Steering control device, steering control method, and steer-by-wire system

Abstract

To provide a steering control device, a steering control method and a steer-by-wire system, capable of restraining electric power from being wastefully consumed in an actuator for imparting steering force to a wheel, in positioning of an operation quantity of a steering input member and a steering angle of the wheel.SOLUTION: Acquiring a first physical quantity related to a traveling state of a vehicle, a second physical quantity related to an operation state of a steering input member, and a third physical quantity related to an output of a second actuator that applies a steering force to wheels, the first physical quantity indicating that the traveling state of the vehicle is a stopped state, the second physical quantity indicating that the operation state of the steering input member is an unoperated state; When an output value of the third physical quantity to the second actuator is equal to or greater than a predetermined value, a first target control amount in a turning force suppression control state in which a turning force applied to the wheel by the second actuator is suppressed is acquired, and a signal corresponding to the first target control amount is output.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a steering control device, a steering control method, and a steer-by-wire system. [Background technology]

[0002] The steering control device of Patent Document 1 performs feedback control of pinion angle θp so that pinion angle θp follows target pinion angle θp*, thereby calculating a turning-side target current value that is a target value for the drive current to be supplied to the turning motor, controlling the operation of the turning motor based on the turning-side target current value, and performing a reduction process to reduce the drive current supplied to the turning motor. The drive current reduction process is performed when at least one of a traveling state variable such as vehicle speed and a steering state variable such as steering torque is a state variable that indicates that the target pinion angle θp* will not change. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-049971 Summary of the Invention [Problem to be solved by the invention]

[0004] In a steer-by-wire system, when the vehicle is stopped, for example, if there is an obstacle that physically prevents the wheels (steered wheels) from returning to the neutral position, the steering input member may be returned to the neutral position, causing a discrepancy between the amount of operation of the steering input member and the steering angle of the wheels. In this case, if the steering force applied by the actuator to the wheel does not return the wheel to the neutral position, a torque command to return the steered wheel to the neutral position will continue to be output to the actuator, which could result in unnecessary power consumption by the actuator. Furthermore, when the vehicle is stopped, for example, when the wheels are returning to their neutral positions, torsion occurs in the tires, which are the wheels, and even if the steering input member that has been returned to the neutral position is released, a torque command that attempts to maintain the wheels in the neutral position continues to be output to the actuator, which could result in unnecessary power consumption by the actuator. As described above, the situation in which a torque command is continuously output to the actuator while the vehicle is stopped may also occur when noise is superimposed on the detection signal of the steering angle of the wheels.

[0005] Therefore, an object of the present invention is to provide a steering control device, a steering control method, and a steer-by-wire system that can prevent unnecessary consumption of power by an actuator that applies a steering force to the wheels when aligning the operation amount of a steering input member with the steering angle of the wheels. [Means for solving the problem]

[0006] In one aspect, the steering control device, steering control method, and steer-by-wire system according to the present invention acquire a first physical quantity related to the running state of the vehicle, a second physical quantity related to the operation state of a steering input member, and a third physical quantity related to the output of a second actuator that applies a steering force to the wheels, and when the first physical quantity indicates that the running state of the vehicle is stopped, the second physical quantity indicates that the operation state of the steering input member is not operated, and the third physical quantity is such that the output value of the second actuator is equal to or greater than a predetermined value, acquire a first target control quantity that will result in a steering force suppression control state in which the second actuator suppresses the steering force applied to the wheels, and output a signal corresponding to the first target control quantity. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent unnecessary consumption of power by an actuator that applies a steering force to the wheels. [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 1 is a schematic diagram of a vehicle equipped with a steer-by-wire system. [Figure 2] FIG. 10 is a diagram showing state transitions in alignment control. [Figure 3] 10A and 10B are diagrams illustrating reaction motor control and steering motor control for each control state. [Figure 4] FIG. 10 is a diagram illustrating a scene in which a steering torque command continues to be output while the vehicle is stopped. [Figure 5] FIG. 10 is a diagram showing another example of a scene in which a steering torque command continues to be output while the vehicle is stopped. [Figure 6] 3 is a flowchart showing a control flow of the steer-by-wire system. [Figure 7] FIG. 2 is a functional block diagram of a steering control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a steering control device, a steering control method, and a steer-by-wire system according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a vehicle 100 equipped with a steer-by-wire system 200. As shown in FIG. The vehicle 100 is a four-wheeled automobile equipped with a pair of left and right front wheels 101, 102 and a pair of left and right rear wheels 103, 104.

[0010] Steer-by-wire system 200 has a steering input device 300 to which the steering operation of the driver of vehicle 100 is input via steering wheel 310, a steering device 400 equipped with a steering actuator that applies a steering force to the wheels of vehicle 100 (more specifically, steerable wheels, for example front wheels 101, 102), and a steering control device 500 that controls the actuator equipped in steer-by-wire system 200.

[0011] In steer-by-wire system 200, steering input device 300 and turning device 400 are mechanically separated. In other words, in steer-by-wire system 200, steering wheel 310, which is a steering input member, and the steered wheels are mechanically separated. The steering input member is not limited to the steering wheel 310, but may be a lever, a joystick, or the like.

[0012] The steering input device 300 includes a steering wheel 310 , a steering shaft 320 , a reaction force motor 330 , and an operation angle sensor 340 . Reaction motor 330 is a reaction actuator (first actuator) provided to impart a steering reaction torque to steering wheel 310 in a pseudo manner. That is, the steering input device 300 is a device into which the driver's steering operation is input via the steering wheel 310, and has a reaction motor 330 that applies a steering reaction torque to the steering wheel 310.

[0013] The operation angle sensor 340 detects the rotation angle of the steering shaft 320 as an operation angle θ of the steering wheel 310 (in other words, an operation amount or an operation position). Specifically, the steering angle sensor 340 detects the neutral position of the steering wheel 310 as an steering angle θ=0 degrees. For example, when the steering wheel 310 is operated to the left from the neutral position, the operation angle sensor 340 detects the operation angle θ as a positive angle, and when the steering wheel 310 is operated to the right from the neutral position, the operation angle sensor 340 detects the operation angle θ as a negative angle.

[0014] The steering device 400 has a steering motor 410 as a steering actuator (second actuator), a steering mechanism 420 that changes the steering angle δ of the front wheels 101, 102 using the steering torque generated by the steering motor 410, and a steering angle sensor 430 that detects the steering angle δ of the front wheels 101, 102. Steering mechanism 420 is a mechanism that changes the steering angle δ of front wheels 101, 102 by converting the rotational motion of steering motor 410 into linear motion of a rack bar using, for example, a rack and pinion system.

[0015] Steering angle sensor 430 detects the rotational position of steering motor 410 or the position of a rack bar of steering mechanism 420, for example, to detect steering angle δ of front wheels 101, 102. Specifically, the steering angle sensor 430 detects the neutral position of the front wheels 101, 102 as a steering angle δ=0 degrees. The steering angle sensor 430 detects the steering angle δ as a positive angle when the front wheels 101, 102 are steered to the left from the neutral position, and detects the steering angle δ as a negative angle when the front wheels 101, 102 are steered to the right from the neutral position.

[0016] The neutral position of the front wheels 101, 102 is a position where the front wheels 101, 102 are not steered to either the left or right, and the vehicle 100 is traveling straight ahead. The neutral position of the steering wheel 310 is a position where the steering wheel 310 is not operated to either the left or right and the front wheels 101, 102 are in a neutral position.

[0017] Steering control device 500 is an electronic control device equipped with MCU (Micro Controller Unit) 510, and controls the operation of steer-by-wire system 200 by outputting control signals to reaction force motor 330 (first actuator) and steering motor 410 (second actuator). The MCU 510 can also be referred to as a microcomputer, a processor, a processing unit, an arithmetic unit, or the like.

[0018] Then, MCU 510 performs arithmetic processing on various signals acquired from the outside to determine a control signal for reaction force motor 330 and a control signal for steering motor 410, and outputs the determined control signals. That is, MCU 510 has a function as a control section that outputs control signals to reaction force motor 330 and steering motor 410, in other words, a function as a control section that executes a steering control method.

[0019] The vehicle 100 is provided with an activation switch 650 that activates various systems of the vehicle 100, such as a power switch or an ignition switch, and the steering control device 500 acquires an on / off signal of the activation switch 650. The systems activated by the activation switch 650 include the steer-by-wire system 200 . When activation switch 650 is turned on, steer-by-wire system 200 is powered on and activated, entering the system-on state. The vehicle 100 also includes wheel speed sensors 621-624 that detect wheel speeds WS1-WS4, which are the rotational speeds of the wheels 101-104, respectively.

[0020] The MCU 510 acquires signals indicating physical quantities related to the wheel speeds WS1-WS4 output by the wheel speed sensors 621-624 (or signals indicating physical quantities related to the vehicle speed VS calculated from the outputs of the wheel speed sensors 621-624), signals indicating physical quantities related to the operating angle θ output by the operating angle sensor 340, and signals indicating physical quantities related to the steering angle δ output by the steering angle sensor 430. Then, MCU 510 calculates a steering angle command value δtg that is a target value for steering angle δ based on information about the operation angle θ of steering wheel 310. Furthermore, MCU 510 determines a control signal based on the deviation between steering angle δ detected by steering angle sensor 430 and steering angle command value δtg, and performs position control by outputting the determined control signal to steering motor 410.

[0021] Furthermore, MCU 510 calculates a reaction torque command value TRtg, which is a target value of reaction torque TR, based on information such as vehicle speed VS determined from wheel speeds WS1-WS4 and operation angle θ of steering wheel 310. In addition, the MCU 510 can obtain the vehicle speed VS by acquiring the signals of the wheel speeds WS1-WS4 from the wheel speed sensors 621-624, and can also obtain information on the vehicle speed VS that other electronic control devices have calculated based on the signals of the wheel speeds WS1-WS4 via the in-vehicle network.

[0022] Then, the MCU 510 outputs a control signal based on the reaction torque command value TRtg to the reaction motor 330. In this way, MCU 510 controls the operation of steer-by-wire system 200 by controlling the steering force applied to front wheels 101, 102 and the reaction torque applied to steering wheel 310.

[0023] Furthermore, MCU 510 acquires outputs from a shift position sensor 630 that detects the shift position (gear position) of the automatic transmission of vehicle 100 and an accelerator operation amount sensor 660 that detects the accelerator operation amount AC by the driver, for use in controlling the alignment of the operation position of steering wheel 310 with the steering angle δ of front wheels 101, 102, as will be described later, and for intervening in the power-saving operation of steering motor 410. Furthermore, the MCU 510 controls the operation of a warning device 640 provided in the vehicle 100 to notify the driver of the vehicle 100 that the alignment control has been performed. The warning device 640 may be a warning lamp, a liquid crystal display device, a voice guidance device, or the like.

[0024] In steer-by-wire system 200, because steering wheel 310 and front wheels 101, 102 are mechanically separated, there may be a static misalignment between the operating position of steering wheel 310 and the steering angle δ of front wheels 101, 102. Therefore, when the deviation AD of the steering angle δ of the front wheels 101, 102 from the steering angle θ of the steering wheel 310 is equal to or greater than the static allowable amount, the MCU 510 performs alignment control to actively change the steering angle θ or the steering angle δ using an actuator.

[0025] The deviation amount AD is an error between the actual steering angle δ and the steering angle command value δtg, which is uniquely determined based on the operation angle θ of the steering wheel 310 . Furthermore, when MCU 510 actively changes the operation angle θ of steering wheel 310 in the positioning control, MCU 510 causes reaction motor 330 to generate a rotational driving force that rotates steering wheel 310 to a position corresponding to the turning angle δ.

[0026] FIG. 2 is a diagram showing the transition of the control state in the alignment control by the steering control device 500. 2. FIG. 3 also shows the control modes of the steering input device 300 (reaction motor 330) and the turning device 400 (turning motor 410) in each control state shown in FIG. In one aspect of the alignment control, the control state can be switched to five patterns from the 0th control state to the 4th control state.

[0027] The 0th control state is the initial control state when the steer-by-wire system 200 is turned on by turning on the activation switch 650 (in other words, the ignition switch IGN-SW), that is, immediately after the steering control device 500 is activated. In the zeroth control state, steering control device 500 stops drive control of reaction force motor 330 and steering motor 410, in other words, reaction force motor 330 and steering motor 410 are not controlled.

[0028] In this zeroth control state, the steering control device 500 calculates the deviation AD [deg] of the steering angle δ (more specifically, the value detected by the steering angle sensor 430) of the front wheels 101, 102 relative to the operating angle θ of the steering wheel 310 (more specifically, the steering angle command value δtg based on the operating angle θ), and compares the calculated deviation AD with the allowable amount TD. Then, when the deviation amount AD is equal to or greater than the allowable amount TD and the vehicle 100 is in a stopped state where the vehicle speed VS is equal to or less than the vehicle speed threshold, the steering control device 500 transitions to the first control state. The deviation amount AD is the absolute value of the deviation angle.

[0029] In the first control state, the steering control device 500 performs position control of the steering input device 300 by driving and controlling the reaction force motor 330 of the steering input device 300 to bring the operating angle θ of the steering wheel 310 closer to the operating angle θ corresponding to the steering angle δ of the front wheels 101, 102 at that time, and reduce the deviation amount AD to less than the allowable amount TD. In addition, in the first control state, the steering control device 500 performs stationary control of the steering motor 410 so that the steering angle δ of the front wheels 101, 102 is not changed. In other words, in the first control state, the steering control device 500 rotates the steering wheel 310 with the force applied by the reaction force motor 330 without changing the steering angle δ, and changes the rotational position of the steering wheel 310 to a position that corresponds to the steering angle δ at that time.

[0030] In the first control state, the steering control device 500 limits the torque applied to the steering wheel 310 by the reaction force motor 330 and the rotation speed when the steering wheel 310 is rotated by the application of this torque. In detail, the steering control device 500 limits the rotational torque applied by the reaction motor 330 to such an extent that the driver can operate the steering wheel 310 against the rotational torque applied by the reaction motor 330. In addition, the steering control device 500 limits the rotation speed of the steering wheel 310 to a level that prevents the driver's hands from interfering with the steering wheel 310 and causing a shock to the driver when the steering wheel 310 automatically rotates.

[0031] In addition, the steering control device 500 activates the warning device 640 when in the first control state, that is, when the steering wheel 310 is automatically rotated by the rotational torque applied by the reaction motor 330, to notify the driver of the vehicle 100 that the steering wheel 310 will automatically rotate due to the implementation of alignment control. The warning issued by the warning device 640 allows the driver to recognize that alignment control is being performed, and prevents the driver from panicking even if the steering wheel 310 starts to rotate automatically. Furthermore, if the driver delays the start operation of the vehicle 100 due to the warning from the warning device 640, this will contribute to completing the alignment while the vehicle is stopped.

[0032] In this way, if the first control state is set when the vehicle 100 is stopped, the operating angle θ of the steering wheel 310 is changed while the steering angle δ of the front wheels 101, 102 is maintained. Therefore, even if alignment control is performed during suspension maintenance at a maintenance shop, for example, the steering angle δ of the front wheels 101, 102 will not move inadvertently, and the maintenance work can be carried out smoothly and safely. Furthermore, even if alignment is performed while the user of the vehicle 100 is parking the vehicle 100, the steering angle δ of the front wheels 101, 102 does not change, so it is possible to avoid movable objects located near the front wheels 101, 102 interfering with the tires.

[0033] On the other hand, if the steering control device 500 determines in the first control state that the deviation amount AD is less than the allowable amount TD, that is, if the steering angle δ of the front wheels 101, 102 is an angle that corresponds to the operating angle θ of the steering wheel 310 and no deviation that requires alignment control has occurred, it transitions to the second control state. The second control state is a state in which normal control of reaction force motor 330 and steering motor 410 is carried out. That is, in the second control state, the steering control device 500 performs reaction torque control to control the reaction motor 330 so that the reaction motor 330 generates a pseudo steering reaction force, and also performs position control to control the steering motor 410 so that the steering angle δ of the front wheels 101, 102 becomes an angle corresponding to the operating angle θ of the steering wheel 310.

[0034] Furthermore, when alignment in the first control state is completed, that is, when the deviation amount AD becomes less than the allowable amount TD due to a change in the operating angle θ of the steering wheel 310 by the reaction force motor 330, the steering control device 500 transitions to the second control state and performs normal control (reaction force torque control and position control) of the reaction force motor 330 and the turning motor 410. In this way, when the deviation amount AD falls below the allowable amount TD in the first control state, the steering control device 500 transitions to a normal steering control state in which a steering reaction torque is applied to the steering wheel 310 by the reaction motor 330, and a steering force based on the operating angle θ (operation information) of the steering wheel 310 is applied to the front wheels 101, 102 by the steering motor 410.

[0035] In addition, when the steering control device 500 detects that the vehicle 100 is starting to move before the alignment in the first control state is completed, that is, before the deviation amount AD becomes less than the allowable amount TD, it transitions to the third control state, cancels the alignment control, and enters the normal steering control state. Note that detection of vehicle 100 starting and running means, for example, detection of a vehicle speed VS higher than a vehicle speed threshold, in other words, detection of the transition of vehicle 100 from a stopped state to a running state, or detection of the input of a vehicle speed signal. Furthermore, when the steering control device 500 detects that the vehicle 100 has started moving immediately from the zeroth control state, it also transitions to the third control state, cancels the alignment control, and switches to the normal steering control state.

[0036] In addition, when the steering control device 500 transitions to a normal steering control state and performs position control to bring the steering angle δ of the front wheels 101, 102 closer to the steering angle command value δtg based on the operating angle θ of the steering wheel 310, if a predetermined intervention condition is met, the steering control device 500 transitions to a fourth control state, which is a steering force suppression control state in which the steering force applied by the steering motor 410 is suppressed to a value smaller than that in the normal control state (including setting the steering force to zero), even if the deviation amount AD is greater than or equal to the allowable amount TD. Here, the transition condition to the fourth control state, i.e., the condition for intervention of steering force suppression control, is that the vehicle 100 is in a stopped state, the steering wheel 310 is not being operated, and the output torque (steering force) of the steering motor 410 is greater than or equal to a predetermined value.

[0037] In other words, the above-mentioned intervention condition is met when the vehicle is stopped, for example, when there is an obstacle that physically prevents the wheels (steered wheels) from returning to the neutral position, and the steering wheel 310 is returned to the neutral position, causing a discrepancy between the operating angle θ of the steering wheel 310 and the steering angle δ of the front wheels 101, 102. In this state, position control of steering motor 410 continues without the deviation amount AD becoming smaller, and steering motor 410 continues to output steering force, which results in unnecessary consumption of power by steering motor 410 and may also cause steering motor 410 to overheat. Therefore, the steering control device 500 suppresses power consumption in the steering motor 410 and temperature rise of the steering motor 410 by transitioning to a steering force suppression control state (fourth control state) in which the steering force applied by the steering motor 410 is suppressed to a smaller value than in the normal control state.

[0038] FIG. 4 illustrates a scene in which steering motor 410 continues to generate steering force without the deviation amount AD becoming smaller. After the vehicle 100 is stopped with the front wheels 101, 102 steered, if the driver performs an operation to return the steering wheel 310 to the neutral position, the steering control device 500 drives and controls the steering motor 410 to return the front wheels 101, 102 to the neutral position in accordance with the steering operation.

[0039] At this time, even if the front wheels 101, 102 hit an obstacle before returning to the neutral position and the steering operation stops, the state in which the deviation amount AD is generated is maintained, and therefore the steering torque continues to be applied to reduce the deviation amount AD. Here, if the steering system is a system in which the steering wheel 310 and the front wheels 101, 102 are mechanically connected, if the front wheels 101, 102 hit an obstacle before returning to the neutral position and the driver takes his / her hands off the steering wheel 310 to stop steering, the steering wheel 310 will be returned to a position corresponding to the steering angle δ of the front wheels 101, 102 at that time.

[0040] In contrast, in the steer-by-wire system 200 in which the steering wheel 310 and the front wheels 101, 102 are mechanically separated, even if the driver releases the steering wheel 310, the deviation amount AD is not eliminated, and the steering torque continues to be applied in order to reduce the deviation amount AD. Therefore, when the steering control device 500 reaches a state where the steering torque continues to be applied without the deviation amount AD becoming smaller as described above, it transitions to a steering force suppression control state (fourth control state) in which the steering force applied by the steering motor 410 is suppressed to a smaller value than in the normal control state.

[0041] In addition, the above-mentioned intervention condition is met when the vehicle is stopped, for example, when the front wheels 101, 102 (steered wheels) return to the neutral position, the torsion generated in the tires of the front wheels 101, 102 returns the steering wheel 310 to the neutral position, and thereafter, even if the steering wheel 310 is released, the position control of the steering motor 410 continues. In this state, although the steering wheel 310 is in the neutral position, the front wheels 101, 102 try to return away from the neutral position due to the reverse force caused by the twisting, and the steering motor 410 continues to output a steering force to resist the reverse force, which wastes power in the steering motor 410 and may also cause the steering motor 410 to overheat. Therefore, the steering control device 500 suppresses power consumption in the steering motor 410 and temperature rise of the steering motor 410 by transitioning to a steering force suppression control state (fourth control state) in which the steering force applied by the steering motor 410 is suppressed to a smaller value than in the normal control state.

[0042] FIG. 5 illustrates a scene in which a force in the opposite direction is generated due to twisting of the tire, and even if steering wheel 310 is released, steering motor 410 continues to generate a steering force to maintain the neutral position. After the vehicle 100 is stopped with the front wheels 101, 102 steered, if the driver performs an operation to return the steering wheel 310 to the neutral position, the steering control device 500 drives and controls the steering motor 410 to return the front wheels 101, 102 to the neutral position in accordance with the steering operation.

[0043] At this time, even if the driver releases the steering wheel 310, the torsion of the tires caused by returning the front wheels 101, 102 to the neutral position generates a force in the direction of returning the tire angle to its original position, and a steering torque continues to be applied to maintain the neutral position of the wheels. Here, if the steering system is a system in which the steering wheel 310 and the front wheels 101, 102 are mechanically connected, when the driver takes his / her hands off the steering wheel 310 and stops steering, the steering wheel 310 will move back slightly, pulled by the front wheels 101, 102, due to the twisting that occurs in the tires.

[0044] In contrast, in steer-by-wire system 200 in which steering wheel 310 and front wheels 101, 102 are mechanically separated, even if the driver releases steering wheel 310, steering wheel 310 remains in the neutral position, so that position control of steering motor 410 continues and steering torque continues to be applied. Therefore, when the steering control device 500 reaches a state in which the steering torque continues to be applied as described above, it transitions to a steering force suppression control state (fourth control state) in which the steering force applied by the steering motor 410 is suppressed to a smaller value than in the normal control state.

[0045] FIG. 6 is a flowchart showing the flow of alignment control in which the control state can be switched among five patterns from the 0th control state to the 4th control state, as explained based on FIGS. The flowchart in FIG. 6 is divided into control processing for the steering input device 300 and control processing for the turning device 400, and each control processing includes an initial processing, a positioning mode, a normal running mode, and an end mode.

[0046] When a start switch 650 such as an ignition switch IGN-SW is turned on to turn on the system, the steering control device 500 executes initial processing for each of the steering input device 300 and the turning device 400. Thereafter, the steering control device 500 shifts to the alignment mode, and transitions to any one of the above-mentioned 0th control state, 1st control state, 2nd control state, 3rd control state, and 4th control state.

[0047] As described above, the 0th control state is an initial non-control state after startup, and the 1st control state is a position control state in which the operation angle θ of the steering wheel 310 is changed to an operation angle θ corresponding to the steering angle δ of the front wheels 101, 102 by driving control of the reaction force motor 330. The second control state is a state in which normal control of reaction force motor 330 and steering motor 410 is carried out, and transition is made from the first control state when deviation amount AD becomes smaller than the allowable amount and alignment is completed.

[0048] Furthermore, when vehicle 100 starts moving from the 0th control state or the 1st control state, it transitions to the 3rd control state, cancels the alignment, and starts torque control of reaction force motor 330 and position control of steering motor 410. Furthermore, in the fourth control state, when vehicle 100 is stopped, steering wheel 310 is not operated, and the output torque (steering force) of steering motor 410 is greater than a predetermined value, the steering force applied by steering motor 410 is reduced to a value smaller than that in the normal control state.

[0049] Furthermore, in the alignment mode, the steering control device 500 activates the warning device 640, for example, turns on the warning lamp, in the first control state. Then, the steering control device 500 stops the operation of the warning device 640 when the mode is changed to the normal driving mode. Thereafter, when the start switch 650 such as the ignition switch IGN-SW is turned off, the steering control device 500 transitions to a termination mode, performs a predetermined termination process, and then shuts off.

[0050] FIG. 7 is a control block diagram of the steering control device 500 that switches from the 0th control state to the 4th control state described above. Here, the control block of the steering control device 500 is divided into a control system 520 for the steering input device 300 and a control system 530 for the turning device 400.

[0051] The control system 520 of the steering input device 300 has a reaction torque command calculation unit 521 and a control selector unit 522 , and controls the reaction torque generated by the reaction motor 330 of the steering input device 300 . Furthermore, control system 530 of steering device 400 has steering torque command calculation section 531, control selector 532 and control state transition determination section 533, and controls the steering force applied to front wheels 101, 102 by steering motor 410 of steering device 400.

[0052] Control state transition determination unit 533 acquires operation angle θ, vehicle speed VS, steering angle δ, steering torque command TP* of steering motor 410, and a gear position signal (shift lever position signal) of the automatic transmission of vehicle 100. The gear position signal includes a parking range P (parking), a drive range D (forward), and a reverse range R (reverse). Then, the control state transition judgment unit 533 judges the transition to any of the 0th to 4th control states based on the various information acquired, and outputs a signal of the judgment result to the control select unit 522 of the control system 520 of the steering input device 300 and the control select unit 532 of the control system 530 of the steering device 400.

[0053] Here, the control state transition determination unit 533 determines whether or not all of the following three intervention conditions are met as transition conditions to the fourth control state (in other words, power saving control intervention conditions). First intervention condition: P range or stopped time (vehicle speed VS=0) continues for a predetermined time or longer. Second intervention condition: The steering wheel 310 is not operated. Third intervention condition: The steering torque command TP* is equal to or greater than a predetermined value.

[0054] Then, if all of the above three intervention conditions are met, control state transition determination unit 533 determines a transition to the fourth control state (steering force suppression control state) and outputs a transition command to the fourth control state to control selector units 522, 532. When control selector 532 is instructed to transition to the fourth control state (steering force suppression control state), it carries out a correction process to reduce steering torque command TP* calculated in steering torque command calculation section 531 in accordance with deviation amount AD, and supplies steering torque command TP* after the correction process to steering motor 410.

[0055] The first intervention condition is that the first physical quantity related to the running state of the vehicle 100, such as the shift position or the vehicle speed VS, indicates that the running state of the vehicle 100 is stopped. In addition, the second intervention condition is that the steering torque, which is a second physical quantity related to the operation state of the steering wheel 310 (steering input member), indicates that the operation state of the steering wheel 310 is not being operated.

[0056] The determination of whether the steering wheel 310 is being operated is carried out, for example, as follows. If the steering input device 300 is equipped with a steering torque sensor that detects the steering torque of the steering wheel 310, the control state transition determination unit 533 can determine whether the steering torque detected by the steering torque sensor is greater than a threshold value, thereby determining whether the steering wheel 310 is being operated. Furthermore, if the steering input device 300 does not have a steering torque sensor that detects the steering torque of the steering wheel 310, the control state transition determination unit 533 can determine whether the steering wheel 310 is being operated by estimating the steering torque, for example, from the output shaft angle of the reaction motor 330 and determining whether the estimated steering torque is greater than a threshold value.

[0057] Furthermore, the third intervention condition is that the steering torque command TP*, which is a third physical quantity related to the output of the steering motor 410 (second actuator), indicates that the output value to the steering motor 410 is greater than or equal to a predetermined value. Then, when all of the first intervention condition, second intervention condition and third intervention condition are met, control selector 532 acquires a first target control amount (such as a steering torque command TP* after reduction correction) that results in a steering force suppression control state that suppresses the steering force applied by steering motor 410 to front wheels 101, 102, and outputs a signal corresponding to the first target control amount to steering motor 410.

[0058] According to the correction process for reducing the steering torque command TP* (transition to the steering force suppression control state), when the driver is not operating the steering wheel 310 while the vehicle 100 is stopped and the deviation between the steering wheel 310 and the steering angle δ is not eliminated by the application of steering force by the steering motor 410, the steering torque command TP* given to the steering motor 410 is suppressed to be smaller than the steering torque command TP* determined in accordance with the deviation amount AD. Therefore, in a situation where deviation amount AD cannot be reduced, steering motor 410 is prevented from wasting a lot of power, and the load on steering motor 410 is reduced, thereby preventing steering motor 410 from generating heat.

[0059] Furthermore, if any one of the following three exit conditions is met, control state transition determination unit 533 determines to exit the fourth control state (steering force suppression control state), that is, to stop the correction process to reduce the steering torque command TP*, and outputs an exit command from the fourth control state to control selector units 522, 532. First condition for disengaging: The gear is shifted from P range to D range or R range. Second departure condition: The steering wheel 310 is being operated. Third condition for leaving: Vehicle speed is present (wheels start moving).

[0060] When instructed to leave the fourth control state (steering force suppression control state), control selector 532 cancels the correction process of reducing steering torque command TP* calculated in steering torque command calculation section 531 according to deviation amount AD, and supplies steering torque command TP* calculated in accordance with deviation amount AD to steering motor 410. The first and third exit conditions are such that the first physical quantity related to the running state of the vehicle 100, such as the shift position or the vehicle speed VS, indicates that the running state of the vehicle 100 is capable of running or is running. In addition, the second release condition is that the steering torque, which is a second physical quantity related to the operation state of the steering wheel 310 (steering input member), indicates that the operation state of the steering wheel 310 is being operated.

[0061] In other words, the control state transition judgment unit 533 judges a request to exit the fourth control state (steering force suppression control state) when the vehicle 100 is able to travel or has actually started moving, and also judges a request to exit the fourth control state (steering force suppression control state) when the driver operates the steering wheel 310. Then, when vehicle 100 starts to travel (when the wheels start to move), control selector 532 outputs a steering torque command TP* (third target control amount) that controls steering motor 410 so that the steering angle δ corresponds to operating angle θ, which is a fourth physical quantity related to the amount of operation of steering wheel 310 (steering input member); in other words, outputs the steering torque command TP* (second target control amount) before the steering force suppression control state (before the reduction correction process is performed).

[0062] When returning steering torque command TP* to a normal value corresponding to the amount of deviation based on the satisfaction of the release condition, control selector 532 gradually brings steering torque command TP* from the reduced steering torque command TP* in the fourth control state closer to steering torque command TP* determined in accordance with deviation amount AD. Furthermore, when the third release condition is met and release is performed, control selector 532 can adjust the rate of gradual increase of steering torque command TP* in accordance with vehicle speed VS, and preferably makes the rate of gradual increase of steering torque command TP* faster the higher vehicle speed VS (the larger the physical quantity related to vehicle speed). In other words, if the gradual increase rate of steering torque command TP* is slow, it will take a while for steering angle δ to converge to a value corresponding to operating angle θ of steering wheel 310, impairing operability for the driver, and since a faster steering response is desired the higher the vehicle speed, the operating speed of steering motor 410 is made faster the higher the vehicle speed.

[0063] The technical ideas explained in the above embodiments can be used in appropriate combinations as long as no contradiction occurs. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical idea and teachings of the present invention.

[0064] The trigger for turning on the steer-by-wire system 200 is not limited to turning on the activation switch, but may be, for example, detection of entry into a vehicle, unlocking of doors, or the like. Steer-by-wire system 200 may also include a backup mechanism that can mechanically couple steering wheel 310 and front wheels 101, 102 with a clutch or the like.

[0065] Furthermore, the steering control device 500 can use a signal of the accelerator operation amount, a signal of the release / activation of the parking brake, and the like to determine whether the vehicle 100 should run or stop. Moreover, the steering control device 500 can be provided integrally with the steering input device 300 or the turning device 400.

[0066] Furthermore, in determining whether the steering wheel 310 is being operated, the gripping state of the steering wheel 310 can be detected as the operating state. The grip state of the steering wheel 310 can be detected, for example, using a grip detection sensor that detects whether or not the steering wheel is being gripped based on the capacitance between the steering wheel and the person measured by a sensor electrode placed on the steering wheel 310. [Explanation of symbols]

[0067] 100...vehicle, 101, 102...front wheels (steered wheels), 200...steer-by-wire system, 300...steering input device, 310...steering wheel (steering input member), 330...reaction motor (first actuator), 400...steering device, 410...steering motor (second actuator), 500...steering control device, 510...MCU (control unit)

Claims

1. a steering input device having a first actuator to which a steering operation by a driver is input via a steering input member and which applies torque to the steering input member; a steering device having a second actuator that is mechanically separated from the steering input device and applies a steering force to wheels of the vehicle, A steering control device that outputs control signals to the first actuator and the second actuator, acquiring a first physical quantity related to a traveling state of the vehicle, a second physical quantity related to an operation state of the steering input member, and a third physical quantity related to an output of the second actuator; When the first physical value indicates that the running state of the vehicle is stopped, the second physical value indicates that the operation state of the steering input member is not operated, and the third physical value indicates that the output value of the second actuator is equal to or greater than a predetermined value, obtaining a first target control amount for achieving a steering force suppression control state in which the second actuator suppresses the steering force applied to the wheels; outputting a signal corresponding to the first target control amount; Steering control device.

2. The steering control device according to claim 1, In the steering force suppression control state, When the first physical value indicates that the vehicle is in a travelable state, or when the second physical value indicates that the steering input member is in an operated state, obtain a second target control amount that sets the steering force applied to the wheels by the second actuator to the steering force before the steering force suppression control state; outputting a signal corresponding to the second target control amount; Steering control device.

3. The steering control device according to claim 1, The steering control device includes: further acquiring a fourth physical quantity related to an operation amount of the steering input member; In the steering force suppression control state, When the first physical quantity indicates that the running state of the vehicle is running, obtaining a third target control amount for controlling the second actuator so that the steering angle of the wheel corresponds to the fourth physical amount; outputting a signal corresponding to the third target control amount; Steering control device.

4. The steering control device according to claim 3, the first physical quantity is a physical quantity related to a vehicle speed of the vehicle, the actuation speed of the second actuator is increased as the physical quantity related to the vehicle speed increases; Steering control device.

5. a steering input device having a first actuator to which a steering operation by a driver is input via a steering input member and which applies torque to the steering input member; a steering device having a second actuator mechanically separated from the steering input device and applying a steering force to wheels of a vehicle; A steering control method executed by a control unit provided in the vehicle equipped with a steer-by-wire system having the following: acquiring a first physical quantity related to a traveling state of the vehicle, a second physical quantity related to an operation state of the steering input member, and a third physical quantity related to an output of the second actuator; When the first physical value indicates that the running state of the vehicle is stopped, the second physical value indicates that the operation state of the steering input member is not operated, and the third physical value indicates that the output value of the second actuator is equal to or greater than a predetermined value, obtaining a first target control amount for achieving a steering force suppression control state in which the second actuator suppresses the steering force applied to the wheels; outputting a signal corresponding to the first target control amount to the second actuator; Steering control method.

6. A steer-by-wire system mounted on a vehicle, comprising: a steering input device having a first actuator to which a steering operation by a driver is input via a steering input member and which applies torque to the steering input member; a steering device having a second actuator mechanically separated from the steering input device and applying a steering force to wheels of the vehicle; a control unit that outputs control signals to the first actuator and the second actuator, The control unit acquiring a first physical quantity related to a traveling state of the vehicle, a second physical quantity related to an operation state of the steering input member, and a third physical quantity related to an output of the second actuator; When the first physical value indicates that the running state of the vehicle is stopped, the second physical value indicates that the operation state of the steering input member is not operated, and the third physical value indicates that the output value of the second actuator is equal to or greater than a predetermined value, obtaining a first target control amount for achieving a steering force suppression control state in which the second actuator suppresses the steering force applied to the wheels; outputting a signal corresponding to the first target control amount; Steer-by-wire system.

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