Vehicle control method and vehicle control device

Abstract

To reduce a risk that occurs when tires are unable to generate a required braking and driving force difference between wheels while controlling a turning motion of an own vehicle by generating the braking and driving force difference between wheels of the own vehicle.SOLUTION: A vehicle control method includes: determining whether or not each wheel has a margin in tire force (S5 and S6); generating a braking and driving force difference to eliminate a deviation between a target yaw rate and an actual yaw rate when at least one wheel has the margin in the tire force and the other wheels have no margin in the tire force (S7); and generating braking force that generates longitudinal force in an own vehicle on the wheels in preference to braking force that generates yaw moment in the own vehicle when all wheels have no margin in the tire force (S8).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vehicle control method and a vehicle control device. [Background technology]

[0002] The vehicle skidding prevention control described in Patent Document 1 applies a braking force difference to the left and right wheels based on the difference between the target yaw rate and the actual yaw rate so as to reduce the difference between the actual yaw rate and the target yaw rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-165216 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is not always possible for the tires to actually generate the desired braking force difference calculated in the skid prevention control described in Patent Document 1. If the tires are unable to generate the required braking force difference, there is a risk that, for example, the vehicle behavior may become unstable or the vehicle may come too close to the lane boundary. The present invention aims to reduce the risk that occurs when tires are unable to generate the required braking / driving force difference when controlling the turning movement of a vehicle by generating a braking / driving force difference between the wheels of the vehicle. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a vehicle control method for controlling turning motion of a host vehicle by generating a braking / driving force difference between wheels of the host vehicle. The vehicle control method detects or estimates an actual yaw rate of the host vehicle, calculates or estimates a target yaw rate of the host vehicle, calculates or estimates a tire action force which is a resultant of a tire lateral force and a tire longitudinal force acting on each tire of the wheel, calculates or estimates a maximum tire force which is a maximum value of the resultant tire lateral force and tire longitudinal force which can be generated by each tire of the wheel, compares the tire action force with the maximum tire force for each wheel, determines that there is a tire force reserve if the tire action force is equal to or less than the maximum tire force, determines that there is no tire force reserve if the tire action force is greater than the maximum tire force, generates a braking / driving force difference at the wheel that eliminates a deviation between the target yaw rate and the actual yaw rate if at least one wheel has a tire force reserve but the other wheels do not, and generates a braking force at the wheel that generates a longitudinal force at the host vehicle in preference to a braking force that generates a yaw moment in the host vehicle if none of the wheels have a tire force reserve. [Effects of the Invention]

[0006] According to the present invention, when controlling the turning movement of a vehicle by generating a braking / driving force difference between the wheels of the vehicle, the risk of the tires being unable to generate the required braking / driving force difference can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a vehicle control device according to an embodiment; [Figure 2] FIG. 2 is a block diagram illustrating an example of a functional configuration of a controller according to the first embodiment. [Figure 3] FIG. 2 is a schematic diagram of tire acting forces and maximum tire forces. [Figure 4] FIG. 2 is a block diagram illustrating an example of a functional configuration of a braking / driving control calculation unit. [Figure 5] 3 is a flowchart illustrating an example of a vehicle control method according to the first embodiment. [Figure 6] FIG. 10 is a block diagram illustrating an example of a functional configuration of a controller according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic and may differ from the actual product. Furthermore, the embodiments of the present invention shown below are examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of component parts to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0009] (First embodiment) (composition) FIG. 1 is a diagram illustrating a schematic configuration example of a vehicle control device according to an embodiment. The host vehicle 1 includes a vehicle control device 10 that controls at least the driving force or braking force of the host vehicle 1. For example, the vehicle control device 10 may execute autonomous driving control, which controls the steering angle, driving force, and braking force of the host vehicle 1 based on the driving environment around the host vehicle 1, to automatically drive the host vehicle 1 without the involvement of a driver. Furthermore, for example, the vehicle control device 10 may execute driving assistance control, which assists the driver in driving the host vehicle 1, by controlling at least one of the steering angle, driving force, and braking force of the host vehicle 1. The driving assistance control may include, for example, automatic braking, lane keeping control, automatic speed control (for example, constant speed driving control, inter-vehicle control that maintains a target inter-vehicle distance from a leading vehicle, or leading vehicle following control), etc.

[0010] The vehicle control device 10 includes an ambient environment sensor 11, a vehicle sensor 12, a positioning device 13, a map database (map DB) 14, a navigation system 15, a controller 16, a steering actuator 17, an accelerator actuator 18, and a brake actuator 19.

[0011] The surrounding environment sensor 11 detects objects within a predetermined distance range from the host vehicle 1. The surrounding environment sensor 11 detects the surrounding environment of the host vehicle 1, such as the relative position of the host vehicle 1 and objects present around the host vehicle 1, the distance between the host vehicle 1 and the objects, and the direction in which the objects are present. The surrounding environment sensor 11 may include, for example, a camera that captures images of the surrounding environment of the host vehicle 1. The surrounding environment sensor 11 may also include a distance measuring device such as a laser range finder, radar, LiDAR (Light Detection and Ranging), or sonar. The surrounding environment sensor 11 outputs surrounding environment information, which is information on the detected surrounding environment of the host vehicle 1, to the controller 16.

[0012] The vehicle sensor 12 detects various information (vehicle information) of the host vehicle 1. For example, the vehicle sensor 12 may include a vehicle speed sensor that detects the vehicle speed V of the host vehicle 1, an acceleration sensor that detects the acceleration (including deceleration) of the host vehicle 1 in three axial directions, a steering angle sensor that detects the front wheel steering angle δf and the rear wheel steering angle δr of the host vehicle 1, and a yaw rate sensor that detects the yaw rate occurring in the host vehicle 1. The vehicle sensor 12 outputs vehicle state information to the controller 16. Note that if the host vehicle 1 does not have a rear wheel steering mechanism, the steering angle sensor detects only the front wheel steering angle δf. In the following description, the front wheel steering angle δf and the rear wheel steering angle δr may be collectively referred to as the "steering angle δ." The yaw rate detected by the yaw rate sensor may be referred to as the "actual yaw rate γa."

[0013] The positioning device 13 measures the current position of the vehicle 1. The positioning device 13 includes, for example, a Global Navigation System (GNSS) receiver. The GNSS receiver is, for example, a Global Positioning System (GPS) receiver, and receives radio waves from multiple navigation satellites to measure the current position of the vehicle 1. The positioning device 13 may also include an inertial navigation system. The positioning device 13 outputs current position information, which is information on the measured current position and attitude, to the controller 16. Map data is stored in the map database 14. The map data stored in the map database 14 may be high-precision map data suitable for use as map data for navigation or maps for automatic driving, for example.

[0014] The navigation system 15 recognizes the current position of the vehicle 1 using the positioning device 13 and obtains map information for the current position from the map database 14. The navigation system 15 accepts a destination input operation by the occupant, sets a target driving route from the current position of the vehicle 1 to the destination, and provides route guidance to the occupant along this target driving route. The navigation system 15 also outputs information about the set target driving route to the controller 16. When performing autonomous driving control, the controller 16 automatically drives the vehicle 1 so that the vehicle 1 travels along the target driving route set by the navigation system 15.

[0015] Steering actuator 17 controls the steering direction and steering amount of the steering mechanism of vehicle 1 in response to a control signal from controller 16. For example, if the steering mechanism of vehicle 1 is equipped with a steer-by-wire system in which the steering wheel and steered wheels are mechanically separated, steering actuator 17 may be a steering motor that generates a steering force to turn the steered wheels. Also, for example, if the steering mechanism is an electric power steering system that applies a steering assist force to assist the driver in steering the steering wheel, steering actuator 17 may be a steering assist motor that generates a steering assist force. The accelerator actuator 18 controls the accelerator opening of the drive device, which is an engine or a drive motor, in response to a control signal from the controller 16. The brake actuator 19 operates the braking device in response to a control signal from the controller 16.

[0016] The controller 16 is an electronic control unit (ECU) that performs autonomous driving control and driving assistance control of the host vehicle 1. The controller 16 includes a processor 16a and peripheral components such as a storage device 16b. The processor 16a may be, for example, a central processing unit (CPU) or a micro-processing unit (MPU). The storage device 16b may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device 16b may include memories such as a register, a cache memory, and a read-only memory (ROM) and a random access memory (RAM) used as a main storage device. The functions of the controller 16 described below are realized, for example, by the processor 16a executing a computer program stored in the storage device 16b.

[0017] The controller 16 may be formed by dedicated hardware for executing each of the information processes described below. For example, the controller 16 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit, such as a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0018] 2 is a block diagram of an example of the functional configuration of the controller 16 in the first embodiment. In the first embodiment, the functional configuration of the controller 16 when the controller 16 drives the host vehicle 1 using autonomous driving control will be described. The controller 16 includes a target trajectory calculation unit 30, a target calculation unit 31, a vehicle control calculation unit 32, a vehicle behavior determination unit 33, and a braking / driving control calculation unit 34.

[0019] The target trajectory calculation unit 30 acquires route information for the route along which the vehicle 1 is traveling. For example, the target trajectory calculation unit 30 acquires, as route information, ambient environment information acquired from the ambient environment sensor 11 and high-precision map data from the map database 14. Based on the acquired route information, the target travel route set by the navigation system 15, and the current position measured by the positioning device 13, the target trajectory calculation unit 30 calculates a target travel trajectory and a target vehicle speed as control targets for autonomous driving control for the vehicle 1 to travel along the target travel route.

[0020] For example, the target trajectory calculation unit 30 may generate a route space map that represents the route around the host vehicle 1 and the presence or absence of objects, and a risk map that quantifies the risk of the driving field, and calculate a target driving trajectory and target vehicle speed for the host vehicle 1 based on the motion characteristics of the host vehicle 1, vehicle state information, the route space map, and the risk map. For example, the target trajectory calculation unit 30 may calculate a target vehicle speed profile that represents the target vehicle speed at a sequence of points on the target driving trajectory.

[0021] The target calculation unit 31 calculates the target longitudinal force Fxt, target lateral force Fyt, target yaw rate γt, target sideslip angle βt, and target yaw moment Mzt required for the host vehicle 1 to travel at the target vehicle speed along the target travel path. For example, the target calculation unit 31 may calculate the longitudinal force and lateral force required for the mass point of the host vehicle 1 to travel at the target vehicle speed along the target travel trajectory as the target longitudinal force Fxt and the target lateral force Fyt, respectively. Also, the target calculation unit 31 may calculate the target yaw rate γt, the target sideslip angle βt, and the target yaw moment Mzt based on the following equations (1) to (9).

[0022]

number

[0023] In equations (1) to (9), m is the weight of the host vehicle 1, Iz is the yaw moment of inertia, l is the wheel base, lf and lr are the distances from the center of gravity of the host vehicle 1 to the front and rear axles, Cf and Cr are the equivalent cornering powers of the front and rear wheels, A is the stability factor, and s is the Laplace operator.

[0024] The vehicle control calculation unit 32 calculates the target steering angle and the target braking / driving force of each wheel based on the target longitudinal force Fxt, target lateral force Fyt, target yaw rate γt, target sideslip angle βt, and target yaw moment Mzt calculated by the target calculation unit 31. For example, the vehicle control calculation unit 32 calculates a target steering angle for realizing a target yaw rate γt and a target braking / driving force for realizing a target longitudinal force Fxt.

[0025] The vehicle control calculation unit 32 may distribute the control amount for achieving the target yaw rate γt to braking force, steering force, and driving force. In this case, in order to achieve the target yaw rate γt, not only the steering angle δ but also the addition of a yaw moment due to the braking / driving force of each wheel and the influence of wheel load fluctuations may be actively used, and for this purpose, information such as the target sideslip angle βt and the target yaw moment Mzt may also be used. The vehicle control calculation unit 32 controls the steering actuator so that the steering angle δ of the steered wheels of the host vehicle 1 becomes the target steering angle. In addition, the vehicle control calculation unit 32 controls the accelerator actuator 18 or the brake actuator 19 so that the target braking / driving force is generated at each wheel.

[0026] The vehicle behavior determination unit 33 determines whether the running state of the host vehicle 1 is in a controllable range where the tires of all wheels have remaining capacity, or in an uncontrollable range where at least one tire has no remaining capacity. In this specification, "a state in which the tire has remaining force" refers to a state in which the tire acting force acting on the tire is equal to or less than the maximum tire force that each tire can generate. The "tire acting force" refers to the resultant force of the tire lateral force and tire longitudinal force acting on the tire, and the "maximum tire force" refers to the maximum value of the resultant force of the tire lateral force and tire longitudinal force that each tire can generate (i.e., the tire friction circle).

[0027] The controllable region is a state in which the target yaw moment calculated from the acceleration at the mass point of the vehicle 1 using a two-wheel model of the vehicle 1 can actually be generated, and is a state in which the cornering power is not saturated with the increase in tire slip angle of the tires of each wheel. When the driving state of the host vehicle 1 is within the controllable range, the controller 16 does not perform control to stabilize the vehicle behavior of the host vehicle 1 using the braking / driving control calculation unit 34 described later, but instead performs vehicle control to drive the host vehicle 1 by following the target driving trajectory using the vehicle control calculation unit 32.

[0028] For example, the vehicle behavior determination unit 33 may determine that the running state of the host vehicle 1 is in a controllable range when the yaw rate deviation between the target yaw rate γt and the actual yaw rate γα is less than a threshold, and may determine that the running state of the host vehicle 1 is in an uncontrollable range when the yaw rate deviation is less than the threshold. Also, for example, the vehicle behavior determination unit 33 may calculate a stability factor, and determine that the running state of the host vehicle 1 is in an uncontrollable range when the stability factor deviates from a steady value by a certain amount or more, and may determine that the running state of the host vehicle 1 is in a controllable range in other cases.

[0029] On the other hand, when the driving state of the vehicle 1 is in an uncontrollable zone, the vehicle behavior determination unit 33 compares the tire acting force with the maximum tire force for each wheel to determine whether there is a tire force reserve for each wheel. Fig. 3 is a schematic diagram of tire acting forces and maximum tire forces. For simplicity, the example in Fig. 3 uses a model in which the left and right front wheels and the left and right rear wheels are each represented by one wheel, but it is also possible to determine separately whether there is spare tire force for each of the left front wheel, right front wheel, left rear wheel, and right rear wheel.

[0030] 3, symbol Faf is the tire force acting on the front wheels, symbol Far is the tire force acting on the rear wheels, symbol μf×Wf is the maximum tire force on the front wheels, and symbol μr×Wr is the maximum tire force on the front wheels. Symbols μf and μr are the road friction coefficients of the front and rear wheels, respectively, and Wf and Wr are the front axle load and rear axle load, respectively.

[0031] For example, the vehicle behavior determination unit 33 may calculate the front axle load Wf and the rear axle load Wr based on the following equations (10) to (13). Wf=Wfs+ΔW …(10) Wr = Wrs - ΔW … (11) ΔW=(B+A×χ)×Fx …(12) Fx = m × Gx …(13) In the above equation, symbol Wfs is the static load on the front wheels, symbol Wrs is the static load on the rear wheels, and symbol χ is the front wheel braking / driving distribution ratio. The front wheel braking / driving distribution ratio χ may use different values ​​when braking and when driving, or may be a dynamically changing variable. Symbols A and B are constants determined from the vehicle characteristics of the host vehicle 1. Symbols A and B may use different values ​​when braking and when driving. Symbol Fx is the longitudinal force acting on the host vehicle 1, and symbol Gx is the longitudinal acceleration detected by the vehicle sensor 12.

[0032] The vehicle behavior determination unit 33 also estimates road surface friction coefficients μf and μr for the front and rear wheels. For example, the vehicle behavior determination unit 33 may assume that the road surface friction coefficients μf = μr = μ for the front and rear wheels are equal to each other, and estimate the road surface friction coefficient μ from the longitudinal acceleration Gx and lateral acceleration Gy detected by the vehicle sensor 12 based on the following equation (14).

[0033]

number

[0034] The vehicle behavior determination unit 33 estimates the tire friction circle of the front wheels (μf×Wf) as the maximum tire force of the front wheels, and estimates the tire friction circle of the rear wheels (μr×Wr) as the maximum tire force of the rear wheels. On the other hand, the vehicle behavior determination unit 33 estimates tire lateral forces Fyf and Fyr acting on the front and rear tires, respectively, based on the following equations (15) to (18).

[0035]

number

[0036] Furthermore, the vehicle behavior determination unit 33 estimates tire longitudinal forces Fxf and Fxr acting on the front and rear tires, respectively, based on the following equations (19) and (20). Fxf = χ × Fx …(19) Fxr=(1-χ)×Fx …(20) The vehicle behavior determination unit 33 estimates the resultant force of the front wheel tire lateral force Fyf and the tire longitudinal force Fxf as the tire action force Faf, and estimates the resultant force of the rear wheel tire lateral force Fyr and the tire longitudinal force Fxr as the tire action force Far, based on the following equations (21) and (22).

[0037]

number

[0038] The vehicle behavior determination unit 33 determines that there is no tire force reserve when the maximum tire forces (μf×Wf) and (μr×Wr) are smaller than or equal to the tire acting forces Faf and Far. For example, if the following equation (23) is satisfied, it determines that there is no tire force reserve in the front wheels, and if the following equation (23) is not satisfied, it determines that there is tire force reserve in the front wheels. Also, if the following equation (24) is satisfied, it determines that there is no tire force reserve in the front wheels, and if the following equation (24) is not satisfied, it determines that there is tire force reserve in the rear wheels. (μf×Wf) <Faf…(23) (μr × Wr) <Far…(24)

[0039] Alternatively, for example, the vehicle behavior determination unit 33 may determine that there is no tire force reserve when the ratios (Faf / (μf×Wf)), (Far / (μr×Wr)) of the tire acting forces Faf, Far to the maximum tire forces (μf×Wf), (μr×Wr) are equal to or greater than a certain percentage. For example, the vehicle behavior determination unit 33 may determine that there is no tire force reserve when the certain percentage is a value greater than 1.

[0040] The vehicle behavior determination unit 33 determines that the running state of the host vehicle 1 is in the first uncontrollable region when either the front wheels or the rear wheels have tire force reserve, and either the front wheels or the rear wheels do not have tire force reserve. The first uncontrollable region is a state in which the cornering power of at least one wheel of the host vehicle 1 has not saturated with respect to an increase in tire slip angle, and the cornering power of the other wheels has saturated with respect to an increase in tire slip angle.

[0041] On the other hand, when there is no tire force reserve in both the front and rear wheels (i.e., in all wheels), the vehicle behavior determination unit 33 determines that the running state of the host vehicle 1 is in the second uncontrollable region. The second uncontrollable region is a state in which the cornering power is saturated with respect to an increase in the tire slip angle in all wheels of the host vehicle 1. The vehicle behavior determination unit 33 outputs a determination result signal Sb, which indicates the determination result of the running state of the host vehicle 1, to the braking / driving control calculation unit .

[0042] When it is determined that the traveling state of the host vehicle 1 is in the first uncontrollable region, the braking / driving control calculation unit 34 performs intervention control to generate a yaw moment by using the braking / driving force difference between the wheels to eliminate the deviation of the actual yaw rate γa from the target yaw rate γt. For example, the braking / driving control calculation unit 34 may generate the yaw moment by using the braking / driving force difference between the wheels through conventional skid prevention control (ESC: Electronic Stability Control).

[0043] 4 is a block diagram of an example of the functional configuration of braking / driving control calculation unit 34. Braking / driving control calculation unit 34 includes a yaw rate deviation calculation unit 40, a sideslip angle deviation calculation unit 41, a sideslip angle velocity calculation unit 42, controllers 43, 44, and 45, an adder 46, and a braking / driving command calculation unit 47. The yaw rate deviation calculation unit 40 calculates the yaw rate deviation Δγ of the actual yaw rate γa with respect to the target yaw rate γt.

[0044] The braking / driving control calculation unit 34 may calculate a yaw rate expected value γe, which is an expected value of a yaw rate that may occur in the host vehicle 1 when it is assumed that the tire characteristics of each wheel are linear, based on the vehicle speed V and steering angle δ detected by the vehicle sensor 12. The yaw rate deviation calculation unit 40 may calculate the deviation of the actual yaw rate γa from the yaw rate expected value γe as a yaw rate deviation Δγ. For example, the braking / driving control calculation unit 34 may calculate the yaw rate expected value γe based on the following equation (25) that conforms to a two-wheel model of the host vehicle 1.

[0045]

number

[0046] The slip angle deviation calculation unit 41 estimates the slip angle deviation Δβ of the actual slip angle from the target slip angle based on the actual yaw rate γa, the steering angle δ, and the vehicle speed V. The slip angle velocity calculation unit 42 estimates the slip angle velocity dβ, which is the derivative of the actual slip angle, based on the actual yaw rate γa, the vehicle speed V, and the lateral acceleration Gy.

[0047] Controllers 43, 44, and 45 calculate the first yaw moment component Mz1, the second yaw moment component Mz2, and the third yaw moment component Mz3, respectively, by at least one of proportional action control (I control), integral action control (P control), and differential action control (D control) for the yaw rate deviation Δγ, the sideslip angle deviation Δβ, and the sideslip angular velocity dβ. The gains of these I control, P control, and D control may be variable gains that change according to the estimated value of the road surface friction coefficient μ and the vehicle speed. An adder 46 calculates the sum of the first to third yaw moment components Mz1 to Mz3 as the braking / driving control target yaw moment Mztv=Mz1+Mz2+Mz3.

[0048] The braking / driving control calculation unit 34 calculates a target left front wheel braking / driving force FxFL, a target right front wheel braking / driving force FxFR, a target left rear wheel braking / driving force FxRL, and a target right rear wheel braking / driving force FxRR for generating a braking / driving control target yaw moment Mztv in the host vehicle 1. For example, the braking / driving control calculation unit 34 may calculate the target left front wheel braking / driving force FxFL, the target right front wheel braking / driving force FxFR, the target left rear wheel braking / driving force FxRL, and the target right rear wheel braking / driving force FxRR based on the relational expression in the following equation (26).

[0049] Mztv=(FxFL-FxFR)×Tf / 2+(FxRL-FxRR)×Tr / 2 …(26) In equation (26), Tf and Tr are the treads of the front and rear wheels, respectively. For example, when a counterclockwise yaw moment is generated only by the braking force of the left front wheel and the left rear wheel, the following equation (27) is obtained from the above equation (26).

[0050] Mztv=κ×Fx×Tf / 2+(1-κ)Fx×Tr / 2 …(27) In equation (27), κ and (1-κ) are the braking force distributions to the front and rear wheels. By rearranging equation (27) above, the left front wheel braking force FxFL and the left rear wheel braking force FxRL can be calculated based on the following equations (28) to (30). FxFL = κ × Fx …(28) FxRL=(1-κ)×Fx …(29) Fx=2×Mztv / {κ×Tf+(1-κ)×Tr}…(30)

[0051] The braking / driving control calculation unit 34 controls the accelerator actuator 18 or the brake actuator 19 so that the left front wheel, right front wheel, left rear wheel, and right rear wheel generate the target left front wheel braking / driving force FxFL, target right front wheel braking / driving force FxFR, target left rear wheel braking / driving force FxRL, and target right rear wheel braking / driving force FxRR, respectively. After starting the intervention control, the braking / driving control calculation unit 34 determines whether the actual traveling trajectory of the host vehicle 1 has converged to the target traveling trajectory. If it is determined that the actual traveling trajectory of the host vehicle 1 has converged to the target traveling trajectory, the braking / driving control calculation unit 34 ends the intervention control.

[0052] For example, the braking / driving control calculation unit 34 may determine that the actual traveling trajectory of the host vehicle 1 has converged to the target traveling trajectory when the yaw rate deviation Δγ, the sideslip angle deviation Δβ, and the lateral acceleration Gy are each less than a threshold value. Alternatively, for example, the braking / driving control calculation unit 34 may determine that the actual traveling trajectory of the host vehicle 1 has converged to the target traveling trajectory when the position deviation of the current position of the host vehicle 1 with respect to the target traveling trajectory is less than a threshold value.

[0053] On the other hand, when it is determined that the traveling state of the host vehicle 1 is in the second uncontrollable region, the braking / driving control calculation unit 34 generates a braking force on the wheels that decelerates the host vehicle 1. In other words, the braking / driving control calculation unit 34 controls the accelerator actuator 18 or the brake actuator 19 so that the wheels generate a braking force that generates a longitudinal force on the host vehicle 1 in preference to a braking force that generates a yaw moment on the host vehicle 1. By decelerating the host vehicle 1 in this way, an attempt is made to eliminate the state in which tire forces are saturated at all wheels (that is, to restore a state in which at least one wheel generates tire force).

[0054] For example, the braking / driving control calculation unit 34 may control the accelerator actuator 18 or the brake actuator 19 so that the right wheel and the left wheel generate the same braking force. Alternatively, for example, the braking / driving control calculation unit 34 may use an existing anti-lock brake system (ABS) to cause the wheels to generate braking force that decelerates the host vehicle 1. For example, the braking / driving control calculation unit 34 may control the accelerator actuator 18 or the brake actuator 19 so as to reduce the amount by which the actual slip ratio of each wheel exceeds a predetermined slip ratio (for example, an ideal slip ratio) (i.e., so that the actual slip ratio of each wheel is equal to or less than the ideal slip ratio).

[0055] (operation) FIG. 5 is a flowchart of an example of the vehicle control method according to the first embodiment. In step S1, the vehicle sensor 12 detects the actual yaw rate γa of the host vehicle 1. In step S2, the target calculation unit 31 calculates the target yaw rate γt. In step S3, the vehicle behavior determination unit 33 calculates or estimates the tire acting force for each wheel. In step S4, the vehicle behavior determination unit 33 calculates or estimates the maximum tire force for each wheel.

[0056] In step S5, the vehicle behavior determination unit 33 compares the tire acting force with the maximum tire force to determine whether there is a tire force reserve for each wheel. If there is no tire force reserve for all wheels (step S6: N), the process proceeds to step S8. If there is a tire force reserve for at least one wheel (step S6: Y), the process proceeds to step S7.

[0057] In step S7, the braking / driving control calculation unit 34 performs intervention control to generate a yaw moment based on the braking / driving force difference between the wheels to eliminate the deviation of the actual yaw rate γa from the target yaw rate γt, and then the process ends. In step S8, the braking / driving control calculation unit 34 generates a braking force on the wheels that decelerates the host vehicle 1. That is, the braking force of each wheel is controlled so that the wheels generate a braking force that generates a longitudinal force on the host vehicle 1 in preference to a braking force that generates a yaw moment on the host vehicle 1. The process then ends.

[0058] (Second embodiment) In the second embodiment, a functional configuration of the controller 16 will be described for the case where the host vehicle 1 is being manually driven by a driver. The host vehicle 1 may be a manually driven vehicle that does not have an autonomous driving function. In this case, for example, the controller 16 may execute lane keeping control to control the steering of the host vehicle 1 so that the host vehicle 1 does not deviate from the driving lane. The controller may also perform automatic speed control (constant speed control, inter-vehicle distance control, and preceding vehicle following control) to automatically adjust the traveling speed of the host vehicle 1.

[0059] 5 is a block diagram showing an example of the functional configuration of the controller 16 in the second embodiment. The controller 16 in the second embodiment has a functional configuration similar to that in the first embodiment. Therefore, the same or similar components are denoted by the same reference numerals. When the vehicle 1 is being manually driven by the driver, the target trajectory calculation unit 30 recognizes the lane boundaries of the lane on which the vehicle 1 is traveling. For example, the target trajectory calculation unit 30 may recognize lane boundaries based on images captured by a camera of the vehicle sensor 12 or measurement results from a distance measurement device.

[0060] Furthermore, for example, the target trajectory calculation unit 30 may recognize lane boundaries based on the measurement results from the positioning device 13 and high-precision map data in the map database 14. The target trajectory calculation unit 30 calculates a target driving trajectory based on the recognized lane boundary. For example, the target trajectory calculation unit 30 may calculate a target driving trajectory that passes through the lane center position based on the left and right lane boundaries, or may calculate a target driving trajectory that passes through a position that is a predetermined distance away from either the left or right lane boundary. The target trajectory calculation unit 30 may set the target vehicle speed based on the amount of accelerator pedal operation and the amount of brake pedal operation by the driver. The target trajectory calculation unit 30 may also set the current vehicle speed of the host vehicle 1 as the target speed.

[0061] When the vehicle control device 10 is assisting the driver in steering operations through lane keeping control, the target trajectory calculation unit 30 may set a trajectory that serves as a target for the driving trajectory of the vehicle 1 in lane keeping control as the target driving trajectory. In lane keeping control, lane boundaries of the lane in which the vehicle 1 is traveling may be recognized, and a target trajectory of the lane keeping control may be calculated based on the recognized lane boundaries. The lane boundaries may be recognized based on images captured by the camera of the vehicle sensor 12 or measurement results from a distance measuring device, or may be recognized based on measurement results from the positioning device 13 and high-precision map data in the map database 14.

[0062] Furthermore, when the vehicle control device 10 assists the driver in steering operation by automatic speed control, the target vehicle speed may be set as the target vehicle speed for the traveling speed of the host vehicle 1 in the automatic speed control. For example, the target vehicle speed of the constant speed cruise control may be a preset set speed or speed limit. Also, for example, the target vehicle speed of the vehicle distance control or the preceding vehicle following control may be set so that the inter-vehicle distance between the host vehicle 1 and the preceding vehicle becomes a target inter-vehicle distance according to the vehicle speed, with the preset set speed or speed limit as the upper limit. The configurations and processing of the target calculation unit 31, the vehicle behavior determination unit 33, and the braking / driving control calculation unit 34 are the same as those in the first embodiment.

[0063] (Effects of the embodiment) (1) The vehicle control device 10 controls the turning movement of the host vehicle 1 by generating a difference in braking / driving force between the wheels of the host vehicle 1. The vehicle control device 10 detects or estimates the actual yaw rate of the vehicle 1, calculates a target yaw rate for the vehicle 1, calculates or estimates a tire action force, which is the resultant of the tire lateral force and tire longitudinal force acting on each tire of the wheel, calculates or estimates a maximum tire force, which is the maximum value of the resultant tire lateral force and tire longitudinal force that can be generated by each tire of the wheel, compares the tire action force with the maximum tire force for each wheel, determines that there is spare tire force if the tire action force is less than the maximum tire force, determines that there is no spare tire force if the tire action force is greater than the maximum tire force, generates a braking / driving force difference in the wheel that eliminates the deviation between the target yaw rate and the actual yaw rate if there is spare tire force in at least one wheel and no spare tire force in the other wheels, and generates a braking force in the wheel that generates a longitudinal force in the vehicle 1 in preference to a braking force that generates a yaw moment in the vehicle 1 if there is no spare tire force in any of the wheels. This reduces the risk that the tires will not be able to generate the necessary difference in braking / driving force when controlling the turning movement of the vehicle 1 by generating a difference in braking / driving force between the wheels of the vehicle 1.

[0064] (2) The vehicle 1 may be an autonomous vehicle that generates a target driving route based on a destination set by a user and the current position of the vehicle 1, and drives along the target driving route through autonomous driving control. This reduces the risk that the tires will be unable to generate the required braking / driving force difference when controlling the turning movement of the vehicle 1 by generating a braking / driving force difference between the wheels of the vehicle 1 during autonomous driving control.

[0065] (3) The controller 16 may compare the size of the tire friction circle of the tire of the wheel with the tire acting force, and determine that there is no tire force reserve if the tire friction circle is smaller than or equal to the tire acting force. This allows for an appropriate determination of whether or not there is tire force reserve. (4) It may be determined that there is no tire force reserve when the ratio of the tire acting force to the size of the tire friction circle of the tire of the wheel is equal to or greater than a certain percentage. For example, the certain percentage may be set to a value greater than 1. This allows for an appropriate determination of whether or not there is tire force reserve.

[0066] (5) The controller 16 may calculate the size of the tire friction circle from the road friction coefficient and the wheel load. This allows the size of the tire friction circle to be calculated appropriately. (6) The controller 16 may calculate the tire lateral force and tire longitudinal force acting on the tire of the wheel based on the measured values ​​of the yaw rate, longitudinal acceleration, and lateral acceleration of the host vehicle 1 and the vehicle specifications of the host vehicle 1, and may calculate the tire action force by combining the tire lateral force and tire longitudinal force. This allows the tire action force acting on the tire to be calculated appropriately. [Explanation of symbols]

[0067] 1... host vehicle, 10... vehicle control device, 11... ambient environment sensor, 12... vehicle sensor, 13... positioning device, 14... map database, 15... navigation system, 16... controller, 16a... processor, 16b... storage device, 17... steering actuator, 18... accelerator actuator, 19... brake actuator, 30... target trajectory calculation unit, 31... target calculation unit, 32... vehicle control calculation unit, 33... vehicle behavior determination unit, 34... braking / driving control calculation unit, 40... yaw rate deviation calculation unit, 41... sideslip angle deviation calculation unit, 42... sideslip angle velocity calculation unit, 43 to 45... controller, 46... adder, 47... braking / driving command calculation unit

Claims

1. A vehicle control method for controlling a turning movement of a host vehicle by generating a braking / driving force difference between wheels of the host vehicle, comprising: Detecting or estimating an actual yaw rate of the host vehicle; calculating a target yaw rate of the host vehicle; calculating or estimating a tire acting force which is a resultant of a tire lateral force and a tire longitudinal force acting on each tire of the wheel; calculating or estimating a maximum tire force that is a maximum value of a resultant force of tire lateral force and tire longitudinal force that can be generated by each tire of the wheel; comparing the tire acting force with the maximum tire force for each wheel, determining that there is a tire force reserve when the tire acting force is equal to or less than the maximum tire force, and determining that there is no tire force reserve when the tire acting force is greater than the maximum tire force; When at least one of the wheels has a tire force reserve and the other wheels have no tire force reserve, the braking / driving force difference is generated in the wheel to eliminate the deviation between the target yaw rate and the actual yaw rate, When there is no tire force remaining in any of the wheels, a braking force that generates a longitudinal force on the host vehicle is generated on the wheels in preference to a braking force that generates a yaw moment on the host vehicle. A vehicle control method comprising:

2. 2. The vehicle control method according to claim 1, wherein the vehicle is an autonomous vehicle that generates a target driving route based on a destination set by a user and a current position of the vehicle, and drives along the target driving route by autonomous driving control.

3. comparing the size of the tire friction circle of the tire of the wheel with the tire acting force; When the tire friction circle is smaller than or equal to the tire acting force, it is determined that there is no tire force reserve.

2. The vehicle control method according to claim 1.

4. 2. The vehicle control method according to claim 1, wherein it is determined that there is no tire force reserve when the ratio of the tire acting force to the size of the tire friction circle of the tire of the wheel is equal to or greater than a certain percentage.

5. 5. The vehicle control method according to claim 4, wherein the fixed ratio is greater than one.

6. 6. The vehicle control method according to claim 3, wherein the size of the tire friction circle is calculated from a road friction coefficient and a wheel load.

7. The vehicle control method according to any one of claims 3 to 5, characterized in that a tire lateral force and a tire longitudinal force acting on a tire of the wheel are calculated based on measured values ​​of a yaw rate, a longitudinal acceleration, and a lateral acceleration of the host vehicle and vehicle specifications of the host vehicle, and the tire acting force is calculated by combining the tire lateral force and the tire longitudinal force.

8. A vehicle control device that generates a braking / driving force difference between wheels of a host vehicle to control a turning movement of the host vehicle, a sensor for detecting an actual yaw rate of the host vehicle or a process for estimating the actual yaw rate; a controller that performs a process of calculating a target yaw rate of the vehicle, a process of calculating or estimating a tire action force which is a resultant of a tire lateral force and a tire longitudinal force acting on each tire of the wheel, a process of calculating or estimating a maximum tire force which is a maximum value of a resultant of a tire lateral force and a tire longitudinal force which can be generated by each tire of the wheel, a process of comparing the tire action force with the maximum tire force for each wheel, and determining that there is a tire force reserve when the tire action force is equal to or less than the maximum tire force, and determining that there is no tire force reserve when the tire action force is greater than the maximum tire force, a process of controlling the braking / driving forces of the wheels to generate the braking / driving force difference which eliminates the deviation between the target yaw rate and the actual yaw rate when at least one of the wheels has a tire force reserve and the other wheels do not, and a process of controlling the braking forces of the wheels to generate a braking force which generates a longitudinal force on the vehicle in preference to a braking force which generates a yaw moment on the vehicle when none of the wheels has a tire force reserve; A vehicle control device characterized by:

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