Vehicle behavior control device

Abstract

To provide a vehicle behavior control device capable of appropriately controlling behavior of a four-wheel vehicle with a simple configuration.SOLUTION: A vehicle behavior control device 10 includes an actuator group 26 and a vehicle behavior controller 12 for controlling operation of the actuator group 26. The vehicle behavior controller 12 applies a target motion to a two-wheel model 50 to calculate respective velocity vectors VECf and VECr of a front wheel 40 and a rear wheel 42, converts the velocity vectors VECf and VECr into a centroid behavior represented by a velocity vector VECg and a yaw rate Θ at a centroid Pg of the vehicle, calculates a turning angle and braking / driving force for each of the four wheels on the basis of the centroid behavior, and controls the operation of the actuator group 26 so that each of the four wheels outputs the turning angle and the braking / driving force that are calculated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present specification discloses a vehicle behavior control device for controlling the behavior of a vehicle having four wheels. [Background technology]

[0002] Many logics have been proposed for analyzing the behavior of vehicles with four wheels. However, in the case of a four-wheeled vehicle, the four wheels behave differently from one another. For example, the tire slip angle differs from wheel to wheel. This makes it difficult to build computational logic for analyzing the behavior of a four-wheeled vehicle. Even if such computational logic could be built, there was the problem of the enormous amount of calculation required.

[0003] One possible solution is to analyze vehicle behavior using a two-wheel model or a simplified model that ignores tire slip angle. However, these simplified models do not take into account ground load or tire slip angle. Therefore, in order to calculate command values ​​for an actual vehicle from the steering angle and braking / driving force obtained from an analysis using the simplified model, it is necessary to build a separate calculation logic for command values ​​that takes ground load and tire slip angle into account. Building such calculation logic increases development time and costs.

[0004] Patent Document 1 discloses a technology that calculates six components of force at the center of gravity of a vehicle from the slip angle, yaw rate, and yaw acceleration at the center of gravity of the vehicle, calculates three-component tire forces for each of the four wheels from the six-component force at the center of gravity, and drives an actuator based on the obtained three-component tire forces. By using this technology, it is possible to appropriately control the drive of each of the four wheels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-165535 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology of Patent Document 1 uses the slip angle at the center of gravity of the vehicle as input, etc. Therefore, the analysis results using the simple model could not be used as input for the device described in Patent Document 1. As a result, there has not been a technology in the past that can appropriately control the behavior of a four-wheeled vehicle with a simple configuration.

[0007] Therefore, this specification discloses a vehicle behavior control device that can appropriately control the behavior of a four-wheel vehicle with a simple configuration. [Means for solving the problem]

[0008] The vehicle behavior control device disclosed in this specification comprises: an actuator group including one or more actuators configured to drive a vehicle having four wheels; and a vehicle behavior controller that controls the operation of the actuator group, wherein the vehicle behavior controller is configured to: apply a target motion to a two-wheel model that simulates the vehicle as a two-wheeled vehicle, calculate a velocity vector for each of the front and rear wheels required to obtain the target motion, convert the velocity vector for each of the front and rear wheels into a center-of-gravity behavior expressed by a velocity vector and yaw rate at the center of gravity of the vehicle, calculate a steering angle and braking / driving force for each of the four wheels based on the center-of-gravity behavior, and control the operation of the actuator group so that each of the four wheels outputs the calculated steering angle and braking / driving force.

[0009] Because a two-wheel model is used, the velocity vectors of the front and rear wheels can be calculated by simple calculations. Furthermore, by converting the velocity vectors of the front and rear wheels into velocity vectors and yaw rates at the center of gravity of the vehicle, the six-component force processing at the center of gravity proposed in Patent Document 1 and elsewhere can be utilized. As a result, the behavior of a four-wheel vehicle can be appropriately controlled with a simple configuration.

[0010] In this case, the velocity vector of the front wheels is expressed by a steering angle Bf of the front wheels and a speed Vf of the front wheels, the velocity vector of the rear wheels is expressed by a steering angle Br of the rear wheels and a speed Vr of the rear wheels, the center of gravity behavior is expressed by a vehicle body slip angle B at the center of the vehicle, a vehicle speed Vv, and a yaw rate Θ, and the vehicle behavior controller may calculate the center of gravity behavior by the following equations (3) to (5), where Lwb is the distance between the front wheels and the rear wheels, Lf is the distance between the front wheels and the center of gravity, and Lr is the distance between the rear wheels and the center of gravity.

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[0011] With this configuration, the velocity vectors of the front and rear wheels are appropriately converted into velocity vectors and yaw rates at the center of gravity of the vehicle.

[0012] Furthermore, the target motion may include a curvature Kf of a trajectory drawn by the front wheels, a curvature Kr of a trajectory drawn by the rear wheels, and a vehicle speed Vv, the velocity vector of the front wheels may be expressed by a steering angle Bf of the front wheels and a speed Vf=Vv of the front wheels, and the velocity vector of the rear wheels may be expressed by a steering angle Br of the rear wheels and a speed Vr=Vv of the rear wheels, and the vehicle behavior controller may calculate the velocity vector of the front wheels and the velocity vector of the rear wheels by solving the following equations (1) to (2), where Lwb is a distance between the front wheels and the rear wheels.

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[0013] With this configuration, the velocity vectors of the front and rear wheels required to obtain the desired motion can be calculated appropriately.

[0014] The one or more actuators may include at least a drive actuator that rotates the wheels, a brake actuator that generates braking force, a front wheel steering actuator that steers the front wheels, and a rear wheel steering actuator that steers the rear wheels.

[0015] By operating these actuators, the vehicle behavior can be controlled appropriately. [Effects of the Invention]

[0016] According to the technology disclosed in this specification, the behavior of a four-wheel vehicle can be appropriately controlled with a simple configuration. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a block diagram showing the configuration of a vehicle behavior control device. [Figure 2] FIG. 2 is a functional block diagram of a vehicle behavior controller. [Figure 3] FIG. 1 is a schematic diagram showing a two-wheel model. [Figure 4] FIG. 2 is a schematic diagram showing a rigid body model. [Figure 5] 10 is a flowchart showing processing by a six-component force control processing unit. DETAILED DESCRIPTION OF THE INVENTION

[0018] The configuration of the vehicle behavior control device 10 will be described below with reference to the drawings. Fig. 1 is a block diagram showing the configuration of the vehicle behavior control device 10. The vehicle behavior control device 10 shown in Fig. 1 is applied to a vehicle having four wheels.

[0019] The vehicle behavior control device 10 controls the behavior of the vehicle based on driving instructions. The driving instructions are instructions related to the acceleration / deceleration and steering of the vehicle. For example, the driver of the vehicle outputs driving instructions by operating the accelerator pedal, the brake pedal, and the steering wheel. The driver's operation amounts are detected by an accelerator pedal sensor 18, a brake pedal sensor 20, and a steering sensor 22, and input to the vehicle behavior controller 12 as driving instructions. Furthermore, when the vehicle is driving autonomously by an autonomous driving system 24, the autonomous driving system 24 outputs driving instructions. The autonomous driving system 24 is a system for performing automatic driving or advanced driving assistance. The autonomous driving system 24 includes multiple sensors and a computer, and automatically controls the acceleration / deceleration and steering of the vehicle.

[0020] The vehicle behavior controller 12 controls the behavior of the vehicle, particularly the behavior of the four wheels, based on driving instructions. The control by the vehicle behavior controller 12 will be described in detail later. The vehicle behavior controller 12 is physically a computer including a processor 14 and a memory 16. In FIG. 1, the vehicle behavior controller 12 is illustrated as a single computer. However, the vehicle behavior controller 12 may be configured from multiple physically separated computers. Also, part or all of the vehicle behavior controller 12 may function as part of the autonomous driving system 24. Furthermore, part of the vehicle behavior controller 12 may be located outside the vehicle. In this case, the vehicle behavior controller 12 has a wireless communication function.

[0021] The vehicle control actuator group 26 includes a plurality of actuators for controlling the behavior of the vehicle, such as a drive actuator 28, a brake actuator 30, a front wheel steering actuator 32, a rear wheel steering actuator 34, an active stabilizer 36, and an active suspension 38.

[0022] The drive actuator 28 controls the amount of air supplied to the engine (throttle opening) in response to a control command from the vehicle behavior controller 12, for example, and thereby controls the driving force of the vehicle. If the vehicle is equipped with a motor (not shown) as a power source, the vehicle behavior controller 12 outputs a control command to the motor to control the driving force. In this case, the motor corresponds to the drive actuator 28. The drive actuator 28 may be capable of changing the distribution of driving force between the front wheels and the rear wheels. The brake actuator 30 controls a brake system (not shown), for example, in response to a control command from the vehicle behavior controller 12, and thereby controls the braking force of the vehicle.

[0023] The front wheel steering actuator 32 changes the steering angle of the front wheels in response to a control command from the vehicle behavior controller 12. The rear wheel steering actuator 34 changes the steering angle of the rear wheels in response to a control command from the vehicle behavior controller 12.

[0024] The active stabilizer 36 controls the torsional angle of a stabilizer bar (not shown) in response to a control command from the vehicle behavior controller 12. The active suspension 38 controls the suspension characteristics in response to a control command from the vehicle behavior controller 12.

[0025] Next, we will explain the control of vehicle behavior by the vehicle behavior controller 12. Fig. 2 is a functional block diagram of the vehicle behavior controller 12. As shown in Fig. 2, the vehicle behavior controller 12 functions as a two-wheel model calculation unit 50, a center of gravity behavior calculation unit 52, and a six-component force control processing unit 54.

[0026] The two-wheel model calculation unit 50 specifies a target motion of the vehicle based on the driving instructions. As described above, the driving instructions are instructions regarding acceleration / deceleration and steering of the vehicle. From the driving instructions, the two-wheel model calculation unit 50 specifies a target motion of the vehicle, specifically, the vehicle's movement trajectory, vehicle speed, acceleration, etc. Next, the two-wheel model calculation unit 50 applies the target motion to the two-wheel model and calculates the velocity vectors VECf and VECr of the front wheel 40 and the rear wheel 42 required to obtain the target motion.

[0027] The two-wheel model is a model that simulates a vehicle with two wheels, and is a model in which the tire slip angle of the wheels is considered to be zero. Fig. 3 is a diagram showing an example of a two-wheel model 60. In the two-wheel model 60, the motion of the vehicle is represented by a velocity vector VECf of the front wheels 40 and a velocity vector VECr of the rear wheels 42. The velocity vector VECf of the front wheels 40 is defined by the front wheel steering angle Bf and the front wheel speed Vf. The velocity vector VECr of the rear wheels 42 is defined by the rear wheel steering angle Br and the rear wheel speed Vr.

[0028] The curvature Kf of the path traced by the front wheels 40 and the curvature Kr of the path traced by the rear wheels 42 are expressed by the following equations (1) and (2). In equations (1) and (2), Lwb is the wheelbase, which is a known constant. The front wheel speed Vf and the rear wheel speed Vr are calculated from the driving instructions and are equal to each other.

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[0029] The two-wheel model calculation unit 50 obtains the velocity vectors VECf and VECr required to obtain the desired motion by solving the above-mentioned equations (1) and (2). The calculated velocity vectors VECf and VECr are output to the center-of-gravity behavior calculation unit 52.

[0030] The center-of-gravity behavior calculation unit 52 calculates the velocity vector VECg and yaw rate Θ at the center of gravity Pg of the vehicle as center-of-gravity behavior based on the velocity vectors VECf and VECr calculated by the two-wheel model calculation unit 50. The velocity vector VECg is expressed by the vehicle speed Vv and vehicle body slip angle B at the center of gravity Pg.

[0031] 4 is a schematic diagram illustrating the behavior of the center of gravity. The center of gravity behavior calculation unit 52 calculates the behavior of the center of gravity by converting the analysis results of the two-wheel model 60 into a lower-order rigid body model 62. More specifically, the center of gravity behavior calculation unit 52 applies the front wheel steering angle Bf, front wheel speed Vf, rear wheel steering angle Br, and rear wheel speed Vr obtained by the two-wheel model 60 to the following equations (3) to (5). In equations (3) to (5), distance Lf is the distance from the center of gravity Pg to the front wheels 40, and distance Lr is the distance from the center of gravity Pg to the rear wheels 42. The calculated center of gravity behavior, i.e., the velocity vector VECg and yaw rate Θ at the center of gravity Pg, are output to the six-component force control processing unit 54.

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[0032] The six-component force control processing unit 54 controls the steering angle of each of the four wheels, and the braking force and driving force (hereinafter collectively referred to as "braking / driving force") based on the center of gravity behavior. The six-component force control processing unit 54 calculates six-component forces at the center of gravity Pg of the vehicle (hereinafter referred to as "center of gravity six-component forces") based on the vehicle body slip angle B, etc. The six-component force control processing unit 54 also outputs control commands to the vehicle control actuator group 26 so that the calculated center of gravity six-component forces are output. This six-component force control processing unit 54 can be constructed based on the techniques disclosed in, for example, Japanese Patent Application Laid-Open No. 2022-021715 and Japanese Patent Application Laid-Open No. 2022-165535. Therefore, only an overview of the six-component force control processing unit 54 will be briefly explained below. FIG. 5 is a flowchart showing the flow of six-component force control processing.

[0033] The center-of-gravity six-component forces are composed of a longitudinal force Fx, a lateral force Fy, a vertical force Fz, a roll moment Mx, a pitch moment My, and a yaw moment Mz at the center of gravity Pg of the vehicle. The six-component force control processing unit 54 calculates the three planar components by applying known conversion equations to the vehicle body slip angle B, the vehicle speed Vv, and the yaw rate Θ (S10). The three planar components are composed of the longitudinal force Fx, the lateral force Fy, and the yaw moment Mz.

[0034] Next, the six-component force control processor 54 applies the obtained planar three-component forces to an inertial motion model to calculate the sprung three-component forces (S12). The inertial motion model is a vehicle model that takes into account inertial forces and suspension reaction forces. The sprung three-component forces are composed of a vertical force Fz, a roll moment Mx, and a pitch moment My.

[0035] The center of gravity six-component force (Fx, Fy, Fz, Mx, My, Mz) is composed of the sprung three-component force (Fz, Mx, My) and the planar three-component force (Fx, Fy, Mz). The six-component force control processing unit 54 calculates tire three-component forces for each of the four wheels based on the calculated center of gravity six-component force (S14). The tire three-component forces are composed of the tire's longitudinal force Fxi, lateral force Fyi, and vertical force Fzi.

[0036] Next, the six-component force control processing unit 54 calculates the braking / driving forces and steering angles of each of the four wheels based on the calculated tire three-component forces (S16). Specifically, the six-component force control processing unit 54 calculates the braking / driving forces from the tire longitudinal forces Fxi, and calculates the steering angle from the tire lateral forces Fyi. Furthermore, the six-component force control processing unit 54 calculates control commands that will obtain the calculated braking / driving forces and steering angles, and outputs these to the vehicle control actuator group 26 (S18). The vehicle control actuator group 26 then operates in accordance with the control commands, causing the vehicle to operate according to the desired motion.

[0037] As is clear from the above explanation, the vehicle behavior controller 12 disclosed in this specification can appropriately control the braking / driving forces and steering angles of the four wheels, thereby obtaining vehicle behavior that matches the desired motion. Furthermore, the vehicle behavior controller 12 disclosed in this specification first applies the desired motion to the two-wheel model 60, and calculates the velocity vectors VECf, VECr of the front wheels 40 and the rear wheels 42 in the two-wheel model 60. By using the two-wheel model 60 in this way, the amount of calculation by the vehicle behavior controller 12 can be significantly reduced compared to when a four-wheel model is used.

[0038] Furthermore, the vehicle behavior controller 12 disclosed herein converts the analysis results of the two-wheel model 60 into a lower-order rigid body model 62 to calculate the center of gravity behavior. Calculating the center of gravity behavior in this manner enables the use of the six-component force control processing unit 54. That is, as described above, the six-component force control processing unit 54 is constructed based on publicly known technology, i.e., the technology disclosed in Japanese Patent Application Laid-Open Nos. 2022-021715 and 2022-165535. To effectively utilize the publicly known six-component force control processing unit 54, the vehicle behavior controller 12 disclosed herein intentionally converts the analysis results of the two-wheel model 60 into a lower-order rigid body model 62. Then, calculating the center of gravity behavior based on the rigid body model 62 enables the use of the publicly known six-component force control processing unit 54. The use of the publicly known six-component force control processing unit 54 eliminates the need to redesign complex calculation logic, significantly reducing the development cost of the vehicle behavior controller 12. [Explanation of symbols]

[0039] 10 vehicle behavior control device, 12 vehicle behavior controller, 14 processor, 16 memory, 18 accelerator pedal sensor, 20 brake pedal sensor, 22 steering sensor, 24 autonomous driving system, 26 vehicle control actuator group, 28 drive actuator, 30 brake actuator, 32 front wheel steering actuator, 34 rear wheel steering actuator, 36 active stabilizer, 38 active suspension, 40 front wheel, 42 rear wheel, 50 two-wheel model calculation unit, 52 center of gravity behavior calculation unit, 60 two-wheel model, 62 rigid body model, B vehicle slip angle, Bf front wheel steering angle, Br rear wheel steering angle, Kf curvature of front wheel trajectory, Kr curvature of rear wheel trajectory, Pg center of gravity of vehicle, Vf front wheel speed, Vr rear wheel speed, Vv vehicle speed, Θ yaw rate.

Claims

1. an actuator group including one or more actuators configured to drive a vehicle having four wheels; a vehicle behavior controller that controls the operation of the actuator group; The vehicle behavior controller includes: applying a desired motion to a two-wheel model that simulates the vehicle as a two-wheel vehicle, and calculating velocity vectors of the front and rear wheels required to obtain the desired motion; calculating a velocity vector and a yaw rate at a center of gravity of the vehicle based on the velocity vectors of the front wheels and the rear wheels, as center of gravity behavior; calculating a steering angle and a braking / driving force for each of the four wheels based on the center of gravity behavior; controlling the operation of the actuator group so that each of the four wheels outputs the calculated steering angle and braking / driving force; The velocity vector of the front wheels is expressed by the steering angle Bf of the front wheels and the velocity Vf of the front wheels, The velocity vector of the rear wheels is expressed by a steering angle Br of the rear wheels and a velocity Vr of the rear wheels, The center of gravity behavior is expressed by a vehicle body slip angle B at the center of the vehicle, a vehicle speed Vv, and a yaw rate Θ, The vehicle behavior controller calculates the center of gravity behavior by the following equations (3) to (5), where Lwb is the distance between the front wheels and the rear wheels, Lf is the distance between the front wheels and the center of gravity, and Lr is the distance between the rear wheels and the center of gravity: A vehicle behavior control device characterized by: [Equation 1]

2. The vehicle behavior control device according to claim 1, the target motion includes a curvature Kf of a path traced by the front wheels, a curvature Kr of a path traced by the rear wheels, and a vehicle speed Vv; The velocity vector of the front wheels is expressed by the steering angle Bf of the front wheels and the velocity Vf = Vv of the front wheels, The velocity vector of the rear wheels is expressed by the steering angle Br of the rear wheels and the velocity Vr = Vv of the rear wheels, When the distance between the front wheels and the rear wheels is Lwb, the vehicle behavior controller calculates a velocity vector of the front wheels and a velocity vector of the rear wheels by solving the following equations (1) and (2): A vehicle behavior control device characterized by: [Equation 2]

3. The vehicle behavior control device according to claim 1, a vehicle behavior control device, characterized in that the one or more actuators include at least a drive actuator that rotates wheels, a brake actuator that generates braking force, a front wheel steering actuator that steers front wheels, and a rear wheel steering actuator that steers rear wheels.

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