Steering system

Abstract

In a steering system that steers the steering wheels by controlling the steering actuator based on the amount of operation of the steering control member estimated by the operation amount estimation unit, the objective is to steer the steering wheels properly even if the operation amount estimation system, including the operation amount estimation unit, is malfunctioning. [Solution] In this steering system, the steering actuator is controlled based on the estimated operating amount, which is the operating amount of the steering operating member estimated by the operating amount estimation unit. However, if the operating amount estimation system, including the operating amount estimation unit, is abnormal, the steering actuator is controlled based on the sensor operating amount, which is the value detected by the operating amount sensor. As a result, even if the operating amount estimation system is abnormal, the steering wheels can be steered smoothly.

Description

Technical Field

[0001] The present invention relates to a so-called steer-by-wire type steering system.

Background Art

[0002] Patent Document 1 describes an automatic avoidance device equipped with a steer-by-wire type steering system. In the automatic avoidance device described in Patent Document 1, when steering becomes impossible due to an abnormality in the steering system, the driving route is changed by controlling the braking force on the left and right of the steered wheels, and the vehicle is driven to a safe place.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present invention is to steer a pair of wheels well in a steering system that controls at least one steering actuator based on the operation amount of a steering operation member estimated by an operation amount estimation unit, even if the operation amount estimation system including the operation amount estimation unit is abnormal.

Means for Solving the Problems

[0005] In the steering system according to the present disclosure, at least one steering actuator is controlled based on an estimated operation amount that is the operation amount of a steering operation member estimated by an operation amount estimation unit. However, when the operation amount estimation system including the operation amount estimation unit is abnormal, at least one steering actuator is controlled based on a sensor operation amount that is a detected value of an operation amount sensor. As a result, even if the operation amount estimation system is abnormal, a pair of wheels can be steered well.

Brief Description of the Drawings

[0006] [Figure 1] This diagram conceptually shows the main components of a steering system according to one embodiment of the present invention. [Figure 2] This is a perspective view conceptually illustrating the entire steering system described above. [Figure 3] This is a flowchart showing the reaction force control and other programs stored in the control unit on the steering side of the steering system described above. [Figure 4] This is a flowchart showing the steering control program stored in the steering control unit of the steering system described above. [Figure 5] This is a flowchart showing the abnormal steering control program stored in the steering control unit of the steering system described above. [Figure 6] This flowchart represents a different abnormal steering control program from the one described above. [Figure 7] This flowchart represents yet another abnormal steering control program, distinct from the abnormal steering control program described above. [Figure 8] This is a flowchart showing the switching control program stored in the steering control unit mentioned above. [Figure 9] This flowchart represents a different switching control program than the one described above. [Figure 10] This figure shows the change in steering torque of the steering motor when the switching control program, represented by the flowchart in Figure 8, is executed. [Figure 11] This figure shows the change in steering torque of the steering motor when the switching control program, represented by the flowchart in Figure 9, is executed. [Modes for carrying out the invention]

[0007] The steering system according to one embodiment of the present invention will be described in detail below with reference to the drawings. [Examples]

[0008] As shown in Figures 1 and 2, the steering system steers a pair of steering wheels 10. The pair of wheels 10 includes a left wheel 10 and a right wheel 10 (hereinafter, these may be referred to collectively, or each may be referred to as wheel 10). The steering system includes an operating device 12, a steering device 14, etc. The operating device 12 and the steering device 14 are mechanically isolated. The steering system is a so-called steer-by-wire type. In this embodiment, the steering system is redundant, and control is performed in two separate systems.

[0009] The operating device 12 includes a steering operating member 20, a steering shaft 22, a steering column 24, a reaction force actuator 25, a reaction force transmission mechanism 28, an operating side control unit 30, etc. The steering operating member 20 is operable by the driver. In this embodiment, the steering operating member 20 is of the rotatable type and can be, for example, a steering wheel. The steering operating member 20 can be of the linear movement type. The steering operating member 20 is attached to one end of the steering shaft 22 so as to be integrally rotatable around the axis of the steering shaft 22. The reaction force actuator 25 is provided at the other end of the steering shaft 22 via the reaction force transmission mechanism 28.

[0010] The steering column 24 rotatably holds the steering shaft 22 while being supported by the vehicle body. The reaction force actuator 25 may include a reaction force motor 26, or it may include the reaction force motor 26 and a reduction gear. The reaction force transmission mechanism 28 includes a plurality of gears, etc. The reaction force torque generated by the reaction force actuator 25 is applied to the steering operating member 20 via the reaction force transmission mechanism 28 and the steering shaft 22. The steering operating member 20 is subjected to an operating reaction force as a reaction force torque.

[0011] In this embodiment, the operating device 12 comprises a steering shaft 22, a steering column 24, a reaction force transmission mechanism 28, a reaction force actuator 25, and the like to form a reaction force application mechanism 31.

[0012] The reaction motor 26 is a three-phase brushless DC motor and includes a rotor, which is a rotating shaft, and a stator, which is a coil. The rotating shaft includes a magnet, and the coil includes two sets of coils that are separable from each other. In the reaction motor 26, two sets of coils are provided for one rotating shaft. In the reaction motor 26, each of the two sets of coils can be referred to as reaction motor 26a and reaction motor 26b, respectively. Reaction motors 26a and 26b are each provided with motor rotation angle sensors 32a and 32b, etc., which detect the rotation angle Θm of the reaction motors 26a and 26b, respectively. Hereinafter, when there is no need to distinguish between reaction motors 26a, 26b, etc., or when referring to them collectively, they may simply be referred to as reaction motor 26, etc.

[0013] The operating device 12 includes a torque sensor 34, an operating amount sensor 36, etc. The operating amount sensor 36 detects the amount of operation of the steering operating member 20. If the steering operating member 20 is of the rotational type, the amount of operation can be expressed as the rotation angle of the steering operating member 20 around the axis. More specifically, when the position of the steering operating member 20 in the straight-ahead state of the vehicle is taken as the neutral position, the amount of operation can be expressed as the rotation angle of the steering operating member 20 in the left and right directions from the neutral position.

[0014] The torque sensor 34 detects the operating torque applied by the driver to the steering operating member 20. The torque sensor 34 incorporates a torsion bar into the steering shaft 22, and the operating torque is detected based on the amount of twist of the torsion bar. In this embodiment, two torque sensors 34 (torque sensors 34a and 34b) are provided.

[0015] The control unit 30 is primarily computer-based and controls the reaction force applied to the steering control member 20 by controlling the reaction force motor 26, and also estimates the amount of operation of the steering control member 20 based on the operating state of the reaction force motor 26. The amount of operation of the steering control member 20 is used in steering control, as will be described later. The control unit 30 can be called a reaction force control unit because it controls the reaction force (hereinafter sometimes simply referred to as reaction force).

[0016] The operation - side control unit 30 includes reaction - force MCUs (Micro Controller Unit or Motor Controller Unit) 60a, 60b, etc., provided respectively corresponding to the reaction - force motors 26a, 26b. The reaction - force MCUs 60a, 60b each include an execution unit, a storage unit, an input / output unit, etc. To the input / output units of each of the reaction - force MCUs 60a, 60b, the reaction - force motors 26a, 26b are connected via drive circuits (not shown), and motor rotation angle sensors 32a, 32b, torque sensors 34a, 34b, etc. are connected. Also, the reaction - force MCU 60a and the reaction - force MCU 60b are communicably connected to each other via a communication line 61.

[0017] The steering device 14 has a structure in which a pair of wheels 10 are steered by one steering actuator 42 which is at least one steering actuator. The steering device 14 includes a steering rod 40, tie rods 41, a steering actuator 42, a steering force transmission mechanism 44, a steering control unit 45, etc. As shown in FIG. 2, the steering rod 40 is held in a housing provided on the vehicle body so as to be movable in the left - right direction, and is connected to the wheels 10 via the tie rods 41 respectively. The steering actuator 42 can include a steering motor 50, or can include a steering motor 50 and a speed reducer (not shown), etc.

[0018] The steering force transmission mechanism 44 has a function as a motion conversion mechanism, and converts the rotation of the steering actuator 42 into a linear movement in the left - right direction and transmits it to the steering rod 40. In the present embodiment, the steering force transmission mechanism 44 is a screw mechanism, and includes, for example, a screw portion 46, a nut member (not shown), pulleys, and belts. The screw portion 46 is provided on the steering rod 40. The nut member is screwed onto the screw portion 46. The rotation of the steering actuator 42 is transmitted to the nut member by transmission members such as pulleys and belts.

[0019] In the present embodiment, in the steering device 14, a steering mechanism 51 is constituted by the steering rod 40, tie rods 41, steering actuator 42, steering force transmission mechanism 44, etc.

[0020] The steering motor 50, like the reaction motor 26, is a three-phase brushless DC motor and includes two sets of coils that are separable from each other. Each of these two sets of coils is referred to as steering motor 50a and steering motor 50b, respectively. Steering motors 50a and 50b are equipped with motor rotation angle sensors 52a and 52b, respectively, for detecting the rotation angle of the electric motor. In addition, current sensors 54a and 54b are provided in the drive circuit (inverter), respectively, for detecting the current flowing through steering motors 50a and 50b. Hereinafter, when there is no need to distinguish between steering motors 50a, 50b, etc., or when referring to them collectively, they may simply be referred to as steering motor 50, etc.

[0021] The steering device 14 also includes a steering angle sensor 56. The steering angle sensor 56 detects the amount of movement of the steering rod 40 in the left and right directions from the neutral position (the position where the vehicle is located when moving straight) to detect the steering angle θ as the amount of steering of the wheel 10.

[0022] The steering control unit 45 is computer-based and controls the steering angle of the wheels by controlling the steering motors 50. The steering control unit 45 includes steering MCUs 62a and 62b, etc. The steering MCUs 62a and 62b are provided corresponding to the steering motors 50a and 50b, respectively. Each of the steering MCUs 62a and 62b includes an execution unit, a storage unit, an input / output unit, etc. The steering motors 50a and 50b are connected to the input / output unit of each of the steering MCUs 62a and 62b via a drive circuit (not shown), and motor rotation angle sensors 52a and 52b, current sensors 54a and 54b, etc. are also connected to the input / output unit of each of the steering MCUs 62a and 62b, respectively. Furthermore, the steering MCUs 62a and 62b are connected to each other so as to be able to communicate with each other via a communication line 63.

[0023] Furthermore, the reaction force MCU 60a and the steering MCU 62a are connected via a dedicated communication line, L-CAN (Local Car Area Network or Local Controller Area Network) 68, enabling communication. The reaction force MCU 60b and the steering MCU 62b are connected via a dedicated communication line, L-CAN 70, enabling communication. In addition, the reaction force MCUs 60a and 60b, and the steering MCUs 62a and 62b are each connected to the control amount sensor 36, etc., via a G-CAN (Global Controller Area network) 66.

[0024] In this embodiment, reaction motor 26a corresponds to the first reaction motor, and reaction motor 26b corresponds to the second reaction motor. Reaction MCU 60a corresponds to the first reaction control unit, and reaction MCU 60b corresponds to the second reaction control unit. Furthermore, steering motor 50a corresponds to the first steering motor, and steering motor 50b corresponds to the second steering motor. Steering MCU 62a corresponds to the first steering control unit, and steering MCU 62b corresponds to the second steering control unit.

[0025] Furthermore, the first reaction force control unit may be referred to as the main reaction force MCU 60a, and the second reaction force control unit as the sub-reaction force MCU 60b. The first steering control unit may be referred to as the main steering control unit MCU 62a, and the second steering control unit as the sub-steering control unit MCU 62b. The terms "main" and "sub" are merely for convenience, and it is also possible to refer to the first reaction force control unit as the sub-reaction force MCU, the first steering control unit as the sub-steering control unit, the second reaction force control unit as the main reaction force MCU, and the second steering control unit as the main steering control unit MCU.

[0026] The operation of the steering system configured as described above will now be explained.

[0027] In the control unit 30, the reaction force MCUs 60a and 60b each control the reaction force motors 26a and 26b respectively so that a target operating reaction force F* is applied to the steering control member 20, and estimate the amount of operation of the steering control member 20 based on the motor rotation angles Θma and Θmb of the reaction force motors 26a and 26b.

[0028] The target operating reaction force F* is obtained according to the following equation, based on the steering load-dependent component Ft and the assist force-dependent component Fs. The target operating reaction force F* is set to a magnitude that makes the driver feel as if they are manually steering a vehicle equipped with a steering system that includes a power steering mechanism. F* = Ft - Fs

[0029] The steering load-dependent component Ft can be set to a magnitude that allows the driver to perceive the steering state (road surface condition) of the wheel 10. When the wheel 10 is steered, a larger load applied to the wheel 10 results in a larger torque output by the steering motor 50 than a smaller load. Therefore, the steering load-dependent component Ft can be set to a magnitude determined based on the steering torque, which is the torque output by the steering motor 50. Furthermore, the steering torque output by the steering motor 50 is obtained based on the current I supplied to the steering motor 50. Therefore, the steering load-dependent component Ft can be set to a magnitude corresponding to the supplied current I.

[0030] The operating force assist-dependent component Fs can be considered a component that provides the driver with a sense of operation in a so-called power steering system. In a power steering system, an assist torque is generally applied in accordance with the operating torque. Therefore, the operating force assist-dependent component Fs can be set to a magnitude determined based on the operating torque detected by the torque sensors 34a and 34b.

[0031] As described above, by determining the target operating reaction force F* to be the magnitude obtained by subtracting the operating force assist component Fs from the steering load-dependent component Ft, the driver can perceive the road surface conditions while obtaining a steering feel as if they were performing manual operation.

[0032] Furthermore, the amount of operation of the steering control member 20 is estimated based on the rotation angles Θa and Θb of the reaction motors 26a and 26b. In the operating device 12, the reaction motor 26 is connected to the steering shaft 22 via a reaction force transmission mechanism 28. Therefore, a predetermined one-to-one relationship exists between the rotation angle Θ of the reaction motor 26 and the amount of operation of the steering control member 20. Based on this relationship and the rotation angles Θa and Θb of the reaction motors 26a and 26b detected by the motor rotation angle sensors 32a and 32b, the amounts of operation δa and δb of the steering control member 20 can be estimated. In this embodiment, the neutral positions of the reaction motors 26a and 26b are set before the vehicle is shipped. By accumulating the detected values ​​from the motor rotation angle sensors 32a and 32b for each of the reaction motors 26a and 26b, the rotation angles Θa and Θb of the reaction motors 26a and 26b are obtained from the neutral position, and the operating amounts δa and δb of the steering operating member 20 are estimated.

[0033] In the reaction force main MCU60a and the reaction force sub-MCU60b, the reaction force control program, represented by the flowchart in Figure 3A, and the manipulated variable estimation program, represented by the flowchart in Figure 3B, are executed independently. The following describes the case in which the reaction force control program and the manipulated variable estimation program are executed in the reaction force main MCU60a.

[0034] The reaction force control program is executed at predetermined set intervals. The current Ia flowing through the steering motor 50a is supplied from the steering main MCU 62a to the reaction force main MCU 60a via a dedicated communication line 68. The current Ib flowing through the steering motor 50b is supplied from the steering sub MCU 62b to the reaction force sub MCU 60b via a dedicated communication line 70.

[0035] In step 1 (hereinafter, step 1 will be abbreviated as S1; the same applies to the other steps), the current Ia flowing through the steering motor 50a supplied from the steering main MCU 62a is obtained, and the steering load dependent component Ft is obtained. In S2, the operating force assist force dependent component Fs is obtained based on the operating torque detected by the torque sensor 34a. In S3, the target operating reaction force F* is obtained, and in S4, the current Ia supplied to the reaction force motor 26a is controlled so that the target operating reaction force F* is obtained.

[0036] The manipulated variable estimation program is also executed at predetermined set intervals. In S6, the detected value of the motor rotation angle sensor 32a is acquired, and in S7, the rotation angle Θa of the reaction force motor 26a from the neutral position is acquired, and the operating amount δa of the steering operating member 20 is estimated. In S8, the main estimated operating amount δa, which is the operating amount of the steering operating member 20 estimated by the reaction force main MCU 60a, is supplied to the steering main MCU 62a via a dedicated communication line 68. The same applies to the reaction force sub MCU 60b, and the sub estimated operating amount δb, which is the operating amount of the steering operating member 20 estimated by the reaction force sub MCU 60b, is supplied to the steering sub MCU 62b via a dedicated communication line 70.

[0037] In the steering control unit 45, the steering main MCU 62a and the steering sub MCU 62b each control the steering motors 50a and 50b, respectively, so that the wheels 10 steer by target steering angles θ*a and θ*b, which are determined based on the operating amounts δa and δb of the steering operating member 20.

[0038] The target steering angle θ* can be obtained by multiplying the operating amounts δa and δb of the steering control member 20 by a gain. For example, the gain can be a value corresponding to the steering gear ratio determined by the vehicle speed.

[0039] Based on the target steering angles θ*a and θ*b, the target motor rotation angles θm*a and θm*b, which are the rotation angles of the steering motors 50a and 50b, are obtained. In the steering device 14, the rotation of the steering motor 50 is converted into the movement of the steering rod 40 via the steering force transmission mechanism 44, and the wheels 10 are steered. Therefore, a predetermined one-to-one relationship is established between the rotation angle of the steering motor 50 and the steering angle of the wheels 10. In addition, motor rotation angle deviations Δθma and Δθmb are obtained, which are the deviations between the target motor rotation angles θm*a and θm*b and the actual motor rotation angles θmsa and θmsb, which are the actual rotation angles of the steering motors 50a and 50b obtained based on the detected values ​​of the motor rotation angle sensors 52a and 52b.

[0040] Then, based on the motor rotation angle deviations Δθma and Δθmb, target steering torques T*a and T*b, which are the torques required for the steering motors 50a and 50b, are obtained. Based on the target steering torques T*a and T*b, target currents I*a and I*b supplied to the steering motors 50a and 50b are determined. Then, the drive circuit (inverter), etc., is controlled so that the currents Isa and Isb detected by the current sensors 54a and 54b approach the target currents I*a and I*b.

[0041] In both the steering main MCU62a and the steering sub-MCU62b, the steering control program shown in the flowchart of Figure 4 is executed at predetermined set time intervals. The steering main MCU62a and the steering sub-MCU62b independently acquire target steering angles θ*a and θ*b based on the main estimated control variable δa and sub estimated control variable δb, respectively, and control the steering motors 50a and 50b. In most cases, the steering main MCU62a and the steering sub-MCU62b are expected to perform similar control. The following describes the case where the steering control program in Figure 4 is executed in the steering main MCU62a.

[0042] In S11, the main estimated manipulated variable δa supplied from the reaction force main MCU 60a is acquired. In S12, the target steering angle θ*a is determined based on the main estimated manipulated variable δa. In S13, the target motor rotation angle θm*a for the steering motor 50a is acquired, as well as the actual motor rotation angle θmsa. The motor rotation angle deviation Δθma is then acquired. In S14, the target steering torque T*a is acquired to bring the actual motor rotation angle θmsa closer to the target motor rotation angle θm*a, and the target current I*a to the steering motor 50a is acquired so that the target steering torque T*a is obtained. In S15, the drive circuit is controlled so that the current Isa detected by the current sensor 54a approaches the target current I*a.

[0043] However, due to an anomaly, the main estimated control input δa and sub estimated control input δb may not be supplied from the reaction force main MCU60a and reaction force sub MCU60b to the steering main MCU62a and steering sub MCU62b. In addition, the supplied main estimated control input δa and sub estimated control input δb may be of an abnormal magnitude. In these cases, it becomes difficult for the steering main MCU62a and steering sub MCU62b to control the steering motors 50a and 50b.

[0044] In this embodiment, abnormalities include, for example, abnormalities in the motor rotation angle sensors 32a and 32b, failure of the reaction force main MCU 60a and reaction force sub-MCU 60b, communication abnormalities in the dedicated communication lines (L-CAN) 68 and 70, disconnections of the dedicated communication lines 68 and 70, and abnormalities in the reaction force motors 26a and 26b. These abnormalities are abnormalities in elements related to the estimation of the operating amount δ of the steering operating member 20 (including elements used to estimate the operating amount δ), and can therefore be referred to as abnormalities in the operating amount estimation system. The operating amount estimation system includes the operating amount estimation main system 80a and the operating amount estimation sub-system 80b. The operating amount estimation main system 80a and the operating amount estimation sub-system 80b can also be referred to as the reaction force main system 80a and the reaction force sub-system 80b.

[0045] The presence or absence of abnormalities in the main reaction force system 80a and the sub-reaction force system 80b may be acquired by the main reaction force MCU 60a and sub-reaction force MCU 60b and supplied to the steering main MCU 62a and sub-reaction force MCU 62b, or acquired by the steering main MCU 62a and sub-reaction force MCU 62b, respectively. For example, abnormalities in the motor rotation angle sensors 32a and 32b can be acquired by the main reaction force MCU 60a and sub-reaction force MCU 60b themselves. In addition, failure of the main reaction force MCU 60a and sub-reaction force MCU 60b, communication abnormalities or disconnections of the dedicated communication lines 68 and 70, etc., can be acquired by the steering main MCU 62a and sub-reaction force MCU 62b, respectively.

[0046] In any case, the reaction force MCUs 60a and 60b, and the steering MCUs 62a and 62b are connected to each other via dedicated communication lines 68 and 70, communication lines 61 and 63, etc., enabling them to communicate with one another. Therefore, the presence or absence of abnormalities in the main reaction force system 80a and the sub-reaction force system 80b can be checked in any of the reaction force MCUs 60a and 60b, or the steering MCUs 62a and 62b. Alternatively, the check can be performed in each of the steering MCUs 62a and 62b.

[0047] An example of an abnormality control program in this case is shown in the flowchart of Figure 5. In this embodiment, if the reaction force main system 80a is not abnormal (normal), the steering main MCU 62a controls the steering motor 50a based on the main estimated control amount δa. If the reaction force sub system 80b is normal, the steering sub MCU 62b controls the steering motor 50b based on the sub estimated control amount δb. On the other hand, if an abnormality is detected in the reaction force main system 80a, the steering main MCU 62a obtains the sensor control amount δs, which is the control amount detected by the control amount sensor 36, via G-CAN 66, and controls the steering motor 50a based on the sensor control amount δs. If an abnormality is detected in the reaction force sub system 80b, the steering sub MCU 62b controls the steering motor 50b based on the sensor control amount δs obtained via G-CAN 66.

[0048] The abnormal control program, represented by the flowchart in Figure 5, is executed at predetermined time intervals in both the steering main MCU62a and the steering sub-MCU62b. In this embodiment, the execution in the steering main MCU62a will be described, and the explanation of the execution in the steering sub-MCU62b will be omitted.

[0049] In S21, it is determined whether or not the reaction force main system 80a is abnormal. In S21, information may also be supplied from the reaction force main MCU 60a indicating that the motor rotation angle sensor 32a is abnormal. If the determination in S21 is NO, in S22, the steering main MCU 62a controls the steering motor 50a based on the main estimated control amount δa. If the determination in S21 is YES, in S23, the steering main MCU 62a controls the steering motor 50a based on the sensor control amount δs.

[0050] Furthermore, abnormal situation control can also be performed according to the abnormal situation control program shown in the flowchart of Figure 6. In this embodiment, if one of the reaction force main system 80a and the reaction force sub-system 80b is normal and the other is abnormal, the steering MCU 62 corresponding to the normal system will stop the steering motor 50. If both the reaction force main system 80a and the reaction force sub-system 80b are abnormal, both the steering main MCU 62a and the steering sub-MCU 62b will control the steering motors 50a and 50b, respectively, based on the sensor operation amount δs.

[0051] When driving on public roads, if the steering motor 50a is controlled by the steering main MCU 62a based on the main estimated control amount δa, the target steering angle θ* can usually be achieved even if the steering motor 50b is stopped. Furthermore, in the event of an abnormality, it is desirable from the standpoint of vehicle driving safety for the steering force to be somewhat insufficient, resulting in an understeer tendency. This is because it is undesirable for the steering force to increase against the driver's intentions in the event of an abnormality, causing the wheels 10 to steer against the driver's intentions and resulting in an oversteer tendency. Therefore, in this embodiment, if either the reaction force main system 80a or the reaction force sub-system 80b is abnormal, the steering motor 50a or steering motor 50b corresponding to that one can be stopped.

[0052] The abnormality control program, as shown in the flowchart of Figure 6, is executed similarly in both the steering main MCU 62a and the steering sub-MCU 62. Information regarding the presence or absence of abnormalities in the reaction force sub-system 80b is supplied from the steering sub-MCU 62b to the steering main MCU 62a via communication line 63, and information regarding the presence or absence of abnormalities in the reaction force main system 80a is supplied from the steering main MCU 62a to the steering sub-MCU 62b.

[0053] In S31, it is determined whether the main reaction system 80a is abnormal. If it is abnormal, in S32, it is determined whether the sub-reaction system 80b is abnormal. Conversely, if the main reaction system 80a is normal, in S33, it is determined whether the sub-reaction system 80b is abnormal.

[0054] If both the main reaction force system 80a and the sub-reaction force system 80b are abnormal, the determination in S32 becomes YES, and in S34, the steering motor 50a is controlled by the steering main MCU 62a based on the sensor operation amount δs, and the steering motor 50b is also controlled by the steering sub-MCU 62b based on the sensor operation amount δs.

[0055] If the reaction force main system 80a is abnormal but the reaction force sub-system 80b is normal, in S35, the steering main MCU 62a stops the steering motor 50a. If the reaction force main system 80a is normal, regardless of whether the reaction force sub-system 80b is normal or abnormal, in S36 and 37, the steering motor 50a is controlled based on the main estimated control amount δa supplied from the reaction force main MCU 60a.

[0056] Conversely, if the reaction force sub-system 80b is abnormal and the reaction force main system 80a is normal, the steering sub-MCU 62b stops the steering motor 50b (S37). If the reaction force sub-system 80b is normal, the steering sub-MCU 62b controls the steering motor 50b based on the sub-estimated control amount δb, regardless of whether the reaction force main system 80a is normal or abnormal (S35,36).

[0057] Anomaly control can also be performed according to the anomaly control program shown in the flowchart of Figure 7. In the flowchart of Figure 7, steps that are performed similarly in the anomaly control program shown in the flowchart of Figure 7 and the anomaly control program shown in the flowchart of Figure 6 are given the same step numbers and their explanations are omitted. The sub-estimated manipulated variable δb is supplied from the steering sub-MCU 62b to the steering main MCU 62a via the communication line 63, and the main estimated manipulated variable δa is supplied from the steering main MCU 62a to the steering sub-MCU 62b via the communication line 63.

[0058] If the reaction force main system 80a is abnormal and the reaction force sub-system 80b is normal, in S35x, both the steering main MCU 62a and the steering sub-MCU 62b control the steering motors 50a and 50b based on the sub-estimated control amount δb. If the reaction force main system 80a is normal and the reaction force sub-system 80b is abnormal, in S37x, both the steering sub-MCU 62b and the steering main MCU 62a control the steering motors 50a and 50b based on the main estimated control amount δa.

[0059] Thus, in the steering MCUs 62a and 62b, if the reaction force main system 80a and the reaction force sub-system 80b are abnormal, the steering motors 50a and 50b are controlled based on the sensor operation amount δs. As a result, the wheels 10 can be steered more effectively compared to the automatic retraction device described in Patent Document 1. Furthermore, when the abnormality control program shown in the flowcharts of Figures 5 and 7 is executed, the steering torque deficiency during abnormalities can be compensated for more effectively compared to when the abnormality control program shown in the flowchart of Figure 6 is executed, and the wheels 10 can be steered more effectively. For example, even if so-called stationary steering is performed (even if the steering operation member 20 is operated while the vehicle is stopped), the wheels 10 can be steered effectively.

[0060] On the other hand, the main estimated manipulated variable δa, the sub estimated manipulated variable δb, and the sensor manipulated variable δs are not necessarily the same. For example, the neutral position when acquiring the main estimated manipulated variable δa, the sub estimated manipulated variable δb, and the sensor manipulated variable δs may differ, resulting in different values. In addition, the rotation angle Θm of the reaction motors 26a and 26b is acquired by accumulating the detected values ​​of the motor rotation angle sensors 32a and 32b, but discrepancies may occur between the main estimated manipulated variable δa, the sub estimated manipulated variable δb, and the sensor manipulated variable δs due to the accumulation of detected values.

[0061] Therefore, the target steering angle θ* of the wheel 10 determined based on the main estimated control variable δa and the sub-estimated control variable δb differs from the target steering angle θ* determined based on the sensor control variable δs, which may cause the steering angle of the wheel 10 to change abruptly and significantly. To address this, when switching from the control of the steering motors 50a and 50b based on the main estimated control variable δa and the sub-estimated control variable δb to the control of the steering motors 50a and 50b based on the sensor control variable δs due to an abnormality in the main reaction force system 80a and the sub-reaction force system 80b, the control of the steering motors 50a and 50b is gradually changed.

[0062] An example of a switching control program in this case is shown in the flowchart of Figure 8. In this embodiment, the case in which this switching control program is executed in the steering main MCU62a will be described. The explanation of execution in the steering sub MCU62b will be omitted.

[0063] In this embodiment, if an abnormality is detected in the reaction force main system 80a, the steering motor 50a is temporarily stopped. As mentioned above, this is because, even if the steering motor 50a is stopped during normal driving, the wheels 10 can still be steered to the target steering angle θ*, and controlling it to have an understeer tendency can suppress a decrease in the vehicle's driving stability.

[0064] In S101, it is determined whether the reaction force main system 80a is abnormal or not. If the reaction force main system 80a is normal and the determination is NO, then in S102, normal control is performed. That is, the steering motor 50a is controlled based on the main estimated control input δa.

[0065] If the reaction force main system 80a is abnormal and the judgment in S101 is YES, then in S103, it is determined whether or not this is the first time that the abnormality of the reaction force main system 80a has been detected. For example, it is determined whether the judgment in S101 was NO during the previous execution of this program and is now YES.

[0066] If the determination in S103 is YES, the steering motor 50a is stopped in S104. The steering motor 50a may be stopped immediately or by gradually reducing the steering torque. In S105, it is determined whether or not the steering motor 50a has stopped. For example, if the current Ia to the steering motor 50a is 0, or if no steering torque is output by the electric motor 50a, it can be determined that the steering motor 50a has stopped. Steps S104 and S105 are executed repeatedly until the steering motor 50a has stopped.

[0067] If the S105 determination is YES, then in S106, it is determined whether the sensor operation amount δs can be used. For example, this applies if the sensor operation amount δs is not of an inappropriate size (e.g., does not exceed the upper or lower limit), or if the absolute value of the difference between the sensor operation amount δs and the previously acquired main estimated operation amount δa is less than or equal to the set value. If the operation amount sensor 36 is abnormal, or if a communication error occurs in G-CAN66, the sensor operation amount δs may be determined to be unusable, and the determination in S106 may be NO.

[0068] If the determination in S106 is YES, in S107 the target steering angle θ* of the wheel 10 is obtained based on the sensor operation amount δs. In addition, the target motor rotation angle θm*a of the steering motor 50a corresponding to the target steering angle θ* of the wheel 10 is obtained, and the target steering torque T*a of the steering motor 50a is obtained. In S108, the supply current Ia to the steering motor 50a is gradually increased to gradually increase the steering torque output by the steering motor 50a. In S109, the actual steering torque Ts of the steering motor 50, which is determined based on the actual current Is, which is the current flowing through the steering motor 50a detected by the current sensor 54a, is obtained, and it is determined whether the actual steering torque Ts has reached the target steering torque T*.

[0069] For example, in S108, the deviation ΔT between the target steering torque T* obtained in S107 and the actual steering torque Ts can be divided by n, and the supply current I can be gradually increased by ΔT / n in a single control cycle to approach the target steering torque T*. Alternatively, the supply current Ia to the steering motor 50a can be increased by a predetermined increment of ΔIa.

[0070] In any case, steps S108 and S109 are executed repeatedly until the determination in S109 is YES. Once the determination in S109 is YES, in S110, the steering motor 50a is controlled from then on based on the sensor operation amount δs.

[0071] On the other hand, if the judgment in S106 is NO, and it is determined that the sensor operation amount δs cannot be used to control the steering motor 50, then in S111, the steering motor 50a remains stopped.

[0072] Furthermore, a step can be added to determine whether the reaction force sub-system 80b is functioning correctly before S111 is executed. S111 can be executed only if the reaction force sub-system 80b is functioning correctly and the determination in this step is YES. It is reasonable to keep the steering motor 50a in a stopped state when the steering motor 50b is operating. On the other hand, it is considered unlikely that both the reaction force main system 80a and the reaction force sub-system 80b will be abnormal.

[0073] If the determination in S103 is NO, and it is not the first time that the reaction force main system 80a has been detected as abnormal, then in S112, it is determined whether the sensor input amount δs is usable. If the determination is YES, S110 is executed; if the determination is NO, S111 is executed. After the switching control is completed, the steering motor 50a is either controlled based on the sensor input amount δs or held in a stopped state.

[0074] In Figure 10, the change in steering torque of the steering motor 50a when this program is executed is shown by a solid line, and the change in steering torque of the steering motor 50a when the supply current Ia is increased immediately after the steering motor 50a is stopped is shown by a dashed line. Comparing these, it can be seen that by executing this switching control program, the steering torque output by the steering motor 50a can be gradually increased, and the change in the steering angle of the wheels 10 can be suppressed. This suppresses a decrease in the vehicle's driving stability and reduces discomfort for the driver.

[0075] Furthermore, it is not essential to temporarily stop the steering motor 50a if the reaction force main system 80a is abnormal. In this embodiment, the control of the steering motor 50a can be gradually changed from control based on the main estimated control amount δa to control based on the sensor control amount δs without temporarily stopping the steering motor 50a. An example of the control program during this switching is shown in the flowchart of Figure 9. The case in which this program is executed in the steering main MCU 62a will be explained. The same execution occurs in the steering sub MCU 62b, so the explanation for that is omitted.

[0076] S121-S123 are executed in the same manner as S101-S103 described above. In S121, it is determined whether or not the reaction force main system 80a is abnormal. If it is normal, in S122 the steering motor 50a is controlled based on the main estimated control amount δa. If the reaction force main system 80a is abnormal, in S123 it is determined whether or not this is the first time that the reaction force main system 80a has been determined to be abnormal.

[0077] If the determination in S123 is YES, then in S124, it is determined whether the sensor operation amount δs is usable. If the determination is NO, then in S125, 126, and 127, the steering motor 50a is stopped, similar to the execution of S104, 105, and 111 described above, and then the steering motor 50a is held in the stopped state.

[0078] If the determination in S124 is YES, in S128 the target steering torque T* of the electric motor 50a is obtained based on the sensor operation amount δs. In S129, it is determined whether the absolute value of the difference between the target steering torque T* based on the sensor operation amount δs and the actual steering torque Ts of the steering motor 50a is less than the threshold Tth, or whether the target steering torque T* based on the sensor operation amount δs is less than the actual steering torque Ts.

[0079] If the absolute value of the difference between the target steering torque T* based on the sensor input δs and the actual steering torque Ts of the steering motor 50a is greater than or equal to the threshold Tt, then when switching from controlling the steering motor 50a based on the main estimated input δa to controlling the steering motor 50a based on the sensor input δs, the steering angle will change significantly, which is undesirable.

[0080] Furthermore, when switching from controlling the steering motor 50a based on the main estimated input δa to controlling the steering motor 50a based on the sensor input δs, if the steering angle increases against the driver's intention, the vehicle may unintentionally tend to oversteer, which is undesirable from the standpoint of driving stability.

[0081] As described above, if the judgment in S129 is NO, the system is prevented from directly switching from control based on the main estimated manipulated variable δa to control based on the sensor manipulated variable δs.

[0082] If the determination in S129 is YES, then in S130 and S131, the current supplied to the steering motor 50a is gradually changed, and it is determined whether the actual steering torque Ts of the steering motor 50a has gradually changed and approached the target steering torque T* based on the sensor operation amount δs. S130 and S131 are executed repeatedly until the actual steering torque T of the steering motor 50a approaches the target steering torque T*. If the determination in S131 is YES, then in S132, the steering motor 50a is controlled based on the sensor operation amount δs.

[0083] Furthermore, a step can be added before S129 or S130 to determine whether the rate of change of the sensor operation amount δs is less than the set speed, or whether the vehicle is stopped (whether the vehicle's speed is below the set speed), and S130 can be executed if the determination is YES. Changing the control of the steering motor 50a when the steering speed is high is undesirable from the standpoint of suppressing a decrease in driving stability. Also, changing the control of the steering motor 50a when the vehicle is stopped can improve safety.

[0084] Conversely, if the determination in S129 is NO, then in S133-136, the steering motor 50a is stopped, similar to the execution of S104, 105, 108, and 109 described above. Subsequently, the supply current Ia to the steering motor 50a is gradually increased, and the actual steering torque Ts is brought closer to the target steering torque T* determined based on the sensor operation amount δs. If the determination in S136 is YES, then in S132, the steering motor 50a is controlled based on the sensor operation amount δs.

[0085] If the result of S123 is NO, then in S137, it is determined whether the sensor operation amount δs is usable. If the result is YES, S132 is executed; if the result is NO, S127 is executed.

[0086] Figure 11 shows an example of the change in steering torque of the steering motor 50a when this program is executed. In this embodiment, as shown by the solid line, the steering torque of the steering motor 50a is gradually changed from control based on the main estimated control amount δa to control based on the sensor control amount δs without stopping the steering motor 50a. As a result, compared to the case shown by the dashed line, it is possible to suppress abrupt changes in the steering angle of the wheels 10 and suppress a decrease in the vehicle's driving stability. In addition, it is possible to reduce discomfort for the driver.

[0087] As described above, in this embodiment, the manipulated amount estimation unit is composed of a part of the operating control unit 30 that stores the manipulated amount estimation program, a part that executes the program, and so on. Furthermore, the reaction force main system 80a corresponds to the first reaction force control system, and the reaction force sub-system 80 corresponds to the second reaction force control system.

[0088] The structure of the steering device 14 is not limited. For example, it can also be applied to a steering device in which each of a pair of wheels 10 is provided with a steering actuator, and each wheel is steered by each of the steering actuators.

[0089] Furthermore, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0090] 12: Operating device 14: Steering device 26,26a,26b: Reaction motor 30: Operating side control unit 32a,32b: Motor rotation angle sensor 34a,34b: Torque sensor 36: Maneuver amount sensor 38: Reaction force application mechanism 45: Steering control unit 50,50a,50b: Steering motor 52a,52b: Motor rotation angle sensor 54a,54b: Current sensor 58: Steering mechanism 60a,60b: Reaction force MCU 62a,62b: Steering MCU 61,63: Communication line 68,70: L-CAN 66: G-LAN Patentable invention

[0091] (1) A steering system for steering a pair of wheels that are mechanically isolated from a steering control member installed on a vehicle and operable by the driver, An operation amount sensor for detecting the amount of operation performed by the driver on the steering operation member, An operating amount estimation unit that estimates the amount of operation of the steering operating member without relying on the detected value of the operating amount sensor, A steering mechanism comprising at least one steering actuator, which steers the pair of wheels by the operation of the steering actuator, A steering control unit controls the steering angle of the pair of wheels by controlling the at least one steering actuator based on the amount of operation of the steering operating member. Includes, A steering system in which the steering control unit controls the at least one steering actuator based on an estimated operating amount, which is the operating amount of the steering operating member estimated by the operating amount estimation unit, when the operating amount estimation system, including the operating amount estimation unit, is functioning normally, and controls the at least one steering actuator based on a sensor operating amount, which is the operating amount of the steering operating member detected by the operating amount sensor, when the operating amount estimation system is abnormal.

[0092] The steering mechanism may have a structure in which one steering actuator is provided for each pair of wheels, or it may have a structure in which a steering actuator is provided for each of the wheels in the pair.

[0093] The manipulated variable estimation system includes at least one of the reaction force main system 80a and the reaction force sub-system 80b. The estimated manipulated variable includes at least one of the main estimated manipulated variable and the sub-estimated manipulated variable.

[0094] (2) The steering control unit controls the steering actuator based on the sensor operation amount if the operation amount estimation system is abnormal and the sensor operation amount detected by the operation amount sensor is a value suitable for controlling the steering actuator, as described in (1).

[0095] If the control sensor is malfunctioning, or if there is a problem with communication between the control sensor and the steering control unit, the value detected by the control sensor may be unsuitable for controlling the steering actuator.

[0096] If the value detected by the maneuvering sensor is inappropriate, the steering actuator can be stopped, or, as described above, the steering actuator can be controlled based on the estimated maneuvering amount estimated by the first reaction force control unit and the second reaction force control unit.

[0097] (3) The steering system The steering shaft to which the steering operating member is connected is equipped with a reaction force actuator connected via a reaction force transmission mechanism, and the reaction force applying mechanism applies an operating reaction force to the steering operating member by the operation of the reaction force actuator, A reaction force control unit controls the reaction force applied to the steering operating member by controlling the reaction force actuator. Includes, The steering system according to (1) or (2), wherein the control amount estimation unit estimates the amount of operation of the steering control member based on the rotation angle of the reaction force actuator.

[0098] The steering control member described in this section is rotatable. Since the steering control member and the reaction force actuator are connected via a steering shaft, there is a one-to-one relationship between the amount of movement of the steering control member and the amount of rotation of the reaction force actuator. The amount of movement estimation unit may be included in the reaction force control unit.

[0099] The presence or absence of an abnormality in the control input estimation system can be detected in the steering control unit, or in a separate control unit (for example, the overall control unit). In addition, the presence or absence of an abnormality in the control input estimation system may also be detected in the control input estimation unit.

[0100] (4) The steering system according to item (1) or (2), wherein the operation amount estimation unit estimates the amount of operation of the steering operating member based on the operation torque applied to the steering operating member by the driver.

[0101] (5) The steering system according to any one of (1) to (4), wherein when the steering control unit detects an abnormality in the manipulative amount estimation system, it gradually changes the control of the at least one steering actuator from the control of the at least one steering actuator based on the estimated manipulative amount to the control of the at least one steering actuator based on the sensor manipulative amount.

[0102] For example, gradual changes in the control of a steering actuator include gradual changes in the current supplied to the steering actuator, gradual changes in the steering torque which is the output of the steering actuator, gradual changes in the rotation angle of the steering actuator, and gradual changes in the steering angle of the wheels.

[0103] (6) The steering control unit, when it detects an abnormality in the manipulative amount estimation system, stops the at least one steering actuator, and then gradually increases the current supplied to the at least one steering actuator so that the steering angle of the pair of wheels approaches a target steering angle determined based on the sensor manipulative amount, as described in (5).

[0104] There is a one-to-one correspondence between the motor rotation angle, which is the rotation angle of the steering actuator, and the steering angle of the wheel. Based on the sensor input, the target steering angle of the wheel is obtained, and based on the target steering angle, the target motor rotation angle of the steering actuator is obtained. Furthermore, based on the deviation between the target motor rotation angle and the actual motor rotation angle, which is the actual rotation angle of the steering actuator, the target steering torque, which is the torque required of the steering actuator to bring the actual motor rotation angle closer to the target motor rotation angle, is obtained. Then, as the current supplied to the steering actuator increases, the steering torque generated in the steering actuator increases, the rotation angle of the steering actuator increases, and the steering angle of the wheel increases.

[0105] Based on the above, the “steering angle of a pair of wheels” described in paragraph (6) can be replaced with “rotation angle of at least one steering actuator” or “steering torque of at least one steering actuator,” etc. The same applies to paragraphs (7) and (8).

[0106] Furthermore, at least one steering actuator is often controlled similarly. It is desirable that a pair of wheels be steered to similar steering angles.

[0107] (7) The steering control unit, when it detects an abnormality in the manipulative amount estimation system, gradually changes the current supplied to at least one steering actuator to bring the steering angle of the pair of wheels closer to the target steering angle if the absolute value of the difference between the actual steering angle of the pair of wheels and the target steering angle determined based on the sensor manipulative amount is less than a threshold value, as described in (5).

[0108] The actual steering angles of the pair of wheels can be replaced with target steering angles determined based on the estimated control input immediately before an anomaly in the control input estimation system is detected. The same applies to item (7).

[0109] (8) The steering control unit, when it detects an abnormality in the manipulative amount estimation system, and the actual steering angle of the pair of wheels is greater than the target steering angle determined based on the sensor manipulative amount, gradually changes the current supplied to the at least one steering actuator to bring the steering angle of the pair of wheels closer to the target steering angle, according to item (5) or (7).

[0110] (9) The steering system The steering shaft to which the steering operating member is connected is provided with a reaction force actuator via a reaction force transmission mechanism, and the reaction force applying mechanism applies an operating reaction force to the steering operating member by the operation of the reaction force actuator, The system includes a reaction force control unit that controls the reaction force actuator and controls the operating reaction force, The manipulated amount estimation unit is included in the reaction force control unit, The reaction actuator includes a first reaction motor and a second reaction motor, which are electric motors. The reaction force control unit includes a first reaction force control unit provided in correspondence with the first reaction force motor, and a second reaction force control unit, separate from the first reaction force control unit, provided in correspondence with the second reaction force motor. One steering actuator, which is at least one steering actuator, steers the pair of wheels. The steering actuator includes a first steering motor and a second steering motor, which are electric motors. The steering system according to any one of (1) to (8), wherein the steering control unit includes a first steering control unit that controls the first steering motor and a second steering control unit, separate from the first steering control unit, that controls the second steering motor.

[0111] (10) The steering system according to item (9), wherein the first steering control unit controls the first steering motor based on the estimated manipulated amount estimated by the first reaction force control unit when the first reaction force control system, including the first reaction force control unit, is functioning normally, and controls the first steering motor based on the sensor manipulated amount when the first reaction force control system is abnormal.

[0112] (11) The steering system according to item (9), wherein the first steering control unit controls the first steering motor based on the first estimated manipulated amount as the estimated manipulated amount estimated by the first reaction force control unit when the first reaction force control system including the first reaction force control unit is normal, and stops the first steering motor when the second reaction force control system including the second reaction force control unit is normal and the first reaction force control system is abnormal.

[0113] (12) The steering system according to item (9), wherein the first steering control unit controls the first steering motor based on a second estimated manipulated amount, which is an estimated manipulated amount estimated by the second reaction control unit, when the first reaction force control system, which includes the first reaction force control unit, is abnormal and the second reaction force control system, which includes the second reaction force control unit, is normal.

[0114] (13) The steering system according to any one of items (9) to (12), wherein the first steering control unit controls the first steering motor based on the value detected by the manipulated amount sensor when both the first reaction force control system including the first reaction force control unit and the second reaction force control system including the second reaction force control unit are abnormal.

[0115] (14) The steering system according to any one of items (9) to (13), wherein the steering system includes an abnormality detection unit that detects whether or not there is an abnormality in the first reaction force control system including the first reaction force control unit and the second reaction force control system including the second reaction force control unit.

[0116] In the above embodiment, it can be considered that the abnormality detection unit is composed of at least one of the steering main MCU62a and the steering sub MCU62b.

Claims

1. A steering system for steering a pair of wheels that are mechanically isolated from steering control members installed on a vehicle and operated by the driver, An operation amount sensor for detecting the amount of operation performed by the driver on the steering operation member, An operating amount estimation unit that estimates the amount of operation of the steering operating member without relying on the detected value of the operating amount sensor, A steering mechanism comprising at least one steering actuator, which steers the pair of wheels by the operation of the steering actuator, A steering control unit controls the steering angle of the pair of wheels by controlling the at least one steering actuator based on the amount of operation of the steering operating member. Includes, A steering system in which the steering control unit controls the at least one steering actuator based on an estimated operating amount, which is the operating amount of the steering operating member estimated by the operating amount estimation unit, when the operating amount estimation system including the operating amount estimation unit is functioning normally, and controls the at least one steering actuator based on a sensor operating amount, which is the operating amount of the steering operating member detected by the operating amount sensor, when the operating amount estimation system is abnormal.

2. The steering system according to claim 1, wherein the steering control unit controls the steering actuator based on the sensor operation amount when the operation amount estimation system is abnormal and the sensor operation amount detected by the operation amount sensor is a value suitable for controlling the steering actuator.

3. The steering system, The steering shaft to which the steering operating member is connected is equipped with a reaction force actuator connected via a reaction force transmission mechanism, and the reaction force applying mechanism applies an operating reaction force to the steering operating member by the operation of the reaction force actuator, A reaction force control unit controls the reaction force applied to the steering operating member by controlling the reaction force actuator. Includes, The steering system according to claim 1 or 2, wherein the operation amount estimation unit estimates the amount of operation of the steering operation member based on the rotation angle of the reaction force actuator.

4. The steering system according to claim 1 or 2, wherein when the steering control unit detects an abnormality in the operation amount estimation system, it gradually changes the control of the at least one steering actuator when switching from the control of the at least one steering actuator based on the estimated operation amount to the control of the at least one steering actuator based on the sensor operation amount.

5. The steering system according to claim 4, wherein the steering control unit, when it detects an abnormality in the operation amount estimation system, stops the at least one steering actuator, and then gradually increases the current supplied to the at least one steering actuator so that the steering angle of the pair of wheels approaches a target steering angle determined based on the sensor operation amount.

6. The steering control unit, when it detects an abnormality in the operation amount estimation system, gradually changes the current supplied to at least one steering actuator in at least one of the following cases: when the absolute value of the difference between the actual steering angle of the pair of wheels and the target steering angle determined based on the sensor operation amount is less than a threshold value, or when the actual steering angle of the pair of wheels is greater than the target steering angle determined based on the sensor operation amount, thereby bringing the steering angle of the pair of wheels closer to the target steering angle, according to claim 4.

7. The steering system, The steering shaft to which the steering operating member is connected is provided with a reaction force actuator via a reaction force transmission mechanism, and the reaction force applying mechanism applies an operating reaction force to the steering operating member by the operation of the reaction force actuator, The system includes a reaction force control unit that controls the reaction force actuator and controls the operating reaction force, The manipulated amount estimation unit is included in the reaction force control unit, The reaction actuator includes a first reaction motor and a second reaction motor, which are electric motors. The reaction force control unit includes a first reaction force control unit provided in correspondence with the first reaction force motor, and a second reaction force control unit, separate from the first reaction force control unit, provided in correspondence with the second reaction force motor. One of the steering actuators, which is at least one steering actuator, steers the pair of wheels. The steering actuator includes a first steering motor and a second steering motor, which are electric motors. The steering control unit includes a first steering control unit that controls the first steering motor, and a second steering control unit, separate from the first steering control unit, that controls the second steering motor. The steering system according to claim 1 or 2, wherein the first steering control unit controls the first steering motor based on the estimated operation amount estimated by the first reaction force control unit when the first reaction force control system, including the first reaction force control unit, is functioning normally, and controls the first steering motor based on the sensor operation amount when the first reaction force control system is abnormal.

8. The steering system, The steering shaft to which the steering operating member is connected is provided with a reaction force actuator via a reaction force transmission mechanism, and the reaction force applying mechanism applies an operating reaction force to the steering operating member by the operation of the reaction force actuator, The system includes a reaction force control unit that controls the reaction force actuator and controls the operating reaction force, The manipulated amount estimation unit is included in the reaction force control unit, The reaction actuator includes a first reaction motor and a second reaction motor, which are electric motors. The reaction force control unit includes a first reaction force control unit provided in correspondence with the first reaction force motor, and a second reaction force control unit, separate from the first reaction force control unit, provided in correspondence with the second reaction force motor. One of the steering actuators, which is at least one steering actuator, steers the pair of wheels. The steering actuator includes a first steering motor and a second steering motor, which are electric motors. The steering control unit includes a first steering control unit that controls the first steering motor, and a second steering control unit, separate from the first steering control unit, that controls the second steering motor. The steering system according to claim 1 or 2, wherein the first steering control unit controls the first steering motor based on the value detected by the manipulated amount sensor if both the first reaction force control system including the first reaction force control unit and the second reaction force control system including the second reaction force control unit are abnormal.

Images