Vehicle control device and vehicle control program

Abstract

To provide a vehicle control device which prevents vehicle behavior during automatic travel from getting unstable.SOLUTION: A vehicle 90 to which a control device 10 is applied comprises a skid prevention function preventing the vehicle from skidding through individually adjusting forward and backward force acting on respective wheels. The control device 10 enables the vehicle 90 to perform automatic travel through controlling the vehicle 90 on the basis of a demand input from an operation support device 20. The control device 10 has a wheel demand generation section 13 which calculates individual wheel horizontal force demand values as demand values of horizontal force of respective wheels on the basis of the demand input from the operation support device 20. Given that a first horizontal force limit value is defined to be a limit value of the horizontal force applicable to rear wheels, the wheel demand generation section 13 limits a front wheel horizontal force demand value, which is the individual wheel horizontal force demand value for front wheels, to be equal to or less than the first horizontal force limit value when the skid prevention function is lost and behavior of the vehicle 90 is in an oversteer state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device and a vehicle control program for an automatically driven vehicle. [Background technology]

[0002] Driving assistance devices that automatically drive vehicles are known. Patent Document 1 discloses a control device that prevents the behavior of an automatically driven vehicle from continuing to be unstable. The control device disclosed in Patent Document 1 is configured to perform behavior stabilization control that aims to resolve the unstable state. Specifically, the behavior stabilization control generates a yaw moment in the vehicle by generating a braking force difference between the inner and outer wheels of a turn when the vehicle's behavior is in an oversteer or understeer state. Furthermore, a configuration is disclosed that reduces the vehicle speed if the vehicle's behavior remains unstable even after performing the behavior stabilization control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-157890 Summary of the Invention [Problem to be solved by the invention]

[0004] When a force in a direction that reduces the vehicle speed is applied to the wheels in order to reduce the vehicle speed, the friction circle theory suggests the following: Increasing the force in the direction that reduces the vehicle speed is accompanied by a decrease in the lateral force that can be applied to the wheels without causing the wheels to slip. Therefore, while the force in the direction that reduces the vehicle speed is being increased while the vehicle is turning, it may not be possible to generate a lateral force sufficient to stabilize the vehicle. In other words, while the force in the direction that reduces the vehicle speed is being increased, there is a problem in that it is difficult to resolve the unstable state of the vehicle's behavior. [Means for solving the problem]

[0005] A vehicle control device for solving the above problem is applied to a vehicle having a driving assistance device that assists the vehicle in traveling, a drive actuator and a braking actuator that generate longitudinal forces that indicate forces that act in the longitudinal direction of the vehicle, and a steering actuator that adjusts a tire angle that is the steering angle of a wheel of the vehicle, and the vehicle control device automatically travels by controlling the vehicle based on a request input from the driving assistance device, and includes a state quantity calculation unit that calculates state quantities including a yaw rate of the vehicle, a wheel request generation unit that calculates each wheel lateral force request value based on the request as a lateral force request value at the wheel, and a steering actuator that controls the steering actuator. and an instruction value generating unit that outputs an instruction value to be controlled based on the each wheel lateral force request value, wherein the vehicle is equipped with a skid suppression function that suppresses skid of the vehicle by separately adjusting the longitudinal force acting on each wheel, and when the state quantity indicates that the behavior of the vehicle is in an oversteer state due to a malfunction of the skid suppression function, the wheel request generating unit calculates a value while the vehicle is traveling as a limit value of the lateral force that can act on the rear wheels among the wheels, and limits the front wheel lateral force request value, which is the each wheel lateral force request value for the front wheels, to a magnitude equal to or less than the first lateral force limit value.

[0006] According to the above configuration, if the vehicle behavior is in an oversteer state when the skid suppression function has failed, the magnitude of the front wheel lateral force demand value is limited. The front wheel tire angle is controlled based on this front wheel lateral force demand value. The first lateral force limit value that limits the magnitude of the front wheel lateral force demand value is set to the limit value of the lateral force that can act on the rear wheels while traveling. Therefore, the lateral force acting on the front wheels of a vehicle in an oversteer state can be limited based on the rear wheels of the vehicle in an oversteer state. By adjusting the front wheel tire angle in accordance with this limited front wheel lateral force demand value, the difference between the lateral forces of the front wheels and the rear wheels of a vehicle turning can be reduced. This suppresses the oversteer state and stabilizes the vehicle behavior.

[0007] However, the skid stabilization function can generate a yaw moment in a direction that will eliminate the oversteer state. With the above configuration, even when it is not possible to expect that such a yaw moment will be applied to the vehicle in a direction that will eliminate the oversteer state, it is possible to suppress the oversteer state and stabilize the vehicle behavior.

[0008] A vehicle control program for solving the above problem is a vehicle that has a driving assistance device that assists vehicle driving, a drive actuator and a braking actuator that generate longitudinal forces that indicate forces that act in the longitudinal direction of the vehicle, and a steering actuator that adjusts a tire angle that is the steering angle of the wheels of the vehicle, and that has a skid suppression function that suppresses skid of the vehicle by separately adjusting the longitudinal forces that act on each wheel, and the vehicle control program automatically drives the vehicle by having a control device of the vehicle execute assistance control that controls the vehicle based on a request output from the driving assistance device, the vehicle control program comprising: a state quantity calculation process that calculates state quantities including a yaw rate of the vehicle; The present invention is configured to have the control device execute a wheel requirement generation process that calculates each wheel lateral force requirement value based on the requirement as a lateral force requirement value at the wheel, and a command value generation process that outputs a command value to control the steering actuator based on the each wheel lateral force requirement value, wherein in the wheel requirement generation process, when the state quantity indicates that the vehicle behavior is in an oversteer state due to a malfunction of the sideslip suppression function, a value calculated while the vehicle is traveling as a limit value of the lateral force that can act on a rear wheel among the wheels is set as a first lateral force limit value, and for front wheels among the wheels, the front wheel lateral force requirement value, which is the each wheel lateral force requirement value at the front wheel, is limited to a magnitude equal to or less than the first lateral force limit value.

[0009] By having the control device execute the vehicle control program, it is possible to suppress an oversteer state and stabilize the behavior of the vehicle, similar to the vehicle control device. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing an embodiment of a vehicle control device and a vehicle that is an object to be controlled by the vehicle control device. [Figure 2] FIG. 2 is a flowchart showing the flow of processing executed by the vehicle control device when performing assistance control for automatic driving of the vehicle. [Figure 3] FIG. 3 is a flowchart showing the flow of processing executed by the vehicle control device when generating a wheel request. [Figure 4] FIG. 4 is a diagram showing the relationship between the front tire angle and the yaw rate, which is used by the vehicle control device to determine the behavior of the vehicle. [Figure 5] FIG. 5 is a diagram illustrating threshold values ​​of vehicle longitudinal forces used by the vehicle control device to determine the behavior of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0011] A control device 10, which is one embodiment of a vehicle control device, will be described below with reference to FIGS. 1 shows a control device 10 and a vehicle 90 to which the control device 10 is applied. The vehicle 90 is equipped with a driving assistance device 20 that assists in driving the vehicle 90. The control device 10 can perform assistance control to automatically drive the vehicle 90 by controlling the vehicle 90 based on a request input from the driving assistance device 20. In this embodiment, the assistance control will be described as control to move the vehicle 90 forward.

[0012] <vehicle> The vehicle 90 is, for example, a four-wheel vehicle having two front wheels and two rear wheels.

[0013] As shown in FIG. 1, a vehicle 90 includes a drive system 30 that transmits drive force to wheels. The drive system 30 includes a drive actuator that generates drive force. For example, the vehicle 90 includes a motor generator as an example of a drive actuator. Drive force can be generated by making the motor generator function as an electric motor. The drive actuator may be an internal combustion engine. A motor generator and an internal combustion engine may also be used as the drive actuator. Another example of a drive actuator is an in-wheel motor.

[0014] For example, the drive system 30 is configured to be able to transmit driving force to all of the wheels. The drive system 30 may be configured to be able to transmit driving force to the front wheels among the wheels, or may be configured to be able to transmit driving force to the rear wheels among the wheels.

[0015] The vehicle 90 is equipped with a braking system 40 that applies braking force to the wheels. The braking system 40 is equipped with a braking actuator that generates the braking force. The braking actuator is configured by, for example, a friction braking device and a regenerative braking device.

[0016] An example of a friction braking device is a hydraulic braking device. The friction braking device is equipped with a braking mechanism corresponding to each wheel. The braking mechanism is composed of a rotating body that rotates integrally with the wheel, a friction material that can be pressed against the rotating body, and a wheel cylinder that presses the friction material against the rotating body in response to hydraulic pressure. One example of a braking mechanism is a disc brake. The braking mechanism may also be a drum brake. Another example of a friction braking device is an electric braking device that mechanically transmits the driving force of an electric motor to press a friction material against the rotating body.

[0017] An example of a regenerative braking device is the motor generator described above. By making the motor generator function as a generator, a regenerative braking force can be applied to the wheels. Another example of a regenerative braking device is an in-wheel motor.

[0018] Regenerative cooperative control is one of the controls that can be performed by the braking system 40. Regenerative cooperative control is a control that applies a desired braking force to the vehicle 90 by coordinating the regenerative braking force of the regenerative braking device and the friction braking force of the friction braking device.

[0019] The brake actuator provided in the brake system 40 is not limited to being configured by a friction brake device and a regenerative brake device. The brake actuator may be configured by only a friction brake device, or may be configured by only a regenerative brake device.

[0020] Vehicle 90 is equipped with a steering system 50 that can adjust the tire angle, which is the steering angle of the wheels. Steering system 50 is equipped with a steering actuator that steers the wheels. For example, vehicle 90 is equipped with a front wheel steering device as a steering actuator. The front wheel steering device is a steering device that can change the tire angle of the front wheels among the wheels.

[0021] Vehicle 90 may be equipped with a rear-wheel steering device as a steering actuator that can change the tire angles of the rear wheels among the wheels. In vehicle 90 where steering system 50 is configured with a front-wheel steering device and a rear-wheel steering device, the tire angles of the front wheels and the rear wheels can be changed separately.

[0022] The drive system 30 may include a drive control device configured by a processing circuit that controls the drive system 30. The braking system 40 may include a braking control device configured by a processing circuit that controls the braking system 40. The steering system 50 may include a steering control device configured by a processing circuit that controls the steering system 50. The drive control device, braking control device, and steering control device can receive command values ​​generated by a command value generation unit 14, which will be described later.

[0023] <Anteroposterior force> The longitudinal force will now be explained. The longitudinal force indicates a force acting in the longitudinal direction of the vehicle 90. When the longitudinal force has a positive value, it indicates a force in a direction that accelerates the vehicle 90. On the other hand, when the longitudinal force has a negative value, it indicates a force in a direction that decelerates the vehicle 90. The further the longitudinal force value is from "0," the greater the force acting on the vehicle 90. In other words, the greater the magnitude of the longitudinal force, the greater the force acting on the vehicle 90. The drive actuator and the brake actuator are actuators that generate the longitudinal force. The sum of the drive force and the brake force corresponds to the longitudinal force. The drive actuator and the brake actuator are collectively referred to as the longitudinal force actuator.

[0024] <lateral force> Next, lateral force will be explained. Lateral force refers to a force acting in the lateral direction of the vehicle 90. Lateral force is generated on each wheel depending on the tire angle of the vehicle 90 while turning. A steering actuator is an actuator that generates lateral force. When the lateral force value is positive, it indicates a force in the left direction. On the other hand, when the lateral force value is negative, it indicates a force in the right direction. The further the lateral force value is from "0," the greater the force acting on the wheel. In other words, the greater the magnitude of the lateral force, the greater the force acting on the wheel.

[0025] Vehicle behavior control The vehicle 90 may have a function for controlling the behavior of the vehicle 90. This function can be implemented by, for example, at least one of the drive system 30, the braking system 40, and the steering system 50. This function is implemented, for example, by a CPU executing a program stored in the memory of a processing circuit. One example of this function is a skid prevention function. Other examples of this function include anti-lock brake control, traction control, electric power steering control, rear wheel steering control, and direct yaw moment control.

[0026] The skid mitigation function is a function that suppresses skid of the vehicle 90 by reducing the amount of slip of the wheels when the vehicle 90 turns. Specifically, the skid mitigation function adjusts the longitudinal force acting on the wheels by adjusting at least one of the driving force and the braking force, and this is performed for each wheel individually. For example, the skid mitigation function uses a mechanism that can adjust the longitudinal force generated by the longitudinal force actuator for each wheel individually. If an abnormality occurs in such a mechanism, the skid mitigation function may fail.

[0027] Antilock brake control is a control that suppresses wheel lock by adjusting the braking force to reduce the amount of wheel slip when braking the vehicle 90. Traction control is a control that suppresses the spin of the drive wheels by suppressing acceleration slip of the drive wheels.

[0028] The electric power steering control assists the driver of the vehicle 90 in operating the steering operation member. The rear wheel steering control adjusts the tire angle of the rear wheels by operating the rear wheel steering device. The direct yaw moment control controls the yaw moment of the vehicle 90 by creating a difference in the longitudinal forces on the left and right wheels by controlling at least one of the braking force and the driving force.

[0029] <Information acquisition device> The vehicle 90 may be equipped with an information acquisition device 80 . The information acquisition device 80 is a device for acquiring information about the surroundings of the vehicle 90. The information acquisition device 80 can acquire the relative distance between the vehicle 90 and other vehicles and obstacles located around the vehicle 90. The information acquisition device 80 can also acquire the shape of the road on which the vehicle 90 is traveling and recognize lanes. An example of the information acquisition device 80 is a camera. An example of the information acquisition device 80 is a detection device such as a LiDAR or a millimeter wave radar.

[0030] Another example of the information acquisition device 80 is a GNSS receiver that receives signals from positioning satellites. The current position of the vehicle 90 can be identified based on the signals received by the GNSS receiver.

[0031] The information acquisition device 80 may be configured by one of the above devices, or may be configured by a combination of two or more devices. The information acquisition device 80 may include a processing circuit for processing the acquired information.

[0032] The information acquisition device 80 can output the acquired information to the control device 10. The information acquisition device 80 can also output the acquired information to the driving assistance device 20. The information acquisition device 80 does not necessarily have to be mounted on the vehicle 90. If the vehicle 90 is equipped with a device that receives a signal from the information acquisition device 80 that is provided outside the vehicle 90, the control device 10 and the driving assistance device 20 can use information about the surroundings of the vehicle 90.

[0033] <Driving assistance device> The driving assistance device 20 is configured by a processing circuit that can set a driving route for automatically driving the vehicle 90. The driving assistance device 20 sets the driving route based on information obtained by the information acquisition device 80, for example. The driving assistance device 20 can output a request to drive the vehicle 90 according to the driving route as a driving request.

[0034] The traveling request includes, for example, a target value for yaw rate and a target value for longitudinal acceleration. The traveling request may also include a target position of the vehicle 90, a target value for vehicle speed, etc. The traveling request may also include a priority level indicating whether braking of the vehicle 90 or turning of the vehicle 90 is to be prioritized. For example, when the braking priority level is 50% and the turning priority level is 50%, neither braking nor turning is prioritized. For example, when the braking priority level is 60% and the turning priority level is 40%, braking is prioritized. For example, when the braking priority level is 70% and the turning priority level is 30%, braking is prioritized more than in the example of a braking priority level of 60%.

[0035] <Various sensors> The vehicle 90 is equipped with various sensors. Illustrated in Fig. 1 are a yaw rate sensor SE1, an acceleration sensor SE2, and a wheel speed sensor SE3 as examples of the various sensors. Detection signals from the various sensors are input to the control device 10.

[0036] The yaw rate sensor SE1 is a sensor that detects the yaw rate of the vehicle 90. The acceleration sensor SE2 is composed of a longitudinal acceleration sensor that detects acceleration in the longitudinal direction of the vehicle 90, and a lateral acceleration sensor that detects acceleration in the lateral direction of the vehicle 90.

[0037] The wheel speed sensors SE3 are sensors for detecting wheel speeds, and are provided for each wheel. Control Device The control device 10 is composed of a processing circuit that controls the drive system 30, the braking system 40, and the steering system 50. The control device 10 is equipped with a CPU and a ROM. The ROM of the control device 10 stores various programs that the CPU uses to execute various controls.

[0038] The control device 10 is connected to a drive control device, a braking control device, and a steering control device, and information can be transmitted and received between the control device 10 and the drive control device, the braking control device, and the steering control device.

[0039] The control device 10 is composed of multiple functional units that execute various types of control. Fig. 1 shows, as examples of the functional units, a state quantity calculation unit 11, a control request generation unit 12, a wheel request generation unit 13, and an instruction value generation unit 14. The functional units included in the control device 10 can transmit and receive information to and from each other.

[0040] <State quantity calculation unit> The state quantity calculation unit 11 calculates a vehicle state quantity. In the following, the subscripts added to the end of various symbols indicate which of the wheels of the vehicle 90 the symbols correspond to. Specifically, the subscripts "fl", "fr", "rl", and "rr" correspond to the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The subscript "**" indicates a general term that corresponds to all wheels. The subscript "f*" is a general term that corresponds to the front wheels. The subscript "r*" is a general term that corresponds to the rear wheels.

[0041] The vehicle state quantities calculated by the state quantity calculation unit 11 will be exemplified. The state quantity calculation section 11 can calculate the yaw rate γ based on the detection signal from the yaw rate sensor SE1.

[0042] The state quantity calculation section 11 can calculate the longitudinal acceleration Gx and the lateral acceleration Gy based on the detection signal from the acceleration sensor SE2. The state quantity calculation unit 11 can calculate the wheel speed Vw** of each wheel based on the detection signal from the wheel speed sensor SE3. The state quantity calculation unit 11 can calculate the vehicle body speed Vx based on each wheel speed Vw**. The vehicle body speed Vx indicates the traveling speed of the vehicle 90.

[0043] The state quantity calculation unit 11 can also calculate the longitudinal force and lateral force acting on each wheel. The lateral force can be calculated as the sum of the lateral forces acting on all the wheels, for example, based on the weight m of the vehicle 90, the height of the center of gravity of the vehicle 90, the lateral acceleration Gy, etc. The state quantity calculation unit 11 can calculate the lateral force acting on each wheel from the sum of the lateral forces, taking into account the distribution ratio for each wheel.

[0044] The state quantity calculation unit 11 can calculate the road surface friction coefficient μ** of each wheel. The road surface friction coefficient μ** can be calculated based on the lateral acceleration Gy, for example. The state quantity calculation unit 11 can calculate the ground contact load w** of each wheel. The ground contact load w** can be calculated based on, for example, the weight m of the vehicle 90, the longitudinal acceleration Gx, the lateral acceleration Gy, and the like.

[0045] <Requirement generation unit> The control request generator 12 generates vehicle requests for the vehicle 90 based on requests input from the driving assistance device 20. The control request generator 12, for example, calculates a vehicle longitudinal force request value Fx as a request value for longitudinal force in the vehicle 90. The control request generator 12, for example, calculates a requested moment Mz as a request value for moment in the vehicle 90. The requested moment Mz can be expressed as the product of a yaw moment of inertia and a time derivative value of the yaw rate. The control request generator 12 can also calculate a vehicle lateral force request value Fy as a request value for lateral force in the vehicle 90.

[0046] The wheel requirement generator 13 executes a wheel requirement generation process. In the wheel requirement generation process, a wheel requirement for each wheel is generated based on the vehicle requirement. For example, the wheel requirement generator 13 allocates the vehicle longitudinal force requirement value Fx to each wheel to calculate the required value of the longitudinal force to be applied to each wheel as an individual wheel longitudinal force requirement value Fx**. The wheel requirement generator 13 allocates the required moment Mz to each wheel to calculate the required value of the lateral force to be applied to each wheel as an individual wheel lateral force requirement value Fy**. The individual wheel lateral force requirement value Fy** can also be calculated based on the vehicle lateral force requirement value Fy. As will be described in detail later, the wheel requirement generator 13 can also correct the vehicle requirement when generating the wheel requirement.

[0047] <Indication value generation unit> Command value generation unit 14 generates command values ​​for operating the actuators based on the wheel requirements. Specifically, command value generation unit 14 calculates a command value for controlling the drive actuator and a command value for controlling the braking actuator based on each wheel longitudinal force requirement value Fx**. Command value generation unit 14 calculates a command value for controlling the steering actuator based on each wheel lateral force requirement value Fy**.

[0048] The command value generator 14 can output each calculated command value. Each command value is input to the corresponding system among the drive system 30, the braking system 40, and the steering system 50. The drive system 30, the braking system 40, and the steering system 50 operate their respective actuators based on each command value. For example, in the braking system 40 that has received the command value, the braking control device operates the braking actuator in accordance with the command value.

[0049] <Indication value generation process> The control device 10 executes an instruction value generation process for performing assistance control of the vehicle 90. This process will be described below with reference to Figures 2 and 3. A vehicle control program, which is a program for executing the processes shown in Figures 2 and 3, is stored in the ROM provided in the control device 10. The processes shown in Figures 2 and 3 are realized by the CPU executing the vehicle control program stored in the ROM.

[0050] 2 shows the flow of processing executed by the control device 10. This processing routine is repeatedly executed at predetermined intervals while the assistance control is being executed. When this processing routine starts, first, in step S101, the control device 10 acquires a driving request output by the driving assistance device 20. For example, the control device 10 acquires a target value for the yaw rate, a target value for the longitudinal acceleration, and a priority level. Thereafter, the control device 10 proceeds to step S102.

[0051] In step S102, the control device 10 causes the state quantity calculation unit 11 to calculate the vehicle state quantity. After that, the control device 10 shifts the processing to step S103. In step S103, the control device 10 causes the control request generator 12 to generate a vehicle request. For example, the control request generator 12 calculates a vehicle longitudinal force request value Fx and a request moment Mz. Thereafter, the control device 10 proceeds to step S104.

[0052] In step S104, the control device 10 causes the wheel request generator 13 to execute a wheel request generation process to generate wheel requests. The wheel request generator 13 calculates each wheel longitudinal force request value Fx** and each wheel lateral force request value Fy**. The wheel request generation process will be described in detail later. Thereafter, the control device 10 proceeds to step S105.

[0053] In step S105, the control device 10 causes the command value generating unit 14 to generate a command value. After generating the command value, the command value generating unit 14 outputs the command value to the processing circuit of each system. As a result, in each system, the actuator is operated according to the command value. In this way, the vehicle 90 travels according to the travel request. After causing the command value generating unit 14 to generate the command value, the control device 10 ends this processing routine.

[0054] <Wheel request generation process> 3 shows the flow of processing executed by the wheel request generator 13. This processing routine is executed by the processing of step S104 shown in FIG.

[0055] When this processing routine starts, first in step S201, the wheel demand generator 13 calculates each wheel lateral force demand value Fy**. For example, the wheel demand generator 13 calculates each wheel lateral force demand value Fy** by allocating the demand moment Mz to each wheel. An example of the allocation ratio is a specified value. The allocation ratio may be changed depending on the execution status of control related to the lateral force of each wheel, such as electric power steering control, rear wheel steering control, and direct yaw moment control. After calculating each wheel lateral force demand value Fy**, the wheel demand generator 13 proceeds to step S202.

[0056] In step S202, the wheel demand generator 13 calculates each wheel longitudinal force demand value Fx**. For example, the wheel demand generator 13 calculates each wheel longitudinal force demand value Fx** by allocating the vehicle longitudinal force demand value Fx to each wheel. An example of the allocation ratio is a specified value. The allocation ratio may be changed depending on the execution state of control related to the longitudinal force of each wheel, such as a skid prevention function. Here, for example, if the skid prevention function has failed, the allocation ratio becomes a specified value. After calculating each wheel longitudinal force demand value Fx**, the wheel demand generator 13 proceeds to step S203.

[0057] In step S203 and step S204 following step S203, the wheel requirement generator 13 acquires information about the behavior of the vehicle 90. In step S203, for example, the wheel requirement generator 13 determines whether the behavior of the vehicle 90 is in an oversteer state or not, and whether the behavior of the vehicle 90 is in an understeer state or not, based on the state quantities of the vehicle 90. Hereinafter, the oversteer state may also be referred to as an OS state, and the understeer state may also be referred to as a US state.

[0058] An example of a method for determining whether the vehicle 90 is in the OS state and whether the vehicle 90 is in the US state will be described with reference to FIG. 4. The solid line in FIG. 4 indicates the relationship between the front tire angle δf and the yaw rate γ when the behavior of the vehicle 90 is stable. The dashed-dotted line in FIG. 4 indicates the OS threshold value OSth. The OS threshold value OSth is an offset of the solid line in FIG. 4. The OS threshold value OSth is set so that the value of the yaw rate γ corresponding to the front tire angle δf is larger than the relationship shown by the solid line. The dashed-dotted line in FIG. 4 indicates the US threshold value USth. The US threshold value USth is an offset of the solid line in FIG. 4. The US threshold value USth is set so that the value of the yaw rate γ corresponding to the front tire angle δf is smaller than the relationship shown by the solid line. The relationships shown by the solid line, dashed-dotted line, and dashed-dotted line are determined in advance through experiments, etc. The relationship between the solid line example and the OS threshold value OSth shown by the dashed-dotted line may be changed depending on the state of the vehicle 90 while it is traveling. For example, it may be changed depending on the priority level included in the traveling request. Similarly, the relationship between the example of the solid line and the US threshold USth shown by the two-dot chain line may be changed.

[0059] A calculation map showing a relationship such as that shown in FIG. 4 is stored in, for example, the control device 10. The wheel request generator 13 determines that the vehicle is in the OS state when the yaw rate γ is greater than the OS threshold value OSth for the calculated front wheel tire angle δf based on the calculation map. In other words, when the yaw rate γ is greater than the OS threshold value OSth for the front wheel tire angle δf, the vehicle state quantity indicates that the behavior of the vehicle 90 is in the OS state. The wheel request generator 13 determines that the vehicle is in the US state when the yaw rate γ is smaller than the US threshold value USth for the calculated front wheel tire angle δf based on the calculation map. In other words, when the yaw rate γ is smaller than the US threshold value USth for the front wheel tire angle δf, the vehicle state quantity indicates that the behavior of the vehicle 90 is in the US state.

[0060] If the skid suppression function is activated, the vehicle 90 is controlled in a direction that suppresses behavior similar to that in the OS state or the US state. Therefore, if the yaw rate γ relative to the front wheel tire angle δf exceeds the OS threshold value OSth or the US threshold value USth, the skid suppression function may be malfunctioning. It is possible to determine whether the skid suppression function is malfunctioning using a calculation map showing the relationship illustrated in FIG. 4.

[0061] Returning to FIG. 3, after executing the process of step S203, the wheel request generator 13 proceeds to step S204. In step S204, the wheel request generator 13 acquires the slip state of the wheel. For example, the wheel request generator 13 determines whether the wheel is in a large slip state. A large slip state is a state in which the amount of slip of the wheel is excessive.

[0062] An example of a method for determining whether or not a large slip state is occurring will be described using FIG. 5. The solid line in FIG. 5 is an example showing the time progression of the vehicle longitudinal force request value Fx. The dashed-dotted line in FIG. 5 shows the large slip threshold value SLth. The large slip threshold value SLth is obtained by offsetting the solid line in the direction of the passage of time. The offset amount may be calculated in advance through experiments or the like. The offset amount may be changed depending on the state of the vehicle 90 while it is traveling. For example, it may be changed depending on the priority level included in the traveling request. The dashed line in FIG. 5 is an example of the vehicle longitudinal force estimated from the actual longitudinal acceleration Gx of the vehicle 90. In the example shown in FIG. 5, the dashed line indicates that the vehicle longitudinal force is gradually deviating from the vehicle longitudinal force request value Fx shown by the solid line over time in the direction in which the vehicle longitudinal force is decreasing. The wheel request generator 13 can determine that a large slip state is occurring when the estimated vehicle longitudinal force shown by the dashed line becomes smaller than the large slip threshold value SLth. In other words, the wheel requirement generator 13 can determine that the vehicle is in a large slip state when the vehicle longitudinal force estimated from the actual longitudinal acceleration Gx deviates significantly from the vehicle longitudinal force requirement value Fx.

[0063] Returning to FIG. 3, when the information on the behavior of the vehicle 90 is acquired in steps S203 and S204, the wheel requirement generator 13 shifts the process to step S205. In step S205, if the behavior of the vehicle 90 is in the OS state (S205: YES), the wheel request generator 13 proceeds to step S206.

[0064] In step S206, the wheel demand generator 13 limits the front wheel lateral force demand value Fyf* based on the rear wheel lateral force limit value. As an example, the wheel demand generator 13 limits the front wheel lateral force demand value Fyf* to a magnitude equal to or less than a first lateral force limit value Ly1. The first lateral force limit value Ly1 can be calculated, for example, as follows.

[0065] First, the rear wheel lateral force limit will be explained. The rear wheel lateral force limit is the limit value of the lateral force that can act on the rear wheel. The longitudinal force limit and lateral force limit values ​​for each wheel can be calculated based on the friction circle equation. The size of the friction circle is determined by the product of the road friction coefficient μ** and the ground load w**. The longitudinal force limit value for each wheel corresponds to the maximum value of the longitudinal force within the range in which the resultant of the longitudinal force and the lateral force does not exceed the friction circle. The lateral force limit value for each wheel corresponds to the maximum value of the lateral force within the range in which the resultant of the longitudinal force and the lateral force does not exceed the friction circle. The longitudinal force limit value for each wheel can be expressed as the following relational expression (Equation 1). The lateral force limit value for each wheel can be expressed as the following relational expression (Equation 2).

[0066]

number

[0067] For example, the left front wheel longitudinal force limit value |Fxfllim| can be calculated based on the above relational expression (Equation 1) using the road surface friction coefficient μfl, the ground load wfl, and the left front wheel lateral force demand value Fyfl.

[0068] The wheel requirement generator 13 can calculate the first lateral force limit value Ly1 based on the rear wheel lateral force limit value |Fyr*lim| using the following relational expression (Equation 3).

[0069]

number

[0070] The rear wheel lateral force limit value |Fyr*lim| in the above relational expression (Equation 3) can be calculated based on the above relational expression (Equation 2). In the above relational expression (Equation 3), "lf" indicates the front axle wheelbase. The front axle wheelbase is the horizontal distance between the center of gravity of the vehicle 90 in the longitudinal direction and the axle on which the front wheels are attached. "lr" indicates the rear axle wheelbase. The rear axle wheelbase is the horizontal distance between the center of gravity of the vehicle 90 in the longitudinal direction and the axle on which the rear wheels are attached. The sum of the front axle wheelbase and the rear axle wheelbase corresponds to the wheelbase of the vehicle 90.

[0071] That is, in step S206, the wheel demand generator 13 calculates the rear wheel lateral force limit value |Fyr*lim| and calculates the first lateral force limit value Ly1 based on the rear wheel lateral force limit value |Fyr*lim|. Then, if the magnitude of the front wheel lateral force request value Fyf* calculated in step S201 is greater than the first lateral force limit value Ly1, the wheel demand generator 13 corrects the front wheel lateral force request value Fyf*. That is, in this case, the wheel demand generator 13 corrects the front wheel lateral force request value Fyf* so that the magnitude of the front wheel lateral force request value Fyf* is equal to or less than the first lateral force limit value Ly1. An example of the corrected front wheel lateral force request value Fyf* is a value equal to the first lateral force limit value Ly1. As a result, the tire angle of the front wheels is adjusted in accordance with the command value calculated from the front wheel lateral force request value Fyf*. After limiting the front wheel lateral force request value Fyf*, the wheel request generator 13 proceeds to step S207.

[0072] In step S207, the wheel requirement generator 13 limits the vehicle longitudinal force requirement value Fx so as to limit the longitudinal force of the turning outer rear wheel. Here, the turning outer rear wheel corresponds to the rear wheel located on the outer side as viewed from the turning center of the turning vehicle 90. For example, when the forward moving vehicle 90 is turning clockwise, the left rear wheel is the turning outer rear wheel.

[0073] As an example, the wheel requirement generator 13 reduces the magnitude of the vehicle longitudinal force requirement value Fx so that the longitudinal force acting on the turning outer rear wheel becomes equal to or less than the first longitudinal force limit value Lx1. The wheel requirement generator 13 sets the rear wheel longitudinal force limit value |Fxr*lim| as the first longitudinal force limit value Lx1, as expressed by the following relational expression (Equation 5).

[0074]

number

[0075] That is, in step S207, the wheel demand generator 13 calculates the rear wheel longitudinal force limit value |Fxr*lim| and sets the rear wheel longitudinal force limit value |Fxr*lim| to the first longitudinal force limit value Lx1. Then, taking into consideration the distribution ratio for each wheel described in the processing of step S202, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the outside rear wheel longitudinal force demand value is calculated to be a value equal to or less than the first longitudinal force limit value Lx1. For example, if the magnitude of the outside rear wheel longitudinal force demand value is greater than the first longitudinal force limit value Lx1, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the outside rear wheel longitudinal force demand value is equal to or less than the first longitudinal force limit value Lx1. For example, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the magnitude of the outside rear wheel longitudinal force demand value becomes equal to the first longitudinal force limit value Lx1. Note that here, the wheel demand generator 13 reduces the magnitude while maintaining the positive or negative sign of the vehicle longitudinal force demand value Fx.

[0076] When the vehicle longitudinal force request value Fx is limited in step S207, the wheel request generator 13 proceeds to step S213. On the other hand, if the behavior of the vehicle 90 is not the OS state in the process of step S205 (S205: NO), the wheel request generator 13 shifts the process to step S208. If the behavior of the vehicle 90 is the US state (S208: YES), the wheel request generator 13 shifts the process to step S209.

[0077] In step S209, the wheel request generator 13 limits the front wheel lateral force request value Fyf* based on the front wheel lateral force limit value |Fyf*lim|. As an example, the wheel request generator 13 limits the front wheel lateral force request value Fyf* to a magnitude equal to or less than the second lateral force limit value Ly2. The front wheel lateral force limit value |Fyf*lim| can be expressed as the above relational expression (Equation 2). The wheel request generator 13 sets the front wheel lateral force limit value |Fyf*lim| as the second lateral force limit value Ly2, as expressed as the above relational expression (Equation 4).

[0078] That is, in step S209, the wheel demand generator 13 calculates the front wheel lateral force limit value |Fyf*lim| and sets the front wheel lateral force limit value |Fyf*lim| to the second lateral force limit value Ly2. Then, if the magnitude of the front wheel lateral force request value Fyf* calculated in step S201 is greater than the second lateral force limit value Ly2, the wheel demand generator 13 corrects the front wheel lateral force request value Fyf*. That is, in this case, the wheel demand generator 13 corrects the front wheel lateral force request value Fyf* so that the magnitude of the front wheel lateral force request value Fyf* is equal to or less than the second lateral force limit value Ly2. An example of the corrected front wheel lateral force request value Fyf* is a value equal to the second lateral force limit value Ly2. As a result, the tire angle of the front wheels is adjusted in accordance with a command value calculated from the front wheel lateral force request value Fyf*. After limiting the front wheel lateral force request value Fyf*, the wheel request generator 13 proceeds to step S210.

[0079] In step S210, the wheel requirement generator 13 limits the vehicle longitudinal force requirement value Fx so as to limit the longitudinal force of the outside front wheel. Here, the outside front wheel corresponds to the front wheel located on the outside of the turning center of the turning vehicle 90. For example, when the forward moving vehicle 90 is turning clockwise, the left front wheel is the outside front wheel.

[0080] As an example, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the longitudinal force acting on the outside front wheel becomes equal to or less than the second longitudinal force limit value Lx2. The wheel demand generator 13 sets the front wheel longitudinal force limit value |Fxf*lim| as the second longitudinal force limit value Lx2, as expressed by the above relational expression (Equation 6).

[0081] That is, in step S210, the wheel demand generator 13 calculates the front wheel longitudinal force limit value |Fxf*lim| and sets the front wheel longitudinal force limit value |Fxf*lim| to the second longitudinal force limit value Lx2. Then, taking into consideration the distribution ratio for each wheel described in the processing of step S202, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the outside front wheel longitudinal force demand value is calculated to be a value equal to or less than the second longitudinal force limit value Lx2. For example, if the magnitude of the outside front wheel longitudinal force demand value is greater than the second longitudinal force limit value Lx2, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the magnitude of the outside front wheel longitudinal force demand value is equal to or less than the second longitudinal force limit value Lx2. For example, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the magnitude of the outside front wheel longitudinal force demand value becomes equal to the second longitudinal force limit value Lx2. Note that here, the wheel demand generator 13 reduces the magnitude while maintaining the positive or negative sign of the vehicle longitudinal force demand value Fx.

[0082] When the vehicle longitudinal force request value Fx is limited in step S210, the wheel request generator 13 proceeds to step S213. On the other hand, if the behavior of the vehicle 90 is not in the US state in the processing of step S208 (S208: NO), the wheel request generator 13 proceeds to step S211. If the behavior of the vehicle 90 is not in the large slip state (S211: NO), the wheel request generator 13 ends this processing routine. If the behavior of the vehicle 90 is in the large slip state (S211: YES), the wheel request generator 13 proceeds to step S212.

[0083] In step S212, the wheel demand generator 13 limits the vehicle longitudinal force demand value Fx based on each wheel longitudinal force limit value. As an example, the wheel demand generator 13 limits the vehicle longitudinal force demand value Fx so that each wheel longitudinal force demand value Fx** is equal to or less than the third longitudinal force limit value Lx3. The wheel demand generator 13 sets the third longitudinal force limit value Lx3 as expressed in the above relational expression (Equation 7). "min" in the relational expression (Equation 7) is a function that returns the smaller value of any of the arguments. In other words, the smallest value among the wheel longitudinal force limit values ​​|Fx**lim| is the third longitudinal force limit value Lx3.

[0084] That is, in step S212, the wheel demand generator 13 calculates each wheel longitudinal force limit value |Fx**lim| and sets the smallest value among the wheel longitudinal force limit values ​​|Fx**lim| as the third longitudinal force limit value Lx3. Then, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that all of the wheel longitudinal force demand values ​​Fx** become equal to or less than the third longitudinal force limit value Lx3. For example, the wheel demand generator 13 reduces the magnitude of the vehicle longitudinal force demand value Fx so that the magnitude of the largest demand value among the wheel longitudinal force demand values ​​Fx** becomes equal to the third longitudinal force limit value Lx3. Note that here, the wheel demand generator 13 reduces the magnitude while maintaining the positive or negative sign of the vehicle longitudinal force demand value Fx.

[0085] When the vehicle longitudinal force request value Fx is limited in step S212, the wheel request generator 13 proceeds to step S213. In step S213, the wheel request generator 13 counts the duration T. For example, when the process is shifted from step S207, the wheel request generator 13 counts the duration T as the time during which the OS state continues. When the OS state is resolved, the wheel request generator 13 initializes the duration T to "0." For example, when the process is shifted from step S210, the wheel request generator 13 counts the duration T as the time during which the US state continues. When the US state is resolved, the wheel request generator 13 initializes the duration T to "0." For example, when the process is shifted from step S212, the wheel request generator 13 counts the duration T as the time during which the large slip state continues. When the large slip state is resolved, the wheel request generator 13 initializes the duration T to "0." After counting the duration T, the wheel request generator 13 shifts the process to step S214.

[0086] In step S214, the wheel request generator 13 determines whether the duration T is longer than the specified time Tth. If the duration T is equal to or shorter than the specified time Tth (S214: NO), the wheel request generator 13 ends this processing routine. On the other hand, if the duration T is longer than the specified time Tth (S214: YES), the wheel request generator 13 proceeds to step S215.

[0087] The designated time Tth will be described. The designated time Tth is a threshold value for determining whether the OS state, the US state, or the large slip state continues for a long time without being resolved. For example, the designated time Tth is set to a value calculated in advance through experiments or the like as an initial value. The wheel request generator 13 can increase or decrease the designated time Tth. For example, the wheel request generator 13 can increase or decrease the designated time Tth based on whether the priority level included in the traveling request input from the driving assistance device 20 prioritizes braking of the vehicle 90 or turning of the vehicle 90. As an example, the wheel request generator 13 lengthens the designated time Tth when braking is prioritized compared to when turning is prioritized. The amount to be added when lengthening the designated time Tth may be changed depending on the level of the braking priority. For example, when the braking priority is 70%, the designated time Tth may be longer than when the braking priority is 60%.

[0088] In step S215, the wheel request generator 13 further reduces the magnitude of the vehicle longitudinal force request value Fx. That is, when the duration T is longer than the specified time Tth, the wheel request generator 13 reduces the magnitude of the vehicle longitudinal force request value Fx more than when the duration T is equal to or shorter than the specified time Tth. Thereafter, the wheel request generator 13 ends this processing routine.

[0089] In this embodiment, the control device 10 performs the process of reflecting the vehicle longitudinal force request value Fx, the magnitude of which is reduced in steps S207, S210, S211, and S215, in the longitudinal force as follows. Here, the braking force generated by the brake actuator is reduced, thereby adjusting the longitudinal force by reducing the magnitude of the vehicle longitudinal force request value Fx. Note that, since the magnitude of the vehicle longitudinal force request value Fx, which is a vehicle request, is reduced, the total braking force applied to each wheel is reduced. One method of reducing the braking force in this way is to reduce the braking force for all of the wheels. Specifically, one method is to reduce the braking force applied to the vehicle 90 by performing regenerative cooperative control.

[0090] <Action and Effects> The operation and effects of this embodiment will be described. According to the control device 10, when the vehicle state quantity indicates that the behavior of the vehicle 90 is in an OS state when the sideslip suppression function has failed (S205: YES), the magnitude of the front wheel lateral force request value Fyf* is limited (S206). The tire angle of the front wheels is controlled based on this front wheel lateral force request value Fyf*. The first lateral force limit value Ly1 that limits the magnitude of the front wheel lateral force request value Fyf* is set to the limit value of the lateral force that can act on the rear wheels while traveling. Therefore, the lateral force acting on the front wheels of the vehicle 90 in the OS state can be limited based on the rear wheels of the vehicle 90 in the OS state. By adjusting the tire angle of the front wheels in accordance with the limited front wheel lateral force request value Fyf* in this manner, the difference between the lateral force of the front wheels and the lateral force of the rear wheels of the vehicle 90 during cornering can be reduced. This suppresses the OS state and stabilizes the behavior of the vehicle 90.

[0091] According to the control device 10, when the vehicle state quantity indicates that the behavior of the vehicle 90 is in an OS state when the skid suppression function has failed (S205: YES), the magnitude of the vehicle longitudinal force request value Fx is limited (S207). Specifically, the longitudinal force acting on the outside rear wheel of the turning wheel is limited to less than or equal to the first longitudinal force limit value Lx1, that is, less than or equal to the limit value of the longitudinal force that can act on the rear wheel. As a result, for the vehicle 90 in the OS state, the grip force of the outside rear wheel of the turning wheel can be ensured by applying a longitudinal force to the outside rear wheel of the turning wheel within a range that does not exceed the friction circle. This makes it possible to suppress the OS state and stabilize the behavior of the vehicle 90.

[0092] According to the control device 10, when the vehicle state quantity indicates that the behavior of the vehicle 90 is in the US state when the sideslip suppression function has failed (S208: YES), the magnitude of the vehicle longitudinal force request value Fx is limited (S210). Specifically, the longitudinal force acting on the outside front wheel is limited to less than or equal to the second longitudinal force limit value Lx2, that is, less than or equal to the limit value of the longitudinal force that can act on the front wheel. As a result, for the vehicle 90 in the US state, the grip force of the outside front wheel can be ensured by applying a longitudinal force to the outside front wheel within a range that does not exceed the friction circle. This makes it possible to suppress the US state and stabilize the behavior of the vehicle 90.

[0093] According to the control device 10, when the vehicle state quantities indicate that the behavior of the vehicle 90 is in the US state when the sideslip suppression function has failed (S208: YES), the magnitude of the front wheel lateral force request value Fyf* is limited (S209). The tire angle of the front wheels is controlled based on this front wheel lateral force request value Fyf*. The second lateral force limit value Ly2 that limits the magnitude of the front wheel lateral force request value Fyf* is set to the limit value of the lateral force that can act on the front wheels while traveling. As a result, by applying a large lateral force to the front wheels within a range that does not exceed the friction circle, the grip of the front wheels can be ensured. This makes it possible to suppress the US state and stabilize the behavior of the vehicle 90.

[0094] According to the control device 10, the specified time Tth is set longer when braking is prioritized than when turning is prioritized, based on the priority level included in the travel request. As a result, the process of step S215 is not executed unless the duration T becomes longer. In other words, the magnitude of the vehicle longitudinal force request value Fx is not reduced as much when braking is prioritized compared to when turning is prioritized. As a result, the period during which a larger braking force is applied can be extended when braking is prioritized.

[0095] According to the control device 10, when the vehicle state quantity indicates that the behavior of the vehicle 90 is in a large slip state when the skid suppression function has failed (S211: YES), the magnitude of the vehicle longitudinal force request value Fx is limited (S212). Specifically, the longitudinal force acting on each wheel is limited to less than or equal to the third longitudinal force limit value Lx3, that is, less than or equal to the smallest value of the respective wheel longitudinal force limit values ​​|Fx**lim|. As a result, for the vehicle 90 in a large slip state, a longitudinal force can be applied to each wheel within a range that does not exceed the friction circle. This makes it possible to suppress the large slip state and stabilize the behavior of the vehicle 90.

[0096] Incidentally, the skid suppression function can generate a yaw moment in a direction that resolves a state in which the behavior of the vehicle 90 is unstable, such as an OS state, a US state, or a large slip state. Even in cases in which it is not possible to expect a yaw moment to act on the vehicle 90 in a direction that resolves the state in which the behavior of the vehicle 90 is unstable, the control device 10 can suppress the unstable behavior and stabilize the behavior of the vehicle 90.

[0097] (Example of change) This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0098] In the above embodiment, when the magnitude of the vehicle longitudinal force request value Fx is reduced, the braking force generated by the brake actuator is reduced as a process for reflecting the vehicle longitudinal force request value Fx in the longitudinal force. However, this is not limiting, and it is sufficient if the magnitude of the longitudinal force can be reduced by controlling the longitudinal force actuator. For example, the drive force generated by the drive actuator may be increased so that the longitudinal force approaches "0."

[0099] The processes of steps S213 to S215 shown in FIG. 3 in the above embodiment may be omitted. The processes of steps S211 and S212 in the above embodiment shown in Fig. 3 may be omitted. In this case, the processing routine may be ended if a negative determination is made in the process of step S208.

[0100] In the above embodiment, the processes of steps S206 and S207 are executed when the vehicle is in the OS state. When the vehicle is in the OS state, it is sufficient to execute at least the process of limiting the front wheel lateral force request value Fyf* based on the rear wheel lateral force limit value. In other words, the process of step S207 can be omitted. Even in this case, the OS state can be suppressed and the behavior of the vehicle 90 can be stabilized.

[0101] In the above embodiment, the processing of steps S209 and S210 is executed when the vehicle is in the US state. When the vehicle is in the US state, for example, at least executing processing to limit the vehicle longitudinal force request value Fx so as to limit the longitudinal force of the outside front wheel can stabilize the behavior of the vehicle 90. That is, the processing of step S209 can be omitted. Also, for example, at least executing processing to limit the front wheel lateral force request value Fyf* based on the front wheel lateral force limit value can stabilize the behavior of the vehicle 90. That is, the processing of step S210 can be omitted.

[0102] In the above embodiment, the case where the vehicle 90 is moved forward has been described. That is, in the above embodiment, the "front wheels" are wheels located on the front side of the vehicle 90 in the direction of travel. A wheel located on the front side of the vehicle 90 in the direction of travel in this manner is referred to as a "first wheel." Also, in the above embodiment, the "rear wheels" are wheels located on the rear side of the vehicle 90 in the direction of travel. A wheel located on the rear side of the vehicle 90 in the direction of travel in this manner is referred to as a "second wheel." Control targeting the "front wheels" in the above embodiment can be rephrased as control targeting the "first wheel." Control targeting the "rear wheels" in the above embodiment can be rephrased as control targeting the "second wheel."

[0103] Now, consider the case where the vehicle 90 is driven in reverse. In this case, the wheels located on the front side in the traveling direction of the vehicle 90 are the wheels attached to the rear of the vehicle 90, i.e., the "rear wheels." In other words, the "rear wheels" correspond to the "first wheels." Similarly, the wheels located on the rear side in the traveling direction of the vehicle 90 are the wheels attached to the front of the vehicle 90, i.e., the "front wheels." In other words, the "front wheels" correspond to the "second wheels."

[0104] In other words, even when applying the assistance control in the above embodiment when moving the vehicle 90 in reverse, the same effect as when moving the vehicle 90 forward can be achieved by performing control targeting the "first wheel" and control targeting the "second wheel."

[0105] The control device 10, drive control device, braking control device, steering control device, and driving assistance device 20, which are processing circuits, may have any of the following configurations [a] to [c]. [a] A circuit having one or more processors that execute various processes according to a computer program. The processor includes a processing device. Examples of the processing device include a CPU, a DSP, and a GPU. The processor includes a memory. Examples of the memory include a RAM, a ROM, and a flash memory. The memory stores program code or instructions configured to cause the processing device to execute the processes. The memory, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. [b] A circuit having one or more hardware circuits that execute various processes. Examples of hardware circuits include an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array). [c] A circuit having a processor that executes some of the various processes according to a computer program and a hardware circuit that executes the remaining processes.

[0106] Some or all of the functions realized by the drive control device, the braking control device, the steering control device, and the processing circuits in the driving assistance device 20 may be realized by the control device 10. Some of the functions implemented by the control device 10 may be implemented by other processing circuits connected to the control device 10.

[0107] (technical thought) The technical ideas that can be understood from the above-described embodiment and modified examples will be described. [A] A vehicle control method for automatically driving a vehicle having a driving assistance device that assists the driving of the vehicle, a drive actuator and a braking actuator that generate longitudinal forces that indicate forces that act in the longitudinal direction of the vehicle, and a steering actuator that adjusts a tire angle that is the steering angle of the wheels of the vehicle, the vehicle having a skid suppression function that suppresses skid of the vehicle by separately adjusting the longitudinal forces that act on each wheel, by controlling the vehicle based on a request output by the driving assistance device, the method comprising: a state quantity calculation process for calculating a state quantity including a yaw rate of the vehicle; a wheel requirement generation process for calculating each wheel lateral force requirement value based on the requirements as a lateral force requirement value for the wheel; and a command value generation process for outputting a command value for controlling the steering actuator based on the required wheel lateral force value for each wheel, In the wheel request generation process, When the state quantity indicates that the behavior of the vehicle is in an oversteer state when the skid suppression function has failed, A vehicle control method which calculates a limit value of lateral force that can act on a rear wheel among the wheels while the vehicle is running as a first lateral force limit value, and limits a front wheel lateral force demand value, which is the wheel lateral force demand value for the front wheel among the wheels, to a magnitude equal to or less than the first lateral force limit value. [Explanation of symbols]

[0108] 10...Control device 11...State quantity calculation unit 12...Control request generation unit 13…Wheel requirement generation unit 14...Indication value generating unit 20...Driving assistance device 30...Drive system 40...Braking system 50...Steering system 80...Information acquisition device 90...Vehicle

Claims

1. A vehicle control device is applied to a vehicle having a driving assistance device that assists in vehicle driving, a drive actuator and a braking actuator that generate longitudinal forces that indicate forces that act in the longitudinal direction of the vehicle, and a steering actuator that adjusts a tire angle that is the steering angle of a wheel of the vehicle, and controls the vehicle based on a request input from the driving assistance device, thereby automatically driving the vehicle, a state quantity calculation unit that calculates a state quantity including a yaw rate of the vehicle; a wheel requirement generating unit that calculates each wheel lateral force requirement value as a lateral force requirement value for the wheel based on the requirement; an instruction value generating unit that outputs an instruction value for controlling the steering actuator based on each of the required wheel lateral forces, The vehicle is provided with a skid suppression function that suppresses skid of the vehicle by separately adjusting the longitudinal forces acting on each wheel, The wheel request generating unit When the state quantity indicates that the behavior of the vehicle is in an oversteer state when the skid suppression function has failed, A value calculated while the vehicle is traveling as a limit value of the lateral force that can act on the rear wheels among the wheels is set as a first lateral force limit value, and for the front wheels among the wheels, a front wheel lateral force demand value that is the individual wheel lateral force demand value for the front wheels is limited to a magnitude equal to or less than the first lateral force limit value. Vehicle control device.

2. a control request generating unit that calculates a vehicle longitudinal force request value as a longitudinal force request value of the vehicle based on the request; the wheel requirement generating unit calculates a required value of a longitudinal force to be applied to each wheel as an individual wheel longitudinal force required value based on the vehicle longitudinal force required value, the instruction value generation unit outputs an instruction value for controlling the drive actuator and an instruction value for controlling the braking actuator based on the required front / rear force values ​​for each wheel, The wheel request generating unit When the state quantity indicates that the behavior of the vehicle is in an oversteer state when the skid suppression function has failed, a value calculated while the vehicle is traveling as a limit value of a longitudinal force that can act on the rear wheel among the wheels is defined as a first longitudinal force limit value, and a rear wheel among the wheels that is located on the outer side as viewed from the turning center of the vehicle is defined as an outer rear wheel, The magnitude of the vehicle longitudinal force request value is reduced so that the longitudinal force acting on the turning outer rear wheel is equal to or less than the first longitudinal force limit value. The vehicle control device according to claim 1 .

3. The wheel request generation unit When the state quantity indicates that the behavior of the vehicle is in an understeer state when the skid suppression function has failed, a value calculated while the vehicle is traveling as a limit value of the longitudinal force that can act on the front wheels among the wheels is defined as a second longitudinal force limit value, and a front wheel among the wheels that is located on the outer side as viewed from the turning center of the vehicle is defined as an outer front wheel, The magnitude of the vehicle longitudinal force request value is reduced so that the longitudinal force acting on the outside front wheel is equal to or less than the second longitudinal force limit value. The vehicle control device according to claim 2.

4. The wheel request generation unit When the state quantity indicates that the behavior of the vehicle is in an understeer state when the skid suppression function has failed, A value calculated while the vehicle is traveling as a limit value of the lateral force that can act on the front wheels among the wheels is set as a second lateral force limit value, and for the front wheels among the wheels, a front wheel lateral force demand value that is the individual wheel lateral force demand value for the front wheels is limited to a magnitude equal to or less than the second lateral force limit value. The vehicle control device according to any one of claims 1 to 3.

5. The wheel request generation unit When the duration during which the state quantity indicates that the behavior of the vehicle is in an oversteer state or an understeer state is longer than a specified designated time, the magnitude of the vehicle longitudinal force request value is reduced more than when the duration is equal to or shorter than the specified time, Based on whether the request from the driving assistance device prioritizes braking of the vehicle or turning of the vehicle, the specified time is made longer when braking is prioritized than when turning is prioritized. The vehicle control device according to claim 2 or 3.

6. A vehicle control program for automatically driving a vehicle having a driving assistance device that assists the driving of the vehicle, a drive actuator and a braking actuator that generate longitudinal forces that indicate forces that act in the longitudinal direction of the vehicle, and a steering actuator that adjusts a tire angle that is the steering angle of the wheels of the vehicle, the vehicle having a skid suppression function that suppresses skid of the vehicle by separately adjusting the longitudinal forces that act on each wheel, by causing a control device of the vehicle to execute assistance control that controls the vehicle based on a request output by the driving assistance device, a state quantity calculation process for calculating a state quantity including a yaw rate of the vehicle; a wheel requirement generation process for calculating each wheel lateral force requirement value based on the requirements as a lateral force requirement value for the wheel; a command value generation process for outputting a command value for controlling the steering actuator based on the required wheel lateral force value for each wheel, In the wheel request generation process, When the state quantity indicates that the behavior of the vehicle is in an oversteer state when the sideslip suppression function has failed, A value calculated while the vehicle is traveling as a limit value of the lateral force that can act on the rear wheels among the wheels is set as a first lateral force limit value, and for the front wheels among the wheels, a front wheel lateral force demand value that is the individual wheel lateral force demand value for the front wheels is limited to a magnitude equal to or less than the first lateral force limit value. Vehicle control program.

Images