Steering control device

Abstract

To provide a steering control device that is able to propose a more useful method as a method for varying a relation between a steering angle and a turning angle.SOLUTION: A steering control device has a turning-side control unit that controls a turning unit. The turning-side control unit controls an operation of the turning unit, based on a target pinion angle θp*. The turning-side control unit has a steering-angle-ratio variable control unit 62 that calculates the target pinion angle θp* for operating the turning unit, based on a steering conversion angle θs _ p obtained by affecting a steering angle θs. The steering-angle-ratio variable control unit 62 includes: a speed-increase-ratio calculation unit 70 that calculates a speed increase ratio, i. e., an acceleration increment value ΔGsir, based on a vehicle speed V and the steering angle θs; and an angle information calculation unit 71 that calculates the steering conversion angle θs_p by using the acceleration increment value ΔGsir to convert the steering angle θs.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a steering control device. [Background technology]

[0002] A vehicle is equipped with a steering device having, for example, a steering section that enables steering of the steering wheel of the vehicle and a steering section that enables steering of the steered wheels of the vehicle. Patent Document 1 discloses, as an example, a steer-by-wire type steering device having a structure in which the power transmission paths between the steering section and the steering section are separated.

[0003] The above-mentioned Patent Document 1 discloses that the operation of the steering unit is controlled using a target steering angle obtained by correcting the steering angle, which is the angle at which the steering wheel is steered and is detected as the state of the steering unit. Here, the steering angle is corrected by varying the ratio of the steering angle, which is the angle of the steered wheels, to the steering angle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-192908 Summary of the Invention [Problem to be solved by the invention]

[0005] In the correction of the steering angle described above, a steering rate gain obtained by map calculation according to vehicle speed is used to vary the ratio of the steering angle, which is the angle of the steered wheels, to the steering angle, thereby varying the relationship between the steering angle and the steering angle. The method of varying the relationship between the steering angle and the steering angle is not limited to using the steering rate gain, and there is room for proposing other more useful methods. [Means for solving the problem]

[0006] A steering control device that solves the above problem is a steering control device that controls at least the steering unit of a steering device that includes a steering unit that enables steering of the steering wheel of a vehicle and a steering unit that operates to steer the steered wheels of the vehicle, and has a structure in which the power transmission path between the steering unit and the steering unit is separated, and includes a control unit that calculates a steering control amount for operating the steering unit based on angle information obtained in relation to the steering angle, which is the angle at which the steering wheel is steered, and controls the operation of the steering unit based on the steering control amount, and the control unit is configured to include a speed increase ratio calculation unit that calculates a speed increase ratio that indicates the ratio of a change in the steering angle, which is the angle of the steered wheels, to a change in the steering angle, based on state variables that change depending on at least one operating state of the steering device and the vehicle in which the steering device is installed, and an angle information calculation unit that converts the steering angle using the speed increase ratio obtained by the speed increase ratio calculation unit to calculate the angle information.

[0007] According to the above configuration, the speed increase ratio is calculated based on a state variable that changes depending on the operating state of at least one of the steering device and the vehicle equipped with the steering device. Therefore, changes in the operating state are reflected as changes in the speed increase ratio. In other words, when calculating the steering control amount, the speed increase ratio can be used as an index for obtaining an appropriate steering control amount depending on the operating state. Furthermore, for example, when information related to the steering angle is reflected in the control of the steering unit as the state of the steering unit, the speed increase ratio obtained by the speed increase ratio calculation unit can be reused by, for example, reciprocalizing it. In this case, even when the state of the steering unit is reflected in the control of the steering unit, there is no need to provide a separate calculation unit such as a speed increase ratio calculation unit for converting information related to the steering angle. In other words, an increase in memory capacity set up in the control unit can be suppressed. Therefore, a useful method can be proposed for varying the relationship between the steering angle and the steering angle, using the speed increase ratio, which is the ratio of the amount of change in the steering angle to the amount of change in the steering angle.

[0008] For example, when the steering angle is changed so that the speed increase ratio results in an increase in speed, the yaw rate response characteristic, which is the behavior of the vehicle, increases in response in accordance with the increase in speed, and a transient peak also increases accordingly. If an attempt is made to suppress the increase in this transient peak, the range in which the speed increase ratio can be used will be narrowed.

[0009] Therefore, in the above steering control device, it is preferable that the angle information calculation unit includes: a static component calculation unit that calculates a static component, which is a component that reflects steady-state characteristics of the yaw rate response characteristics, which is the behavior of the vehicle with respect to the angle information, as a result of converting the steering angle using the speed increase ratio; and a compensation calculation unit that calculates the angle information by phase-compensating the static component based on the state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit, in order to adjust transient characteristics of the yaw rate response characteristics that appear in relation to the calculation of the static component.

[0010] According to the above configuration, the response characteristics of the yaw rate can be adjusted so as to suppress an increase in a transient peak without narrowing the range that can be used as the speed-up ratio.

[0011] Furthermore, in the above steering control device, it is preferable that the static component calculation unit calculates the static component using an increase in the speed increase ratio, which is the difference between a reference value where the ratio of a change in the steering angle, which is the angle of the steered wheels, to a change in the steering angle is 1, the compensation calculation unit is configured as a phase lag filter whose transfer function changes based on the state variables including at least the state variables used for calculation by the speed increase ratio calculation unit so as to perform phase lag compensation, and the control unit is configured to calculate the steering control amount based on a result obtained by adding the steering angle and the angle information obtained by the phase lag filter.

[0012] According to the above configuration, even if the steering angle is changed so as to increase the speed as a result of using the speed-up ratio, the effect of the change is limited to the increase in the speed due to the speed-up ratio. In this case, even if phase compensation is performed while leaving the transient characteristics of the yaw rate response characteristics that the vehicle originally has, it is possible to effectively suppress an increase in the transient peak that appears in the yaw rate response characteristics.

[0013] Furthermore, in the above steering control device, it is preferable that the static component calculation unit calculates the static component using the speed increase ratio, the compensation calculation unit is configured as a phase compensation filter whose transfer function changes based on state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit so as to perform phase compensation, the phase compensation filter is configured to include an inverse function obtained by interchanging the numerator and denominator of a transfer function that indicates a transient characteristic of the response characteristic of the yaw rate, and the control unit is configured to calculate the steering control amount based on the angle information obtained by the phase compensation filter.

[0014] According to the above configuration, if the steering angle is changed to increase the speed as a result of using the speed-increase ratio, the effect of this will be felt by the value of the speed-increase ratio. In this case, phase compensation can be performed while canceling out the transient characteristics of the yaw rate response characteristics inherent to the vehicle. Therefore, even if the steering angle is changed using the speed-increase ratio, it is possible to effectively suppress an increase in the transient peak that appears in the yaw rate response characteristics.

[0015] Furthermore, in the above steering control device, it is preferable that the compensation calculation unit further includes a phase lag filter whose transfer function changes based on the state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit so as to perform phase lag compensation for reducing noise that appears from a perspective different from the transient characteristics of the response characteristics of the yaw rate that appears in relation to the calculation of the static component.

[0016] According to the above configuration, it is possible to reduce noise that appears from a perspective different from the transient increase in the peak in the yaw rate response characteristics, which is effective in ensuring stability in the control of the operation of the steering unit. [Effects of the Invention]

[0017] According to the steering control device of the present invention, it is possible to propose a more useful method for varying the relationship between the steering angle and the turning angle. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. [Figure 2] FIG. 2 is a block diagram showing the functions of a steering control device. [Figure 3] FIG. 3 is a block diagram showing the function of a steering angle ratio variable control unit according to the first embodiment. [Figure 4] 5(a) to 5(c) are diagrams illustrating the characteristics of the yaw rate response in the first embodiment. [Figure 5] FIG. 3 is a block diagram showing the function of a steering angle ratio inverse variable control unit according to the first embodiment. [Figure 6] FIG. 10 is a block diagram showing the function of a steering angle ratio variable control unit according to a second embodiment. [Figure 7] FIG. 10 is a block diagram showing the function of a steering angle ratio inverse variable control unit according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] First Embodiment A first embodiment of the steering control device will be described below with reference to the drawings. As shown in FIG. 1, the steering device 2 of this embodiment is a steer-by-wire type steering device for a vehicle. The steering device 2 is equipped with a steering control device 1 that controls the operation of the steering device 2. The steering device 2 is equipped with a steering unit 4 and a turning unit 6. The steering unit 4 is steered by a driver via a steering wheel 3 of the vehicle. The turning unit 6 steers left and right steerable wheels 5 of the vehicle in accordance with the steering input to the steering unit 4 by the driver. Note that the steering device 2 of this embodiment has a structure in which the power transmission paths between the steering unit 4 and the turning unit 6 are mechanically separated at all times. In other words, the power transmission paths between a steering actuator 12 (described later) and a turning actuator 31 (described later) are mechanically separated at all times.

[0020] The steering unit 4 includes a steering shaft 11 and a steering actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering actuator 12 includes a steering-side motor 13, which is a drive source, and a steering-side reduction mechanism 14. The steering-side motor 13 is a reaction motor that applies a steering reaction force, which is a force that resists steering, to the steering wheel 3 via the steering shaft 11. The steering-side motor 13 is connected to the steering shaft 11 via the steering-side reduction mechanism 14, which is made up of, for example, a worm and wheel. For example, a three-phase brushless motor is used as the steering-side motor 13 in this embodiment.

[0021] The steered unit 6 includes a pinion shaft 21, a rack shaft 22 serving as a steered shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected at a predetermined cross angle. A rack-and-pinion mechanism 24 is formed by meshing pinion teeth 21a formed on the pinion shaft 21 with rack teeth 22a formed on the rack shaft 22. In other words, the pinion shaft 21 corresponds to a rotation axis that can be converted into a steering angle of the steered wheels 5. The rack housing 23 accommodates the rack-and-pinion mechanism 24. An end of the pinion shaft 21 opposite the end connected to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the rack shaft 22 via rack ends 25 formed as ball joints. The ends of the tie rods 26 are connected to knuckles (not shown) to which the left and right steered wheels 5 are attached.

[0022] The steering unit 6 includes a steering actuator 31. The steering actuator 31 includes a steering-side motor 32, which is a drive source, a transmission mechanism 33, and a conversion mechanism 34. The steering-side motor 32 applies a steering force to the rack shaft 22 to turn the steered wheels 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering-side motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering-side motor 32 into reciprocating motion of the rack shaft 22 via the conversion mechanism 34, which is, for example, a ball screw mechanism. A three-phase brushless motor, for example, is used as the steering-side motor 32 in this embodiment.

[0023] In the steering device 2 configured as described above, the steering actuator 31 applies motor torque as a steering force to the rack shaft 22 in response to the steering operation by the driver, thereby changing the steering angle of the steered wheels 5. At this time, the steering actuator 12 applies a steering reaction force that resists the steering by the driver to the steering wheel 3. In other words, in the steering device 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is the motor torque applied from the steering actuator 12.

[0024] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 inside the rack housing 23. In other words, the rack shaft 22 is supported movably along its axial direction and is pressed toward the pinion shaft 21 by a support mechanism (not shown) provided in the steering device 2. In this way, the rack shaft 22 is supported inside the rack housing 23. However, another support mechanism may be provided to support the rack shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0025] <Electrical configuration of steering device 2> 1, the steering-side motor 13 and the turning-side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of the steering-side motor 13 and the turning-side motor 32.

[0026] The steering control device 1 is connected to a torque sensor 41, a steering side rotation angle sensor 42, a turning side rotation angle sensor 43, and a vehicle speed sensor 44. The torque sensor 41 detects the steering torque Th, which is a value indicating the torque applied to the steering shaft 11 by the driver's steering. The torque sensor 41 is provided on a portion of the steering shaft 11 closer to the steering wheel 3 than the steering-side reduction gear mechanism 14. The torque sensor 41 detects the steering torque Th based on the twist of a torsion bar 41a provided midway along the steering shaft 11. Note that the steering torque Th is detected as a positive value when the vehicle is steered to the right, for example, and as a negative value when the vehicle is steered to the left.

[0027] The steering-side rotation angle sensor 42 detects the rotation angle θa, which is the angle of the rotation shaft of the steering-side motor 13, within a range of 360 degrees. The steering-side rotation angle sensor 42 is provided in the steering-side motor 13. The rotation angle θa of the steering-side motor 13 is used to calculate the steering angle θs. The steering-side motor 13 and the steering shaft 11 are linked via the steering-side reduction mechanism 14. Therefore, there is a correlation between the rotation angle θa of the steering-side motor 13 and the rotation angle of the steering shaft 11, and ultimately the steering angle θs, which is the rotation angle of the steering wheel 3. Therefore, the steering angle θs can be calculated based on the rotation angle θa of the steering-side motor 13. Note that the rotation angle θa is detected as a positive value when steering to the right, for example, and as a negative value when steering to the left. In this embodiment, the steering angle θs is an example of a state variable that changes depending on the operating state of the steering device 2.

[0028] The turning-side rotation angle sensor 43 detects the rotation angle θb, which is the angle of the rotation shaft of the turning-side motor 32, within a range of 360 degrees. The turning-side rotation angle sensor 43 is provided in the turning-side motor 32. The rotation angle θb of the turning-side motor 32 is used to calculate the pinion angle θp. The turning-side motor 32 and the pinion shaft 21 are linked via the transmission mechanism 33, the conversion mechanism 34, and the rack-and-pinion mechanism 24. Therefore, there is a correlation between the rotation angle θb of the turning-side motor 32 and the pinion angle θp, which is the rotation angle of the pinion shaft 21. Therefore, the pinion angle θp can be determined based on the rotation angle θb of the turning-side motor 32. In addition, the pinion shaft 21 is meshed with the rack shaft 22. Therefore, there is also a correlation between the pinion angle θp and the amount of movement of the rack shaft 22. In other words, the pinion angle θp is a value that reflects the turning angle of the steered wheels 5. The rotation angle θb is detected as a positive value when the vehicle is steered to the right, and as a negative value when the vehicle is steered to the left.

[0029] The vehicle speed sensor 44 detects the vehicle speed V, which is set as information indicating the traveling speed of the vehicle. The vehicle speed sensor 44 may be connected to a vehicle-side control device that is mounted on the vehicle as a control device separate from the steering control device 1. In this case, the vehicle speed V is input from the vehicle-side control device to the steering control device 1 via an in-vehicle network such as a CAN (not shown). In this embodiment, the vehicle speed V is an example of a state variable that changes depending on the operating state of the vehicle.

[0030] <Functions of the steering control device 1> The steering control device 1 includes a central processing unit (CPU) and memory (not shown), and the CPU executes a program stored in the memory at each predetermined calculation cycle, thereby executing various processes.

[0031] Fig. 2 shows part of the processing executed by the steering control device 1. The processing shown in Fig. 2 is part of the processing realized by the CPU executing a program stored in memory, and is described for each type of processing realized.

[0032] The steering control device 1 includes a steering side control unit 50 that controls the power supply to the steering side motor 13. The steering side control unit 50 has a steering side current sensor 54. The steering side current sensor 54 detects an actual steering side current value Ia obtained from the current value of each phase of the steering side motor 13 that flows through a connecting wire between the steering side control unit 50 and the motor coil of each phase of the steering side motor 13. The steering side current sensor 54 acquires, as a current, a voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering side motor 13. Note that, for ease of explanation, in FIG. 2, the connecting wires of each phase and the current sensors of each phase are shown collectively.

[0033] The steering control device 1 also includes a turning side control unit 60 that controls the power supply to the turning side motor 32. The turning side control unit 60 has a turning side current sensor 65. The turning side current sensor 65 detects a turning side actual current value Ib obtained from the current value of each phase of the turning side motor 32 flowing through a connecting wire between the turning side control unit 60 and the motor coil of each phase of the turning side motor 32. The turning side current sensor 65 obtains, as a current, a voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the turning side motor 32. For ease of explanation, FIG. 2 illustrates the connecting wires and current sensors of each phase collectively. In this embodiment, the turning side control unit 60 is an example of a control unit that controls the turning unit 6 of the steering device 2.

[0034] <Steering-side control unit 50> As shown in Fig. 2, steering torque Th, vehicle speed V, rotation angle θa, turning side actual current value Ib, and turning conversion angle θp_s, which will be described later, are input to the steering side control unit 50. The steering side control unit 50 controls the power supply to the steering side motor 13 based on the steering torque Th, vehicle speed V, rotation angle θa, turning side actual current value Ib, and turning conversion angle θp_s. Note that the pinion angle θp is calculated based on the rotation angle θb of the turning side motor 32. Also, the turning conversion angle θp_s is calculated based on the pinion angle θp, i.e., the rotation angle θb, or a target pinion angle θp*, which will be described later.

[0035] The steering-side control unit 50 includes a steering angle calculation unit 51 , a target reaction torque calculation unit 52 , and an energization control unit 53 . The rotation angle θa is input to the steering angle calculation unit 51. The steering angle calculation unit 51 converts the rotation angle θa into an integrated angle including a range exceeding 360°, for example, by counting the number of rotations of the steering-side motor 13 from a steering neutral position, which is the position of the steering wheel 3 when the vehicle is traveling straight. The steering angle calculation unit 51 calculates the steering angle θs by multiplying the integrated angle obtained by conversion by a conversion coefficient based on the rotational speed ratio of the steering-side reduction gear mechanism 14. The steering angle θs obtained in this way is output to the target reaction force torque calculation unit 52 and the turning-side control unit 60.

[0036] Steering torque Th, vehicle speed V, steering side actual current value Ib, steering conversion angle θp_s (described later), and steering angle θs are input to target reaction torque calculation unit 52. Target reaction torque calculation unit 52 calculates target reaction torque command value Ts* based on steering torque Th, vehicle speed V, steering side actual current value Ib, steering conversion angle θp_s, and steering angle θs. Target reaction torque command value Ts* is a reaction force control amount that serves as a target for the steering reaction force of steering wheel 3 to be generated by steering side motor 13. Target reaction torque command value Ts* obtained in this manner is output to current supply control unit 53.

[0037] The current supply control unit 53 receives inputs of the target reaction torque command value Ts*, the rotational angle θa, and the steering side actual current value Ia. The current supply control unit 53 calculates a current command value Ia* for the steering side motor 13 based on the target reaction torque command value Ts*. The current supply control unit 53 then calculates the deviation between the current command value Ia* and a current value on the dq coordinates obtained by converting the steering side actual current value Ia detected by the steering side current sensor 54 based on the rotational angle θa, and controls the power supply to the steering side motor 13 to eliminate the deviation. This causes the steering side motor 13 to generate torque corresponding to the target reaction torque command value Ts*. In other words, it is possible to provide the driver with an appropriate sense of response corresponding to the road reaction force.

[0038] <Steering-side control unit 60> 2, the vehicle speed V, the rotation angle θb, and the steering angle θs are input to the turning-side control unit 60. The turning-side control unit 60 controls the power supply to the turning-side motor 32 based on the vehicle speed V, the rotation angle θb, and the steering angle θs.

[0039] The steering side control unit 60 has a pinion angle calculation unit 61, a steering angle ratio variable control unit 62, a pinion angle feedback control unit ("pinion angle F / B control unit" in the figure) 63, an energization control unit 64, and a steering angle ratio inverse variable control unit 66.

[0040] The rotation angle θb is input to the pinion angle calculation unit 61. The pinion angle calculation unit 61 converts the rotation angle θb into an integrated angle that includes a range exceeding 360°, for example, by counting the number of rotations of the steered-side motor 32 from a rack neutral position, which is the position of the rack shaft 22 when the vehicle is traveling straight. The pinion angle calculation unit 61 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, by multiplying the integrated angle obtained by the conversion by a conversion coefficient that is based on the rotation speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack-and-pinion mechanism 24. The pinion angle θp obtained in this manner is output to the pinion angle feedback control unit 63 and the steering angle ratio inverse variable control unit 66.

[0041] The vehicle speed V and the steering angle θs are input to the steering angle ratio variable control unit 62. Based on the vehicle speed V and the steering angle θs, the steering angle ratio variable control unit 62 calculates a target pinion angle θp* as a steering control amount that is a target for the pinion angle θp obtained as a result of steering the steered wheels 5. The target pinion angle θp* obtained in this manner is output to the pinion angle feedback control unit 63 and the steering angle ratio inverse variable control unit 66.

[0042] The steering angle ratio variable control unit 62 also has a function of calculating a speed increase ratio Gsir, which will be described later, as a variable to be used in a predetermined calculation to be performed in the process of obtaining the target pinion angle θp*. The target pinion angle θp* is subjected to a calculation to scale it so that it becomes a state variable based on the pinion angle θp as a predetermined calculation. The speed increase ratio Gsir will be described in detail later. The speed increase ratio Gsir obtained in the process of obtaining the target pinion angle θp* is used in the calculation as a speed increase value ΔGsir that corresponds to the difference obtained by subtracting the reference value "1" from the speed increase ratio Gsir. The speed increase value ΔGsir obtained in this way is output to the steering angle ratio inverse variable control unit 66.

[0043] Target pinion angle θp* and pinion angle θp are input to pinion angle feedback control unit 63. Pinion angle feedback control unit 63 calculates a steering force command value Tp* as a control amount that becomes a target for the steering force through feedback control of pinion angle θp so that pinion angle θp follows target pinion angle θp*. The steering force command value Tp* obtained in this manner is output to energization control unit 64.

[0044] The turning force command value Tp*, rotation angle θb, and turning side actual current value Ib are input to the energization control unit 64. The energization control unit 64 calculates a current command value Ib* for the turning side motor 32 based on the turning force command value Tp*. The energization control unit 64 then determines the deviation between the current command value Ib* and a current value on the dq coordinates obtained by converting the turning side actual current value Ib detected via the turning side current sensor 65 based on the rotation angle θb, and controls the power supply to the turning side motor 32 so as to eliminate this deviation. As a result, the turning side motor 32 rotates by an angle corresponding to the turning force command value Tp*.

[0045] Pinion angle θp, target pinion angle θp*, and speed increase value ΔGsir are input to steering angle ratio inverse variable control section 66. Steering angle ratio inverse variable control section 66 calculates steering conversion angle θp_s based on pinion angle θp, target pinion angle θp*, and speed increase value ΔGsir. A predetermined calculation is performed on steering conversion angle θp_s to scale it so that it becomes a state variable based on steering angle θs. The steering conversion angle θp_s obtained in this way is output to steering-side control section 50, i.e., target reaction force torque calculation section 52.

[0046] <Steering angle ratio variable control unit 62> As shown in FIG. 3, the steering angle ratio variable control unit 62 has a speed increase ratio calculation unit 70 and an angle information calculation unit 71.

[0047] The speed increase ratio calculation unit 70 receives inputs of the vehicle speed V and the steering angle θs. The speed increase ratio calculation unit 70 includes a speed increase ratio map that defines the relationship between the vehicle speed V, the steering angle θs, and the speed increase value ΔGsir. The speed increase ratio calculation unit 70 receives inputs of the vehicle speed V and the steering angle θs and calculates the speed increase value ΔGsir using the map. The speed increase ratio map is set, for example, so that the value decreases as the steering angle θs increases and as the vehicle speed V increases. In this embodiment, the speed increase ratio Gsir, which may be expressed as a transmission ratio, steering angle ratio, gear ratio, etc., is defined between the steering angle θs and the pinion angle θp as an index indicating the ratio of the amount of change in the pinion angle θp to the amount of change in the steering angle θs. In other words, the speed increase ratio Gsir corresponds to a value obtained by using the steering angle θs as the denominator and the pinion angle θp as the numerator, i.e., the target pinion angle θp*. The speed increase value ΔGsir is defined as a value obtained by subtracting "1" from the speed increase ratio Gsir, based on the case where the ratio of the change in the pinion angle θp, i.e., the target pinion angle θp*, to the change in the steering angle θs is "1". In this embodiment, the speed increase value ΔGsir is set to a value equal to or greater than zero, i.e., the speed increase ratio Gsir is set to a value equal to or greater than 1, but the speed increase value ΔGsir may be set to a negative value, i.e., the speed increase ratio Gsir may be set to less than 1. The speed increase value ΔGsir obtained in this manner is output to the angle information calculation unit 71.

[0048] The vehicle speed V, the steering angle θs, and the speed increase value ΔGsir are input to the angle information calculation unit 71. The angle information calculation unit 71 calculates the target pinion angle θp* based on the vehicle speed V, the steering angle θs, and the speed increase value ΔGsir.

[0049] Specifically, the angle information calculation unit 71 has a static component calculation unit 72 and a compensation calculation unit 75 including a first compensation calculation unit 73 and a second compensation calculation unit 74 . The steering angle θs and the speed increase value ΔGsir are input to the static component calculation unit 72. The static component calculation unit 72 is configured as a multiplier and calculates the conversion addition angle Δθbs_p by multiplying the steering angle θs by the speed increase value ΔGsir. The conversion addition angle Δθbs_p is an amount of change that increases reflecting the speed increase ratio Gsir. As a result of reflecting the speed increase ratio Gsir, this is a static component that is a component that reflects the steady-state characteristics of the yaw rate response characteristics, which are the behavior of the vehicle. The conversion addition angle Δθbs_p obtained in this manner is output to the first compensation calculation unit 73.

[0050] The vehicle speed V, the steering angle θs, and the conversion addition angle Δθbs_p are input to the first compensation calculation unit 73. The first compensation calculation unit 73 calculates the final conversion addition angle Δθs_p based on the vehicle speed V, the steering angle θs, and the conversion addition angle Δθbs_p.

[0051] Specifically, the first compensation calculation unit 73 has a first constant calculation unit 73a and a first dynamic component calculation unit 73b. The first constant calculation unit 73a receives input of a vehicle speed V and a steering angle θs. The vehicle speed V and the steering angle θs, which are state variables input here, are the same as those input to the speed increase ratio calculation unit 70. The first constant calculation unit 73a includes a first constant map that defines the relationship between the vehicle speed V, the steering angle θs, and a first constant K1. The first constant calculation unit 73a receives input of the vehicle speed V and the steering angle θs and calculates the first constant K1 using the map. The first constant map is set, for example, to have a constant value relative to the steering angle θs and to decrease in value as the vehicle speed V increases. The first constant K1 is a value that indicates a constant of a transfer function, which is a characteristic of the filter processing, for the first dynamic component calculation unit 73b that implements filter processing to adjust frequency characteristics as phase compensation. That is, the first constant K1 is the cutoff frequency of a transfer function for specifying a target frequency during filtering, and corresponds to a filter constant set when implementing a discrete control system as the first dynamic component calculator 73b. The first constant K1 obtained in this manner is output to the first dynamic component calculator 73b.

[0052] The first dynamic component calculator 73b receives the converted addition angle Δθbs_p and the first constant K1. The first dynamic component calculator 73b calculates the final converted addition angle Δθs_p based on the converted addition angle Δθbs_p and the first constant K1. In this embodiment, the first dynamic component calculator 73b is configured as a phase lag filter, for example, a low-pass filter, having a zeroth-order / first-order, i.e., first-order lag, transfer function. The first dynamic component calculator 73b adjusts the pass frequency to, for example, a frequency band of several hertz according to the first constant K1, so as to suppress the absolute value of a so-called yaw rate peak, which is a peak that transiently appears in the yaw rate response characteristics, which represent the behavior of the vehicle. Note that in this embodiment, a low-pass filter having a transfer function with a higher order lag, such as a second-order lag, may be used as the first dynamic component calculator 73b, depending on the degree to which the absolute value of the yaw rate peak is suppressed. The converted addition angle Δθs_p obtained in this manner is output to the adder 76.

[0053] The adder 76 receives the steering angle θs and the conversion addition angle Δθs_p. The adder 76 calculates the steering conversion angle θs_p by adding the steering angle θs and the conversion addition angle Δθs_p obtained through the first compensation calculation unit 73. In other words, the steering conversion angle θs_p is angle information obtained by scaling the steering angle θs so that it becomes a state variable based on the pinion angle θp. The steering conversion angle θs_p obtained in this manner is output to the second compensation calculation unit 74.

[0054] The vehicle speed V, the steering angle θs, and the steering conversion angle θs_p are input to the second compensation calculation unit 74. The second compensation calculation unit 74 calculates the target pinion angle θp* based on the vehicle speed V, the steering angle θs, and the steering conversion angle θs_p.

[0055] Specifically, the second compensation calculation section 74 has a second constant calculation section 74a and a second dynamic component calculation section 74b. The second constant calculation unit 74a receives inputs of the vehicle speed V and the steering angle θs. The vehicle speed V and the steering angle θs, which are state variables, are the same as those input to the speed-up ratio calculation unit 70. That is, the vehicle speed V and the steering angle θs, which are state variables, are the same as those input to the first constant calculation unit 73a. The second constant calculation unit 74a includes a second constant map that defines the relationship between the vehicle speed V, the steering angle θs, and the second constant K2. The second constant calculation unit 74a receives the vehicle speed V and the steering angle θs as inputs and calculates the second constant K2 using the map. The second constant map is set to be a constant value relative to the steering angle θs, for example, and to decrease as the vehicle speed V increases. The second constant K2 is a value that indicates a constant of a transfer function, which is a characteristic of the filter processing, for the second dynamic component calculation unit 74b that implements filter processing to adjust the frequency characteristics as phase compensation. That is, the second constant K2 is the cutoff frequency of the transfer function for specifying the target frequency during filtering, and corresponds to the filter constant set when implementing a discrete control system as the second dynamic component calculator 74b. The second constant K2 obtained in this manner is output to the second dynamic component calculator 74b.

[0056] The second dynamic component calculator 74b receives the steering conversion angle θs_p and a second constant K2. The second dynamic component calculator 74b calculates the target pinion angle θp* based on the steering conversion angle θs_p and the second constant K2. In this embodiment, the second dynamic component calculator 74b is configured as a phase delay filter, for example, a low-pass filter, having a zeroth-order / first-order, i.e., first-order delay, transfer function. The second dynamic component calculator 74b adjusts the pass frequency to, for example, a frequency band of several tens of hertz according to the second constant K2, to reduce so-called high-frequency noise, which is a high-frequency component that appears in the yaw rate response characteristics, which are the behavior of the vehicle. In other words, the second dynamic component calculator 74b performs filtering to reduce noise that appears from a different perspective than that of the first dynamic component calculator 73b. Note that in this embodiment, the second dynamic component calculator 74b may employ a low-pass filter having a transfer function with a higher order delay, such as a second-order delay, depending on the degree of noise reduction.

[0057] <Functions of the angle information calculation unit 71> Of the main functions of the angle information calculation unit 71, the function of adjusting the response characteristics of the yaw rate, which is the behavior of the vehicle, is realized by the functions of the static component calculation unit 72 and the first compensation calculation unit 73.

[0058] For example, as shown in Fig. 4(a), the yaw rate response characteristic of a vehicle at a given vehicle speed V and steering angle θs has a given relationship with frequency. Here, the horizontal axis represents frequency F (Hz), and the vertical axis represents yaw rate gain Kγ (dB), which is the amplitude ratio of the yaw rate to frequency F. In this case, the peak value indicating the magnitude of a peak that transiently appears to exceed the value of "1" in yaw rate gain Kγ is represented by peak value γ0p, with frequency F0 being the resonant frequency.

[0059] As shown in FIG. 4(b), the static component calculation unit 72 reflects the acceleration ΔGsir on the steering angle θs, resulting in an offset so that the absolute value of the yaw rate gain Kγ increases by an amount corresponding to the acceleration ΔGsir. In other words, the yaw rate gain Kγ transitions from the characteristic shown by the dashed line to the characteristic shown by the solid line. In this case, the peak value of the yaw rate gain Kγ changes from the peak value γ0p to the peak value γ1p, which has a larger absolute value. Note that the frequency F1, which is the resonance frequency showing the peak value γ1p, can fluctuate above and below the frequency F0. As a result, the transient peak value of the yaw rate response characteristic increases as the responsiveness increases in accordance with the acceleration ΔGsir.

[0060] In contrast, as shown in FIG. 4(c), the first compensation calculation unit 73 performs filtering using a low-pass filter with a first-order lag transfer function, which results in canceling the peak value γ1p of the yaw rate gain Kγ. In other words, the yaw rate gain Kγ changes from the characteristic shown by the two-dot chain line to the characteristic shown by the solid line. In this case, the cutoff frequency of the low-pass filter is set based on frequency F1, which is the resonance frequency that indicates the peak value γ1p. As a result, the response characteristics of the yaw rate are adjusted to suppress an increase in the transient peak.

[0061] This cutoff frequency is set as the first constant K1 through the function of the first constant calculation unit 73a of the first compensation calculation unit 73. The first constant K1 is calculated using the vehicle speed V and the steering angle θs, which are the same state variables used when calculating the speed increase value ΔGsir. In this case, the first constant K1 is set to a value corresponding to the speed increase value ΔGsir and associated with a peak value that changes depending on the speed increase value ΔGsir. For example, the first constant K1 is set to a value that narrows the range of the cutoff frequency as the peak value increases.

[0062] <Steering angle ratio inverse variable control unit 66> As shown in FIG. 5, the steering angle ratio inverse variable control section 66 has a speed increase ratio conversion section 80 and a steering conversion angle calculation section 81.

[0063] In the speed increase ratio conversion unit 80, the speed increase value ΔGsir is input to an adder 82. The adder 82 calculates the speed increase ratio Gsir by adding "1" stored in a storage unit 83 to the speed increase value ΔGsir. The speed increase ratio Gsir obtained in this way is output to a divider 84. The storage unit 83 is a predetermined storage area of ​​a memory (not shown).

[0064] Then, divider 84 calculates the reverse speed increase ratio Hsir by dividing "1" stored in memory unit 85 by the speed increase ratio Gsir. The reverse speed increase ratio Hsir is the reciprocal of the speed increase ratio Gsir ("1 / Gsir" in FIG. 5), and is an index that indicates the ratio of the amount of change in pinion angle θp, i.e., target pinion angle θp*, with respect to the steering angle θs. In other words, the reverse speed increase ratio Hsir corresponds to a value obtained by using pinion angle θp, i.e., target pinion angle θp*, as the denominator and steering angle θs as the numerator. The reverse speed increase ratio Hsir obtained in this manner is output to steering conversion angle calculation unit 81. Note that memory unit 85 is a predetermined storage area of ​​a memory (not shown).

[0065] In turning conversion angle calculation section 81, pinion angle θp and reverse speed increase ratio Hsir are input to first multiplier 86. First multiplier 86 multiplies pinion angle θp by reverse speed increase ratio Hsir to calculate turning conversion angle θp_s(θp) for pinion angle θp. In other words, turning conversion angle θp_s(θp) is angle information obtained by scaling pinion angle θp so that it becomes a state variable based on steering angle θs. The turning conversion angle θp_s(θp) obtained in this way is output to steering-side control section 50, i.e., target reaction force torque calculation section 52.

[0066] Furthermore, in turning conversion angle calculation section 81, target pinion angle θp* and reverse speed increase ratio Hsir are input to second multiplier 87. Second multiplier 87 multiplies target pinion angle θp* by reverse speed increase ratio Hsir to calculate turning conversion angle θp_s(θp*) for target pinion angle θp*. In other words, turning conversion angle θp_s(θp*) is angle information obtained by scaling target pinion angle θp* so that it becomes a state variable based on steering angle θs. The turning conversion angle θp_s(θp*) obtained in this way is output to steering-side control section 50, i.e., target reaction force torque calculation section 52.

[0067] <Operation of this embodiment> 3, the speed increase value ΔGsir obtained in relation to the speed increase ratio Gsir is calculated based on the vehicle speed V and the steering angle θs, and therefore changes in the vehicle speed V and the steering angle θs appear as changes in the speed increase ratio Gsir, i.e., the speed increase value ΔGsir. In other words, when calculating the target pinion angle θp*, the speed increase ratio Gsir, i.e., the speed increase value ΔGsir, can be used as an index for obtaining an appropriate target pinion angle θp* corresponding to the vehicle speed V and the steering angle θs.

[0068] In this case, when the pinion angle θp or the target pinion angle θp* is reflected in the control of the steering unit 4 as the state of the turning unit 6, the speed increase ratio Gsir related to the speed increase value ΔGsir obtained by the speed increase ratio calculation unit 70 can be reused by making it its inverse.

[0069] Specifically, as shown in Fig. 5, the speed increase ratio conversion section 80 of the steering angle ratio inverse variable control section 66 acquires only the value of the speed increase value ΔGsir. The speed increase ratio conversion section 80 also performs a simple calculation combining the four basic arithmetic operations on the acquired speed increase value ΔGsir, and uses the result as the inverse speed increase ratio Hsir.

[0070] As a result, even when the pinion angle θp or the target pinion angle θp* is reflected in the control of the steering unit 4, there is no need to separately provide a calculation unit for map calculation such as the speed increase ratio calculation unit 70 for converting the pinion angle θp or the target pinion angle θp*. In other words, it is possible to suppress an increase in the capacity of the memory set in relation to the turning-side control unit 60. This is remarkable when calculating a plurality of types of turning conversion angles θp_s for the pinion angle θp and the target pinion angle θp* as in the present embodiment.

[0071] <Effects of the first embodiment> (1-1) In this embodiment, the speed increase ratio Gsir, i.e., the speed increase value ΔGsir, can be used as an index for obtaining an appropriate target pinion angle θp* corresponding to the vehicle speed V and the steering angle θs when calculating the target pinion angle θp*. Furthermore, the speed increase value ΔGsir can be used as the reverse speed increase ratio Hsir when reflecting the pinion angle θp or the target pinion angle θp* in the control of the steering unit 4 as the state of the steered unit 6. Therefore, a useful method can be proposed that uses the speed increase ratio Gsir, which is the ratio of the amount of change in the pinion angle θp, i.e., the target pinion angle θp*, to the amount of change in the steering angle θs, as a method for varying the relationship between the steering angle θs and the pinion angle θp.

[0072] (1-2) In this embodiment, the angle information calculation unit 71 includes a static component calculation unit 72 and a first compensation calculation unit 73. In this case, as explained with reference to Figures 4(a) to 4(c), the responsiveness of the yaw rate response characteristic can be improved in accordance with the speed increase ratio ΔGsir, and transient peak values ​​can be canceled. Therefore, the range of the speed increase ratio Gsir that can be used can be adjusted to suppress an increase in transient peak values.

[0073] (1-3) In this embodiment, the target pinion angle θp* is obtained by adding the steering angle θs and the final conversion addition angle Δθs_p obtained by the first dynamic component calculation unit 73b to the conversion addition angle Δθbs_p. The conversion addition angle Δθbs_p is obtained by the static component calculation unit 72 using the speed increase value ΔGsir corresponding to the value obtained by subtracting the reference value “1” from the speed increase ratio Gsir.

[0074] As a result, even if the steering angle θs is changed so as to increase the speed as a result of using the speed-up ratio Gsir, the effect is limited to the speed-up value ΔGsir of the speed-up ratio. In this case, even if the filtering process is performed by the first dynamic component calculation unit 73b while leaving the original yaw rate response characteristics of the vehicle, it is possible to suitably suppress an increase in a peak that appears transiently in the yaw rate response characteristics.

[0075] (1-4) In this embodiment, the target pinion angle θp* is obtained by performing filtering by the second dynamic component calculation unit 74b. This makes it possible to reduce noise that appears from a perspective other than the transient increase in the peak in the response characteristics of the yaw rate. This is effective in ensuring stability in controlling the operation of the steering unit 6.

[0076] Second Embodiment Hereinafter, a second embodiment of the steering control device will be described. Note that the same components as those in the already described embodiment will be given the same reference numerals, and redundant description will be omitted.

[0077] In a steering angle ratio variable control unit 67 of this embodiment, the function of the steering angle ratio variable control unit 62 of the first embodiment is changed so that the target pinion angle θp* is calculated using the speed increase ratio Gsir. Accordingly, in a steering angle ratio inverse variable control unit 68 of this embodiment, the function of the steering angle ratio inverse variable control unit 66 of the first embodiment is changed.

[0078] <Steering angle ratio variable control unit 67> As shown in FIG. 6, in the steering angle ratio variable control unit 67, the vehicle speed V and the steering angle θs are input to the speed increase ratio calculation unit 90. The speed increase ratio calculation unit 90 is provided with a speed increase ratio map that defines the relationship between the vehicle speed V, the steering angle θs, and the speed increase ratio Gsir. The speed increase ratio calculation unit 90 receives the vehicle speed V and the steering angle θs as input, and calculates the speed increase ratio Gsir using the map. The speed increase ratio map is set, for example, so that the value decreases as the steering angle θs increases and the value decreases as the vehicle speed V increases. The speed increase ratio Gsir obtained in this manner is output to the angle information calculation unit 91 and the steering angle ratio inverse variable control unit 68.

[0079] In the steering angle ratio variable control unit 67, the vehicle speed V, steering angle θs, and speed increase ratio Gsir are input to an angle information calculation unit 91. In the angle information calculation unit 91, the steering angle θs and speed increase ratio Gsir are input to a static component calculation unit 92. The static component calculation unit 92 is configured as a multiplier, and calculates a conversion angle θbs_p as a static component by multiplying the steering angle θs by the speed increase ratio Gsir. The conversion angle θbs_p obtained in this manner is output to a third compensation calculation unit 93 that constitutes the compensation calculation unit 95 of this embodiment.

[0080] In the third compensation calculation unit 93, a vehicle speed V and a steering angle θs are input to a third constant calculation unit 93aa, a fourth constant calculation unit 93ab, and a fifth constant calculation unit 93ac, respectively. The vehicle speed V and the steering angle θs, which are state variables input here, are the same as the state variables input to the speed increase ratio calculation unit 90.

[0081] Specifically, each of the constant calculation units 93aa, 93ab, and 93ac includes a constant map that defines the relationship between the vehicle speed V and steering angle θs and each of the constants K3, K4, and K5. That is, the third constant calculation unit 93aa receives the vehicle speed V and steering angle θs as inputs and calculates the third constant K3 using the map. The fourth constant calculation unit 93ab receives the vehicle speed V and steering angle θs as inputs and calculates the fourth constant K4 using the map. The fifth constant calculation unit 93ac receives the vehicle speed V and steering angle θs as inputs and calculates the fifth constant K5 using the map. Each constant map is set to have a constant value relative to the steering angle θs and to decrease as the vehicle speed V increases.

[0082] The constants K3, K4, and K5 are values ​​indicating constants of the transfer function, which is a characteristic of the filter processing, for the third dynamic component calculation unit 93b that implements filter processing to adjust frequency characteristics as phase compensation. That is, the constants K3, K4, and K5 correspond to filter constants set when implementing a discrete control system as the third dynamic component calculation unit 93b. The third constant K3 is the cutoff frequency of the transfer function for identifying the target frequency during filter processing, and corresponds to "ωf" in equation (3) described below. The fourth constant K4 is the time constant of the transfer function of the filter processing, and corresponds to "Tf" in equation (3) described below. The fifth constant K5 is the damping ratio of the transfer function of the filter processing, and corresponds to "ζf" in equation (3) described below. The constants K3, K4, and K5 thus obtained are output to the third dynamic component calculation unit 93b.

[0083] In the third compensation calculation unit 93, the conversion angle θbs_p and the constants K3, K4, and K5 are input to the third dynamic component calculation unit 93b. The third dynamic component calculation unit 93b calculates the steering conversion angle θs_p based on the conversion angle θbs_p and the constants K3, K4, and K5. In this embodiment, the third dynamic component calculation unit 93b includes a second-order / first-order transfer function and is configured as a multiple phase compensation filter in which a plurality of filters having first-order / second-order transfer functions are cascaded.

[0084] For example, it is assumed that the yaw rate response characteristics of the vehicle are originally given by the following equations (1) and (2), which are defined based on the relationship between the yaw rate and the steering angle of the front wheels.

[0085]

number

[0086] In contrast to this, for example, the transfer function "Qf" of the third dynamic component calculation unit 93b is defined as the following equation (3).

[0087]

number

[0088] The third dynamic component calculation unit 93b functions to cancel "Qv," which is the linear / quadratic transfer function originally possessed by the vehicle, in the denominator of "Qf," and replace it with a linear / quadratic transfer function defined by the constants K3, K4, and K5 in the numerator of "Qf." In this case, the third dynamic component calculation unit 93b performs adjustment so as to suppress the absolute value of the yaw rate peak that appears transiently in the yaw rate response characteristics by replacing it with the linear / quadratic transfer function defined by the constants K3, K4, and K5. The steering conversion angle θs_p obtained in this manner is output to a fourth compensation calculation unit 94 that constitutes the compensation calculation unit 95 of this embodiment.

[0089] The fourth compensation calculation unit 94 has a function corresponding to the second compensation calculation unit 74 of the first embodiment. Specifically, the fourth compensation calculation unit 94 has a sixth constant calculation unit 94a as a function corresponding to the second constant calculation unit 74a of the second compensation calculation unit 74 of the first embodiment. Similar to the second constant calculation unit 74a, the sixth constant calculation unit 94a receives the vehicle speed V and the steering angle θs as input. Similarly to the second constant calculation unit 74a, the sixth constant calculation unit 94a calculates a sixth constant K6 corresponding to the second constant K2 based on the vehicle speed V and the steering angle θs. The sixth constant K6 obtained in this manner is output to the fourth dynamic component calculation unit 94b.

[0090] The fourth compensation calculator 94 also has a fourth dynamic component calculator 94b as a function corresponding to the second dynamic component calculator 74b of the second compensation calculator 74 of the first embodiment. Similar to the second dynamic component calculator 74b, the fourth dynamic component calculator 94b receives the steering conversion angle θs_p and the sixth constant K6. Similarly to the second dynamic component calculator 74b, the fourth dynamic component calculator 94b calculates the target pinion angle θp* based on the steering conversion angle θs_p and the sixth constant K6.

[0091] <Functions of the angle information calculation unit 91> Of the main functions of the angle information calculation unit 91, the function of adjusting the response characteristics of the yaw rate, which is the behavior of the vehicle, is realized by the functions of the static component calculation unit 72 and the first compensation calculation unit 73.

[0092] As a result of reflecting the speed increase ratio Gsir to the steering angle θs through the function of the static component calculation unit 92, the above equation (1) becomes the following equation (4), which is defined by replacing "Gd" with "Gf", which is a value corresponding to the speed increase ratio Gsir.

[0093]

number

[0094] On the other hand, the above formula (4) undergoes filtering by multiple filters having the transfer function of the above formula (3) through the function of the third compensation calculation unit 93, resulting in the following formulas (5) and (6): Then, as a result of the above formula (4) passing through the following formulas (5) and (6), it becomes the following formula (7) which is defined by replacing "Qv" with the transfer function corresponding to the numerator of "Qf".

[0095]

number

[0096] <Steering angle ratio inverse variable control unit 68> As shown in Fig. 7, in steering angle ratio inverse variable control section 68, in speed increase ratio conversion section 100, divider 102 calculates the inverse speed increase ratio Hsir by dividing "1" stored in memory section 103 by the speed increase ratio Gsir, as in the first embodiment. The inverse speed increase ratio Hsir obtained in this manner is output to steering conversion angle calculation section 101. Note that memory section 103 is a predetermined storage area of ​​a memory (not shown).

[0097] Turning conversion angle calculation section 101 has a function corresponding to that of turning conversion angle calculation section 81 of the first embodiment described above. Specifically, turning conversion angle calculation section 101 has a third multiplier 104 as a function corresponding to that of first multiplier 86 of turning conversion angle calculation section 81 of the first embodiment described above. Like first multiplier 86 described above, pinion angle θp and reverse speed increase ratio Hsir are input to third multiplier 104. Like first multiplier 86 described above, third multiplier 104 multiplies pinion angle θp by reverse speed increase ratio Hsir to calculate turning conversion angle θp_s(θp) for pinion angle θp. The turning conversion angle θp_s(θp) obtained in this way is output to steering-side control section 50, i.e., target reaction force torque calculation section 52.

[0098] Furthermore, turning conversion angle calculation section 101 has a fourth multiplier 105 as a function corresponding to second multiplier 87 of turning conversion angle calculation section 81 of the first embodiment. Like second multiplier 87, fourth multiplier 105 receives as input target pinion angle θp* and reverse speed increase ratio Hsir. Like second multiplier 87, fourth multiplier 105 multiplies target pinion angle θp* by reverse speed increase ratio Hsir to calculate turning conversion angle θp_s(θp*) for target pinion angle θp*. The turning conversion angle θp_s(θp*) obtained in this way is output to steering-side control section 50, i.e., target reaction force torque calculation section 52.

[0099] <Effects of the second embodiment> According to this embodiment, in addition to the effects equivalent to those of the first embodiment, the following effects are achieved.

[0100] (2-1) In this embodiment, the target pinion angle θp* is obtained based on the conversion angle θbs_p. The conversion angle θbs_p is obtained by the static component calculation unit 92 using the speed increase ratio Gsir.

[0101] As a result, if the steering angle θs is converted so as to increase the speed as a result of using the speed-increase ratio Gsir, the effect of this will extend to the value of the speed-increase ratio Gsir. In this case, the third dynamic component calculation unit 93b can perform filtering while canceling out the transient characteristics of the yaw rate response characteristics that the vehicle originally has. Therefore, even if the steering angle θs is converted using the speed-increase ratio Gsir, it is possible to suitably suppress an increase in the peak that appears transiently in the yaw rate response characteristics.

[0102] <Other embodiments> The above-described embodiments may be modified as follows: In addition, the following other embodiments may be combined with each other within the scope of technical compatibility.

[0103] In the first embodiment, the speed increase ratio calculation unit 70 only needs to use a state variable that changes depending on the operating state of at least one of the steering device 2 and the vehicle. In this case, the speed increase ratio calculation unit 70 may use only one of the vehicle speed V and the steering angle θs, or may use a combination of other elements. Note that, as the state variable that changes depending on the operating state of the steering device 2, the steering speed, which is the differential value of the steering angle θs obtained from the steering unit 4, or the steering speed, which is the differential value of the pinion angle θp or the target pinion angle θp* obtained from the steering unit 6, can be used. This is also true for the second embodiment. In other words, the speed increase ratio calculation unit 90 only needs to use a state variable that changes depending on the operating state of at least one of the steering device 2 and the vehicle. In this case, the speed increase ratio calculation unit 90 only needs to use one of the vehicle speed V and the steering angle θs, or may use a combination of other elements.

[0104] In the first embodiment, the speed increase ratio map of the speed increase ratio calculation unit 70 can be changed as appropriate, for example, by setting it so that the value changes linearly as the steering angle θs increases and decreases, or by setting it so that the value increases as the steering angle θs increases. The same applies to the speed increase ratio map of the speed increase ratio calculation unit 90 in the second embodiment.

[0105] In the first embodiment, when calculating the conversion addition angle Δθs_p, the first compensation calculation unit 73 may use state variables including at least the vehicle speed V and the steering angle θs, i.e., the same state variables as those input to the speed increase ratio calculation unit 70. In this case, the first compensation calculation unit 73 may use other elements in combination with the vehicle speed V and the steering angle θs. This is the same as in the second embodiment. In other words, when calculating the steering conversion angle θs_p, the third compensation calculation unit 93 may use state variables including at least the vehicle speed V and the steering angle θs, i.e., the same state variables as those input to the speed increase ratio calculation unit 90.

[0106] In the first embodiment, when calculating the conversion addition angle Δθs_p, the first compensation calculation unit 73 can use only one of the vehicle speed V and the steering angle θs, or can do without using the vehicle speed V or the steering angle θs. In this case, the first compensation calculation unit 73 uses a state variable different from that input to the speed increase ratio calculation unit 70. This is the same as in the second embodiment. In other words, when calculating the steering conversion angle θs_p, the third compensation calculation unit 93 can use only one of the vehicle speed V and the steering angle θs, or can do without using the vehicle speed V and the steering angle θs.

[0107] In the first embodiment, when calculating the target pinion angle θp*, the second compensation calculation unit 74 may use state variables that include at least the vehicle speed V and the steering angle θs, i.e., the same state variables as those input to the speed increase ratio calculation unit 70. In this case, the second compensation calculation unit 74 may use a combination of other elements in addition to the vehicle speed V and the steering angle θs. This is the same as in the second embodiment. In other words, when calculating the target pinion angle θp*, the fourth compensation calculation unit 94 may use state variables that include at least the vehicle speed V and the steering angle θs, i.e., the same state variables as those input to the speed increase ratio calculation unit 90.

[0108] In the first embodiment, when calculating the target pinion angle θp*, the second compensation calculation unit 74 can use only one of the vehicle speed V and the steering angle θs, or can avoid using the vehicle speed V and the steering angle θs. In this case, the second compensation calculation unit 74 uses a state variable different from that input to the speed increase ratio calculation unit 70. This is the same as in the second embodiment. In other words, when calculating the target pinion angle θp*, the fourth compensation calculation unit 94 can use only one of the vehicle speed V and the steering angle θs, or can avoid using the vehicle speed V and the steering angle θs.

[0109] In the first embodiment, the first constant map of the first constant calculation unit 73a can be changed as needed, for example, by setting the value to decrease as the steering angle θs increases. The same applies to the second constant map and the constant maps of the constant calculation units 93aa, 93ab, and 93ac in the second embodiment.

[0110] In the first embodiment, the second compensation calculator 74 may be omitted from the compensation calculator 75. In this case, the first compensation calculator 73 may also be omitted from the angle information calculator 71, i.e., the compensation calculator 75 itself may be omitted. Alternatively, the first compensation calculator 73 may be omitted from the compensation calculator 75, while the second compensation calculator 74 remains. This is similar to the second embodiment, where the fourth compensation calculator 94 from the compensation calculator 95 may be omitted, or the third compensation calculator 93 may also be omitted, i.e., the compensation calculator 95 itself may be omitted. Alternatively, the third compensation calculator 93 may be omitted from the compensation calculator 95, while the fourth compensation calculator 94 remains.

[0111] As shown by the two-dot chain line in FIG. 5, in the first embodiment, in addition to the pinion angle θp or the target pinion angle θp*, an intermediate control variable θinf obtained in the process of obtaining the target pinion angle θp* may be input to turning conversion angle calculation unit 81. The function of calculating such intermediate control variable θinf is realized as a function of steering angle ratio variable control unit 62. In this case, in turning conversion angle calculation unit 81, fifth multiplier 88 multiplies the intermediate control variable θinf by the reverse speed increase ratio Hsir to calculate the turning conversion angle θp_s(θinf) for the intermediate control variable θinf. The turning conversion angle θp_s(θinf) obtained in this way is output to steering-side control unit 50, i.e., target reaction force torque calculation unit 52. This is the same as in the second embodiment, as shown by the two-dot chain line in FIG. 7. That is, in addition to the pinion angle θp or the target pinion angle θp*, the intermediate control amount θinf is input to turning conversion angle calculation section 101. In this case, in turning conversion angle calculation section 101, sixth multiplier 106 multiplies the intermediate control amount θinf by the reverse speed increase ratio Hsir to calculate the turning conversion angle θp_s(θinf) for the intermediate control amount θinf.

[0112] In the above-described other embodiment, the intermediate control amount θinf is obtained in the process of obtaining the target pinion angle θp*, and may also include information stored in the turning-side control unit 60 as information related to the turning unit 6, such as steering limit information indicating the steering limit of the steered wheels 5. The steering limit information can be used to calculate a reaction force for informing the driver of a situation in which the steering limit of the steering wheel 3 is reached. In this case, the steering limit information is appropriately used by the target reaction force torque calculation unit 52 as angle information scaled to become a state variable based on the steering angle θs.

[0113] In the first embodiment, the turning conversion angle θp_s obtained through the turning conversion angle calculation unit 81 may be output to a vehicle control device provided in the vehicle separately from the steering control device 1. An example of a vehicle control device is a stable driving control device that controls the braking amount of the vehicle's brake mechanism so as to change the yaw rate generated in the vehicle. Another example of a vehicle control device is a driving assistance control device that controls the operation of the steering unit 6, i.e., the steering device 2, to provide various driving assistance functions to further improve vehicle comfort. Another example of a vehicle control device is a route guidance control device that controls the display content of a back guide monitor provided in the vehicle cabin to provide guidance on the predicted route of the vehicle. This also applies to the second embodiment. That is, the turning conversion angle θp_s obtained through the turning conversion angle calculation unit 101 may be output to the vehicle control device.

[0114] In the first embodiment, any one of the multipliers 86 and 87 may be eliminated from the turning conversion angle calculation unit 81. This is also true for the second embodiment, where any one of the multipliers 104 and 105 from the turning conversion angle calculation unit 101 may be eliminated.

[0115] In the first embodiment, the first multiplier 86 in the turning conversion angle calculation unit 81 can also be changed to a divider. In this case, the divider calculates the turning conversion angle θp_s(θp) by dividing the pinion angle θp by the speed increase ratio Gsir obtained through the speed increase ratio conversion unit 80. In this case, the divider 84 of the speed increase ratio conversion unit 80 and the storage unit 85 can be eliminated from the first embodiment. This also applies to the second multiplier 87 and the multipliers 104, 105 of the turning conversion angle calculation unit 101 in the second embodiment. In this case, the speed increase ratio conversion unit 100 can be eliminated from the second embodiment.

[0116] In the first embodiment, at least a part of the steering angle ratio variable control section 62 and the steering angle ratio inverse variable control section 66 may be realized as a function of the steering-side control section 50. For example, the steering angle ratio variable control section 62 of the steering angle ratio variable control section 62 and the steering angle ratio inverse variable control section 66 may be realized as a function of the steering-side control section 50. This is the same for the second embodiment. In other words, at least a part of the steering angle ratio variable control section 67 and the steering angle ratio inverse variable control section 68 may be realized as a function of the steering-side control section 50.

[0117] In each of the above embodiments, when calculating the target reaction torque command value Ts*, the target reaction torque calculation unit 52 needs to use at least a state variable that changes depending on the operating state of the steering wheel 3. In this case, the target reaction torque calculation unit 52 does not need to use the vehicle speed V or the steering torque Th, or may use a combination of other elements.

[0118] In each of the above embodiments, the steering-side control unit 50 may calculate, as the target reaction torque command value Ts*, a value calculated by executing torque feedback control that causes the steering torque Th to follow the target steering torque calculated based on the steering torque Th.

[0119] In each of the above embodiments, the steering angle calculation unit 51 may take into account the amount of torsion of the steering shaft 11 that corresponds to the steering torque Th, and calculate the steering angle θs by taking into account the amount of torsion by adding or subtracting from the rotation angle θa.

[0120] In each of the above embodiments, the steering angle θs may be determined using the detection result of a steering sensor provided on the steering shaft 11 to detect the rotation angle of the steering shaft 11.

[0121] In each of the above embodiments, the steered-side motor 32 may be, for example, one that is arranged coaxially with the rack shaft 22, or one that is connected to the rack shaft 22 via a worm and wheel to a pinion shaft that constitutes a rack-and-pinion mechanism.

[0122] In each of the above embodiments, the steering control device 1 can be configured by 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 executes at least some of the various processes; or 3) a combination thereof. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., a non-transitory computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0123] In each of the above embodiments, the steering device 2 has a linkless structure in which the steering unit 4 and the steered unit 6 are mechanically separated at all times, but this is not limiting, and the steering unit 4 and the steered unit 6 may be mechanically separated by a clutch. Also, the steering device 2 may have an independently steerable structure in which the steered unit 6 can steer the left and right steered wheels 5 independently.

[0124] In each of the above embodiments, the steering conversion angle θp_s obtained through the steering conversion angle calculation unit 81, 101 may be applied to functions realized by a four-wheel steering device, a rear-wheel steering device, or other devices of the vehicle other than those exemplified in each of the above embodiments. [Explanation of symbols]

[0125] 1...Steering control device 2...Steering device 3...Steering wheel 4...Steering section 5...Steering wheel 6...Rudder section 60...Steering side control unit (control unit) 62, 67... Steering angle ratio variable control unit 70,90...Speed-up ratio calculation section 71, 91...Angle information calculation section 72,92...Static component calculation section 73...First compensation calculation section 73b...first dynamic component calculation unit (phase delay filter) 74...Second compensation calculation section 74b...Second dynamic component calculation unit (phase delay filter) 75,95...compensation calculation section 93...Third compensation calculation section 93b...Third dynamic component calculation unit (phase compensation filter) 94...Fourth compensation calculation section 94b...Fourth dynamic component calculation unit (phase delay filter)

Claims

1. A steering control device that controls at least the steering unit of a steering device including a steering unit that enables steering of a steering wheel of a vehicle and a turning unit that operates to turn steered wheels of the vehicle, the steering unit having a structure in which a power transmission path between the steering unit and the steering unit is separated, a control unit that calculates a steering control amount for operating the steering unit based on angle information obtained in relation to a steering angle, which is an angle at which the steering wheel is steered, and controls the operation of the steering unit based on the steering control amount, The control unit a speed increase ratio calculation unit that calculates a speed increase ratio indicating a ratio of a change in a steering angle, which is the angle of the steered wheels, to a change in the steering angle, based on state variables that change depending on the operating state of at least one of the steering device and a vehicle equipped with the steering device; an angle information calculation unit that converts the steering angle using the speed increase ratio obtained by the speed increase ratio calculation unit to calculate the angle information, The angle information calculation unit a static component calculation unit that calculates a static component, which is a component that reflects a steady-state characteristic of a yaw rate response characteristic that is a behavior of the vehicle with respect to the angle information, as a result of converting the steering angle using the speed increase ratio; and a compensation calculation unit that calculates the angle information by phase-compensating the static component based on the state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit in order to adjust a transient characteristic of the response characteristics of the yaw rate that appears in relation to the calculation of the static component, The compensation calculation unit is configured to adjust the transient characteristics related to the yaw rate gain, which appear transiently in the response characteristics of the yaw rate, and to perform phase compensation so as to keep the absolute value of the peak value of the yaw rate gain small.

2. the static component calculation unit calculates the static component using an increase in the speed increase ratio, which is a difference between a reference value where a ratio of a change in the steering angle, which is the angle of the steered wheels, to a change in the steering angle is 1; the compensation calculation unit is configured as a phase lag filter whose transfer function changes based on the state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit so as to perform phase lag compensation, 2. The steering control device according to claim 1, wherein the control unit is configured to calculate the steering control amount based on a result obtained by adding the steering angle and the angle information obtained by the phase delay filter.

3. the static component calculation unit calculates the static component using the speed increase ratio, the compensation calculation unit is configured as a phase compensation filter whose transfer function changes based on the state variables including at least the state variables used for calculation by the speed increase ratio calculation unit so as to perform phase compensation, the phase compensation filter is configured to include an inverse function obtained by exchanging a numerator and a denominator of a transfer function that indicates the transient characteristic related to a yaw rate gain, which transiently appears in the response characteristic of the yaw rate, 2. The steering control device according to claim 1, wherein the control unit is configured to calculate the steering control amount based on the angle information obtained by the phase compensation filter.

4. The steering control device according to any one of claims 1 to 3, wherein the compensation calculation unit further includes a phase lag filter whose transfer function changes based on the state variables including at least the state variables used in the calculation by the speed increase ratio calculation unit so as to perform phase lag compensation that reduces noise that appears transiently in the response characteristics of the yaw rate that appears in relation to the calculation of the static component and that appears from a perspective different from the transient characteristics related to the yaw rate gain.

Images