. Then, steer-by-wire steering reaction force device 1 performs feedback control so that the current value input to steering reaction force actuator 5 becomes the command current value. In this way, the steer-by-wire steering reaction force device 1 controls the current supplied to the steering reaction force actuator 5 that applies a reaction torque to the steering wheel 3 so that the steering torque of the steering wheel 3 of the steer-by-wire 2 becomes the standard steering force set by the standard steering force setting means 16.

[0031] In the case of the steer-by-wire steering reaction force device 1 of this embodiment, the current flowing through the steering reaction force actuator 5 is feedback controlled as described above. Therefore, the output of the steering actuator 11 and the reaction force that the wheels 7 receive from the road surface are approximately equal, so by setting the target steering reaction force of the steering reaction force actuator 5 based on the standard steering force from the current value of the steering actuator 11, it is possible to easily set the target steering reaction force while minimizing the influence of vehicle characteristics. Furthermore, in the case of the steer-by-wire steering reaction force device 11 of this embodiment, the axial force of the steering actuator 11 is corrected by the friction estimated from the motor speed of the steering actuator 11. Therefore, it is possible to correct any deviation from the actual rack axial force caused by friction when the steering wheel 3 starts to turn or when turning back.

[0032] Furthermore, in the case of the steer-by-wire steering reaction force device 1 of this embodiment, the axial force of the steering actuator 11 is corrected by a viscosity correction value and an inertia correction value obtained from the motor speed of the steering actuator 11. Therefore, by performing viscosity correction (at the start of steering) and inertia correction (at the change of direction) from the motor speed, the deviation described above can be further suppressed. Furthermore, in the case of the steer-by-wire steering reaction force device 1 of this embodiment, the basic reaction force obtained from the axial force estimated by the axial force estimating means 15 is corrected by a friction correction value obtained from the steering wheel angle, which is the motor angle of the steering reaction force actuator 5. Therefore, by correcting the reference weight based on the estimated axial force by the steering wheel angle, it is possible to set a steering force appropriate for the vehicle driver. Furthermore, in the case of the steer-by-wire steering reaction force device 1 of this embodiment, the basic reaction force obtained from the axial force estimated by the axial force estimating means 15 is corrected by a damping correction value obtained from the steering wheel angular velocity, which is the motor angular velocity of the steering reaction force actuator 5. Therefore, by correcting the reference weight based on the estimated axial force using the steering wheel angular velocity, it is possible to set a target steering reaction force that corresponds not only to the steering wheel angle but also to the steering wheel angular velocity, thereby enabling a steering force that is more appropriate for the driver to be set.

[0033] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention.

[0034] For example, in the above embodiment, the axial force is corrected using the viscosity correction value and the inertia correction value, but the axial force may be corrected using either the viscosity correction value or the inertia correction value. [Explanation of symbols]

[0035] 1 Steer-by-wire steering reaction device 2 Steer-by-wire 3 Steering wheel (operator) 5 Steering reaction actuator 7 Wheels (steering wheels) 11 Steering actuator 15 Axial force estimation means 16 Standard steering force setting means

Claims

1. an axial force estimation means for estimating an axial force of a steering actuator based on a current value of the steering actuator that steers the steered wheels; a standard steering force setting means for setting a standard steering force based on the axial force estimated by the axial force estimation means, the axial force estimation means estimates the friction of the steering actuator using a friction estimation unit that receives the axial force generated by a conversion unit that receives the current value of the steering actuator and the motor speed of the steering actuator, and corrects the axial force of the steering actuator based on the estimated friction; A steer-by-wire steering reaction force device that controls a current supplied to a steering reaction force actuator that applies a reaction torque to an operator so that the steering torque of the operator becomes the standard steering force set by the standard steering force setting means.

2. 2. The steer-by-wire steering reaction force device according to claim 1, wherein the axial force estimating means corrects the axial force of the steering actuator based on a viscosity correction value determined based on a motor speed of the steering actuator.

3. 3. The steer-by-wire steering reaction force device according to claim 1, wherein the axial force estimation means corrects the axial force of the steering actuator based on an inertia correction value determined based on a motor speed of the steering actuator.

4. 3. The steer-by-wire steering reaction force device according to claim 1, wherein the reference steering force setting means determines a friction correction value based on a motor angle of the steering reaction force actuator, and corrects the basic reaction force determined based on the axial force estimated by the axial force estimating means, based on the determined friction correction value.

5. 3. The steer-by-wire steering reaction force device according to claim 1, wherein the reference steering force setting means determines a damping correction value based on a motor angular velocity of the steering reaction force actuator, and corrects the basic reaction force determined based on the axial force estimated by the axial force estimating means, based on the determined damping correction value.

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