Steering control device and steering control method

Abstract

Provided is a steering control device (1) comprising a reaction force command value calculation unit (61) configured to calculate a reaction force command value (T*), which is a command value for an operation reaction force, so as to reflect a reaction force component (Fa) calculated on the basis of an operation amount (θ1) of an operation lever (11) and a control signal generation unit (63) configured to generate a control signal for operating an operation unit (4) on the basis of the reaction force command value (T*). The reaction force command value calculation unit (61) is configured to carry out holding state determination processing which determines whether or not a holding condition for detecting a holding state in which the operation amount (θl) is held constant is satisfied and calculation mode switching processing of switching a calculation mode of the reaction force command value (T*) to a holding-time calculation mode when the holding condition is satisfied. The holding-time calculation mode is configured such that a dead zone (R), which is a range in which the reaction force component (Fa) does not change in response to the operation amount (θl), is wide compared with that in a normal-time calculation mode.

Description

[Technical Field]

[0001] The present disclosure relates to a steering control device and a steering control method. [Background technology]

[0002] Conventionally, there is a steer-by-wire steering device in which the power transmission path between an operation unit to which a steering wheel is connected and a steering unit that steers the steered wheels is separated. For example, as described in Patent Document 1, a steering control device that controls such a steering device changes the angle ratio of the steering angle of the steered wheels to the steering angle of the steering wheel depending on the driving conditions of the vehicle.

[0003] Patent Document 2 discloses a vehicle that employs a joystick as an operating member operated by a driver in addition to or instead of a steering wheel. When such a joystick is operated, a reaction torque is applied in accordance with the amount of operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-30837 [Patent Document 2] Japanese Patent Application Publication No. 8-34353 Summary of the Invention [Problem to be solved by the invention]

[0005] When applying a reaction torque according to the amount of joystick operation as described above, for example, by keeping the amount of joystick operation constant by the driver, a state in which a reaction torque according to that amount of operation is applied is maintained. In this case, the driver is maintained in a state in which a reaction torque is applied through the joystick. In other words, when keeping the amount of joystick operation constant, the driver needs to continuously apply a force according to the reaction torque to the joystick. This places a burden on the driver. [Means for solving the problem]

[0006] One aspect of the present disclosure provides a steering control device for controlling a steering device of a vehicle. The steering device has a structure in which a power transmission path is separated between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels. The steering control device includes: a reaction force command value calculation unit configured to calculate a reaction force command value that is a command value for the operation reaction force so as to reflect a reaction force component calculated based on state variables obtained from the vehicle; and a control signal generation unit configured to generate a control signal for operating the operation unit based on the reaction force command value. The reaction force command value calculation unit includes a hold operation calculation mode and a normal operation calculation mode as calculation modes for the reaction force command value. The normal operation calculation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant. The hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the manipulated variable is held constant, and the reaction force command value has an absolute value smaller than that of the reaction force command value calculated in the normal calculation mode. The reaction force command value calculation unit is configured to execute a hold-state determination process to determine whether a hold condition for detecting the hold state is satisfied, and a calculation mode switching process to switch the calculation mode of the reaction force command value to the hold-time calculation mode when the hold condition is satisfied. The hold-time calculation mode is configured so that a dead zone, which is a range in which the reaction force component does not change with respect to the manipulated variable, is larger than that in the normal calculation mode.

[0007] Another aspect of the present disclosure provides a steering control device for controlling a steering device of a vehicle. The steering device has a structure in which a power transmission path is separated between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels. The steering control device includes: a reaction force command value calculation unit configured to calculate a reaction force command value that is a command value for the operation reaction force so as to reflect a reaction force component calculated based on state variables obtained from the vehicle; and a control signal generation unit configured to generate a control signal for operating the operation unit based on the reaction force command value. The reaction force command value calculation unit includes a hold-time calculation mode and a normal-time calculation mode as calculation modes for the reaction force command value. The normal-time calculation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant. The hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the manipulated variable is held constant, and is a mode in which the reaction force command value has an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode. The reaction force command value calculation unit is configured to execute a hold-state determination process that determines whether a hold condition for detecting the hold state is satisfied, and a calculation mode switching process that switches the calculation mode of the reaction force command value to the hold-time calculation mode when the hold condition is satisfied. The normal-time calculation mode and the hold-time calculation mode each have a relationship of the reaction force component with the manipulated variable. The origin of the relationship in the hold-time calculation mode is configured to be shifted toward the manipulated variable when it is determined that the hold condition is satisfied, compared to the origin of the relationship in the normal-time calculation mode.

[0008] A further aspect of the present disclosure provides a steering control method for controlling a steering device of a vehicle. The steering device has a structure in which a power transmission path is separated between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels. The steering control method includes: calculating a reaction force command value that is a command value for the operation reaction force so as to reflect a reaction force component calculated based on state variables obtained from the vehicle; and generating a control signal for operating the operation unit based on the reaction force command value. The calculation of the reaction force command value includes a hold-time calculation mode and a normal-time calculation mode as calculation modes for the reaction force command value. The normal-time calculation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant. The hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the operation amount is held constant, and is a mode in which the reaction force command value has an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode. The calculation of the reaction force command value includes executing a hold state determination process for determining whether a hold condition for detecting the hold state is satisfied, and a calculation mode switching process for switching the calculation mode of the reaction force command value to the hold-time calculation mode when the hold condition is satisfied. The hold-time calculation mode is configured so that a dead zone, which is a range within which the reaction force component does not change with respect to the operation amount, is larger than that in the normal calculation mode.

[0009] Another aspect of the present disclosure provides a steering control method for controlling a steering device of a vehicle. The steering device has a structure in which a power transmission path is separated between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels. The steering control method includes: calculating a reaction force command value that is a command value for the operation reaction force so as to reflect a reaction force component calculated based on state variables obtained from the vehicle; and generating a control signal for operating the operation unit based on the reaction force command value. The calculation of the reaction force command value includes a hold-time calculation mode and a normal-time calculation mode as calculation modes for the reaction force command value. The normal-time calculation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant. The hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the operation amount is held constant, and is a mode in which the reaction force command value has an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode. Calculating the reaction force command value includes executing a hold state determination process for determining whether a hold condition for detecting the hold state is satisfied, and a calculation mode switching process for switching the calculation mode of the reaction force command value to the hold-time calculation mode when the hold condition is satisfied. The normal calculation mode and the hold-time calculation mode each have a relationship of the reaction force component with the manipulated variable. The origin of the relationship in the hold-time calculation mode is configured to be shifted toward the manipulated variable when it is determined that the hold condition is satisfied, compared to the origin of the relationship in the normal calculation mode. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a steering device of a first embodiment and a steering control device that controls the steering device. [Figure 2] FIG. 2 is a block diagram of the steering control device of FIG. [Figure 3] FIG. 3 is a block diagram of a reaction torque command value calculation in FIG. 2. [Figure 4]4A is a diagram showing an example of a normal time map possessed by the steering control device of FIG. 1, and FIG. 4B is a diagram showing an example of a holding time map possessed by the steering control device of FIG. [Figure 5] 3 is a flowchart showing an example of a processing procedure performed by an angle axial force calculation unit of the reaction torque command value calculation unit in FIG. 2. [Figure 6] 3 is a flowchart showing an example of a processing procedure for guard processing by the guard processing unit of FIG. 2; [Figure 7] FIG. 7A is a diagram showing an example of a normal time map provided in the steering control device of the second embodiment, and FIG. 7B is a diagram showing an example of a holding time map provided in the steering control device of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) A first embodiment of the steering control device will be described below with reference to the drawings. (Overall composition) As shown in Fig. 1, a steering control device 1 controls a steer-by-wire steering device 2. The steering device 2 changes the traveling direction of the vehicle by steering steered wheels 3 in response to an operation by the driver. The steering device 2 includes an operation unit 4 that is operated by the driver, and a steering unit 5 that steers the steered wheels 3. The steering device 2 has a structure in which the power transmission paths between the operation unit 4 and the steering unit 5 are mechanically separated.

[0012] The operation unit 4 includes an operating lever 11 operated by the driver and a base 12 that supports the operating lever 11 so that it can tilt. In this embodiment, the base 12 supports the operating lever 11 so that it can tilt laterally, i.e., in the left-right direction, of the vehicle, and the operating lever 11 tilts in the left-right direction when operated by the driver. In other words, the amount of operation by the driver is represented by the tilt angle of the operating lever 11 (hereinafter referred to as the lever tilt angle θl). In other embodiments, the base 12 may support the operating lever 11 so that it can tilt in the front-rear direction of the vehicle.

[0013] In the illustrated example, the operation unit 4 is equipped with a tilt angle sensor 13 that detects the lever tilt angle θl. The lever tilt angle θl is detected as a positive value when the operating lever 11 is tilted to the right and a negative value when the operating lever 11 is tilted to the left, but the opposite may also be true.

[0014] The operation unit 4 also includes a reaction force actuator 15 that applies an operation reaction force, which is a force that resists the operation of the operation lever 11 by the driver. In the example shown in the figure, the reaction force actuator 15 includes a reaction force motor 16 and a link mechanism 17 that transmits the torque of the reaction force motor 16 to the operation lever 11. The link mechanism 17 is configured by connecting a plurality of gears and rotating shafts, for example. The reaction force actuator 15 transmits the rotation of the reaction force motor 16 to the link mechanism 17, and converts it into a corresponding movement of the operation lever 11 at the link mechanism 17, thereby applying a reaction force torque, which is an operation reaction force, to the operation lever 11.

[0015] The steering unit 5 includes a pinion shaft 21, a rack shaft 22 connected to the pinion shaft 21, a rack housing 23 that accommodates the rack shaft 22 so that it can reciprocate, and a rack-and-pinion mechanism 24 that has the pinion shaft 21 and the rack shaft 22. The rack-and-pinion mechanism 24 is configured such that pinion teeth 21a formed on the pinion shaft 21 mesh with rack teeth 22a formed on the rack shaft 22. As a result, the pinion shaft 21 rotates in response to the reciprocating motion of the rack shaft 22. 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 knuckle (not shown) to which the steered wheels 3 are assembled.

[0016] Furthermore, steering unit 5 is equipped with steering actuator 31 that applies a steering force to rack shaft 22 that steers steerable wheels 3. In the example shown, steering actuator 31 is equipped with steering motor 32 and a power transmission mechanism 33 that transmits the torque of steering motor 32 to rack shaft 22. Power transmission mechanism 33 is equipped with a belt mechanism 34 and a ball screw mechanism 35. Steering actuator 31 transmits the rotation of steering motor 32 to ball screw mechanism 35 via belt mechanism 34, and applies the steering force to steerable wheels 3 by converting it into reciprocating motion of rack shaft 22 by ball screw mechanism 35.

[0017] In steering device 2 configured as above, steering force is applied from steering actuator 31 in response to operation of control lever 11 by the driver. This causes rack shaft 22 to reciprocate, changing the steering angle θi of steered wheels 3. In other words, steering actuator 31 steers steered wheels 3 in response to the operation of the driver. At this time, reaction force that resists the operation of the driver is applied to control lever 11 from reaction force actuator 15. In other words, in steering device 2, the force applied by the driver to operate control lever 11 is changed by the reaction torque applied from reaction force actuator 15.

[0018] Steering control device 1 is connected to reaction force motor 16 and steering motor 32, and controls the operation of reaction force motor 16 and steering motor 32. Detection results from various sensors are input to steering control device 1. The various sensors include, for example, tilt angle sensor 13, vehicle speed sensor 41, rotation angle sensor 42, acceleration sensor 43, and yaw rate sensor 44. Vehicle speed sensor 41 detects vehicle speed V, which is the traveling speed of the vehicle. Rotation angle sensor 42 detects rotation angle θt of the rotation shaft of steering motor 32 as a relative angle within a range of 360°. Acceleration sensor 43 in this embodiment detects lateral acceleration GY of the vehicle. In other embodiments, the acceleration sensor may detect vertical acceleration GZ, which detects acceleration in the vertical direction as a positive or negative value. Furthermore, the acceleration sensor that detects vertical acceleration GZ may be connected separately to steering control device 1. Yaw rate sensor 44 detects yaw rate γ of the vehicle. The detection results from these various sensors are examples of state variables. The steering control device 1 then controls the operation of the steering motor 32 based on the input state variables.

[0019] (Steering control device 1) The configuration of the steering control device 1 will be described in detail below. As shown in Fig. 2, steering control device 1 includes microcomputer 51, drive circuit 52, and drive circuit 53. Microcomputer 51 outputs control signals Ms and Mt. Drive circuit 52 supplies power to reaction force motor 16 based on control signal Ms. Drive circuit 53 supplies power to steering motor 32 based on control signal Mt.

[0020] The microcomputer 51, which is a processing circuit, can be configured as (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. Memory, i.e., non-transitory computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. Various controls by the microcomputer 51 are performed by the CPU executing programs stored in the memory at predetermined calculation cycles.

[0021] A typical PWM inverter having a plurality of switching elements such as FETs and IGBTs is employed for the drive circuits 52 and 53. The control signals Ms and Mt are gate on / off signals that define the on / off state of each switching element.

[0022] When microcomputer 51 outputs control signal Ms to drive circuit 52, power corresponding to control signal Ms is supplied from the on-board power supply to reaction motor 16. This causes reaction motor 16 to rotate, and reaction torque is applied to operating lever 11 as described above. In this way, steering control device 1 controls the motor torque generated by reaction motor 16 through the power supply to reaction motor 16, and applies reaction torque to operating lever 11. Furthermore, when microcomputer 51 outputs control signal Mt to drive circuit 53, power corresponding to control signal Mt is supplied from the on-board power supply to turning motor 32. This causes turning motor 32 to rotate, and a turning force is applied to steered wheels 3 as described above. In this way, steering control device 1 controls the motor torque generated by turning motor 32 through the power supply to turning motor 32, and turns steered wheels 3.

[0023] (Microcomputer 51) The configuration of the microcomputer 51 will be described in detail below. The microcomputer 51 outputs the control signals Ms and Mt by having the following control blocks execute calculation processes at predetermined calculation cycles. The vehicle speed V, lever tilt angle θl, rotation angle θt, lateral acceleration GY, and yaw rate γ are input to the microcomputer 51. The microcomputer 51 generates and outputs the control signals Ms and Mt based on these various state variables.

[0024] More specifically, microcomputer 51 comprises a reaction force control section 60 that generates and outputs a control signal Ms, and a steering control section 70 that generates and outputs a control signal Mt. Reaction force control section 60 comprises a reaction force torque command value calculation section 61, a guard processing section 62, and a control signal generation section 63. Steering control section 70 comprises a steering corresponding angle calculation section 71, a target steering corresponding angle calculation section 72, and a control signal generation section 73.

[0025] (Reaction force control unit 60) Reaction torque command value calculation unit 61 receives as input vehicle speed V, lever tilt angle θl, lateral acceleration GY, yaw rate γ, and actual steering current value It. Based on these various state variables, reaction torque command value calculation unit 61 calculates reaction torque command value T* as a reaction command value, which is a command value for reaction torque. Actual steering current value It is information obtained from drive circuit 53 provided corresponding to steering motor 32. Drive circuit 53 has a current sensor (not shown). The current sensor detects actual steering current value It obtained from the value of current for each phase of steering motor 32 flowing through a connection line between drive circuit 53 and the motor coil for each phase of steering motor 32. The current sensor obtains, as current, the voltage drop across a shunt resistor connected to the source side of each switching element in, for example, a PWM inverter included in drive circuit 53. The calculation process of reaction torque command value T* by reaction torque command value calculation unit 61 will be described later.

[0026] More specifically, as shown in FIG. 3, the reaction torque command value calculation unit 61 has an angle axial force calculation unit 81, a current axial force calculation unit 82, and a distribution axial force calculation unit 83. The angular axial force calculation unit 81 receives the vehicle speed V, lever tilt angle θl, lateral acceleration GY, and yaw rate γ as input. The angular axial force calculation unit 81 calculates the angular axial force Fa based on these various state variables. The angular axial force Fa is an ideal value of the axial force determined by an arbitrarily set vehicle model. The angular axial force Fa is an axial force that does not reflect road surface information. The road surface information includes information on minute irregularities that do not affect the lateral behavior of the vehicle and steps that affect the lateral behavior of the vehicle. The angular axial force calculation unit 81 calculates the absolute value of the angular axial force Fa so that, for example, the greater the absolute value of the lever tilt angle θl, the greater the absolute value of the angular axial force Fa. Furthermore, the angular axial force calculation unit 81 calculates the absolute value of the angular axial force Fa so that, for example, the greater the vehicle speed V, the greater the absolute value of the angular axial force Fa. The angular axial force Fa has a torque dimension (N·m). The angular axial force calculation unit 81 also calculates the hold FLG (described later) while calculating the angular axial force Fa. The calculation process of the angular axial force Fa by the angular axial force calculation unit 81 will be described later. The angular axial force Fa is output to the distribution axial force calculation unit 83. The held FLG is output to the guard processing unit 62. In this embodiment, the angular axial force Fa is an example of a reaction force component. In other words, the calculation process executed by the angular axial force calculation unit 81 corresponds to reaction force component calculation process.

[0027] The current axial force calculation unit 82 receives the actual steering current value It. The current axial force calculation unit 82 calculates the current axial force Fb based on the actual steering current value It. The current axial force Fb is an axial force that actually acts on the rack shaft 22, which operates to steer the steered wheels 3, i.e., an estimated value of the axial force actually transmitted to the rack shaft 22. The current axial force Fb is an axial force that reflects the road surface information. For example, the current axial force calculation unit 82 calculates the current axial force Fb on the assumption that the torque applied to the rack shaft 22 by the steering motor 32 is balanced with the torque corresponding to the force applied to the rack shaft 22 through the steered wheels 3. In other words, the current axial force calculation unit 82 calculates the current axial force Fb so that the absolute value of the current axial force Fb increases as the absolute value of the actual steering current value It increases. The current axial force Fb has a dimension of torque (N m). The current axial force Fb is output to the distribution axial force calculation unit 83. In this embodiment, the current axial force Fb is an example of a reaction force component. That is, the calculation process executed by the current axial force calculation unit 82 corresponds to reaction force component calculation process.

[0028] The distribution axial force calculation unit 83 receives the vehicle speed V, the angular axial force Fa, and the current axial force Fb as input. The distribution axial force calculation unit 83 calculates a reaction torque command value T* based on these various state variables. The distribution axial force calculation unit 83 calculates the reaction torque command value T* by adding the angular axial force Fa and the current axial force Fb together at a predetermined distribution ratio. In other words, the distribution axial force calculation unit 83, i.e., the reaction torque command value calculation unit 61, calculates the reaction torque command value T* so that the angular axial force Fa and the current axial force Fb are reflected in the reaction torque command value T*. The distribution axial force calculation unit 83 adjusts the distribution ratio of the angular axial force Fa and the current axial force Fb based on the vehicle speed V. For example, as the vehicle speed V increases, the distribution axial force calculation unit 83 decreases the distribution ratio of the angular axial force Fa and increases the distribution ratio of the current axial force Fb. The reaction torque command value T* is output to the guard processing unit 62. In this embodiment, the calculation process executed by the distribution axial force calculation unit 83 corresponds to reaction force command value calculation process.

[0029] Returning to the explanation of FIG. 2 , the guard processing unit 62 receives as input the vehicle speed V, lateral acceleration GY, yaw rate γ, held FLG, reaction torque command value T*, and difference ΔT*. The guard processing unit 62 calculates a reaction torque command value Tg* after guard processing based on these various state variables. The difference ΔT* is a value obtained through a subtractor 64. The subtractor 64 receives as input the reaction torque command value T*, which is the current value calculated in the current cycle, and the reaction torque command value Tg* after guard processing, which is the previous value calculated in the cycle immediately preceding the current cycle (one cycle before). The reaction torque command value Tg* for the immediately preceding cycle is held by a previous value holding unit 65. The subtractor 64 calculates the difference ΔT* by subtracting the reaction torque command value Tg* for the immediately preceding cycle from the reaction torque command value T*.

[0030] The guard processing unit 62 calculates a reaction torque command value Tg* after guard processing, which limits the reaction torque command value T* so as to limit the difference ΔT* to a difference upper limit value ΔT*lim or less. The difference upper limit value ΔT*lim is a value that is set according to the vehicle speed V, the lateral acceleration GY, and the yaw rate γ. The guard processing of the reaction torque command value Tg* by the guard processing unit 62 will be described later. The reaction torque command value Tg* is output to the control signal generating unit 63.

[0031] The reaction torque command value Tg* is input to the control signal generating unit 63. The control signal generating unit 63 generates a control signal Ms based on this state variable. The control signal generating unit 63 calculates a target reaction torque by performing an F / B calculation based on the reaction torque command value Tg*. As an example, a PID control calculation is used for the F / B calculation, but this is not limiting and a PI control calculation or the like may also be used. Then, the control signal generating unit 63 generates a control signal Ms that causes the reaction motor 16 to generate the target reaction torque using any known technology.

[0032] As described above, the reaction torque command value Tg* used in the F / B calculation is limited so that the difference ΔT* is equal to or less than the upper difference limit value ΔT*lim. In other words, the control signal generator 63 generates the control signal Ms so as to suppress a sudden change in the reaction torque.

[0033] (Steering control unit 70) Rotation angle θt is input to steering response angle calculation unit 71. For example, steering response angle calculation unit 71 counts the number of rotations of steering motor 32 from the midpoint and calculates an integrated angle by integrating rotation angle θt with the midpoint set as a zero value. Then, steering response angle calculation unit 71 calculates steering response angle θp by multiplying this integrated angle by a conversion coefficient based on the reduction ratio of belt mechanism 34, the lead of ball screw mechanism 35, and the rotational speed ratio of rack and pinion mechanism 24. Turning response angle θp is output to control signal generation unit 73 via subtractor 74. In this embodiment, steering response angle θp corresponds to the pinion angle, which is the rotation angle of pinion shaft 21, and the midpoint is the rotation angle of pinion shaft 21 when the vehicle is traveling straight. As described above, pinion shaft 21 rotates in response to the reciprocating motion of rack shaft 22, and therefore the rotation angle of pinion shaft 21, i.e., steering corresponding angle θp, corresponds to a steering corresponding value that is an actual value of a convertible value that can be converted into steering angle θi of steered wheels 3, and steering corresponding angle calculation unit 71 corresponds to a steering corresponding value calculation unit.

[0034] Vehicle speed V and lever tilt angle θl are input to target turning corresponding angle calculation unit 72. Target turning corresponding angle calculation unit 72 calculates target turning corresponding angle θp*, which is a target value of turning corresponding angle θp, based on these various state variables. Target turning corresponding angle θp* is output to control signal generation unit 73 via subtractor 74. In this embodiment, target turning corresponding angle θp* corresponds to a target turning corresponding value, which is a target value of a convertible value that can be converted into turning angle θi of steered wheels 3, and target turning corresponding angle calculation unit 72 corresponds to a target turning corresponding value calculation unit.

[0035] The deviation Δθp is input to the control signal generating unit 73. The deviation Δθp is a value obtained through a subtractor 74. The target turning-corresponding angle θp* and the turning-corresponding angle θp are input to the subtractor 74. The subtractor 74 calculates the deviation Δθp by subtracting the turning-corresponding angle θp from the target turning-corresponding angle θp*.

[0036] Control signal generation unit 73 generates control signal Mt based on this state variable. Control signal generation unit 73 calculates the target steering torque by executing F / B calculation based on deviation Δθp. As an example, a PID control calculation is used for the F / B calculation, but the F / B calculation is not limited to this and may be a PI control calculation or the like. Then, the F / B control unit uses any well-known technology to generate control signal Mt that causes steering motor 32 to generate the target steering torque.

[0037] (Reaction torque command value calculation unit 61) The calculation process of the reaction torque command value T* by the reaction torque command value calculation unit 61 will be described in detail below.

[0038] The reaction torque command value calculation unit 61 calculates a reaction torque command value T* by reflecting the angular axial force Fa calculated by the angle axial force calculation unit 81 and the current axial force Fb calculated by the current axial force calculation unit 82 in the reaction torque command value T* through the distribution axial force calculation unit 83. In other words, the reaction torque command value calculation unit 61 calculates the angular axial force Fa through the calculation processing by the angle axial force calculation unit 81.

[0039] More specifically, as shown in FIG. 3 , the angle axial force calculation unit 81 executes a hold state determination process for determining whether or not a hold condition is satisfied, and a release condition determination process for determining whether or not a release condition is satisfied. As will be described later, the hold condition is a condition for determining whether or not a situation has arisen in which the calculation mode of the reaction torque command value T* for the operation amount of the operating lever 11 is to be switched to a hold calculation mode. The hold condition is set from the viewpoint of being able to detect a hold state in which the lever tilt angle θl, which is the operation amount, is held constant. For example, the hold state includes a state in which the operating lever 11 is tilted and held. The release condition is a condition for determining whether or not a situation has arisen in which the calculation mode of the reaction torque command value T* for the operation amount of the operating lever 11 is to be switched to a normal calculation mode after being switched to the hold calculation mode. The release condition is set from the viewpoint of being able to detect a non-hold state in which the lever tilt angle θl, which is the operation amount, is not held constant.

[0040] The angular axial force calculation unit 81 executes a process of calculating the angular axial force Fa based on the lever inclination angle θl and the vehicle speed V in a holding calculation mode or a normal calculation mode depending on whether the holding condition and the release condition are satisfied. After starting the calculation process of the angular axial force Fa, the angular axial force calculation unit 81 executes the process in the normal calculation mode until the holding condition is satisfied. On the other hand, after the holding condition is satisfied, the angular axial force calculation unit 81 executes the process in the holding calculation mode. Furthermore, the angular axial force calculation unit 81 executes the process in the holding calculation mode from when the holding condition is no longer satisfied until the release condition is satisfied. After the holding condition is no longer satisfied and the release condition is satisfied, the angular axial force calculation unit 81 executes the process in the normal calculation mode.

[0041] As shown in Fig. 2, the reaction torque command value calculation unit 61 includes a memory 61a. The memory 61a stores a plurality of maps 90, which are calculation information used when calculating the reaction torque command value T*. The maps 90 include a normal state map 91 and a holding state map 92, which are used when the angle axial force calculation unit 81 calculates the angle axial force Fa. The normal state map 91 is normal state calculation information used when calculating in the normal state calculation mode. The holding state map 92 is holding state calculation information used when calculating in the holding state calculation mode.

[0042] As shown in FIGS. 4A and 4B , the normal-state map 91 and the holding-state map 92 show the relationship between the lever tilt angle θl, the vehicle speed V, and the angular axial force Fa. That is, the normal-state map 91 and the holding-state map 92 are three-dimensional maps showing the relationship between the lever tilt angle θl and the vehicle speed V and the angular axial force Fa. In the illustrated example, in both the normal-state map 91 and the holding-state map 92, when the lever tilt angle θl is zero, the angular axial force Fa is zero. In both the normal-state map 91 and the holding-state map 92, the absolute value of the angular axial force Fa increases as the absolute value of the lever tilt angle θl increases. In both the normal-state map 91 and the holding-state map 92, the absolute value of the angular axial force Fa increases as the vehicle speed V increases. In addition, the holding-state map 92 has a dead zone R in which the absolute value of the angular axial force Fa is maintained at zero even when the lever tilt angle θl changes. The normal-state map 91 does not have a dead zone for the angular axial force Fa with respect to changes in the lever tilt angle θl. That is, in the holding-state map 92, the range of the dead zone R is set to be larger than the range in which the absolute value of the angular axial force Fa is maintained at zero even when the lever tilt angle θl changes in the normal-state map 91. Furthermore, the absolute value of the angular axial force Fa in the holding-state map 92 is set to a value shifted toward the positive value side, which is the right side in the figure, by the amount of the dead zone R, while maintaining the tendency set in the normal-state map 91. As a result, the absolute value of the angular axial force Fa in the holding-state map 92 is smaller than the absolute value of the angular axial force Fa in the normal-state map 91 at any lever tilt angle θl and vehicle speed V. That is, the absolute value of the reaction torque command value T* obtained by reflecting the angular axial force Fa in the holding-state map 92 is smaller than the absolute value of the reaction torque command value T* obtained by reflecting the angular axial force Fa in the normal-state map 91.

[0043] In the normal calculation mode, the angle axial force calculation unit 81 calculates the angle axial force Fa corresponding to the lever tilt angle θl and the vehicle speed V by referring to the normal map 91. On the other hand, in the holding calculation mode, the angle axial force calculation unit 81 calculates the angle axial force Fa corresponding to the lever tilt angle θl and the vehicle speed V by referring to the holding map 92. That is, the angle axial force calculation unit 81 switches the map to be used between the normal calculation mode and the holding calculation mode. As a result, in the holding calculation mode, the angle axial force calculation unit 81 calculates an angle axial force Fa having a smaller absolute value than the angle axial force Fa calculated in the normal calculation mode. That is, in the holding calculation mode, the reaction torque command value calculation unit 61 calculates a reaction torque command value T* having a smaller absolute value than the reaction torque command value T* calculated in the normal calculation mode.

[0044] The angle axial force calculation unit 81 sets a hold FLG as information indicating whether the hold condition and the release condition are satisfied. When the hold condition is satisfied, the hold FLG is set to "1." When the hold FLG is set to "1" and the release condition is satisfied after the hold condition is no longer satisfied, the hold FLG is set to "0 (zero)." On the other hand, when the hold FLG is set to "1" and the hold condition is no longer satisfied, the hold FLG is set to "1" until the release condition is satisfied.

[0045] (Regarding retention and release conditions) The angle and axial force calculation unit 81 determines that the holding condition is met when the following condition is met: (a1) The operation speed ωl of the operating lever 11 is less than the holding threshold ωltha.

[0046] The hold threshold value ωltha is a value within a range within which it can be determined that the driver is holding the operation lever 11. The hold threshold value ωltha is calculated as a value that changes based on the vehicle speed V, the lateral acceleration GY, and the yaw rate γ. The angle axial force calculation unit 81 of this embodiment calculates the operation speed ωl by differentiating the lever inclination angle θl. In other embodiments, a speed sensor may be provided in the operation unit 4, and the operation speed ωl may be detected from the speed sensor.

[0047] As shown in (a1), the holding condition includes a condition based on the result of comparing the magnitude of an operation amount parameter indicating a change in the operation amount of the operating lever 11 with a threshold value. The threshold value of the holding condition is calculated based on driving parameters indicating the driving state of the vehicle. In (a1), the driving parameters are the vehicle speed V, the lateral acceleration GY, and the yaw rate γ.

[0048] The angle axial force calculation unit 81 determines that the release condition is met when the following condition is met: (b1) The operating speed ωl of the operating lever 11 is equal to or greater than the release threshold ωlthb. The release threshold value ωlthb is a value within a range within which it can be determined that the driver is not holding the control lever 11. The release threshold value ωlthb is calculated as a value that changes based on the vehicle speed V, the lateral acceleration GY, and the yaw rate γ. The absolute value of the release threshold value ωlthb is set to be greater than the absolute value of the hold threshold value ωltha. In other words, an intermediate value that does not belong to either the release threshold value ωlthb or the hold threshold value ωltha is included between them. These intermediate values ​​are values ​​that can be used to determine the period until the release condition is met when the hold FLG is set to "1" and the hold condition is no longer met.

[0049] As shown in (b1), the release condition includes a condition based on the result of comparing the magnitude of an operation amount parameter indicating a change in the operation amount of the operating lever 11 with a threshold value. The threshold value of the release condition is calculated based on driving parameters indicating the driving state of the vehicle. In (b1), the driving parameters are the vehicle speed V, the lateral acceleration GY, and the yaw rate γ.

[0050] (Calculation of angular axial force Fa) An example of a processing procedure in which the angular axial force calculation unit 81 in the reaction torque command value calculation unit 61 calculates the angular axial force Fa will be described with reference to the flowchart shown in FIG.

[0051] As shown in the figure, upon acquiring various state variables (step 101), the angular axial force calculation unit 81 calculates the operation speed ωl of the control lever 11 (step 102). Subsequently, the angular axial force calculation unit 81 determines whether or not the holding condition is met (step 103). In step 103, the angular axial force calculation unit 81 calculates a holding threshold value ωltha based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, and determines whether or not the operation speed ωl is less than the holding threshold value ωltha.

[0052] When the angular axial force calculation unit 81 determines that the holding condition is met because the operation speed ωl is less than the holding threshold ωltha (step 103: YES), it sets "1" to the holding FLG (step 104). Subsequently, the angular axial force calculation unit 81 calculates the angular axial force Fa using the holding map 92 (step 105) and ends the processing. The processing in step 103 corresponds to the holding state determination processing, and the processing in step 104 corresponds to the calculation mode switching processing.

[0053] On the other hand, when the angle axial force calculation unit 81 determines that the holding condition is not met because the operation speed ωl is equal to or greater than the holding threshold ωltha (step 103: NO), it determines whether the holding FLG is "1" (step 106). When the holding FLG is "1" (step 106: YES), the angle axial force calculation unit 81 determines whether the release condition is met (step 107). In step 107, the angle axial force calculation unit 81 calculates the release threshold ωlthb based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, and determines whether the operation speed ωl is equal to or greater than the release threshold ωlthb. When the angle axial force calculation unit 81 determines that the release condition is not met because the operation speed ωl is not equal to or greater than the release threshold ωlthb (step 107: NO), it proceeds to the processing of step 105 and performs the corresponding processing.

[0054] On the other hand, when the angular axial force calculation unit 81 determines that the release condition is met because the operation speed ωl is equal to or greater than the release threshold value ωlthb (step 107: YES), it sets "0 (zero)" to the hold FLG (step 108). Next, the angular axial force calculation unit 81 calculates the angular axial force Fa using the normal state map 91 (step 109) and ends the processing. The processing of steps 103, 106, and 107 corresponds to the release state determination processing, and the processing of step 108 corresponds to the calculation mode switching processing.

[0055] (Guard processing unit 62) The guard processing of the reaction torque command value Tg* by the guard processing unit 62 will be described. 2, the guard processing unit 62 executes guard processing to limit the reaction torque command value T* based on the absolute value of the difference ΔT*. The execution conditions for determining whether to execute the guard processing include a condition based on the result of a comparison between the difference ΔT* and the difference upper limit value ΔT*lim. The guard processing unit 62 also executes upper limit value calculation processing to calculate the difference upper limit value ΔT*lim based on the vehicle speed V, lateral acceleration GY, and yaw rate γ.

[0056] In the upper limit speed calculation process, the guard processing unit 62 of this embodiment calculates the upper limit difference value ΔT*lim in accordance with the running state of the vehicle. More specifically, the reaction torque command value T* may change due to a change in the calculation mode of the angle axial force calculation unit 81. In consideration of such a situation, the guard processing unit 62 calculates the difference upper limit value ΔT*lim according to the vehicle running conditions when the calculation mode is switched between the normal calculation mode and the hold calculation mode. The guard processing unit 62 determines whether the calculation mode has been switched between the normal calculation mode and the hold calculation mode based on the hold FLG.

[0057] When the guard processing unit 62 determines that the calculation mode has switched between the normal calculation mode and the hold calculation mode, it calculates the difference upper limit value ΔT*lim based on the vehicle speed V, the lateral acceleration GY, and the yaw rate γ. Then, for example, the guard processing unit 62 is provided with a map or a function formula that indicates the relationship between the vehicle speed V, the lateral acceleration GY, the yaw rate γ, and the difference upper limit value ΔT*lim, and calculates the difference upper limit value ΔT*lim by referring to the map or the function formula.

[0058] In the guard processing, the guard processing unit 62 compares the absolute value of the input difference ΔT* with the difference upper limit value ΔT*lim to determine which is larger. If the absolute value of the difference ΔT* is equal to or smaller than the difference upper limit value ΔT*lim, the guard processing unit 62 outputs the input reaction torque command value T* as is as the reaction torque command value Tg* after the guard processing to the control signal generating unit 63. On the other hand, if the absolute value of the difference ΔT* is greater than the difference upper limit value ΔT*lim, the guard processing unit 62 outputs a value obtained by limiting the absolute value of the input reaction torque command value T* as the reaction torque command value Tg* after the guard processing to the control signal generating unit 63. In this case, the sign of the reaction torque command value Tg* is maintained as the sign of the input reaction torque command value T*, and the absolute value of the reaction torque command value Tg* is limited to a value obtained by adding the difference upper limit value ΔT*lim to the reaction torque command value Tg* of the immediately preceding cycle.

[0059] When the guard processing unit 62 of this embodiment determines that the calculation mode has not been switched, it outputs the input reaction torque command value T* as is as the reaction torque command value Tg* after guard processing to the control signal generating unit 63. However, in other embodiments, in such a case, the guard processing may compare the absolute value of the input difference ΔT* with the difference upper limit value ΔT*lim to determine which is larger, and limit the absolute value of the input reaction torque command value T* depending on the result of the comparison.

[0060] (Regarding guard processing) An example of a procedure for the guard processing unit 62 to perform guard processing on the reaction torque command value T* will be described with reference to the flowchart shown in FIG.

[0061] 6, the guard processing unit 62 acquires various state variables (step 201) and acquires a retained FLG (step 202). Subsequently, the guard processing unit 62 determines whether the retained FLG has changed (step 203). In step 203, the guard processing unit 62 determines whether the current value of the retained FLG acquired in the current cycle is different from the previous value of the retained FLG acquired in the immediately preceding cycle (one cycle ago).

[0062] When the guard processing unit 62 determines that the held FLG has changed because the value of the held FLG acquired in the current cycle is different from the value of the held FLG acquired in the immediately preceding cycle (step 203: YES), it determines whether the execution condition is met (step 204). In step 204, the guard processing unit 62 calculates a difference upper limit value ΔT*lim based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, and determines whether the absolute value of the difference ΔT* is equal to or less than the difference upper limit value ΔT*lim.

[0063] If the guard processing unit 62 determines that the execution condition is met because the absolute value of the difference ΔT* is less than or equal to the difference upper limit value ΔT*lim (step 204: YES), it outputs the reaction torque command value T* as is as the reaction torque command value Tg* (step 205) and terminates the processing.

[0064] On the other hand, if the guard processing unit 62 determines that the execution condition is not met because the absolute value of the difference ΔT* is greater than the difference upper limit value ΔT*lim (step 204: NO), it outputs a value obtained by limiting the absolute value of the reaction torque command value T* as the reaction torque command value Tg* (step 206), and ends the processing. In step 206, the guard processing unit 62 maintains the sign of the reaction torque command value T*, and limits the absolute value to a value obtained by adding the difference upper limit value ΔT*lim to the reaction torque command value Tg* of the immediately preceding cycle. In this embodiment, the processing of steps 205 and 206 corresponds to the guard processing.

[0065] Next, the operation and effects of this embodiment will be described. (1-1) When the driver holds the operation amount of the control lever 11 constant, and thus the holding condition is met, the reaction torque command value calculation unit 61 executes a calculation mode switching process to switch to the holding calculation mode. As a result, when the driver holds the operation amount of the control lever 11 constant, the absolute value of the reaction torque corresponding to the operation amount becomes smaller than in the normal calculation mode. In this case, when the driver holds the operation amount of the control lever 11 constant, the force that the driver continuously applies to the control lever 11 becomes smaller than in the non-hold state. This is effective in reducing the burden on the driver.

[0066] (1-2) When the holding condition is satisfied, the reaction torque command value calculation unit 61 switches the map used to calculate the angular axial force Fa between the normal calculation mode and the normal calculation mode through the calculation mode switching process. As a result, when the amount of operation of the control lever 11 is kept constant by the driver, the reaction torque command value calculation unit 61 can easily calculate a value with a smaller absolute value as the reaction torque corresponding to the amount of operation compared to the normal calculation mode.

[0067] (1-3) The reaction torque command value calculation unit 61 determines whether the holding condition is met based on the result of comparing the magnitude between the operation speed ωl, which indicates the change in the operation amount of the operating lever 11, and the holding threshold value ωltha. This is effective in optimizing the situation in which the mode is switched to the holding calculation mode.

[0068] (1-4) The reaction torque command value calculation unit 61 calculates the holding threshold value ωltha based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, which indicate the vehicle running state. This is effective in optimizing the situation in which the mode is switched to the holding calculation mode.

[0069] (1-5) The reaction torque command value calculation unit 61 normally uses the vehicle speed V, lateral acceleration GY, and yaw rate γ, which are information that can be acquired from any vehicle regardless of the type of vehicle, etc., to determine whether the holding conditions are met. In this case, the scale of changes required to the configuration of the steering control device 1 in order to realize the determination of whether the holding conditions are met is reduced.

[0070] (1-6) The guard processing unit 62 can limit the amount of change in the reaction torque command value T* to the difference upper limit value ΔT*lim or less through the guard processing. This prevents a sudden change in the reaction torque command value T* when switching to the holding calculation mode. Therefore, when switching to the holding calculation mode, the driver is prevented from feeling uncomfortable. This also applies when switching to the normal calculation mode.

[0071] (1-7) The guard processing unit 62 calculates the upper limit difference value ΔT*lim based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, which indicate the vehicle's running state. This makes it possible to suitably prevent the driver from feeling uncomfortable when switching to the holding calculation mode. The same applies when switching to the normal calculation mode.

[0072] (1-8) In the holding operation mode, the reaction torque command value calculation unit 61 calculates the absolute value of the angle axial force Fa out of the angle axial force Fa and the current axial force Fb so as to be smaller than that in the normal operation mode. In this case, the current axial force Fb can be extracted as a reaction component whose absolute value does not need to be made smaller than that in the non-holding state. This is effective in optimizing the reaction torque command value T*.

[0073] (Second embodiment) Next, a second embodiment of the steering control device will be described with reference to the drawings. For the sake of convenience, the same components as those in the first embodiment will be assigned the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

[0074] 7A and 7B, of the normal state map 93 and the held state map 94 of this embodiment, the normal state map 93 has the same configuration as the normal state map 91 of the first embodiment. On the other hand, the held state map 94 can have a different configuration from the held state map 92 of the first embodiment depending on the situation in which the operating lever 11 is held.

[0075] Specifically, the holding map 94 is set so that the absolute value of the holding-time inclination angle θlh, which is the lever inclination angle θl when it is determined that the holding condition is satisfied, corresponds to the origin of the normal-time map 93. That is, the absolute value of the angular axial force Fa in the holding-time map 94 is set to a value shifted toward the positive value side, which is the right side in the figure, by the absolute value of the holding-time inclination angle θlh, while maintaining the tendency set in the normal-time map 93. In this case, the range from zero to the holding-time inclination angle θlh in the holding-time map 94 corresponds to a dead zone in which the absolute value of the angular axial force Fa is maintained at zero with respect to changes in the lever inclination angle θl. That is, in the configuration of this embodiment, when it is determined that the holding condition is satisfied, the angular axial force Fa is not reflected in the reaction torque command value T*. In addition, in the configuration of this embodiment, the range of the dead zone for the angular axial force Fa changes depending on the magnitude of the holding-time inclination angle θlh.

[0076] 5, the angle axial force calculation unit 81 calculates the lever inclination angle θl when the determination in step 103 is YES as the holding-time inclination angle θlh. The angle axial force calculation unit 81 calculates the angle axial force Fa using the holding-time map 94 that is set so that the absolute value of the holding-time inclination angle θlh becomes a point corresponding to the origin of the normal-time map 93. According to this embodiment, the same actions and effects as those of the first embodiment can be achieved.

[0077] (Other embodiments) The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0078] In the first embodiment, the normal state map 91 may have a dead zone for the angular axial force Fa relative to changes in the lever tilt angle θl. This also applies to the normal state map 93 in the second embodiment.

[0079] In the first embodiment, the hold-time map 92 may have a tendency different from that set in the normal-time map 91. In this case, it is sufficient that the absolute value of the angular axial force Fa in the hold-time map 92 is configured to be smaller than the absolute value of the angular axial force Fa in the normal-time map 91 at any lever tilt angle θl and vehicle speed V. This also applies to the hold-time map 94 in the second embodiment.

[0080] In the second embodiment, the hold-time map 94 may be set so that the point corresponding to the origin of the normal-time map 93 approaches the absolute value of the hold-time inclination angle θlh, which is the lever inclination angle θl when it is determined that the hold condition is met. Also, the hold-time map 94 may be set so that the point corresponding to the origin of the normal-time map 93 exceeds the absolute value of the hold-time inclination angle θlh, which is the lever inclination angle θl when it is determined that the hold condition is met.

[0081] In each of the above embodiments, the configuration for calculating the current axial force Fb may be omitted from the reaction torque command value calculation unit 61. In this case, the angle axial force Fa is calculated as the reaction torque command value T*.

[0082] In each of the above embodiments, the reaction torque command value calculation unit 61 may calculate the absolute values ​​of both the angle axial force Fa and the current axial force Fb in the holding calculation mode so as to be smaller than those in the normal calculation mode. Also, the reaction torque command value calculation unit 61 may calculate the absolute value of the current axial force Fb in the holding calculation mode so as to be smaller than those in the normal calculation mode. In this case, the reaction torque command value calculation unit 61 may omit the configuration for calculating the angle axial force Fa.

[0083] In each of the above embodiments, the reaction torque command value calculation unit 61 may calculate a vehicle state quantity axial force that can be calculated based on the vehicle speed V, lateral acceleration GY, and yaw rate γ, instead of the current axial force Fb. Also, the reaction torque command value calculation unit 61 may calculate a tire axial force that is obtained in consideration of the tire force acting on the steered wheels 3, instead of the current axial force Fb. The vehicle state quantity axial force and the tire axial force can also be used by being added to the angle axial force Fa and the current axial force Fb.

[0084] In each of the above embodiments, reaction torque command value calculation unit 61 may be configured to calculate reaction torque command value T* based on vehicle speed V, lever tilt angle θl, and actual steering current value It. In this case, the map used to calculate reaction torque command value T* may be any map that shows the relationship between reaction torque command value T* and lever tilt angle θl, vehicle speed V, and actual steering current value It.

[0085] In each of the above embodiments, the guard processing unit 62 may use only the vehicle speed V, only the lateral acceleration GY, or only the yaw rate γ when calculating the difference upper limit value ΔT*lim. Furthermore, the calculation of the difference upper limit value ΔT*lim may use the vehicle speed V and the lateral acceleration GY, the vehicle speed V and the yaw rate γ, or the lateral acceleration GY and the yaw rate γ. Furthermore, the calculation of the difference upper limit value ΔT*lim may use other factors instead of the vehicle speed V, the lateral acceleration GY, and the yaw rate γ, or a combination of other factors. One possible factor is the vehicle's vertical acceleration GZ. For example, when the vehicle's vertical acceleration GZ is used, a condition for determining whether the vehicle is traveling on a canted road may be set in addition to condition (a1) as a condition for determining whether the holding condition is met. In this case, the reaction torque command value calculation unit 61 may determine whether the holding condition is met, for example, when the vehicle speed V is equal to or greater than a speed threshold and the vertical acceleration GZ is equal to or less than a slope determination threshold. The inclination determination threshold is a value within a range within which it can be determined that the vehicle is traveling on a canted road, and is set in advance to a negative value.

[0086] In each of the above embodiments, the upper limit value of the difference ΔT*lim may be a fixed value. In each of the above embodiments, the guard processing unit 62 may be omitted from the reaction force control unit 60.

[0087] In each of the above embodiments, the control signal generating unit 63 of the reaction force control unit 60 may, when performing F / B calculation, execute guard processing on the deviation between the current command value calculated based on the reaction torque command value T* and the actual current value of the reaction force motor 16. In this case, the control signal generating unit 63 may have a configuration corresponding to the guard processing unit 62. For example, the deviation between the current command value and the actual current value of the reaction force motor 16 is input to the guard processing unit 62 instead of the difference ΔT*.

[0088] In each of the above embodiments, the reaction torque command value calculation unit 61 of the reaction force control unit 60 may perform guard processing on the deviation between the angle axial force Fa of the current cycle and the angle axial force Fa of the immediately preceding cycle when calculating the angle axial force Fa. In this case, the reaction torque command value calculation unit 61 may have a configuration corresponding to the guard processing unit 62. For example, the deviation between the angle axial force Fa of the current cycle and the angle axial force Fa of the immediately preceding cycle is input to the guard processing unit 62 instead of the difference ΔT*.

[0089] In each of the above embodiments, the reaction torque command value calculation unit 61 may use only the vehicle speed V, only the lateral acceleration GY, or only the yaw rate γ when calculating the holding threshold value ωltha. Furthermore, when calculating the holding threshold value ωltha, the reaction torque command value calculation unit 61 may use the vehicle speed V and the lateral acceleration GY, the vehicle speed V and the yaw rate γ, or the lateral acceleration GY and the yaw rate γ. Furthermore, when calculating the holding threshold value ωltha, other elements may be used instead of the vehicle speed V, the lateral acceleration GY, and the yaw rate γ, or a combination of other elements may be used. The other elements may be, for example, the vehicle's vertical acceleration GZ.

[0090] In each of the above embodiments, steering corresponding angle calculation unit 71 may be omitted from steering control unit 70. In this case, for example, steering corresponding angle θp, which is the rotation angle, may be input from a sensor that detects the rotation angle of pinion shaft 21. The sensor may detect the rotation angle of pinion shaft 21 as an absolute angle exceeding the range of 360°.

[0091] In each of the above embodiments, the reaction torque command value calculation unit 61 may calculate the angle axial force Fa using the normal state maps 91 and 93, and then correct the angle axial force Fa to calculate the angle axial force Fa in the holding state calculation mode. In this case, the holding state maps 92 and 94 can be omitted. As a method of correction, for example, the reaction torque command value T* calculated using the normal state maps 91 and 93 may be offset.

[0092] In each of the above embodiments, the reaction torque command value calculation unit 61 may be provided with two or more normal state maps. For example, when a first normal state map and a second normal state map are provided, the first normal state map and the second normal state map may be switched by the driver's operation on the vehicle. In this case, the reaction torque command value calculation unit 61 may be provided with a first hold state map and a second hold state map corresponding to the first normal state map and the second normal state map.

[0093] In each of the above embodiments, the normal calculation information and the hold calculation information may be, for example, a function formula instead of the normal maps 91, 93 and the hold maps 92, 94. In each of the above embodiments, when determining whether the holding condition is met, reaction torque command value calculation unit 61 may use other factors instead of operation speed ωl, or may use other factors in combination. Possible other factors include operation acceleration, which is the amount of change in operation speed ωl, steering response angle θp, and steering speed, which is the amount of change in steering response angle θp.

[0094] In each of the above embodiments, the operating lever 11 may be provided with a torque sensor that detects the operating force of the driver on the operating lever 11. In this case, the detection result of the torque sensor can be used to determine whether the holding condition is met or not, and can also be used to calculate the reaction torque command value T*.

[0095] In each of the above embodiments, the hold threshold value ωltha and the release threshold value ωlthb may be set to the same value. That is, the condition (b1) can be set to that the operating speed ωl of the operating lever 11 is equal to or greater than the hold threshold value ωltha. As a result, the process shown in FIG. 5 can be configured to delete the processes of steps 104, 106, 107, and 108, and to execute the process of step 109 if step 103: NO. In this case, the process shown in FIG. 5 can be configured to execute the process of step 109 after the process of step 101, and to execute the process of step 103 after the process of step 109. Then, after the process of step 103: YES, the process of step 105 can be executed.

[0096] In each of the above embodiments, the processing procedure by the guard processing unit 62 is not limited to the procedure shown in Fig. 6 and can be changed as appropriate. For example, the processing of step 201 may be configured to be executed after the processing of step 204: NO.

[0097] In the above embodiments, the lever tilt angle θl may be detected based on the rotation angle of the reaction force motor 16. In the above embodiments, the convertible value that can be converted into the steering angle θi of the steered wheels 3 is the rotation angle of the pinion shaft 21. However, this is not limited to this. For example, the convertible value may be the stroke amount of the rack shaft 22 or the steering angle θi itself.

[0098] In each of the above embodiments, the operating lever 11 is tiltably supported on the base 12, but this is not limiting and, for example, the operating lever 11 may be supported slidably relative to the base 12. In this case, the amount of operation by the driver is represented by the amount of sliding of the operating lever 11. The operating lever 11 may be used to control the driving / braking of the vehicle in addition to controlling the steering angle θi of the steered wheels 3.

[0099] In each of the above embodiments, the operation unit 4 may include a steering wheel operated by the driver in addition to the operation lever 11. The steering device 2 has a linkless structure in which power transmission between the operation unit 4 and the steering unit 5 is separated, but this is not limited to this. If a steering wheel is provided, the steering device 2 may have a structure in which power transmission between the operation unit 4 and the steering unit 5 can be separated by a clutch.

[0100] In each of the above embodiments, the reaction force control unit 60 and the steering control unit 70 may be separate processing circuits. In this case, the reaction force actuator 15 of the operation unit 4 may be provided with a processing circuit for the reaction force control unit 60. Also, the steering actuator 31 of the steering unit 5 may be provided with a processing circuit for the steering control unit 70.

[0101] In each of the above embodiments, steering actuator 31 transmits the rotation of steering motor 32 to ball screw mechanism 35 via belt mechanism 34, but this is not limiting. For example, steering actuator 31 may be configured so that the rotation of steering motor 32 is transmitted to ball screw mechanism 35 via a gear mechanism. Also, steering actuator 31 may be configured so that steering motor 32 directly rotates ball screw mechanism 35. Furthermore, steering unit 5 may be configured to include a second rack-and-pinion mechanism, and steering actuator 31 may be configured so that the rotation of steering motor 32 is converted into reciprocating motion of rack shaft 22 by the second rack-and-pinion mechanism, thereby applying a steering force to steering unit 5.

[0102] (Other technical ideas) Next, the technical ideas that can be understood from the above-described embodiments and modifications will be described below. (i) The reaction force command value calculation unit is configured to execute a cancellation condition determination process for determining whether or not a cancellation condition for canceling the holding-time calculation mode is satisfied after the holding condition is satisfied, and the calculation mode switching process may include a process for canceling the holding-time calculation mode and switching to the normal-time calculation mode when the cancellation condition is satisfied.

Claims

1. A steering control device that controls a steering device of a vehicle, the steering device has a structure in which a power transmission path between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels is separated, The steering control device includes: a reaction force command value calculation unit configured to calculate a reaction force command value that is a command value of the operation reaction force so as to reflect a reaction force component calculated based on a state variable obtained from the vehicle; a control signal generating unit configured to generate a control signal for operating the operation unit based on the reaction force command value, the reaction force command value calculation unit includes, as calculation modes for the reaction force command value, a holding calculation mode and a normal calculation mode; the normal operation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant, the hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the operation amount is kept constant, and is a mode in which the reaction force command value having an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode is calculated, The reaction force command value calculation unit a holding state determination process for determining whether a holding condition for detecting the holding state is satisfied; a calculation mode switching process for switching a calculation mode of the reaction force command value to the holding time calculation mode when the holding condition is satisfied, A steering control device configured such that the dead zone, which is a range in which the reaction force component does not change with respect to the operation amount, is larger in the holding calculation mode than in the normal calculation mode.

2. A steering control device that controls a steering device of a vehicle, the steering device has a structure in which a power transmission path between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels is separated, The steering control device includes: a reaction force command value calculation unit configured to calculate a reaction force command value that is a command value of the operation reaction force so as to reflect a reaction force component calculated based on a state variable obtained from the vehicle; a control signal generating unit configured to generate a control signal for operating the operation unit based on the reaction force command value, the reaction force command value calculation unit includes, as calculation modes for the reaction force command value, a holding calculation mode and a normal calculation mode; the normal operation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant, the hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the operation amount is kept constant, and is a mode in which the reaction force command value having an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode is calculated, The reaction force command value calculation unit a holding state determination process for determining whether a holding condition for detecting the holding state is satisfied; a calculation mode switching process for switching a calculation mode of the reaction force command value to the holding time calculation mode when the holding condition is satisfied, each of the normal operation mode and the hold operation mode has a relationship of the reaction force component with respect to the operation amount, A steering control device configured such that the origin of the relationship in the holding calculation mode is shifted toward the operation amount when it is determined that the holding condition is met, compared to the origin of the relationship in the normal calculation mode.

3. The steering control device according to claim 1 or 2, the reaction force command value calculation unit includes a memory, the memory stores calculation information indicating a relationship between the operation amount and the reaction force component, the calculation information being used when calculating the reaction force component; the calculation information includes normal operation information used in the normal operation mode and hold operation information used in the hold operation mode, The calculation mode switching process includes a process of switching the calculation information to the holding calculation information when the holding condition is met.

4. The steering control device according to any one of claims 1 to 3, A steering control device, wherein the holding condition includes a condition based on a result of comparing a magnitude of an operation amount parameter indicating a change state of the operation amount with a threshold value.

5. The steering control device according to claim 4, A steering control device, wherein the threshold value of the holding condition is calculated based on a driving parameter indicating a driving state of the vehicle.

6. The steering control device according to claim 5, A steering control device, wherein the driving parameters include at least one of vehicle speed, lateral acceleration, and yaw rate.

7. The steering control device according to any one of claims 1 to 6, a subtractor configured to calculate a difference between a previous value and a current value of the reaction force command value; a guard processing unit configured to execute a guard process that limits the reaction force command value based on the difference, A steering control device, wherein the execution condition for determining whether to execute the guard process includes a condition based on the result of a comparison between the difference and a difference upper limit value.

8. The steering control device according to claim 7, The guard process includes an upper limit value calculation process that calculates the difference upper limit value based on a driving parameter that indicates a driving state of the vehicle.

9. The steering control device according to any one of claims 1 to 8, The reaction force command value calculation unit a reaction force component calculation process for calculating a plurality of reaction force components as the reaction force component; a reaction force command value calculation process for calculating the reaction force command value so as to reflect at least one of the plurality of reaction force components, The holding time calculation mode is a mode in which, in the reaction force component calculation process, calculation is performed so that the absolute value of the at least one reaction force component is smaller than that in the normal time calculation mode.

10. A steering control method for controlling a steering device of a vehicle, comprising: the steering device has a structure in which a power transmission path between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels is separated, The steering control method includes: calculating a reaction force command value that is a command value of the operation reaction force so as to reflect a reaction force component calculated based on a state variable obtained from the vehicle; generating a control signal for actuating the operation unit based on the reaction force command value; calculating the reaction force command value includes a holding calculation mode and a normal calculation mode as calculation modes of the reaction force command value, the normal operation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant, the hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the operation amount is kept constant, and is a mode in which the reaction force command value having an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode is calculated, Calculating the reaction force command value includes: a holding state determination process for determining whether a holding condition for detecting the holding state is satisfied; and executing a calculation mode switching process of switching a calculation mode of the reaction force command value to the holding time calculation mode when the holding condition is satisfied, The steering control method is configured so that the holding calculation mode has a larger dead zone, which is a range in which the reaction force component does not change with respect to the operation amount, than the normal calculation mode.

11. A steering control method for controlling a steering device of a vehicle, comprising: the steering device has a structure in which a power transmission path between an operation unit having an operation lever and configured to apply an operation reaction force to the operation lever in accordance with an operation amount of the operation lever, and a steering unit configured to steer steered wheels is separated, The steering control method includes: calculating a reaction force command value that is a command value of the operation reaction force so as to reflect a reaction force component calculated based on a state variable obtained from the vehicle; generating a control signal for actuating the operation unit based on the reaction force command value; calculating the reaction force command value includes a holding calculation mode and a normal calculation mode as calculation modes of the reaction force command value, the normal operation mode is a mode in which the reaction force command value is calculated in a non-hold state in which the operation amount is not held constant, the hold-time calculation mode is a mode in which the reaction force command value is calculated in a hold state in which the manipulated variable is kept constant, and is a mode in which the reaction force command value having an absolute value smaller than that of the reaction force command value calculated in the normal-time calculation mode is calculated, Calculating the reaction force command value includes: a holding state determination process for determining whether a holding condition for detecting the holding state is satisfied; and executing a calculation mode switching process of switching a calculation mode of the reaction force command value to the holding time calculation mode when the holding condition is satisfied, each of the normal operation mode and the hold operation mode has a relationship of the reaction force component with respect to the operation amount, A steering control method configured such that the origin of the relationship in the holding calculation mode is shifted toward the operation amount when it is determined that the holding condition is satisfied, compared to the origin of the relationship in the normal calculation mode.

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