Steering control device

Abstract

The present application relates to a steering control device that includes a control unit that controls the operation of a steering motor (13). The control unit calculates a target reaction force torque that is a target value of a motor torque of the steering motor (13) that becomes a steering reaction force. The control unit calculates a bias axial force that limits steering of a steered wheel in a prescribed direction. The control unit calculates a reference angle from either of a steering angle that is a value indicating an amount of rotation of a steering wheel (3) or a steered angle that is a value indicating an amount of rotation of the steered wheel. The control unit calculates a converted angle from the other of the steering angle or the steered angle that is converted based on a steering angle ratio. The control unit calculates the bias axial force based on a difference between the reference angle and the converted angle.

Description

Technical Field

[0001] This invention relates to a steering control device. Background Technology

[0002] Conventionally, one type of steering control device includes an electric steering system where the power transmission path between the steering control unit operated by the driver and the steering unit that turns the steering wheels according to the driver's steering input is separated. In this type of steering control device, road surface information, such as the road reaction force acting on the steering wheels, cannot be mechanically transmitted to the steering wheel. Therefore, steering control devices that control this type of steering control device include those that control the steering input-side actuator located on the steering control unit to control the steering reaction force, taking road surface information into account, so as to transmit this road surface information to the driver.

[0003] For example, in the steering control device described in Japanese Patent Application Publication No. 2019-127217, when determining the steering reaction force, the axial force acting on the steering shaft installed in the steering unit is considered. As one of the considered axial forces, when the steering wheel encounters an obstacle such as a curb, the axial force of the obstacle collision is used to transmit this situation to the driver. In this case, when the steering wheel encounters an obstacle, the steering control device limits further steering maneuvering by the driver in one direction towards the obstacle by increasing the axial force of the obstacle collision.

[0004] In steering control systems, the axial forces considered for determining steering reaction forces include not only the axial forces related to obstacle collisions, but also various other types of axial forces. In this regard, the axial forces used to convey the situation of the steering wheels hitting an obstacle are set based on the condition that the steering wheels have hit an obstacle. On the other hand, other types of axial forces must be set based on the condition of the steering wheels hitting an obstacle, which is different from the condition of the steering wheels hitting an obstacle. Therefore, since the axial forces must be set separately for each situation when considering various types of axial forces to determine steering reaction forces, there is a concern that the setting of axial forces considered for determining steering reaction forces becomes increasingly complex. Summary of the Invention

[0005] The present invention provides a steering control device that can suppress the complexity of setting the axial force to determine the steering reaction force.

[0006] One aspect of the present invention relates to a steering control device configured to control a steering mechanism. This steering mechanism has a structure that separates the power transmission path between a steering control unit connected to a steering wheel and a steering unit that operates via a steering shaft to turn the steering wheels according to steering inputs to the steering control unit. It also has the function of changing the ratio of the rotation of the steering wheels to the rotation of the steering wheel, i.e., the steering angle ratio. The steering control device includes a control unit that controls at least the operation of a motor provided on the steering control side of the steering control unit, so as to generate a force that resists steering inputs to the steering control unit, i.e., a steering reaction force. The control unit is configured to: calculate the target reaction torque, which is the motor torque of the steering control side motor that becomes the steering control reaction force, as a target value; calculate the deviation axial force of the steering control, which is reflected in the target reaction torque and is used to limit the steering wheel to turn in a predetermined direction; take the angle of either the steering control angle, which is set as a value representing the rotation amount of the steering wheel, or the steering angle, which is set as a value representing the rotation amount of the steering wheel, as a reference angle; take the angle obtained by converting the steering control angle and the other of the steering angle according to the rudder angle ratio as a conversion angle; and calculate the deviation axial force based on the deviation between the reference angle and the conversion angle.

[0007] In the above structure, the deviation axial force is calculated based on the deviation between the reference angle and the converted angle. In this case, considering the change in the rudder angle ratio, when calculating the deviation between the reference angle and the converted angle, a structure can be adopted that converts either the steering angle or the steering angle based on the rudder angle ratio. Therefore, when the relationship between the steering angle and the steering angle shifts, the deviation between the reference angle and the converted angle can be calculated to also take into account the shift in the rudder angle ratio at that time. Furthermore, since the deviation axial force is set based on the deviation between the reference angle and the converted angle, multiple types of axial forces can be considered uniformly, eliminating the need to set the axial force separately for each situation where an axial force should be generated. Therefore, the complexity of setting the axial force considered to determine the steering reaction force can be suppressed.

[0008] In the aforementioned steering control device, the control unit may be configured to: calculate the deviation axial force component based on the deviation between the reference angle and the conversion angle; calculate the axial force viscous component based on the angular velocity, which is the amount of change of the reference angle or the conversion angle, in order to adjust the change of the deviation axial force; and obtain the deviation axial force by making the deviation axial force component reflect the axial force viscous component.

[0009] Based on the above structure, for example, when calculating the viscous component of the axial force in a way that the greater the angular velocity, the smaller the change in the deviation axial force component, it is possible to suppress sudden changes in the deviation axial force. In this case, when reproducing the process of transmitting the steering reaction force to the driver, such as the elasticity of the steering wheel when it encounters an obstacle, the viscous feel of the steering wheel when it turns, and the rigidity of the mechanical structure from the steering wheel to the steering wheel, it is possible to more accurately convey the actual situation occurring at the steering wheel.

[0010] In the aforementioned steering control device, a turning state quantity, which is set to represent the difference between the actual turning action of the vehicle and the ideal turning action of the vehicle, can be input to the control unit. The control unit is configured to calculate the deviation using the steering angle after compensation based on the aforementioned turning state quantity.

[0011] Based on the above structure, when considering the deviation of the actual turning action of the vehicle in a turning state from the ideal turning action of the vehicle, it is possible to adjust how this situation is transmitted to the driver as the steering reaction force.

[0012] In the aforementioned steering control device, the control unit can calculate a plurality of deviation axial force components, including a first deviation axial force component obtained based on the aforementioned deviation and a second deviation axial force component obtained based on the aforementioned deviation in a manner having characteristics different from the first deviation axial force component. The control unit is configured to adopt any one of the first deviation axial force component and the second deviation axial force component into the aforementioned deviation axial force depending on whether the operation of the steering side motor installed in the aforementioned steering unit is not restricted or the operation is restricted.

[0013] Based on the above structure, during the period when the operation of the steering-side motor is restricted, it can be assumed that the manner in which the deviation between the reference angle and the converted angle occurs changes due to the following variation of the steering angle. In this case, depending on whether the aforementioned restriction condition exists, either the first deviation axial force component or the second deviation axial force component is adopted as the deviation axial force. Therefore, an appropriate deviation axial force can be calculated based on whether the operation of the steering-side motor is restricted.

[0014] In the aforementioned steering control device, the control unit may be configured to gradually reduce the difference between the first deviation axial force component and the second deviation axial force component before and after switching between a state where the operation of the steering side motor is not restricted and a state where the operation is restricted.

[0015] According to the above structure, when switching between adopting either the first or second deviation axial force component as the deviation axial force due to a change in whether the operation of the steering side motor is restricted, even if there is a difference between the first and second deviation axial force components before and after the switch, this difference can be gradually reduced. Therefore, sudden changes in the deviation axial force can be suppressed during periods when the operation of the steering side motor is not restricted.

[0016] In the aforementioned steering control device, the control unit can add together a plurality of deviation axial force components, including a first deviation axial force component obtained based on the aforementioned deviation and a second deviation axial force component obtained based on the aforementioned deviation in a manner having characteristics different from the first deviation axial force component, at a predetermined distribution ratio. The control unit is configured to change the distribution ratio depending on whether the operation of the steering side motor installed in the aforementioned steering unit is not restricted or the operation is restricted, and to incorporate the deviation axial force component obtained by adding the components at the aforementioned distribution ratio into the aforementioned deviation axial force.

[0017] Based on the above structure, when considering how the magnitude of the deviation between the reference angle and the converted angle changes due to the following variation in the steering angle during the period when the operation of the steering-side motor is restricted, the distribution ratio of the first deviation axial force component and the second deviation axial force component is changed according to whether the aforementioned restriction condition exists. Therefore, an appropriate deviation axial force can be calculated based on whether the operation of the steering-side motor is restricted.

[0018] In the aforementioned steering control device, the control unit may be configured to gradually change the distribution ratio when the distribution ratio changes due to a switch between a state where the operation of the steering side motor is not restricted and a state where the operation is restricted.

[0019] Based on the above structure, when the distribution ratio changes due to a switch between states where the steering side motor's operation is restricted and not, the change can be gradually reflected. Therefore, during periods when the steering side motor's operation is not restricted, sudden changes in the deviation axial force can be suppressed.

[0020] In the aforementioned steering control device, the control unit may be configured to set the slope of the deviation axial force component relative to the deviation to be greater when the absolute value of the deviation is greater than the absolute value of the deviation is less than the deviation threshold, and the control unit may be configured to set the absolute value of the deviation threshold to be smaller when the operation of the steering side motor is restricted than when the operation of the steering side motor is not restricted.

[0021] Based on the above structure, when considering the situation where the deviation between the reference angle and the converted angle increases due to the reduced following ability of the steering angle under the condition of restricting the operation of the steering-side motor, the increase in deviation can be suppressed.

[0022] Here, if we consider the steering control limit of the steering wheel, i.e. the steering limit of the steering wheel, to limit the steering control of the steering wheel, then in the case of deviation axial force, if the steering wheel actually exceeds the steering control limit side when the steering wheel cannot turn, and there is no deviation between the reference angle and the converted angle, then the steering control of the steering wheel cannot be limited.

[0023] Therefore, in the aforementioned steering control device, the control unit can calculate the end axial force for limiting steering operation in a direction exceeding the steering angle limit, and the control unit is configured to have the function of calculating the deviation axial force and the end axial force respectively.

[0024] Based on the above structure, when the steering angle exceeds the steering angle limit, by setting the end force independently of the deviation axial force, steering control of the steering wheel in the direction exceeding the steering angle limit can be restricted. Therefore, even if there is no deviation between the reference angle and the calculated angle when the steering wheel reaches the steering angle limit, steering control of the steering wheel can be restricted.

[0025] In the aforementioned steering control device, the control unit can select the axial force with the largest absolute value among a plurality of axial forces including the aforementioned deviation axial force and the aforementioned end axial force, and the control unit is configured to obtain the aforementioned target reaction torque by reflecting the selected axial force.

[0026] Based on the above structure, when multiple axial forces, including deviation axial force and end axial force, are calculated to generate steering reaction force simultaneously, the axial force that actually reflects the target reaction torque even in this situation is only the axial force with the largest absolute value. Therefore, even when multiple axial forces, including deviation axial force and end axial force, are calculated to generate steering reaction force simultaneously, excessive increase in steering reaction force can be suppressed.

[0027] In the aforementioned steering control device, the control unit may be configured to perform reaction force control to generate the steering reaction force by driving control of the steering control side motor, and to perform steering control to turn the steering wheel by driving control of the steering side motor provided in the steering unit. The control unit is configured to control the change of the steering angle ratio based on a vehicle speed value that is set to represent the vehicle's travel speed, and to calculate a steering conversion angle that converts the steering angle into the steering control angle according to the steering angle ratio. The reference angle is the steering control angle, and the conversion angle is the steering conversion angle.

[0028] Based on the above structure, the function of converting using the rudder angle ratio can be integrated into the control unit, enabling a structure that is easy to design in terms of the control unit.

[0029] The steering control device according to the above-described manner of the present invention simplifies the setting of steering reaction force. Attached Figure Description

[0030] Hereinafter, the features, advantages, technical and industrial importance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same constituent elements, wherein:

[0031] Figure 1 This is a diagram illustrating a simplified structure of the electric steering control device in the first embodiment.

[0032] Figure 2 This is a block diagram illustrating the function of the steering control device in the first embodiment.

[0033] Figure 3 This is a block diagram illustrating the function of the axial force calculation unit in the first embodiment.

[0034] Figure 4 This is a block diagram illustrating the function of the axial force calculation unit in the first embodiment.

[0035] Figure 5 This is a block diagram illustrating the function of the deviation axial force calculation unit in the first embodiment.

[0036] Figure 6 This is a block diagram illustrating the function of the deviation axial force calculation unit in the second embodiment. Detailed Implementation

[0037] <First Embodiment>

[0038] The first embodiment of the steering control device will be described with reference to the accompanying drawings. Figure 1 As shown, the steering control device 2 of the vehicle, which is controlled by the steering control device 1, is configured as an electric steering steering device. The steering control device 2 includes: a steering control unit 4, which is operated by the driver via a steering wheel 3; and a steering unit 6, which turns the steering wheel 5 according to the steering operation input by the driver to the steering control unit 4.

[0039] The steering control unit 4 includes: a steering shaft 11 to which a steering wheel 3 is fixed; and a steering control actuator 12, which applies a force resisting the driver's steering operation, i.e., a steering reaction force, to the steering wheel 3 via the steering shaft 11. The steering control actuator 12 includes: a steering control side motor 13 as a drive source; and a steering control side deceleration mechanism 14, which decelerates the rotation of the steering control side motor 13 and transmits it to the steering shaft 11. In this embodiment, the steering control side motor 13 is, for example, a three-phase brushless motor.

[0040] The steering unit 6 includes a first pinion shaft 21 and a rack shaft 22 connected to the first pinion shaft 21 as a steering shaft. The first pinion shaft 21 and the rack shaft 22 are configured to have a predetermined angle. A first gear and rack mechanism 23 is formed by meshing the pinion teeth 21a formed on the first pinion shaft 21 with the first rack teeth 22a formed on the rack shaft 22. Steering tie rods 24 are connected to both ends of the rack shaft 22. The front ends of the steering tie rods 24 are connected to steering knuckles (not shown) on which the left and right steering wheels 5 are assembled.

[0041] The steering unit 6 includes a steering actuator 31 that imparts a steering force to the rack shaft 22, causing the steering wheel 5 to turn. The steering actuator 31 imparts the steering force to the rack shaft 22 via the second pinion shaft 32. The steering actuator 31 includes a steering-side motor 33, which serves as a drive source; and a steering-side reduction mechanism 34, which reduces the rotation of the steering-side motor 33 and transmits it to the second pinion shaft 32. The second pinion shaft 32 and the rack shaft 22 are configured to have a predetermined angle. A second gear and rack mechanism 35 is formed by meshing the second pinion tooth 32a formed on the second pinion shaft 32 with the second rack tooth 22b formed on the rack shaft 22.

[0042] In the steering control device 2 configured in this way, the steering actuator 31 rotates to drive the second pinion shaft 32 according to the driver's steering operation. This rotation is converted into axial movement of the rack shaft 22 by the second gear and rack mechanism 35, thereby changing the steering angle of the steering wheel 5. At this time, the steering actuator 12 applies a force to the steering wheel 3 in the opposite direction to the driver's steering operation, as a steering reaction force to resist the driver's steering operation.

[0043] The reason for providing the first pinion shaft 21 is to support the rack shaft 22 together with it inside a housing (not shown). Specifically, the rack shaft 22 is supported by a support mechanism (not shown) of the steering control device 2 so that it can move axially, and is pressed against the first pinion shaft 21 and the second pinion shaft 32. Thus, the rack shaft 22 is supported inside the housing. However, other support mechanisms that support the rack shaft 22 in the housing without using the first pinion shaft 21 may also be provided.

[0044] The electrical structure of the steering control device 2 will be described. The steering control device 1 is connected to the steering side motor 13 and the steering side motor 33. The steering control device 1 controls the operation of the steering side motor 13 and the steering side motor 33. The steering control device 1 includes a central processing unit (not shown) and a memory. The steering control device 1 performs various controls by executing programs stored in the memory through the CPU at predetermined operation cycles.

[0045] A torque sensor 41 is connected to the steering control unit 1, which detects the steering torque Th applied to the steering shaft 11. The torque sensor 41 is positioned closer to the steering wheel 3 than the connection portion of the steering shaft 11 to the steering-side deceleration mechanism 14. The torque sensor 41 detects the steering torque Th based on the torsion of a torsion bar located midway along the steering shaft 11. A steering-side rotation angle sensor 42 and a steering-side rotation angle sensor 43 are also connected to the steering control unit 1.

[0046] The steering-side rotation angle sensor 42 detects the steering-side rotation angle θa of the steering-side motor 13 within a 360-degree range. The steering-side rotation angle θa is used in the calculation of the steering angle θs. The steering-side motor 13 is linked to the steering shaft 11 via the steering-side reduction mechanism 14. Therefore, the steering-side rotation angle θa of the steering-side motor 13 is correlated with the rotation angle of the steering shaft 11, and further with the rotation angle of the steering wheel 3, which is set to represent the amount of rotation. Therefore, the steering angle θs can be calculated based on the steering-side rotation angle θa of the steering-side motor 13.

[0047] The steering-side rotation angle sensor 43 detects the steering-side rotation angle θb of the steering-side motor 33 as a relative angle. The steering-side rotation angle θb is used in the calculation of the pinion angle θp. The steering-side motor 33 is linked to the second pinion shaft 32 via the steering-side reduction mechanism 34. Therefore, there is a correlation between the steering-side rotation angle θb of the steering-side motor 33 and the actual rotation angle of the second pinion shaft 32, i.e., the pinion angle θp. Therefore, the pinion angle θp can be calculated based on the steering-side rotation angle θb of the steering-side motor 33. Furthermore, the second pinion shaft 32 meshes 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. That is, the pinion angle θp is a value reflecting the steering angle of the steering wheel 5. Specifically, the steering torque Th, steering-side rotation angle θa, and steering-side rotation angle θb are positive values ​​when steering to the right and negative values ​​when steering to the left.

[0048] A vehicle speed sensor 44 is connected to the steering control unit 1. The vehicle speed sensor 44 detects a vehicle speed value V, which is set to represent information about the vehicle's travel speed. A host control unit 45 is connected to the steering control unit 1. The host control unit 45 is mounted on the vehicle equipped with the steering control unit 2 as a control unit independent of the steering control unit 1. The host control unit 45 determines the optimal control method based on the vehicle's state at any given moment, and instructs various onboard control devices to perform their respective controls according to the determined control method. In this embodiment, the host control unit 45 generates a drift state quantity θx defined as an angle as a turning state quantity. This turning state quantity is set to represent information about the difference between the actual turning action of the vehicle in a turning driving state and the ideal turning action of the vehicle. For example, a yaw rate sensor is connected to the host control unit 45. The drift state quantity θx is calculated as a value with the dimension of angle based on the deviation between the actual yaw rate detected by the yaw rate sensor and the inferred yaw rate calculated as the ideal yaw rate based on the driving state such as the vehicle speed value V in a turning position. The drift state quantity θx obtained in this way is output to the steering control device 1.

[0049] The steering control device 1 performs reaction force control to generate steering reaction force based on steering torque Th by driving control of steering control side motor 13. In addition, the steering control device 1 performs steering control to turn steering wheel 5 according to steering state by driving control of steering control side motor 33.

[0050] The functions of the steering control unit 1 will be described. The steering control unit 1 includes a central processing unit (CPU) (not shown) and a memory. The CPU executes the program stored in the memory according to a predetermined operation cycle. As a result, various processes are performed.

[0051] Figure 2 The image shows a portion of the processing performed by the steering control device 1. Figure 2 The process shown is a part of the process implemented by the CPU executing a program stored in memory, according to each type of process implemented.

[0052] like Figure 2As shown, the steering control device 1 includes: a steering control side control unit 50 for performing reaction force control; and a steering side control unit 60 for performing steering control. The steering control side control unit 50 has a steering control side current sensor 54. The steering control side current sensor 54 is provided in the connection line between the steering control side control unit 50 and the motor coils of each phase of the steering control side motor 13. The steering control side current sensor 54 detects the actual steering side current value Ia obtained from the current value of each phase of the steering control side motor 13 flowing in this connection line. The steering control side current sensor 54 obtains the voltage drop of the shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering control side motor 13 as the current. Furthermore, in Figure 2 For ease of explanation, the connection lines of each phase and the current sensors of each phase are shown as a single unit in the diagram.

[0053] The steering-side control unit 60 includes a steering-side current sensor 67. The steering-side current sensor 67 is provided in the connection line between the steering-side control unit 60 and the motor coils of each phase of the steering-side motor 33. The steering-side current sensor 67 detects the actual steering-side current value Ib obtained from the current value of each phase of the steering-side motor 33 flowing in this connection line. The steering-side current sensor 67 takes the voltage drop of the shunt resistor connected to the source side of each switching element in an inverter (not shown) corresponding to the steering-side motor 33 as the current. Furthermore, in... Figure 2 For ease of explanation, the connection lines of each phase and the current sensors of each phase are shown as a single unit in the diagram.

[0054] The functions of the steering control side control unit 50 will be explained. The steering control side control unit 50 receives inputs of steering torque Th, vehicle speed V, steering side rotation angle θa, actual steering side current Ib, target pinion angle θp* (described later), steering conversion angle θp_s (described later), and code signal Sm (described later). The steering control side control unit 50 controls the power supply to the steering control side motor 13 based on the steering torque Th, vehicle speed V, steering side rotation angle θa, actual steering side current Ib, steering conversion angle θp_s, and code signal Sm. The steering conversion angle θp_s is calculated based on the steering side rotation angle θb.

[0055] The steering angle control unit 50 includes a steering angle calculation unit 51, a target reaction torque calculation unit 52, and an energization control unit 53. The steering angle calculation unit 51 inputs a steering angle θa. For example, the steering angle calculation unit 51 converts the steering angle θa into a cumulative angle encompassing a range exceeding 360 degrees by counting the number of rotations of the steering wheel 3 from the position of the steering wheel 3 when the vehicle is traveling straight, i.e., the neutral steering position. The steering angle calculation unit 51 calculates the steering angle θs by multiplying the converted cumulative angle based on the rotational speed ratio of the steering angle reduction mechanism 14 by a conversion factor. Furthermore, the steering angle θs is positive when it is an angle to the right of the neutral steering position, and negative when it is an angle to the left of the neutral steering position.

[0056] The target reaction torque calculation unit 52 is input with steering torque Th, vehicle speed value V, steering angle θs, actual steering current value Ib, target pinion angle θp* (described later), steering conversion angle θp_s (described later), and code signal Sm (described later). Based on the steering torque Th, vehicle speed value V, steering angle θs, actual steering current value Ib, target pinion angle θp*, steering conversion angle θp_s, and code signal Sm, the target reaction torque Ts*, which should be generated by the steering motor 13 to become the steering reaction force of the steering wheel 3, is calculated as a reaction force control quantity.

[0057] Specifically, the target reaction torque calculation unit 52 includes a steering force calculation unit 55 and an axle force calculation unit 56. The steering torque Th and vehicle speed V are input to the steering force calculation unit 55. The steering force calculation unit 55 calculates the steering force Tb* based on the steering torque Th and vehicle speed V. The steering force Tb* acts in the same direction as the driver's steering direction. The larger the absolute value of the steering torque Th and the slower the vehicle speed V, the larger the absolute value of the steering force calculation unit 55 calculates for the steering force Tb*. The steering force Tb* is calculated as a value in the dimension of torque (N·m). The obtained steering force Tb* is then output to the subtractor 57.

[0058] The vehicle speed value V, steering angle θs, actual steering current value Ib, target pinion angle θp* (described later), steering conversion angle θp_s (described later), and code signal Sm (described later) are input to the axle force calculation unit 56. The axle force calculation unit 56 calculates the axle force F acting on the rack shaft 22 through the steering wheel 5 based on the vehicle speed value V, steering angle θs, actual steering current value Ib, target pinion angle θp* (described later), steering conversion angle θp_s (described later), and code signal Sm (described later). The axle force F is calculated as a value in the dimension of torque (N·m). The axle force F acts in the opposite direction to the driver's steering direction. The target reaction torque Ts* is calculated by subtracting the axle force F from the steering force Tb* using the subtractor 57. The obtained target reaction torque Ts* is then output to the power control unit 53.

[0059] The power supply control unit 53 is input with the target reaction torque Ts*, the steering angle θa, and the actual steering current value Ia. The power supply control unit 53 calculates the current command value Ia* for the steering motor 13 based on the target reaction torque Ts*. The power supply control unit 53 calculates the deviation between the current command value Ia* and the current value on the dq coordinate obtained by transforming the actual steering current value Ia based on the steering angle θa, and controls the power supply to the steering motor 13 to eliminate this deviation. The steering motor 13 generates torque corresponding to the target reaction torque Ts*. This provides the driver with a suitable feel.

[0060] The functions of the steering side control unit 60 will be explained. The steering side control unit 60 includes a pinion angle calculation unit 61, a rudder angle ratio variable control unit 62, and a pinion angle feedback control unit (…). Figure 2 The components include the "pinion angle F / B control unit" 63, the power-on control unit 64, the rudder angle conversion unit 65, and the code signal generation unit 66.

[0061] The steering-side rotation angle θb is input to the pinion angle calculation unit 61. The pinion angle calculation unit 61 converts the steering-side rotation angle θb into a cumulative angle encompassing a range exceeding 360 degrees by counting the number of rotations of the steering-side motor 33 from the position of the rack shaft 22 (i.e., the rack neutral position) when the vehicle is traveling straight. The pinion angle calculation unit 61 calculates the actual rotation angle of the second pinion shaft 32, i.e., the pinion angle θp, by multiplying the calculated cumulative angle by a conversion factor based on the rotational speed ratio of the steering-side reduction mechanism 34. Furthermore, the pinion angle θp is positive when it is an angle to the right of the rack neutral position and negative when it is an angle to the left of the rack neutral position. The obtained pinion angle θp is output to the pinion angle feedback control unit 63. Additionally, the compensated pinion angle θp′ is calculated by subtracting the drift state quantity θx from the pinion angle θp using the subtractor 68. The compensated pinion angle θp′ obtained in this way is output to the rudder angle conversion unit 65.

[0062] The vehicle speed value V and the steering angle θs are input to the variable steering angle ratio control unit 62. The variable steering angle ratio control unit 62 calculates the target pinion angle θp* by adding the steering angle θs to an adjustment amount. The variable steering angle ratio control unit 62 is used to change the ratio of the target pinion angle θp* to the steering angle θs, that is, the adjustment amount of the steering angle ratio is variable according to the vehicle speed value V. For example, the adjustment amount is changed in such a way that the change of the target pinion angle θp* relative to the change of the steering angle θs is greater when the vehicle speed value V is slower than when the vehicle speed value V is faster. There is a correlation between the steering angle θs and the target pinion angle θp*. In addition, the pinion angle θp is controlled based on the target pinion angle θp*. Therefore, there is also a correlation between the steering angle θs and the pinion angle θp.

[0063] The target pinion angle θp* and the pinion angle θp are input to the pinion angle feedback control unit 63. To ensure that the pinion angle θp follows the target pinion angle θp*, the pinion angle feedback control unit 63 performs PD control using proportional and derivative terms as feedback control for the pinion angle θp. Specifically, the pinion angle feedback control unit 63 calculates the deviation between the target pinion angle θp* and the pinion angle θp, and calculates the steering force command value T*, which is the target control quantity and serves as the target steering force, in a manner that eliminates this deviation.

[0064] The power supply control unit 64 is input with a steering force command value T*, a steering side rotation angle θb, and a steering side actual current value Ib. The power supply control unit 64 calculates the current command value Ib* for the steering side motor 33 based on the steering force command value T*. Furthermore, the power supply control unit 64 calculates the deviation between the current command value Ib* and the current value on the dq coordinate obtained by transforming the steering side actual current value Ib based on the steering side rotation angle θb, and controls the power supply to the steering side motor 33 to eliminate this deviation. As a result, the steering side motor 33 rotates by the angle corresponding to the steering force command value T*.

[0065] The vehicle speed value V and the compensated pinion angle θp′ are input to the steering angle conversion unit 65. The steering angle conversion unit 65 calculates the steering conversion angle θp_s by adding the compensated pinion angle θp′ to the adjustment amount Δθ′. The steering angle conversion unit 65 changes the adjustment amount Δθ′ based on the vehicle speed value V in a manner that reverses the input and output relationship relative to the calculation rules defined by the steering angle ratio variable control unit 62. That is, if the steering angle ratio variable control unit 62, for example, increases the change of the target pinion angle θp* relative to the change of the steering angle θs when the vehicle speed value V is slower than when the vehicle speed value V is faster, then the steering angle conversion unit 65 changes the adjustment amount Δθ′ in a manner that decreases the change of the steering conversion angle θp_s relative to the change of the compensated pinion angle θp′ when the vehicle speed value V is slower than when the vehicle speed value V is faster. Therefore, the rudder angle conversion unit 65 calculates the compensated pinion angle θp′, which is expressed as a steering angle index, and converts it into a steering conversion angle θp_s, which is expressed as a steering control angle index, based on the rudder angle ratio. The conversion angle described in the technical solution is equivalent to the steering conversion angle θp_s. The steering conversion angle θp_s thus obtained is output to the shaft force calculation unit 56.

[0066] The code signal generation unit 66 inputs the detection results from a temperature sensor (not shown) or similar source. The temperature sensor detects, for example, the temperature of the motor coil of the steering motor 33 or the inverter. In this case, the code signal generation unit 66 determines the heating state as the state of the steering motor 33 by comparing the temperature detected by the temperature sensor with multiple temperature thresholds. The heating states of the steering motor 33 are, for example, normally heated, slightly overheated, moderately overheated, and severely overheated, in order of increasing demand for restricting the operation of the steering motor 33. The normally heated state indicates that the operation of the steering motor 33 is not restricted. On the other hand, the slightly overheated, moderately overheated, and severely overheated states indicate that the operation of the steering motor 33 is restricted.

[0067] Additionally, the detection results from a voltage sensor (not shown) are input to the code signal generation unit 66. The voltage sensor, for example, detects the voltage of a DC power source such as a battery. In this case, the code signal generation unit 66 determines the state of the DC power supply voltage by comparing the voltage detected by the voltage sensor with multiple voltage thresholds. In order of increasing demand for restricting the operation of the steering motor 33, the DC power supply voltage states include, for example, a normal voltage state, a slight voltage drop state, a moderate voltage drop state, and a severe voltage drop state. Furthermore, a normal voltage state indicates that the operation of the steering motor 33 is not restricted. On the other hand, a slight voltage drop state, a moderate voltage drop state, and a severe voltage drop state indicate that the operation of the steering motor 33 is restricted.

[0068] The code signal generation unit 66 performs the following processing when generating the code signal Sm. Specifically, the code signal generation unit 66 encodes the state of the steering control device 2 according to the code table stored in the storage unit of the steering control device 1. Encoding refers to the process of representing the state of the steering control device 2 using codes as symbols. The state of the steering control device 2 includes the heating state of the steering-side motor 33 and the voltage state of the DC power supply. An example of the correspondence between the state of the steering control device 2 and the codes is described below.

[0069] • Code “0”… Normal state where the operation of the steering motor 33 is not restricted. • Code “1A”… Slight overheating state of the steering motor 33. • Code “1B”… Moderate overheating state of the steering motor 33. • Code “1C”… Severe overheating state of the steering motor 33. • Code “2A”… Slight voltage drop state of the DC power supply. • Code “2B”… Moderate voltage drop state of the DC power supply. • Code “2C”… Severe voltage drop state of the DC power supply. The code signal generation unit 66 generates a code signal Sm representing the code corresponding to the state of the steering control device 2. The obtained code signal Sm is output to the axial force calculation unit 56.

[0070] In this embodiment, by outputting a signal, i.e., a code signal Sm, indicating the state of the steering control device 2 to the steering operation side control unit 50 via the steering side control unit 60, the steering operation side control unit 50 can grasp the state of the steering control device 2, particularly the state of the steering side motor 33. Here, if only the state of the steering side motor 33 is considered, it is also possible to achieve this by having the steering side control unit 60 output various information such as the temperature of the steering side motor 33 and the voltage of the DC power supply to the steering operation side control unit 50. In this respect, compared to the case where the steering side control unit 60 outputs various information such as the temperature of the steering side motor 33 and the voltage of the DC power supply to the steering operation side control unit 50, the amount of information that must be output is reduced, which is advantageous in reducing the communication load between the steering operation side control unit 50 and the steering side control unit 60.

[0071] Specifically, the temperature threshold is set, for example, as a range of values ​​determined experimentally based on the temperature at which the motor coil or inverter is considered to be approaching an overheated state. Similarly, the voltage threshold is set, for example, as a range of values ​​determined experimentally based on the voltage at which the DC power supply is considered to be approaching a state where it cannot adequately supply power. In states other than normal heating and voltage conditions, the steering side control unit 60 performs protection mode control to limit the operation of the steering side motor 33. On the other hand, in normal heating and voltage conditions, the steering side control unit 60 performs normal mode control without limiting the operation of the steering side motor 33 and without limiting its power supply.

[0072] Here, the function of the axial force calculation unit 56 will be explained in more detail. For example... Figure 3 As shown, the axial force calculation unit 56 includes an axial force distribution calculation unit 71, an end axial force calculation unit 72, a deviation axial force calculation unit 73, and an axial force selection unit 74.

[0073] The axial force calculation unit 71 calculates the distributed axial force Fd corresponding to the axial force acting on the rack shaft 22. The distributed axial force Fd is equivalent to the calculated axial force acting on the rack shaft 22, obtained by distributing the angular axial force Fr and the current axial force Fi (described later) according to their respective distribution ratios, in a manner that appropriately reflects the axial force acting on the rack shaft 22 through the steering wheel 5. The distributed axial force Fd thus obtained is output to the adder 75.

[0074] The end-force calculation unit 72 calculates the end-force Fie, which is transmitted to the driver when the steering wheel 3 reaches its steering limit, i.e., the steering limit of the steering wheel 5. The end-force Fie is equivalent to the force that resists further steering maneuvering of the steering wheel 3 beyond the steering angle limit when the absolute value of the steering angle θs approaches the steering angle limit corresponding to the steering limit. The end-force Fie thus obtained is output to the force selection unit 74.

[0075] The deviation axial force calculation unit 73 calculates the deviation axial force Fv that is transmitted to the driver when there is a deviation between the steering control state of the steering wheel 3 and the steering state of the steering wheel 5, taking into account the rudder angle ratio. Examples of deviations between the steering control state of the steering wheel 3 and the steering state of the steering wheel 5 include: For example, even though the steering wheel 5 encounters an obstacle such as a curb and cannot be turned in one direction towards that obstacle, the power transmission path between the steering control unit 4 and the steering unit 6 is separated, causing the steering wheel 3 to be turned in that direction beyond the stop position corresponding to the stop position of the steering wheel 5. Furthermore, a situation can be described where, due to overheat protection, the operation of the steering-side motor 33 is restricted, and the pinion angle θp cannot follow the target pinion angle θp*, resulting in a loss of correlation between the steering control angle θs and the steering angle. The deviation axial force Fv is equivalent to a force that resists further steering control of the steering wheel 3 when the steering wheel 5 encounters an obstacle such as a curb. Furthermore, when the operation of the steering-side motor 33 is restricted for overheat protection, it is equivalent to resisting the steering operation of the steering wheel 3 in order to ensure the following of the pinion angle θp towards the target pinion angle θp*. The resulting deviation axial force Fv is output to the axial force selection unit 74.

[0076] The final axial force Fie and the deviation axial force Fv are input to the axial force selection unit 74. The axial force selection unit 74 selects the axial force with the largest absolute value between the final axial force Fie and the deviation axial force Fv, and calculates the selected axial force as the selected axial force Fsl. The axial force F is calculated by adding the selected axial force Fsl to the allocated axial force Fd using the adder 75. The axial force F obtained in this way is output to the subtractor 57. The target reaction torque Ts* is calculated by subtracting the allocated axial force Fd from the steering force Tb* using the subtractor 57. The target reaction torque Ts* obtained in this way is output to the power control unit 53.

[0077] Next, the functions of the axial force calculation unit 71 will be explained in detail. For example... Figure 4As shown, the axial force calculation unit 71 includes an angle axial force calculation unit 81, a current axial force calculation unit 82, and a distribution ratio calculation unit 83.

[0078] The target pinion angle θp* and vehicle speed V are input to the axial force calculation unit 81. The axial force calculation unit 81 calculates the axial force Fr based on the target pinion angle θp* and vehicle speed V. The axial force Fr is an ideal value of the axial force defined by an arbitrarily set vehicle model. The axial force Fr is calculated as an axial force that does not reflect road surface information. Road surface information includes minor bumps and dips that do not affect the lateral movement of the vehicle, as well as step differences that do affect the lateral movement of the vehicle. Specifically, the axial force calculation unit 81 calculates the axial force Fr in such a way that the larger the absolute value of the target pinion angle θp*, the larger the absolute value of the axial force Fr. Furthermore, the axial force calculation unit 81 calculates the axial force Fr in such a way that the absolute value of the axial force Fr increases as the vehicle speed V increases. The axial force Fr is calculated as a value in the dimension of torque (N·m). The axial force Fr thus obtained is output to the multiplier 84.

[0079] The actual steering-side current value Ib is input to the current axial force calculation unit 82. The current axial force calculation unit 82 calculates the current axial force Fi based on the actual steering-side current value Ib. The current axial force Fi is the axial force that actually acts on the rack shaft 22 to turn the steering wheel 5, i.e., the estimated value of the axial force actually transmitted to the rack shaft 22. The current axial force Fi is calculated as an axial force reflecting the aforementioned road surface information. Specifically, the current axial force calculation unit 82 considers the torque applied to the rack shaft 22 by the steering-side motor 33 and the torque corresponding to the force applied to the rack shaft 22 through the steering wheel 5 to be balanced, and calculates the current axial force Fi in such a way that the larger the absolute value of the actual steering-side current value Ib, the larger the absolute value of the current axial force Fi. The current axial force Fi is calculated as a value in the dimension of torque (N·m). The obtained current axial force Fi is then output to the multiplier 85.

[0080] The vehicle speed value V is input to the allocation ratio calculation unit 83. The allocation ratio calculation unit 83 calculates the allocation gain Di based on the vehicle speed value V. The allocation gain Di is the allocation ratio of the current axial force Fi when the axial force F is obtained by allocating the angular axial force Fr and the current axial force Fi. Specifically, the allocation ratio calculation unit 83 has an allocation gain mapping that defines the relationship between the vehicle speed value V and the allocation gain Di, and performs mapping calculation on the allocation gain Di with the vehicle speed value V as input.

[0081] The allocation gain Di is "1 (100%)" when the vehicle speed value V is a low speed, including when the vehicle is stopped. In this case, it means that at low vehicle speeds, only the current axial force Fi is allocated to the axial force F, that is, no angular axial force Fr is allocated. Conversely, the allocation gain Di is "zero (0%)" when the vehicle speed value V is, for example, a high vehicle speed of 60 km / h or above. In this case, it means that at high vehicle speeds, only the angular axial force Fr is allocated to the axial force F, that is, no current axial force Fi is allocated. In other words, the allocation ratio in this embodiment includes the concept of zero values ​​for both the angular axial force Fr and the current axial force Fi, where only one of them is allocated to the axial force F.

[0082] The distribution gain Di obtained in this way is multiplied by the current axial force Fi obtained by the current axial force calculation unit 82, and the final current axial force Fim obtained by the multiplier 85 is output to the adder 88. Additionally, the distribution gain Dr is calculated by subtracting the distribution gain Di from the "1" stored in the storage unit 87 using the subtractor 86. The distribution gain Dr obtained in this way is output to the multiplier 84. The distribution gain Dr is the distribution ratio of the angle axial force Fr when the axial force F is obtained by distributing the angle axial force Fr and the current axial force Fi. That is, the distribution gain Dr is calculated such that the sum of the distribution gain Di and the distribution gain Di is "1 (100%)". The storage unit 87 refers to a defined storage area of ​​a memory (not shown).

[0083] The distribution gain Dr obtained in this way is multiplied by the angular axial force Fr obtained by the angular axial force calculation unit 81, and the result is output to the adder 88 as the final angular axial force Frm obtained by the multiplier 84. In addition, the angular axial force Frm obtained in this way is added to the current axial force Fim, and the result is output to the adder 75 as the distribution axial force Fd obtained by the adder 88.

[0084] The function of the end-effector force calculation unit 72 is explained in detail. For example... Figure 3As shown, a target pinion angle θp* is input to the end-effector force calculation unit 72. The end-effector force calculation unit 72 calculates the end-effector force Fie based on the target pinion angle θp*. Specifically, the end-effector force calculation unit 72 has an end-effector force mapping that defines the relationship between the target pinion angle θp* and the end-effector force Fie, and performs mapping calculation on the end-effector force Fie by taking the target pinion angle θp* as input. If the absolute value of the target pinion angle θp* is below the threshold angle θie, the end-effector force calculation unit 72 calculates the end-effector force Fie as "0". If the absolute value of the target pinion angle θp* is greater than the threshold angle θie, the end-effector force calculation unit 72 calculates the end-effector force Fie with an absolute value greater than "0". The end-effector force Fie is set to an absolute value that, if the absolute value of the target pinion angle θp* exceeds the threshold angle θie to a certain extent, becomes so large that further steering of the steering wheel 3 cannot be achieved by human hand. The end-effector force Fie thus obtained is output to the axle force selection unit 74.

[0085] Next, the functions of the deviation axial force calculation unit 73 will be explained in detail. For example... Figure 5 As shown, the deviation axial force calculation unit 73 includes an axial force basic component calculation unit 101, an axial force viscous component calculation unit 102, a gradient processing unit 103, an upper limit protection processing unit 104, and a symbol processing unit 105.

[0086] The axle force basic component calculation unit 101 is input with the deviation Δθ obtained by subtracting the steering conversion angle θp_s from the steering control angle θs using the subtractor 106, and the code signal Sm. The axle force basic component calculation unit 101 calculates the axle force basic component FΔθ based on the deviation Δθ and the code signal Sm. Specifically, the axle force basic component calculation unit 101 has an axle force basic component mapping that determines the relationship between the absolute value of the deviation Δθ and the axle force basic component FΔθ, and performs mapping calculations on the axle force basic component FΔθ using the deviation Δθ as input. The reference angle described in the technical solution is equivalent to the steering control angle θs.

[0087] In this embodiment, the axial force basic component calculation unit 101 has two mappings as axial force basic component mappings. The axial force basic component calculation unit 101 calculates the axial force basic component FΔθ based on the code signal Sm and using either of the two mappings. When the axial force basic component calculation unit 101 is input with code "0" indicating a normal state where the operation of the steering side motor 33 is not restricted, i.e., code signal Sm indicating execution of the normal mode, the axial force basic component calculation unit 101 implements the following: Figure 5 The mapping operation of the axial force basic component mapping used in the normal mode represented by double-dotted lines. Figure 5The axial force base component mapping for the normal mode, indicated by double-dotted lines, is set such that if the absolute value of the deviation Δθ reaches or exceeds the first deviation threshold Δθ1, the slope of the axial force base component FΔθ relative to the deviation Δθ is greater than when the absolute value of the deviation Δθ is less than the first deviation threshold Δθ1. That is, if the axial force base component calculation unit 101 is input with a code signal Sm indicating execution of the normal mode, then when the absolute value of the deviation Δθ is less than the first deviation threshold Δθ1, the axial force base component FΔθ is calculated as "0", and if the absolute value of the deviation Δθ reaches or exceeds the first deviation threshold Δθ1, the axial force base component FΔθ with an absolute value greater than "0" is calculated. The axial force base component FΔθ obtained through the axial force base component mapping for the normal mode is equivalent to the first deviation axial force component.

[0088] If the axial force basic component calculation unit 101 receives a code signal Sm other than "0", which indicates a state other than the normal state in which the operation of the steering side motor 33 is restricted, that is, a code signal Sm indicating the execution of the protection mode, then the operation is implemented. Figure 5 The protection mode, represented by solid lines, uses the mapping operation of the axial force basic component mapping. Figure 5 The axial force base component mapping for the protection mode, represented by solid lines, is set such that if the absolute value of the deviation Δθ reaches or exceeds the second deviation threshold Δθ2, the slope of the axial force base component FΔθ relative to the deviation Δθ is greater than when the absolute value of the deviation Δθ is less than the second deviation threshold Δθ2. That is, if the axial force base component calculation unit 101 is input with a code signal Sm representing the execution of the protection mode, then when the absolute value of the deviation Δθ is less than the second deviation threshold Δθ2, the axial force base component FΔθ is calculated as "0", and if the absolute value of the deviation Δθ reaches or exceeds the second deviation threshold Δθ2, the axial force base component FΔθ with an absolute value greater than "0" is calculated. The axial force base component FΔθ obtained through the axial force base component mapping for the protection mode is equivalent to the second deviation axial force component. The axial force base component FΔθ thus obtained is output to the gradient processing unit 103.

[0089] In this embodiment, the second deviation threshold Δθ2 is set to a value less than the first deviation threshold Δθ1. That is, the axial force basis component mapping used in the normal mode mapping operation takes the shape of a mapping used in the protection mode mapping operation that has been shifted parallel to the direction in which the deviation Δθ increases. Therefore, the dead zone of the deviation Δθ in the axial force basis component mapping used in the normal mode mapping operation is set larger than that in the protection mode mapping operation. In other words, in the normal mode, compared to the protection mode, the slope of the axial force basis component FΔθ relative to the deviation Δθ increases when the deviation Δθ is larger. This is because if the deviation axial force Fv is calculated based on a small deviation Δθ in the normal mode, there is a concern that it could hinder the driver's steering operation.

[0090] In particular, in this embodiment, since the pinion angle feedback control unit 63 uses PD control and does not have an integral term, there is a possibility that a small deviation between the target pinion angle θp* and the pinion angle θp exists compared to PID control. If there is a small deviation between the target pinion angle θp* and the pinion angle θp, there is a possibility that a small deviation Δθ may be generated as a result. Therefore, if we assume that the dead zone is set to the same size in both the protection mode and the normal mode, it is possible that the deviation axial force Fv will frequently occur in the normal mode when the deviation Δθ is small. As a result, there is a concern that the driver's steering operation may be hindered in the normal mode. However, by setting the dead zone in the normal mode to be larger than that in the protection mode, as in this embodiment, the frequency of the deviation axial force Fv occurring in the stage where the deviation Δθ is small can be suppressed even in the normal mode, and the situation where the driver's steering operation is hindered by the deviation axial force Fv in the normal mode can be suppressed.

[0091] The axial force base component FΔθ and the code signal Sm are input to the gradient processing unit 103. When the content represented by the code signal Sm switches between codes other than "0", i.e., between normal mode and protection mode, the gradient processing unit 103 performs gradient processing on the axial force base component FΔθ relative to time. Specifically, when switching between normal mode and protection mode, the gradient processing unit 103 obtains the deviation of the axial force base component FΔθ after the switch based on the axial force base component FΔθ calculated before the switch, and calculates this deviation as an offset. In this case, the gradient processing unit 103 calculates the processed axial force base component FΔθ′ by shifting the switched axial force base component FΔθ away from the original axial force base component FΔθ by an offset amount. Moreover, the gradient processing unit 103 performs gradient processing that gradually decreases the offset amount so that any switched axial force base component FΔθ changes to its original switched value. Therefore, even when switching between normal mode and protection mode, sudden changes in the processed axial force base component FΔθ′ can be suppressed. Specifically, during the period when the content represented by the code signal Sm is not switching between normal mode and protection mode, if the aforementioned offset does not exist, the gradient processing unit 103 calculates the axial force base component FΔθ into the processed axial force base component FΔθ′. In this embodiment, the axial force base component calculation unit 101 and the gradient processing unit 103 correspond to the deviation axial force component calculation unit. Furthermore, in this embodiment, the processed axial force base component FΔθ′ corresponds to the deviation axial force component. The thus obtained processed axial force base component FΔθ′ is output to the adder 107.

[0092] The steering angular velocity ωs, obtained by differentiating the steering angle θs using a differentiator 108, is input to the axial force viscous component calculation unit 102. The steering angular velocity ωs is set to represent the amount of change in the steering angle θs. Specifically, the axial force viscous component calculation unit 102 has an axial force viscous component mapping that determines the relationship between the absolute value of the steering angular velocity ωs and the axial force viscous component Fω, and performs mapping calculations on the axial force viscous component Fω using the absolute value of the steering angular velocity ωs as input. The angular velocity described in the technical solution corresponds to the steering angular velocity ωs.

[0093] When the absolute value of the steering angular velocity ωs is large, the axial force viscous component calculation unit 102 calculates the axial force viscous component Fω with a larger absolute value compared to when the absolute value of the steering angular velocity ωs is small. The axial force viscous component Fω is set to have a larger absolute value as the steering angular velocity ωs increases. The axial force viscous component Fω functions to suppress sudden changes in the axial force base component FΔθ. That is, the axial force viscous component Fω functions to slow down the increase of the deviation axial force Fv calculated using the axial force base component FΔθ. As a result, the elasticity of the tire when the steering wheel 5 hits an obstacle, the viscous feel of the tire when the steering wheel 5 turns, and the rigidity of the mechanical structure from the steering wheel 5 to the steering wheel 3 are reproduced. Furthermore, when the deviation Δθ is less than the deviation threshold, that is, when the axial force base component FΔθ is "0", the axial force viscous component calculation unit 102 outputs the axial force viscous component Fω as "0" without reflecting the calculated axial force viscous component Fω in the axial force base component FΔθ.

[0094] The total axial force Ft is calculated by adding the viscous component Fω of the axial force to the processed basic component FΔθ′ of the axial force using adder 107. The total axial force Ft obtained in this way is output to the upper limit protection processing unit 104. The vehicle speed value V, the total axial force Ft, and the maximum value Flim stored in the storage unit 109 are input to the upper limit protection processing unit 104. The storage unit 109 refers to a defined storage area of ​​a memory (not shown). The maximum value Flim is set as a value within a range determined experimentally, which is an indicator that, when the vehicle speed value V is, for example, the aforementioned high vehicle speed, it will not affect the steering operation of the steering wheel 3 and can maximize the total axial force Ft.

[0095] When the vehicle speed value V is less than, for example, the speed threshold indicating a low vehicle speed, the upper limit protection processing unit 104 outputs the total axle force Ft as the protected total axle force Ft′. Additionally, when the vehicle speed value V is above, for example, the speed threshold indicating a high vehicle speed, the upper limit protection processing unit 104 performs upper limit protection processing on the total axle force Ft. When the total axle force Ft is less than the maximum value Flim while performing upper limit protection processing, the upper limit protection processing unit 104 outputs the total axle force Ft as the protected total axle force Ft′. Furthermore, when the total axle force Ft is above or equal to the maximum value Flim during upper limit protection processing, the upper limit protection processing unit 104 outputs the maximum value Flim as the protected total axle force Ft′. The thus obtained protected total axle force Ft′ is output to the multiplier 110.

[0096] The actual steering current value Ib is input to the symbol processing unit 105. The symbol processing unit 105 sets the sign of the total axial force Ft′ after protection based on the actual steering current value Ib. That is, when the actual steering current value Ib is a positive value including zero, the symbol processing unit 105 outputs "+1", and when the actual steering current value Ib is a negative value, the symbol processing unit 105 outputs "-1". The value of "1" or "-1" obtained in this way is multiplied by the total axial force Ft′ after protection and output to the axial force selection unit 74 as the deviation axial force Fv obtained by the multiplier 110.

[0097] The operation of the first embodiment will be explained. The condition of the steering wheel 5 is reflected in the pinion angle θp obtained as information of the steering unit 6. For example, when the steering wheel 5 encounters an obstacle, the pinion angle θp cannot change from the pinion angle θp when the steering wheel 5 encounters the obstacle towards the obstacle side. On the other hand, the condition of the steering wheel 3 is reflected in the steering angle θs obtained as information of the steering control unit 4. For example, when the steering wheel 5 encounters an obstacle, if the axial force used to convey the condition that the steering wheel 5 has encountered an obstacle to the driver is not given as a steering control reaction force, the steering angle θs can change further from the steering angle θs when the steering wheel 5 encounters the obstacle towards the obstacle side. Therefore, the relationship between the steering angle θs and the pinion angle θp sometimes deviates. The inventors have focused on a common point in both cases where an axial force is set to convey the situation of the steering wheel 5 encountering an obstacle to the driver, and in cases where an axial force is set to consider other types of situations of the steering wheel 5, different from the situation of the steering wheel 5 encountering an obstacle, is applied: the relationship between the steering angle θs and the pinion angle θp may shift for some reason. That is, the inventors have discovered that when the relationship between the steering angle θs and the pinion angle θp shifts for some reason, if the steering reaction force is determined in a way that either does not increase the shift or eliminates the shift, multiple types of axial forces can be considered uniformly.

[0098] Specifically, in this embodiment, the deviation axial force Fv is calculated based on the deviation Δθ between the steering control angle θs and the steering conversion angle θp_s. In this case, if the premise is a change in the rudder angle ratio, the deviation Δθ between the steering control angle θs and the pinion angle θp is no longer in a one-to-one correspondence, and a structure is adopted to convert the pinion angle θp to the steering control angle θs based on the rudder angle ratio when calculating the deviation Δθ between the steering control angle θs and the steering conversion angle θp_s. Thus, when a deviation occurs in the relationship between the steering control angle θs and the pinion angle θp, the deviation Δθ between the steering control angle θs and the steering conversion angle θp_s can be calculated to also take into account the offset of the rudder angle ratio at this time. Moreover, if the basic component of the axial force FΔθ, i.e., the deviation axial force Fv, is set based on the deviation Δθ between the steering control angle θs and the steering conversion angle θp_s, multiple types of axial forces can be considered uniformly, so it is not necessary to set the axial force separately for each situation in which axial force should be generated each time.

[0099] The effects of the first embodiment will be explained.

[0100] (1-1) For example, since it is no longer necessary to set the axial force separately for each situation where the steering wheel 5 hits an obstacle such as a curb, or the output of the steering motor 33 is limited for overheat protection, the situation where the setting of the axial force to determine the steering reaction force becomes complicated can be suppressed.

[0101] (1-2) Since the axial force viscous component Fω is calculated in such a way that the larger the absolute value of the steering angular velocity ωs, the smaller the change in the axial force basic component FΔθ, sudden changes in the deviation axial force Fv can be suppressed. In this case, when transmitting the steering reaction force to the driver, such as the elasticity of the tire when the steering wheel 5 encounters an obstacle, the viscous feel of the tire when the steering wheel 5 turns, and the rigidity of the mechanical structure from the steering wheel 5 to the steering wheel 3, the actual situation occurring at the steering wheel 5 can be transmitted more accurately. Furthermore, regarding the rigidity of the mechanical structure from the steering wheel 5 to the steering wheel 3, the rigidity can be reproduced when the power transmission path between the steering control unit 4 and the steering unit 6 is connected. In this case, when transmitting the steering reaction force to the driver, the same rigidity of the steering wheel 5 as when the steering control device 2 is a steering control device that is always mechanically connected between the steering control unit 4 and the steering unit 6 can be reproduced. In addition, the return of the steering wheel 3 to the neutral position when the driver releases his hands from the steering wheel 3 or when the force required to hold the steering wheel 3 is reduced can be mitigated.

[0102] (1-3) Consider the deviation of the actual vehicle's turning action from the ideal turning action of the vehicle in a turning driving state. Examples of actual vehicle turning actions include understeer and oversteer. Therefore, according to this embodiment, the deviation axial force calculation unit 73 calculates the deviation Δθ using a compensated pinion angle θp′ based on the drift state amount θx. Thus, for example, in an oversteer state, the adjustment range of the steering reaction force transmission method, such as the amount of pinion angle θp being slightly smaller than that of the steering wheel 5, is determined in a way that allows for a wider range of steering reaction force transmission methods.

[0103] (1-4) During the period when the operation of the steering motor 33 is restricted, it can be assumed that the manner in which the deviation Δθ between the steering angle θs and the steering conversion angle θp_s occurs changes due to the following change in the pinion angle θp. In this case, depending on whether the operation of the steering motor 33 is restricted, it is possible to switch which axial force base component is adopted into the deviation axial force Fv: the axial force base component FΔθ obtained by mapping the axial force base component in normal mode or the axial force base component FΔθ obtained by mapping the axial force base component in protection mode. Thus, an appropriate deviation axial force Fv can be calculated based on whether the operation of the steering motor 33 is restricted.

[0104] (1-5) When the axial force base component mapping is switched due to whether the operation of the steering side motor 33 is restricted, the difference between the two conditions before and after the switch can be gradually reduced. Thus, during the period when the operation of the steering side motor 33 is not restricted, the sudden change of the deviation axial force Fv can be suppressed.

[0105] (1-6) When the protection mode is executed, the deviation Δθ between the steering control angle θs and the steering conversion angle θp_s is small because the following performance of the pinion angle θp is reduced.

[0106] (1-7) is configured such that, compared to the protection mode, if the deviation Δθ does not increase to a certain extent when the normal mode is being executed, the slope of the basic component of the axial force FΔθ relative to the deviation Δθ does not increase, and the dead zone of the deviation Δθ increases. Therefore, when the normal mode is being executed, the deviation axial force Fv is calculated based on the small deviation Δθ, which can suppress the driver's steering operation from being hindered.

[0107] (1-8) When the target pinion angle θp* exceeds the threshold angle θie, the end-force calculation unit 72 considers the steering angle θs to have exceeded the steering angle limit and calculates the end-force Fie based on the target pinion angle θp*. When the steering angle θs exceeds the steering angle limit, by setting the end-force Fie independently of the deviation force Fv, it is possible to limit the steering operation that causes the steering wheel 5 to turn in one direction to the side where the steering wheel 3 exceeds the steering angle limit. Thus, for example, when the steering wheel 3 reaches the steering angle limit, the steering operation of the steering wheel 3 can be limited regardless of the magnitude of the deviation Δθ between the steering angle θs and the steering conversion angle θp_s.

[0108] (1-9) When the deviation axial force Fv and the end axial force Fie are calculated to be values ​​that should simultaneously generate steering reaction force, the axial force that actually reflects the target reaction torque Ts* even in this situation is the only one with the largest absolute value. Therefore, even when the deviation axial force Fv and the end axial force Fie are calculated to be values ​​that should simultaneously generate steering reaction force, it is possible to suppress excessive increase in steering reaction force.

[0109] (1-10) The steering side control unit 60, which is equipped with a rudder angle ratio variable control unit 62, has a rudder angle conversion unit 65. In this case, the function of converting using the rudder angle ratio can be integrated into the steering side control unit 60, and a structure that is easy to design in terms of designing each control unit can be realized.

[0110] (1-11) For example, when the vehicle is traveling at the aforementioned high speed, if the deviation axial force Fv is too large, there is a concern that it may affect the steering control of the steering wheel 3. According to this embodiment, when the vehicle speed value V is above the vehicle speed threshold, for example, when traveling at the aforementioned high speed, when the total axial force Ft is above the maximum value Flim, the upper limit protection processing unit 104 uses the maximum value Flim to protect the total axial force Ft. Thus, when the vehicle is traveling at, for example, the aforementioned high speed, the influence of the deviation axial force Fv on the steering control of the steering wheel 3 can be suppressed.

[0111] (1-12) Since it is only necessary to set the relationship between the deviation axial force Fv and the deviation Δθ, it is possible to suppress the increase in the storage capacity of the ROM of the steering control device 1 compared to setting the axial force separately each time.

[0112] <Second Implementation>

[0113] The second embodiment of the steering control device will be described with reference to the accompanying drawings. Here, the description will focus on the differences from the first embodiment. Furthermore, descriptions that use the same reference numerals as those in the first embodiment will be omitted.

[0114] like Figure 6 As shown, the deviation axial force calculation unit 73 of this embodiment has a first deviation axial force component calculation unit 111, a second deviation axial force component calculation unit 112, and a distribution ratio calculation unit 113 as a structure that replaces the axial force basic component calculation unit 101 and the gradient processing unit 103 of the first embodiment.

[0115] The first deviation axial force component calculation unit 111 is input with respect to the deviation Δθ obtained by subtracting the steering conversion angle θp_s from the steering control angle θs using the subtractor 106. The first deviation axial force component calculation unit 111 calculates the first deviation axial force component FΔθ1 based on the deviation Δθ. The first deviation axial force component calculation unit 111 includes a function to represent the first deviation axial force component FΔθ1. Figure 5 The axial force component of the normal pattern, represented by a double-dotted line, is mapped using the same trend. The deviation Δθ is used as input to perform the mapping operation on the first deviation axial force component FΔθ1. The first deviation axial force component FΔθ1 obtained in this way is output to multiplier 114.

[0116] The second deviation axial force component calculation unit 112 is input with respect to the deviation Δθ obtained by subtracting the steering conversion angle θp_s from the steering control angle θs using the subtractor 106. The second deviation axial force component calculation unit 112 calculates the second deviation axial force component FΔθ2 based on the deviation Δθ. The second deviation axial force component calculation unit 112 includes a function to represent the deviation Δθ. Figure 5 The protection mode, represented by solid lines, uses the same trend mapping for the axial force base component, mapping the second deviation axial force component FΔθ2 as input. The resulting second deviation axial force component FΔθ2 is then output to multiplier 115.

[0117] The code signal Sm is input to the allocation ratio calculation unit 113. The allocation ratio calculation unit 113 calculates the first allocation gain D1 based on the code signal Sm. The first allocation gain D1 is the allocation ratio of the first deviation axial force component FΔθ1 when the first deviation axial force component FΔθ1 and the second deviation axial force component FΔθ2 are allocated and added together by the specified allocation ratio described later.

[0118] The first allocation gain D1 thus obtained is multiplied by the first deviation axial force component FΔθ1 obtained by the first deviation axial force component calculation unit 111, and the final first deviation axial force component FΔθ1m obtained by multiplier 114 is output to adder 116. Furthermore, the second allocation gain D2 is calculated by subtracting the first allocation gain D1 from the "1" stored in storage unit 118 using subtractor 117. The second allocation gain D2 thus obtained is output to multiplier 115. The second allocation gain D2 is the allocation ratio of the second deviation axial force component FΔθ2 when the deviation axial force component FΔθm is obtained by allocating the first deviation axial force component FΔθ1 and the second deviation axial force component FΔθ2 and adding them together according to the specified allocation ratio described later. The second allocation gain D2 is calculated such that the sum of the second allocation gain D2 and the first allocation gain D1 is "1 (100%)". The allocation ratio of the first allocation gain D1 and the second allocation gain D2 is set to an appropriate value based on the operating conditions of the steering side motor 33, product specifications, etc. Here, storage unit 118 refers to a designated storage area of ​​a memory (not shown).

[0119] The second distribution gain D2 thus obtained is multiplied by the second deviation axial force component FΔθ2 obtained using the second deviation axial force component calculation unit 112, and the resulting second deviation axial force component FΔθ2m is obtained by multiplier 115 and output to adder 116. Furthermore, the second deviation axial force component FΔθ2m thus obtained is added to the first deviation axial force component FΔθ1m, and the resulting deviation axial force component FΔθm obtained by adder 116 at a predetermined distribution ratio is output to adder 107.

[0120] In this embodiment, the first deviation axial force component calculation unit 111, the second deviation axial force component calculation unit 112, the distribution ratio calculation unit 113, the multiplier 114, 115, the adder 116, the subtractor 117, and the storage unit 118 are equivalent to the deviation axial force component calculation unit.

[0121] Next, the allocation ratio calculation unit 113 will be described in detail. The specific setting of the allocation ratio of the first allocation gain D1 and the second allocation gain D2 is as follows. When the code signal Sm representing the code "0" is input, that is, in the normal state where the operation of the steering side motor 33 is not restricted, the allocation ratio calculation unit 113 calculates the allocation gain D1 in such a way that each allocation gain D1, D2 becomes the allocation ratio expressed by the following relationship (1).

[0122] D1:D2=1(100%):0(0%)…(1)

[0123] In this case, the first allocation gain D1 is set to "1 (100%)", and the second allocation gain D2 is set to "zero (0%)". Therefore, when the code signal Sm representing code "0" is input, it means that for the deviation axial force Fv, only the first deviation axial force component FΔθ1 of the first deviation axial force component FΔθ1 and the second deviation axial force component FΔθ2 are adopted, that is, the second deviation axial force component FΔθ2 is not adopted. That is, the allocation ratio of this embodiment includes the concept that only one of the first deviation axial force component FΔθ1 and the second deviation axial force component FΔθ2 is adopted to the zero value of the deviation axial force Fv.

[0124] The more the overheating state represented by the code signal Sm progresses in the order of "mild," "moderate," and "severe," meaning the more the steering motor 33 is in an overheated state, the smaller the first allocation gain D1 is set to in the allocation ratio calculation unit 113. In this case, the more the overheating state represented by the code signal Sm progresses in the order of "mild," "moderate," and "severe," the larger the second allocation gain D2 is set to in the allocation ratio calculation unit 113.

[0125] When the code signal Sm representing code "1A" is input, that is, when the steering motor 33 is in a slightly overheated state, the allocation ratio calculation unit 113 calculates the allocation gain D1 in such a way that each allocation gain D1, D2 becomes an allocation ratio expressed by the following relationship (2).

[0126] D1:D2=0.8(80%):0.2(20%)…(2)

[0127] When the code signal Sm representing code "1B" is input, that is, when the steering motor 33 is in a moderate overheating state, the allocation ratio calculation unit 113 calculates the allocation gain D1 in such a way that each allocation gain D1, D2 becomes an allocation ratio expressed by the following relationship (3).

[0128] D1:D2=0.2(20%):0.8(80%)…(3)

[0129] When the code signal Sm representing code "1C" is input, that is, when the steering motor 33 is in a state of severe overheating, the allocation ratio calculation unit 113 calculates the allocation gain D1 in such a way that each allocation gain D1, D2 becomes an allocation ratio expressed by the following relationship (4).

[0130] D1:D2=0(0%):1(100%)…(4)

[0131] As the voltage drop state of the DC power supply represented by the code signal Sm progresses in the order of "mild," "moderate," and "severe," the allocation ratio calculation unit 113 can set the first allocation gain D1 to a smaller value. In this case, when the code signal Sm representing code "2A" is input, the allocation ratio calculation unit 113 calculates the allocation gain D1 in the same way as when the code signal Sm representing code "1A" is input. Similarly, when the code signal Sm representing code "2B" is input, the allocation ratio calculation unit 113 calculates the allocation gain D1 in the same way as when the code signal Sm representing code "1B" is input. When the code signal Sm representing code "2C" is input, the allocation ratio calculation unit 113 calculates the allocation gain D1 in the same way as when the code signal Sm representing code "1C" is input.

[0132] The allocation ratio calculation unit 113 has the function of gradually changing the allocation gain D1 when the allocation gain D1 is changed. When the allocation gain D1 is changed, the allocation ratio calculation unit 113 performs a gradual change processing on the allocation gain D1 with respect to time. Specifically, when the code is switched, the allocation ratio calculation unit 113 gradually changes the allocation gain D1 with respect to the elapsed time in a way that changes from the value before the switch to the value after the switch. As a method for gradually changing the allocation gain D1, for example, the same method as the gradual processing unit 103 in the first embodiment described above can be used. In this case, when the code is switched, the allocation ratio calculation unit 113 obtains the deviation between the allocation gain D1 calculated before the switch and the allocation gain D1 after the switch, and calculates the deviation as an offset. In addition, the allocation ratio calculation unit 113 calculates the processed allocation gain D1 by offsetting the allocation gain D1 after the switch by an offset from the allocation gain D1 before the switch. Moreover, the allocation ratio calculation unit 113 gradually decreases the offset with respect to time so that the allocation gain D1 after any switch changes to the original value after the switch.

[0133] According to this embodiment, the functions and effects of the first embodiment are achieved. Furthermore, according to this embodiment, the following effects are achieved.

[0134] (2-1) The distribution ratio of the first deviation axial force component FΔθ1 and the second deviation axial force component FΔθ2 is changed according to whether the operation of the steering side motor 33 is restricted. Thus, an appropriate deviation axial force Fv can be calculated according to whether the operation of the steering side motor 33 is restricted.

[0135] (2-2) When the distribution ratio changes due to a switch between whether the steering side motor 33 is operating under restricted conditions, the change can be gradually reflected. Thus, during periods when the steering side motor 33 is not operating under restricted conditions, sudden changes in the deviation axial force Fv can be suppressed.

[0136] The above-described embodiments can be modified as follows. Furthermore, the following other embodiments can be combined with each other to the extent that they are not technically contradictory.

[0137] In each of the above embodiments, the rudder angle conversion unit 65 can be configured to function as the steering control side control unit 50. Furthermore, the rudder angle ratio variable control unit 62 can be configured to function as the steering control side control unit 50 in conjunction with the function of the rudder angle conversion unit 65. In this case, the effects described in the first embodiment (1-10) can be achieved.

[0138] • In the above embodiments, the axial force selection unit 74 can be omitted. In this case, for example, the axial force F can be obtained by adding the distributed axial force Fd calculated by the distributed axial force calculation unit 71, the end axial force Fie calculated by the end axial force calculation unit 72, and the deviation axial force Fv calculated by the deviation axial force calculation unit 73 through the adder 75.

[0139] In the above embodiments, the axial force calculation unit 56, in addition to having the axial force distribution calculation unit 71, the end axial force calculation unit 72, and the deviation axial force calculation unit 73, may also have the function of calculating additional axial force for conveying the condition of the steering wheel 5. In this case, the axial force selection unit 74 selects the axial force with the largest absolute value among the end axial force Fie, the deviation axial force Fv, and the additional axial force, and calculates the selected axial force as the selected axial force Fsl.

[0140] In the above embodiments, the upper control device 45 generates a drift state quantity θx, which is a value with the dimension of angle, as a turning state quantity. However, it is not limited to this; for example, it can also generate a drift state quantity with the dimension of torque as a turning state quantity. In this case, the drift state quantity with the dimension of torque is converted into a value with the dimension of angle and then output to the rudder angle conversion unit 65 as a compensated pinion angle θp′ obtained by subtracting the pinion angle θp by the subtractor 68.

[0141] • In the above embodiments, the function of calculating the drift state quantity θx can be set to the function of the steering control device 1, that is, the steering control side control unit 50 or the steering side control unit 60.

[0142] In the above embodiments, the drift state quantity θx generated by the upper control device 45 may not be input to the steering control device 1. In this case, the subtractor 68 can be removed from the steering-side control unit 60. That is, in the rudder angle conversion unit 65, the pinion angle θp calculated by the pinion angle calculation unit 61 is input, and this pinion angle θp is used in the calculation of the steering conversion angle θp_s.

[0143] In the first embodiment described above, the code signal generation unit 66 can detect mechanical abnormalities in the structure of the steering unit 6, such as the steering-side motor 33, based on the detection results from various sensors. In this case, for example, if it is determined that there is a mechanical abnormality in the steering-side motor 33, the code signal generation unit 66 generates a code signal Sm indicating that a protection mode is being executed.

[0144] In the above embodiments, the pinion angle feedback control unit 63 can perform PID control using proportional, integral, and derivative terms as feedback control for the pinion angle θp. If, in this case, the deviation axial force Fv is calculated in response to a small deviation Δθ occurring during the process of making the pinion angle θp follow the target pinion angle θp* calculated based on the steering angle θs, then, as in the above embodiments, it will only hinder the driver's steering operation.

[0145] • In the first embodiment described above, the gradient processing unit 103 can be removed from the deviation axial force calculation unit 73. In this case, regardless of the mode switching between normal mode and protection mode, the axial force basic component FΔθ calculated by the axial force basic component calculation unit 101 is output to the adder 107.

[0146] In the above embodiments, the axial force calculation unit 56 only needs to calculate at least the deviation axial force Fv as the axial force F. In this case, the end axial force calculation unit 72 can be omitted.

[0147] In the embodiments described above, the axial force viscous component calculation unit 102 can use parameters other than the steering angle velocity ωs to calculate the axial force viscous component Fω. For example, the axial force viscous component calculation unit 102 can use the vehicle speed value V to calculate the axial force viscous component Fω. In this case, for example, the axial force viscous component calculation unit 102 can have multiple mappings with different trends for the vehicle speed value V, and calculate the axial force viscous component Fω by referring to the mapping selected based on the vehicle speed value V.

[0148] In the above embodiments, the axial force viscous component calculation unit 102 can use the change in the pinion angle θp, i.e., the pinion angular velocity, instead of the steering angular velocity ωs when calculating the axial force viscous component Fω. Alternatively, the change in the target pinion angle θp*, i.e., the target pinion angular velocity, can also be used when calculating the axial force viscous component Fω. Furthermore, the change in the steering conversion angle θp_s, i.e., the steering conversion angular velocity, can be used when calculating the axial force viscous component Fω. In this modified example, the angular velocities described in the technical solution correspond to the pinion angular velocity, the target pinion angular velocity, and the steering conversion angular velocity. Furthermore, in this modified example, the steering-side control unit 60 can calculate information related to the axial force viscous component Fω and send this information to the steering control-side control unit 50.

[0149] In the above embodiments, the axial force viscous component calculation unit 102 can reflect the axial force viscous component Fω to the axial force basic component FΔθ when the deviation Δθ is less than the deviation threshold.

[0150] In the above embodiments, the axial force viscous component calculation unit 102 can be removed from the deviation axial force calculation unit 73. In this case, the adder 107 can be removed from the deviation axial force calculation unit 73. That is, the processed axial force basic component FΔθ′ calculated by the gradient processing unit 103 is output to the upper limit protection processing unit 104.

[0151] In the first embodiment described above, the axial force basic component calculation unit 101 may have one type of mapping or three or more types of mapping as axial force basic component mappings. When three or more types of mappings are used as axial force basic component mappings, the axial force basic component calculation unit 101 may, for example, use mappings corresponding to the states represented by the codes, such as mappings corresponding to code "0", mappings corresponding to codes "1A", "1B", "2A", "2B", and mappings corresponding to codes "1C", "2C", to calculate the axial force basic component FΔθ.

[0152] • In the second embodiment described above, the deviation axial force calculation unit 73 may include three or more deviation axial force component calculation units. In this case, the deviation axial force calculation unit 73 may, for example, use allocation gains corresponding to the state represented by the code, such as allocation gains corresponding to code "0", allocation gains corresponding to codes "1A", "1B", "2A", "2B", and allocation gains corresponding to codes "1C", "2C", to add three or more deviation axial force components at a predetermined allocation ratio.

[0153] • In the second embodiment described above, the sum of the first allocation gain D1 and the second allocation gain D2 can exceed "1 (100%)". This is also true for the case where the deviation axial force calculation unit 73 calculates more than 3 allocation gains as in the modified example described above, where the sum of more than 3 allocation gains can exceed "1 (100%)".

[0154] In the first embodiment described above, the axial force basic component calculation unit 101 uses deviations Δθ, where the reference angle is used as the steering control angle θs and the converted angle is used as the steering conversion angle θp_s, when calculating the axial force basic component FΔθ, but it is not limited to this. For example, when calculating the deviation Δθ, deviations such as using the reference angle as the target pinion angle θp* and the converted angle as the steering conversion angle θp_s can be used. In addition, when calculating the deviation Δθ, deviations such as using the reference angle as the value obtained by converting the steering control angle θs into an index value of the pinion angle θp based on the rudder angle ratio and using the converted angle as the pinion angle θp can be used. Furthermore, when calculating the deviation Δθ, deviations such as using the reference angle as the pinion angle θp and the converted angle as the target pinion angle θp* can also be used. In this case, the rudder angle conversion unit 65 can be deleted in the steering side control unit 60. This is also the case in the second embodiment described above.

[0155] In the above embodiments, the deviation axial force calculation unit 73 can be configured to function as the steering side control unit 60. Alternatively, in addition to the deviation axial force calculation unit 73, the axial force calculation unit 56 itself can also be configured to function as the steering side control unit 60. In this case, the axial force F calculated by the axial force calculation unit 56 provided in the steering side control unit 60 is output to the target reaction torque calculation unit 52 of the steering control side control unit 50.

[0156] In each of the above embodiments, the code signal generation unit 66 can be configured to function as the steering control side control unit 50. In this case, the detection results from the temperature sensor, voltage sensor, etc., detected by the steering control side control unit 60 are output to the code signal generation unit provided in the steering control side control unit 50.

[0157] In the second embodiment described above, the allocation ratio calculation unit 113 can calculate the first allocation gain D1 and the second allocation gain D2 based on the code signal Sm. In this case, the subtractor 117 and the storage unit 118 can be eliminated. Thus, the deviation axial force component calculation unit only needs to include at least the first deviation axial force component calculation unit 111, the second deviation axial force component calculation unit 112, and the allocation ratio calculation unit 113, and other structures can be appropriately modified.

[0158] In the first embodiment described above, the slope of the axial force base component mapping can be adjusted, for example, by increasing the slope of the axial force base component FΔθ relative to the deviation Δθ in the axial force base component mapping used in the protection mode. In this case, the first deviation threshold Δθ1 and the second deviation threshold Δθ2 can be set to the same value between the axial force base component mappings, and the dead zone of the deviation Δθ can be set to the same degree. This can also be applied to the deviation axial force component mappings in the second embodiment described above.

[0159] • In the second embodiment described above, the function of gradually changing the allocation gain D1 in the allocation ratio calculation unit 113 can be removed. In this case, regardless of code switching, the first allocation gain D1 calculated by the allocation ratio calculation unit 113 is output to the multiplier 114 and the subtractor 117.

[0160] In the first embodiment described above, we consider the possibility that multiple conditions requiring restriction of the operation of the steering motor 33 may repeatedly occur. For example, we consider the possibility that the condition requiring restriction of the operation of the steering motor 33 from the viewpoint of its heating state and the condition requiring restriction of the operation of the steering motor 33 from the viewpoint of the DC power supply voltage state may repeatedly occur. To address this situation, we can assign a priority to the codes, for example, we can prioritize the code representing the heating state of the steering motor 33 over the code representing the DC power supply voltage state. The same applies to the second embodiment.

[0161] In the first embodiment described above, the operation of the steering motor 33 can be unrestricted under mild overheating or mild voltage drop conditions. That is, the allocation of the normal mode and protection mode as the states that restrict the operation of the steering motor 33 can be appropriately changed. The same applies to the second embodiment.

[0162] In the above embodiments, when calculating the angular axial force Fr, the angle axial force calculation unit 81 only needs to use at least the target pinion angle θp*, and may not use the vehicle speed value V, or may combine other factors. Furthermore, the angle axial force calculation unit 81 can use the pinion angle θp instead of the target pinion angle θp*. This is because using the pinion angle θp and using the target pinion angle θp* are equivalent concepts.

[0163] In the above embodiments, the current axial force calculation unit 82 only needs to use at least the actual steering side current value Ib when calculating the current axial force Fi, and may also combine it with other factors such as the vehicle speed value V. Furthermore, the current axial force calculation unit 82 may use a current command value obtained to eliminate the deviation between the current value on the dq coordinate obtained by transforming the actual steering side current value Ib based on the steering side rotation angle θb, instead of the actual steering side current value Ib. This is because using the aforementioned current command value is equivalent to using the actual steering side current value Ib.

[0164] In the above embodiments, the allocation ratio calculation unit 83 may use other elements such as the vehicle speed value V instead of the vehicle speed value V, the pinion angle θp, the target pinion angle θp*, the steering angle θs, and the steering speed obtained by differentiating the pinion angle θp when calculating the allocation gain Di.

[0165] In the above embodiments, the angle axial force calculation unit 81 or the current axial force calculation unit 82 can be deleted from the axial force calculation unit 71. In this case, the allocation ratio calculation unit 83 can also be deleted. Furthermore, the angle axial force Fr calculated by the angle axial force calculation unit 81 or the current axial force Fi calculated by the current axial force calculation unit 82 is output to the adder 75.

[0166] In the above embodiments, the end-axis force calculation unit 72 can combine other factors such as the vehicle speed value V when calculating the end-axis force Fie. Furthermore, the end-axis force calculation unit 72 can also use the pinion angle θp instead of the target pinion angle θp*. This is because using the pinion angle θp and using the target pinion angle θp* are equivalent concepts.

[0167] In the above embodiments, when the steering force calculation unit 55 calculates the steering force Tb*, it is sufficient to use at least the state variable related to the movement of the steering wheel 3; the vehicle speed value V may not be used, and other elements may be used in combination. As the state variable related to the movement of the steering wheel 3, the steering angle θs or other elements may be used instead of the steering torque Th exemplified in the above embodiments.

[0168] • In the above embodiments, the steering side control unit 60 may be additionally configured to function as the steering operation side control unit 50.

[0169] In the above embodiments, the steering motor 33 may, for example, be configured with the steering motor 33 coaxially mounted on the rack shaft 22, or be connected to the rack shaft 22 via a belt reducer using a ball screw mechanism.

[0170] In the above embodiments, the steering control device 1 can be composed of a processing circuit including 1) one or more processors that operate according to a computer program (software), 2) one or more dedicated hardware circuits such as an application-specific integrated circuit (ASIC) that performs at least a portion of various processes, or 3) a combination of these. The processor includes a CPU and memories such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. Memory, i.e., non-transitory computer-readable media, includes all available media that can be accessed by a general-purpose or special-purpose computer.

[0171] • In the above embodiments, the steering control device 2 is a linkageless structure in which the steering control part 4 and the steering part 6 are always mechanically separated, but it is not limited to this and can also be as follows: Figure 1 As shown by the double-dotted line, the steering control unit 4 and the steering unit 6 are mechanically separated by the clutch 25.

Claims

1. A steering control device configured to control a steering mechanism having a separate power transmission path between a steering control unit (4) connected to a steering wheel (3) and a steering unit (6) that operates via a steering shaft to turn the steering wheels according to steering input to the steering control unit (4), and having the function of changing the ratio of the rotation of the steering wheels to the rotation of the steering wheel (3), i.e., the rudder angle ratio. The steering control device is characterized in that... The steering control device includes a control unit that controls at least the operation of the steering control side motor (13) disposed in the steering control unit (4) to generate a force that resists the steering input to the steering control unit (4), i.e., a steering reaction force. in, The control unit is configured as follows: The target reaction force torque is calculated as the motor torque of the steering control side motor (13) that becomes the steering control reaction force. The calculation reflects the deviation axial force in the target reaction torque, used to limit the steering operation that causes the steering wheels to turn in a specified direction. The angle between the steering angle set to represent the value of the rotation of the steering wheel (3) and the steering angle set to represent the value of the rotation of the steering wheel is used as a reference angle, and the angle obtained by converting the steering angle and the other steering angle according to the rudder angle ratio is used as a conversion angle. The deviation axial force is calculated based on the deviation between the reference angle and the conversion angle. The control unit is input a turning state quantity that is set to represent the difference between the actual turning action of the vehicle and the ideal turning action of the vehicle. The control unit is configured to calculate the deviation using the steering angle after compensation based on the turning state quantity.

2. The steering control device according to claim 1, characterized in that, The control unit is configured as follows: The deviation axial force component is calculated based on the deviation between the reference angle and the converted angle. In order to adjust for the change in the deviation axial force, the viscous component of the axial force is calculated based on the angular velocity, which is the amount of change of the reference angle or the conversion angle. The deviation axial force is obtained by making the deviation axial force component reflect the viscous component of the axial force.

3. The steering control device according to claim 1, characterized in that, The control unit calculation includes a first deviation axial force component obtained based on the deviation and a second deviation axial force component obtained based on the deviation in a manner having characteristics different from the first deviation axial force component. The control unit is configured to incorporate either the first deviation axial force component or the second deviation axial force component into the deviation axial force, depending on whether the operation of the steering side motor (33) provided in the steering unit (6) is not restricted or is restricted.

4. The steering control device according to claim 3, characterized in that, The control unit is configured to gradually reduce the difference between the first deviation axial force component and the second deviation axial force component before and after switching which one of the first deviation axial force component and the second deviation axial force component is adopted into the deviation axial force when the operation of the steering side motor (33) is switched between a state where the operation is not restricted and a state where the operation is restricted.

5. The steering control device according to claim 1, characterized in that, The control unit will add together a plurality of deviation axial force components, including a first deviation axial force component obtained based on the deviation and a second deviation axial force component obtained based on the deviation in a manner having characteristics different from the first deviation axial force component, at a predetermined distribution ratio. The control unit is configured to change the distribution ratio based on whether the operation of the steering side motor (33) provided in the steering unit (6) is not restricted or the operation is restricted, and to incorporate the deviation axial force component obtained by adding the distribution ratio into the deviation axial force.

6. The steering control device according to claim 5, characterized in that, The control unit is configured to gradually change the allocation ratio when the allocation ratio changes due to a switch between a state where the operation of the steering side motor (33) is not restricted and a state where the operation is restricted.

7. The steering control device according to claim 3, characterized in that, The control unit is configured to set the slope of the deviation axial force component relative to the deviation to be larger when the absolute value of the deviation is above a deviation threshold than when the absolute value of the deviation is below the deviation threshold. The control unit is configured to set the absolute value of the deviation threshold to be smaller when the operation of the steering side motor (33) is restricted than when the operation of the steering side motor (33) is not restricted.

8. The steering control device according to claim 1, characterized in that, The control unit calculates the end-axis force used to limit steering maneuvers in directions exceeding the steering angle limit. The control unit is configured to have the function of calculating the deviation axial force and the end axial force respectively.

9. The steering control device according to claim 8, characterized in that, The control unit selects the axial force with the largest absolute value among a plurality of axial forces, including the deviation axial force and the end axial force. The control unit is configured to obtain the target reaction torque by reflecting the selected axial force.

10. The steering control device according to any one of claims 1 to 9, characterized in that, The control unit is configured to perform reaction force control to generate the steering reaction force by driving control of the steering control side motor (13), and to perform steering control to turn the steering wheels by driving control of the steering control side motor (33) provided in the steering unit (6). The control unit is configured to control the change of the steering angle ratio based on a vehicle speed value that is set to represent the vehicle's travel speed, and to calculate a steering conversion angle that converts the steering angle into the steering control angle according to the steering angle ratio. The reference angle is the steering angle. The conversion angle is the turning conversion angle.

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