Vehicle control device, computer-readable medium storing a vehicle control program, and vehicle control method

Abstract

The present application provides a vehicle control device, a computer readable medium storing a vehicle control program, and a vehicle control method. The vehicle is provided with a side slip prevention function that suppresses side slip by independently adjusting front and rear forces acting on each wheel for each wheel. The control device automatically drives the vehicle by controlling the vehicle based on a request input from a driving support device. The control device is provided with a wheel request generation section that calculates a request value for lateral force for each wheel, i.e., each wheel lateral force request value, based on a request input from the driving support device. The wheel request generation section limits each wheel lateral force request value for the front wheels to a size that is below a limit value of lateral force that can act on the rear wheels, i.e., a first lateral force limit value, when the running condition of the vehicle is an oversteering state in the event that the side slip prevention function fails.

Description

TECHNICAL FIELD

[0001] The present application relates to a vehicle control device applied to a vehicle that automatically travels, a computer-readable medium storing a vehicle control program, and a vehicle control method. BACKGROUND

[0002] A driving support device that causes a vehicle to automatically travel is known. Japanese Patent Application Publication No. 2020-157890 discloses a control device that suppresses continuation of a state in which a running situation of an automatically traveling vehicle is unstable. The control device disclosed in the publication is configured to perform running situation stabilization control that achieves elimination of the unstable state. Specifically, the running situation stabilization control causes the vehicle to generate a yaw moment by causing a difference in braking force between inner and outer wheels of the turning vehicle when the running situation of the vehicle is in an over-steering state or an under-steering state. The publication also shows a configuration that reduces the vehicle speed when the running situation of the vehicle is not stabilized even if the above-described running situation stabilization control is performed.

[0003] When a force in a direction in which the vehicle speed is reduced is applied to the wheels in order to reduce the vehicle speed, it can be said in accordance with the theory of a friction circle that the following case. Increasing the force in the direction in which the vehicle speed is reduced is accompanied by a decrease in the lateral force that can be applied to the wheels without causing the wheels to slip. Therefore, during the period in which the force in the direction in which the vehicle speed is reduced is increased in the turning of the vehicle, there is a case in which the lateral force that only stabilizes the vehicle cannot be generated. In other words, during the period in which the force in the direction in which the vehicle speed is reduced is increased, there is a problem that the state in which the running situation of the vehicle is unstable is not easily eliminated. SUMMARY

[0004] In one embodiment of the present disclosure, a vehicle control device is provided that is configured to automatically control a vehicle based on a request input from a driving support device that supports driving of the vehicle. The vehicle includes the driving support device, wheels including front wheels and rear wheels, drive actuators and brake actuators that generate a fore-aft force that is a force acting in a fore-aft direction of the vehicle, and a steering actuator that adjusts a respective steering angle, i.e., a tire angle, of the wheels. The vehicle control device includes a state quantity calculation unit configured to calculate a state quantity including a yaw rate of the vehicle, a wheel request generation unit configured to calculate a respective wheel lateral force request value that is a request value for a lateral force of each wheel based on the request, and an instruction value generation unit configured to output an instruction value for controlling the steering actuator based on the respective wheel lateral force request values. The vehicle includes a side-slip prevention function that is a function of suppressing side-slip of the vehicle by independently adjusting the fore-aft force acting on each wheel for each wheel. The wheel request generation unit is configured to, in the event that the side-slip prevention function fails, calculate a first lateral force limit value that is a limit value of a lateral force that can act on the rear wheels when the state quantity indicates that a running condition of the vehicle is an over-steering state, and limit a front wheel lateral force request value to a magnitude that is equal to or less than the first lateral force limit value, of the respective wheel lateral force request values, where the front wheel lateral force request value is the respective wheel lateral force request value for the front wheels.

[0005] In another aspect of the disclosure, a computer-readable medium storing a vehicle control program that causes a vehicle to automatically travel by causing a control device of the vehicle to execute assistance control that controls the vehicle based on a request output by a driving assistance device that assists travel of the vehicle is provided. The vehicle has the driving assistance device, wheels including front wheels and rear wheels, drive actuators and brake actuators that generate a fore-aft force that indicates a force acting in a fore-aft direction of the vehicle, and a steering actuator that adjusts respective steering angles, i.e., tire angles, of the wheels. The vehicle is provided with a side-slip prevention function that suppresses side-slip of the vehicle by independently adjusting the fore-aft force acting on each wheel for each wheel. The vehicle control program is configured to cause the control device to execute a state quantity calculation process that calculates a state quantity including a yaw rate of the vehicle, a wheel request generation process that calculates, based on the request, a wheel lateral force request value that is a request value for a lateral force of each wheel, and an instruction value generation process that outputs an instruction value that controls the steering actuator based on the wheel lateral force request value. The wheel request generation process includes, in the event that the side-slip prevention function fails, when the state quantity indicates that a running condition of the vehicle is an over-steering state, calculating a first lateral force limit value that is a limit value of a lateral force that can act on the rear wheels, and limiting a front wheel lateral force request value to a magnitude that is equal to or less than the first lateral force limit value, of the wheel lateral force request value, where the front wheel lateral force request value is the wheel lateral force request value for the front wheels.

[0006] In another aspect of the present disclosure, a vehicle control method is provided for automatically driving the vehicle by controlling the vehicle based on a request output by a driving support device that assists the vehicle's travel. The vehicle includes: the driving support device; wheels, including front and rear wheels; a drive actuator and a brake actuator that generate fore-aft forces, representing forces acting on the vehicle in the fore-aft direction; and a steering actuator that adjusts the steering angles, or tire angles, of each of the wheels. The vehicle includes a side slip prevention function that suppresses side slip by independently adjusting the fore-aft forces acting on each wheel. The vehicle control method includes: a state quantity calculation process for calculating state quantities including the yaw rate of the vehicle; a wheel request generation process for calculating a wheel lateral force request value based on the request; and an instruction value generation process for outputting an instruction value for controlling the steering actuator based on the wheel lateral force request value. The wheel requirement generation process includes calculating a first lateral force limit value and limiting the front wheel lateral force requirement value to a value below the first lateral force limit value when the anti-skid function fails and the state quantity indicates that the vehicle is in an oversteering state, wherein the first lateral force limit value is a limit value of the lateral force that can act on the rear wheel, and the front wheel lateral force limit value is a lateral force requirement value for each of the front wheels. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing one embodiment of a vehicle control device and a vehicle that is a control target of the vehicle control device.

[0008] Figure 2 Yes Figure 1 Flowchart of the process flow of the vehicle control device executed when performing support control for automatically driving the vehicle.

[0009] Figure 3 Yes Figure 1 Flowchart of the process of processing performed by the vehicle control device when generating a wheel request.

[0010] Figure 4 Yes Figure 1 A graph showing the relationship between the front wheel tire angle and the yaw rate used by a vehicle control device to determine the behavior of the vehicle.

[0011] Figure 5 It is an explanation Figure 1 A graph showing threshold values ​​of vehicle front and rear forces used by a vehicle control device to determine the operating conditions of the vehicle. DETAILED DESCRIPTION

[0012] Below, refer to Figures 1-5An embodiment of the control device 10 as a vehicle control device will be described.

[0013] Figure 1 The control device 10 and a vehicle 90 to which the control device 10 is applied will be described. The vehicle 90 is provided with a drive assist device 20 that assists driving of the vehicle 90. The control device 10 is capable of performing assist control that causes the vehicle 90 to automatically drive by controlling the vehicle 90 based on a request input from the drive assist device 20. In the present embodiment, the assist control will be described as control that causes the vehicle 90 to advance.

[0014] <VEHICLE>

[0015] The vehicle 90 is provided with, for example, four wheels including two front wheels 60F and two rear wheels 60R.

[0016] As shown in Figure 1 , the vehicle 90 is provided with a drive system 30 that transmits a driving force to the wheels. The drive system 30 is provided with a drive actuator 31 that generates the driving force. The vehicle 90 is provided with, for example, a motor generator as one example of the drive actuator 31. By causing the motor generator to function as a motor, the driving force can be generated. The drive actuator 31 can also be an internal combustion engine. The motor generator and the internal combustion engine can be employed as the drive actuator 31. As other examples of the drive actuator 31, there are in-wheel motors.

[0017] The drive system 30 is configured to be capable of transmitting the driving force to all of the wheels, for example. The drive system 30 can be configured to be capable of transmitting the driving force to the front wheels 60F among the wheels, or can be configured to be capable of transmitting the driving force to the rear wheels 60R among the wheels.

[0018] The vehicle 90 is provided with a brake system 40 that imparts a braking force to the wheels. The brake system 40 is provided with a brake actuator 41 that generates the braking force. The brake actuator 41 is configured by, for example, a friction brake device and a regenerative brake device.

[0019] As the friction brake device, there is a hydraulic brake device. The friction brake device is provided with a brake mechanism corresponding to each wheel. The brake mechanism is configured by a rotating body that rotates integrally with the wheel, a friction member that can be pressed to the rotating body, and a wheel cylinder that presses the friction member to the rotating body in accordance with hydraulic pressure. One example of the brake mechanism is a disc brake. The brake mechanism can also be a drum brake. Other examples of the friction brake device are an electric brake device that mechanically transmits a driving force of an electric motor to press the friction member to the rotating body.

[0020] One example of the regenerative brake device is the above-described motor generator. By causing the motor generator to function as a generator, a regenerative braking force can be applied to the wheel. Other examples of the regenerative brake device are in-wheel motors.

[0021] As the control that the braking system 40 can implement, there is regenerative coordination control. The regenerative coordination control is control that makes a desired braking force act on the vehicle 90 by coordinating a regenerative braking force based on the regenerative braking device with a frictional braking force based on the frictional braking device.

[0022] Further, the braking actuator 41 that the braking system 40 is provided with is not limited to being constituted by the frictional braking device and the regenerative braking device. The braking actuator 41 can be constituted by only the frictional braking device, or the braking actuator 41 can be constituted by only the regenerative braking device.

[0023] The vehicle 90 is provided with a steering manipulation system 50 that can adjust the steering angle of the wheels, that is, the tire angles. The steering manipulation system 50 is provided with a steering actuator 51 that steers the wheels. For example, the vehicle 90 is provided with a front wheel steering device as the steering actuator 51. The front wheel steering device is a steering device that can change the tire angle of the front wheels 60F among the wheels.

[0024] The vehicle 90 can also be provided with a rear wheel steering device that can change the tire angle of the rear wheels 60R among the wheels as the steering actuator 51. In the vehicle 90 in which the steering manipulation system 50 is constituted by the front wheel steering device and the rear wheel steering device, the tire angle of the front wheels 60F and the tire angle of the rear wheels 60R can be changed independently.

[0025] The drive system 30 can also be provided with a drive control device constituted by a processing circuit that controls the drive system 30. The braking system 40 can also be provided with a braking control device constituted by a processing circuit that controls the braking system 40. The steering manipulation system 50 can also be provided with a steering manipulation control device constituted by a processing circuit that controls the steering manipulation system 50. The processing circuit includes, for example, a memory that stores a program, and a CPU that executes various processes in accordance with the program in the memory. The drive control device, the braking control device, and the steering manipulation control device can receive the command value generated by the command value generation section 14 described later.

[0026] <Forward-backward force>

[0027] The forward-backward force is explained. The forward-backward force indicates a force acting in the forward-backward direction of the vehicle 90. The forward-backward force indicates a force in the direction in which the vehicle 90 accelerates when the value is positive. On the other hand, the forward-backward force indicates a force in the direction in which the vehicle 90 decelerates when the value is negative. The farther the value of the forward-backward force is from "0", the greater the force acting on the vehicle 90 is indicated. That is, the greater the magnitude of the forward-backward force, the greater the force acting on the vehicle 90 is indicated. The drive actuator 31 and the braking actuator 41 are actuators that generate the forward-backward force. The sum of the drive force and the braking force corresponds to the forward-backward force. The drive actuator 31 and the braking actuator 41 are collectively referred to as a forward-backward force actuator.

[0028] <Lateral force>

[0029] A lateral force is described. The lateral force indicates a force acting in a lateral direction of the vehicle 90. The lateral force is generated at each wheel according to a tire angle of the vehicle 90 in a turn. The steering actuator 51 is an actuator that generates the lateral force. The lateral force indicates a force in a left direction when the value is positive. On the other hand, the lateral force indicates a force in a right direction when the value is negative. The more the value of the lateral force deviates from "0", the greater the force acting on the wheel. That is, the greater the magnitude of the lateral force, the greater the force acting on the wheel.

[0030] <Vehicle behavior control>

[0031] The vehicle 90 can also have a function of controlling a behavior of the vehicle 90. For example, the vehicle behavior control function can be implemented by at least one of the drive system 30, the brake system 40, and the steering manipulation system 50. That is, the vehicle behavior control function can be implemented by a processing circuit included in the vehicle 90. The vehicle behavior control function is implemented, for example, by a CPU executing a program stored in a memory of the processing circuit. One example of the vehicle behavior control function is a side slip prevention function. In addition to this, the vehicle behavior control function can include functions of performing an anti-lock brake control, a traction control, an electric power steering control, a rear wheel steering manipulation control, and a direct yaw moment control.

[0032] The side slip prevention function is a function of suppressing a side slip of the vehicle 90 by reducing a slip amount of a wheel when the vehicle 90 turns. Specifically, in the side slip prevention function, a front-rear force acting on each wheel is adjusted by adjusting at least one of a drive force and a brake force independently for each wheel. For example, in the side slip prevention function, a mechanism that can adjust the front-rear force generated by the front-rear force actuator independently for each wheel is used. If an abnormality occurs in such a mechanism, there is a case where the side slip prevention function fails. The "failure of the side slip prevention function" can also be said to be an "abnormality of a front-rear force adjustment system (the drive system 30 and the brake system 40) that performs a side slip suppression control".

[0033] The anti-lock brake control is a control of suppressing a lock of a wheel by reducing a slip amount of the wheel through adjustment of a brake force when the vehicle 90 is braked. The traction control is a control of suppressing a spin of a drive wheel in the wheel by suppressing an acceleration slip of the drive wheel.

[0034] The electric power steering control is a control of assisting an operator of a steering manipulation operating member in the vehicle 90. The rear wheel steering manipulation control is a control of adjusting a tire angle of the rear wheel 60R by operating a rear wheel steering device. The direct yaw moment control is a control of controlling a yaw moment of the vehicle 90 by causing a difference in a front-rear force between left and right wheels through control of at least one of a brake force and a drive force.

[0035] <Information acquisition device>

[0036] The vehicle 90 can also be provided with the information acquisition device 80.

[0037] The information acquisition device 80 is a device for acquiring information of the surroundings of the vehicle 90. The information acquisition device 80 can acquire the relative distance of the vehicle 90 from other vehicles and obstacles and the like located in the surroundings of the vehicle 90. The information acquisition device 80 can also acquire the shape of the road on which the vehicle 90 is traveling, or recognize the lane. One example of the information acquisition device 80 is a camera. One example of the information acquisition device 80 is a detection device such as a LiDAR and a millimeter wave radar.

[0038] As another example of the information acquisition device 80, there is a GNSS receiver that receives a signal from a positioning satellite. Based on the signal received by the GNSS receiver, the current position of the vehicle 90 can be determined.

[0039] The information acquisition device 80 can be constituted by one of the above-described devices, or can be constituted by two or more devices in combination. The information acquisition device 80 can also be provided with a processing circuit that processes the acquired information.

[0040] 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 support device 20.

[0041] The information acquisition device 80 can not necessarily be mounted on the vehicle 90. If the vehicle 90 is provided with a device that receives a signal from the information acquisition device 80 provided on the outside of the vehicle 90, the control device 10 and the driving support device 20 can use the information of the surroundings of the vehicle 90.

[0042] <Driving support device>

[0043] The driving support device 20 is constituted by a processing circuit that can set a travel path for automatically driving the vehicle 90. The driving support device 20 sets the travel path, for example, based on the information obtained by the information acquisition device 80. The driving support device 20 can output a request for driving the vehicle 90 in accordance with the travel path as a travel request.

[0044] The travel request includes, for example, a target value of the yaw rate, a target value of the front-rear acceleration. The travel request can also include a target position of the vehicle 90, a target value of the vehicle speed, and the like. The travel request can also include a priority degree indicating which one of the braking of the vehicle 90 and the turning of the vehicle 90 is prioritized. For example, in the case of a braking priority degree of 50% and a turning priority degree of 50%, neither the braking nor the turning is prioritized. For example, in the case of a braking priority degree of 60% and a turning priority degree of 40%, the braking is prioritized. For example, in the case of a braking priority degree of 70% and a turning priority degree of 30%, the braking is further prioritized compared to the example of the braking priority degree of 60%.

[0045] <Various Sensors>

[0046] The vehicle 90 is equipped with various sensors. In the Figure 1 , as one example of the various sensors, a yaw rate sensor SE1, an acceleration sensor SE2, and a wheel speed sensor SE3 are shown. The detection signals from the various sensors are input to the control device 10.

[0047] The yaw rate sensor SE1 is a sensor that detects the yaw rate of the vehicle 90.

[0048] The acceleration sensor SE2 is constituted by a front-rear acceleration sensor that detects the acceleration in the front-rear direction of the vehicle 90, and a lateral acceleration sensor that detects the acceleration in the lateral direction of the vehicle 90.

[0049] The wheel speed sensor SE3 is a sensor that detects the wheel rotational speed. The wheel speed sensor SE3 is provided to each wheel.

[0050] <Control Device>

[0051] The control device 10 is constituted by a processing circuit that controls the drive system 30, the brake system 40, and the steering manipulation system 50. The control device 10 is equipped with a CPU and a ROM. Various programs for the CPU to execute various controls are stored in the ROM of the control device 10.

[0052] The control device 10 is connected to the drive control device, the brake control device, and the steering manipulation control device. Information can be transmitted and received between the control device 10 and the drive control device, the brake control device, and the steering manipulation control device.

[0053] The control device 10 is constituted by a plurality of functional sections that execute various controls. In the Figure 1 , as one example of the functional sections, a state quantity calculation section 11, a control request generation section 12, a wheel request generation section 13, and an instruction value generation section 14 are shown. The respective functional sections equipped in the control device 10 can transmit and receive information to and from each other.

[0054] <State quantity calculation section>

[0055] The state quantity calculation section 11 calculates vehicle state quantities.

[0056] Hereinafter, a suffix added to the end of a symbol representing a variety of state quantities indicates which wheel of the vehicle 90 the symbol representing the state quantity corresponds to. Specifically, the suffixes "fl", "fr", "rl", and "rr" correspond to the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, respectively. In addition, the suffix "**" indicates that the symbol representing the state quantity is a general term corresponding to all the wheels. The suffix "f*" indicates that the symbol representing the state quantity is a general term corresponding to the two front wheels 60F. The suffix "r*" indicates that the symbol representing the state quantity is a general term corresponding to the two rear wheels 60R.

[0057] The vehicle state quantities calculated by the state quantity calculation section 11 are exemplified.

[0058] The state quantity calculation section 11 can calculate the yaw rate γ on the basis of a detection signal from the yaw rate sensor SE1.

[0059] The state quantity calculation section 11 can calculate the front-rear acceleration Gx and the lateral acceleration Gy on the basis of a detection signal from the acceleration sensor SE2.

[0060] The state quantity calculation section 11 can calculate the wheel rotational speed Vw** of each wheel on the basis of a detection signal from the wheel speed sensor SE3. The state quantity calculation section 11 can calculate the vehicle body speed Vx on the basis of the wheel rotational speeds Vw** of the plurality of wheels. The vehicle body speed Vx indicates the running speed of the vehicle 90.

[0061] The state quantity calculation section 11 can also calculate the front-rear force and the lateral force acting on each wheel, respectively. With respect to the lateral force, for example, the total of the lateral forces acting on all the wheels can be calculated on the basis of the weight m of the vehicle 90, the center of gravity height of the vehicle 90, the lateral acceleration Gy, and the like. The state quantity calculation section 11 can calculate the lateral force acting on each wheel from the total value of the lateral forces, taking into account the distribution ratio to each wheel.

[0062] The state quantity calculation section 11 can calculate the road surface friction coefficient μ** of each wheel. For example, the road surface friction coefficient μ** can be calculated on the basis of the lateral acceleration Gy.

[0063] The state quantity calculation section 11 can calculate the ground contact load w** of each wheel. For example, the ground contact load w** can be calculated on the basis of the weight m of the vehicle 90, the front-rear acceleration Gx, the lateral acceleration Gy, and the like.

[0064] <Requirement generation section>

[0065] The control demand generating portion 12 generates a demand for the vehicle 90, that is, a vehicle demand, based on the demand input from the driving support device 20. The control demand generating portion 12, for example, calculates a demand value of a front-rear force in the vehicle 90, that is, a vehicle front-rear force demand value Fx. The control demand generating portion 12, for example, calculates a demand value of a moment for the vehicle 90, that is, a demand moment Mz. The demand moment Mz can be expressed by the product of the yaw inertia moment and the time differential value of the yaw rate. The control demand generating portion 12 can also calculate a demand value of a lateral force in the vehicle 90, that is, a vehicle lateral force demand value Fy.

[0066] The wheel demand generating portion 13 executes a wheel demand generating process. In the wheel demand generating process, a demand for each wheel, that is, a wheel demand, is generated based on the vehicle demand. For example, the wheel demand generating portion 13 calculates a demand value of a front-rear force acting on each wheel, that is, each wheel front-rear force demand value Fx**, by distributing the vehicle front-rear force demand value Fx to each wheel. The wheel demand generating portion 13 calculates a demand value of a lateral force acting on each wheel, that is, each wheel lateral force demand value Fy**, by distributing the demand moment Mz to each wheel. The wheel lateral force demand value Fy** can also be calculated based on the vehicle lateral force demand value Fy. In addition, although described in detail later, the wheel demand generating portion 13 can also correct the vehicle demand when generating the wheel demand.

[0067] <Indication value generating portion>

[0068] The indication value generating portion 14 generates an indication value for operating the actuator based on the wheel demand. Specifically, the indication value generating portion 14 calculates an indication value for controlling the drive actuator 31 and an indication value for controlling the brake actuator 41 based on each wheel front-rear force demand value Fx**. The indication value generating portion 14 calculates an indication value for controlling the steering actuator 51 based on each wheel lateral force demand value Fy**.

[0069] The indication value generating portion 14 can output each calculated indication value. Each indication value is input to the corresponding system in the drive system 30, the brake system 40, and the steering manipulation system 50. The drive system 30, the brake system 40, and the steering manipulation system 50 operate the respective actuators based on each indication value. For example, in the brake system 40 that has received the indication value, the brake control device operates the brake actuator 41 according to the indication value.

[0070] <Indication value generating process>

[0071] The control device 10 executes an indication value generating process for performing the support control of the vehicle 90. Hereinafter, the process is described using Figure 2 and Figure 3 The control device 10 has a ROM in which the programs for executing Figure 2 and Figure 3The program of the processing shown, that is, the vehicle control program. Figure 2 and Figure 3 The processing shown is realized by the CPU executing the vehicle control program stored in the ROM.

[0072] Figure 2 The flow of the processing executed by the control device 10 is shown. This processing program is repeatedly executed at a prescribed period in the execution of the support control.

[0073] If the present processing program is started, first, in step S101, the control device 10 acquires the travel request output by the driving support device 20. For example, the control device 10 acquires the target value of the yaw rate, the target value of the front-rear acceleration, and the priority degree. Thereafter, the control device 10 causes the processing to proceed to step S102.

[0074] In step S102, the control device 10 causes the state quantity calculation section 11 to calculate the vehicle state quantity. Thereafter, the control device 10 causes the processing to proceed to step S103.

[0075] In step S103, the control device 10 causes the control request generation section 12 to generate the vehicle request. For example, the control request generation section 12 calculates the vehicle front-rear force request value Fx and the request torque Mz. Thereafter, the control device 10 causes the processing to proceed to step S104.

[0076] In step S104, the control device 10 causes the wheel request to be generated by causing the wheel request generation section 13 to execute the wheel request generation processing. The wheel request generation section 13 calculates the front-rear force request value Fx** of each wheel and the lateral force request value Fy** of each wheel. The details of the wheel request generation processing will be described later. Thereafter, the control device 10 causes the processing to proceed to step S105.

[0077] In step S105, the control device 10 causes the indication value generation section 14 to generate the indication value. If the indication value is generated, the indication value generation section 14 outputs the indication value to the processing circuit of each system. As a result thereof, in each system, the actuator operates in accordance with the indication value. In this way, the vehicle 90 travels in accordance with the travel request. If the indication value generation section 14 is caused to generate the indication value, the control device 10 ends the present processing program.

[0078] <Wheel request generation processing>

[0079] Figure 3 The flow of the processing executed by the wheel request generation section 13 is shown. This processing program is executed by the processing of step S104 shown. Figure 2 The processing of step S104 shown executes the present processing program.

[0080] If the process is started, first, in step S201, the wheel request generation portion 13 calculates the wheel lateral force request value Fy**. For example, the wheel request generation portion 13 calculates the wheel lateral force request value Fy** by distributing the required moment Mz to each wheel. One example of the distribution ratio is a prescribed value. The distribution ratio can also be changed according to the execution state of the control related to the lateral force of each wheel, such as electric power steering control, rear wheel steering control, and direct yaw moment control. If the wheel request generation portion 13 calculates the wheel lateral force request value Fy**, the process moves to step S202.

[0081] In step S202, the wheel request generation portion 13 calculates the wheel fore-aft force request value Fx**. For example, the wheel request generation portion 13 calculates the wheel fore-aft force request value Fx** by distributing the vehicle fore-aft force request value Fx to each wheel. One example of the distribution ratio is a prescribed value. The distribution ratio can also be changed according to the execution state of the control related to the fore-aft force of each wheel, such as the anti-skid function. Here, for example, in the case where the anti-skid function is disabled, the above distribution ratio becomes a prescribed value. If the wheel request generation portion 13 calculates the wheel fore-aft force request value Fx**, the process moves to step S203.

[0082] In step S203, and step S204 following step S203, the wheel request generation portion 13 acquires information related to the running situation of the vehicle 90.

[0083] In step S203, for example, the wheel request generation portion 13 determines whether the running situation of the vehicle 90 is the over-steering state and whether it is the under-steering state, based on the state quantity of the vehicle 90. Hereinafter, the over-steering state is also referred to as the OS state. The under-steering state is also referred to as the US state.

[0084] Using Figure 4 An example of a method for determining whether the running situation of the vehicle 90 is in the OS state and whether it is in the US state will be described. Figure 4 The solid line shown in the figure shows the relationship between the front wheel tire angle δf and the yaw rate γ in the case where the running situation of the vehicle 90 is stable. Figure 4 The dot-and-dash line shown in the figure shows the OS threshold value OSth. The OS threshold value OSth is a value that is set so that the running situation of the vehicle 90 is in the OS state when the front wheel tire angle δf and the yaw rate γ are equal to or greater than the OS threshold value OSth. Figure 4 The threshold value after the solid line is offset. The OS threshold value OSth is a value that is set so that the running situation of the vehicle 90 is in the OS state when the front wheel tire angle δf and the yaw rate γ are equal to or greater than the OS threshold value OSth. Figure 4 The double dot-and-dash line shown in the figure shows the US threshold value USth. The US threshold value USth is a value that is set so that the running situation of the vehicle 90 is in the US state when the front wheel tire angle δf and the yaw rate γ are equal to or less than the US threshold value USth. Figure 4The solid line shown represents the offset threshold. Compared to the relationship shown by the solid line, the US threshold USth corresponds to a smaller yaw rate γ corresponding to the front tire angle δf. The relationships shown by the solid line, the dashed line, and the double-dashed line are determined in advance through experiments, etc. The relationship between the OS threshold OSth shown by the dashed line and the solid line example may be modified depending on the state of the traveling vehicle 90. For example, a modification may be considered based on the priority level included in the driving request. Similarly, the relationship between the US threshold USth shown by the double-dashed line and the solid line example may be modified.

[0085] express Figure 4 A calculation map of the relationship illustrated is stored in, for example, the control device 10. Based on this calculation map, the wheel requirement generating unit 13 determines that the vehicle is in the OS state when the yaw rate γ relative to the calculated front wheel tire angle δf is greater than the OS threshold value OSth. In other words, when the yaw rate γ relative to the front wheel tire angle δf is greater than the OS threshold value OSth, the vehicle state quantity indicates that the vehicle 90 is in the OS state. Based on this calculation map, the wheel requirement generating unit 13 determines that the vehicle is in the US state when the yaw rate γ relative to the calculated front wheel tire angle δf is less than the US threshold value USth. In other words, when the yaw rate γ relative to the front wheel tire angle δf is less than the US threshold value USth, the vehicle state quantity indicates that the vehicle 90 is in the US state.

[0086] Furthermore, if the anti-skid function is activated, the vehicle 90 is controlled in a direction to suppress the behavior such as the OS state or the US state. Therefore, when the yaw rate γ relative to the front wheel tire angle δf exceeds the above-mentioned OS threshold value OSth or US threshold value USth, the anti-skid function may fail. Figure 4 The calculation map of the relationship shown as an example can determine whether the anti-skid function has failed.

[0087] Return to Figure 3 If the wheel request generation unit 13 completes step S203, the process proceeds to step S204. In step S204, the wheel request generation unit 13 obtains the wheel slip state. For example, the wheel request generation unit 13 determines whether the wheel is in a large slip state. A large slip state refers to a state in which the wheel slip amount is excessive.

[0088] use Figure 5 , an example of a method for determining whether or not a large slip state is present will be described. Figure 5 The solid line shown is an example of the temporal transition of the vehicle longitudinal force request value Fx. Figure 5The dotted line shown indicates a large slip threshold value SLth. The large slip threshold value SLth is a threshold value after the solid line is shifted in the direction of time passage. This shift amount can be calculated in advance through experiments or the like. This shift amount can also be changed according to the state of the vehicle 90 in running. For example, it is considered to be changed according to the priority level included in the running request. Figure 5 The dashed line shown illustrates the vehicle fore-aft force estimated from the actual fore-aft acceleration Gx of the vehicle 90. In the example shown, the dashed line develops in a direction in which the vehicle fore-aft force decreases from the vehicle fore-aft force request value Fx shown by the solid line as time passes. If the estimated vehicle fore-aft force like that shown by the dashed line is smaller than the large slip threshold value SLth, the wheel request generation portion 13 can determine that the large slip state is present. In other words, if the vehicle fore-aft force estimated from the actual fore-aft acceleration Gx greatly departs from the vehicle fore-aft force request value Fx, the wheel request generation portion 13 can determine that the large slip state is present. Figure 5 In the example shown, the dashed line develops in a direction in which the vehicle fore-aft force decreases from the vehicle fore-aft force request value Fx shown by the solid line as time passes. If the estimated vehicle fore-aft force like that shown by the dashed line is smaller than the large slip threshold value SLth, the wheel request generation portion 13 can determine that the large slip state is present. In other words, if the vehicle fore-aft force estimated from the actual fore-aft acceleration Gx greatly departs from the vehicle fore-aft force request value Fx, the wheel request generation portion 13 can determine that the large slip state is present.

[0089] Returning to Figure 3 , if the information related to the running situation of the vehicle 90 is acquired in step S203 and step S204, the wheel request generation portion 13 causes the process to proceed to step S205.

[0090] In step S205, the wheel request generation portion 13 causes the process to proceed to step S206 if the running situation of the vehicle 90 is the OS state (S205: YES).

[0091] In step S206, the wheel request generation portion 13 limits the front wheel lateral force request value Fyf* based on the rear wheel lateral force limit value. As one example, the wheel request generation portion 13 limits the front wheel lateral force request value Fyf* to a size equal to or smaller than the first lateral force limit value Ly1. The first lateral force limit value Ly1 can be calculated as follows, for example.

[0092] First, the rear wheel lateral force limit value will be described. The rear wheel lateral force limit value is a limit value of the lateral force that can act on the rear wheel 60R. With respect to each wheel, the limit value of the fore-aft force and the limit value of the lateral force can be calculated based on the equation of a friction circle. The size of the friction circle is determined by the product of the road surface friction coefficient μ** and the ground contact load w**. The front wheel fore-aft force limit value corresponds to the maximum value of the size of the fore-aft force within a range in which the resultant of the fore-aft force and the lateral force does not exceed the friction circle. The front wheel lateral force limit value corresponds to the maximum value of the size of the lateral force within a range in which the resultant of the fore-aft force and the lateral force does not exceed the friction circle. The front wheel fore-aft force limit value can be expressed by the following relational expression (Expression 1). The front wheel lateral force limit value can be expressed by the following relational expression (Expression 2).

[0093]

[0094]

[0095] For example, the front-left-wheel front-and-rear force limit value |Fxfllim| can be calculated based on the above-described relational expression (Formula 1) using the road surface friction coefficient μfl, the ground contact load wfl, and the left-front-wheel lateral force request value Fyfl.

[0096] The wheel request generation portion 13 can calculate the first lateral force limit value Ly1 based on the following relational expression (Formula 3) and according to the rear-wheel lateral force limit value |Fyr*lim|.

[0097] Ly1 = lf / lr |Fyr*lim|... (Formula 3)

[0098] Ly2 = |Fyf*lim|... (Formula 4)

[0099] The rear-wheel lateral force limit value |Fyr*lim| in the above-described relational expression (Formula 3) can be calculated based on the above-described relational expression (Formula 2). In the above-described relational expression (Formula 3), "lf" denotes a front-axle track. The front-axle track is a horizontal distance between a vehicle center of gravity in the front-and-rear direction of the vehicle 90 and an axle on which the front wheel 60F is installed. "lr" denotes a rear-axle track. The rear-axle track is a horizontal distance between the vehicle center of gravity in the front-and-rear direction of the vehicle 90 and an axle on which the rear wheel 60R is installed. The sum of the front-axle track and the rear-axle track corresponds to a wheelbase of the vehicle 90.

[0100] That is, in step S206, the wheel request generation portion 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|. Also, in a case where 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 request generation portion 13 corrects the front-wheel lateral force request value Fyf*. That is, in this case, the wheel request generation portion 13 corrects the front-wheel lateral force request value Fyf* so that the magnitude of the front-wheel lateral force request value Fyf* becomes equal to or less than the first lateral force limit value Ly1. One 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 wheel 60F is adjusted according to an indication value calculated based on the front-wheel lateral force request value Fyf*. If the wheel request generation portion 13 limits the front-wheel lateral force request value Fyf*, the processing moves to step S207.

[0101] In step S207, the wheel request generation portion 13 limits the vehicle front-and-rear force request value Fx to limit the front-and-rear force of the outer rear wheel in a turn. Here, the outer rear wheel in a turn corresponds to the rear wheel 60R that is located on the outer side when viewed from a turning center of the vehicle 90 that is making a turn. For example, in a case where the vehicle 90 that is advancing makes a turn clockwise, the left rear wheel is the outer rear wheel in a turn.

[0102] As one example, the wheel request generation portion 13 reduces the magnitude of the vehicle longitudinal force request value Fx so that the longitudinal force acting on the outer rear wheel during turning becomes a magnitude equal to or less than the first longitudinal force limit value Lx1. The wheel request generation portion 13 sets the rear wheel longitudinal force limit value |Fxr*lim| as the first longitudinal force limit value Lx1 as represented by the following relational expression (Expression 5).

[0103] Lx1 = |Fxr*lim|... (Expression 5)

[0104] Lx2 = |Fxf*lim|... (Expression 6)

[0105] Lx3 = min{|Fx**lim|}... (Expression 7)

[0106] That is, in step S207, the wheel request generation portion 13 calculates the rear wheel longitudinal force limit value |Fxr*lim| and sets the rear wheel longitudinal force limit value |Fxr*lim| as the first longitudinal force limit value Lx1. Then, the wheel request generation portion 13 reduces the magnitude of the vehicle longitudinal force request value Fx so that the longitudinal force request value of the outer rear wheel during turning is calculated as a value equal to or less than the first longitudinal force limit value Lx1, taking into account the distribution ratio to each wheel explained in the process of step S202. For example, in the case where the magnitude of the longitudinal force request value of the outer rear wheel during turning is greater than the first longitudinal force limit value Lx1, the magnitude of the vehicle longitudinal force request value Fx is reduced so that the magnitude of the longitudinal force request value of the outer rear wheel during turning becomes equal to or less than the first longitudinal force limit value Lx1. For example, the magnitude of the vehicle longitudinal force request value Fx is reduced so that the magnitude of the longitudinal force request value of the outer rear wheel during turning becomes equal to the first longitudinal force limit value Lx1. Also, here, the wheel request generation portion 13 reduces the magnitude while maintaining the positive or negative of the vehicle longitudinal force request value Fx.

[0107] If the vehicle longitudinal force request value Fx is limited in step S207, the wheel request generation portion 13 moves the process to step S213.

[0108] On the other hand, in the case where the running situation of the vehicle 90 is not the OS state in the process of step S205 (S205: No), the wheel request generation portion 13 moves the process to step S208. In the case where the running situation of the vehicle 90 is the US state (S208: Yes), the wheel request generation portion 13 moves the process to step S209.

[0109] In step S209, the wheel demand generation portion 13 limits the front wheel lateral force demand value Fyf* based on the front wheel lateral force limit value |Fyf*lim|. As one example, the wheel demand generation portion 13 limits the front wheel lateral force demand value Fyf* to a magnitude that is 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-described relational expression (Equation 2). The wheel demand generation portion 13 sets the front wheel lateral force limit value |Fyf*lim| to the second lateral force limit value Ly2 as expressed by the above-described relational expression (Equation 4).

[0110] That is, in step S209, the wheel demand generation portion 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. Also, in the case where the magnitude of the front wheel lateral force demand value Fyf* calculated by the wheel demand generation portion 13 in step S201 is greater than the second lateral force limit value Ly2, the wheel demand generation portion 13 corrects the front wheel lateral force demand value Fyf*. That is, in this case, the wheel demand generation portion 13 corrects the front wheel lateral force demand value Fyf* so that the magnitude of the front wheel lateral force demand value Fyf* becomes equal to or less than the second lateral force limit value Ly2. One example of the corrected front wheel lateral force demand value Fyf* is a value that is equal to the second lateral force limit value Ly2. As a result of this, the tire angle of the front wheel 60F is adjusted in accordance with the indication value calculated based on the front wheel lateral force demand value Fyf*. If the wheel demand generation portion 13 limits the front wheel lateral force demand value Fyf*, the processing moves to step S210.

[0111] In step S210, the wheel demand generation portion 13 limits the vehicle fore-aft force demand value Fx to limit the fore-aft force of the outer front wheel in a turn. Here, the outer front wheel in a turn corresponds to the front wheel 60F that is located on the outer side when viewed from the center of the turn of the vehicle 90 that is making a turn. For example, in the case where the vehicle 90 is making a turn in a clockwise direction, the left front wheel is the outer front wheel in a turn.

[0112] As one example, the wheel demand generation portion 13 reduces the magnitude of the vehicle fore-aft force demand value Fx so that the fore-aft force acting on the outer front wheel in a turn becomes a magnitude that is equal to or less than the second fore-aft force limit value Lx2. The wheel demand generation portion 13 sets the front wheel fore-aft force limit value |Fxf*lim| to the second fore-aft force limit value Lx2 as expressed by the above-described relational expression (Equation 6).

[0113] That is, in step S210, the wheel demand generation portion 13 calculates the front wheel front-rear force limit value |Fxf*lim| and sets the front wheel front-rear force limit value |Fxf*lim| as the second front-rear force limit value Lx2. Then, the wheel demand generation portion 13 reduces the magnitude of the vehicle front-rear force demand value Fx considering the distribution ratio to each wheel explained in the process of step S202 so as to calculate the corner outer front wheel front-rear force demand value to be a value equal to or less than the second front-rear force limit value Lx2. For example, in the case where the magnitude of the corner outer front wheel front-rear force demand value is larger than the second front-rear force limit value Lx2, the magnitude of the vehicle front-rear force demand value Fx is reduced so that the magnitude of the corner outer front wheel front-rear force demand value becomes equal to or less than the second front-rear force limit value Lx2. For example, the magnitude of the vehicle front-rear force demand value Fx is reduced to be equal to the second front-rear force limit value Lx2. Further, here the wheel demand generation portion 13 maintains the sign of the vehicle front-rear force demand value Fx to reduce the magnitude.

[0114] If the vehicle front-rear force demand value Fx is limited in step S210, the wheel demand generation portion 13 moves the process to step S213.

[0115] On the other hand, in the case where the running situation of the vehicle 90 is not the US state in the process of step S208 (S208: No), the wheel demand generation portion 13 moves the process to step S211. In the case where the running situation of the vehicle 90 is not the large slip state (S211: No), the wheel demand generation portion 13 ends the present processing routine. In the case where the running situation of the vehicle 90 is the large slip state (S211: Yes), the wheel demand generation portion 13 moves the process to step S212.

[0116] In step S212, the wheel demand generation portion 13 limits the vehicle front-rear force demand value Fx based on each wheel front-rear force limit value. As one example, the wheel demand generation portion 13 limits the vehicle front-rear force demand value Fx so that each wheel front-rear force demand value Fx** becomes a magnitude equal to or less than the third front-rear force limit value Lx3. The wheel demand generation portion 13 sets the third front-rear force limit value Lx3 as expressed by the above relational expression (Expression 7). The "min" in the relational expression (Expression 7) is a function that returns the smaller value of any one of the arguments. That is, the smallest value of each wheel front-rear force limit value |Fx**lim| is the third front-rear force limit value Lx3.

[0117] That is, in step S212, the wheel demand generation portion 13 calculates each wheel front-rear force limit value |Fx**lim| and sets the smallest value among the wheel front-rear force limit values |Fx**lim| as the third front-rear force limit value Lx3. Then, the wheel demand generation portion 13 reduces the magnitude of the vehicle front-rear force demand value Fx so that all of the wheel front-rear force demand values Fx** become equal to or less than the third front-rear force limit value Lx3. For example, the magnitude of the vehicle front-rear force demand value Fx is reduced so that the magnitude of the largest demand value among the wheel front-rear force demand values Fx** becomes equal to the third front-rear force limit value Lx3. Further, here the wheel demand generation portion 13 maintains the positive and negative of the vehicle front-rear force demand value Fx to reduce the magnitude.

[0118] If the vehicle front-rear force demand value Fx is limited in step S212, the wheel demand generation portion 13 causes the process to proceed to step S213.

[0119] In step S213, the wheel demand generation portion 13 performs counting of the duration T. For example, in the case where the process is moved from step S207, the wheel demand generation portion 13 counts the duration T as the time during which the OS state continues. If the OS state is eliminated, the wheel demand generation portion 13 initializes the duration T to "0". For example, in the case where the process is moved from step S210, the wheel demand generation portion 13 counts the duration T as the time during which the US state continues. If the US state is eliminated, the wheel demand generation portion 13 initializes the duration T to "0". For example, in the case where the process is moved from step S212, the wheel demand generation portion 13 counts the duration T as the time during which the large slip state continues. If the large slip state is eliminated, the wheel demand generation portion 13 initializes the duration T to "0". If the wheel demand generation portion 13 performs counting of the duration T, the wheel demand generation portion 13 causes the process to proceed to step S214.

[0120] In step S214, the wheel demand generation portion 13 determines whether the duration T is longer than a specified time Tth. In the case where the duration T is equal to or less than the specified time Tth (S214: No), the wheel demand generation portion 13 ends the present processing routine. On the other hand, in the case where the duration T is longer than the specified time Tth (S214: Yes), the wheel demand generation portion 13 causes the process to proceed to step S215.

[0121] The specified time Tth will be described. The specified time Tth is a threshold value for determining whether the time during which the OS state, the US state, or the large slip state does not cancel out and continues is long. For example, the specified time Tth is set to a value calculated in advance through experiments or the like as an initial value. The wheel request generation portion 13 can increase or decrease the specified time Tth. For example, the wheel request generation portion 13 can increase or decrease the specified time Tth based on which of braking of the vehicle 90 and turning of the vehicle 90 is prioritized, which is included in the travel request input from the drive assist device 20. As one example, the wheel request generation portion 13 lengthens the specified time Tth in the case where braking is prioritized compared to the case where turning is prioritized. The amount by which the specified time Tth is lengthened can also be changed according to the degree of priority of braking. For example, the specified time Tth can be further lengthened in the case where the degree of priority of braking is 70% compared to the case where the degree of priority of braking is 60%.

[0122] In step S215, the wheel request generation portion 13 further reduces the magnitude of the vehicle fore-aft force request value Fx. That is, the wheel request generation portion 13 reduces the magnitude of the vehicle fore-aft force request value Fx in the case where the duration T is longer than the specified time Tth compared to the case where the duration T is the specified time Tth or less. Thereafter, the wheel request generation portion 13 ends the present processing routine.

[0123] In the present embodiment, the control device 10 implements processing of reflecting the vehicle fore-aft force request value Fx whose magnitude has been reduced in the above steps S207, S210, S212, and S215 in the following manner. Here, adjustment of the fore-aft force based on the reduction in the magnitude of the vehicle fore-aft force request value Fx is achieved by reducing the braking force generated by the brake actuator 41. Further, because the magnitude of the vehicle fore-aft force request value Fx as a vehicle request is reduced, the total of the braking forces imparted to the wheels is reduced. As a method of reducing the braking force like this, it is possible to cite reducing the braking force with all of the wheels as targets. Specifically, it is possible to cite reducing the braking force imparted to the vehicle 90 by implementing regenerative coordination control.

[0124] <Effects>

[0125] The effects of the present embodiment will be described.

[0126] According to the control device 10, in a case where the vehicle state quantity indicates that the running state of the vehicle 90 is the OS state in the event of failure of the anti-skid function (S205: YES), the magnitude of the front wheel lateral force demand value Fyf* is limited (S206). The tire angle of the front wheel 60F is controlled on the basis of this front wheel lateral force demand value Fyf*. A first lateral force limit value Ly1 that limits the magnitude of the front wheel lateral force demand value Fyf* is a limit value of the lateral force that can act on the rear wheel 60R in running. Therefore, the rear wheel 60R of the vehicle 90 in the OS state can be used as a reference to limit the lateral force that acts on the front wheel 60F of the vehicle 90 in the OS state. By adjusting the tire angle of the front wheel 60F in accordance with the front wheel lateral force demand value Fyf* that is limited as described above, the difference between the lateral force of the front wheel 60F and the lateral force of the rear wheel 60R in the vehicle 90 in a turn can be reduced. Thus, the OS state can be suppressed, and the running state of the vehicle 90 can be stabilized.

[0127] According to the control device 10, in a case where the vehicle state quantity indicates that the running state of the vehicle 90 is the OS state in the event of failure of the anti-skid function (S205: YES), the magnitude of the front wheel lateral force demand value Fyf* is limited (S206). The tire angle of the front wheel 60F is controlled on the basis of this front wheel lateral force demand value Fyf*. A first lateral force limit value Ly1 that limits the magnitude of the front wheel lateral force demand value Fyf* is a limit value of the lateral force that can act on the rear wheel 60R in running. Therefore, the rear wheel 60R of the vehicle 90 in the OS state can be used as a reference to limit the lateral force that acts on the front wheel 60F of the vehicle 90 in the OS state. By adjusting the tire angle of the front wheel 60F in accordance with the front wheel lateral force demand value Fyf* that is limited as described above, the difference between the lateral force of the front wheel 60F and the lateral force of the rear wheel 60R in the vehicle 90 in a turn can be reduced. Thus, the OS state can be suppressed, and the running state of the vehicle 90 can be stabilized.

[0128] According to the control device 10, in a case where the vehicle state quantity indicates that the running state of the vehicle 90 is the OS state in the event of failure of the anti-skid function (S205: YES), the magnitude of the front wheel lateral force demand value Fyf* is limited (S206). The tire angle of the front wheel 60F is controlled on the basis of this front wheel lateral force demand value Fyf*. A first lateral force limit value Ly1 that limits the magnitude of the front wheel lateral force demand value Fyf* is a limit value of the lateral force that can act on the rear wheel 60R in running. Therefore, the rear wheel 60R of the vehicle 90 in the OS state can be used as a reference to limit the lateral force that acts on the front wheel 60F of the vehicle 90 in the OS state. By adjusting the tire angle of the front wheel 60F in accordance with the front wheel lateral force demand value Fyf* that is limited as described above, the difference between the lateral force of the front wheel 60F and the lateral force of the rear wheel 60R in the vehicle 90 in a turn can be reduced. Thus, the OS state can be suppressed, and the running state of the vehicle 90 can be stabilized.

[0129] According to the control device 10, in a case where the vehicle state quantity indicates that the running state of the vehicle 90 is the US state in the event of failure of the anti-skid function (S208: YES), the magnitude of the front wheel lateral force demand value Fyf* is limited (S209). The tire angle of the front wheel 60F is controlled based on the front wheel lateral force demand value Fyf*. The second lateral force limit value Ly2, which is the limit value of the lateral force that can act on the front wheel 60F, is used to limit the magnitude of the front wheel lateral force demand value Fyf*. As a result, by causing a larger lateral force to act on the front wheel 60F within the range not exceeding the friction circle, the grip of the front wheel 60F can be ensured. Thus, the running state of the vehicle 90 can be stabilized against the US state.

[0130] According to the control device 10, the specified time Tth is extended in the priority braking case compared to the priority turning case based on the priority level included in the travel demand. As a result, as long as the duration T does not become longer, the processing of step S215 is not executed. That is, as long as the duration T does not become longer, the magnitude of the vehicle fore-aft force demand value Fx is not reduced. In other words, in the priority braking case, the magnitude of the vehicle fore-aft force demand value Fx is not easily reduced compared to the priority turning case. Thus, in the priority braking case, the period during which a larger braking force is imparted can be further extended.

[0131] According to the control device 10, in a case where the vehicle state quantity indicates that the running state of the vehicle 90 is the large slip state in the event of failure of the anti-skid function (S211: YES), the magnitude of the vehicle fore-aft force demand value Fx is limited (S212). Specifically, the fore-aft force acting on each wheel is limited to be equal to or less than the third fore-aft force limit value Lx3, that is, to be equal to or less than the smallest value among the wheel fore-aft force limit values |Fx**lim|. As a result, for the vehicle 90 in the large slip state, the fore-aft force can be caused to act on each wheel within the range not exceeding the friction circle. Thus, the running state of the vehicle 90 can be stabilized against the large slip state.

[0132] Further, according to the anti-skid function, the yaw moment in the direction in which the state in which the running state of the vehicle 90 is unstable, such as the OS state, the US state, and the large slip state, is eliminated can be generated. According to the control device 10, even in a case where the yaw moment in the direction in which such a state in which the running state of the vehicle 90 is unstable is eliminated cannot be expected to act on the vehicle 90, the unstable running state can be suppressed, and the running state of the vehicle 90 can be stabilized.

[0133] (Modified Example)

[0134] The present embodiment can be implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a range in which there is no technical contradiction.

[0135] • In the above-described embodiment, in the case where the magnitude of the vehicle fore-aft force demand value Fx is reduced, as the process of causing the vehicle fore-aft force demand value Fx to be reflected in the fore-aft force, reduction of the braking force generated by the braking actuator 41 is implemented. This is not limiting, and as long as the fore-aft force actuator can be controlled to reduce the magnitude of the fore-aft force, it is acceptable. For example, the driving force generated by the driving actuator 31 can be increased to cause the fore-aft force to approach "0".

[0136] • The processes of steps S213 to S215 illustrated above can be omitted in the above-described embodiment. Figure 3

[0137] • The processes of steps S211 and S212 illustrated above can be omitted in the above-described embodiment. Figure 3

[0138] • In the above-described embodiment, the processes of steps S206 and S207 are implemented in the case of the OS state. In the case of the OS state, as long as at least the process of limiting the front wheel lateral force demand value Fyf* based on the front wheel lateral force limit value is implemented, it is acceptable. That is, the process of step S207 can be omitted. Even in this case, it is possible to stabilize the running situation of the vehicle 90 by the OS state.

[0139] • In the above-described embodiment, the processes of steps S209 and S210 are implemented in the case of the US state. In the case of the US state, for example, if at least the process of limiting the vehicle fore-aft force demand value Fx to limit the fore-aft force of the outer front wheel in the turn is implemented, it is possible to stabilize the running situation of the vehicle 90. That is, the process of step S209 can be omitted. Further, for example, if at least the process of limiting the front wheel lateral force demand value Fyf* based on the front wheel lateral force limit value is implemented, it is possible to stabilize the running situation of the vehicle 90. That is, the process of step S210 can be omitted.

[0140] • In the above-described embodiment, the case where the vehicle 90 is made to advance is described. That is, in the above-described embodiment, the "front wheel 60F" is a wheel located on the front side with respect to the traveling direction of the vehicle 90. A wheel like this located on the front side with respect to the traveling direction is set as a "first wheel". Further, in the above-described embodiment, the "rear wheel 60R" is a wheel located on the rear side with respect to the traveling direction of the vehicle 90. A wheel like this located on the rear side with respect to the traveling direction is set as a "second wheel". The control of the above-described embodiment that takes the "front wheel 60F" as the target can be replaced by control that takes the "first wheel" as the target. The control of the above-described embodiment that takes the "rear wheel 60R" as the target can be replaced by control that takes the "second wheel" as the target.

[0141] ​​Here, a case where the vehicle 90 is made to travel backward is considered. In this case, the wheel located on the front side with respect to the traveling direction of the vehicle 90 is the wheel installed on the rear side of the vehicle 90, that is, the "rear wheel 60R". That is, the "rear wheel 60R" corresponds to the "first wheel". Also similarly, the wheel located on the rear side with respect to the traveling direction of the vehicle 90 is the wheel installed on the front side of the vehicle 90, that is, the "front wheel 60F". That is, the "front wheel 60F" corresponds to the "second wheel".

[0142] That is, when the support control in the above-described embodiment is applied in a case where the vehicle 90 is made to travel backward, the same effects as in a case where the vehicle 90 is made to travel forward can be exerted by performing the control targeting the "first wheel" and the control targeting the "second wheel".

[0143] • The control device 10, the drive control device, the brake control device, the steering control device, and the driving support device 20 as the processing circuit can have any one of the following [a] to [c].

[0144] [a] A circuit having one or more processors that execute various processes according to computer programs. The processor has a processing device. Examples of the processing device are a CPU, a DSP, a GPU, and the like. The processor has a memory. Examples of the memory are a RAM, a ROM, a flash memory, and the like. The memory stores program codes or instructions configured to cause the processing device to execute processes. The memory, that is, the computer-readable medium includes all available media that a general-purpose or special-purpose computer can access, which can be used.

[0145] [b] A circuit having one or more hardware circuits that execute various processes. Examples of the hardware circuit are an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), an FPGA (Field Programmable Gate Array), and the like.

[0146] [c] A circuit having a processor that executes part of various processes according to computer programs, and a hardware circuit that executes the remaining processes of the various processes.

[0147] • Part or all of the functions that the processing circuit of the drive control device, the brake control device, the steering control device, and the driving support device 20 can be implemented by the control device 10.

[0148] • Part of the functions that the control device 10 implements can be implemented by another processing circuit connected to the control device 10.

Claims

1. A vehicle control device configured to control the vehicle based on a request input from a driving support device that supports the vehicle's travel so as to automatically drive the vehicle, wherein: The above vehicle has: the aforementioned driving support device; Wheels, including front and rear wheels; driving the actuator and the brake actuator to generate a front-rear force, wherein the front-rear force refers to a force acting on the vehicle in a front-rear direction; as well as The steering actuator adjusts the steering angle of each wheel, i.e., the tire angle. The vehicle control device includes: a state quantity calculation unit configured to calculate state quantities including a yaw rate of the vehicle; a wheel request generating unit configured to calculate a required lateral force value for each wheel based on the request, the required lateral force value for each wheel being a required value for the lateral force of each wheel; as well as an instruction value generating unit configured to output an instruction value for controlling the steering actuator based on the required wheel lateral force value; The vehicle has an anti-skid function that suppresses the vehicle's skidding by independently adjusting the front-rear force acting on each wheel. The wheel requirement generating unit is configured to calculate a first lateral force limit value and limit the front wheel lateral force requirement value to a value below the first lateral force limit value when the anti-skid function fails and the state quantity indicates that the vehicle is in an oversteering state, wherein the first lateral force limit value is a limit value of the lateral force that can act on the rear wheel, and the front wheel lateral force requirement value is a lateral force requirement value for each of the front wheels.

2. The vehicle control device according to claim 1, wherein: The control request generating unit is further provided, the control request generating unit being configured to calculate a vehicle longitudinal force request value based on the request, the vehicle longitudinal force request value being a request value for the longitudinal force of the vehicle, The wheel requirement generating unit is configured to calculate the wheel longitudinal force requirement value for each wheel based on the vehicle longitudinal force requirement value. The instruction value generating unit is configured to output an instruction value for controlling the driving actuator and an instruction value for controlling the braking actuator based on the required values ​​of the front and rear forces of each wheel. The wheel requirement generating unit is configured to calculate a first front-rear force limit value when the state quantity indicates that the vehicle is in an oversteering state in the case where the anti-skid function fails, and reduce the magnitude of the vehicle front-rear force requirement value so that the front-rear force acting on the outer rear wheel of the turn becomes smaller than the first front-rear force limit value, wherein the first front-rear force limit value is a limit value of the front-rear force that can act on the rear wheel. The turning outer rear wheel is a rear wheel located on the outer side of the rear wheels when viewed from the turning center of the vehicle.

3. The vehicle control device according to claim 2, wherein: The wheel requirement generating unit is configured to calculate a second front-to-rear force limit value when the state quantity indicates that the vehicle is in an understeering state in the case where the anti-skid function fails, and reduce the magnitude of the vehicle front-to-rear force requirement value so that the front-to-rear force acting on the outer front wheel of the turn becomes smaller than the second front-to-rear force limit value, wherein the second front-to-rear force limit value is a limit value of the front-to-rear force that can act on the front wheel. The turning outer front wheel is a front wheel located on the outer side of the front wheels when viewed from the turning center of the vehicle.

4. The vehicle control device according to any one of claims 1 to 3, wherein: The wheel requirement generating unit is configured to calculate a second lateral force limit value and limit the front wheel lateral force requirement value to a value below the second lateral force limit value when the anti-skid function fails and the state quantity indicates that the vehicle is in an understeering state, wherein the second lateral force limit value is a limit value of the lateral force that can act on the front wheel.

5. The vehicle control device according to claim 2 or 3, wherein: The wheel requirement generating unit is configured to reduce the magnitude of the vehicle's front and rear force requirement value when the state quantity indicates that the duration of the vehicle's operation in an oversteering state or an understeering state is longer than a prescribed designated time, compared to a case where the duration is less than the designated time. Based on whether the requirement from the driving support device prioritizes braking of the vehicle or turning of the vehicle, the designated time is extended when braking is prioritized compared to when turning is prioritized.

6. A computer-readable medium storing a vehicle control program for causing a vehicle control device to perform support control to automatically drive the vehicle, wherein: The support control is a control for controlling the vehicle based on a request output by a driving support device that supports the travel of the vehicle. The above vehicle has: the aforementioned driving support device; Wheels, including front and rear wheels; driving the actuator and the brake actuator to generate a front-rear force, wherein the front-rear force refers to a force acting on the vehicle in a front-rear direction; as well as The steering actuator adjusts the steering angle of each wheel, i.e., the tire angle. The vehicle has an anti-skid function that suppresses the vehicle's skidding by independently adjusting the front-rear force acting on each wheel. The vehicle control program is configured to cause the control device to execute: a state quantity calculation process for calculating state quantities including a yaw rate of the vehicle; Wheel requirement generation processing, calculating a required lateral force value for each wheel based on the above requirements, the required lateral force value for each wheel being a required lateral force value for each wheel; as well as Indicator value generation processing, outputting an indicator value for controlling the steering actuator based on the above-mentioned lateral force requirement value of each wheel, The wheel requirement generation process includes calculating a first lateral force limit value and limiting the front wheel lateral force requirement value to a value below the first lateral force limit value when the anti-skid function fails and the state quantity indicates that the vehicle is in an oversteering state, wherein the first lateral force limit value is a limit value of the lateral force that can act on the rear wheel, and the front wheel lateral force requirement value is a lateral force requirement value for each of the front wheels.

7. A vehicle control method for causing the vehicle to automatically travel by controlling the vehicle based on a request output by a driving support device that supports the vehicle's travel, wherein: The above vehicle has: the aforementioned driving support device; Wheels, including front and rear wheels; driving the actuator and the brake actuator to generate a front-rear force, wherein the front-rear force refers to a force acting on the vehicle in a front-rear direction; as well as The steering actuator adjusts the steering angle of each wheel, i.e., the tire angle. The vehicle has an anti-skid function that suppresses the vehicle's skidding by independently adjusting the front-rear force acting on each wheel. The vehicle control method includes: a state quantity calculation process for calculating state quantities including a yaw rate of the vehicle; Wheel requirement generation processing, calculating a required lateral force value for each wheel based on the above requirements, the required lateral force value for each wheel being a required lateral force value for each wheel; as well as Indicator value generation processing, outputting an indicator value for controlling the steering actuator based on the above-mentioned lateral force requirement value of each wheel, The wheel requirement generation process includes calculating a first lateral force limit value and limiting the front wheel lateral force requirement value to a value below the first lateral force limit value when the anti-skid function fails and the state quantity indicates that the vehicle is in an oversteering state, wherein the first lateral force limit value is a limit value of the lateral force that can act on the rear wheel, and the front wheel lateral force requirement value is a lateral force requirement value for each of the front wheels.

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