Vehicle control device, vehicle control method, and vehicle control system

Abstract

To provide a vehicle control device, a vehicle control method and a vehicle control system which can enhance follow-up accuracy to an avoidance route.SOLUTION: A vehicle control device, a vehicle control method and a vehicle control system in one aspect acquire a first angle which is an angle formed by a direction of a vehicle and a direction of travel of the vehicle, acquire an avoidance route for avoiding an article which is located in front of the vehicle, execute first angle control which brings the first angle close to a prescribed reference angle when executing route follow-up control which allows the vehicle to travel following the avoidance route, and selectively switch a control object of the first angle control to one of a steering actuator or both of a control drive actuator and the steering actuator on the basis of a physical quantity resulting from tire force of the vehicle.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vehicle control device, a vehicle control method, and a vehicle control system.

Background Art

[0002] The vehicle control device of Patent Document 1 comprises: a travel route control unit that updates a target travel route of a vehicle; and an automatic emergency avoidance control unit that executes automatic emergency avoidance control processing for automatically activating a predetermined control system to avoid collision with an obstacle. The travel route control unit corrects the target travel route to calculate a plurality of corrected travel routes for avoiding an obstacle, evaluates the corrected travel routes by a predetermined evaluation function to select one corrected travel route, and generates a first request signal so that the vehicle travels along the corrected travel route. Meanwhile, the automatic emergency avoidance control unit generates a second request signal.

Prior Art Literature

Patent Literature

[0003]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] By the way, when a vehicle control device performs route following control for causing a vehicle to travel along an avoidance route for avoiding an object located in front of the vehicle, if the angle formed between the orientation of the vehicle and the traveling direction of the vehicle is large, the following accuracy to the avoidance route may be lowered.

[0005] The present invention has been made in view of conventional circumstances, and an object of the present invention is to provide a vehicle control device, a vehicle control method, and a vehicle control system that can improve the following accuracy to an avoidance route.

Means for Solving the Problem

[0006] According to the vehicle control device, vehicle control method, and vehicle control system of the present invention, in one embodiment, the angle between the orientation of the vehicle and the direction of travel of the vehicle Estimated value When obtaining a first angle, obtaining an avoidance path to avoid an object located in front of the vehicle, and performing path following control to drive the vehicle along the avoidance path, the first angle is Set to zero or a value in the vicinity of zero. A first angle control is performed to approach a predetermined reference angle, and the control target of the first angle control is the physical quantity caused by the tire force of the vehicle. The first angle and the angular velocity of the first angle are the first angle and the first angle Based on this, it selectively switches to either the steering actuator or both the braking / driving actuator and the steering actuator. The following selection conditions for selecting the control target for the first angle control are: the absolute value of the first angle is greater than a predetermined first angle threshold which is greater than the predetermined reference angle; the absolute value of the first angle is less than a predetermined second angle threshold which is greater than the predetermined first angle threshold; and the absolute value of the angular velocity of the first angle is less than a predetermined angular velocity threshold which is greater than zero. If the selection conditions are met, both the braking / driving actuator and the steering actuator are selected as the control target for the first angle control; if the selection conditions are not met, the steering actuator is selected as the control target for the first angle control. [Effects of the Invention]

[0007] According to the present invention, the accuracy of following an avoidance path can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram showing a vehicle control system according to the first embodiment. [Figure 2] This diagram shows the operation of collision avoidance assistance using a combination of AEB and ESS. [Figure 3] This is a block diagram showing the steering support request value calculation unit of the first embodiment. [Figure 4] This is a block diagram showing the β-angle minimization requirement calculation unit of the first embodiment. [Figure 5] This is a block diagram showing the control signal calculation unit of the first embodiment. [Figure 6] This is a flowchart showing the selection process for the control device of the first embodiment. [Figure 7] This is a flowchart showing the selection process for the control device of the first embodiment. [Figure 8] This is a flowchart showing the selection process for the control device of the first embodiment. [Figure 9]FIG. 1 is a diagram illustrating that a recognition error of a lateral shift amount occurs due to a vehicle slip angle. [Figure 10] FIG. 2 is a diagram showing that a follow-up error to a target path is reduced by reducing the vehicle slip angle. [Figure 11] FIG. 3 is a diagram showing generation of a yaw moment by controlling lateral force of front wheels and longitudinal force of each wheel. [Figure 12] FIG. 4 is a block diagram showing a vehicle control system according to a second embodiment. [Figure 13] FIG. 5 is a block diagram showing a control signal calculation unit according to the second embodiment. [Figure 14] FIG. 6 is a flowchart showing a control device selection process according to the second embodiment. [Figure 15] FIG. 7 is a flowchart showing a control device selection process according to the second embodiment. [Figure 16] FIG. 8 is a flowchart showing a control device selection process according to the second embodiment. [Figure 17] FIG. 9 is a block diagram showing a vehicle control system according to a third embodiment. [Figure 18] FIG. 10 is a block diagram showing a control signal calculation unit according to the third embodiment. [Figure 19] FIG. 11 is a flowchart showing a control device selection process according to the third embodiment. [Figure 20] FIG. 12 is a flowchart showing a control device selection process according to the third embodiment. [Figure 21] FIG. 13 is a block diagram showing a vehicle control system according to a fourth embodiment. [Figure 22] FIG. 14 is a flowchart showing a control device selection process according to the fourth embodiment. [Figure 23] FIG. 15 is a flowchart showing a control device selection process according to the fourth embodiment. [Figure 24] FIG. 16 is a flowchart showing a control device selection process according to the fourth embodiment. MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments of the vehicle control device, vehicle control method, and vehicle control system according to the present invention will be described with reference to the drawings. [First Embodiment] Figure 1 is a block diagram showing one embodiment of a vehicle control system 200 installed in a vehicle 100 such as a four-wheeled automobile.

[0010] The vehicle control system 200 is a system that provides collision avoidance assistance, which will be explained in detail later. The vehicle control system 200 includes a braking device 300 that applies braking force to each wheel of the vehicle 100 (a pair of front wheels and a pair of rear wheels), a front wheel steering device 400 that steers the front wheels of the vehicle 100, and a vehicle control device 500 installed on the vehicle 100.

[0011] The braking device 300 described above includes an actuator capable of individually controlling the braking force applied to each wheel by an electrical signal. Furthermore, the front wheel steering system 400 is equipped with an actuator that can control the steering angle of the front wheels by an electrical signal.

[0012] Here, the braking device 300 is a braking actuator that applies braking force to each wheel of the vehicle 100, among the braking and driving actuators that apply braking and driving force to each wheel. In other words, in this application, the braking-driving actuator includes a braking actuator and a driving actuator, and the braking device 300 corresponds to the braking actuator among the braking-driving actuators. Furthermore, the front wheel steering device 400 is a front wheel steering actuator that steers the front wheels among the steering actuators that steer the wheels of the vehicle 100.

[0013] The vehicle control device 500 includes a microcomputer 510 which serves as a control unit that performs calculations based on the input information and outputs the calculation results. The microcomputer 510 includes an MPU (Microprocessor Unit), ROM (Read Only Memory), RAM (Random Access Memory), and other components, which are not shown in the diagram. The microcomputer 510 can also be referred to as an MCU (Micro Controller Unit), processor, processing unit, or arithmetic unit.

[0014] The vehicle 100 has various sensors for detecting the vehicle's state, and the microcomputer 510 acquires the signals output by these various sensors. Vehicle 100 has various sensors, including an acceleration sensor 101, a gyro sensor 102, a steering angle sensor 103, a self-position recognition sensor 104, an external environment recognition sensor 105, and a wheel speed sensor 106.

[0015] The acceleration sensor 101 is a sensor that detects acceleration in the behavior of the vehicle 100, and detects the longitudinal acceleration, lateral acceleration (in other words, acceleration in the left-right direction), and vertical acceleration of the vehicle 100. The gyro sensor 102 is a sensor that detects the angular velocity of the vehicle 100's behavior, and detects the yaw rate, roll rate, and pitch rate of the vehicle 100.

[0016] The steering angle sensor 103 detects the steering angle θ caused by the driver's operation of the vehicle 100. The self-position recognition sensor 104 includes a GPS receiver that measures the latitude and longitude of the vehicle 100's position by receiving signals from GPS satellites, for example, and detects the position of the vehicle 100.

[0017] The external environment recognition sensor 105 is a device that acquires external information of the vehicle 100, in other words, information about the driving environment of the road on which the vehicle 100 travels, and includes, for example, a camera, radar, LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging). The wheel speed sensor 106 is a sensor that detects the rotational speed of each wheel of the vehicle 100.

[0018] The microcomputer 510 has a function to provide collision avoidance support in order to avoid or mitigate collision damage with an object (hereinafter referred to as an obstacle) located in the direction of travel ahead of the vehicle 100. The microcomputer 510 performs Autonomous Emergency Braking (AEB), which automatically activates the braking system 300 based on the collision risk, and Emergency Steering Support (ESS), which causes the vehicle 100 to follow an automatically generated avoidance path triggered by the driver's evasive steering.

[0019] Figure 2 illustrates the transition of support actions in collision avoidance assistance using a combination of AEB and ESS. In collision avoidance support using a combination of AEB and ESS, the microcomputer 510 gradually strengthens collision avoidance support in stages as the risk of collision with an obstacle recognized by the external environment recognition sensor 105 increases, in the following steps: "warning to the driver" → "primary braking (preliminary braking) by AEB" → "secondary braking (main braking) by AEB" & "steering assistance by ESS".

[0020] In the following embodiments, the intervention timing for "steering assistance by ESS" and the intervention timing for "secondary braking (main braking) by AEB" are described as being the same, but the intervention timing for "steering assistance by ESS" may be different from the intervention timing for "secondary braking (main braking) by AEB". In other words, the timing of intervention for "steering assistance by ESS" can be set independently of the intervention timings for "primary braking (preliminary braking) by AEB" and "secondary braking (main braking) by AEB" mentioned above.

[0021] Figure 1 shows the functional blocks for the collision avoidance support described above. The microcomputer 510 has the following functional units: a steering assistance request value calculation unit 520 which is responsible for the ESS function, a braking assistance request value calculation unit 530 which is responsible for the AEB function, a control signal calculation unit 540, a vehicle slip angle calculation unit 550, and a control device selection unit 560.

[0022] The control signal calculation unit 540 acquires the steering support request value output by the steering support request value calculation unit 520 and the braking support request value output by the braking support request value calculation unit 530, and calculates the braking control signal for each wheel and the front wheel steering control signal based on these. The control signal calculation unit 540 then outputs a braking control signal to the braking device 300 and a front wheel steering control signal to the front wheel steering device 400.

[0023] Furthermore, when the braking device 300 generates braking force in accordance with the control current, the control signal calculation unit 540 can output a braking control current as a braking control signal. Similarly, when the front wheel steering device 400 generates steering force in accordance with the control current, the control signal calculation unit 540 can output a front wheel steering control current as a front wheel steering control signal.

[0024] The vehicle slip angle calculation unit 550 calculates a first angle (hereinafter referred to as the vehicle slip angle β) which is the angle between the orientation of the vehicle 100 and the direction of travel of the vehicle 100. The vehicle slip angle calculation unit 550 acquires longitudinal and lateral acceleration information detected by the acceleration sensor 101 and yaw rate information detected by the gyro sensor 102, and performs calculation processing to estimate the vehicle slip angle β based on this information.

[0025] The steering assistance request value calculation unit 520 has a path following control function (in other words, an ESS function) that generates an avoidance path to avoid an obstacle triggered by the driver's steering operation and calculates steering request values ​​to make the vehicle 100 follow the avoidance path. Furthermore, the steering support request value calculation unit 520 includes a vehicle slip angle control function that calculates steering request values ​​and braking request values ​​to obtain the yaw moment necessary to bring the vehicle slip angle β closer to a predetermined reference angle βTH when making the vehicle 100 follow an avoidance path.

[0026] The control device selection unit 560 acquires a vehicle slip angle β signal from the vehicle slip angle calculation unit 550 and outputs a control device selection signal to the steering support request value calculation unit 520, which is a signal for instructing the control target in vehicle slip angle control. Here, the control device selection unit 560 selectively switches the control target in the vehicle slip angle control function to either the front wheel steering device 400 or both the braking device 300 and the front wheel steering device 400, based on the vehicle slip angle β. In other words, the control device selection unit 560 has the function of selectively switching the control target in vehicle slip angle control to either the steering actuator or both the braking / driving actuator and the steering actuator, based on the vehicle slip angle β, which is a physical quantity caused by the tire force.

[0027] One method of path-following control is to feed back the lateral positional deviation between the vehicle's predicted position at the forward gaze point and the target path. In collision avoidance scenarios, a larger vehicle slip angle β leads to a greater error in the predicted position of the vehicle at the forward focus point, resulting in a larger error in tracking the target path. Therefore, when the steering support request value calculation unit 520 performs path following control to make the vehicle 100 follow the avoidance path, it performs vehicle body slip angle control to reduce the vehicle slip angle β, thereby improving the accuracy of following the avoidance path.

[0028] Furthermore, the control device selection unit 560 has a function that selectively switches the control target in vehicle slip angle control according to the vehicle slip angle β. This makes it possible to select a control target that takes into account the tire force of each wheel and the limits of the tire force of each wheel in order to obtain the yaw moment necessary to reduce the vehicle slip angle β, thereby stably achieving minimization of the vehicle slip angle β in each situation. Therefore, the microcomputer 510 can make the vehicle 100 follow an avoidance path with high precision in each situation, and can achieve a high level of steering assistance for collision avoidance.

[0029] The functional blocks shown in Figure 1 will be explained in detail below. Figure 3 is a functional block diagram showing the details of the steering support request value calculation unit 520. The steering support request value calculation unit 520 includes a β angle minimization request value calculation unit 521, an avoidance path following request value calculation unit 522, and an addition unit 523.

[0030] The avoidance path following request value calculation unit 522 acquires information on the steering angle θ detected by the steering angle sensor 103, the external environment recognition state by the external environment recognition sensor 105 (specifically, information on the position and size of obstacles), the position information of the vehicle 100 by the self-position recognition sensor 104, and wheel speed information detected by the wheel speed sensor 106 (in other words, vehicle speed information). Furthermore, the avoidance path following request value calculation unit 522 receives a braking support flag signal indicating the operating status of AEB from the braking support request value calculation unit 530, and outputs an avoidance path generation flag signal indicating the avoidance path generation status (in other words, the operating status of ESS) to the braking support request value calculation unit 530.

[0031] Then, when the AEB enters a secondary braking state, the avoidance path following request value calculation unit 522 generates an avoidance path to avoid the obstacle based on the positional relationship between the vehicle and the obstacle, the speed of the vehicle 100, and the steering angle θ (in other words, avoidance steering information from the driver). As mentioned above, the steering support request value calculation unit 520 can set the timing of steering support intervention independently of the AEB operation by the braking support request value calculation unit 530. In this case, the avoidance path following request value calculation unit 522 will independently determine the intervention timing based on indicators such as collision risk and generate an avoidance path, thus eliminating the need to exchange signals of the braking support flag and the avoidance path generation flag between the avoidance path following request value calculation unit 522 and the braking support request value calculation unit 530.

[0032] The avoidance path following request value calculation unit 522, once it has generated an avoidance path, calculates the lateral position deviation Δy (in other words, the avoidance path following error) between the predicted position of the vehicle at the forward gaze point and the avoidance path. Next, the avoidance path following request value calculation unit 522 calculates and outputs the required lateral force of the front wheels (in other words, the required lateral force for steering assistance, or the required lateral force for ESS) required to make the vehicle 100 follow the avoidance path, based on the lateral position deviation Δy.

[0033] The β-angle minimization requirement calculation unit 521 is a functional unit that performs vehicle slip angle control. The β angle minimization requirement calculation unit 521 acquires the vehicle slip angle β and the control device selection signal, and outputs the required lateral force of the front wheels and the required longitudinal force of each wheel as steering support components to obtain the yaw moment necessary to bring the vehicle slip angle β closer to a predetermined reference angle βTH.

[0034] The addition unit 523 acquires the required lateral force of the front wheels output by the avoidance path following request value calculation unit 522 and the required lateral force of the front wheels output by the β angle minimization request value calculation unit 521, and outputs the sum of these values ​​to the control signal calculation unit 540 as the required lateral force of the front wheels in steering assistance. On the other hand, the required longitudinal force for each wheel output by the β-angle minimization requirement calculation unit 521 is output directly to the control signal calculation unit 540 as the required longitudinal force for each wheel in steering assistance.

[0035] Figure 4 is a functional block diagram showing the details of the β-angle minimization requirement calculation unit 521. The β-angle minimization requirement calculation unit 521 includes a comparison unit 521A, a first conversion unit 521B, a second conversion unit 521C, and a forward / reverse force output switching unit 521D. The comparison unit 521A acquires information on the vehicle body slip angle β[deg] calculated by the vehicle slip angle calculation unit 550 and information on the reference angle βTH[deg], calculates the deviation Δβ[deg] between the vehicle body slip angle β and the reference angle βTH, and outputs the obtained deviation Δβ information.

[0036] The first conversion unit 521B acquires information on the deviation Δβ and converts the deviation Δβ into the required longitudinal force for each wheel. In other words, the longitudinal force required for each wheel by the first conversion unit 521B is the longitudinal force required for each wheel in order to obtain the yaw moment necessary to set the vehicle body slip angle β to the reference angle βTH.

[0037] The second conversion unit 521C acquires information on the deviation Δβ and converts the deviation Δβ into the required lateral force for the front wheels. In other words, the required lateral force for the front wheels determined by the second conversion unit 521C is the lateral force required for the front wheels in order to obtain the yaw moment necessary to set the vehicle body slip angle β to the reference angle βTH.

[0038] The reference angle βTH acquired by the comparison unit 521A is set to zero or a value close to zero. Furthermore, if the reference angle βTH is zero, the comparison unit 521A will output the vehicle body slip angle β calculated by the vehicle slip angle calculation unit 550 as is. Therefore, when the reference angle βTH is zero, the first conversion unit 521B and the second conversion unit 521C will calculate the longitudinal force of each wheel and the lateral force of the front wheel in order to obtain the yaw moment necessary to make the vehicle slip angle β zero.

[0039] The longitudinal force output switching unit 521D acquires the required longitudinal force information for each wheel obtained by the first conversion unit 521B, and the control device selection signal output by the control device selection unit 560. Here, the control device selection signal is set to a binary signal. Furthermore, when the control device selection signal is 1, it indicates that both the braking system 300 and the front wheel steering system 400 are selected as the control targets in vehicle slip angle control. On the other hand, when the control device selection signal is 0, it indicates that only the front wheel steering system 400 is selected as the control target in vehicle slip angle control.

[0040] When the control device selection signal is 1 and the braking device 300 is included in the controlled objects in vehicle slip angle control, the front / rear force output switching unit 521D outputs the information of the required front / rear force for each wheel obtained by the first conversion unit 521B as the required front / rear force for each wheel for vehicle slip angle control (in detail, the braking request value). When the control device selection signal is 0 and the braking device 300 is not included in the controlled objects in the vehicle slip angle control, the front / rear force output switching unit 521D outputs the required front / rear force for each wheel of the vehicle slip angle control as 0.

[0041] In other words, the longitudinal force output switching unit 521D switches whether or not to add the braking device 300 to the controlled object in vehicle slip angle control by switching, in accordance with the control device selection signal, whether to output the required longitudinal force for each wheel determined by the first conversion unit 521B as is, or to output the required longitudinal force for each wheel as zero. Then, the required longitudinal force for each wheel for vehicle slip angle control, output by the longitudinal force output switching unit 521D, is output directly from the steering support request value calculation unit 520 as the required longitudinal force for each wheel for steering support.

[0042] Meanwhile, the required lateral force of the front wheels for vehicle slip angle control, as determined by the second conversion unit 521C, is output to the adder unit 523 and added to the required lateral force of the front wheels determined by the avoidance path following request value calculation unit 522. The addition unit 523 outputs the addition result to the control signal calculation unit 540 as the required lateral force for steering assistance.

[0043] The braking support request value calculation unit 530 shown in Figure 1 acquires the output of the external environment recognition sensor 105 (in other words, external environment recognition information), the output of the wheel speed sensor (in other words, information on the speed of the vehicle 100), and the avoidance path generation flag signal output by the steering support request value calculation unit 520. The braking support request value calculation unit 530 then calculates and outputs the required longitudinal force for each wheel required to avoid a collision or mitigate collision damage (in other words, the required longitudinal force for braking support, or the required longitudinal force for AEB).

[0044] In other words, the braking support request value calculation unit 530 automatically generates braking force to avoid a collision or mitigate collision damage by detecting obstacles such as cars or objects in front of the vehicle using external recognition sensors 105 such as cameras and radar. Furthermore, the braking support request value calculation unit 530 outputs a braking support flag signal indicating the operating status of the AEB to the steering support request value calculation unit 520. Furthermore, if the steering support request value calculation unit 520 independently sets the timing of the steering support intervention, the output of the braking support flag from the braking support request value calculation unit 530 to the steering support request value calculation unit 520 can be omitted.

[0045] The control signal calculation unit 540 obtains signals for the required longitudinal force and lateral force for steering support from the steering support request value calculation unit 520, and further obtains a signal for the required longitudinal force for braking support from the braking support request value calculation unit 530. Furthermore, the control signal calculation unit 540 acquires the output of the wheel speed sensor (in other words, information on the speed of the vehicle 100). The control signal calculation unit 540 then outputs braking control signals for each wheel to the braking device 300 and steering control signals for the front wheels to the front wheel steering device 400.

[0046] Figure 5 is a block diagram showing the details of the control signal calculation unit 540. The summing unit 541 acquires the required longitudinal force signals for steering assistance and the required longitudinal force signals for braking assistance, and outputs the sum of these values ​​as the final required longitudinal force signal for collision avoidance assistance. The first conversion unit 542 converts the collision avoidance support required longitudinal force signals output by the addition unit 541 into braking control signals for each wheel.

[0047] The second conversion unit 543 acquires a signal of the required lateral force of the front wheels for steering assistance and converts the signal of the required lateral force of the front wheels for steering assistance into a steering control signal for the front wheels. The comparison unit 544 acquires a vehicle speed signal based on the output of the wheel speed sensor 106, compares the acquired vehicle speed signal with a threshold value, and outputs a switching signal to switch between outputting a requested value for collision avoidance support and stopping.

[0048] The switching unit 545 acquires the braking control signals for each wheel output by the first conversion unit 542, the steering control signal for the front wheels output by the second conversion unit 543, and the switching signal output by the comparison unit 544. Then, based on the switching signal, the switching unit 545 switches between outputting the braking control signals for each wheel output by the first conversion unit 542 and the steering control signals for the front wheels output by the second conversion unit 543 to the subsequent stages (braking device 300, front wheel steering device 400) and stopping them.

[0049] Here, in a low-speed state where the vehicle speed is below a threshold, the switching unit 545 sets the braking control signal output to the braking device 300 and the steering control signal output to the front wheel steering device 400 to zero, thereby stopping the output of the braking control signals for each wheel output by the first conversion unit 542 and the steering control signals for the front wheels output by the second conversion unit 543 to the subsequent stages. On the other hand, when the vehicle speed exceeds a threshold, the switching unit 545 outputs the braking control signals for each wheel output by the first conversion unit 542 and the steering control signals for the front wheels output by the second conversion unit 543 directly to the braking device 300 and the front wheel steering device 400. In other words, the control signal calculation unit 540 stops the braking control and steering control for collision avoidance assistance because the effectiveness of collision avoidance assistance decreases when the vehicle speed is sufficiently low.

[0050] The flowcharts in Figures 6-8 show the process of selecting the control target by the control device selection unit 560 and the process of controlling the vehicle slip angle by the β-angle minimization requirement value calculation unit 521. In step S601, the microcomputer 510 determines whether or not to activate the AEB braking assist based on the output of the external environment recognition sensor 105, which indicates a high risk of collision.

[0051] Then, if the AEB is activated, the microcomputer 510 will proceed to step S602 and beyond, as the ESS may be activated by the driver's steering input. On the other hand, if the AEB is not operating, the microcomputer 510 will terminate this routine because the prerequisites for activating the ESS are not met. Furthermore, if the steering assistance request value calculation unit 520 independently sets the timing of the steering assistance intervention, the microcomputer 510 will independently determine the preconditions for activating the ESS in step S601 based on indicators such as collision risk.

[0052] In step S602, the microcomputer 510 calculates the longitudinal and lateral speeds [km / h] of the vehicle 100 based on the output of the acceleration sensor 101 and the output of the gyro sensor 102. Next, in step S603, the microcomputer 510 determines whether the forward / backward velocity obtained in step S602 is greater than a threshold. At this point, the microcomputer 510 determines that if the longitudinal speed is below a threshold, the conditions for estimating the vehicle slip angle β are not met, in other words, the conditions under which the accuracy of estimating the vehicle slip angle β cannot be ensured, and therefore vehicle slip angle control cannot be performed, and terminates this routine.

[0053] On the other hand, if the velocity in the forward and backward direction is greater than the threshold, the microcomputer 510 proceeds to step S604. In step S604, the microcomputer 510 determines the vehicle slip angle β based on detected values ​​such as vehicle speed, yaw rate, and lateral acceleration, and then calculates the vehicle slip angular velocity α by differentiating the determined vehicle slip angle β with respect to time.

[0054] In other words, when the longitudinal speed is greater than a threshold, the microcomputer 510 acquires the vehicle slip angle β and the vehicle slip angular velocity α, which are physical quantities resulting from the tire force of the vehicle 100. The microcomputer 510 calculates the vehicle slip angle β and vehicle slip angular velocity α, with a sign indicating the difference between left and right directions.

[0055] Next, in step S605, the microcomputer 510 determines whether the absolute value of the vehicle slip angle β is less than the first threshold βTH1 (βTH1>0) and whether the absolute value of the vehicle slip angular velocity α is less than the threshold αTH1 (αTH1>0). In other words, in step S605, the microcomputer 510 determines whether the vehicle slip angle β is sufficiently small, below a threshold, and showing a decreasing trend.

[0056] If the microcomputer 510 determines in step S605 that the absolute value of the vehicle slip angle β is smaller than the first threshold βTH1 and the absolute value of the vehicle slip angular velocity α is smaller than the threshold αTH1, it proceeds to step S607. In step S607, the microcomputer 510 calculates the required lateral force of the front wheels to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH (for example, βTH = 0 [deg]).

[0057] In other words, the state in which the absolute value of the vehicle slip angle β is smaller than the first threshold βTH1, and the absolute value of the vehicle slip angular velocity α is smaller than the threshold αTH1, is a state in which the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH can be generated solely by steering control of the front wheels. Therefore, when the absolute value of the vehicle slip angle β is smaller than the first threshold βTH1, and the absolute value of the vehicle slip angular velocity α is smaller than the threshold αTH1, the microcomputer 510 selects only the front wheel steering system 400 as the control target for vehicle slip angle control.

[0058] Next, the microcomputer 510 proceeds to step S608 and determines whether the absolute value of the steering angle θ by the driver is greater than the threshold θTH, and whether the absolute value of the steering angular velocity ω, obtained by differentiating the steering angle θ with respect to time, is greater than the threshold ωTH. Here, the process in step S608 is to determine whether or not the driver's steering operation has been performed as a trigger to start the ESS (Energy Sweeper).

[0059] The microcomputer 510 determines that the operating conditions for the ESS are met when the absolute value of the steering angle θ is greater than the threshold θTH and the absolute value of the steering angular velocity ω is greater than the threshold ωTH, and proceeds to step S609. In step S609, the microcomputer 510 outputs a steering control signal for the front wheels based on the required lateral force of the front wheels for vehicle slip angle control determined in step S607. On the other hand, if the microcomputer 510 determines in step S608 that the absolute value of the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH, it determines that the operating conditions for the ESS are not met and terminates this routine without performing vehicle slip angle control.

[0060] If the microcomputer 510 determines in step S605 that the conditions that the absolute value of the vehicle slip angle β is less than the first threshold βTH1 and the absolute value of the vehicle slip angular velocity α is less than the threshold αTH1 are not met, it proceeds to step S606. In step S606, the microcomputer 510 determines whether the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2 (βTH2 > βTH1 > 0), and whether the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1. In other words, in step S606, the microcomputer 510 determines whether the vehicle slip angle β is within a predetermined range that does not include zero and whether it is showing an increasing trend.

[0061] Then, in step S606, if the microcomputer 510 determines that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, it proceeds to step S610. In step S610, the microcomputer 510 calculates the required lateral force of the front wheels and the required longitudinal force (required braking force) of each wheel to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH.

[0062] In other words, when the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, it is necessary to control the longitudinal force of each wheel in addition to steering control of the front wheels in order to generate the yaw moment required to bring the vehicle slip angle β closer to the reference angle βTH. Therefore, when the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, the microcomputer 510 selects both the front wheel steering system 400 and the braking system 300 as the control targets for vehicle slip angle control.

[0063] Next, the microcomputer 510 proceeds to step S611, and, similar to step S608, determines whether the steering angle θ is greater than the threshold θTH and whether the steering angular velocity ω is greater than the threshold ωTH. Then, if the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH, the microcomputer 510 proceeds to step S612.

[0064] In step S612, the microcomputer 510 outputs a steering control signal for the front wheels based on the required lateral force of the front wheels for vehicle slip angle control, and also outputs braking control signals for each wheel based on the required longitudinal force of each wheel for vehicle slip angle control. On the other hand, if the microcomputer 510 determines in step S611 that the conditions that the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH are not met, it terminates this routine without performing vehicle slip angle control.

[0065] Furthermore, if the microcomputer 510 determines in step S606 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and that the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then the process proceeds to step S613. In step S613, the microcomputer 510 calculates the required lateral force for the front wheels and the required longitudinal force (required braking force) for each rear wheel to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH.

[0066] If the microcomputer 510 determines in step S606 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and that the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then it is estimated that the lateral force on the front tires is saturated and there is no margin to generate longitudinal force on the tires. Therefore, the microcomputer 510 excludes the front wheels from the longitudinal force control in vehicle slip angle control and controls the longitudinal force of each rear wheel in vehicle slip angle control. Switching the controlled object helps prevent unstable control states.

[0067] In other words, if the microcomputer 510 determines in step S606 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then it selects the front wheel steering device 400 (front wheel steering actuator) and the rear wheel braking device 300 (rear wheel braking actuator) as the control targets for vehicle slip angle control.

[0068] Next, the microcomputer 510 proceeds to step S614, and, similar to step S608, determines whether the steering angle θ is greater than the threshold θTH, and whether the steering angular velocity ω, obtained by differentiating the steering angle θ with respect to time, is greater than the threshold ωTH. Then, if the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH, the microcomputer 510 proceeds to step S615.

[0069] In step S615, the microcomputer 510 outputs a steering control signal for the front wheels based on the required lateral force of the front wheels for vehicle slip angle control, and also outputs a braking control signal for each rear wheel based on the required longitudinal force of each rear wheel for vehicle slip angle control. On the other hand, if the microcomputer 510 determines in step S614 that the conditions that the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH are not met, it terminates this routine without performing vehicle slip angle control.

[0070] After performing steps S609, S612, and S615, the microcomputer 510 proceeds to step S616, where it compares the vehicle speed VS, determined based on the output of the wheel speed sensor 106, with the threshold value VSTH. Here, the threshold VSTH is the vehicle speed VS, which is the termination condition for ESS.

[0071] The microcomputer 510 terminates vehicle slip angle control if the vehicle speed VS falls below the threshold VSTH. Meanwhile, the microcomputer 510 proceeds to step S617 if the vehicle speed VS is greater than or equal to the threshold VSTH and ESS continues.

[0072] In step S617, the microcomputer 510 determines whether the distance D from the vehicle 100 to the obstacle ahead is greater than the threshold DTH. In this case, if the distance D to the obstacle is greater than the threshold DTH, there is a large margin for collision avoidance control, and the requirement for accuracy in following the avoidance path is relatively low.

[0073] Therefore, if the microcomputer 510 determines in step S617 that the distance D to the obstacle is greater than the threshold DTH, it proceeds to step S607 and uses only the control of the front wheel steering device 400 to bring the vehicle slip angle β closer to the reference angle βTH. In other words, if the distance D to the obstacle is greater than the threshold DTH, the microcomputer 510 selects only the front wheel steering system 400 as the target for vehicle slip angle control, regardless of the conditions of the vehicle slip angle β and vehicle slip angular velocity α.

[0074] On the other hand, if the distance D to the obstacle is less than or equal to the threshold DTH, the margin for collision avoidance control is small, and it is necessary to quickly bring the vehicle slip angle β closer to the reference angle βTH to improve the ability to follow the avoidance path. Therefore, if the microcomputer 510 determines in step S617 that the distance D to the obstacle is less than or equal to the threshold DTH, it proceeds to step S605 and performs the selection of a control target based on the vehicle slip angle β and the vehicle slip angular velocity α.

[0075] The first threshold βTH1 and second threshold βTH2 for the vehicle slip angle β, and the threshold αTH1 for the vehicle slip angular velocity α, which the microcomputer 510 uses in the process of selecting the controlled object, are set as follows. The first threshold βTH1 for the vehicle slip angle β and the threshold αTH1 for the vehicle slip angular velocity α depend on the path-following control logic and are influenced by, for example, the forward gaze distance (forward gaze time / vehicle speed) in the case of forward gaze control. Therefore, the first threshold βTH1 for the vehicle slip angle β and the threshold αTH1 for the vehicle slip angular velocity α are adapted according to the path-following control logic, for example, the set value of the forward gaze distance.

[0076] Furthermore, the second threshold βTH2 of the vehicle slip angle β is influenced by factors that affect the tire friction circle (the limit of tire grip). Therefore, the second threshold βTH2 of the vehicle slip angle β is adapted according to the factors affecting the tire friction circle. Factors that affect the tire friction circle include, for example, contact load, tire type (summer or winter tires), tire pressure and temperature, tire wear, and road surface friction coefficient.

[0077] When the microcomputer 510 changes the second threshold βTH2 according to the ground load, it can estimate the ground load information from, for example, the output of the acceleration sensor 101 and the output of the gyro sensor 102, and increase the second threshold βTH2 as the ground load increases. Furthermore, when the microcomputer 510 changes the second threshold βTH2 according to the tire type, for example, it can obtain tire type information from the user of the vehicle 100 and increase the second threshold βTH2 when the vehicle 100 is equipped with summer tires (in other words, standard tires) compared to when it is equipped with winter tires (for example, studless tires).

[0078] Furthermore, when the microcomputer 510 changes the second threshold βTH2 according to the tire pressure and temperature, for example, it can acquire information on the tire pressure and temperature from sensors and increase the second threshold βTH2 as the air pressure increases and as the temperature increases. Furthermore, when the microcomputer 510 changes the second threshold βTH2 according to the amount of tire wear, for example, it can estimate the tire slip ratio from the output of the acceleration sensor 101 and the output of the gyro sensor 102, estimate the amount of tire wear from the slip ratio, and increase the second threshold βTH2 as the amount of tire wear increases.

[0079] Furthermore, when the microcomputer 510 changes the second threshold βTH2 according to the friction coefficient of the road surface, for example, it can estimate the tire slip ratio from the output of the acceleration sensor 101 and the output of the gyro sensor 102, estimate the friction coefficient of the road surface from the slip ratio, and increase the second threshold βTH2 as the friction coefficient of the road surface increases.

[0080] According to the collision avoidance support of the first embodiment described above, when the ESS that causes the vehicle 100 to follow the avoidance path is executed, the microcomputer 510 performs steering control and braking control to reduce the vehicle slip angle β, thereby improving the ability to follow the avoidance path and improving the performance of collision avoidance and damage mitigation. Furthermore, in vehicle slip angle control, which reduces the vehicle slip angle β, the microcomputer 510 selects the control target based on information about the vehicle slip angle β and the vehicle slip angular velocity α.

[0081] Therefore, the microcomputer 510 can switch the controlled object, taking into account the tire force of each wheel and the limits of the tire force, in order to obtain the yaw moment necessary to reduce the vehicle slip angle β. Therefore, the microcomputer 510 can effectively reduce the vehicle slip angle β, stably improving the accuracy of following the avoidance path, and by selectively intervening in braking control according to the situation, it can suppress brake pad wear and ensure functional safety in the long term.

[0082] Figure 9 is a state diagram showing the difference in the recognition of lateral displacement amount depending on the presence or absence of a vehicle slip angle β. The upper part of Figure 9 shows the state in which an error occurs in the recognition of lateral displacement amount due to the occurrence of a vehicle slip angle β, and the lower part of Figure 9 shows the state in which the recognition error of lateral displacement amount is eliminated as a result of control to reduce the vehicle slip angle β. When determining the amount of lateral displacement relative to the avoidance path based on the longitudinal direction of vehicle 100, if a vehicle slip angle β occurs and the longitudinal direction of vehicle 100 does not coincide with the vehicle speed vector, an error will occur in recognizing the amount of lateral displacement. As shown in the upper part of Figure 9, underestimating the amount of lateral displacement will reduce the ability to follow the avoidance path.

[0083] In this case, by applying a counterclockwise yaw moment to the vehicle 100 in Figure 9, the vehicle slip angle β can be brought close to zero, as shown in the lower part of Figure 9. This causes the longitudinal direction of the vehicle 100 to coincide with the vehicle speed vector, thereby reducing the recognition error of the lateral displacement. Furthermore, by correctly recognizing the amount of lateral displacement relative to the avoidance path, the ability to follow the avoidance path improves, leading to improved collision avoidance and damage mitigation performance.

[0084] Figure 10 is a time chart showing the correlation between the vehicle slip angle β and the tracking error relative to the target path, such as an avoidance route. The upper part of Figure 10 shows how the vehicle slip angle β decreases when control is implemented to reduce the vehicle slip angle β, and the lower part of Figure 10 shows that the tracking error with respect to the target path is reduced as the vehicle slip angle β decreases. In other words, by implementing vehicle slip angle control that reduces the vehicle slip angle β, the microcomputer 510 can correctly recognize the amount of lateral displacement relative to the avoidance path, thereby improving its ability to follow the avoidance path.

[0085] Figure 11 shows an example of setting lateral and longitudinal forces to obtain the yaw moment required to bring the vehicle slip angle β closer to the reference angle βTH. Figure 11 shows vehicle slip angle control when the vehicle slip angle β approaches zero by applying a counterclockwise yaw moment, in other words, a yaw moment that turns the vehicle 100 to the left.

[0086] In this case, the lateral force generated by steering the front wheels to the left can impart a yaw moment to the vehicle 100 that turns it to the left. Additionally, applying braking force to the left front and rear wheels of the vehicle 100 can also impart a yaw moment to the vehicle 100 that turns it to the left. Therefore, in steps S607, S612, and S615 described above, the microcomputer 510 sets the steering direction and the wheels to which braking force is applied according to the direction in which the vehicle slip angle β is generated, and sets the steering angle and longitudinal force (braking force) according to the magnitude of the vehicle slip angle β.

[0087] As shown in Figure 11, the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH can also be applied to the vehicle 100 by applying driving force to the wheel opposite to the side on which braking force is applied. For example, if a yaw moment that turns the vehicle 100 to the left is applied to the vehicle 100, driving force can be applied to the right wheel. In other words, the microcomputer 510 can bring the vehicle slip angle β closer to the reference angle βTH by controlling the braking force of each wheel as well as the driving force of each wheel.

[0088] [Second Embodiment] The following describes a second embodiment in which the microcomputer 510 selectively switches the control target in vehicle slip angle control, which brings the vehicle slip angle β closer to the reference angle βTH, to either the steering actuator or one of the three: the braking actuator, the drive actuator, and the steering actuator.

[0089] Figure 12 is a block diagram showing a vehicle control system 200 that implements collision avoidance support (AEB&ESS) in a second embodiment. In the vehicle control system 200 shown in Figure 12, the same elements as those in the vehicle control system 200 of the first embodiment shown in Figure 1 are denoted by the same reference numerals, and a detailed explanation of blocks that perform the same functions is omitted.

[0090] The vehicle control system 200 shown in Figure 12 differs from the vehicle control system 200 of the first embodiment shown in Figure 1 in that a drive unit 310 that provides driving force to each of the four wheels to be controlled is added, and the control signal calculation unit 540 also outputs a control signal to the drive unit 310. The drive unit 310 includes actuators that can individually electronically control the driving force of each wheel using electrical signals. The drive unit 310 is a drive actuator that provides driving force to each wheel among the brake and drive actuators for each wheel, and the vehicle 100 equipped with the drive unit 310 is a so-called four-wheel drive vehicle.

[0091] Furthermore, the steering support request value calculation unit 520 has the same configuration as in the first embodiment (see Figure 3), but the β angle minimization request value calculation unit 521, which constitutes the steering support request value calculation unit 520, calculates the braking force of each wheel and the driving force of each wheel as the required longitudinal force in vehicle slip angle control. The β angle minimization requirement calculation unit 521 calculates the required longitudinal force for each wheel in order to obtain a yaw moment in the direction that reduces the vehicle slip angle β. For example, as shown in Figure 11, it calculates the required longitudinal force for each wheel by applying a braking force to one of the left and right front and rear wheels and a driving force to the other front and rear wheel.

[0092] Figure 13 is a functional block diagram of the control signal calculation unit 540 in the second embodiment. In Figure 13, the same reference numerals are used for elements that are the same as those in Figure 5, which shows the details of the control signal calculation unit 540 of the first embodiment, and detailed explanations are omitted.

[0093] The control signal calculation unit 540 in the second embodiment shown in Figure 13 acquires signals for the required longitudinal force of each wheel for steering assistance (ESS) and signals for the required lateral force of the front wheels for steering assistance from the steering assistance request value calculation unit 520, and acquires signals for the required longitudinal force of each wheel for braking assistance (AEB) from the braking assistance request value calculation unit 530. Furthermore, the requested longitudinal force for steering assistance output by the steering assistance request value calculation unit 520 represents the requested driving force when it is a positive value, and the requested braking force when it is a negative value.

[0094] The summing unit 541 acquires the required longitudinal force signals for each wheel for steering support and the required longitudinal force signals for each wheel for braking support, and outputs the sum of these values ​​as the required longitudinal force signal for each wheel for collision avoidance support. The first conversion unit 542 converts the collision avoidance support signals for each wheel output by the addition unit 541 into brake / drive control signals for each wheel.

[0095] The code discrimination unit 546 determines whether the requested longitudinal force for each wheel is a braking request or a driving request by discriminating the codes of the requested longitudinal force for each wheel output by the addition unit 541 for collision avoidance support. The braking signal switching unit 547 acquires braking and driving control signals for each wheel from the first conversion unit 542, and also acquires a signal indicating the result of code discrimination from the code discrimination unit 546.

[0096] Then, the braking signal switching unit 547 outputs a braking control signal of zero, that is, no braking request for collision avoidance support, if the sign of the required longitudinal force for each wheel output by the summing unit 541 is positive and the required longitudinal force for collision avoidance support is the required driving force. On the other hand, if the sign of the required longitudinal force for each wheel of the collision avoidance support component output by the summing unit 541 is negative and the required longitudinal force of the collision avoidance support component is the required braking force, the braking-driving control signal output by the first conversion unit 542 is output as the braking control signal.

[0097] Furthermore, the drive signal switching unit 548 acquires brake / drive control signals for each wheel from the first conversion unit 542, and also acquires a signal indicating the result of code discrimination from the code discrimination unit 546. Then, the drive signal switching unit 548 outputs a drive control signal to zero, that is, no drive request for collision avoidance support, if the sign of the required longitudinal force for each wheel output by the summing unit 541 is negative and the required longitudinal force for collision avoidance support is the required braking force.

[0098] On the other hand, the drive signal switching unit 548 outputs the brake / drive control signal output by the first conversion unit 542 as the drive control signal if the sign of the required longitudinal force for each wheel of the collision avoidance support output by the addition unit 541 is positive and the required longitudinal force of the collision avoidance support is the required driving force. In other words, the code discrimination unit 546, the braking signal switching unit 547, and the drive signal switching unit 548 output a braking control signal or a drive control signal for each wheel, depending on whether the required front-to-rear force for collision avoidance support, which is obtained by adding the required front-to-rear force for steering support and the required front-to-rear force for braking support, is a required braking force or a required driving force.

[0099] The second conversion unit 543 acquires a signal of the required lateral force of the front wheels for steering assistance and converts the signal of the required lateral force of the front wheels for steering assistance into a steering control signal for the front wheels. Furthermore, the comparison unit 544 acquires a vehicle speed signal based on the output of the wheel speed sensor 106, compares the acquired vehicle speed signal with a threshold value, and outputs a switching signal to switch between outputting the required value for collision avoidance support and stopping.

[0100] The switching unit 545-2 acquires the braking control signals for each wheel output by the braking signal switching unit 547, the driving control signals for each wheel output by the driving signal switching unit 548, the steering control signal for the front wheels output by the second conversion unit 543, and the switching signal output by the comparison unit 544. Then, the switching unit 545-2 switches the output of the braking control signal, drive control signal, and steering control signal to the subsequent stages (braking device 300, drive device 310, front wheel steering device 400) and stops based on the switching signal output by the comparison unit 544.

[0101] In this configuration, when the vehicle speed is below a threshold, the output of the braking control signal, drive control signal, and steering control signal to the subsequent stages is stopped, and when the vehicle speed exceeds the threshold, the braking control signal, drive control signal, and steering control signal are output to the subsequent stages. In other words, the control signal calculation unit 540 determines that collision avoidance assistance is less effective when the vehicle speed is sufficiently low, and therefore stops the braking control, drive control, and steering control for collision avoidance assistance.

[0102] The flowcharts in Figures 14-16 show the process of selecting the control target by the control device selection unit 560 and the process of controlling the vehicle slip angle by the β angle minimization requirement value calculation unit 521 in the second embodiment. In the second embodiment, the β angle minimization requirement calculation unit 521 determines the required braking force or required driving force for each wheel as the required longitudinal force to obtain the yaw moment necessary to make the vehicle body slip angle β the reference angle βTH. On the other hand, the process of selecting the control target by the control device selection unit 560 in the second embodiment is the same as in the first embodiment.

[0103] Therefore, the flowcharts in Figures 14-16 differ from the flowcharts in Figures 6-8, which show the processing content of the first embodiment, only in the processing content in steps S612-2 and S615-2. Therefore, for each step other than steps S612-2 and S615-2, the same step numbers as in the flowcharts in Figures 6-8 are used, and detailed explanations are omitted.

[0104] If the microcomputer 510 determines in step S606 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then it proceeds to step S610. Then, in step S610, the microcomputer 510 calculates the required lateral force of the front wheels and the required longitudinal forces (required braking force, required driving force) of each wheel to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH.

[0105] Next, if the microcomputer 510 determines in step S611 that a steering operation by the driver has been performed as a trigger to start the operation of the ESS, it proceeds to step S612-2. In step S612-2, the microcomputer 510 outputs a steering control signal for the front wheels to the front wheel steering device 400 based on the required lateral force of the front wheels determined in step S610. It also outputs a braking control signal for each wheel to the braking device 300 and a drive control signal for each wheel to the drive device 310 based on the required longitudinal force (required braking force, required driving force) of each wheel determined in step S610.

[0106] Furthermore, if the microcomputer 510 determines in step S606 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then it proceeds to step S613. Then, in step S613, the microcomputer 510 calculates the required lateral force for the front wheels and the required longitudinal forces (required braking force, required driving force) for each rear wheel to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH.

[0107] Next, if the microcomputer 510 determines in step S614 that a steering operation by the driver has been performed as a trigger to start the operation of the ESS, it proceeds to step S615-2. In step S615-2, the microcomputer 510 outputs a steering control signal for the front wheels to the front wheel steering device 400 based on the required lateral force of the front wheels determined in step S613. It also outputs a braking control signal for each rear wheel to the braking device 300 and a drive control signal for each rear wheel to the drive device 310 based on the required longitudinal force (required braking force, required driving force) of each rear wheel determined in step S613.

[0108] According to the second embodiment described above, when both a steering actuator and a braking / driving actuator are selected as the control targets for vehicle slip angle control, both the braking actuator and the driving actuator are selected from among the braking / driving actuators. Therefore, compared to the first embodiment in which only the braking actuator among the braking and driving actuators is selected, it becomes easier to secure the yaw moment necessary to bring the vehicle slip angle β closer to a predetermined reference angle βTH, and the accuracy of following the avoidance path can be stably maintained.

[0109] [Third Embodiment] Incidentally, if the vehicle 100 is equipped with a rear-wheel steering system in addition to the front-wheel steering system 400, the rear-wheel steering system can be included as a control target in the vehicle slip angle control for obtaining the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH. A third embodiment in which the vehicle slip angle control includes a rear-wheel steering system is described below.

[0110] Figure 17 is a block diagram showing a vehicle control system 200 that implements collision avoidance support (AEB&ESS) in the third embodiment. In the vehicle control system 200 shown in Figure 17, the same elements as those in the vehicle control system 200 shown in Figure 12 are given the same reference numerals, and a detailed explanation of blocks that perform the same function is omitted.

[0111] The vehicle control system 200 shown in Figure 17 differs from the vehicle control system 200 of the second embodiment shown in Figure 12 in that a rear-wheel steering device 410 is added as a control target, and the control signal calculation unit 540 also outputs a control signal to the rear-wheel steering device 410. The rear-wheel steering system 410 is equipped with an actuator that can electronically control the steering angle of the rear wheels using an electrical signal.

[0112] In this application, the steering actuator includes a front wheel steering actuator and a rear wheel steering actuator, the front wheel steering device 400 corresponds to the front wheel steering actuator of the steering actuator, and the rear wheel steering device 410 corresponds to the rear wheel steering actuator of the steering actuator. Furthermore, the vehicle 100 of the third embodiment includes both a front-wheel steering device 400 as a front-wheel steering actuator and a rear-wheel steering device 410 as a rear-wheel steering actuator.

[0113] Figure 18 is a functional block diagram of the control signal calculation unit 540 in the third embodiment. In Figure 18, the same reference numerals are used for elements that are the same as those in Figure 13, which shows the details of the control signal calculation unit 540 of the second embodiment, and detailed explanations are omitted.

[0114] The control signal calculation unit 540 in the third embodiment shown in Figure 18 acquires signals from the steering support request value calculation unit 520 for the required longitudinal force (required braking force and required driving force for each wheel) and the required lateral force (required lateral force for the front wheels and required lateral force for the rear wheels) for each wheel for steering support, and acquires signals from the braking support request value calculation unit 530 for the required longitudinal force (required braking force) for each wheel for braking support. The second conversion unit 543-3 then converts the required lateral force signals for each wheel (front and rear wheels) for steering assistance into steering control signals for the front wheels and steering control signals for the rear wheels.

[0115] The switching unit 545-3 outputs the brake / drive control signals for each wheel and the steering control signals for the front and rear wheels as zero when the vehicle speed is below a threshold, thereby stopping the brake / drive control and steering control for AEB and ESS. Furthermore, when the vehicle speed exceeds a threshold, the switching unit 545-3 outputs the brake / drive control signals for each wheel and the steering control signals for the front and rear wheels directly to the next stage, thereby activating the AEB and ESS. The control signal calculation unit 540 then outputs braking control signals for each wheel to the braking device 300, drive control signals for each wheel to the drive device 310, steering control signals for the front wheels to the front wheel steering device 400, and steering control signals for the rear wheels to the rear wheel steering device 410.

[0116] The flowcharts in Figures 19-20 show the process of selecting the control target by the control device selection unit 560 and the process of controlling the vehicle slip angle by the β angle minimization requirement value calculation unit 521 in the third embodiment. In the third embodiment, the microcomputer 510 uses the following conditions for selecting the controlled object in vehicle slip angle control: the absolute value of the vehicle slip angle β is greater than a first threshold βTH1 and less than a second threshold βTH2 (βTH2>βTH1>0), and the absolute value of the vehicle slip angular velocity α is greater than a threshold αTH1.

[0117] Then, based on whether the selection conditions are met, the microcomputer 510 selectively switches the control target in vehicle slip angle control to either both the front wheel steering system 400 and the rear wheel steering system 410 (in other words, only the steering actuators), or to one of the four components: the front wheel steering system 400, the rear wheel steering system 410, the braking system 300, and the drive system 310 (in other words, both the steering actuators and the braking / driving actuators).

[0118] The microcomputer 510 performs the same processing as described above in steps S601-S604 of the flowchart in Figures 19-20, from step S701 to step S704. Then, in step S705, the microcomputer 510 determines whether the following conditions are met: the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1.

[0119] If the microcomputer 510 determines in step S705 that the condition is not met, it proceeds to step S706. In step S706, the microcomputer 510 calculates the required lateral force for the front wheels and the required lateral force for the rear wheels to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH.

[0120] Next, in step S707, the microcomputer 510 determines whether the steering angle θ of the front wheels by the driver is greater than the threshold θTH, and whether the steering angular velocity ω is greater than the threshold ωTH. Then, if the operating conditions for the ESS are met, namely that the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH, the microcomputer 510 proceeds to step S708.

[0121] In step S708, the microcomputer 510 outputs a steering control signal for the front wheels to the front wheel steering device 400 based on the required lateral force of the front wheels, and also outputs a steering control signal for the rear wheels to the rear wheel steering device 410 based on the required lateral force of the rear wheels. In other words, if the conditions that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1 are not met, the microcomputer 510 selects the front wheel steering device 400 and the rear wheel steering device 410 (in other words, steering actuators including the front wheel steering actuator and the rear wheel steering actuator) as the targets for vehicle slip angle control.

[0122] If the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, then it is estimated that the yaw moment necessary to bring the vehicle slip angle β closer to a predetermined reference angle βTH can be generated solely by the lateral forces of each wheel through front wheel steering control and rear wheel steering control, or that the lateral forces of the tires have saturated and there is no margin to generate longitudinal forces of the tires. Therefore, if the conditions that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1 are not met, the microcomputer 510 selects only the steering actuators, including the front wheel steering device 400 and the rear wheel steering device 410, as the control targets in vehicle slip angle control.

[0123] On the other hand, if the microcomputer 510 determines in step S705 that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, it proceeds to step S709. In step S709, the microcomputer 510 calculates the required lateral force for the front wheels, the required lateral force for the rear wheels, and the required longitudinal forces (required braking force, required driving force) for each wheel, based on the deviation Δβ between the vehicle slip angle β and the reference angle βTH, in order to obtain the yaw moment necessary to bring the vehicle slip angle β closer to the reference angle βTH.

[0124] Next, the microcomputer 510 proceeds to step S710, and, similar to step S707, determines whether the conditions are met that the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH. Then, if the operating conditions for the ESS are met, namely that the steering angle θ is greater than the threshold θTH and the steering angular velocity ω is greater than the threshold ωTH, the microcomputer 510 proceeds to step S711. In step S711, the microcomputer 510 outputs a steering control signal for the front wheels to the front wheel steering device 400 based on the required lateral force of the front wheels, a steering control signal for the rear wheels to the rear wheel steering device 410 based on the required lateral force of the rear wheels, a braking control signal for each wheel to the braking device 300 based on the required braking force of each wheel, and a drive control signal for each wheel to the drive device 310 based on the required driving force of each wheel.

[0125] Furthermore, after processing in step S708 or step S711, the microcomputer 510 proceeds to step S712, where it compares the vehicle speed VS with the threshold value VSTH. Then, if the vehicle speed VS is below the threshold VSTH, the microcomputer 510 terminates the vehicle slip angle control, and if the vehicle speed VS is greater than or equal to the threshold VSTH, proceeds to step S713. In step S713, the microcomputer 510 determines whether the distance D from the vehicle 100 to the obstacle ahead is greater than the threshold DTH.

[0126] If the microcomputer 510 determines in step S713 that the distance D to the obstacle is greater than the threshold DTH, it proceeds to step S706, where it controls the steering of the front wheel steering device 400 and the rear wheel steering device 410 to bring the vehicle slip angle β closer to the reference angle βTH. On the other hand, if the distance D to the obstacle is less than or equal to the threshold DTH, the microcomputer 510 proceeds to step S705 and performs the selection of the control target based on the vehicle slip angle β and the vehicle slip angular velocity α.

[0127] In the third embodiment described above, the microcomputer 510 selects whether the controlled object in vehicle slip angle control is only the steering actuators including the front wheel steering device 400 and the rear wheel steering device 410, or both the steering actuators and the braking / driving actuators including the braking device 300 and the driving device 310, depending on whether the conditions are met that the absolute value of the vehicle slip angle β is greater than a first threshold βTH1 and less than a second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than a threshold αTH1. Furthermore, according to this third embodiment, since the steering control in vehicle slip angle control targets both the front wheel steering device 400 and the rear wheel steering device 410, the range in which vehicle slip angle control can be performed by steering control alone is expanded, and the instability of the vehicle 100's behavior can be suppressed.

[0128] [Fourth Embodiment] Incidentally, the microcomputer 510 can predict the future vehicle slip angle β and select the target for vehicle slip angle control based on the predicted vehicle slip angle βes. A fourth embodiment is described below in which the control target for vehicle slip angle control is selected based on the predicted vehicle slip angle βes. The fourth embodiment differs from the first embodiment in that the selection process for the vehicle slip angle control is performed based on the predicted vehicle slip angle βes instead of the vehicle slip angle β.

[0129] Figure 21 is a block diagram showing a vehicle control system 200 that implements collision avoidance support (AEB&ESS) in the fourth embodiment. In the vehicle control system 200 shown in Figure 21, the same elements as those in the vehicle control system 200 of the first embodiment shown in Figure 1 are denoted by the same reference numerals, and a detailed explanation of blocks that perform the same functions is omitted.

[0130] The vehicle control system 200 shown in Figure 21 differs from the vehicle control system 200 of the first embodiment shown in Figure 1 in that it includes a vehicle slip angle prediction unit 570. The vehicle slip angle prediction unit 570 obtains information on the azimuth angle of the avoidance path from the steering support request value calculation unit 520 and outputs information on the predicted vehicle slip angle βes to the control device selection unit 560. Here, the vehicle slip angle prediction unit 570 determines the predicted vehicle slip angle βes, which is the future vehicle slip angle β, based on the rate of change over time of the azimuth angle of the avoidance path.

[0131] The flowcharts in Figures 22-24 show the process of selecting the control target by the control device selection unit 560 and the process of controlling the vehicle slip angle by the β angle minimization requirement value calculation unit 521 in the fourth embodiment. The flowcharts in Figures 22-24 differ from the flowcharts in Figures 6-8, which show the first embodiment, in that step S604-4 is added to determine the predicted vehicle slip angle βes and the predicted vehicle slip angular velocity αes. Furthermore, in steps S605-4 and S606-4, the first threshold βTH1 and the second threshold βTH2 are compared with the predicted vehicle slip angle βes, and the threshold αTH1 is compared with the predicted vehicle slip angular velocity αes.

[0132] In step S604, the microcomputer 510 determines the current vehicle slip angle β and vehicle slip angular velocity α, and then proceeds to step S604-2. In step S604-2, the microcomputer 510 determines the time rate of change of the azimuth angle of the avoidance path, and based on the time conversion rate of the azimuth angle of the avoidance path, it determines the predicted vehicle slip angle βes, which is the future vehicle slip angle β. Furthermore, it determines the predicted vehicle slip angular velocity αes by differentiating the predicted vehicle slip angle βes with respect to time.

[0133] Then, in step S605-4, the microcomputer 510 determines whether the absolute value of the predicted vehicle slip angle βes is smaller than the first threshold βTH1, and whether the absolute value of the predicted vehicle slip angular velocity αes is smaller than the threshold αTH1. Furthermore, in step S606-4, the microcomputer 510 determines whether the absolute value of the predicted vehicle slip angle βes is greater than the first threshold βTH1 and less than the second threshold βTH2, and whether the absolute value of the predicted vehicle slip angular velocity αes is greater than the threshold αTH1.

[0134] In other words, in the fourth embodiment, the microcomputer 510 selectively switches the control target of the vehicle slip angle control based on the future vehicle slip angle βes and vehicle slip angular velocity αes, instead of the current vehicle slip angle β and vehicle slip angular velocity α. According to this fourth embodiment, the control target of the vehicle slip angle control is switched based on the predicted vehicle slip angle βes that is expected to occur in the future. Therefore, it is possible to anticipate changes in the vehicle slip angle β and switch to the appropriate control target in advance, thereby suppressing the response delay of the vehicle slip angle control.

[0135] The technical concepts described in the above embodiments can be used in appropriate combinations, as long as no contradictions arise. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it will be obvious to those skilled in the art that various modifications can be taken based on the basic technical concept and teachings of the present invention.

[0136] In the above embodiment, in collision avoidance support using a combination of AEB and ESS, control is applied to reduce the vehicle slip angle β as a control to improve the ability to follow the avoidance path generated in response to the driver's steering operation. However, collision avoidance support is not limited to the combination of AEB and ESS. For example, when the microcomputer 510 performs control to make the vehicle 100 follow an avoidance path automatically generated based on information from the external environment recognition sensor 105, it can perform vehicle slip angle control to reduce the vehicle slip angle β.

[0137] Furthermore, the microcomputer 510 can switch from a setting where the only control target in vehicle slip angle control, which is used to bring the vehicle slip angle β closer to the reference angle βTH, is the steering actuator. For example, the microcomputer 510 can control only the steering actuator when the vehicle slip angle β is less than the first threshold βTH1, control both the steering actuator and the brake / drive actuator when the vehicle slip angle β is greater than or equal to the first threshold βTH1 and greater than or equal to the second threshold βTH2, and control only the steering actuator or both the steering actuator and the rear wheel brake / drive actuator when the vehicle slip angle β is greater than the second threshold βTH2. In other words, the microcomputer 510 can stepwise switch the controlled object in response to an increase in the vehicle slip angle β.

[0138] Furthermore, as in the third embodiment, when the microcomputer 510 switches the controlled object of vehicle slip angle control in two ways based on the conditions that the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1, the controlled object can be an actuator different from that in the third embodiment. For example, the microcomputer 510 can control only the front wheel steering system 400 when the following conditions are not met: the absolute value of the vehicle slip angle β is greater than the first threshold βTH1 and less than the second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than the threshold αTH1. Furthermore, the microcomputer 510 can be either a front-wheel steering system 400 and a braking system 300, or a front-wheel steering system 400 and a rear-wheel braking system, when the absolute value of the vehicle slip angle β is greater than a first threshold βTH1 and less than a second threshold βTH2, and the absolute value of the vehicle slip angular velocity α is greater than a threshold αTH1.

[0139] Furthermore, in the control target switching process of the second embodiment shown in the flowcharts of Figures 14-16, and the control target switching process of the third embodiment shown in the flowcharts of Figures 19-20, the microcomputer 510 can compare the predicted vehicle slip angle βes with the first threshold βTH1 and the second threshold βTH2 instead of the vehicle slip angle β, and compare the predicted vehicle slip angular velocity αes with the threshold αTH1 instead of the vehicle slip angular velocity α.

[0140] Furthermore, the microcomputer 510 can stop vehicle slip angle control when the vehicle slip angle β falls below a set value. Furthermore, the microcomputer 510 can selectively switch the control target in vehicle slip angle control, which is used to bring the vehicle slip angle β closer to the reference angle βTH, based on physical quantities resulting from the tire force of the vehicle 100, such as tire slip angle and yaw rate.

[0141] Furthermore, in the second embodiment, if the vehicle 100 is a rear-wheel drive vehicle and the drive unit 310 provides driving force only to the rear wheels, the microcomputer 510 can output a rear-wheel drive control signal in step S612-2 of Figure 15. Furthermore, in the second embodiment, if the vehicle 100 is a front-wheel drive vehicle and the drive unit 310 provides driving force only to the front wheels, the microcomputer 510 can be configured not to perform driving force control for each wheel in step S612-2 in Figure 15 and step S615-2 in Figure 16. [Explanation of Symbols]

[0142] 100...Vehicle, 200...Vehicle control system, 300...Braking system (brake / drive actuator, brake actuator), 400...Front wheel steering system (steering actuator), 500...Vehicle control device, 510...Microcomputer (control unit, control section), 520...Steering assistance request value calculation unit, 530...Braking assistance request value calculation unit, 540...Control signal calculation unit, 550...Vehicle slip angle calculation unit, 560...Control device selection unit, β...Vehicle slip angle (first angle)

Claims

1. A vehicle control device provided in a vehicle having a braking actuator that applies braking force to the wheels and a steering actuator that steers the wheels, The control unit of the aforementioned vehicle control device is A first angle is obtained, which is an estimated value of the angle formed by the orientation of the vehicle and the direction of travel of the vehicle. Obtain an avoidance path to avoid an object located in front of the aforementioned vehicle, When performing path following control to drive the vehicle along the avoidance path, a first angle control is performed to bring the first angle closer to a predetermined reference angle set to zero or near zero. The control target of the first angle control is configured to selectively switch between the steering actuator, or both the braking / driving actuator and the steering actuator, based on the first angle and the angular velocity of the first angle, which are physical quantities resulting from the tire force of the vehicle. The control unit is The selection conditions for selecting the control target for the first angle control are that the absolute value of the first angle is greater than a predetermined first angle threshold which is greater than the predetermined reference angle, the absolute value of the first angle is less than a predetermined second angle threshold which is greater than the predetermined first angle threshold, and the absolute value of the angular velocity of the first angle is less than a predetermined angular velocity threshold which is greater than zero. If the above selection conditions are met, both the braking / driving actuator and the steering actuator are selected as the control targets for the first angle control. If the above selection conditions are not met, the steering actuator is selected as the control target for the first angle control. Vehicle control device.

2. A vehicle control device according to claim 1, The control unit is When the longitudinal speed of the vehicle is greater than a predetermined longitudinal speed threshold for determining the estimation accuracy of the first angle, the first angle and the angular velocity of the first angle are acquired. Vehicle control device.

3. A vehicle control device according to claim 1, The control unit is When the steering angle operated by the driver of the vehicle is greater than a predetermined steering angle threshold, and the angular velocity of the steering angle is greater than a predetermined steering angular velocity threshold, the system determines that the driver is performing a steering operation and executes the first angle control. Vehicle control device.

4. A vehicle control device according to claim 1, The control unit is After initiating the first angle control, the first angle control is terminated when the vehicle's speed falls below a predetermined vehicle speed threshold set in advance as a condition for terminating the first angle control. Vehicle control device.

5. A vehicle control method performed by a control unit provided in a vehicle having a braking actuator that applies braking force to a wheel and a steering actuator that steers the wheel, A first angle is obtained, which is an estimated value of the angle formed by the orientation of the vehicle and the direction of travel of the vehicle. Obtain an avoidance path to avoid an object located in front of the aforementioned vehicle, When performing path following control to drive the vehicle along the avoidance path, a first angle control is performed to bring the first angle closer to a predetermined reference angle set to zero or near zero. The control target of the first angle control is selectively switched to either the steering actuator or both the braking / driving actuator and the steering actuator, based on the first angle and the angular velocity of the first angle, which are physical quantities resulting from the tire force of the vehicle. The selection conditions for selecting the control target for the first angle control are that the absolute value of the first angle is greater than a predetermined first angle threshold which is greater than the predetermined reference angle, the absolute value of the first angle is less than a predetermined second angle threshold which is greater than the predetermined first angle threshold, and the absolute value of the angular velocity of the first angle is less than a predetermined angular velocity threshold which is greater than zero. If the above selection conditions are met, both the braking / driving actuator and the steering actuator are selected as the control targets for the first angle control. If the above selection conditions are not met, the steering actuator is selected as the control target for the first angle control. Vehicle control method.

6. A braking and driving actuator that applies braking and driving force to the wheels of a vehicle, A steering actuator for steering the aforementioned wheels, A control unit provided in the aforementioned vehicle, A first angle is obtained, which is an estimated value of the angle formed by the orientation of the vehicle and the direction of travel of the vehicle. Obtain an avoidance path to avoid an object located in front of the aforementioned vehicle, When performing path following control to drive the vehicle along the avoidance path, a first angle control is performed to bring the first angle closer to a predetermined reference angle set to zero or near zero. The control target of the first angle control is configured to selectively switch between the steering actuator, or both the braking / driving actuator and the steering actuator, based on the first angle and the angular velocity of the first angle, which are physical quantities resulting from the tire force of the vehicle. The selection conditions for selecting the control target for the first angle control are that the absolute value of the first angle is greater than a predetermined first angle threshold which is greater than the predetermined reference angle, the absolute value of the first angle is less than a predetermined second angle threshold which is greater than the predetermined first angle threshold, and the absolute value of the angular velocity of the first angle is less than a predetermined angular velocity threshold which is greater than zero. If the above selection conditions are met, both the braking / driving actuator and the steering actuator are selected as the control targets for the first angle control. If the above selection conditions are not met, the steering actuator is selected as the control target for the first angle control. The control unit and, A vehicle control system equipped with the following features.

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