Steering control device and steering control method

Abstract

A steering control device (1) controls the behavior of a steering device (2) through control of driving of a motor (13) of the steering device. The steering control device (1) includes a control unit (50) that controls the driving of the motor (13). The control unit (50) includes: a control mode determination process for determining a control mode from among a plurality of control modes for achieving the behavior of the steering device (2); a motor control amount calculation process for calculating a motor control amount for controlling the driving of the motor (13); a stabilization constant determination process for determining a stabilization constant from among a plurality of stabilization constants having different characteristics; and a stabilization compensation amount calculation process for calculating a stabilization compensation amount for compensating for the motor control amount. The stabilization constant determination process includes a process for determining the stabilization constant associated with the control mode determined by the control mode determination process.

Description

Steering control device and steering control method

[0006]

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

[0002] For example, Patent Document 1 below describes a vehicle steering device having a vehicle stabilization compensator that calculates a vehicle stabilization current for compensating a basic assist torque current in order to enhance the steering feeling of the vehicle by the driver. Such a vehicle stabilization compensator obtains the vehicle stabilization current by changing the frequency characteristics of vehicle state signals such as the yaw rate generated in the vehicle.

[0003] Japanese Patent Application Laid-Open No. 2006-88866

[0004] In the above vehicle steering device, the steering feeling of the vehicle by the driver is enhanced on the premise that characteristics such as constants related to the calculation of the basic assist torque current are fixed. In this regard, even when characteristics such as constants related to the calculation of the basic assist torque current change, it is desired to enhance the steering feeling of the vehicle by the driver.

[0005] A steering control device according to an aspect of the present disclosure controls the behavior of a steering device of a vehicle through control of driving of a motor included in the steering device of the vehicle. The steering control device includes a control unit configured to control the driving of the motor. The control unit includes a control mode determination process for determining a control mode for controlling the behavior of the steering device from among a plurality of control modes that realize different behaviors of the steering device, a motor control amount calculation process for calculating a motor control amount for controlling the driving of the motor so as to exhibit steering characteristics corresponding to the determined control mode, a stabilization constant determination process for determining a stabilization constant, which is a characteristic for ensuring control stability when controlling the driving of the motor, from among a plurality of stabilization constants having different characteristics, and a stabilization compensation amount calculation process for calculating a stabilization compensation amount corresponding to the determined stabilization constant for compensating the motor control amount. The stabilization constant determination process includes a process for determining the stabilization constant associated with the control mode determined by the control mode determination process.

[0006] A steering control method according to another aspect of the present disclosure is a method for controlling the behavior of a steering system of a vehicle through control of the drive of a motor having a steering system of the vehicle. The steering control method includes: executing a control mode determination process to determine a control mode for controlling the behavior of the steering system from among a plurality of control modes that realize different behaviors of the steering system; executing a motor control amount calculation process to calculate a motor control amount for controlling the drive of the motor so as to exhibit steering characteristics corresponding to the determined control mode; executing a stabilization constant determination process to determine a stabilization constant, which is a characteristic for ensuring control stability when controlling the drive of the motor, from among a plurality of stabilization constants having different characteristics; and executing a stabilization compensation amount calculation process to calculate a stabilization compensation amount corresponding to the determined stabilization constant for compensating the motor control amount. The stabilization constant determination process includes a process for determining the stabilization constant associated with the control mode determined by the control mode determination process.

[0007] This figure shows the overall configuration of the steering device according to the embodiment. This figure shows the functions of the steering control device in Figure 1. This is a block diagram showing the processing contents of the target steering force calculation unit in Figure 2. This is a diagram illustrating the state set by the target steering force calculation unit. This is a flowchart illustrating the processing flow of the stabilization constant determination unit in Figure 3.

[0008] The embodiments will be described below with reference to the drawings. As shown in Figure 1, the steering control device 1 controls the steering device 2. The steering device 2 is, for example, a steering device for a steer-by-wire type vehicle. The steering device 2 comprises a steering unit 4 and a steering unit 6. The steering unit 4 is steered by the driver via the vehicle's steering wheel 3, which is a steering member. The steering unit 6 steers the left and right steering wheels 5 of the vehicle in response to the steering input from the driver to the steering unit 4. In the steering device 2, for example, the power transmission path between the steering unit 4 and the steering unit 6 is mechanically and permanently isolated. The power transmission path between the steering actuator 12 (described later) and the steering actuator 31 (described later) is mechanically and permanently isolated.

[0009] The steering unit 4 comprises a steering shaft 11 and a steering actuator 12. A steering wheel 3 is connected to the steering shaft 11. The steering actuator 12 includes a steering motor 13 and a steering-side reduction mechanism 14. The steering motor 13 is the drive source for the steering actuator 12. The steering motor 13 is a reaction motor that applies a steering reaction force to the steering shaft 11, which is a force that opposes the driver's steering as a steering force. The steering motor 13 is connected to the steering shaft 11 via a steering-side reduction mechanism 14, which consists of, for example, a worm and wheel. The steering motor 13 is, for example, a three-phase brushless motor.

[0010] The steering unit 6 comprises a pinion shaft 21, a steering shaft 22, and a rack housing 23. The pinion shaft 21 and the steering shaft 22 are connected at a predetermined intersection angle. The rack and pinion mechanism 24 is formed by meshing the pinion teeth 21a formed on the pinion shaft 21 with the rack teeth 22a formed on the steering shaft 22. In other words, the pinion shaft 21 corresponds to a rotation axis that can be converted into a steering angle θi, which is the steering position of the steering wheel 5. The rack housing 23 houses the rack and pinion mechanism 24. The first end of the pinion shaft 21 is connected to the steering shaft 22 while housed inside the rack housing 23. The second end of the pinion shaft 21, opposite to the first end, protrudes from the rack housing 23. Both ends of the steering shaft 22 protrude from both ends of the rack housing 23 in the axial direction. Tie rods 26 are connected to both ends of the steering shaft 22 via rack ends 25, which are ball joints. The ends of the tie rods 26 are connected to knuckles to which the left and right steering wheels 5 are assembled.

[0011] The steering unit 6 is equipped with a steering actuator 31. The steering actuator 31 has a steering motor 32, a transmission mechanism 33, and a conversion mechanism 34. The steering motor 32 is the drive source for the steering actuator 31. The steering motor 32 applies a steering force to the steering shaft 22 to steer the steering wheel 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering 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 motor 32 into reciprocating motion of the steering shaft 22 via the conversion mechanism 34, which is for example a ball screw mechanism. The steering motor 32 is, for example, a three-phase brushless motor.

[0012] In the steering system 2 configured in this way, motor torque is applied as a steering force from the steering actuator 31 to the steering shaft 22 in response to steering input by the driver, thereby changing the steering angle θi of the steering wheel 5. At this time, the steering actuator 12 applies a steering reaction force to the steering wheel 3 that opposes the driver's steering input. As a result, in the steering system 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is motor torque applied from the steering actuator 12. In other words, the driver can feel the steering wheel 3.

[0013] The reason for providing the pinion shaft 21 is to support the steering shaft 22 together with the pinion shaft 21 inside the rack housing 23. The steering shaft 22 is supported so as to be movable along its axial direction by the support mechanism provided in the steering device 2, and is also pressed toward the pinion shaft 21. As a result, the steering shaft 22 is supported inside the rack housing 23. However, other support mechanisms may be provided to support the steering shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0014] <Electrical Configuration of the Steering System> As shown in Figure 1, the steering motor 13 and the steering motor 32 are connected to the steering control device 1. The steering control device 1 controls the steering wheel 3, which is the object to be controlled. The steering control device 1 controls the operation of the steering actuator 12 through the drive of the steering motor 13 in order to control the steering reaction force, which is the control amount of the object to be controlled. The steering control device 1 controls the steering wheel 5, which is the object to be controlled. The steering control device 1 controls the operation of the steering actuator 31 through the drive of the steering motor 32 in order to control the steering angle θi of the steering wheel 5, which is the control amount of the object to be controlled. Various sensors are connected to the steering control device 1. Based on the detection results of the various sensors, the steering control device 1 controls the drive of each motor 13 and 32 by controlling the supply of current, which is the control amount of each motor 13 and 32. Examples of various sensors include a torque sensor 41, a steering-side rotation angle sensor 42, a steering-side rotation angle sensor 43, and a vehicle speed sensor 44.

[0015] The torque sensor 41 detects the steering torque Th, which is a value indicating the torque applied to the steering shaft 11 by the driver's steering. The steering-side rotation angle sensor 42 detects the rotation angle θa, which is the angle of the rotation axis of the steering motor 13, within a range of 360°. The steering-side rotation angle sensor 43 detects the rotation angle θb, which is the angle of the rotation axis of the steering motor 32, within a range of 360°. Note that the steering torque Th and each rotation angle θa, θb are detected as positive values ​​when steering to the right, for example, and as negative values ​​when steering to the left. The vehicle speed sensor 44 detects the vehicle speed value V, which is a value indicating the vehicle's travel speed.

[0016] The torque sensor 41 is located on the torsion bar 41a of the steering shaft 11. The steering-side rotation angle sensor 42 is located on the steering motor 13. The rotation angle θa of the steering motor 13 is used to calculate the steering angle θs. The steering 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 motor 13 and the rotation angle of the steering shaft 11, and consequently, the steering angle θs, which is the rotation angle of the steering wheel 3. Thus, the steering angle θs can be determined based on the rotation angle θa of the steering motor 13. The steering-side rotation angle sensor 43 is located on the steering motor 32. The steering motor 32 and the pinion shaft 21 are linked via the steering shaft 22, the transmission mechanism 33, and the conversion mechanism 34. Therefore, there is a correlation between the rotation angle θb of the steering motor 32, the rotation angle of the pinion shaft 21, and consequently the steering angle θi. Thus, the pinion angle θp, which is the rotation angle of the pinion shaft 21, and consequently the steering angle θi can be determined based on the rotation angle θb of the steering motor 32.

[0017] Furthermore, the steering control device 1 is connected to an on-board switch 45 that can be operated by the driver. The switch 45 switches the drive mode DM, which indicates the setting state of the control pattern of the on-board engine, etc. When the steering control device 1 controls the supply of current, which is the control amount of each motor 13, 32, it further refers to the input result of the drive mode DM. Depending on the drive mode DM, the responsiveness of the vehicle to the driver's demands differs, resulting in different ride comfort. The drive mode DM includes a normal mode FM, a sport mode PM, a first extended mode EM1, and a second extended mode EM2. The normal mode FM is, for example, a mode that optimizes the output of the engine, etc. to achieve both low fuel consumption and responsiveness to the driver's demands. The first extended mode EM1 is, for example, a mode that optimizes the output of the engine, etc. to increase responsiveness to the driver's demands regardless of fuel consumption. The second extended mode EM2 is, for example, a mode that optimizes the output of the engine, etc. to increase passenger comfort.

[0018] Furthermore, an on-board driver assistance control device 46 is connected to the steering control device 1. The driver assistance control device 46 controls the behavior of the steering device 2 in order to assist the driver. The driver assistance control device 46 determines the optimal control method based on the vehicle's state at any given time. The driver assistance control device 46 controls the behavior of the steering device 2 according to the determined control method. For example, the driver assistance control device 46 instructs a change in the steering angle θi of the steering wheels 5 to prevent the vehicle from leaving its lane or to assist in emergency avoidance.

[0019] The driver assistance control device 46 is connected to various detection devices for understanding the state of the vehicle, such as a vehicle speed sensor 44 and a camera for lane recognition. Based on the detection results of the above detection devices, the driver assistance control device 46 executes a process to generate a driver assistance request FLG that indicates the optimal control method. When the steering control device 1 controls the supply of current, which is the control amount of each motor 13, 32, it further refers to the input result of the driver assistance request FLG.

[0020] <Functions of the Steering System> Figure 2 shows some of the processes performed by the steering control device 1. Figure 2 shows some of the processes that are realized by the CPU executing a program stored in memory, categorized by the type of process performed.

[0021] The steering control device 1 includes one or more central processing units (CPUs) (not shown) and one or more memories. The CPU executes programs stored in the memories at predetermined calculation cycles. This allows various processes to be executed.

[0022] The CPU and memory constitute a microcomputer, which is a processing circuit. The memory includes computer-readable media such as RAM (Random Access Memory) and ROM (Read Only Memory). However, it is only an example that various processes are implemented by software. The processing circuit of the steering control device 1 may be configured to implement at least some of the processes by hardware circuits such as logic circuits. In this way, various processes are executed in the steering control device 1.

[0023] The steering control device 1 includes a steering-side control unit 50 that controls the power supply to the steering motor 13. The steering-side control unit 50 has a steering-side current sensor 54. The steering-side current sensor 54 detects the steering-side actual current value Ia, which is obtained from the value of the current flowing through the connection lines between the steering-side control unit 50 and the motor coils of each phase of the steering motor 13. The steering-side current sensor 54 acquires the voltage drop across the shunt resistors connected to the source side of each switching element as current in an inverter (not shown) provided in correspondence with the steering motor 13. Note that in Figure 2, for the sake of explanation, the connection lines of each phase and the current sensors of each phase are shown together as one unit. In this embodiment, the steering-side control unit 50 is an example of a control unit.

[0024] Furthermore, the steering control device 1 includes a steering-side control unit 60 that controls the power supply to the steering motor 32. The steering-side control unit 60 has a steering-side current sensor 65. The steering-side current sensor 65 detects the steering-side actual current value Ib, which is obtained from the value of the current flowing through the connection lines between the steering-side control unit 60 and the motor coils of each phase of the steering motor 32. The steering-side current sensor 65 acquires the voltage drop across the shunt resistors connected to the source side of each switching element as current in an inverter (not shown) provided in correspondence with the steering motor 32. Note that in Figure 2, for the sake of explanation, the connection lines of each phase and the current sensors of each phase are shown together as one unit.

[0025] As shown in Figure 2, the steering control unit 50 receives the drive mode DM, driver assistance request FLG, steering torque Th, vehicle speed value V, and steering side actual current value Ib. Based on the drive mode DM, driver assistance request FLG, code signal Sm, steering torque Th, vehicle speed value V, and steering side actual current value Ib, the steering control unit 50 performs a process to control the power supply to the steering motor 13. When controlling the power supply to the steering motor 13, the steering control unit 50 further performs a process that refers to the code signal Sm, which will be described later.

[0026] More specifically, the steering control unit 50 includes a steering angle calculation unit 51, a reaction force control amount calculation unit 52, and a power supply control unit 53. The steering angle calculation unit 51 receives the rotation angle θa. The steering angle calculation unit 51 performs a process to convert the rotation angle θa into an integrated angle that includes a range exceeding 360° by, for example, counting the number of rotations of the steering motor 13 from the steering neutral position, which is the position of the steering wheel 3 when the vehicle is moving straight. The steering angle calculation unit 51 performs a process to calculate the steering angle θs by multiplying the obtained integrated angle by a conversion coefficient based on the rotation speed ratio of the steering reduction mechanism 14. The steering angle θs is output to the reaction force control amount calculation unit 52 and the steering control unit 60.

[0027] The reaction force control amount calculation unit 52 receives the steering torque Th, vehicle speed value V, steering angle θs, and steering-side actual current value Ib. Based on the steering torque Th, vehicle speed value V, steering angle θs, and steering-side actual current value Ib, the reaction force control amount calculation unit 52 performs a process to calculate the target reaction force torque command value Ts*, which is the target motor control amount for the steering reaction force. When calculating the target reaction force torque command value Ts*, the reaction force control amount calculation unit 52 further performs a process that refers to the drive mode DM, the driving assistance request FLG, and the code signal Sm.

[0028] More specifically, the reaction force control amount calculation unit 52 includes an axial force calculation unit 55, a target steering force calculation unit 56, and an axial force reflection unit 57. The axial force calculation unit 55 receives the vehicle speed value V and the steering side actual current value Ib. Based on the vehicle speed value V and the steering side actual current value Ib, the axial force calculation unit 55 performs a process to calculate the axial force component F. The axial force component F is the axial force applied to the steering shaft 22. The axial force component F is output to the axial force reflection unit 57.

[0029] The target steering force calculation unit 56 receives the steering torque Th, the vehicle speed value V, and the steering angle θs. Based on the steering torque Th, the vehicle speed value V, and the steering angle θs, the target steering force calculation unit 56 performs a process to calculate the steering force component Tb*. The steering force component Tb* acts in the same direction as the driver's steering direction. The target steering force calculation unit 56 performs a process to calculate a steering force component Tb* with a larger absolute value the larger the absolute value of the steering torque Th and the slower the vehicle speed value V. When calculating the target reaction force command value Ts*, the target steering force calculation unit 56 further performs a process that refers to the drive mode DM, the driving support request FLG, and the code signal Sm. The steering force component Tb* is output to the axial force reflection unit 57. In this embodiment, the process performed by the target steering force calculation unit 56 is an example of motor control amount calculation processing.

[0030] The axial force reflection unit 57 receives the axial force component F and the steering force component Tb*. The axial force reflection unit 57 performs a process to calculate the target reaction force torque command value Ts* by subtracting the axial force component F from the steering force component Tb*. The target reaction force torque command value Ts* is output to the energization control unit 53.

[0031] The power supply control unit 53 receives the target reaction force torque command value Ts*, the rotation angle θa, and the steering side actual current value Ia. Based on the target reaction force torque command value Ts*, the power supply control unit 53 calculates the current command value Ia* for the steering motor 13. The power supply control unit 53 then determines the difference between the current command value Ia* and the current value on the dq coordinate obtained by converting the steering side actual current value Ia based on the rotation angle θa, and controls the power supply to the steering motor 13 to eliminate this difference. As a result, the steering motor 13 generates torque corresponding to the target reaction force torque command value Ts*. In other words, it is possible to provide the driver with an appropriate responsiveness corresponding to the road surface reaction force.

[0032] As shown in Figure 2, the steering control unit 60 receives the drive mode DM, driver assistance request FLG, vehicle speed value V, rotation angle θb, and steering angle θs. Based on the drive mode DM, driver assistance request FLG, vehicle speed value V, rotation angle θb, and steering angle θs, the steering control unit 60 performs a process to control the power supply to the steering motor 32.

[0033] More specifically, the steering control unit 60 includes a pinion angle calculation unit 61, a target angle calculation unit 62, a pinion angle feedback control unit (referred to as "pinion angle F / B control unit" in the figure) 63, an energization control unit 64, and a code signal generation unit 66. The pinion angle calculation unit 61 receives the rotation angle θb. The pinion angle calculation unit 61 performs a process to convert the rotation angle θb into an integrated angle that includes a range exceeding 360° by, for example, counting the number of rotations of the steering motor 32 from the rack neutral position, which is the position of the steering shaft 22 when the vehicle is moving straight. The pinion angle calculation unit 61 multiplies the obtained integrated angle by a conversion coefficient 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. As a result, the pinion angle calculation unit 61 performs a process to calculate the pinion angle θp, which is the actual rotation angle of the pinion shaft 21. The pinion angle θp is output to the pinion angle feedback control unit 63.

[0034] The target angle calculation unit 62 receives the vehicle speed value V and the steering angle θs. Based on the vehicle speed value V and the steering angle θs, the target angle calculation unit 62 performs a process to calculate the target pinion angle θp*, which is the target motor control amount for the pinion angle θp. When calculating the target pinion angle θp*, the target angle calculation unit 62 further performs a process to refer to the drive mode DM and the driving assistance request FLG. For example, the target angle calculation unit 62 performs a process to calculate the target pinion angle θp* so as to reflect the characteristics according to the type of drive mode DM. Also, for example, the target angle calculation unit 62 performs a process to calculate the target pinion angle θp* so as to reflect the control method indicated by the driving assistance request FLG. The target pinion angle θp* is output to the pinion angle feedback control unit 63.

[0035] The pinion angle feedback control unit 63 receives the target pinion angle θp* and the pinion angle θp. The pinion angle feedback control unit 63 performs a process to calculate the steering force command value Tp*, which is the target control amount of steering force, through feedback control of the pinion angle θp in order to make the pinion angle θp follow the target pinion angle θp*. The steering force command value Tp* is output to the energization control unit 64.

[0036] The power supply control unit 64 receives the steering force command value Tp*, the rotation angle θb, and the steering-side actual current value Ib. The power supply control unit 64 calculates the current command value Ib* for the steering motor 32 based on the steering force command value Tp*. The power supply control unit 64 then calculates the difference between the current command value Ib* and the current value on the dq coordinate obtained by converting the steering-side actual current value Ib detected through the steering-side current sensor 65 based on the rotation angle θb, and controls the power supply to the steering motor 32 to eliminate this difference. As a result, the steering motor 32 rotates by an angle corresponding to the steering force command value Tp*.

[0037] The code signal generation unit 66 includes a process for determining whether the steering motor 32 is in an overheating state by referring to, for example, the detection result of a temperature sensor. The code signal generation unit 66 includes a process for determining whether the steering motor 32 is in an overheating state by comparing the temperature detected by the temperature sensor with a plurality of temperature thresholds. The temperature sensor detects, for example, the temperature of the motor coil or inverter of the steering motor 32. The overheating state of the steering motor 32 indicates that the operation of the steering motor 32 will be restricted in the case of overheating.

[0038] Furthermore, the code signal generation unit 66 performs processing to determine the voltage state of the DC power supply by referring to the detection results of, for example, a voltage sensor. The code signal generation unit 66 performs processing to determine the voltage state of the DC power supply by comparing the voltage detected by the voltage sensor with a plurality of voltage thresholds. The voltage sensor detects the voltage of a DC power supply such as a battery. The voltage state of the DC power supply indicates that the operation of the steering motor 32 is restricted if the voltage is low.

[0039] The code signal generation unit 66 includes a process for generating a code signal Sm by referring, for example, to the heat generation state of the steering motor 32 and the voltage state of the DC power supply. The code signal generation unit 66 codes the state of the steering device 2 according to the code table stored in the memory unit of the steering side control unit 60. Coding refers to the process of representing the state of the steering device 2 with a code. The state of the steering device 2 includes the heat generation state of the steering motor 32 and the voltage state of the DC power supply. If the steering device 2 is in an overheated state or a low voltage state, the code signal generation unit 66 executes a process to generate a code signal Sm indicating the state of the steering device 2 in which it is necessary to restrict the operation of the steering motor 32. The code signal generation unit 66 also includes a process to generate a code signal Sm indicating the state of the steering device 2 in which it is not necessary to restrict the operation of the steering motor 32 if the steering device 2 is neither in an overheated state nor a low voltage state. The code signal Sm is output to the steering side control unit 50.

[0040] The steering control unit 60 executes a process to restrict the operation of the steering motor 32 if the steering device 2 is in an overheating state or a voltage drop state. More specifically, when the steering control unit 60 restricts the operation of the steering motor 32, it executes a process to set a protection mode that restricts the power supply to the steering motor 32. On the other hand, when the steering control unit 60 does not restrict the operation of the steering motor 32, it executes a process to set a normal mode that does not restrict the power supply to the steering motor 32.

[0041] <About the Target Steering Force Calculation Unit> As shown in Figure 3, the target steering force calculation unit 56 includes a phase lag compensation amount calculation unit 71, a basic control amount calculation unit 72, a compensation amount calculation unit 73, a stabilization compensation amount calculation unit 74, a differentiator 75, a control amount reflection unit 76, a calculation mode determination unit 77, and a stabilization constant determination unit 78.

[0042] The phase lag compensation calculation unit 71 receives the steering torque Th. Based on the steering torque Th, the phase lag compensation calculation unit 71 performs a process to calculate the compensated steering torque Thf. The compensated steering torque Thf is obtained by applying phase compensation to the steering torque Th in order to adjust the frequency characteristics of the phase difference between the upper and lower parts of the torsion bar 41a with respect to the steering torque Th. If the phase difference that occurs between the upper and lower parts of the torsion bar 41a becomes large in accordance with the twisting of the torsion bar 41a, vibration may occur in the steering device 2. The compensated steering torque Thf compensates the phase difference so that such vibration is suppressed. The compensated steering torque Thf delays the phase of the steering torque Th. When calculating the compensated steering torque Thf, the phase lag compensation calculation unit 71 performs a process that further refers to the typeset Sta described later. The phase lag compensation calculation unit 71 performs filtering by, for example, a low-pass filter. In this case, the phase lag compensation calculation unit 71 performs filtering using filter characteristics such as the corresponding cutoff frequency to reflect the characteristics corresponding to the type set Sta. The compensated steering torque Thf is output to the basic control amount calculation unit 72.

[0043] The basic control quantity calculation unit 72 receives the compensated steering torque Thf and the vehicle speed value V. The basic control quantity calculation unit 72 executes a process of calculating a basic control quantity I1* based on the compensated steering torque Thf and the vehicle speed value V. The basic control quantity I1* is a control quantity calculated in relation to the steering of the steering wheel 3. The basic control quantity I1* is a basic component of the steering force component Tb*, and is set so that the steering of the steering wheel 3 exhibits desired characteristics. When calculating the basic control quantity I1*, the basic control quantity calculation unit 72 further executes a process of referring to a map set Smap described later. The basic control quantity calculation unit 72 executes a process of performing map calculation on the basic control quantity I1* using, for example, map data that defines the relationship among the compensated steering torque Thf, the vehicle speed value V, and the basic control quantity I1*. In this case, the basic control quantity calculation unit 72 performs map calculation using the corresponding map data so as to reflect the characteristics corresponding to the classification indicated by the map set Smap. Also, the basic control quantity calculation unit 72 uses the corresponding control constant so as to reflect the characteristics corresponding to the classification indicated by the map set Smap. The basic control quantity I1* is output to the control quantity reflection unit 76.

[0044] Note that map data is set data of a pair of discrete values of input variables and output values that are output variables corresponding to each of the input values that are input variables. That is, the map data defines an input-output relationship that is the relationship of the output value with respect to the input value related to the steering force component Tb*, that is, the target reaction torque command value Ts*. The map calculation may be a process in which when the input value matches any of the input values of the map data, the output value of the corresponding map data is used as the calculation result. Also, the map calculation may be a process in which when the input value does not match any of the input values of the map data, a value obtained by interpolation of a plurality of output values included in the map data is used as the calculation result. Alternatively, the map calculation may be a process in which when the input value does not match any of the input values of the map data, the output value of the map data corresponding to the closest value among the plurality of output values included in the map data is used as the calculation result.

[0045] The compensation amount calculation unit 73 receives the vehicle speed value V and the steering angle θs. Based on the vehicle speed value V and the steering angle θs, the compensation amount calculation unit 73 performs a process to calculate various compensation amounts Ic*. The various compensation amounts Ic* compensate the operation of the steering wheel 3 so that the operation of the steering wheel 3 realized based on the basic control amount I1* exhibits the desired characteristics. When calculating the various compensation amounts Ic*, the compensation amount calculation unit 73 further performs a process that refers to the map set Smap described later.

[0046] Various compensation amounts Ic* include, for example, at least one of return compensation, hysteresis compensation, damping compensation, and inertia compensation. The return compensation is a component that compensates for any excess or deficiency of the self-aligning torque of the steering wheel 5, and generates a torque directed in the direction of returning the steering wheel 3 to the steering neutral position. The return compensation is a component based on the rate of change of the steering angle θs. The hysteresis compensation is a component that compensates to optimize the hysteresis characteristics due to the mechanical friction component, and generates hysteresis characteristics in response to changes in the steering angle θs. The hysteresis compensation is a component based on the steering angle θs. The damping compensation is a component that reduces the minute vibrations occurring in the steering wheel 3, and generates a torque in the opposite direction to the steering direction at that time. The damping compensation is a component based on the rate of change of the steering angle θs. The inertia compensation is a component that suppresses the feeling of sticking at the beginning of steering and the feeling of flowing at the end of steering of the steering wheel 3. The inertia compensation amount generates a torque in the direction of the change in acceleration when the absolute value of the acceleration of the change in steering angle θs increases, such as when steering the steering wheel 3 begins. The inertia compensation amount is a component based on the change in acceleration of the steering angle θs.

[0047] For example, the compensation amount calculation unit 73 uses map data that defines the relationship between the rate of change of the steering angle θs, the vehicle speed value V, and the return compensation amount to perform a map calculation of the return compensation amount. In this case, the compensation amount calculation unit 73 performs a map calculation using the corresponding map data so as to reflect the characteristics according to the classification shown by the map set Smap. The compensation amount calculation unit 73 also uses the corresponding control constants so as to reflect the characteristics according to the classification shown by the map set Smap. This is also the case when the compensation amount calculation unit 73 performs a process to calculate the hysteresis compensation amount, the damping compensation amount, and the inertia compensation amount.

[0048] Various compensation amounts Ic* are output to the control amount reflecting unit 76. The stabilization compensation amount calculation unit 74 receives the vehicle speed value V and the torque derivative value dTh. The torque derivative value dTh is obtained through a differentiator 75 that performs a differential operation on the steering torque Th. The stabilization compensation amount calculation unit 74 executes a process of calculating a stabilization compensation amount Ita* based on the vehicle speed value V and the torque derivative value dTh. The stabilization compensation amount Ita* performs phase compensation to advance the phase of the steering force component Tb* related to the motor torque, that is, the target reaction torque command value Ts*, in order to adjust the response delay of the operation of the steering wheel 3 with respect to the change in the steering torque Th. When calculating the stabilization compensation amount Ita*, the stabilization compensation amount calculation unit 74 executes a process of further referring to the type set Sta described later. The stabilization compensation amount calculation unit 74 executes, for example, a process of performing a map calculation of a gain using map data that defines the relationship between the vehicle speed value V and the gain. Also, the stabilization compensation amount calculation unit 74 executes, for example, a process of performing a map calculation of a basic compensation amount using map data that defines the relationship between the torque derivative value dTh and the basic compensation amount. Also, the stabilization compensation amount calculation unit 74 executes a process of calculating the stabilization compensation amount Ita* by multiplying, for example, the gain and the basic compensation amount. In this case, the stabilization compensation amount calculation unit 74 executes a map calculation using corresponding map data so as to reflect the characteristics according to the type of the type set Sta. Also, the stabilization compensation amount calculation unit 74 uses corresponding control constants so as to reflect the characteristics according to the type of the type set Sta. The stabilization compensation amount Ita* is output to the control amount reflecting unit 76. In the present embodiment, the process executed by the stabilization compensation amount calculation unit 74 is an example of a stabilization compensation amount calculation process.

[0049] The control amount reflecting unit 76 receives the basic control amount I1*, various compensation amounts Ic*, and the stabilization compensation amount Ita*. The control amount reflecting unit 76 is an adder-subtractor that executes a process of calculating the steering force component Tb* by adding and subtracting the basic control amount I1*, the various compensation amounts Ic*, and the stabilization compensation amount Ita*. The control amount reflecting unit 76 executes a process of calculating the steering force component Tb* by adding various compensation amounts other than the damping compensation amount and subtracting only the damping compensation amount among the various compensation amounts Ic*.

[0050] The calculation mode determination unit 77 receives the drive mode DM, the driving assistance request FLG, and the code signal Sm. Based on the drive mode DM, the driving assistance request FLG, and the code signal Sm, the calculation mode determination unit 77 executes a process to switch the setting state of the map data classification, which is the calculation mode.

[0051] More specifically, as shown in Figure 4, when the calculation mode determination unit 77 receives the drive mode DM, which is the normal mode FM, it determines that the vehicle state is classified as "normal". In this case, the calculation mode determination unit 77 executes a process to generate a map set Smap indicating that it will switch to a calculation mode classified as "Map A". The basic control amount calculation unit 72 and the compensation amount calculation unit 73, having received this map set Smap, perform calculations using the map data and control constants corresponding to "Map A". In this embodiment, the vehicle state classified as "normal" is an example of a second vehicle state. Also, the calculation mode classified as "Map A" is an example of a first calculation mode.

[0052] Furthermore, when the calculation mode determination unit 77 receives a drive mode DM which is sport mode PM, it determines that the vehicle state is classified as "normal," just as when it receives a drive mode DM which is normal mode FM. In this case, the calculation mode determination unit 77 executes a process to generate a map set Smap indicating that it will switch to a calculation mode classified as "map B." The basic control amount calculation unit 72 and the compensation amount calculation unit 73, having received this map set Smap, perform calculations using the map data and control constants corresponding to "map B." In this embodiment, the calculation mode classified as "map B" is an example of a second calculation mode.

[0053] Furthermore, when the calculation mode determination unit 77 receives a drive mode DM indicating the first extended mode EM1, it determines that the vehicle state is classified as "extended 1," which is the first extended state. In this case, the calculation mode determination unit 77 executes a process to generate a map set Smap indicating that it will switch to a calculation mode classified as "map C." The basic control amount calculation unit 72 and the compensation amount calculation unit 73, having received this map set Smap, perform calculations using the map data and control constants corresponding to "map C." In this embodiment, the vehicle state classified as "extended 1" is an example of a fourth vehicle state. Also, the calculation mode classified as "map C" is an example of a third calculation mode.

[0054] Furthermore, when the calculation mode determination unit 77 receives a drive mode DM indicating a second extended mode EM2, it determines that the vehicle state is classified as "extended 2," which is a second extended state. In this case, the calculation mode determination unit 77 executes a process to generate a map set Smap indicating a switch to a calculation mode classified as "map D." The basic control amount calculation unit 72 and the compensation amount calculation unit 73, having received this map set Smap, perform calculations using the map data and control constants corresponding to "map D." In this embodiment, the vehicle state classified as "extended 2" is an example of a fourth vehicle state.

[0055] Furthermore, when the calculation mode determination unit 77 receives a driving assistance request FLG, it determines that the vehicle state is classified as a "driving assistance" state. In this case, the calculation mode determination unit 77 executes a process to generate the same map set Smap as the current one in order to maintain the current calculation mode. In this embodiment, a vehicle state classified as "driving assistance" is an example of a third vehicle state. Also, a calculation mode classified as "Map D" is an example of a third calculation mode.

[0056] Furthermore, when the calculation mode determination unit 77 receives a code signal Sm indicating an overheating state or a voltage drop state, it determines that the vehicle state is classified as an abnormal state, or "abnormal". In this case, the calculation mode determination unit 77 executes a process to generate a map set Smap indicating that it will switch to a calculation mode classified as "map A". In this embodiment, a vehicle state classified as "abnormal" is an example of a first vehicle state.

[0057] The map set Smap is output to the basic control variable calculation unit 72, the compensation variable calculation unit 73, and the stabilization constant determination unit 78. In this embodiment, the processing performed by the calculation mode determination unit 77 is an example of control mode determination processing.

[0058] The stabilization constant determination unit 78 receives a driver assistance request FLG, a code signal Sm, and a map set Smap. Based on the driver assistance request FLG, the code signal Sm, and the map set Smap, the stabilization constant determination unit 78 performs a process to switch the setting state of the type of stabilization constant. When switching the setting state of the type of stabilization constant, the stabilization constant determination unit 78 considers the control mode defined by the association between the vehicle state and the calculation mode. The contents indicated by the driver assistance request FLG, the code signal Sm, and the map set Smap identify a single control mode through their combination.

[0059] More specifically, as shown in Figure 4, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are in a vehicle state classified as "normal" and the calculation mode is "Map A", the control mode is classified as "second". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 1". The stabilization compensation amount calculation unit 74, upon receiving this type set Sta, performs a calculation using a stabilization constant determined from the map data and control constants corresponding to "type 1". In this embodiment, the stabilization constant classified as "type 1" is an example of a third stabilization constant. Also, the control mode classified as "second" is an example of a second control mode.

[0060] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are in a vehicle state classified as "normal" and the calculation mode classified as "map B", the control mode is classified as "third". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 1", similar to the case of the "second" control mode. In this embodiment, the control mode classified as "third" is an example of a third control mode.

[0061] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap indicate a vehicle condition classified as "abnormal," the control mode is classified as "first." When the control mode is classified as "first," the calculation mode is classified as "map A." In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 2." The stabilization compensation amount calculation unit 74, upon receiving this type set Sta, performs calculations using the stabilization constant determined from the map data and control constants corresponding to "type 2." In this embodiment, the stabilization constant classified as "type 2" is an example of a second stabilization constant. Also, the control mode classified as "first" is an example of a first control mode.

[0062] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are a vehicle state classified as "driver assistance" and a calculation mode classified as "map A", the control mode is classified as "fourth". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 3". The stabilization compensation amount calculation unit 74, upon receiving this type set Sta, performs a calculation using a stabilization constant determined from the map data and control constants corresponding to "type 3". In this embodiment, the stabilization constant classified as "type 3" is an example of the first stabilization constant. Also, the control mode classified as "fourth" is an example of the fourth control mode.

[0063] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are a vehicle state classified as "driver assistance" and a calculation mode classified as "map B", the control mode is classified as "fifth". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 3", similar to the case of the "fourth" control mode. In this embodiment, the control mode classified as "fifth" is an example of a fifth control mode.

[0064] Furthermore, if the contents indicated by the driving assistance request FLG, code signal Sm, and map set Smap are a vehicle state classified as "driving assistance" and a calculation mode classified as "map C", the control mode is classified as "6-1". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 3", similar to the case of the "4th" control mode. In this embodiment, the control mode classified as "6-1" is an example of the sixth control mode.

[0065] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are a vehicle state classified as "driver assistance" and a calculation mode classified as "map D", the control mode is classified as "6-2". In this case, the stabilization constant determination unit 78 executes a process to generate a type set Sta indicating a switch to a stabilization constant classified as "type 3", similar to the case of the "4th" control mode. In this embodiment, the control mode classified as "6-2" is an example of the sixth control mode.

[0066] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are vehicle conditions classified as "extension 1", the control mode is classified as "7-1". When the control mode is classified as "7-1", the calculation mode is classified as "map C". In this case, the stabilization constant determination unit 78 includes the process of generating a type set Sta indicating a switch to a stabilization constant classified as "type 4". The stabilization compensation amount calculation unit 74, upon receiving this type set Sta, performs calculations using the stabilization constant determined from the map data and control constants corresponding to "type 4". In this embodiment, the stabilization constant classified as "type 4" is an example of a fourth stabilization constant. Also, the control mode classified as "7-1" is an example of a seventh control mode.

[0067] Furthermore, if the contents indicated by the driver assistance request FLG, code signal Sm, and map set Smap are vehicle conditions classified as "extension 2", the control mode is classified as "7-2". When the control mode is classified as "7-2", the calculation mode is classified as "map D". In this case, the stabilization constant determination unit 78 includes the process of generating a type set Sta indicating a switch to a stabilization constant classified as "type 5". The stabilization compensation amount calculation unit 74, upon receiving this type set Sta, performs calculations using the stabilization constant determined from the map data and control constants corresponding to "type 5". In this embodiment, the stabilization constant classified as "type 5" is an example of the fourth stabilization constant. Also, the control mode classified as "7-2" is an example of the seventh control mode.

[0068] The typeset Sta is output to the phase delay compensation amount calculation unit 71 and the stabilization compensation amount calculation unit 74. In this embodiment, the processing performed by the stabilization constant determination unit 78 is an example of stabilization constant determination processing.

[0069] As a result, when the vehicle state is classified as "normal," the target steering force calculation unit 56 uses the same "Type 1" stabilization constant in the control modes classified as "Second" and "Third," regardless of which calculation mode is selected. For example, a vehicle state classified as "normal" is a state within which the driver can easily control the vehicle's behavior without requiring special skills. The calculation modes classified as "Map A" or "Map B" are states that realize a steering feel that allows the driver to comfortably steer the steering device 2 in a vehicle state classified as "normal." The calculation mode classified as "Map B" realizes a steering feel that allows the driver to directly steer the steering device 2, compared to the calculation mode classified as "Map A." In other words, the control modes classified as "Second" and "Third" are states that realize the behavior of the steering device 2, i.e., the steering feel, within a range where the driver can easily control the vehicle's behavior without requiring special skills. In contrast, the stabilization constant classified as "Type 1" is set to a range of values ​​experimentally determined through simulations, etc., that ensures control stability in the behavior of the steering system 2 within a range where the driver can easily control the vehicle's behavior without requiring special skills.

[0070] Furthermore, when the vehicle condition is classified as "abnormal," the target steering force calculation unit 56 uses a stabilization constant classified as "Type 2," as the calculation mode is classified as "Map A" and the control mode is classified as "First." For example, a vehicle condition classified as "abnormal" is a condition in which the vehicle cannot perform its normal driving function. The calculation mode of "Map A" is a state in which, in a vehicle condition classified as "abnormal," a steering feel is achieved that allows the driver to easily steer the steering device 2. In other words, the control mode classified as "First" is a state that realizes the behavior of the steering device 2, i.e., the steering feel, when the vehicle is unable to perform its normal driving function. In contrast, the stabilization constant classified as "Type 2" is set to a value within a range experimentally determined by simulation, etc., that ensures control stability in the behavior of the steering device 2 when the vehicle is unable to perform its normal driving function.

[0071] Furthermore, when the vehicle state is classified as "driving assistance," the target steering force calculation unit 56 uses a stabilization constant classified as "Type 3," regardless of the calculation mode, i.e., the control mode. For example, a vehicle state classified as "driving assistance" is a state in which the steering of the steering wheels 5 is controlled regardless of whether the driver steers the steering device 2. In other words, the control modes classified as "Type 4," "Type 5," "Type 6-1," and "Type 6-2" are states that realize the behavior of the steering device 2, i.e., the steering feel, when the steering of the steering wheels 5 is controlled regardless of whether the driver steers the steering device 2. In contrast, the stabilization constant classified as "Type 3" is set to a range of values ​​experimentally determined by simulation, etc., that can ensure control stability in the behavior of the steering device 2 when the steering of the steering wheels 5 is controlled regardless of whether the driver steers the steering device 2.

[0072] Furthermore, when the vehicle state is classified as "Extended 1", the target steering force calculation unit 56 uses a dedicated stabilization constant classified as "Type 4" in a calculation mode classified as "Map C" and a control mode classified as "7-1". For example, the vehicle state classified as "Extended 1" is a state in which the output of the engine, etc., is optimized to increase responsiveness to the driver's demands regardless of fuel consumption. In other words, the control mode classified as "7-1" is a state that realizes the behavior of the steering device 2, i.e., the steering feel, in a state in which the output of the engine, etc., is optimized to increase responsiveness to the driver's demands regardless of fuel consumption. In contrast, the stabilization constant classified as "Type 4" is set to a value within a range experimentally determined by simulation, etc., that can ensure control stability in the behavior of the steering device 2 in a state in which the output of the engine, etc., is optimized to increase responsiveness to the driver's demands regardless of fuel consumption.

[0073] Furthermore, when the vehicle state is classified as "Extended 2", the target steering force calculation unit 56 uses a dedicated stabilization constant classified as "Type 5" in a calculation mode classified as "Map D" and a control mode classified as "7-2". For example, the vehicle state classified as "Extended 2" is a state in which the output of the engine, etc., is optimized to enhance passenger comfort. In other words, the control mode classified as "7-2" is a state that realizes the behavior of the steering device 2, i.e., the steering feel, in a state in which the output of the engine, etc., is optimized to enhance passenger comfort. In contrast, the stabilization constant classified as "Type 5" is set to a value within a range experimentally determined by simulation, etc., that can ensure control stability in the behavior of the steering device 2 in a state in which the output of the engine, etc., is optimized to enhance passenger comfort.

[0074] <Process to switch the setting state of the type of stabilization constant> As shown in Figure 5, the stabilization constant determination unit 78, without receiving the drive mode DM, executes a process to switch the setting state of the type of stabilization constant based on the driving assistance request FLG, the code signal Sm, and the map set Smap.

[0075] In the process of switching the setting state of the type of stabilization constant, the stabilization constant determination unit 78 determines whether or not the vehicle state is classified as "driving assistance" (step 100). The process in step 100 includes the process of determining whether or not a driving assistance request FLG has been received.

[0076] Next, if the stabilization constant determination unit 78 determines that the vehicle state is classified as "driving assistance" (step 100: YES), it generates a typeset Sta indicating that it will switch to a stabilization constant classified as "type 3" (step 102). In other words, if the vehicle state is classified as "driving assistance," the stabilization constant determination unit 78 decides to switch to a stabilization constant classified as "type 3," regardless of the classification of the calculation mode, i.e., the control mode. After that, the stabilization constant determination unit 78 completes the series of processes.

[0077] On the other hand, if the stabilization constant determination unit 78 determines that the vehicle state is not classified as "driving assistance" (step 100: NO), it determines whether the vehicle state is classified as "abnormal" (step 104). The process in step 104 includes determining whether the steering device 2 has received a code signal Sm indicating that there is no need to restrict the operation of the steering motor 32.

[0078] Next, if the stabilization constant determination unit 78 determines that the vehicle state is classified as "abnormal" (step 104: YES), it generates a typeset Sta indicating that it will switch to a stabilization constant classified as "Type 2" (step 106). In other words, if the vehicle state is classified as "abnormal," the stabilization constant determination unit 78 determines that the calculation mode is classified as "Map A," and therefore it will switch to a stabilization constant classified as "Type 2." In this case, the control mode is classified as "First." After that, the stabilization constant determination unit 78 completes the series of processes.

[0079] On the other hand, if the stabilization constant determination unit 78 determines that the calculation mode is not classified as "abnormal" (step 104: NO), it determines whether the calculation mode is classified as "map A" or "map B" (step 108). The process in step 108 includes determining whether or not it has received a map set Smap indicating that the calculation mode is classified as "map A".

[0080] Next, the stabilization constant determination unit 78 determines that the calculation mode is classified as "Map A" or "Map B" (Step 108: YES), and generates a typeset Sta indicating that it will switch to a stabilization constant classified as "Type 1" (Step 110). In other words, the stabilization constant determination unit 78 determines that if the calculation mode is classified as "Map A" or "Map B", the vehicle state is classified as "Normal", and therefore it will switch to a stabilization constant classified as "Type 1". In this case, the control mode is classified as "Second" or "Third". After that, the stabilization constant determination unit 78 completes the series of processes.

[0081] On the other hand, if the stabilization constant determination unit 78 determines that the calculation mode is not classified as "Map A" or "Map B" (step 108: NO), it determines whether the calculation mode is classified as "Map C" (step 112). The process in step 112 includes determining whether it has received a map set Smap indicating that the calculation mode is classified as "Map C".

[0082] Next, if the stabilization constant determination unit 78 determines that the calculation mode is classified as "Map C" (Step 112: YES), it generates a typeset Sta indicating that it will switch to a stabilization constant classified as "Type 4" (Step 114). In other words, if the calculation mode is classified as "Map C", the stabilization constant determination unit 78 determines that the vehicle state is classified as "Extended 1", and therefore decides to switch to a stabilization constant classified as "Type 4". In this case, the control mode is classified as "7-1". After that, the stabilization constant determination unit 78 completes the series of processes.

[0083] On the other hand, if the stabilization constant determination unit 78 determines that the calculation mode is not in a state classified as "Map C" (step 112: NO), it generates a typeset Sta indicating that it will switch to a stabilization constant classified as "Type 5" (step 116). In step 116, the stabilization constant determination unit 78 determines that it has received a mapset Smap indicating that the calculation mode is in a state classified as "Map D". In other words, if the stabilization constant determination unit 78 determines that the calculation mode is in a state classified as "Map D", it determines that the vehicle state is in a state classified as "Extended 2", and therefore decides to switch to a stabilization constant classified as "Type 5". In this case, the control mode is in a state classified as "7-2". After that, the stabilization constant determination unit 78 completes the series of processes.

[0084] <Operation of this embodiment> For example, if there is only one type of stabilization constant, the stabilization constant will be shared regardless of the combination of vehicle state and calculation mode, i.e., the classification of the control mode. As a result, the range of adjustment for control stability in the vehicle state and calculation mode is limited, and depending on the combination of vehicle state and calculation mode, responsiveness may have to be sacrificed.

[0085] In contrast, as shown in Figure 4, for example, the types of stabilization constants include five types, each with different characteristics. In the steering control unit 50, the target steering force calculation unit 56 includes a stabilization constant determination unit 78 that determines the type of stabilization constant so associates the combination of vehicle state and calculation mode, i.e., the type of control mode, with the stabilization constant. This makes it possible to ensure control stability specific to the combination of vehicle state and calculation mode.

[0086] <Effects of this embodiment> (1-1) Since it becomes possible to ensure control stability specific to the combination of vehicle state and calculation mode, the range of adjustment for control stability for each combination of vehicle state and calculation mode can be broadened. In other words, it is possible to suppress the sacrifice of responsiveness for each combination of vehicle state and calculation mode. Therefore, the behavior realized by the steering device 2, that is, the driver's feel of steering the vehicle can be enhanced.

[0087] (1-2) The vehicle state includes vehicle states classified as "abnormal" and vehicle states classified as "normal," which relate to the behavior of different vehicles. The control mode includes a control mode classified as "first" to which a vehicle state classified as "abnormal" is associated with a specific calculation mode classified as "Map A," and a control mode classified as "second" to which a vehicle state classified as "normal" is associated. In response to this, the stabilization constant determination unit 78 performs a process to determine different stabilization constants for the control modes classified as "first" and "second," which have the same calculation mode but different vehicle states. Therefore, even if the calculation mode is the same, compensation that takes into account the different vehicle states can be realized. As a result, the steering force component Tb* related to motor torque, i.e., the target reaction force command value Ts*, can be appropriately compensated while having a specific calculation mode classified as "Map A" that is associated with different vehicle states.

[0088] (1-3) The calculation modes include calculation modes classified as "Map A" and calculation modes classified as "Map B" which define different input / output relationships. The control modes include a third type of control mode to which the calculation mode classified as "Map B" is associated with a vehicle state classified as "normal". In contrast, when the vehicle state is classified as "normal", the stabilization constant determination unit 78 performs the process of determining the same stabilization constant in the control modes classified as "second" and "third", regardless of which state the calculation mode is. Therefore, even if the calculation modes are different, compensation that emphasizes the same vehicle state can be realized. As a result, the steering force component Tb* related to motor torque, i.e., the target reaction force command value Ts*, can be appropriately compensated when the vehicle state is classified as "normal" and associated with different calculation modes.

[0089] (1-4) The vehicle state includes a vehicle state classified as "Driving Assistance" which is different from "Abnormal" and "Normal". The calculation mode includes a calculation mode classified as "Map C" or "Map D" which is different from "Map A" and "Map B". The control mode includes a control mode classified as "4" to which the calculation mode classified as "Map A" is associated with a vehicle state classified as "Driving Assistance", and a control mode classified as "5" to which the calculation mode classified as "Map B" is associated. The control mode also includes a control mode classified as "6-1" to which the calculation mode classified as "Map C" is associated with a vehicle state classified as "Driving Assistance". The control mode also includes a control mode classified as "6-2" to which the calculation mode classified as "Map D" is associated. In response to this, when the vehicle state is classified as "Driving Assistance", the stabilization constant determination unit 78 executes a process to determine the same stabilization constant in the control modes classified as "4", "5", "6-1", and "6-2", regardless of which state the calculation mode is. Therefore, even when four different calculation modes are included, compensation that prioritizes the same vehicle state can be achieved. This allows for appropriate compensation of the steering force component Tb* related to motor torque, i.e., the target reaction torque command value Ts*, while the vehicle state of "driving assistance" is associated with the four different calculation modes.

[0090] (1-5) The vehicle state includes vehicle states classified as "extension 1" or "extension 2" that are different from the vehicle states classified as "abnormal," "normal," and "driving assistance." The control mode includes a control mode classified as "7-1" to which a calculation mode classified as "map C" is associated with a vehicle state classified as "extension 1." The control mode also includes a control mode classified as "7-2" to which a calculation mode classified as "map D" is associated with a vehicle state classified as "extension 2." In response to this, the stabilization constant determination unit 78 executes a process to determine a stabilization constant classified as "type 4" corresponding to a control mode classified as "7-1" when the vehicle state is classified as "extension 1." The stabilization constant determination unit 78 also executes a process to determine a stabilization constant classified as "type 5" corresponding to a control mode classified as "7-2" when the vehicle state is classified as "extension 2." Therefore, even when control modes classified as "7-1" and "7-2" have a dedicated relationship in which the calculation mode and the vehicle state are linked one-to-one, compensation that emphasizes the existence of this dedicated relationship can be realized. As a result, the steering force component Tb* related to motor torque, i.e., the target reaction torque command value Ts*, can be appropriately compensated while the calculation mode and the vehicle state have a dedicated relationship.

[0091] <Other Embodiments> The above embodiments can be implemented with modifications as follows. The above embodiments and the following other embodiments can be combined with each other to the extent that they do not contradict each other technically.

[0092] The stabilization constant determination unit 78 may be configured to receive a drive mode DM instead of a map set Smap. In this case, the stabilization constant determination unit 78 can determine the control mode based on the drive mode DM, the driving assistance request FLG, and the code signal Sm, and perform a process to switch the setting state of the type of stabilization constant.

[0093] - The vehicle state does not have to include vehicle states classified as "extension 2". In other words, the calculation mode does not have to include calculation modes classified as "map D". In this case, the process of switching the setting state of the type of stabilization constant shown in Figure 5 can be eliminated by removing the process in step 116. The other embodiments described here can also be similarly applied when the vehicle state classified as "extension 1" is omitted instead of "extension 2".

[0094] - The vehicle state does not have to include the vehicle states classified as "extension 1" and "extension 2". In other words, the calculation mode does not have to include the calculation modes classified as "map C" and "map D". In this case, the process of switching the setting state of the type of stabilization constant shown in Figure 5 can be simplified by eliminating the processing from step 112 onwards.

[0095] - Vehicle states classified as "Extension 1" may be associated with two or more calculation modes. The same applies to vehicle states classified as "Extension 2". - Vehicle states classified as "Driving Assistance" do not necessarily have to be associated with at least one of the calculation modes classified as "Map C" and "Map D".

[0096] - Vehicle states classified as "driving assistance" may be associated with a dedicated calculation mode. - Vehicle states do not necessarily have to include vehicle states classified as "driving assistance". In this case, the process of switching the setting state of the type of stabilization constant shown in Figure 5 can be simplified by eliminating steps 100 and 102.

[0097] - The vehicle status should include at least two vehicle statuses classified as "normal" and "abnormal." In other words, the calculation mode should include at least two calculation modes classified as "Map A" and "Map B."

[0098] - A dedicated calculation mode may be associated with vehicle conditions classified as "abnormal". - The stabilization constant determination unit 78 may determine different stabilization constants in the calculation modes classified as "second" and "third". In this case, the vehicle conditions only need to include vehicle conditions classified as "normal".

[0099] The stabilization constant determination unit 78 may determine different stabilization constants in the calculation modes classified as "4th," "5th," "6-1," and "6-2." Alternatively, the stabilization constant determination unit 78 may determine the same stabilization constant in the calculation modes classified as "4th" and "5th."

[0100] The stabilization constant determination unit 78 may determine the same stabilization constant for vehicle conditions other than those classified as "abnormal." Furthermore, the stabilization constant determination unit 78 may determine the same stabilization constant for vehicle conditions other than those classified as "normal" and "abnormal."

[0101] - The stabilization constant determination unit 78 may determine the same stabilization constant for vehicle states classified as "extension 1" and "extension 2". - The target steering force calculation unit 56 only needs to include the basic control amount calculation unit 72. In other words, the compensation amount calculation unit 73 is not required.

[0102] The basic control variable calculation unit 72 only needs to receive state variables related to the steering wheel 3; for example, it does not need to receive the vehicle speed value V, and may also receive other parameters.

[0103] - The steering member used by the driver to steer the steering device 2 may be a joystick, for example, in addition to the steering wheel 3. - The steering control unit 50 may perform feedback control of the steering angle θs in order to make the steering angle θs follow the target steering angle, similar to the steering control unit 60.

[0104] - The steering control unit 50 may perform torque feedback control processing to make the compensated steering torque Thf follow the target steering torque calculated based on the steering torque Th. - The steering angle calculation unit 51 may calculate the steering angle θs by considering the torsion of the steering shaft 11 in accordance with the steering torque Th and adding or subtracting the torsion to the rotation angle θa.

[0105] - 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. - The steering motor 32 may be, for example, arranged coaxially with the steering shaft 22, or connected to the steering shaft 22 via a worm and wheel to a pinion shaft constituting a rack and pinion mechanism.

[0106] - The steering system 2 is designed with a linkless structure in which the steering unit 4 and the steering unit 6 are mechanically separated at all times. However, it is not limited to this, and a structure in which the steering unit 4 and the steering unit 6 can be mechanically separated by a clutch may also be used. Furthermore, the steering system 2 may have a structure in which the steering unit 6 can independently steer the left and right steering wheels 5.

[0107] - Although the steering system 2 is configured as a steer-by-wire type steering system, it may also be configured as an electric power steering type steering system. In an electric power steering type steering system, the steering wheel 3 and the steering wheels 5 shown in Figure 1 are mechanically connected. That is, the steering shaft 11, pinion shaft 21, and steering shaft 22 function as a power transmission path between the steering wheel 3 and the steering wheels 5. As the steering wheel 3 is turned, the steering shaft 22 reciprocates, changing the steering angle θi of the steering wheels 5. The electric power steering type steering system has an assist motor and an assist control device. The assist motor is provided in the same position as the steering motor 13 or steering motor 32 shown in Figure 1. The assist motor generates an assist force to assist the steering of the steering wheel 3. The assist force is a torque in the same direction as the steering direction of the steering wheel 3, and is a steering torque for turning the steering wheels 5. The assist control device corresponds to the steering control device 1. The assist control device controls the drive of the assist motor, which is the object of control.

Claims

1. A steering control device for controlling the behavior of a steering system of a vehicle through control of the drive of a motor having a steering system of the vehicle, wherein the steering control device includes a control unit configured to control the drive of the motor, and the control unit is configured to perform: a control mode determination process for determining a control mode for controlling the behavior of the steering system from among a plurality of control modes that realize different behaviors of the steering system; a motor control amount calculation process for calculating a motor control amount for controlling the drive of the motor so as to exhibit steering characteristics corresponding to the determined control mode; a stabilization constant determination process for determining a stabilization constant, which is a characteristic for ensuring control stability when controlling the drive of the motor, from among a plurality of stabilization constants having different characteristics; and a stabilization compensation amount calculation process for calculating a stabilization compensation amount corresponding to the determined stabilization constant for compensating the motor control amount, wherein the stabilization constant determination process includes a process for determining the stabilization constant associated with the control mode determined by the control mode determination process.

2. Each of the plurality of control modes is defined by associating one of a plurality of vehicle states relating to the behavior of the vehicle with one of a plurality of calculation modes defining the input-output relationship between input values ​​and output values ​​relating to the motor control amount, the plurality of vehicle states include a first vehicle state and a second vehicle state relating to the behavior of the vehicle which are different from each other, the plurality of control modes include a first control mode to which the first vehicle state is associated with a particular calculation mode among the plurality of calculation modes and a second control mode to which the second vehicle state is associated, and the stabilization constant determination process includes a process to determine the stabilization constant which is different for the first control mode and the second control mode in the particular calculation mode, according to claim 1.

3. The steering control device according to claim 2, wherein the plurality of calculation modes include a first calculation mode which is a specific calculation mode and a second calculation mode which defines an input / output relationship different from that of the first calculation mode, the plurality of control modes further include a third control mode to which the second calculation mode is associated with a second vehicle state, and the stabilization constant determination process includes a process to determine the same stabilization constant in the second control mode and the third control mode, regardless of whether the vehicle is in the second vehicle state or the first calculation mode and the second calculation mode.

4. The steering control device according to claim 3, wherein the plurality of vehicle states further includes a third vehicle state relating to the behavior of the vehicle which is different from the first vehicle state and the second vehicle state; the plurality of calculation modes further includes a third calculation mode that defines the input / output relationship which is different from the first calculation mode and the second calculation mode; the plurality of control modes further includes a fourth control mode to which the first calculation mode is associated with the third vehicle state, a fifth control mode to which the second calculation mode is associated, and a sixth control mode to which the third calculation mode is associated; and the stabilization constant determination process includes a process to determine the same stabilization constant in the fourth control mode, the fifth control mode and the sixth control mode, regardless of any of the first calculation mode, the second calculation mode and the third calculation mode, when the vehicle is in the third vehicle state.

5. The steering control device according to claim 4, wherein the plurality of vehicle states further includes a fourth vehicle state relating to the behavior of the vehicle which is different from the first vehicle state, the second vehicle state, and the third vehicle state; the plurality of control modes further includes a seventh control mode in which the third calculation mode is associated with the fourth vehicle state; and the stabilization constant determination process includes a process of determining a dedicated stabilization constant corresponding to the seventh control mode from among the plurality of stabilization constants when the vehicle is in the fourth vehicle state.

6. The steering control device according to claim 5, wherein the stabilization constant determination process includes: a process for determining a first stabilization constant when the vehicle is in the third vehicle state, regardless of whether the determined control mode is the fourth control mode, the fifth control mode, or the sixth control mode; a process for determining a second stabilization constant corresponding to the first control mode when the vehicle is in the first vehicle state; a process for determining a third stabilization constant when the vehicle is not in the first vehicle state and the first or second calculation mode is determined, regardless of whether the determined control mode is the second control mode or the third control mode; and a process for determining a fourth stabilization constant corresponding to the seventh control mode when the vehicle is not in the first vehicle state and the third calculation mode is determined.

7. A steering control method for controlling the behavior of a steering system of a vehicle through control of the drive of a motor having a steering system of the vehicle, comprising: executing a control mode determination process to determine a control mode for controlling the behavior of the steering system from among a plurality of control modes that realize different behaviors of the steering system; executing a motor control amount calculation process to calculate a motor control amount for controlling the drive of the motor so as to exhibit steering characteristics corresponding to the determined control mode; executing a stabilization constant determination process to determine a stabilization constant, which is a characteristic for ensuring control stability when controlling the drive of the motor, from among a plurality of stabilization constants having different characteristics; and executing a stabilization compensation amount calculation process to calculate a stabilization compensation amount corresponding to the determined stabilization constant for compensating the motor control amount, wherein the stabilization constant determination process includes a process for determining the stabilization constant associated with the control mode determined by the control mode determination process.

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