Steering control device and reference value adjustment method

Abstract

To provide a steering control device and a reference value adjustment method that can effectively suppress a reduction of the effect of feedback-controlling a control angle.SOLUTION: A steering control device is intended to control a steering device including a turning part. The steering control device includes a turning side control unit in which a reference value θsd that is a value associated with a mechanical state of the turning part where turning wheels show a straight advancing state and which controls operation of the turning part. The turning side control unit executes control angle calculation processing of calculating a pinion angle θp as an integration angle that is an absolute angle with respect to the reference value θsd, angle feedback processing of feedback-controlling the pinion angle θp, and reference value adjustment processing of adjusting the reference value θsd on condition that it is in a factory mode. The reference value adjustment processing includes processing of adjusting the reference value θsd so as to minimize a deviation between the pinion angle θp and zero value when the pinion angle θp deviates from the zero value in the straight advancing state of the turning wheels.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a steering control device and a reference value adjustment method. [Background technology]

[0002] For example, a steering device described in Patent Document 1 has been proposed as a steering device to be mounted on a vehicle. The steering device described in Patent Document 1 is a so-called steer-by-wire type steering device in which the power transmission path between the steering wheel of the vehicle and the steered wheels of the vehicle is separated. The steering device described in Patent Document 1 includes a steering unit and a turning unit. The steering unit includes a steering-side actuator that operates to apply a steering reaction force to the steering wheel. The turning unit includes a turning-side actuator that operates to steer the steered wheels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-142596 Summary of the Invention [Problem to be solved by the invention]

[0004] In the steering device described in Patent Document 1, when controlling the operation of the steering unit, for example, feedback control is performed using a steering response angle as a control angle to steer the steered wheels to achieve a target steering state. The steering response angle is angle information indicating the steering state of the steered wheels and is specified as an absolute angle relative to a predetermined reference value. The reference value is a value associated with a neutral position, which is the mechanical state of the steered unit when the steered wheels are in a straight-ahead state. The reference value is set, for example, during assembly of the steering unit in a factory. However, during assembly of the steering unit, the reference value may be set as a value that deviates from the neutral position indicating the straight-ahead state of the steered wheels. In this case, the steering response angle deviates from the value indicating the straight-ahead state even when the steered wheels are in a straight-ahead state. This reduces the effectiveness of feedback control of the steering response angle. This problem is not limited to steer-by-wire steering devices, but can similarly occur in any steering device that feedback-controls angle information indicating the steered state of the steered wheels as a control angle. [Means for solving the problem]

[0005] A steering control device that solves the above problem controls a steering device including a steering unit that operates to steer the steered wheels of a vehicle. The steering control device stores a reference value that is a value associated with the mechanical state of the steering unit that indicates a straight-ahead state, which is the steering state of the steered wheels when the vehicle travels straight, and includes a control unit that controls the operation of the steering unit. The control unit is configured to execute a control angle calculation process that calculates a control angle as an absolute angle relative to the reference value, which is angle information that indicates the actual steering state of the steered wheels; an angle feedback process that feedback-controls the control angle to steer the steered wheels to achieve a target steering state; and a reference value adjustment process that adjusts the stored reference value on the condition that the vehicle is in a diagnostic state that diagnoses an abnormal state. The reference value adjustment process includes a process that, when the control angle deviates from a value that indicates the straight-ahead state in the straight-ahead state, adjusts the reference value so as to reduce the deviation between the control angle and the value that indicates the straight-ahead state.

[0006] A reference value adjustment method that solves the above problem adjusts a reference value, which is information stored in a control unit of a steering control device that controls a steering device including a steering unit that operates to steer the steered wheels of a vehicle, and is a value associated with a mechanical state of the steered unit that indicates a straight-ahead state, which is a steered state of the steered wheels when the vehicle travels straight. The reference value is used when the control unit calculates a control angle, which is angle information that indicates the actual steered state of the steered wheels as an absolute angle with respect to the reference value. The control angle is used as a control amount when the control unit performs feedback control to steer the steered wheels to achieve a target steering state when controlling the operation of the steering unit. The reference value adjustment method includes a diagnostic state setting step of setting a diagnostic state that diagnoses an abnormal state of the vehicle through operation of a diagnostic tool connected externally to the vehicle, and a reference value adjustment step of adjusting the reference value stored in the control unit under the condition that the diagnostic state is being set. The reference value adjustment step includes a step of adjusting the reference value through operation of the diagnostic tool when the control angle deviates from a value indicating the straight-line driving state in the straight-line driving state so that the deviation between the control angle and the value indicating the straight-line driving state becomes smaller.

[0007] According to the above configuration and method, for example, when the reference value deviates from a value associated with the mechanical state of the steering unit, which indicates the straight-ahead state of the steered wheels, due to assembly work of the steering unit, the reference value can be adjusted through a reference value adjustment process. This reference value adjustment process is performed when the vehicle is in a diagnostic state. The vehicle diagnostic state corresponds to, for example, a situation in which a vehicle user is not expected to be in the vehicle and drive, such as when vehicle maintenance work is being performed. During maintenance work, even if the adjustment of the reference value affects the feedback control of the control angle, it is not a situation that causes inconvenience to the vehicle user. As a result, when the control angle deviates from a value indicating the straight-ahead state when the steered wheels are in a straight-ahead state, the deviation of the control angle can be reduced without causing inconvenience to the vehicle user. Therefore, a reduction in the effectiveness of feedback control of the control angle can be effectively suppressed.

[0008] In the above steering control device, it is preferable that the reference value adjustment process includes a process of adjusting the reference value so as to reflect an offset value obtained based on the control angle in the straight traveling state.

[0009] According to the above configuration, the offset value can be obtained simply by creating a straight-ahead state of the steered wheels, which is effective in simplifying the reference value adjustment process. In the above steering control device, it is preferable that the reference value adjustment process includes a process of setting an upper limit for the absolute value of the offset value.

[0010] With the above configuration, it is possible to prevent the absolute value of the offset value from becoming large, which results in a situation where the range in which the steered wheels can be steered differs greatly between the left and right wheels. Therefore, it is possible to adjust the reference value so that the user of the vehicle does not feel uncomfortable when driving.

[0011] In the above steering control device, the control unit is configured to execute the reference value adjustment process while the vehicle is traveling, provided that the vehicle is in the diagnostic state, and it is preferable that the reference value adjustment process includes a process of obtaining, as the offset value, a value obtained by accumulating unit quantities that are smaller than the value by which the control angle deviates from the value indicating the straight-line driving state in the straight-line driving state.

[0012] According to the above configuration, for example, a maintenance worker can adjust the reference value while the vehicle is running. In this case, since the vehicle can actually be run, when the steered wheels are running straight, the deviation of the control angle from the value indicating the straight-ahead state can be accurately reflected in the adjustment of the reference value. Furthermore, since the accumulated value of the unit amount is obtained as the offset value, the reference value can be adjusted in stages. This is effective in ensuring the safety of the maintenance worker when adjusting the reference value while the vehicle is running.

[0013] In the above steering control device, the control unit is configured to execute the reference value adjustment process while the vehicle is stopped, provided that the vehicle is in the diagnostic state, and it is preferable that the reference value adjustment process includes a process of obtaining the control angle in the straight-ahead state as the offset value.

[0014] According to the above configuration, for example, a maintenance worker can adjust the reference value while the vehicle is stopped. In this case, since the vehicle is stopped, the reference value can be adjusted without considering the effect of feedback control of the control angle that accompanies the adjustment of the reference value. This is effective in ensuring the safety of the maintenance worker and achieving highly efficient work when adjusting the reference value. [Effects of the Invention]

[0015] According to the present invention, it is possible to effectively suppress a decrease in the effect of feedback control of the control angle. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a steer-by-wire steering device. [Figure 2] FIG. 2 is a block diagram showing the functions of a steering control device. [Figure 3] 4 is a flowchart illustrating a reference value adjustment process according to the first embodiment. [Figure 4] 4 is a flowchart illustrating a reference value adjustment method according to the first embodiment. [Figure 5] 10A and 10B are diagrams illustrating a state in which the reference value deviates from the rack neutral position, which indicates a straight traveling state of the steered wheels. [Figure 6] 5A to 5C are diagrams illustrating how a reference value is adjusted in the first embodiment. [Figure 7] 10 is a flowchart illustrating a reference value adjustment process according to the second embodiment. [Figure 8] 10 is a flowchart illustrating a reference value adjustment method according to the second embodiment. [Figure 9]10A and 10B are diagrams illustrating how a reference value is adjusted in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] First Embodiment The steering control device 1 according to the first embodiment will be described below. As shown in FIG. 1, steering control device 1 controls steering device 2. Steering device 2 is configured as a steer-by-wire type steering device for a vehicle. Steering device 2 includes a steering unit 4 and a turning unit 6. Steering unit 4 is steered by a driver via a steering wheel 3 of the vehicle. Steering unit 6 steers left and right steerable wheels 5 of the vehicle in accordance with steering input to steering unit 4 by the driver. Note that steering device 2 of this embodiment has a structure in which the power transmission paths between steering unit 4 and turning unit 6 are mechanically separated at all times. In other words, the power transmission paths between steering side actuator 12 (described later) and turning side actuator 31 (described later) are mechanically separated at all times.

[0018] The steering unit 4 includes a steering shaft 11 and a steering-side actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering-side actuator 12 includes a steering-side motor 13, which is a drive source, and a steering-side reduction mechanism 14. The steering-side motor 13 is a reaction motor that applies a steering reaction force, which is a force that resists steering, to the steering wheel 3 via the steering shaft 11. The steering-side motor 13 is connected to the steering shaft 11 via the steering-side reduction mechanism 14, which is made up of, for example, a worm and wheel. For example, a three-phase brushless motor is used as the steering-side motor 13 in this embodiment.

[0019] The steered unit 6 includes a pinion shaft 21, a rack shaft 22 serving as a steered shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected at a predetermined cross angle. A rack-and-pinion mechanism 24 is formed by meshing pinion teeth 21a formed on the pinion shaft 21 with rack teeth 22a formed on the rack shaft 22. In other words, the pinion shaft 21 corresponds to a rotation axis that can be converted into a steering angle θi, which is the steering position of the steered wheels 5. The rack housing 23 accommodates the rack-and-pinion mechanism 24. One end of the pinion shaft 21 opposite the end connected to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the rack shaft 22 via rack ends 25 formed as ball joints. The ends of the tie rods 26 are connected to knuckles (not shown) to which the left and right steered wheels 5 are attached.

[0020] The steering unit 6 includes a steering-side actuator 31. The steering-side actuator 31 includes a steering-side motor 32, which is a drive source, a transmission mechanism 33, and a conversion mechanism 34. The steering-side motor 32 applies a steering force to the rack shaft 22 to turn the steered wheels 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering-side motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering-side motor 32 into reciprocating motion of the rack shaft 22 via the conversion mechanism 34, which is, for example, a ball screw mechanism. A three-phase brushless motor, for example, is used as the steering-side motor 32 in this embodiment.

[0021] In the steering device 2 configured as described above, the steering angle θi of the steered wheels 5 is changed by applying a motor torque as a steering force from the steering-side actuator 31 to the rack shaft 22 in response to steering by the driver. At this time, a steering reaction force that resists the steering by the driver is applied to the steering wheel 3 from the steering-side actuator 12. In other words, in the steering device 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is the motor torque applied from the steering-side actuator 12.

[0022] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 inside the rack housing 23. In other words, the rack shaft 22 is supported movably along its axial direction and is pressed toward the pinion shaft 21 by a support mechanism (not shown) provided in the steering device 2. In this way, the rack shaft 22 is supported inside the rack housing 23. However, another support mechanism may be provided to support the rack shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0023] <Electrical configuration of steering device 2> 1, the steering-side motor 13 and the turning-side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of the steering-side motor 13 and the turning-side motor 32.

[0024] Detection results of various sensors are input to the steering control device 1. Various sensors are connected to the steering control device 1. The various sensors include, for example, a torque sensor 41, a steering side rotation angle sensor 42, a turning side rotation angle sensor 43, and a vehicle speed sensor 44.

[0025] The torque sensor 41 detects the steering torque Th, which is a value indicating the torque applied to the steering shaft 11 by the driver's steering. The steering-side rotation angle sensor 42 detects the rotation angle θa, which is the angle of the rotation shaft of the steering-side motor 13, within a range of 360 degrees. The turning-side rotation angle sensor 43 detects the rotation angle θb, which is the angle of the rotation shaft of the turning-side motor 32, within a range of 360 degrees. The vehicle speed sensor 44 detects the vehicle speed V, which is the traveling speed of the vehicle.

[0026] Specifically, the torque sensor 41 is provided on the steering shaft 11 at a portion closer to the steering wheel 3 than the steering-side reduction gear mechanism 14. The torque sensor 41 detects the steering torque Th based on the twist of a torsion bar 41a provided midway along the steering shaft 11. The steering torque Th is detected as a positive value when the vehicle is steered to the right, and as a negative value when the vehicle is steered to the left, for example.

[0027] Furthermore, the steering-side rotation angle sensor 42 is provided in the steering-side motor 13. The rotation angle θa of the steering-side motor 13 is used to calculate the steering angle θh. The steering-side motor 13 and the steering shaft 11 are linked via the steering-side reduction mechanism 14. For this reason, there is a correlation between the rotation angle θa of the steering-side motor 13 and the rotation angle of the steering shaft 11, and ultimately the steering angle θh, which is the rotation angle indicating the rotational position of the steering wheel 3. Therefore, the steering angle θh can be obtained based on the rotation angle θa of the steering-side motor 13. Note that the rotation angle θa is detected as a positive value when the vehicle is steered to the right, and as a negative value when the vehicle is steered to the left, for example.

[0028] Furthermore, the turning-side rotation angle sensor 43 is provided in the turning-side motor 32. The rotation angle θb of the turning-side motor 32 is used to calculate the pinion angle θp. The turning-side motor 32 and the pinion shaft 21 are linked via the transmission mechanism 33, the conversion mechanism 34, and the rack-and-pinion mechanism 24. Therefore, there is a correlation between the rotation angle θb of the turning-side motor 32 and the pinion angle θp, which is the rotation angle of the pinion shaft 21. Therefore, the pinion angle θp can be obtained based on the rotation angle θb of the turning-side motor 32. Furthermore, the pinion shaft 21 is meshed with the rack shaft 22. Therefore, there is also a correlation between the pinion angle θp and the amount of movement of the rack shaft 22. In other words, the pinion angle θp is angle information that indicates the steered state of the steered wheels 5, and is a value that reflects the turning angle θi, which is the steered position of the steered wheels 5. The rotation angle θb is detected as a positive value when the vehicle is steered to the right, and as a negative value when the vehicle is steered to the left, for example.

[0029] A diagnostic tool 45 can be connected to the steering control device 1. The diagnostic tool 45 is used, for example, in a repair shop where vehicles are repaired, such as a dealer's shop. The diagnostic tool 45 is connected to the vehicle from outside. The steering control device 1 of this embodiment has a connector 45a. The diagnostic tool 45 is connected to the vehicle from outside via the connector 45a of the steering control device 1. Note that the connector 45a may be provided in a control device mounted on the vehicle separately from the steering control device 1, or may be mounted on the vehicle as a dedicated connector. The diagnostic tool 45 is a tool for diagnosing abnormal conditions in the vehicle.

[0030] The diagnostic tool 45, while connected to the steering control device 1, instructs the vehicle, i.e., the steering control device 1, to be set to factory mode, which is a diagnostic state, through operation by a maintenance worker. While the factory mode is set, the vehicle is in a situation where it is not expected that a user will be in the vehicle and driving, etc., and maintenance work is being carried out on the vehicle. While the factory mode is set, the worker can use the diagnostic tool 45 to check the diagnosis results of an abnormal state for the vehicle, i.e., the steering control device 1. Then, the worker can take measures according to the diagnosis results by operating the diagnostic tool 45.

[0031] <Functions of the steering control device 1> The steering control device 1 is equipped with a central processing unit (CPU) and memory (not shown). The steering control device 1 performs various processes by having the CPU execute programs stored in the memory at predetermined calculation intervals. The CPU and memory constitute a microcomputer, which is a processing circuit. The memory includes computer-readable media such as RAM (Random Access Memory) and ROM (Read Only Memory). However, realizing various processes by software is one example. The processing circuit of the steering control device 1 may be configured to realize at least a part of the processes by hardware circuits such as logic circuits.

[0032] Figure 2 shows part of the processing executed by the steering control device 1. The processing shown in Figure 2 is part of the processing realized by the CPU executing a program stored in memory, and is described for each type of processing realized.

[0033] The steering control device 1 has a steering side control unit 50 and a turning side control unit 60. The steering side control unit 50 controls the power supply to the steering side motor 13. The steering side control unit 50 has a steering side current sensor 54. The steering side current sensor 54 detects an actual steering side current value Ia obtained from the current value of each phase of the steering side motor 13 flowing through a connecting wire between the steering side control unit 50 and the motor coil of each phase of the steering side motor 13. The steering side current sensor 54 acquires, as a current, the voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering side motor 13. Note that in FIG. 2, for ease of explanation, the connecting wires of each phase and the current sensors of each phase are shown collectively.

[0034] The turning side control unit 60 controls the power supply to the turning side motor 32. The turning side control unit 60 has a turning side current sensor 65. The turning side current sensor 65 detects a turning side actual current value Ib obtained from the current value of each phase of the turning side motor 32 flowing through a connecting wire between the turning side control unit 60 and the motor coil of each phase of the turning side motor 32. The turning side current sensor 65 obtains, as a current, a voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the turning side motor 32. For ease of explanation, FIG. 2 illustrates the connecting wires and current sensors of each phase together. In this embodiment, the turning side control unit 60 is an example of a control unit that controls the operation of the steering unit 6 of the steering device 2, i.e., the turning side actuator 31.

[0035] <Steering-side control unit 50> 2, steering torque Th, vehicle speed V, rotation angle θa, turning side actual current value Ib, and a turning conversion angle θp_s, which will be described later, are input to the steering side control unit 50. The steering side control unit 50 controls the power supply to the steering side motor 13 based on the steering torque Th, vehicle speed V, rotation angle θa, turning side actual current value Ib, and turning conversion angle θp_s. The turning conversion angle θp_s is calculated based on the pinion angle θp.

[0036] The steering-side control unit 50 includes a steering angle calculation unit 51 , a target reaction torque calculation unit 52 , and an energization control unit 53 . The rotation angle θa is input to the steering angle calculation unit 51. The steering angle calculation unit 51 converts the rotation angle θa into an integrated angle including a range exceeding 360°, for example, by counting the number of rotations of the steering-side motor 13 from a steering neutral position, which is the position of the steering wheel 3 when the vehicle is traveling straight. The steering angle calculation unit 51 calculates the steering angle θh by multiplying the integrated angle obtained by conversion by a conversion coefficient based on the rotational speed ratio of the steering-side reduction gear mechanism 14. In other words, the steering angle calculation unit 51 calculates the steering angle θh as an absolute angle with respect to the steering neutral position. The steering angle θh obtained in this way is output to the target reaction force torque calculation unit 52 and the turning-side control unit 60.

[0037] Steering torque Th, vehicle speed V, steering side actual current value Ib, steering conversion angle θp_s (described later), and steering angle θh are input to target reaction torque calculation unit 52. Target reaction torque calculation unit 52 calculates target reaction torque command value Ts* based on steering torque Th, vehicle speed V, steering side actual current value Ib, steering conversion angle θp_s, and steering angle θh. Target reaction torque command value Ts* is a reaction force control amount that serves as a target for the steering reaction force of steering wheel 3 to be generated via steering side motor 13. Target reaction torque command value Ts* obtained in this manner is output to current supply control unit 53.

[0038] The current supply control unit 53 receives inputs of the target reaction torque command value Ts*, the rotational angle θa, and the steering side actual current value Ia. The current supply control unit 53 calculates a current command value Ia* for the steering side motor 13 based on the target reaction torque command value Ts*. The current supply control unit 53 then calculates the deviation between the current command value Ia* and a current value on the dq coordinates obtained by converting the steering side actual current value Ia detected by the steering side current sensor 54 based on the rotational angle θa, and controls the power supply to the steering side motor 13 to eliminate the deviation. This causes the steering side motor 13 to generate torque corresponding to the target reaction torque command value Ts*. In other words, it is possible to provide the driver with an appropriate sense of response corresponding to the road reaction force.

[0039] <Steering-side control unit 60> 2, the vehicle speed V, the rotation angle θb, and the steering angle θh are input to the turning-side control unit 60. The turning-side control unit 60 controls the power supply to the turning-side motor 32 based on the vehicle speed V, the rotation angle θb, and the steering angle θh.

[0040] The steering side control unit 60 has a pinion angle calculation unit 61, a steering angle ratio variable control unit 62, an angle feedback control unit ("pinion angle F / B control unit" in the drawing) 63, and an energization control unit 64.

[0041] The rotation angle θb is input to the pinion angle calculation unit 61. The pinion angle calculation unit 61 converts the rotation angle θb into an integrated angle that includes a range exceeding 360°, for example, by counting the number of rotations of the steered-side motor 32 from a rack neutral position, which is the position of the rack shaft 22 when the vehicle is traveling straight. The pinion angle calculation unit 61 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, by multiplying the integrated angle obtained by the conversion by a conversion coefficient that is based on the rotation speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack-and-pinion mechanism 24. In other words, the pinion angle calculation unit 61 calculates the pinion angle θp as an absolute angle with respect to the rack neutral position. The pinion angle θp obtained in this manner is output to the steering angle ratio variable control unit 62 and the angle feedback control unit 63.

[0042] Vehicle speed V, steering angle θh, and pinion angle θp are input to steering angle ratio variable control unit 62. Steering angle ratio variable control unit 62 calculates target pinion angle θp* based on steering angle θh. Target pinion angle θp* is the pinion angle θp obtained as a result of steering the steered wheels 5, i.e., a control amount that is a target for the steering state of the steered wheels 5. Target pinion angle θp* is calculated as an angle converted from the steering angle θh into a scale of pinion angle θp that takes into account the steering angle ratio, which is the ratio between the steering angle θh and the pinion angle θp. Steering angle ratio variable control unit 62 calculates steering conversion angle θp_s based on the pinion angle θp. Steering conversion angle θp_s is calculated as an angle converted from the pinion angle θp into a scale of steering angle θh that takes into account the steering angle ratio.

[0043] Steering angle ratio variable control unit 62 changes the steering angle ratio in accordance with vehicle speed V. For example, steering angle ratio variable control unit 62 changes the steering angle ratio so that the change in pinion angle θp relative to the change in steering angle θh is greater when vehicle speed V is low than when vehicle speed V is high. That is, in calculating target pinion angle θp*, a conversion calculation is performed to ensure that the positional relationship between target pinion angle θp* and steering angle θh satisfies a predetermined correspondence relationship. In calculating steering conversion angle θp_s, an inverse conversion calculation is performed, for example, using the reciprocal of the value used in the conversion calculation, to ensure that the positional relationship between target pinion angle θp and pinion angle θp satisfies a predetermined correspondence relationship. Target pinion angle θp* obtained in this way is output to angle feedback control unit 63. Furthermore, steering conversion angle θp_s is output to steering-side control unit 50, i.e., target reaction force torque calculation unit 52.

[0044] Target pinion angle θp* and pinion angle θp are input to angle feedback control unit 63. Angle feedback control unit 63 calculates a steering force command value Tp* as a control amount that becomes a target for the steering force through angle feedback processing that feedback controls pinion angle θp so that pinion angle θp follows target pinion angle θp*. The steering force command value Tp* obtained in this manner is output to current supply control unit 64. In the present embodiment, pinion angle θp is an example of a control angle.

[0045] The turning force command value Tp*, the rotation angle θb, and the turning side actual current value Ib are input to the energization control unit 64. The energization control unit 64 calculates a current command value Ib* for the turning side motor 32 based on the turning force command value Tp*. The energization control unit 64 then determines the deviation between the current command value Ib* and a current value on the dq coordinate obtained by converting the turning side actual current value Ib detected by the turning side current sensor 65 based on the rotation angle θb, and controls the power supply to the turning side motor 32 to eliminate this deviation. As a result, the turning side motor 32 rotates by an angle corresponding to the turning force command value Tp*. In other words, the turning side control unit 60 controls the operation of the steering device 2, i.e., the steering unit 6, so that the positional relationship between the steering angle θh and the pinion angle θp, i.e., the positional relationship between the steering angle θh and the turning angle θi, becomes a predetermined correspondence relationship determined according to the steering angle ratio.

[0046] <About the reference value θsd> As shown in FIG. 2, the turning-side control unit 60 has a memory unit 66. The memory unit 66 is a predetermined storage area in the memory of the steering control device 1. The memory unit 66 stores a reference value θsd, which is a value associated with the mechanical state of the turning unit 6 that indicates a straight-ahead state, which is the steered state of the steered wheels 5 when the vehicle travels straight. In other words, the reference value θsd is a value that indicates the rack neutral position. As a result, the pinion angle calculation unit 61 executes a control angle calculation process that calculates the pinion angle θp as an absolute angle relative to the reference value θsd.

[0047] The reference value θsd is set, for example, during assembly of the turning unit 6 at a factory or the like. During assembly of the turning unit 6, the reference value θsd is set as a value that indicates that the pinion angle θp is zero when the steered wheels 5 are in a straight-ahead state and the rack shaft 22 is in the rack neutral position. The zero value of the pinion angle θp corresponds to the zero value where the steering angle θh, indicating the position of the steering wheel 3, is in the steering neutral position. However, due to the assembly of the turning unit 6, the reference value θsd may be set as a value that deviates from the rack neutral position. In this case, the zero value of the pinion angle θp does not correspond to the zero value where the steering angle θh, indicating the position of the steering wheel 3, is in the steering neutral position. In other words, when the turning-side control unit 60 performs feedback control of the pinion angle θp so that it becomes an angle corresponding to the steering angle θh, a situation arises in which a deviation occurs in the relationship between the position of the steering wheel 3 and the turning state of the steered wheels 5. To deal with such a situation, the steering-side control unit 60 has a function of adjusting the reference value θsd stored in the storage unit 66. Below, the reference value adjustment process for adjusting the reference value θsd will be described in detail.

[0048] <Reference value adjustment process> As shown in Fig. 3, the turning side control unit 60 executes a reference value adjustment process at each predetermined control cycle. In the reference value adjustment process, the turning side control unit 60 determines whether or not the system is in factory mode (step S10). In step S10, the turning side control unit 60 determines whether or not a mode setting command instructing the system to set the factory mode has been input via the diagnostic tool 45. When the turning side control unit 60 determines that the system is not in factory mode because a mode setting command has not been input (step S10: NO), it ends the reference value adjustment process and proceeds to other processing.

[0049] On the other hand, in step S10, if the turning side control unit 60 determines that the mode is the factory mode because a mode setting command has been input (step S10: YES), it determines whether the system of the steering device 2 including the steering control device 1 is normal (step S11). In step S11, the turning side control unit 60 determines whether the turning side control can be normally executed when power is applied to the steer-by-wire steering device 2. The normal turning side control is a control to steer the steered wheels 5 to an angle corresponding to the steering operation of the driver by reflecting the state of the steering unit 4 in the state of the turning unit 6. If the turning side control unit 60 determines that the normal turning side control cannot be normally executed (step S11: NO), it ends the reference value adjustment process and proceeds to another process. Note that if the turning side control unit 60 determines that the normal turning side control cannot be normally executed, it outputs information indicating this to the diagnostic tool 45.

[0050] On the other hand, in step S11, if the turning side control unit 60 determines that normal turning side control can be executed normally (step S11: YES), it determines whether or not an offset command is input via the diagnostic tool 45 (step S12). If an offset command is not input (step S12: NO), the turning side control unit 60 ends the reference value adjustment process and proceeds to another process.

[0051] On the other hand, in step S12, if an offset command is input (step S12: YES), the turning side control unit 60 updates the offset value θofs (step S13). In step S13, the turning side control unit 60 updates the offset value θofs so as to reflect the left adjustment amount θl or right adjustment amount θr instructed in the offset command. The offset value θofs is a value for adjusting the reference value θsd. The turning side control unit 60 uses a value obtained by adding or subtracting the offset value θofs from the reference value θsd stored in the memory unit 66 as the adjusted reference value θsd in calculating the pinion angle θp. The offset value θofs is set to zero as its initial value. In other words, when the offset value θofs is zero, the adjusted reference value θsd is the same as the reference value θsd stored in the memory unit 66 and set during the assembly work of the turning unit 6 at a factory, etc.

[0052] In step S13, the turning side control unit 60 increases or decreases the offset value θofs by a predetermined unit amount depending on the content of the offset command determined in step S12. For example, if the content of the offset command is a leftward adjustment amount θl, the turning side control unit 60 increases the offset value θofs by the unit amount. This means that the reference value θsd is adjusted so as to shift the offset value θofs to the rightward steering side, which is the positive direction of the rotation angle θb. On the other hand, if the content of the offset command is a rightward adjustment amount θr, the turning side control unit 60 decreases the offset value θofs by the unit amount. This means that the reference value θsd is adjusted so as to shift the offset value θofs to the leftward steering side, which is the negative direction of the rotation angle θb. For example, the unit amount is set to a value within a range that is experimentally determined to be smaller than a possible deviation from the reference value θsd.

[0053] Next, the turning side control unit 60 determines whether the absolute value of the offset value θofs after updating in step S13 is equal to or less than the threshold value θth (step S14). In step S14, the turning side control unit 60 limits the upper limit of the absolute value of the offset value θofs so that it does not become too large. For example, the threshold value θth is set to a value within a range that is experimentally determined so that the range in which the steerable wheels 5 can be turned, and the deviation of the steering range between the left and right, does not cause discomfort to the driver.

[0054] In step S14, if the absolute value of the offset value θofs after updating in step S13 is equal to or less than the threshold value θth (step S14: YES), the turning side control unit 60 ends the reference value adjustment process and proceeds to other processes. In this case, the turning side control unit 60 will use the offset value θofs after updating in step S13 for adjusting the reference value θsd thereafter.

[0055] On the other hand, in step S14, if the absolute value of the offset value θofs after updating in step S13 is greater than the threshold value θth (step S14: NO), the turning side control unit 60 limits the absolute value of the offset value θofs to the threshold value θth (step S15). If step S15 is proceeded through, the turning side control unit 60 will use the offset value θofs obtained by limiting the absolute value of the value after updating in step S13 to the threshold value θth for adjusting the reference value θsd thereafter. Thereafter, the turning side control unit 60 ends the reference value adjustment process and proceeds to other processes.

[0056] As the reference value adjustment process, the turning side control unit 60 repeatedly executes the processes of steps S10 to S15 at predetermined control cycles, and as a result, each time it determines the input of an offset command in step S12, it cumulatively reflects the left adjustment amount θl or the right adjustment amount θr. In other words, the turning side control unit 60 is configured to obtain, as the offset value θofs, a value obtained by accumulating unit amounts corresponding to the left adjustment amount θl or the right adjustment amount θr. Furthermore, the turning side control unit 60 is configured to limit the offset value θofs so as not to accumulate it endlessly, but to do so in a manner that does not cause discomfort to the driver.

[0057] <Reference value adjustment method> As shown in Fig. 4, an operator at a repair shop that repairs vehicles, such as a dealer, adjusts the reference value θsd according to the following reference value adjustment method. In the reference value adjustment method, the operator connects the diagnostic tool 45 to the vehicle, i.e., the steering control device 1 (step S100). Next, the operator sets the factory mode by operating the diagnostic tool 45 (step S101). In this case, the diagnostic tool 45 outputs a mode setting command to instruct the steering control device 1 to set the factory mode. In this embodiment, the steps S100 and S101 correspond to a diagnostic state setting step.

[0058] Next, the worker drives the vehicle with the factory mode set (step S102). In step S102, the worker drives the vehicle so that the steered wheels 5 are in a straight-ahead state. For example, if the reference value θsd is a value that deviates from the rack neutral position, when attempting to adjust the position of the steering wheel 3 so that the vehicle travels straight, the position will deviate to either the left or right steering side from the steering wheel neutral position. The amount of deviation to the steering side corresponds to the magnitude of the value by which the reference value θsd deviates from the rack neutral position.

[0059] Next, the worker outputs an offset command by operating the diagnostic tool 45 (step S103). In step S103, the worker operates the diagnostic tool 45 to output an offset command instructing a leftward adjustment amount θl or a rightward adjustment amount θr according to the position of the steering wheel 3. For example, if the position of the steering wheel 3 is deviated to the rightward steering side with respect to the steering wheel neutral position, the worker performs an operation to output an offset command instructing a leftward adjustment amount θl. This means that the reference value θsd is adjusted so as to shift the steering wheel 3 to the rightward steering side, which is the positive direction of the rotation angle θb. On the other hand, if the position of the steering wheel 3 is deviated to the leftward steering side with respect to the steering wheel neutral position, the worker performs an operation to output an offset command instructing a rightward adjustment amount θr. This means that the reference value θsd is adjusted so as to shift the steering wheel 3 to the leftward steering side, which is the negative direction of the rotation angle θb.

[0060] Then, when an offset command is input, the turning side control unit 60 updates the offset value θofs and adjusts the reference value θsd. The turning side control unit 60 performs feedback control so that the pinion angle θp obtained using the adjusted reference value θsd becomes an angle corresponding to the steering angle θh. The turning side control unit 60 controls the steering device 2 so that the positional relationship between the steering angle θh and the pinion angle θp, i.e., the steering angle θh and the turning angle θi, approaches a predetermined correspondence relationship determined in accordance with the steering angle ratio. This allows the operator to understand that when the vehicle is driven so that the steered wheels 5 are in a straight-ahead state, the amount of deviation when the position of the steering wheel 3 deviates to the right steering side from the steering wheel neutral position will be reduced.

[0061] Then, while checking the position of the steering wheel 3, the operator repeats the operation to output an offset command (step S103) so that the position approaches the neutral position of the steering wheel. Note that, as a result of repeating the operation to output the offset command, if the turning-side control unit 60 determines that the absolute value of the offset value θofs is greater than the threshold value θth (step S14: NO), the position of the steering wheel 3 does not change. In this embodiment, the steps S102 and S103 correspond to a reference value adjustment step.

[0062] Next, if the worker determines that the adjustment of the reference value θsd is complete while checking the position of the steering wheel 3, he or she ends the factory mode by operating the diagnostic tool 45 (step S104). Next, the worker removes the diagnostic tool 45 from the steering control device 1 (step S105) and ends the work of adjusting the reference value.

[0063] <How the reference value θsd is adjusted> As shown in FIG. 5, a case will be described as an example in which the reference value θsd deviates from the rack neutral position by a deviation amount D toward the right steering side due to the assembly work of the steering unit 6. In this example, when the vehicle is driven so that the steered wheels 5 are in a straight-ahead state, the value of the pinion angle θp is calculated as the deviation amount D indicating that the steered wheels 5 are facing in the direction of the dashed arrow in FIG. 5. In other words, the position of the steering wheel 3 deviates from the steering wheel neutral position by an amount corresponding to the deviation amount D toward the right steering side. Then, the reference value θsd can be adjusted through the reference value adjustment process by the steering side control unit 60 shown in FIG. 3, in addition to the reference value adjustment method by the operator shown in FIG. 4. In this case, in the reference value adjustment method, the operator repeatedly outputs an offset command instructing the left adjustment amount θl by operating the diagnostic tool 45.

[0064] As shown in Fig. 6, in the reference value adjustment process, the turning side control unit 60 cumulatively adds the offset value θofs by unit amount Dua each time an offset command specifying the left adjustment amount θl is input. For example, the offset value θofs becomes equal to the deviation amount D when the left adjustment amount θl is specified n times. The adjusted reference value θsd is adjusted so as to be deviated by the deviation amount D toward the steering side in the right direction by adding the offset value θofs corresponding to the deviation amount D. In other words, the adjusted reference value θsd becomes equal to the deviation amount D, which is the value of the pinion angle θp when the vehicle is driven so that the steered wheels 5 are in a straight-ahead state, i.e., the rack neutral position.

[0065] As a result, when the vehicle is driven so that the steered wheels 5 are in a straight-ahead state, the value of the pinion angle θp is calculated as zero, which indicates that the steered wheels 5 are pointing in the direction of the solid arrow in Fig. 5, using the reference value θsd of the adjustment degree. In other words, the position of the steering wheel 3 coincides with the neutral position of the steering wheel.

[0066] <Operation of this embodiment> According to this embodiment, when the reference value θsd deviates from the rack neutral position due to the assembly work of the steering unit 6, the turning-side control unit 60 can adjust the reference value θsd through the reference value adjustment process. This reference value adjustment process is performed on the condition that the factory mode is set. When the factory mode is set, it is a situation in which it is not expected that a vehicle user will be in the vehicle and driving, etc., and this corresponds to when vehicle maintenance work is being performed. During maintenance work, even if the adjustment of the reference value θsd affects the feedback control of the pinion angle θp, it is a situation in which the vehicle user will not be inconvenienced. As a result, when the pinion angle θp deviates from the zero value when the steered wheels 5 are traveling straight, the deviation of the pinion angle θp can be reduced so as not to cause inconvenience to the vehicle user.

[0067] <Effects of this embodiment> (1-1) In this embodiment, when the pinion angle θp deviates from the zero value while the steered wheels 5 are traveling straight, the deviation of the pinion angle θp can be reduced so as not to cause inconvenience to the vehicle user. Therefore, it is possible to effectively prevent a decrease in the effect of feedback control of the pinion angle θp.

[0068] (1-2) In this embodiment, the offset value θofs can be obtained simply by creating a straight-ahead state of the steered wheels 5. This is effective in simplifying the reference value adjustment process. (1-3) In this embodiment, the absolute value of the offset value θofs becomes large, which prevents the range in which the steered wheels 5 can be steered from deviating significantly between the left and right. Therefore, the reference value θsd can be adjusted so as not to cause discomfort to the user of the vehicle when driving.

[0069] (1-4) In this embodiment, the worker can adjust the reference value θsd while the vehicle is running. In this case, since the vehicle can actually be run, the deviation of the pinion angle θp from the zero value when the steered wheels 5 are running straight can be accurately reflected in the adjustment of the reference value θsd. In addition, since the accumulated value of the unit amounts is obtained as the offset value θofs, the reference value θsd can be adjusted in stages. This is effective in ensuring the safety of the maintenance worker when adjusting the reference value θsd while the vehicle is running.

[0070] Second Embodiment Next, a steering control device 1 according to a second embodiment will be described. For convenience of explanation, the same components as those in the first embodiment will be assigned the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

[0071] <Reference value adjustment process> As shown in Fig. 7, in the reference value adjustment process, the turning side control unit 60 determines whether or not the mode is factory mode (step S20). In step S20, the turning side control unit 60 makes the same determination as in step S10 in Fig. 3. When the turning side control unit 60 determines that the mode is not factory mode because a mode setting command has not been input (step S20: NO), it ends the reference value adjustment process and moves on to other processing.

[0072] On the other hand, in step S20, if the steering side control unit 60 determines that the mode is the factory mode because a mode setting command has been input (step S20: YES), it determines whether the system of the steering device 2 including the steering control device 1 is normal (step S21). In step S21, the turning side control unit 60 makes a determination similar to step S11 in Fig. 3. If the turning side control unit 60 determines that normal turning side control cannot be executed normally (step S21: NO), it ends the reference value adjustment process and moves on to other processes.

[0073] On the other hand, in step S21, if the turning side control unit 60 determines that normal turning side control can be executed normally (step S21: YES), it determines whether or not the vehicle is stopped (step S22). In step S22, the turning side control unit 60 determines whether or not the vehicle speed V is less than the vehicle speed threshold Vth. The vehicle speed threshold Vth is set to a value within an experimentally determined range that indicates that a speed less than the vehicle speed threshold Vth is an extremely low speed, including when the vehicle is stopped. If the turning side control unit 60 determines that the vehicle is not stopped because the vehicle speed V is equal to or greater than the vehicle speed threshold Vth (step S22: NO), it ends the reference value adjustment process and proceeds to other processes.

[0074] On the other hand, when the turning side control unit 60 determines that the vehicle is stopped because the vehicle speed V is less than the vehicle speed threshold Vth (step S22: YES), it determines whether or not an offset command has been input via the diagnostic tool 45 (step S23). When an offset command has not been input (step S23: NO), the turning side control unit 60 ends the reference value adjustment process and proceeds to another process.

[0075] On the other hand, if an offset command is input in step S23 (step S23: YES), the turning side control unit 60 sets the offset value θofs (step S24). In step S24, the turning side control unit 60, in response to the input of the offset command, sets the value of the pinion angle θp at that time as the offset value θofs. In this embodiment, the offset command is information for instructing the turning side control unit 60 to adjust the reference value θsd so that the value of the pinion angle θp at that time becomes the reference value θsd.

[0076] In the present embodiment, the offset command is input to the steering unit 6 in a state where the steering state has been adjusted so that the steered wheels 5 are in a straight-ahead state. In other words, the steered wheels 5 are in a straight-ahead state when the steering-side control unit 60 determines whether to input the offset command. In this case, if the pinion angle θp deviates from the zero value, the reference value θsd deviates from the rack neutral position by the amount of that deviation. In step S24, the steering-side control unit 60 setting the offset value θofs means adjusting the reference value θsd so that it becomes the value of the pinion angle θp at that time.

[0077] Next, the turning side control unit 60 determines whether the absolute value of the offset value θofs after setting in step S24 is equal to or less than the threshold value θth (step S25). In step S25, the turning side control unit 60 makes the same determination as in step S14 of FIG. 3. If the absolute value of the offset value θofs after setting in step S24 is equal to or less than the threshold value θth (step S25: YES), the turning side control unit 60 ends the reference value adjustment process and moves on to other processes. In this case, the turning side control unit 60 will use the offset value θofs after setting in step S24 for adjusting the reference value θsd thereafter.

[0078] On the other hand, in step S25, if the absolute value of the offset value θofs after setting in step S24 is greater than the threshold value θth (step S25: NO), the turning side control unit 60 limits the absolute value of the offset value θofs to the threshold value θth (step S26). If step S26 is carried out, the turning side control unit 60 will use the offset value θofs obtained by limiting the absolute value of the value after setting in step S24 to the threshold value θth for adjusting the reference value θsd thereafter. Thereafter, the turning side control unit 60 ends the reference value adjustment process and moves on to other processes.

[0079] <Reference value adjustment method> As shown in Fig. 8, in the reference value adjustment method, an operator connects the diagnostic tool 45 to the vehicle, i.e., the steering control device 1 (step S110), and sets the factory mode by operating the diagnostic tool 45 (step S111). The processes of steps S110 and S111 are similar to steps S100 and S101 in Fig. 4. In other words, the processes of steps S110 and S111 correspond to a diagnostic state setting process.

[0080] Next, with the factory mode set, the worker places the steered wheels 5 in a straight-ahead state while the vehicle is stopped (step S112). In step S112, the worker adjusts the steering state of the steering unit 6 so that the steered wheels 5 are in a straight-ahead state. For example, if the reference value θsd is a value that deviates from the rack neutral position, the position of the steering wheel 3 will deviate to either the left or right steering side from the steering wheel neutral position, as in the first embodiment.

[0081] Next, the operator outputs an offset command by operating the diagnostic tool 45 (step S113). The operator's operation in step S113 means adjusting the reference value θsd so that the position of the steering wheel 3 coincides with the neutral position of the steering wheel. In this embodiment, the steps S112 and S113 correspond to a reference value adjustment step.

[0082] Next, the worker checks the position of the steering wheel 3, and if it is determined that the adjustment of the reference value θsd is complete, ends the factory mode by operating the diagnostic tool 45 (step S114). Next, the worker removes the diagnostic tool 45 from the steering control device 1 (step S115), and ends the work of adjusting the reference value. The processes of steps S114 and S115 are similar to steps S104 and S105 in FIG. 4.

[0083] <How the reference value θsd is adjusted> In the example shown in Fig. 5, the reference value θsd can be adjusted through the reference value adjustment process by the steering side control unit 60 shown in Fig. 9, in addition to the reference value adjustment method by an operator shown in Fig. 8. In this case, in the reference value adjustment method, the operator outputs an offset command by operating the diagnostic tool 45.

[0084] As shown in Fig. 9, in the reference value adjustment process, when an offset command is input, the turning side control unit 60 sets the offset value θofs to the deviation amount D. As a result, the offset value θofs coincides with the deviation amount D. The adjusted reference value θsd is adjusted so as to be deviated by the deviation amount D to the rightward steering side by adding the offset value θofs corresponding to the deviation amount D. In other words, the adjusted reference value θsd coincides with the deviation amount D, which is the value of the pinion angle θp when the steered wheels 5 are caused to travel straight while the vehicle is stopped, i.e., the rack neutral position.

[0085] As a result, when the vehicle is stopped and the steered wheels 5 are caused to travel straight, the value of the pinion angle θp is calculated as zero, which indicates that the steered wheels 5 are facing in the direction of the solid arrow in Fig. 5, using the reference value θsd of the adjustment degree. In other words, the position of the steering wheel 3 coincides with the neutral position of the steering wheel.

[0086] <Effects of this embodiment> (2-1) In this embodiment, the worker can adjust the reference value θsd while the vehicle is stopped. In this case, since the vehicle is stopped, the reference value θsd can be adjusted without considering the effect of feedback control of the pinion angle θp that accompanies the adjustment of the reference value θsd. This is effective in ensuring the safety of the maintenance worker and achieving highly efficient work when adjusting the reference value θsd.

[0087] <Other embodiments> The above-described embodiments may be modified as follows: In addition, the following other embodiments may be combined with each other within the scope of technical compatibility.

[0088] In the first embodiment, the processes of steps S14 and S15 in the reference value adjustment process may be omitted. The same applies to the processes of steps S25 and S26 in the reference value adjustment process in the second embodiment.

[0089] In the first embodiment, the threshold value θth used in step S14 of the reference value adjustment process may be set from the viewpoint of preventing the driver from feeling uncomfortable, and may be changed as appropriate. For example, the threshold value θth may be set to a value within an experimentally determined range in which the steering reaction force applied based on the steering conversion angle θp_s and the vehicle behavior do not cause the driver to feel uncomfortable. This also applies to the second embodiment.

[0090] In the first embodiment, the offset value θofs may be calculated when the steered wheels 5 are steered to their left or right limits, instead of when the steered wheels 5 are moving straight ahead. For example, in the example shown in Fig. 5, when the steered wheels 5 are steered to their left or right limits, the value of the pinion angle θp deviates from its original value by the deviation amount D. This also applies to the second embodiment.

[0091] In the first embodiment, in step S13 of the reference value adjustment process, similar to step S24 of the reference value adjustment process in the second embodiment, the value of the pinion angle θp at that time may be set as the offset value θofs in response to input of an offset command.

[0092] In the first embodiment, steps S12 and S13 of the reference value adjustment process may be implemented as a process in which the turning-side control unit 60 calculates the pinion angle θp when the steered wheels 5 are in a straight-ahead state, regardless of the input of an offset command, and automatically updates the offset value θofs. In this case, step S103 of the reference value adjustment method can be deleted. The same applies to steps S23 and S24 of the reference value adjustment process in the second embodiment. In this case, step S113 of the reference value adjustment method can be deleted.

[0093] In the first embodiment, the process of step S11 for determining whether or not the steering side control in normal operation can be executed normally may be determined based on the results of diagnosis by the diagnostic tool 45. In this case, the diagnostic tool 45 may output a diagnosis result command indicating the result of determination as to whether or not the steering side control in normal operation can be executed normally to the steering control device 1, i.e., the turning side control unit 60. This is also true for the process of step S21 of the reference value adjustment process in the second embodiment.

[0094] In the reference value adjustment method of the first embodiment, a step of adjusting the toe angles of the left and right steered wheels 5 can be added before the step of step S102 in which the vehicle is driven. In this case, even if a situation is considered in which the reference value θsd deviates from the rack neutral position due to the adjustment of the toe angles of the left and right steered wheels 5, it is possible to deal with this appropriately. This is the same as in the reference value adjustment method of the second embodiment. In other words, in the reference value adjustment method, a step of adjusting the toe angles of the left and right steered wheels 5 can be added before or after the step of step S112 in which the steered wheels 5 are caused to travel straight while the vehicle is stopped.

[0095] In the first embodiment, the vehicle may be configured so that a factory mode can be set through a special operation by an operator on the vehicle or the steering control device 1. In this case, the vehicle may be configured so that an offset command can be input through a special operation by an operator on the vehicle or the steering control device 1. In these cases, the diagnostic tool 45 is not required to adjust the reference value θsd. This also applies to the second embodiment.

[0096] In the first embodiment, the unit amount may be a value that varies based on the value of the pinion angle θp when the steered wheels 5 are traveling straight, i.e., the magnitude of deviation from the reference value θsd. For example, the unit amount may be a value obtained by equally dividing the value of the pinion angle θp when the steered wheels 5 are traveling straight by a predetermined integer n.

[0097] In the second embodiment, in step S24 of the reference value adjustment process, similar to step S13 of the reference value adjustment process in the first embodiment, the offset value θofs may be updated by increasing or decreasing it by the unit amount in response to input of an offset command.

[0098] In each of the above embodiments, the reference value adjustment process may be realized as a process executed by the steering-side control unit 50 and the turning-side control unit 60 in cooperation with each other. For example, the processes of steps S10 and S11 may be performed by the steering-side control unit 50, and the processes of the remaining steps S12 to S15 may be performed by the turning-side control unit 60. In this case, the steering-side control unit 50 and the turning-side control unit 60 correspond to the control unit. This also applies to the reference value adjustment process of the second embodiment.

[0099] In each of the above embodiments, the diagnostic tool 45 may be configured so that an operator can check the value of the pinion angle θp. In this case, the steering-side control unit 60 may be configured so that it can output the value of the pinion angle θp to the diagnostic tool 45 while the factory mode is set.

[0100] In the vehicle interior of each of the above embodiments, for example, the instrument panel may be provided with an alarm device that notifies the driver that the factory mode is being set, i.e., that the reference value θsd is being adjusted. The alarm device may display a text message, issue a voice message, or generate an electronic sound.

[0101] In each of the above embodiments, the steering angle ratio is set to an appropriate value depending on product specifications, etc. The steering angle ratio, for example, "θh:θi", i.e., "θh:θp", may be "1:1" or "1:3". When "θh:θp" is "1:3", a 10° change in steering angle θh is accompanied by a 30° change in steered angle θi. Furthermore, when "θh:θp" is "1:1", the steered conversion angle θp_s and the pinion angle θp basically match. In either case, if the reference value θsd does not deviate from the rack neutral position, the value of the pinion angle θp when the steered wheels 5 are traveling straight is zero.

[0102] In each of the above embodiments, the steering control device 1 may be configured as a single control unit having a combined function in which the steering side control unit 50 operates the steering side motor 13 and the steering side control unit 60 operates the steering side motor 32.

[0103] In each of the above embodiments, when calculating the target reaction torque, the steering-side control unit 50 needs to use at least a state variable that changes depending on the operating state of the steering wheel 3. In this case, the steering-side control unit 50 may use other elements instead of the vehicle speed V or the steering torque Th, or may use other elements in combination.

[0104] In each of the above embodiments, the steering-side control unit 50 may calculate, as the target reaction torque, a value calculated by executing torque feedback control that causes the steering torque Th to follow a target steering torque calculated based on the steering torque Th.

[0105] In each of the above embodiments, the steering-side control unit 50 may take into account the torsion of the steering shaft 11 according to the steering torque Th and calculate the steering angle θh by adding or subtracting the torsion to the rotation angle θa.

[0106] In each of the above embodiments, the steering angle θh may be determined using the detection result of a steering sensor provided on the steering shaft 11 to detect the rotation angle of the steering shaft 11.

[0107] In each of the above embodiments, the pinion angle θp may be determined using the detection result of a pinion angle sensor provided on the pinion shaft 21 to detect the rotation angle of the pinion shaft 21. In each of the above embodiments, the steered-side motor 32 may be, for example, one that is arranged coaxially with the rack shaft 22, or one that is connected to the rack shaft 22 via a worm and wheel to a pinion shaft that constitutes a rack-and-pinion mechanism.

[0108] In the above embodiments, the steering device 2 has a linkless structure in which the steering unit 4 and the turning unit 6 are mechanically separated at all times. However, this is not limiting, and a structure in which the steering unit 4 and the turning unit 6 can be mechanically separated by a clutch may also be used. Furthermore, the steering device 2 may have a structure in which the turning unit 6 can independently steer the left and right steerable wheels 5. Furthermore, the steering device 2 may be an electric power steering device that applies an assist force to assist the driver's steering. In this case, the pinion shaft 21 is mechanically connected to the steering wheel 3 via the steering shaft 11. Furthermore, the steering shaft 11 is mechanically connected to the pinion shaft 21 via a steering ratio variable mechanism that varies the steering ratio. In an electric power steering device with a variable steering ratio, when feedback control of the pinion angle θp is performed, the reference value θsd in the above embodiments may be adjustable. In this case, even if a problem similar to that of the above embodiments occurs, the problem can be solved by applying a configuration similar to that of the above embodiments. [Explanation of symbols]

[0109] 1...Steering control device 2...Steering device 5...Steering wheel 6...Rudder section 45...Diagnostic Tools 60...Steering side control unit (control unit) 61... Pinion angle calculation unit (control angle calculation processing) 63...Angle feedback control unit (angle feedback processing)

Claims

1. A steering control device that controls a steering device including a steering unit that operates to steer steered wheels of a vehicle, a control unit that stores a reference value that is a value associated with a mechanical state of the steering unit that indicates a straight traveling state, which is a steering state of the steered wheels when the vehicle travels straight, and controls an operation of the steering unit; The control unit a control angle calculation process for calculating a control angle as an absolute angle relative to the reference value, the control angle being angle information indicating an actual steering state of the steered wheels; an angle feedback process for feedback-controlling the control angle so as to steer the steered wheels to a target steering state; a reference value adjustment process for adjusting the stored reference value under the condition that the vehicle is in a diagnostic state in which an abnormal state is diagnosed, the reference value adjustment process includes, when the control angle deviates from a value indicating the straight-line driving state in the straight-line driving state, adjusting the reference value so that the deviation between the control angle and the value indicating the straight-line driving state becomes smaller; the process of adjusting the reference value includes a process of reflecting an offset value obtained based on the control angle in the straight-ahead driving state, A steering control device, wherein the reference value adjustment process includes a process of setting an upper limit for the absolute value of the offset value.

2. The control unit is configured to execute the reference value adjustment process while the vehicle is running, on condition that the vehicle is in the diagnostic state; 2. The steering control device according to claim 1, wherein the reference value adjustment process includes a process of obtaining, as the offset value, a value obtained by accumulating unit amounts that are smaller than the value by which the control angle deviates from the value indicating the straight-line driving state in the straight-line driving state.

3. A steering control device that controls a steering device including a steering unit that operates to steer steered wheels of a vehicle, a control unit that stores a reference value that is a value associated with a mechanical state of the steering unit that indicates a straight traveling state, which is a steering state of the steered wheels when the vehicle travels straight, and controls an operation of the steering unit; The control unit a control angle calculation process for calculating a control angle as an absolute angle relative to the reference value, the control angle being angle information indicating an actual steering state of the steered wheels; an angle feedback process for feedback-controlling the control angle so as to steer the steered wheels to a target steering state; a reference value adjustment process for adjusting the stored reference value under the condition that the vehicle is in a diagnostic state in which an abnormal state is diagnosed, the reference value adjustment process includes, when the control angle deviates from a value indicating the straight-line driving state in the straight-line driving state, adjusting the reference value so that the deviation between the control angle and the value indicating the straight-line driving state becomes smaller; the process of adjusting the reference value includes a process of reflecting an offset value obtained based on the control angle in the straight-ahead driving state, The reference value adjustment process includes a process of obtaining, as the offset value, a value obtained by accumulating unit amounts that are smaller than the value by which the control angle deviates from the value indicating the straight-line driving state in the straight-line driving state.

4. The steering control device according to claim 3 , wherein the control unit is configured to execute the reference value adjustment process while the vehicle is traveling, on condition that the vehicle is in the diagnostic state.

5. the control unit is configured to execute the reference value adjustment process while the vehicle is stopped, on condition that the vehicle is in the diagnostic state; The steering control device according to claim 1 or 3, wherein the reference value adjustment process includes a process of obtaining the control angle in the straight traveling state as the offset value.

6. A reference value adjustment method for adjusting a reference value, which is information stored in a control unit of a steering control device that controls a steering device including a steering unit that operates to steer steered wheels of a vehicle, and is a value associated with a mechanical state of the steering unit that indicates a straight-ahead state, which is a steering state of the steered wheels when the vehicle is traveling straight, comprising: the reference value is used when the control unit calculates a control angle, which is angle information indicating an actual steering state of the steered wheels as an absolute angle relative to the reference value, the control angle is used as a control amount when the control unit performs feedback control so as to steer the steered wheels to a target steering state when controlling the operation of the steering unit, a diagnostic state setting step of setting a diagnostic state for diagnosing an abnormal state of the vehicle through operation of a diagnostic tool externally connected to the vehicle; a reference value adjustment step of adjusting the reference value stored in the control unit under the condition that the diagnostic state is being set, the reference value adjustment step includes a step of adjusting the reference value through operation of the diagnostic tool when the control angle deviates from a value indicating the straight-line driving state in the straight-line driving state so that the deviation between the control angle and the value indicating the straight-line driving state becomes smaller; the step of adjusting the reference value includes a step of reflecting an offset value obtained based on the control angle in the straight-ahead driving state, The reference value adjustment method includes a step of obtaining, as the offset value, a value obtained by accumulating unit amounts that are smaller than the value by which the control angle deviates from the value indicating the straight-line driving state in the straight-line driving state.

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