Steering control device and steering control system

Abstract

The present invention discloses a steering control device and a steering control system. The steering control device (1) includes: a target torque generator (72) configured to generate a target torque as a target value of the motor torque; and a control signal generator configured to generate a control signal for controlling the motor to generate a motor torque corresponding to the target torque. The target torque generator (72) includes a pre-adjustment axial force calculator (101), a first axial force calculator (102), a second axial force calculator (103), a post-adjustment axial force calculator (104), and a target torque calculator (93). The post-adjustment axial force calculator (104) is configured to set the ratio of the contribution of the first axial force to the post-adjustment axial force to be smaller when the vehicle speed is in an abnormal state than when the vehicle speed is in a normal state.

Description

Technical Field

[0001] The present invention relates to a steering control device and a steering control system. Background Art

[0002] There is known a steer-by-wire steering control system in which a power transmission path between a steering control unit connected to a steering wheel and a steering unit that steers a steered wheel is cut off. In this type of steering control system, road surface reaction forces applied to the steered wheel are not mechanically transmitted to the steering wheel. Therefore, a steering control device that controls this type of steering control system calculates a target value of a steering reaction force applied to the steering wheel in consideration of road surface reaction forces and the like.

[0003] For example, the steering control device described in WO 2013 / 061567 calculates a plurality of types of calculated axial forces corresponding to an axial force acting on a steering shaft connected to a steered wheel based on various state quantities focused on axial force. The steering control device calculates a target steering reaction force based on an allocated axial force obtained by summing the plurality of types of calculated axial forces with separately set allocation ratios. Summary of the Invention

[0004] Some components used as a basis for calculating a target steering reaction force are calculated based on a vehicle speed. For example, the allocated axial force described in WO 2013 / 061567. Therefore, when the detected vehicle speed has an incorrect value, for example, due to an abnormality occurring in a sensor that detects the vehicle speed, the component used as a basis for the target steering reaction force may have an abnormal value. As a result, the target steering reaction force may become different from an appropriate value corresponding to the running state of the vehicle.

[0005] This problem is not limited to the case of controlling a steer-by-wire steering control system that applies motor torque as a steering reaction force. For example, as described in Japanese Unexamined Patent Application Publication No. 2016-144974, when a steering control device that controls an electric power steering control system that applies motor torque as an auxiliary force calculates a component used as a basis for calculating a target value of the auxiliary force based on a vehicle speed, this problem may similarly occur.

[0006] The present invention provides a steering control device and a steering control system that can prevent a target torque from becoming different from an appropriate value.

[0007] According to a first aspect of the present invention, a steering control device is provided. The steering control device is configured to control a steering system that changes a steering torque required for steering a steering wheel using a motor torque applied from a motor. The steering control device includes: a target torque generator configured to generate a target torque that is a target value of the motor torque; and a control signal generator configured to generate a control signal for controlling the motor so as to generate a motor torque corresponding to the target torque. The target torque generator includes: a pre-adjustment axial force calculator configured to calculate a pre-adjustment axial force corresponding to an axial force acting on a steering shaft connected to a steering wheel; a first axial force calculator configured to calculate a first axial force by adjusting the pre-adjustment axial force using a vehicle speed; a second axial force calculator configured to calculate a second axial force by adjusting the pre-adjustment axial force without using the vehicle speed; a post-adjustment axial force calculator configured to calculate a post-adjustment axial force based on the first axial force and the second axial force; and a target torque calculator configured to calculate a target torque based on the post-adjustment axial force. The post-adjustment axial force calculator is configured to set a ratio of a contribution of the first axial force to the post-adjustment axial force to be smaller when the vehicle speed is in an abnormal state than when the vehicle speed is in a normal state.

[0008] With this configuration, when the vehicle speed is in an abnormal state, the ratio of the contribution of the first axial force that has been adjusted using the vehicle speed to the post-adjustment axial force is reduced. The target torque is calculated based on the post-adjustment axial force in which the ratio of the contribution from the first axial force is reduced. Therefore, it is possible to prevent the target torque from becoming different from an appropriate value corresponding to the driving state of the vehicle.

[0009] In this steering control device, the post-adjustment axial force calculator may be configured to calculate the post-adjustment axial force by summing the first axial force and the second axial force at a separately set predetermined distribution ratio. The post-adjustment axial force calculator may be configured to set the distribution ratio of the first axial force to be smaller when the vehicle speed is in an abnormal state than when the vehicle speed is in a normal state.

[0010] In this steering control device, the post-adjustment axial force calculator may be configured to switch an effective calculation system to a first calculation system or a second calculation system, where the first calculation system is a calculation system including the first axial force calculator, and the second calculation system is a calculation system including the second axial force calculator. The post-adjustment axial force calculator may be configured to output the first axial force as the post-adjustment axial force by making the first calculation system effective when the vehicle speed is in a normal state. The post-adjustment axial force calculator may be configured to output the second axial force as the post-adjustment axial force by making the second calculation system effective when the vehicle speed is in an abnormal state.

[0011] In the steering control device, the adjusted axial force calculator may be configured to: when switching the effective calculation system from the first calculation system to the second calculation system, slowly change the value of the adjusted axial force from the value of the first axial force to the value of the second axial force.

[0012] With this configuration, when the vehicle speed is in an abnormal state, the value of the adjusted axial force slowly changes from the value of the first axial force to the value of the second axial force. Therefore, compared with the case where the value of the adjusted axial force immediately changes from the value of the first axial force to the value of the second axial force when the vehicle speed is in an abnormal state, a sharp change in the adjusted axial force can be suppressed. Therefore, a sharp change in the target torque can be suppressed and a deterioration in the feeling of steering operation can be prevented.

[0013] In the steering control device, the first axial force calculator may be configured to adjust the pre-adjustment axial force such that the first axial force is equal to or less than a first upper limit value based on the vehicle speed. The second axial force calculator may be configured to adjust the pre-adjustment axial force such that the second axial force is equal to or less than a second upper limit value.

[0014] With this configuration, for example, even when the pre-adjustment axial force becomes too large due to a sensor abnormality, the adjusted axial force can be prevented from becoming too large. Therefore, the target torque can be prevented from becoming an abnormal value.

[0015] According to a second aspect of the present invention, a steering control system is provided. The steering control system includes: an electric motor; a steering control unit connected to a steering wheel; a steering unit configured to steer a steering wheel, and a power transmission path between the steering control unit and the steering unit is cut off; and a steering control device. The electric motor is a steering control side electric motor that applies a motor torque as a steering reaction force against the steering operation input to the steering control unit. The steering control device includes: a target torque generator configured to generate a target torque as a target value of the motor torque; and a control signal generator configured to generate a control signal for controlling the electric motor so as to generate a motor torque corresponding to the target torque. The target torque generator includes: an axial force calculator before adjustment configured to calculate an axial force before adjustment corresponding to an axial force acting on a steering shaft connected to the steering wheel; a first axial force calculator configured to calculate a first axial force by adjusting the axial force before adjustment using a vehicle speed; a second axial force calculator configured to calculate a second axial force by adjusting the axial force before adjustment without using the vehicle speed; an axial force calculator after adjustment configured to calculate an axial force after adjustment based on the first axial force and the second axial force; and a target torque calculator configured to calculate a target torque based on the axial force after adjustment. The target torque generator is configured to generate a target reaction torque as a target value of the steering reaction force as the target torque. The axial force calculator after adjustment is configured to set a ratio of the contribution of the first axial force to the axial force after adjustment to be smaller when the vehicle speed state is abnormal than when the vehicle speed state is normal.

[0016] According to these aspects, it is possible to prevent the target torque from becoming different from an appropriate value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, in which like reference numerals denote like elements, and in the drawings:

[0018] Figure 1 is a diagram schematically showing a configuration of a steering control system according to a first embodiment;

[0019] Figure 2 is a block diagram showing a steering control device according to a first embodiment;

[0020] Figure 3 is a block diagram showing a target reaction torque generation unit according to a first embodiment; and

[0021] Figure 4 is a block diagram showing a target reaction torque generation unit according to a second embodiment. Detailed Implementation Manner

[0022] First Embodiment

[0023] Hereinafter, a steering control device according to a first embodiment will be described with reference to the accompanying drawings. As Figure 1 shown, a steering system 2 controlled by a steering control device 1 is configured as a steer-by-wire system. The steering system 2 includes: a steering operation unit 4 that a driver steers by using a steering wheel 3; and a steering unit 6 that steers a steering wheel 5 according to the driver's steering operation of the steering operation unit 4.

[0024] The steering operation unit 4 includes: a steering operation shaft 11 connected to the steering wheel 3; and a steering operation side actuator 12 that applies a steering operation reaction force as a force resisting the steering operation of the steering wheel 3.

[0025] The steering operation side actuator 12 includes a steering operation side motor 13 and a steering operation side reduction gear 14. For example, a three-phase surface permanent magnet synchronous motor is used as the steering operation side motor 13. For example, a worm gear mechanism is used as the steering operation side reduction gear 14. The steering operation side motor 13 is connected to the steering operation shaft 11 via the steering operation side reduction gear 14. Therefore, the motor torque of the steering operation side motor 13 is applied to the steering wheel 3 as a steering operation reaction force via the steering operation shaft 11.

[0026] The steering unit 6 includes: a pinion shaft 21; a rack shaft 22 as a steering shaft connected to the pinion shaft 21; a rack housing 23 that houses the rack shaft 22 so that the rack shaft 22 can reciprocate; and a rack-and-pinion mechanism 24 including the pinion shaft 21 and the rack shaft 22. The pinion shaft 21 and the rack shaft 22 are arranged in the rack housing 23 at a predetermined crossing angle. The rack-and-pinion mechanism 24 has a structure in which pinion teeth 21a formed in the pinion shaft 21 mesh with rack teeth 22a formed in the rack shaft 22. Therefore, the pinion shaft 21 rotates as the rack shaft 22 reciprocates. Tie rods 26 are connected to both ends of the rack shaft 22 via ball joints 25. The ends of the tie rods 26 are connected to a steering knuckle (not shown), and the steering wheel 5 is assembled to the steering knuckle.

[0027] The steering unit 6 includes a steering-side actuator 31 that applies a steering force as a force for steering the steering wheel 5. The steering-side actuator 31 includes a steering-side motor 32, a transmission mechanism 33, and a conversion mechanism 34. For example, a three-phase surface permanent magnet synchronous motor is used as the steering-side motor 32. For example, a belt mechanism is used as the transmission mechanism 33. For example, a ball screw mechanism is used as the conversion mechanism 34. The motor torque of the steering-side motor 32 is transmitted to the conversion mechanism 34 via the transmission mechanism 33. The conversion mechanism 34 converts the transmitted torque into a translational motion of the rack shaft 22. Accordingly, the steering-side actuator 31 applies a steering force to the steering unit 6.

[0028] In the steering control system 2 having the above configuration, a steering force is applied from the steering-side actuator 31 according to the driver's steering operation. Accordingly, the rack shaft 22 reciprocates and the steering angle of the steering wheel 5 changes. At this time, a steering reaction force against the driver's steering operation is applied from the steering control-side actuator 12 to the steering wheel 3. That is, in the steering control system 2, the steering torque Th required for steering the steering wheel 3 changes according to the motor torque applied as the steering reaction force from the steering control-side motor 13.

[0029] The electrical configuration according to this embodiment will be described below. The steering control device 1 is connected to the steering control-side motor 13 and the steering-side motor 32 and operates the steering control-side motor 13 and the steering-side motor 32.

[0030] The steering control device 1 may be configured to include the following processing circuits: (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 perform at least some of the various processes; or (3) a combination of the above two. The processor includes a central processing unit (CPU) and a memory such as RAM and ROM, and the memory stores program codes or commands configured to cause the CPU to execute processes. The memory, i.e., the non-transitory computer-readable medium, includes all available media that can be accessed by a general-purpose computer or a dedicated computer. The steering control device 1 executes various types of control by causing the CPU to execute the programs stored in the memory in each predetermined operation cycle.

[0031] The detection results from various sensors are input to the steering control device 1. The various sensors include, for example, a torque sensor 41, a steering-side rotation angle sensor 42, and a steered-side rotation angle sensor 43. The torque sensor 41 detects the steering torque Th applied to the steering shaft 11. For example, when the steering wheel is turned to the right, the steering torque Th is detected as a positive value, and when the steering wheel is turned to the left, the steering torque Th is detected as a negative value. The steering-side rotation angle sensor 42 detects the rotation angle θs of the rotation shaft 13a of the steering-side motor 13 as a relative angle within 360°. The steered-side rotation angle sensor 43 detects the rotation angle θt of the rotation shaft 32a of the steered-side motor 32 as a relative angle.

[0032] The steering control device 1 is communicatively connected to a brake control device 51 provided outside the steering control device 1. The brake control device 51 is a device that operates a brake device (not shown). The brake control device 51 calculates the vehicle speed Vb of the vehicle body when the brake device is activated. Specifically, a left front wheel sensor 52l, a right front wheel sensor 52r, a left rear wheel sensor 53l, and a right rear wheel sensor 53r are connected to the brake control device 51. The left front wheel sensor 52l and the right front wheel sensor 52r are provided in a wheel hub unit 54 that rotatably supports the steering wheel 5 via a drive shaft (not shown). The left front wheel sensor 52l detects the wheel speed Vfl of the left steering wheel 5, the right front wheel sensor 52r detects the wheel speed Vfr of the right steering wheel 5, the left rear wheel sensor 53l detects the wheel speed Vrl of a left rear wheel (not shown), and the right rear wheel sensor 53r detects the wheel speed Vrr of a right rear wheel (not shown). For example, the brake control device 51 calculates the average value of the wheel speeds Vfl, Vfr, Vrl, and Vrr as the vehicle speed Vb. The calculated vehicle speed Vb is output to the steering control device 1.

[0033] The brake control device 51 determines whether the state of the detected vehicle speed Vb is normal. For example, when the wheel speeds Vfl, Vfr, Vrl, and Vrr output from the left front wheel sensor 52l, the right front wheel sensor 52r, the left rear wheel sensor 53l, and the right rear wheel sensor 53r are unavailable values or when the change relative to the previous value is greater than a preset threshold, the brake control device 51 determines that the state of the vehicle speed Vb is abnormal. For example, when at least one of the drive voltages supplied to the left front wheel sensor 52l, the right front wheel sensor 52r, the left rear wheel sensor 53l, and the right rear wheel sensor 53r decreases, the brake control device 51 determines that the state of the vehicle speed Vb is abnormal. The brake control device 51 generates a vehicle speed state signal Sve indicating the determination result of the state of the vehicle speed Vb. The generated vehicle speed state signal Sve is output to the steering control device 1.

[0034] The steering control device 1 controls the operations of the steering-side motor 13 and the steered-side motor 32 based on the state quantities input from the sensors and the brake control device 51. The configuration of the steering control device 1 will be described in more detail below.

[0035] As Figure 2 shown, the steering control device 1 includes: a steering-side microcomputer 61 that outputs a steering-side motor control signal Ms; and a steering-side drive circuit 62 that supplies drive power to the steering-side motor 13 based on the steering-side motor control signal Ms. A current sensor 64 in a connection line 63 provided between the steering-side drive circuit 62 and the phase motor coil of the steering-side motor 13 is connected to the steering-side microcomputer 61. The current sensor 64 detects the phase current values Ius, Ivs, and Iws of the steering-side motor 13 flowing in the connection line 63. In Figure 2 the description, for the purpose of convenience, each of the phase connection lines 63 is commonly shown as one phase connection line 63, and each of the phase current sensors 64 is commonly shown as one phase current sensor 64.

[0036] The steering control device 1 includes: a steered-side microcomputer 66 that outputs a steered-side motor control signal Mt; and a steered-side drive circuit 67 that supplies drive power to the steered-side motor 32 based on the steered-side motor control signal Mt. A current sensor 69 in a connection line 68 provided between the steered-side drive circuit 67 and the phase motor coil of the steered-side motor 32 is connected to the steered-side microcomputer 66. The current sensor 69 detects the phase current values Iut, Ivt, and Iwt of the steered-side motor 32 flowing in the connection line 68. In Figure 2 the description, for the purpose of convenience, one phase connection line 68 of each of the phase connection lines 68 is commonly shown, and one phase current sensor 69 of each of the phase current sensors 69 is commonly shown.

[0037] For example, the steering-side drive circuit 62 and the steered-side drive circuit 67 employ a known PWM inverter including a plurality of switching elements such as FETs. The steering-side motor control signal Ms and the steered-side motor control signal Mt are gate on / off signals for specifying the on / off states of the switching elements.

[0038] When the steering operation side motor control signal Ms is output to the steering operation side drive circuit 62, drive power from the vehicle-mounted power supply B is supplied to the steering operation side motor 13. In this way, the steering control device 1 controls the motor torque generated by the steering operation side motor 13 by supplying drive power to the steering operation side motor 13. When the steering side motor control signal Mt is output to the steering side drive circuit 67, drive power from the vehicle-mounted power supply B is supplied to the steering side motor 32. In this way, the steering control device 1 controls the motor torque generated by the steering side motor 32 by supplying drive power to the steering side motor 32.

[0039] The configuration of the steering operation side microcomputer 61 will be described below. The steering operation side microcomputer 61 outputs the steering operation side motor control signal Ms by executing operation processing indicated by the following control blocks at intervals of a predetermined operation cycle. The steering operation torque Th, vehicle speed Vb, vehicle speed state signal Sve, rotation angle θs, phase current values Ius, Ivs, and Iws, the steering corresponding angle θp which is the rotation angle of the pinion shaft 21 and will be described later, and the q-axis current value Iqt which is the drive current of the steering side motor 32 are input to the steering operation side microcomputer 61. Then, the steering operation side microcomputer 61 outputs the steering operation side motor control signal Ms based on these state quantities.

[0040] Specifically, the steering operation side microcomputer 61 includes: a steering operation angle calculation unit 71 that calculates the steering operation angle θh of the steering wheel 3; a target reaction torque generation unit 72 that generates a target reaction torque Ts* which is a target value of the steering reaction force; and a steering operation side motor control signal generation unit 73 that generates the steering operation side motor control signal Ms.

[0041] The rotation angle θs of the steering operation side motor 13 is input to the steering operation angle calculation unit 71. The steering operation angle calculation unit 71 calculates the total angle, for example, by counting the number of rotations of the steering operation side motor 13 starting from the steering operation midpoint and summing the rotation angle θs with the steering operation midpoint as the origin. The steering operation midpoint is the steering operation angle θh when the steering wheel 3 is at the center of the steerable range. The steering operation angle calculation unit 71 calculates the steering operation angle θh by multiplying the total angle by a conversion factor based on the rotation speed ratio of the steering operation side reduction gear 14. For example, when the steering operation angle θh is an angle to the right of the steering operation midpoint, the steering operation angle θh is calculated as a positive value, and when the steering operation angle θh is an angle to the left of the steering operation midpoint, the steering operation angle θh is calculated as a negative value. The calculated steering operation angle θh is output to the steering side microcomputer 66.

[0042] The steering operation torque Th, vehicle speed Vb, vehicle speed state signal Sve, steering corresponding angle θp, and q-axis current value Iqt are input to the target reaction torque generation unit 72. As will be described later, the target reaction torque generation unit 72 generates a target reaction torque Ts* based on these state quantities and outputs the generated target reaction torque Ts* to the steering operation side motor control signal generation unit 73. The target reaction torque Ts* corresponds to the target torque of the steering operation side motor 13, and the target reaction torque generation unit 72 corresponds to the target torque generator.

[0043] In addition to the target reaction torque Ts*, the rotation angle θs and the phase current values Ius, Ivs, and Iws are also input to the steering operation side motor control signal generation unit 73. The steering operation side motor control signal generation unit 73 calculates a d-axis target current value Ids* on the d-axis and a q-axis target current value Iqs* on the q-axis in the d / q coordinate system based on the target reaction torque Ts*. The d-axis target current value Ids* represents the target current value on the d-axis. The q-axis target current value Iqs* represents the target current value on the q-axis.

[0044] Specifically, the steering operation side motor control signal generation unit 73 calculates the q-axis target current value Iqs* such that its absolute value increases as the absolute value of the target reaction torque Ts* increases. In this embodiment, the d-axis target current value Ids* on the d-axis is basically set to zero.

[0045] The steering operation side motor control signal generation unit 73 generates a steering operation side motor control signal Ms that is output to the steering operation side drive circuit 62 by performing a current feedback operation in the d / q coordinate system. The steering operation side motor control signal generation unit 73 performs a PID control operation as an example of the current feedback operation. Hereinafter, the word "feedback" can be replaced by "F / B".

[0046] Specifically, the steering operation side motor control signal generation unit 73 calculates the d-axis current value Ids and the q-axis current value Iqs, which are the actual current values of the steering operation side motor 13 in the d / q coordinate system, by mapping the phase current values Ius, Ivs, and Iws to the d / q coordinates based on the rotation angle θs. The steering operation side motor control signal generation unit 73 calculates a target voltage value based on the current differences on the d-axis and q-axis such that the d-axis current value Ids follows the d-axis target current value Ids* and the q-axis current value Iqs follows the q-axis target current value Iqs*. The steering operation side motor control signal generation unit 73 generates a steering operation side motor control signal Ms with a duty ratio based on the target voltage value.

[0047] The calculated steering-side motor control signal Ms is output to the steering-side drive circuit 62. Accordingly, drive power corresponding to the steering-side motor control signal Ms is supplied from the steering-side drive circuit 62 to the steering-side motor 13. The steering-side motor 13 applies the motor torque indicated by the target reaction torque Ts* as a steering reaction force to the steering wheel 3.

[0048] The configuration of the steering-side microcomputer 66 will be described below. The steering-side microcomputer 66 outputs a steering-side motor control signal Mt by executing operation processes indicated by the following control blocks at intervals of a predetermined operation cycle. The vehicle speed Vb, the rotation angle θt, the steering operation angle θh, and the phase current values Iut, Ivt, and Iwt of the steering-side motor 32 are input to the steering-side microcomputer 66. Then, the steering-side microcomputer 66 generates a steering-side motor control signal Mt based on these state quantities and outputs the generated steering-side motor control signal Mt.

[0049] Specifically, the steering-side microcomputer 66 includes: a steering-corresponding angle calculation unit 81 that calculates a steering-corresponding angle θp; a target steering torque generation unit 82 that generates a target steering torque Tt* as a target value of the steering force; and a steering-side motor control signal generation unit 83 that generates a steering-side motor control signal Mt.

[0050] The rotation angle θt of the steering-side motor 32 is input to the steering-corresponding angle calculation unit 81. The steering-corresponding angle calculation unit 81 calculates the total angle, for example, by counting the number of rotations of the steering-side motor 32 with respect to a steering-corresponding angle midpoint used as an origin and summing up the rotation angle θt. The steering-corresponding angle midpoint is the rotation angle of the pinion shaft 21 when the vehicle is traveling straight. The steering-corresponding angle calculation unit 81 calculates the steering-corresponding angle θp by multiplying the total angle by a conversion factor based on the reduction ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack-and-pinion mechanism 24. That is, the steering-corresponding angle θp corresponds to the pinion angle that is the rotation angle of the pinion shaft 21. The calculated steering-corresponding angle θp is output to the target reaction torque generation unit 72 and the target steering torque generation unit 82.

[0051] The vehicle speed Vb, the steering operation angle θh, and the steering-corresponding angle θp are input to the target steering torque generation unit 82. The target steering torque generation unit 82 includes: a target steering-corresponding angle calculation unit 84 that calculates a target steering-corresponding angle θp* as a target value of the steering-corresponding angle θp; and a target steering torque calculation unit 85 that calculates the target steering torque Tt*.

[0052] Specifically, the vehicle speed Vb and the steering operation angle θh are input to the target steering corresponding angle calculation unit 84. The target steering corresponding angle calculation unit 84 calculates the target steering corresponding angle θp* based on the vehicle speed Vb and the steering operation angle θh. For example, the target steering corresponding angle calculation unit 84 calculates the target steering corresponding angle θp* by dividing the steering operation angle θh by the gear ratio that varies according to the steering operation angle θh and the vehicle speed Vb. That is, the steering control device 1 according to this embodiment changes the steering operation angle ratio that is the ratio of the steering corresponding angle θp to the steering operation angle θh according to the vehicle speed.

[0053] The angle difference Δθp obtained by subtracting the steering corresponding angle θp from the target steering corresponding angle θp* by the subtractor 86 is input to the target steering torque calculation unit 85. The target steering torque calculation unit 85 calculates the target steering torque Tt* by performing an angle F / B operation that makes the steering corresponding angle θp follow the target steering corresponding angle θp*. The target steering torque calculation unit 85 performs a PID control operation as an example of the angle F / B operation. The calculated target steering torque Tt* is output to the steering side motor control signal generation unit 83.

[0054] In addition to the target steering torque Tt*, the rotation angle θt and the phase current values Iut, Ivt, and Iwt are also input to the steering side motor control signal generation unit 83. The steering side motor control signal generation unit 83 calculates the d-axis target current value Idt* on the d-axis and the q-axis target current value Iqt* on the q-axis in the d / q coordinate system based on the target steering torque Tt*. Specifically, the steering side motor control signal generation unit 83 calculates the q-axis target current value Iqt* such that its absolute value increases as the absolute value of the target steering torque Tt* increases. In this embodiment, the d-axis target current value Idt* on the d-axis is basically set to zero. Similar to the steering operation side motor control signal generation unit 73, the steering side motor control signal generation unit 83 generates the steering side motor control signal Mt output to the steering side drive circuit 67 by performing current F / B control in the d / q coordinate system. The q-axis current value Iqt calculated during the generation of the steering side motor control signal Mt is output to the target reaction torque generation unit 72.

[0055] The calculated steering side motor control signal Mt is output to the steering side drive circuit 67. Therefore, the drive power corresponding to the steering side motor control signal Mt is supplied from the steering side drive circuit 67 to the steering side motor 32. Then, the steering side motor 32 applies the motor torque indicated by the target steering torque Tt* as the steering force to the steering wheel 5.

[0056] The configuration of the target reaction torque generation unit 72 will be described below. As Figure 3As shown, the target reaction torque generation unit 72 includes: an input torque base component calculation unit 91 that calculates an input torque base component Tb; an axial component calculation unit 92 that calculates an adjusted axial force Fir, which will be described later as an axial component; and a subtractor 93 as a target torque calculator. The input torque base component Tb is a force for rotating the steering wheel 3 in the steering operation direction of the driver. The adjusted axial force Fir is a force that resists the rotation of the steering wheel 3 steered by the driver, that is, the axial force acting on the rack shaft 22 from the steering wheel 5.

[0057] Specifically, the steering operation torque Th is input to the input torque base component calculation unit 91. The input torque base component calculation unit 91 calculates the input torque base component Tb such that its absolute value increases as the absolute value of the steering operation torque Th increases. The calculated input torque base component Tb is output to the subtractor 93.

[0058] The q-axis current value Iqt of the steering-side motor 32, the steering corresponding angle θp, the vehicle speed Vb, and the vehicle speed state signal Sve are input to the axial component calculation unit 92. As will be described later, the axial component calculation unit 92 calculates the adjusted axial force Fir corresponding to the axial force acting on the rack shaft 22 based on these state quantities. The adjusted axial force Fir corresponds to the calculated axial force obtained by estimating the axial force acting on the rack shaft 22. The calculated adjusted axial force Fir is output to the subtractor 93.

[0059] The subtractor 93 calculates the target reaction torque Ts* by subtracting the adjusted axial force Fir as an axial component from the input torque base component Tb. The calculated target reaction torque Ts* is output to the steering operation side motor control signal generation unit 73.

[0060] As described above, the target reaction torque generation unit 72 calculates the target reaction torque Ts* based on the adjusted axial force Fir as the calculated axial force. Therefore, the steering reaction force applied from the steering operation side motor 13 is basically a force that resists the steering operation of the driver, but can also be a force that assists the driver's steering operation depending on the difference between the calculated axial force and the actual axial force acting on the rack shaft 22.

[0061] The axial component calculation unit 92 will be described below. The axial component calculation unit 92 includes an unadjusted axial force calculation unit 101, a first axial force calculation unit 102, a second axial force calculation unit 103, and an adjusted axial force calculation unit 104.

[0062] Specifically, the q-axis current value Iqt, the steering corresponding angle θp, and the vehicle speed Vb of the steering-side motor 32 are input to the pre-adjustment axial force calculation unit 101. The pre-adjustment axial force calculation unit 101 calculates the pre-adjustment axial force Fds based on these state quantities. The pre-adjustment axial force Fds is a calculated axial force corresponding to the axial force acting on the rack shaft 22. The pre-adjustment axial force calculation unit 101 according to this embodiment calculates the distributed axial force obtained by summing multiple types of calculated axial forces at a separately set predetermined distribution ratio as the pre-adjustment axial force Fds.

[0063] Specifically, the pre-adjustment axial force calculation unit 101 includes: an angle axial force calculation unit 111 that calculates the angle axial force Fib; and a current axial force calculation unit 112 that calculates the current axial force Fer. The magnitudes (dimensions) of the angle axial force Fib and the current axial force Fer are, for example, torques (N·m) around the pinion shaft. The pre-adjustment axial force calculation unit 101 includes a distribution calculation unit 113 that sums the angle axial force Fib and the current axial force Fer at a separately set predetermined distribution ratio.

[0064] The steering corresponding angle θp and the vehicle speed Vb are input to the angle axial force calculation unit 111. The angle axial force calculation unit 111 calculates the angle axial force Fib based on the steering corresponding angle θp and the vehicle speed Vb. The angle axial force Fib is the ideal value of the axial force in the preset model. Therefore, the angle axial force Fib does not include road surface information, such as fine unevenness that does not affect the vehicle's behavior in the lateral direction or step portions that affect the vehicle's behavior in the lateral direction.

[0065] Specifically, the angle axial force calculation unit 111 calculates the angle axial force Fib such that its absolute value increases as the absolute value of the steering corresponding angle θp increases. The angle axial force calculation unit 111 calculates the angle axial force Fib such that its absolute value increases as the vehicle speed Vb increases. The calculated angle axial force Fib is output to the distribution calculation unit 113.

[0066] The q-axis current value Iqt of the steering-side motor 32 is input to the current axial force calculation unit 112. The current axial force calculation unit 112 calculates the axial force acting on the rack shaft 22 via the steering wheel 5 based on the q-axis current value Iqt. The current axial force Fer is an estimated value of the axial force acting on the rack shaft 22. The current axial force Fer is a road surface axial force that includes road surface information.

[0067] Specifically, the current axial force calculation unit 112 calculates the current axial force Fer based on the following assumption: the torque applied to the rack shaft 22 by the steering-side motor 32 and the torque corresponding to the force applied to the steering wheel 5 from the road surface are balanced. The current axial force calculation unit 112 calculates the current axial force Fer such that its absolute value increases as the absolute value of the q-axis current value Iqt increases. The calculated current axial force Fer is output to the distribution calculation unit 113.

[0068] The angular axial force Fib and the current axial force Fer are input to the distribution calculation unit 113. In the distribution calculation unit 113, the angular distribution gain Gib and the current distribution gain Ger are preset based on experimental results and the like. The angular distribution gain Gib represents the distribution ratio of the angular axial force Fib in the pre-adjustment axial force Fds. The current distribution gain Ger represents the distribution ratio of the current axial force Fer in the pre-adjustment axial force Fds. The distribution calculation unit 113 calculates the angular axial force distribution value by multiplying the angular axial force Fib by the angular distribution gain Gib, and calculates the current axial force distribution value by multiplying the current axial force Fer by the current distribution gain Ger. The distribution calculation unit 113 calculates the pre-adjustment axial force Fds by summing these distribution values. The calculated pre-adjustment axial force Fds is output to the first axial force calculation unit 102 and the second axial force calculation unit 103.

[0069] The pre-adjustment axial force Fds and the vehicle speed Vb are input to the first axial force calculation unit 102. For the purpose of improving the feeling of steering operation, the first axial force calculation unit 102 calculates the first axial force Fd1 by adjusting the pre-adjustment axial force Fds using the vehicle speed Vb, for example. The first axial force calculation unit 102 according to this embodiment includes a first map that defines the relationship between the absolute value of the pre-adjustment axial force Fds and the vehicle speed Vb and the absolute value of the first axial force Fd1. That is, the first axial force calculation unit 102 adjusts the pre-adjustment axial force Fds based on the absolute value of the pre-adjustment axial force Fds and the vehicle speed Vb.

[0070] In the first map, when the absolute value of the pre-adjustment axial force Fds is zero, the absolute value of the first axial force Fd1 is set to zero. In the first map, the absolute value of the first axial force Fd1 is set to increase linearly as the absolute value of the pre-adjustment axial force Fds increases. In the first map, when the absolute value of the pre-adjustment axial force Fds is equal to or greater than a certain value, although the absolute value of the pre-adjustment axial force Fds increases, the absolute value of the first axial force Fd1 is also set to be fixed at the first upper limit value Fl1. That is, the first map has a protection function for limiting the upper limit value of the first axial force Fd1. The first map is set such that the absolute value of the first axial force Fd1 increases as the vehicle speed Vb increases. That is, the first upper limit value Fl1 changes according to the vehicle speed Vb.

[0071] The first axial force calculation unit 102 calculates the absolute value of the first axial force Fd1 with reference to the first map, based on the axial force Fds before adjustment and the vehicle speed Vb. The first axial force calculation unit 102 calculates a component having the absolute value obtained by map calculation and the same sign as the axial force Fds before adjustment as the first axial force Fd1. The calculated first axial force Fd1 is output to the axial force calculation unit 104 after adjustment.

[0072] The axial force Fds before adjustment is input to the second axial force calculation unit 103. For the purpose of improving the feeling of steering operation, the second axial force calculation unit 103 calculates the second axial force Fd2 by, for example, adjusting the axial force Fds before adjustment without using the vehicle speed Vb. The second axial force calculation unit 103 according to this embodiment includes a second map defining the relationship between the absolute value of the axial force Fds before adjustment and the absolute value of the second axial force Fd2. That is, the second axial force calculation unit 103 adjusts the axial force Fds before adjustment based on the absolute value of the axial force Fds before adjustment.

[0073] In the second map, the relationship between the absolute value of the axial force Fds before adjustment and the absolute value of the second axial force Fd2 is set to be substantially the same as the relationship between the absolute value of the axial force Fds before adjustment and the absolute value of the first axial force Fd1 at a predetermined vehicle speed in the first map. That is, in the second map, when the absolute value of the axial force Fds before adjustment is zero, the absolute value of the second axial force Fd2 is set to zero. In the second map, the absolute value of the second axial force Fd2 is set to increase linearly as the absolute value of the axial force Fds before adjustment increases. In the second map, when the absolute value of the axial force Fds before adjustment is equal to or greater than a certain value, although the absolute value of the axial force Fds before adjustment increases, the absolute value of the second axial force Fd2 is also set to be fixed at the second upper limit value Fl2. That is, the second map has a protection function for limiting the upper limit value of the second axial force Fd2. For example, the predetermined vehicle speed is set to a speed at which the absolute value of the second axial force Fd2 is not too large or too small in a wide vehicle speed range.

[0074] The second axial force calculation unit 103 calculates the absolute value of the second axial force Fd2 with reference to the second map, based on the axial force Fds before adjustment. The second axial force calculation unit 103 calculates a component having the absolute value obtained by map calculation and the same sign as the axial force Fds before adjustment as the second axial force Fd2. The calculated second axial force Fd2 is output to the axial force calculation unit 104 after adjustment.

[0075] In addition to the first axial force Fd1 and the second axial force Fd2, the vehicle speed state signal Sve is also input to the adjusted axial force calculation unit 104. The adjusted axial force calculation unit 104 calculates the adjusted axial force Fir based on these state quantities. The adjusted axial force calculation unit 104 according to this embodiment calculates the value obtained by summing the first axial force Fd1 and the second axial force Fd2 at a separately set predetermined distribution ratio as the adjusted axial force Fir.

[0076] Specifically, in the adjusted axial force calculation unit 104, the first distribution gain G1 and the second distribution gain G2 are preset based on experimental results and the like. The first distribution gain G1 represents the distribution ratio of the first axial force Fd1 in the adjusted axial force Fir. The second distribution gain G2 represents the distribution ratio of the second axial force Fd2 in the adjusted axial force Fir.

[0077] Here, the adjusted axial force calculation unit 104 changes the first distribution gain G1 and the second distribution gain G2 based on the state of the vehicle speed Vb. When the vehicle speed state signal Sve indicates that the state of the vehicle speed Vb is normal, the adjusted axial force calculation unit 104 sets the value of the first distribution gain G1 to the first normal gain G1n, and sets the value of the second distribution gain G2 to the second normal gain G2n. The first normal gain G1n is, for example, "0.5", and the second normal gain G2n is, for example, "0.5".

[0078] When the vehicle speed state signal Sve indicates that the state of the vehicle speed Vb is abnormal, the adjusted axial force calculation unit 104 sets the value of the first distribution gain G1 to the first abnormal gain G1a, and sets the value of the second distribution gain G2 to the second abnormal gain G2a. The first abnormal gain G1a is, for example, "0", and the second abnormal gain G2a is, for example, "1". That is to say, the adjusted axial force calculation unit 104 sets the distribution ratio of the first axial force Fd1 to be smaller when the state of the vehicle speed Vb is abnormal than when the state of the vehicle speed Vb is normal. Therefore, the proportion of the first axial force Fd1 in the adjusted axial force Fir is smaller when the state of the vehicle speed Vb is abnormal than when the state of the vehicle speed Vb is abnormal.

[0079] The adjusted axial force calculation unit 104 calculates a first axial force distribution value by multiplying the first axial force Fd1 by the first distribution gain G1 set based on the state of the vehicle speed Vb as described above. The adjusted axial force calculation unit 104 calculates a second axial force distribution value by multiplying the second axial force Fd2 by the second distribution gain G2 set based on the state of the vehicle speed Vb as described above. Then, the adjusted axial force calculation unit 104 calculates the adjusted axial force Fir by summing these distribution values. As described above, the calculated adjusted axial force Fir is output as an axial component to the subtracter 93.

[0080] The operation and advantages of this embodiment will be described below. The adjusted axial force calculation unit 104 sets the ratio of the first axial force Fd1 in the adjusted axial force Fir to be smaller when the state of the vehicle speed Vb is abnormal than when the state of the vehicle speed Vb is normal. Therefore, when the state of the vehicle speed Vb is abnormal, the proportion of the contribution of the first axial force Fd1, which has been adjusted using the vehicle speed Vb, to the adjusted axial force Fir decreases. The target reaction torque Ts* is calculated based on the adjusted axial force Fir in which the proportion of the contribution of the first axial force Fd1 has decreased. Therefore, it is possible to prevent the target reaction torque Ts* from becoming different from an appropriate value corresponding to the driving state of the vehicle.

[0081] The first axial force calculation unit 102 adjusts the axial force Fds before adjustment so that the first axial force Fd1 is equal to or less than the first upper limit value Fl1 corresponding to the vehicle speed Vb. The second axial force calculation unit 103 adjusts the axial force Fds before adjustment so that the second axial force Fd2 is equal to or less than the second upper limit value Fl2. Therefore, for example, even when the axial force Fds before adjustment becomes too large because the current axial force Fer becomes excessive due to an abnormality of the current sensor 69, it is possible to prevent the adjusted axial force Fir from becoming too large. Therefore, it is possible to prevent the target reaction torque Ts* from becoming an abnormal value.

[0082] Second Embodiment

[0083] The steering control device according to the second embodiment will be described below with reference to the drawings. For ease of description, elements that are the same as those in the first embodiment will be referred to by the same reference numerals as in the first embodiment, and their description will be omitted.

[0084] As Figure 4As shown, the adjusted axial force calculation unit 121 according to this embodiment outputs the first axial force Fd1 or the second axial force Fd2 as the adjusted axial force Fir, that is, the axial component, by switching the effective calculation system to the first calculation system or the second calculation system. The first calculation system is a calculation system for calculating the first axial force Fd1 and includes the pre-adjustment axial force calculation unit 101 and the first axial force calculation unit 102. The second calculation system is a calculation system for calculating the second axial force Fd2 and includes the pre-adjustment axial force calculation unit 101 and the second axial force calculation unit 103.

[0085] Specifically, when the vehicle speed state signal Sve indicates that the state of the vehicle speed Vb is normal, the adjusted axial force calculation unit 121 outputs the first axial force Fd1 as the adjusted axial force Fir by making the first calculation system effective. On the other hand, when the vehicle speed state signal Sve indicates that the state of the vehicle speed Vb is abnormal, the adjusted axial force calculation unit 121 outputs the second axial force Fd2 as the adjusted axial force Fir by making the second calculation system effective. That is to say, when the state of the vehicle speed Vb is abnormal, the adjusted axial force calculation unit 121 switches the value of the adjusted axial force Fir from the value of the first axial force Fd1 to the value of the second axial force Fd2. Therefore, when the state of the vehicle speed Vb is abnormal, the first axial force Fd1 does not affect the adjusted axial force Fir. That is to say, when the state of the vehicle speed Vb is abnormal, the proportion of the first axial force Fd1 in the adjusted axial force Fir decreases.

[0086] When the effective calculation system is switched from the first calculation system to the second calculation system due to the state of the vehicle speed Vb changing from normal to abnormal, the adjusted axial force calculation unit 121 according to this embodiment slowly changes the value of the adjusted axial force Fir from the value of the first axial force Fd1 to the value of the second axial force Fd2.

[0087] For example, the adjusted axial force calculation unit 121 calculates the difference by subtracting the second axial force Fd2 from the first axial force Fd1, and the difference is obtained in the calculation cycle of switching the effective calculation system from the first calculation to the second calculation system. The adjusted axial force calculation unit 121 calculates a compensation value based on the difference and the steering operation speed such that the absolute value slowly decreases. The adjusted axial force calculation unit 121 outputs the value obtained by adding the compensation value to the second axial force Fd2 as the adjusted axial force Fir. That is to say, when the compensation value is zero, the value of the adjusted axial force Fir is the same as the value of the second axial force Fd2.

[0088] According to this embodiment, in addition to the operations and advantages that are the same as those of the first embodiment, the following operations and advantages are also achieved. When switching the effective computing system from the first computing system to the second computing system, the adjusted axial force calculation unit 121 slowly changes the value of the adjusted axial force Fir as the axial component from the value of the first axial force Fd1 to the value of the second axial force Fd2. Therefore, compared with the case where the value of the adjusted axial force Fir changes immediately from the value of the first axial force Fd1 to the value of the second axial force Fd2 when the vehicle speed Vb state is abnormal, a sharp change in the adjusted axial force Fir can be suppressed. Therefore, a sharp change in the target reaction torque Ts* can be suppressed and a deterioration in the feeling of steering operation can be prevented.

[0089] The above embodiment can be modified as follows. Unless there is a technical conflict, the above embodiment and the following modification examples can be combined. In the above embodiment, the average value of the wheel speeds Vfl, Vfr, Vrl, and Vrr is used as the vehicle speed Vb, but the present invention is not limited thereto, and for example, the average value of the second highest wheel speed and the third highest wheel speed among the wheel speeds Vfl, Vfr, Vrl, and Vrr can be used, and the method of calculating the vehicle speed Vb can be appropriately modified. Instead of using the wheel speeds, for example, a value obtained by integrating the longitudinal acceleration of the vehicle can be used as the vehicle speed Vb. For example, a positioning signal from a Global Positioning System (GPS) satellite can be received, and an estimated vehicle speed estimated based on the change per unit time of the position of the vehicle according to the received positioning signal can be used as the vehicle speed Vb.

[0090] In the above embodiment, the steering control device 1 can calculate the vehicle speed Vb based on the wheel speeds Vfl, Vfr, Vrl, and Vrr. In the above embodiment, the input torque base component calculation unit 91 can calculate the input torque base component Tb based on, for example, the steering torque Th and the vehicle speed Vb. In this case, for example, the input torque base component calculation unit 91 calculates the input torque base component Tb such that its absolute value increases as the vehicle speed Vb decreases. When a vehicle speed state signal Sve indicating that the vehicle speed Vb is abnormal is input, preferably, the input torque base component calculation unit 91 determines that the vehicle speed Vb is a preset predetermined vehicle speed and calculates the input torque base component Tb based on the steering torque Th. The predetermined vehicle speed is set to a speed at which the input torque base component Tb does not have an excessive value or an excessively small value as the steering torque Th changes.

[0091] In the above-described embodiment, the first mapping of the first axial force calculation unit 102 is set such that the absolute value of the first axial force Fd1 is equal to or less than the first upper limit value Fl1. However, the present invention is not limited thereto. For example, instead of setting the first upper limit value Fl1 in the first mapping, the absolute value of the first axial force Fd1 may be set to be greater than the first upper limit value Fl1 in proportion to the absolute value of the axial force Fds before adjustment. Similarly, instead of setting the second upper limit value Fl2 in the second mapping of the second axial force calculation unit 103, the absolute value of the second axial force Fd2 may be set to be greater than the second upper limit value Fl2 in proportion to the absolute value of the axial force Fds before adjustment.

[0092] In the above-described embodiment, the first axial force calculation unit 102 calculates the first axial force Fd1 by adjusting the axial force Fds before adjustment via mapping calculation. However, the present invention is not limited thereto. The first axial force calculation unit 102 may calculate the first axial force Fd1 by adjusting the axial force Fds before adjustment, for example, by calculation using a predetermined function expression. Similarly, the second axial force calculation unit 103 may calculate the second axial force Fd2 by adjusting the axial force Fds before adjustment, for example, by calculation using a predetermined function expression.

[0093] In the above-described embodiment, the first axial force calculation unit 102 adjusts the axial force Fds before adjustment based on the absolute value of the axial force Fds before adjustment and the vehicle speed Vb. However, the present invention is not limited thereto. The first axial force calculation unit 102 may adjust the axial force Fds before adjustment considering other state quantities as long as the other state quantities include the vehicle speed Vb. The second axial force calculation unit 103 may adjust the axial force Fds before adjustment without using the vehicle speed Vb and may adjust the axial force Fds before adjustment considering state quantities other than the absolute value of the axial force Fds before adjustment.

[0094] In the above-described embodiment, the distributed axial force obtained by summing the angular axial force Fib and the current axial force Fer at a predetermined distribution ratio is used as the axial force Fds before adjustment. However, the present invention is not limited thereto. For example, the distributed axial force obtained by distributing the calculated axial force other than the angular axial force Fib and the current axial force Fer may be used as the axial force Fds before adjustment. Other calculated axial forces include, for example, the vehicle state quantity axial force based on the vehicle speed Vb, the lateral acceleration, and the yaw rate of the vehicle; the sensor axial force based on the detection value of the axial force sensor that detects the axial force acting on the rack shaft 22; and the tire axial force based on the tire force detected by the tire force sensor. The vehicle state quantity axial force does not include the road surface information that does not cause a change in the vehicle's behavior in the lateral direction, but includes the road surface information that can be transmitted through the change in the vehicle's behavior in the lateral direction. The sensor axial force and the tire axial force are the road surface axial forces that include the road surface information. Instead of using the distributed axial force as the axial force Fds before adjustment, for example, a single calculated axial force such as the current axial force Fer may be used as the axial force Fds before adjustment.

[0095] In the first embodiment, the first abnormal gain G1a is set to "0". However, the present invention is not limited thereto. The value of the first abnormal gain G1a may be appropriately changed as long as the value of the first abnormal gain G1a is less than the value of the first normal gain G1n.

[0096] In the first embodiment, when the state of the vehicle speed Vb becomes abnormal, the value of the first distribution gain G1 may be slowly changed from the first normal gain G1n to the first abnormal gain G1a. Similarly, the value of the second distribution gain G2 may be slowly changed from the second normal gain G2n to the second abnormal gain G2a.

[0097] In the second embodiment, the calculation mode in which the value of the adjusted axial force Fir is slowly changed from the value of the first axial force Fds1 to the value of the second axial force Fds2 may be appropriately modified. For example, after the state of the vehicle speed Vb changes from the normal state to the abnormal state, the compensation value added to the second axial force Fds2 may be slowly decreased over time.

[0098] In the second embodiment, when switching the effective calculation system from the first calculation system to the second calculation system, the adjusted axial force calculation unit 121 may immediately change the value of the adjusted axial force Fir from the value of the first axial force Fds1 to the value of the second axial force Fds2.

[0099] In the above-described embodiment, the axial component calculation unit 92 may calculate, as the axial component, a value obtained by adding another axial force to the adjusted axial force Fir. For example, as such another axial force, an end axial force for restricting further steering operation of the steering when the absolute value of the steering operation angle of the steering wheel 3 approaches the steering operation angle threshold may be employed.

[0100] In the above-described embodiment, the current axial force Fer is calculated based on the q-axis current value Iqt, but the present invention is not limited thereto, and for example, the current axial force Fer may be calculated based on the q-axis target current value Iqt*. In the above-described embodiment, the angular axial force Fib is calculated based on the steering-corresponding angle θp, but the present invention is not limited thereto, and for example, the angular axial force Fib may be calculated based on the target steering-corresponding angle θp* or the steering operation angle θh, or another method such as considering another parameter such as the steering operation torque Th may be used to calculate the angular axial force Fib.

[0101] In the above-described embodiment, the steer-by-wire steering system 2 to be controlled employs a linkless structure in which the power transmission between the steering operation unit 4 and the steering unit 6 is cut off, but the present invention is not limited thereto, and a steering system having a structure in which the power transmission between the steering operation unit 4 and the steering unit 6 is cut off by a clutch may be controlled.

[0102] In the above-described embodiment, the steer-by-wire steering system 2 is controlled, but the present invention is not limited thereto. For example, an electric power steering system including a steering operation mechanism for steering the steering wheel 5 based on an operation of the steering wheel 3 and applying a motor torque for assisting the operation of the steering wheel 3 as an assisting force may be controlled. In such a steering system, the steering operation torque Th required for steering the steering wheel 3 is changed by the motor torque applied as the assisting force. In this case, the steering control device calculates a target assisting torque as a target value of the assisting force based on the axial component.

Claims

1. A steering control device (1), which is configured to control a steering system that changes the steering torque required for steering the steering wheel using the motor torque applied from a motor, wherein the steering control device is characterized by comprising: A target torque generator (72) configured to generate a target torque as a target value of the motor torque; and A control signal generator configured to generate a control signal for controlling the motor to generate a motor torque corresponding to the target torque, wherein the target torque generator (72) includes: a pre-adjustment axial force calculator (101) configured to calculate a pre-adjustment axial force corresponding to an axial force acting on a steering shaft connected to a steering wheel; a first axial force calculator (102) configured to calculate a first axial force by adjusting the pre-adjustment axial force using a vehicle speed; a second axial force calculator (103) configured to calculate a second axial force by adjusting the pre-adjustment axial force without using the vehicle speed; a post-adjustment axial force calculator (104) configured to calculate a post-adjustment axial force based on the first axial force and the second axial force; and a target torque calculator (93) configured to calculate the target torque based on the post-adjustment axial force, and wherein the post-adjustment axial force calculator (104) is configured to set a ratio of a contribution of the first axial force to the post-adjustment axial force to be smaller when the vehicle speed is in an abnormal state than when the vehicle speed is in a normal state, The pre-adjustment axial force calculator (101) includes: an angular axial force calculation unit (111) that calculates an angular axial force (Fib); a current axial force calculation unit (112) that calculates a current axial force (Fer); and a distribution calculation unit (113) that sums the angular axial force (Fib) and the current axial force (Fer) at a separately set predetermined distribution ratio. The pre-adjustment axial force calculator (101) uses the distribution axial force obtained by summing by the distribution calculation unit (113) as the pre-adjustment axial force.

2. The steering control device (1) according to claim 1, wherein The post-adjustment axial force calculator (104) is configured to calculate the post-adjustment axial force by summing the first axial force and the second axial force at a separately set predetermined distribution ratio, and characterized in that the post-adjustment axial force calculator (104) is configured to set a distribution ratio of the first axial force to be smaller when the vehicle speed is in an abnormal state than when the vehicle speed is in a normal state.

3. The steering control device (1) according to claim 1, wherein The post-adjustment axial force calculator (104) is configured to switch an effective calculation system to a first calculation system or a second calculation system. The first calculation system is a calculation system including the first axial force calculator (102), and the second calculation system is a calculation system including the second axial force calculator (103), characterized in that the post-adjustment axial force calculator (104) is configured to: when the vehicle speed is in a normal state, output the first axial force as the post-adjustment axial force by making the first calculation system effective; and The adjusted axial force calculator (104) is configured to: when the vehicle speed is abnormal, output the second axial force as the adjusted axial force by enabling the second calculation system.

4. The steering control device (1) according to claim 3, wherein The adjusted axial force calculator (104) is configured to: when switching the effective calculation system from the first calculation system to the second calculation system, slowly change the value of the adjusted axial force from the value of the first axial force to the value of the second axial force.

5. The steering control device (1) according to any one of claims 1 to 4, wherein The first axial force calculator (102) is configured to adjust the axial force before adjustment such that the first axial force is equal to or less than a first upper limit value based on the vehicle speed, and It is characterized in that the second axial force calculator (103) is configured to adjust the axial force before adjustment such that the second axial force is equal to or less than a second upper limit value.

6. A steering system (2), wherein Comprising: A motor; A steering control unit (4) connected to the steering wheel; A steering unit (6) configured to steer the steering wheel, and the power transmission path between the steering control unit (4) and the steering unit (6) is cut off; And A steering control device (1), wherein the motor is a steering control side motor (13), and the steering control side motor applies a motor torque as a steering reaction force against the steering input to the steering control unit. wherein the steering control device (1) includes: a target torque generator (72) configured to generate a target torque as a target value of the motor torque; and a control signal generator configured to generate a control signal for controlling the motor to generate a motor torque corresponding to the target torque. wherein the target torque generator (72) includes: an axial force calculator before adjustment (101) configured to calculate an axial force before adjustment corresponding to the axial force acting on the steering shaft connected to the steering wheel; a first axial force calculator (102) configured to calculate a first axial force by adjusting the axial force before adjustment using the vehicle speed; a second axial force calculator (103) configured to calculate a second axial force by adjusting the axial force before adjustment without using the vehicle speed; an adjusted axial force calculator (104) configured to calculate an adjusted axial force based on the first axial force and the second axial force; and a target torque calculator (93) configured to calculate the target torque based on the adjusted axial force. wherein the target torque generator (72) is configured to generate a target reaction torque as a target value of the steering reaction force as the target torque, and wherein the adjusted axial force calculator (104) is configured to set the ratio of the contribution of the first axial force to the adjusted axial force to be smaller when the vehicle speed is abnormal than when the vehicle speed is normal. The axial force calculator (101) before the above adjustment includes: an angular axial force calculation unit (111) that calculates an angular axial force (Fib); a current axial force calculation unit (112) that calculates a current axial force (Fer); and a distribution calculation unit (113) that sums the angular axial force (Fib) and the current axial force (Fer) at a separately set predetermined distribution ratio. The axial force calculator (101) before the above adjustment uses the distributed axial force obtained by summing by the above distribution calculation unit (113) as the axial force before the above adjustment.

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