Control method for drifting and obstacle avoidance of electric vehicle, vehicle control unit, and electric vehicle

Abstract

A control method for drifting and obstacle avoidance of an electric vehicle, a vehicle control unit, and an electric vehicle, relating to the field of new energy vehicles, and being applicable to pure electric vehicles and hybrid vehicles. The control method is used for controlling a steering system and a driving system of an electric vehicle during a traveling process in which the vehicle speed of the electric vehicle is greater than a preset vehicle speed, so that the electric vehicle avoids a detected obstacle. The control method comprises: at a first moment when a distance between an electric vehicle and an obstacle is less than a preset distance, controlling a steering wheel of the electric vehicle to rotate; and at a second moment following the first moment, controlling the driving torque of two rear wheels of the electric vehicle to increase. According to the present solution, controlled drift of the electric vehicle is automatically controlled, collision with an obstacle is avoided, the stability of an obstacle avoidance operation is improved, the response is accurate and rapid, and the vehicle safety is effectively improved.

Description

Control methods for drifting and obstacle avoidance in electric vehicles, vehicle controllers, and electric vehicles

[0001] This application claims priority to Chinese Patent Application No. 202411908551.8, filed with the State Intellectual Property Office of China on December 20, 2024, entitled "Control Method for Drifting and Obstacle Avoidance of Electric Vehicle, Vehicle Controller and Electric Vehicle", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electric vehicles, and more specifically, to a control method for drifting and obstacle avoidance in electric vehicles, a vehicle controller, and an electric vehicle. Background Technology

[0003] When an electric vehicle is traveling and there is an obstacle in its path, if the distance between the electric vehicle and the obstacle is too close to allow for emergency braking, braking alone is not the optimal way to avoid a collision or mitigate damage. In such situations, a drift maneuver can be initiated by controlling the steering wheel and accelerator to avoid a collision. However, drifting usually requires skilled driving techniques and precise timing. In extreme scenarios where the distance between the electric vehicle and the obstacle is too close, it is difficult for the driver to drift effectively to avoid the obstacle. Therefore, how to effectively control the vehicle to drift and avoid obstacles is a problem that needs to be solved. Summary of the Invention

[0004] This application provides a control method, vehicle controller, and electric vehicle for drifting and obstacle avoidance of an electric vehicle. When the distance to an obstacle is close, the steering is controlled and the torque output of the rear wheels is adjusted so that the rear wheels exceed the critical adhesion limit. The electric vehicle is automatically controlled to drift in a controlled manner to avoid collision with the obstacle, thereby improving the stability of the obstacle avoidance operation, responding accurately and quickly, and effectively improving vehicle safety.

[0005] Firstly, this application provides a control method for drifting and obstacle avoidance of an electric vehicle. This method controls the steering and drive systems of the electric vehicle while it is traveling at a speed greater than a preset speed, enabling the electric vehicle to avoid detected obstacles. The control method includes: at a first moment after the distance between the electric vehicle and the obstacle becomes less than a preset distance, controlling the steering wheel of the electric vehicle to turn; and at a second moment after the first moment, controlling the drive torque of the two rear wheels of the electric vehicle to increase.

[0006] The electric vehicle can be an electric vehicle or a hybrid vehicle. It can have a distributed drive motor or a centralized drive motor architecture, possessing multiple drive motors and multiple motor controllers. The drive motors can be wheel-side motors or wheel hub motors, and each drive motor can independently drive one wheel of the vehicle.

[0007] Drifting is a special driving technique that involves causing the rear wheels to lose or significantly reduce traction while turning, resulting in oversteer, the rear of the vehicle swinging outwards, and the vehicle sliding through the corner. This process requires a high level of skill from the driver, as well as sensitive control over the vehicle's dynamics through coordinated operation of the steering wheel, accelerator, and brakes. One method of drifting involves reducing or eliminating the lateral adhesion of the tires through driving mechanisms. In obstacle avoidance scenarios, it is difficult for the driver to accurately perform a drift by operating the steering wheel and drive system. The electric vehicle drift obstacle avoidance control method provided in this application can be used for automatic control of the electric vehicle to perform drift obstacle avoidance without driver intervention, or to assist the driver in drift obstacle avoidance, requiring only minimal driver input.

[0008] Electric vehicles can use a perception system to detect their surroundings and operational status. This system includes sensors such as cameras, lidar, and millimeter-wave radar to perceive the environment and collect and process environmental and in-vehicle information, primarily involving technologies like road boundary monitoring, vehicle detection, and pedestrian detection. The system may also include sensors such as speed sensors, acceleration sensors, and inertial measurement units to detect vehicle status and driving information. Perception data signals can include relative distance, relative speed, relative acceleration, and lane information. Perception signals may also include information such as vehicle speed, acceleration, roll angle, and yaw angle. Based on the acquired perception data, electric vehicles can detect information about themselves and obstacles and plan their driving path. They can also use sensors such as cameras and radar to detect the distance between themselves and obstacles in real time and determine whether to perform drift avoidance control based on vehicle speed and distance.

[0009] When an electric vehicle is traveling at a speed exceeding a preset speed, drift obstacle avoidance control is initiated when the distance between the electric vehicle and an obstacle is detected to be less than a preset distance. It should be understood that when the distance between the electric vehicle and the obstacle is less than the preset distance, emergency braking from the preset speed may not avoid a collision or may result in a severe collision. Therefore, a drift obstacle avoidance control method is employed to control the electric vehicle to drift and avoid the obstacle. The preset speed and preset distance can be pre-calibrated based on real-vehicle experiments and / or model calculations, or they can be pre-set considering overall vehicle requirements and performance.

[0010] The electric vehicle's speed is initially greater than the preset speed but less than the speed limit. The vehicle's speed is a crucial factor in obstacle avoidance; by monitoring the vehicle's speed in real time, it's possible to determine whether drift avoidance control should be initiated. It's easy to understand that an electric vehicle's speed for drift avoidance not only has a lower limit but also an upper limit. When the electric vehicle's speed is greater than or equal to the speed limit, neither emergency braking nor drift avoidance methods may prevent a collision with the obstacle.

[0011] At the first moment, the electric vehicle begins to steer, and the steering wheel of the electric vehicle is turned to generate a sideslip angle and lateral force.

[0012] At the second moment, the driving torque of the two rear wheels of the electric vehicle increases, breaking through the road surface adhesion, and the rear wheels begin to slip. The lateral force on the electric vehicle is greater than the lateral friction limit of the tires, so the electric vehicle sideslips, the wheels travel along the tangent of the vehicle body, and the electric vehicle drifts.

[0013] It should be understood that the second moment can be very close to the first moment. An electric vehicle can adjust the increase of the drive torque of the rear wheels after the steering wheel has been turned, or it can start adjusting the increase of the drive torque of the rear wheels during the steering wheel turning process.

[0014] In this application, the driving torque of a wheel can be understood as the torque output by the drive motor used to drive the wheel.

[0015] The coefficient of friction (COP) is the magnitude of the friction between a vehicle's wheels and the road surface, significantly impacting vehicle safety and stability. COP is influenced by various factors, including road material, humidity, temperature, tire type, and wear. Different road conditions and weather conditions may result in different COPs. When the adhesion between the wheels and the road surface changes, the speed and torque of the drive motor also change. Therefore, changes in road adhesion can be detected by measuring the drive motor speed using a resolver sensor. The actual torque output by the drive motor reflects the road surface's adhesion capability to some extent, allowing for real-time, accurate, and rapid observation of road adhesion based on resolver and torque signals.

[0016] According to the solution in this application, the road surface adhesion capability is observed in real time, and the rear wheel drive torque is adjusted to make the rear wheel break through the critical adhesion limit. The rear wheel is actively controlled to slip, creating favorable conditions for the vehicle to drift. This makes the drift obstacle avoidance process reliably controllable and improves the vehicle's safety.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: at a third moment after the second moment, when the distance between the electric vehicle and the obstacle is greater than a second preset distance, controlling the driving torque of the two rear wheels to decrease.

[0018] At the third moment, the electric vehicle changes its path by drifting, avoiding the obstacle and gradually moving away from it. The distance between the electric vehicle and the obstacle increases to a level greater than the second preset distance. At this point, the obstacle avoidance objective is achieved, and the drift can be stopped. The drive torque of the two rear wheels is reduced to keep it within the road surface adhesion limit, preventing slippage. The second preset distance can be pre-calibrated based on real-vehicle experiments and / or model calculations, or it can be preset by comprehensively considering the vehicle's requirements and performance.

[0019] It should be understood that the distance between the electric vehicle and the obstacle includes the distance between the front of the electric vehicle and the obstacle, as well as the distance between the body of the electric vehicle and the obstacle. The electric vehicle can also determine whether obstacle avoidance has been completed based on its actual driving path; obstacle avoidance is considered complete when the obstacle is no longer located on the electric vehicle's actual driving path.

[0020] According to the solution in this application, after an electric vehicle avoids an obstacle by drifting, the torque of the rear wheel drive is reduced to stop the rear wheel from slipping and obtain sufficient grip. The electric vehicle then exits the drift state, preventing the electric vehicle from continuing to drift and causing other collisions, thus improving the safety and controllability of the electric vehicle.

[0021] In conjunction with the first aspect, in some implementations of the first aspect, at a fourth time after the third time, the driving torque of the two rear wheels is reduced to zero, and the braking system of the electric vehicle is controlled to increase the output braking force.

[0022] In the fourth moment, after the electric vehicle completes the drift and obstacle avoidance maneuver, the system can be controlled to stop the electric vehicle by reducing the drive torque to zero and controlling the braking system to output braking force, thus bringing the electric vehicle to a stop. Furthermore, the system can also control the steering wheel of the electric vehicle to return to center.

[0023] It should be understood that after the third moment, the electric vehicle can still be controlled to continue driving, that is, the drive torque of the two rear wheels can be controlled to be equal to the torque indicated by the accelerator pedal opening.

[0024] According to the solution in this application, after the electric vehicle completes the drifting obstacle avoidance, the electric vehicle is controlled to stop, avoiding the danger caused by continuing to drive, thus improving the safety and controllability of the electric vehicle.

[0025] In conjunction with the first aspect, in some implementations of the first aspect, the control method specifically includes: between the second and third time points, controlling the driving torque of the two rear wheels to be greater than the driving torque of the two front wheels.

[0026] During a drift, the front wheels should maintain traction. As the steering wheels, if they lose traction first, it will result in a partial or near-complete loss of grip, reducing or eliminating steering effectiveness. With the same steering wheel angle, the actual turning angle produced by the vehicle will be smaller than when there is traction, leading to understeer. For the rear wheels, they are in a critical stability range, within the non-linear range of the tire's friction limit circle, and are prone to sideslip. The goal of controlling the rear wheels is to cause them to lose or partially lose traction, causing the electric vehicle to fishtail. Therefore, controlling the drive torque of the rear wheels to be greater than that of the front wheels can provide favorable conditions for drifting and keep the electric vehicle's drift process under control.

[0027] According to the solution in this application, during the drifting process, controlling the driving torque of the rear wheel to be greater than that of the front wheel provides the critical condition for drifting, making the drift obstacle avoidance controllable and improving the safety and stability of the vehicle.

[0028] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: before the first moment, when the distance between the electric vehicle and the obstacle is greater than a preset distance and less than a third preset distance, controlling the drive motor of the electric vehicle to output reverse torque and controlling the drive motor to stop outputting reverse torque at the first moment, wherein the direction of the reverse torque is opposite to the rotational speed direction of the drive motor.

[0029] Reverse torque can also be understood as negative driving torque. A drive motor consists of stator windings and a rotor. By outputting alternating current to the three-phase stator windings, the output torque of the drive motor can be controlled. By adjusting the magnitude of the stator winding current and the phase of the three-phase current through the motor controller, the strength and direction of the stator magnetic field can be changed, thereby altering the interaction force between the stator and rotor, i.e., the drive motor torque. Changing the phase of the three-phase current output to the drive motor causes the rotor to cut the magnetic field generated by the stator windings, converting the rotor's kinetic energy into electrical energy that is input into the power battery; in this case, the drive motor outputs negative torque. The motor controller can increase or decrease the output driving torque or reverse torque by changing the magnitude of the three-phase current output to the drive motor.

[0030] When the driving torque of a wheel is negative, the drive motor driving that wheel outputs a reverse torque. The direction of the reverse torque is opposite to the rotational speed of the drive motor, and the reverse torque is used to brake that wheel.

[0031] The third preset distance can be the distance at which the electric vehicle begins to brake. The third preset distance can be pre-calibrated based on actual vehicle experiments and / or model calculations, or it can be pre-set by comprehensively considering the needs and performance of the entire vehicle.

[0032] Before the first moment, when the distance between the electric vehicle and the obstacle is greater than a preset distance but less than a third preset distance, and the steering wheel has not yet been turned while the electric vehicle is still moving straight, the electric vehicle can begin to brake. At this time, braking can be achieved by controlling the drive motor to output reverse torque, shifting the electric vehicle's center of gravity, reducing the axle load on the rear axle, and facilitating the rear wheels to break through road adhesion, thus providing favorable conditions for the electric vehicle to drift. At the first moment, the drive motor is controlled to stop outputting reverse torque to prevent the reverse torque from affecting the vehicle's balance during the drift process.

[0033] According to the scheme of this application, braking is performed before drifting to transfer the rear axle load, providing favorable conditions for the electric vehicle to drift. The reverse torque output by the drive motor is used for braking, which has a rapid response and improves the handling and stability of the electric vehicle.

[0034] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: before the first moment, when the distance between the electric vehicle and the obstacle is greater than a preset distance and less than a third preset distance, controlling the braking system of the electric vehicle to output braking force to the four wheels of the electric vehicle and controlling the braking force output by the braking system to decrease to zero at the first moment.

[0035] Before the initial drift begins (the first moment), when the steering wheel has not yet turned and the electric vehicle is still moving straight, braking force can be applied to the wheels via the braking system to shift the vehicle's center of gravity. This reduces the axle load on the rear axle, making it easier for the rear wheels to break free of road adhesion and thus providing favorable conditions for drifting. At the first moment, the braking system stops applying braking force to prevent it from affecting the vehicle's balance during the drift.

[0036] The braking force output by the control braking system and the reverse torque output by the control drive motor can also be used in conjunction. Within the capability of the drive system, the reverse torque output by the drive motor is used first for braking. When the capability of the drive system is insufficient, the braking force of the braking system is used as a supplement, resulting in a precise and rapid response.

[0037] According to the scheme of this application, the drive and braking are controlled in a coordinated manner, with a precise and rapid response. Braking is performed before drifting to transfer the rear axle load, providing favorable conditions for electric vehicle drifting and improving the handling and stability of electric vehicle.

[0038] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: controlling the slip ratio of the two rear wheels to be greater than a preset value between the second and third time points.

[0039] The rotational speed of the drive motor can be obtained through the resolver signal from the resolver sensor. The angular velocity of the wheels can be calculated using the drive motor speed and the transmission ratio of the electric vehicle. Combined with the wheel radius and the speed of the electric vehicle, the slip ratio of each wheel can be obtained. In this application, the slip ratio can be either the slip rate or the slip ratio. The electric vehicle can adjust the drive torque of the rear wheels based on the slip ratio of the rear wheels. For the rear wheels, during drifting, it is desirable for the slip ratio of the rear axle wheels to be within the critical stability range, within the nonlinear range of the tire's friction limit circle, tending towards sideslip. By controlling the slip ratio of the two rear wheels to be greater than a preset value, the electric vehicle can be in a drifting state.

[0040] According to the solution of this application, the rear wheel drive torque is varied according to the wheel slip ratio, so that the rear wheel slip ratio is greater than a preset value, thereby precisely controlling the electric vehicle to be in a drift state, with rapid response and improved handling and stability of the electric vehicle.

[0041] In conjunction with the first aspect, in some implementations of the first aspect, the control method specifically includes: at a first moment, controlling the steering wheel rotation angle of the electric vehicle to increase as the speed of the electric vehicle increases, and controlling the steering wheel rotation angle of the electric vehicle to decrease as the distance between the electric vehicle and the obstacle increases.

[0042] The faster an electric vehicle travels or the closer it is to an obstacle, the shorter the time it takes to hit the obstacle. Therefore, a larger drift angle is needed to avoid the obstacle. Consequently, the steering wheel angle increases with vehicle speed and decreases with distance from the obstacle. Conversely, the slower an electric vehicle travels or the farther it is from the obstacle, the longer the time it takes to hit the obstacle. This allows for a greater margin of error in drifting to avoid the obstacle. Therefore, the steering wheel angle decreases with decreasing vehicle speed and decreases with increasing distance from the obstacle.

[0043] According to the solution in this application, the steering wheel rotation angle of the electric vehicle when drifting and avoiding obstacles is determined based on the vehicle speed and the distance to the obstacle, which improves the effect of drifting and avoiding obstacles and enhances the handling and safety of the electric vehicle.

[0044] In conjunction with the first aspect, in some implementations of the first aspect, the control method specifically includes: at a second moment, controlling the drive torque of the two rear wheels of the electric vehicle to increase to a target value, the target value increasing with the increase of the speed of the electric vehicle, and the target value decreasing with the increase of the distance between the electric vehicle and the obstacle.

[0045] This target value is greater than the road surface adhesion capacity, which can be detected based on the resolver signal and the output torque of the drive motor. This prevents the target value from far exceeding the road surface adhesion capacity, which could lead to excessive slippage and cause danger.

[0046] The faster an electric vehicle travels or the closer it is to an obstacle, the shorter the time it takes to hit the obstacle. This requires the rear wheels to slip more quickly. Therefore, the drive torque controlling the rear wheels increases with increasing speed and decreases with decreasing distance from the obstacle. Conversely, the slower an electric vehicle travels or the farther it is from the obstacle, the longer the time it takes to hit the obstacle. This allows for more margin of error in rear wheel slippage. Therefore, the drive torque controlling the rear wheels decreases with decreasing speed and decreases with increasing distance from the obstacle.

[0047] According to the solution in this application, the increase in rear-wheel drive torque when an electric vehicle performs drift obstacle avoidance is determined based on vehicle speed and distance from obstacles, thereby improving the drift obstacle avoidance effect and enhancing the handling and safety of the electric vehicle.

[0048] In conjunction with the first aspect, in some implementations of the first aspect, the control method specifically includes: between the second and third time points, controlling the driving torque of the rear wheels of the electric vehicle to vary with the change in the sideslip angle of the electric vehicle's center of gravity.

[0049] Electric vehicles can detect information about themselves and obstacles based on acquired perception data and plan a drift-to-avoidance path. Based on this path and the actual path taken by the electric vehicle, the target sideslip angle during the drift-to-avoidance process can be determined. The electric vehicle then controls the magnitude of the rear-wheel drive torque according to its actual sideslip angle: when the sideslip angle is less than the target sideslip angle, the rear-wheel drive torque is increased; when the sideslip angle is greater than the target sideslip angle, the rear-wheel drive torque is decreased.

[0050] According to the scheme of this application, using the sideslip angle as the control parameter in the drifting obstacle avoidance process of electric vehicles can accurately control the drifting obstacle avoidance path of electric vehicles, effectively control the sideslip angle, improve handling stability, avoid uncontrollable dangers of electric vehicles during drifting obstacle avoidance, and improve the controllability and safety of electric vehicles.

[0051] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: between the second and third time points, controlling the drive torque of the rear wheels of the electric vehicle to be different from the torque indicated by the opening of the accelerator pedal.

[0052] The accelerator pedal in this application can also be called the power pedal or throttle pedal. The opening degree of the accelerator pedal indicates the amount of driving force required by the driver. The larger the opening degree of the accelerator pedal, the greater the driver's demand for driving force, and the greater the torque required from the drive motor. When drift and obstacle avoidance control is not performed, the torque output of the drive motor can be controlled according to the opening degree of the accelerator pedal. The larger the opening degree of the accelerator pedal, the greater the torque output of the drive motor; the smaller the opening degree of the accelerator pedal, the smaller the torque output of the drive motor. The drive torque of the rear wheels varies with the opening degree of the accelerator pedal.

[0053] Between the second and third moments, the electric vehicle is drifting and avoiding obstacles. The driving torque of the rear wheels differs from the torque indicated by the accelerator pedal opening. The driving torque of the rear wheels does not change with the brake pedal opening. At this time, the torque is determined directly by a closed-loop torque calculation within the motor controller, which differs from the torque indicated by the accelerator pedal opening.

[0054] According to the solution in this application, the driving torque of the rear wheel in the closed loop of the drive system during drift obstacle avoidance is determined by the opening of the accelerator pedal, which reduces the signal transmission delay, improves the control accuracy and speed, and enhances the safety and efficiency of drift obstacle avoidance.

[0055] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: after the first moment, in response to changes in the opening degree of the accelerator pedal, the opening degree of the brake pedal, or the steering wheel angle operated by the user, stopping the control of the steering wheel rotation of the electric vehicle and controlling the drive torque of the two rear wheels to be equal to the torque indicated by the opening degree of the accelerator pedal.

[0056] It should be understood that drifting obstacle avoidance is mainly the control performed in the intelligent driving or autonomous driving scenarios of electric vehicles. When the user intervenes in the process, the human driving signal should take priority. When the driver is detected to have made an active operation, such as turning the steering wheel, pressing the accelerator pedal or pressing the brake pedal, the electric vehicle will determine that the driver has intervened, stop the automatic drifting obstacle avoidance, and respond to the driver's operation to take control.

[0057] According to the solution in this application, the driver's operation takes priority during drift obstacle avoidance. When the driver intervenes, the drift obstacle avoidance stops, which improves the flexibility of handling in emergency situations and enhances the safety and reliability of electric vehicles.

[0058] In conjunction with the first aspect, in some implementations of the first aspect, the control method further includes: before the first moment, the user controls the electric vehicle to activate the automatic obstacle avoidance mode by touching the central control screen of the electric vehicle or activating the automatic obstacle avoidance button. The automatic obstacle avoidance mode is used to control the steering system and drive system of the electric vehicle to avoid obstacles while the electric vehicle is traveling at a speed greater than a preset speed.

[0059] Drift obstacle avoidance can be used as an optional operating mode for electric vehicles. Drift obstacle avoidance control will only be activated when a collision is imminent if the user has previously activated the automatic obstacle avoidance mode.

[0060] Electric vehicles can be equipped with an automatic obstacle avoidance button for driver operation. For example, the automatic obstacle avoidance button can be a physical button; pressing this button activates the electric vehicle's automatic obstacle avoidance mode, thereby initiating drift obstacle avoidance control when the distance between the electric vehicle and an obstacle is less than a preset distance while the vehicle is traveling at a speed exceeding a preset speed. Alternatively, the automatic obstacle avoidance button can be a virtual button on the central control screen, which the driver can select to activate the automatic obstacle avoidance mode. Furthermore, the automatic obstacle avoidance button can also be indirectly configured, for example, by incorporating it into the intelligent driving mode button or by default activating the electric vehicle's automatic obstacle avoidance mode when the driver disables other buttons.

[0061] According to the scheme of this application, an automatic obstacle avoidance switch is set for the driver to adjust, which can improve the driver's driving experience and enhance the safety of electric vehicles.

[0062] Secondly, this application provides a vehicle controller for executing the control methods described in the first aspect and its various implementations.

[0063] The vehicle controller in this application can be a motor controller for an electric vehicle, a vehicle controller, an intelligent driving controller, or a separately configured controller with control capabilities. This vehicle controller is applicable to electric or hybrid vehicles, where the electric vehicle can have a distributed motor or centralized motor architecture, possessing multiple drive motors and multiple motor controllers. The vehicle controller can be any one of these multiple motor controllers.

[0064] The intelligent driving controller in this application can be a domain controller used to realize functions such as perception, localization, path planning, and decision control. When the electric vehicle is in intelligent driving mode, the intelligent driving controller performs intelligent active driving or assists the user in driving. The intelligent driving controller receives perception data signals sent by the electric vehicle's perception components, such as radar and cameras. The intelligent driving controller fuses the information perceived by various sensors and obtains the electric vehicle's driving status and lane information based on the perception data signals. By analyzing signals such as distance, speed, and acceleration, it obtains target acceleration and target speed, etc. Based on the fused information, it makes driving decisions / planning, issues operation commands to the vehicle controller, and the vehicle controller sends an intelligent driving torque signal to the motor controller, thereby outputting the torque value indicated by the intelligent driving torque signal to complete intelligent driving.

[0065] Thirdly, this application provides an electric vehicle including a vehicle controller, a steering system, and a drive system as described in the second aspect. The drive system includes a motor controller and a drive motor, the motor controller controlling the drive motor to output drive torque to the two rear wheels of the electric vehicle. The steering system controls the steering angle of the two front wheels of the electric vehicle.

[0066] Other beneficial effects can be found in the description of the first aspect, and will not be repeated here. Attached Figure Description

[0067] Figure 1 is a schematic diagram of a T-shaped collision of an electric vehicle provided in an embodiment of this application;

[0068] Figure 2 is a schematic diagram of an electric vehicle provided in an embodiment of this application;

[0069] Figure 3 is a schematic diagram of the architecture of an electric vehicle provided in an embodiment of this application;

[0070] Figure 4 is a schematic diagram of the electric vehicle drift obstacle avoidance control process provided in an embodiment of this application;

[0071] Figure 5 is a schematic diagram of electric vehicle drifting and obstacle avoidance provided in an embodiment of this application;

[0072] Figure 6 is a schematic diagram of the vehicle controller architecture provided in an embodiment of this application;

[0073] Figure 7 is a schematic diagram of the vehicle controller drift obstacle avoidance control provided in the embodiment of this application. Detailed Implementation

[0074] The technical solutions in this application will now be described in conjunction with the accompanying drawings. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments.

[0075] Drifting is a sport that focuses on specific driving techniques. Vehicle drifting involves using oversteer to steer the vehicle sideways through a corner. Drifting occurs through the interaction between the tires and the road surface, generating lateral and longitudinal forces on the tires. When the rear-wheel drive lateral force exceeds the road surface traction, the tires generate lateral velocity, causing sideslip, and the wheels travel along the tangent of the vehicle's circumference, resulting in a drift. Drivers can drift by manipulating the drivetrain, brakes, and steering wheel to achieve small-radius turns, satisfying the needs of racing, driving pleasure, and maneuvering in tight areas. However, drifting by a driver requires highly skilled driving techniques, which is difficult for ordinary drivers to achieve. The principle behind drifting is to cause the rear wheels to lose most or all of their traction, while the front wheels maintain traction. At this point, as long as the front wheels have a certain lateral force, the vehicle will fishtail, resulting in a drift.

[0076] As shown in Figure 1, when driving at intersections, especially those without traffic lights, a T-shaped collision scenario may occur from two directions, where one vehicle hits the side of another. If the two vehicles are too close to brake in time, a collision may occur. Because the side structure of a car lacks energy absorption devices, T-shaped collisions result in greater injuries and losses in traffic accidents compared to other types of collisions.

[0077] In one possible implementation, a collision could be avoided by swerving to one side and braking suddenly.

[0078] Understandably, if the two vehicles are close together, the steering angle may not be sufficient, and the deceleration from emergency braking may not be adequate to avoid a collision.

[0079] To address the aforementioned issues, this application provides a control method, vehicle controller, and electric vehicle for drifting and obstacle avoidance of an electric vehicle. When the distance to an obstacle is close, the electric vehicle is controlled to steer and the torque output of the rear wheels is adjusted so that the rear wheels exceed the critical adhesion limit. The electric vehicle is automatically controlled to drift in a controlled manner, avoiding collisions with obstacles. This improves the stability of obstacle avoidance operations, provides precise and rapid response, and effectively enhances vehicle safety.

[0080] Figures 2 and 3 are schematic diagrams of the architecture of the electric vehicle 10 provided in the embodiments of this application.

[0081] As shown in Figure 2, the electric vehicle 10 includes a vehicle controller 20, a drive system, a braking system 60, an intelligent driving controller 70, a power battery (not shown in the figure), and multiple wheels. The drive system includes a drive motor 30 and a motor controller 40. The motor controller 40 outputs current to the drive motor 30 to control the drive motor 30 to output torque to drive the electric vehicle 10. The intelligent driving controller 70 plans a driving path based on obstacle information detected by the sensors of the electric vehicle 10 and the driving information of the electric vehicle 10.

[0082] The vehicle controller in this application may be the motor controller 40 of the electric vehicle 10, or the vehicle controller 20, or the intelligent driving controller 70, or a separately configured controller with control capabilities.

[0083] Understandably, the electric vehicle 10 in this application embodiment can be any type of vehicle such as a car, truck, or passenger bus, or it can be a tricycle, two-wheeled vehicle, or other transportation device for carrying passengers or goods, or other types of vehicles powered by a power battery. This application embodiment does not limit this. The vehicle includes, but is not limited to, pure electric vehicles (pure EV / battery EV), hybrid electric vehicles (HEV), range-extended electric vehicles (REEV), and plug-in hybrid electric vehicles (PHEV).

[0084] The power battery in this application embodiment can be a lithium-ion battery, lithium metal battery, lead-acid battery, nickel-cadmium battery, nickel-metal hydride battery, lithium-sulfur battery, lithium-air battery, or sodium-ion battery, etc., and this application does not limit it to any particular type. The power battery can also supply power to other electrical components in the vehicle, such as the vehicle's air conditioning system and in-vehicle media player.

[0085] The electric vehicle 10 can be a rear-wheel drive vehicle, with the two rear wheels driven by a drive motor 30. Alternatively, the electric vehicle 10 can have a distributed four-motor drive architecture, with the drive motors positioned beside the driving wheels and controlled by individual motor controllers 40. The electric vehicle 10 can also have a centralized drive motor architecture, with the drive motors for driving the two front wheels or the two rear wheels grouped together. There can be one or more motor controllers 40. The motor controller 40 can correspond one-to-one with the drive motors 30, or one motor controller 40 can correspond to multiple drive motors 30. The motor controller 40 is used to control the output torque of one or more drive motors 30 to drive the electric vehicle 10.

[0086] In one embodiment, as shown in FIG3(a), the electric vehicle 10 may be a distributed four-drive motor drive architecture, with drive motors mounted on the sides of the driving wheels and controlled by separate motor controllers. Alternatively, the electric vehicle 10 may be a centralized four-drive motor drive architecture, as shown in FIG3(b), where two drive motors for driving the two front wheels or the two rear wheels are mounted together.

[0087] For example, the electric vehicle 10 includes four motor controllers: motor controller 41, motor controller 42, motor controller 43, and motor controller 44. The four motors include drive motor 31, drive motor 32, drive motor 33, and drive motor 34. Motor controller 41 controls drive motor 31 to drive wheel 51, motor controller 42 controls drive motor 32 to drive wheel 52, motor controller 43 controls drive motor 33 to drive wheel 53, and motor controller 44 controls drive motor 34 to drive wheel 54.

[0088] In one embodiment, the electric vehicle 10 may also be a centralized drive motor architecture as shown in Figure 3(c), with one drive motor driving the two front wheels of the electric vehicle 10 and two drive motors driving the two rear wheels of the electric vehicle 10 respectively.

[0089] In one embodiment, the various architectures mentioned above can also be combined, for example, the front drive adopts a distributed drive motor architecture and the rear drive adopts a centralized drive motor architecture.

[0090] The vehicle controller provided in this application can be any one of multiple motor controllers.

[0091] The electric vehicle 10 also includes an accelerator pedal, a brake pedal, a steering system, and a steering wheel. The accelerator pedal is used to indicate the torque output to the wheels of the electric vehicle 10. The brake pedal is used to indicate the braking force output to the wheels of the electric vehicle 10, the steering wheel angle is used to indicate the steering angle of the two front wheels, and the steering system is used to control the steering angle of the two front wheels of the electric vehicle 10.

[0092] In one embodiment, the braking system 60 includes a brake controller and a plurality of wheel-end braking devices, the brake controller being signal-connected to the brake pedal. The brake controller can be used to determine the braking force based on the opening degree of the brake pedal. During driving, when the electric vehicle 10 needs to brake, the driver depresses the brake pedal. The brake controller receives the brake pedal signal from the brake pedal and outputs a braking force distribution signal to the wheel-end braking devices. The wheel-end braking devices receive the braking force distribution signal and output clamping force to the brake disc according to the indication of the braking force distribution signal, thereby generating frictional braking force, causing the electric vehicle 10 to brake.

[0093] In one embodiment, the motor controller 40 includes a signal interface, through which the motor controller 40 is connected to the vehicle controller 20 and other motor controllers 40. The vehicle controller 20 is signal-connected to the accelerator pedal, and calculates the vehicle torque demand based on the accelerator pedal opening during the operation of the electric vehicle 10, and sends a torque signal to the motor controllers 40 according to the vehicle torque demand. Each motor controller 40 controls the corresponding drive motor to output torque to drive the corresponding wheel according to the torque signal indication.

[0094] In one embodiment, each motor controller 40 may also be directly connected to the accelerator pedal and control the corresponding motor output torque according to the torque signal output by the accelerator pedal.

[0095] In one embodiment, the vehicle controller 20 is connected to the brake pedal via a signal interface. The vehicle controller 20 calculates the vehicle braking demand based on the brake pedal opening of the electric vehicle 10 during driving and sends a braking signal to the brake controller based on the vehicle braking demand. The brake controller controls the corresponding wheel-end braking device to output braking force to brake the corresponding wheel according to the indication of the braking signal.

[0096] In one embodiment, the vehicle controller 20 can also be directly connected to the brake pedal and control the wheel-end braking device to output braking force according to the opening degree of the brake pedal.

[0097] In one embodiment, each motor controller 40 uses a resolver sensor via a signal interface. The resolver sensor detects the rotational speed of the drive motor 30 controlled by the motor controller 40, and the motor controller 40 receives signals from the resolver sensor. The motor controller 40 can also generate a rotational speed signal based on the signals from the resolver sensor and send the rotational speed signal to the other three motor controllers 40. Similarly, each motor controller 40 also receives rotational speed signals from the other three motor controllers 40.

[0098] The resolver sensor can accurately detect the position, direction and speed of the motor rotor, and is responsible for monitoring and extracting the rotational speed of the drive motor. It has a high sampling rate and is directly connected to the motor controller 40, resulting in short signal transmission time and higher stability.

[0099] In one embodiment, the motor controller 40 also acquires vehicle signals from the vehicle controller 20 or other sensors of the electric vehicle 10 via a signal interface. The vehicle signals are used to indicate the vehicle speed, yaw rate, and center of gravity sideslip angle of the electric vehicle 10.

[0100] In one embodiment, the motor controller 40 can connect to the vehicle controller 20, the intelligent driving controller 70, and the steering system via a controller area network (CAN) bus, a local interconnect network (LIN) bus, a high-speed fault-tolerant network protocol (FlexRay), or other types of connection methods, and exchange signals.

[0101] In one embodiment, the electric vehicle 10 includes an automatic obstacle avoidance button. The automatic obstacle avoidance button is used to activate an automatic obstacle avoidance mode, which controls the steering and drive systems of the electric vehicle 10 to avoid obstacles while the electric vehicle 10 is traveling at a speed greater than a preset speed.

[0102] An automatic obstacle avoidance button can be provided on the electric vehicle 10 for the driver to operate. For example, the automatic obstacle avoidance button can be a physical button; pressing this physical button activates the automatic obstacle avoidance mode of the electric vehicle 10, thereby initiating drift obstacle avoidance control when the distance between the electric vehicle 10 and an obstacle is less than a preset distance while the electric vehicle 10 is traveling at a speed greater than a preset speed. Alternatively, the automatic obstacle avoidance button can be a virtual button on the central control screen, which the driver can select to activate the automatic obstacle avoidance mode of the electric vehicle 10. Furthermore, the automatic obstacle avoidance button can also be indirectly configured, for example, by incorporating it into the intelligent driving mode button or by default activating the automatic obstacle avoidance mode of the electric vehicle 10 when the driver closes other buttons.

[0103] It should be understood that the vehicle controller provided in this application may be a vehicle controller 20, a motor controller 40, an intelligent driving controller 70, or other separately configured controllers with control capabilities.

[0104] The drift obstacle avoidance control method provided in this application embodiment is used to control the electric vehicle 10 to drift to one side when it encounters an obstacle. The drift causes the electric vehicle to oversteer and avoid the obstacle, preventing collision damage. The vehicle controller senses the road surface adhesion, causing the rear wheels to exceed the road surface adhesion limit. This controlled drift does not require driver intervention, has a short signal transmission time, and improves vehicle safety. The following description, in conjunction with Figures 4 and 5, illustrates the drift obstacle avoidance control method and vehicle controller provided in this application embodiment at the first time point t1, the second time point t2, the third time point t3, and the fourth time point t4 during the electric vehicle 10's travel at a speed greater than a preset speed. Figure 4 is a signal timing diagram of the electric vehicle 10 during its travel, showing the relationship between the distance between the electric vehicle and the obstacle, the steering wheel angle, the rear wheel drive torque, the braking force, and the difference in front and rear wheel drive torques.

[0105] In one embodiment, before the first moment t1, the user controls the electric vehicle 10 to activate the automatic obstacle avoidance mode by touching the central control screen of the electric vehicle 10 or activating the automatic obstacle avoidance button. The automatic obstacle avoidance mode is used to control the steering system and drive system of the electric vehicle 10 so that the electric vehicle 10 avoids obstacles while driving at a speed greater than a preset speed.

[0106] Drift obstacle avoidance can be used as an optional operating mode for electric vehicle 10. Drift obstacle avoidance control will only be performed when a collision is about to occur if the user has previously activated the automatic obstacle avoidance mode.

[0107] In one embodiment, after the automatic obstacle avoidance mode of the control method is activated, the control method provided in this application includes detecting the distance between the electric vehicle 10 and the obstacle during the driving of the electric vehicle 10.

[0108] The electric vehicle 10 can detect its surrounding environment and operational status information through a perception system. The perception system may include sensors such as cameras, lidar, and millimeter-wave radar to perceive the surrounding environment and collect and process environmental and in-vehicle information, primarily involving technologies such as road boundary monitoring, vehicle detection, and pedestrian detection. The perception system may also include sensors such as vehicle speed sensors, acceleration sensors, and inertial measurement units to detect vehicle status and driving information. Perception data may include relative distance, relative speed, relative acceleration, and lane information. Perception data may also include electric vehicle speed, acceleration, roll angle, and yaw angle. Based on the acquired perception data, the electric vehicle 10 can detect information about obstacles and plan its driving path. The perception system sends the detected distance to obstacles to the vehicle controller, which then determines whether to perform drift obstacle avoidance control based on the vehicle speed and the distance to obstacles.

[0109] While the electric vehicle 10 is traveling at a speed greater than a preset speed, when the distance between the electric vehicle 10 and an obstacle is detected to be less than a preset distance, drift obstacle avoidance control is initiated. It should be understood that when the distance between the electric vehicle 10 and the obstacle is less than the preset distance, emergency braking from the preset speed may not avoid a collision or may result in a severe collision. Therefore, the electric vehicle 10 employs a drift obstacle avoidance control method to drift and avoid the obstacle. The preset speed and preset distance can be pre-calibrated based on real-vehicle experiments and / or model calculations, or they can be pre-set considering overall vehicle requirements and performance.

[0110] It is easy to understand that the electric vehicle 10 has not only a lower limit but also an upper limit for the speed at which it can drift to avoid obstacles. When the speed of the electric vehicle 10 is greater than or equal to the speed limit, it may be impossible to avoid a collision with the obstacle, regardless of whether the electric vehicle 10 uses emergency braking or drifting to avoid obstacles.

[0111] As shown in Figures 4 and 5, in one embodiment, during the operation of the electric vehicle 10 at a speed greater than a preset speed, at a first moment t1 after the distance between the electric vehicle 10 and the obstacle becomes less than a preset distance, the steering wheel of the electric vehicle is controlled to turn. At a second moment t2 after the first moment t1, the drive torque of the two rear wheels of the electric vehicle 10 is increased.

[0112] At the first moment t1, the electric vehicle begins to steer, controlling the steering wheel to rotate, causing the electric vehicle to generate a sideslip angle and lateral force. At the second moment t2, the driving torque of the two rear wheels of the electric vehicle increases, exceeding the road surface adhesion, and the rear wheels begin to slip. The lateral force on the electric vehicle exceeds the lateral friction limit of the tires, resulting in sideslip. The wheels travel along the tangent of the vehicle's circumference, and the electric vehicle drifts. It should be understood that the second moment t2 can be very close to the first moment t1. The electric vehicle 10 can adjust the increase of the driving torque of the rear wheels after the steering wheel rotation is completed, or it can start adjusting the increase of the driving torque of the rear wheels during the steering wheel rotation. In this application, the driving torque of the wheel can be understood as the torque output by the drive motor used to drive the wheel. The road surface adhesion coefficient is the magnitude of the friction between the wheel and the road, and its magnitude has an important impact on the safety and stability of vehicle driving. The road surface adhesion coefficient is affected by various factors, including road surface material, humidity, temperature, tire type, and wear degree. The corresponding road surface adhesion coefficient may vary under different road conditions and weather conditions. When the adhesion between the wheels and the road surface changes, the speed and torque of the drive motor driving the wheels also change. Therefore, changes in road surface adhesion can be sensed and observed by detecting changes in the drive motor speed using a resolver sensor. The actual torque output by the drive motor reflects the road surface adhesion to a certain extent. Thus, the road surface adhesion can be observed accurately and quickly in real time based on the resolver signal and torque signal. According to the solution of this application, the road surface adhesion is observed in real time, and the rear wheel drive torque is adjusted to make the rear wheels exceed the critical adhesion limit, actively controlling the rear wheels to slip, creating favorable conditions for vehicle drifting, making the drifting obstacle avoidance process reliably controlled, and improving vehicle safety.

[0113] In one embodiment, before the first moment t1, at moment t0 when the distance between the electric vehicle 10 and the obstacle is greater than a preset distance and less than a third preset distance, the drive motor 30 of the electric vehicle 10 is controlled to output reverse torque, and at the first moment t1, the drive motor is controlled to stop outputting reverse torque. The direction of the reverse torque is opposite to the rotational speed direction of the drive motor.

[0114] In one embodiment, before the first time t1, at time t0 when the distance between the electric vehicle 10 and the obstacle is greater than a preset distance and less than a third preset distance, the braking system 60 of the electric vehicle 10 is controlled to output braking force to the four wheels of the electric vehicle 10, and the braking force output by the braking system 60 is reduced to zero at the first time t1.

[0115] When the distance between the electric vehicle and the obstacle is greater than a preset distance but less than a third preset distance, and the steering wheel has not yet been turned, the electric vehicle 10 is still moving straight. At this time, the drive motor 30 can be controlled to output reverse torque and / or the braking system 60 can be controlled to output braking force to brake, thereby shifting the center of gravity of the electric vehicle 10, reducing the axle load of the rear axle of the electric vehicle 10, which is conducive to the rear axle wheels breaking through the road surface adhesion, thus providing favorable conditions for the electric vehicle to drift.

[0116] At the first moment t1, the drive motor 30 is controlled to stop outputting reverse torque and / or the braking system 60 is controlled to stop outputting braking force, so as to avoid affecting the body balance of the electric vehicle 10 during the drifting process.

[0117] It should be understood that the braking force output by the braking system 60 and the reverse torque output by the drive motor 30 can be used in conjunction. Within the capability of the drive system, the reverse torque output by the drive motor 30 is used first for braking. When the capability of the drive system is insufficient, the braking force of the braking system 60 is used as a supplement, resulting in a precise and rapid response.

[0118] It should also be understood that in some cases, there may not be enough time to brake, and transferring the load on the rear wheels of an electric vehicle is not a necessary condition for drifting, so braking may not be necessary before the first moment.

[0119] In one embodiment, at a first time t1, the steering wheel rotation angle of the electric vehicle 10 increases as the speed of the electric vehicle 10 increases, and the steering wheel rotation angle of the electric vehicle 10 decreases as the distance between the electric vehicle 10 and the obstacle increases.

[0120] The faster the electric vehicle 10 travels or the closer it is to the obstacle, the shorter the time it takes to hit the obstacle. Therefore, a larger drift angle is needed to avoid the obstacle. Consequently, the steering wheel angle increases with increasing vehicle speed and decreases with decreasing distance from the obstacle. Conversely, the slower the electric vehicle 10 travels or the farther it is from the obstacle, the longer the time it takes to hit the obstacle. This allows for a greater margin in the drift angle needed to avoid the obstacle. Therefore, the steering wheel angle decreases with decreasing vehicle speed and decreases with increasing distance from the obstacle.

[0121] At the first moment t1, the electric vehicle 10 begins to turn, and the steering wheel of the electric vehicle 10 is turned to generate a side slip angle and lateral force.

[0122] Referring again to Figures 4 and 5, at the second time t2 after the first time t1, the drive torque of the two rear wheels of the electric vehicle 10 is increased.

[0123] At the second moment t2, the driving torque of the two rear wheels of the electric vehicle 10 increases, exceeding the road surface adhesion, and the rear wheels begin to slip. The lateral force on the electric vehicle 10 exceeds the lateral friction limit of the tires, causing the electric vehicle 10 to sideslip. The wheels travel along the tangent of the vehicle's circumference, and the electric vehicle 10 drifts. The essence of achieving drift is to precisely control the electric vehicle 10 to be in a critical stable state of oversteering, with the rear wheels exceeding the critical adhesion limit, intentionally causing the vehicle to sideslip. This requires precise and rapid observation of the road surface adhesion limit to achieve effective control of drift and obstacle avoidance.

[0124] It should be understood that the second moment t2 can be very close to the first moment t1. The electric vehicle 10 can adjust the increase of the driving torque of the rear wheels after the steering wheel is turned, or it can start adjusting the increase of the driving torque of the rear wheels during the steering wheel rotation.

[0125] When the adhesion of the wheel to the road surface changes, the speed and torque of the drive motor 30 used to drive the wheel will also change. Therefore, the change in road surface adhesion can be sensed and observed by detecting the change in the speed of the drive motor 30 through the resolver sensor. The actual torque output by the drive motor 30 reflects the road surface adhesion to a certain extent. Thus, the road surface adhesion can be observed accurately and quickly in real time based on the resolver signal and torque signal.

[0126] In one embodiment, at a second time t2, the drive torque of the two rear wheels of the electric vehicle 10 is increased to a target value, which increases with the speed of the electric vehicle 10 and decreases with the distance between the electric vehicle 10 and the obstacle.

[0127] This target value is greater than the road surface adhesion capacity, which can be detected based on the resolver signal and the output torque of the drive motor. This prevents the target value from far exceeding the road surface adhesion capacity, which could lead to excessive slippage and cause danger.

[0128] The faster the electric vehicle 10 travels or the closer it is to the obstacle, the shorter the time it takes for the electric vehicle 10 to hit the obstacle. Therefore, the rear wheels of the electric vehicle 10 need to slip more quickly. Thus, the drive torque controlling the rear wheels increases with increasing speed and decreases with decreasing distance from the obstacle. Conversely, the slower the electric vehicle 10 travels or the farther it is from the obstacle, the longer the time it takes for it to hit the obstacle. This allows for more margin of error in the rear wheel slippage. Therefore, the drive torque controlling the rear wheels decreases with decreasing speed and decreases with increasing distance from the obstacle.

[0129] Referring again to Figures 4 and 5, in one embodiment, between the second time t2 and the third time t3, the drive torque of the two rear wheels is controlled to be greater than the drive torque of the two front wheels.

[0130] During a drift, the front wheels should maintain traction. As the steering wheels, if they lose traction first, it will result in a partial or near-complete loss of grip, reducing or eliminating steering effectiveness. With the same steering wheel angle, the actual turning angle produced by the vehicle will be smaller than when there is traction, leading to understeer. For the rear wheels, they are in a critical stability range, within the non-linear range of the tire's friction limit circle, and are prone to sideslip. The goal of controlling the rear wheels is to cause them to lose or partially lose traction, causing the electric vehicle to fishtail. Therefore, controlling the drive torque of the rear wheels to be greater than that of the front wheels can provide favorable conditions for drifting and keep the electric vehicle's drift process under control.

[0131] In one embodiment, the control method further includes controlling the slip ratio of the two rear wheels to be greater than a preset value between the second time t2 and the third time t3.

[0132] The rotational speed of the drive motor can be obtained through the resolver signal from the resolver sensor. The angular velocity of the wheels can be calculated from the drive motor speed and the transmission ratio of the electric vehicle. Combined with the wheel radius and the speed of the electric vehicle, the slip ratio of each wheel can be obtained. The electric vehicle can adjust the drive torque of the rear wheels based on the slip ratio of the rear wheels. For the rear wheels, during drifting, it is desirable for the slip ratio of the rear axle wheels to be within the critical stable range, within the nonlinear range of the tire's friction limit circle, tending towards sideslip. By controlling the slip ratio of the two rear wheels to be greater than a preset value, the electric vehicle can be in a drifting state.

[0133] In one embodiment, between a second time t2 and a third time t3, the drive torque of the rear wheel of the electric vehicle 10 is controlled to vary with the change in the sideslip angle of the center of gravity of the electric vehicle 10.

[0134] The electric vehicle 10 can detect information about itself and obstacles based on acquired perception data and plan a drift obstacle avoidance path. Based on this path and the actual path of the electric vehicle, the target sideslip angle of the electric vehicle 10 during the drift obstacle avoidance process can be determined. Therefore, the electric vehicle 10 controls the magnitude of the rear wheel drive torque according to its actual sideslip angle. When the sideslip angle is less than the target sideslip angle, the drive torque of the rear wheels is increased; when the sideslip angle is greater than the target sideslip angle, the drive torque of the rear wheels is decreased.

[0135] In one embodiment, between a second time t2 and a third time t3, the drive torque of the rear wheel of the electric vehicle 10 is different from the torque indicated by the opening of the accelerator pedal.

[0136] Between the second time point t2 and the third time point t3, the electric vehicle is in the process of drifting and avoiding obstacles. The driving torque of the rear wheels is different from the torque indicated by the accelerator pedal opening. The driving torque of the rear wheels does not change with the change of the brake pedal opening. At this time, the torque is directly determined by the closed loop of the motor controller 40, which is different from the torque indicated by the accelerator pedal opening.

[0137] Referring to Figures 4 and 5, at the third time t3 after the second time t2, the distance between the electric vehicle 10 and the obstacle is greater than the second preset distance, and the driving torque of the two rear wheels is reduced.

[0138] At the third moment t3, the electric vehicle 10 changed its driving path by drifting, avoiding the obstacle and gradually moving away from it. The distance between the electric vehicle 10 and the obstacle increased to a distance greater than the second preset distance. At this point, the obstacle avoidance goal was achieved, and the drifting could be stopped. The driving torque of the two rear wheels was reduced so that the driving torque of the two rear wheels was within the road surface adhesion limit range, and slippage no longer occurred.

[0139] Referring again to Figures 4 and 5, in one embodiment, at a fourth time t4 after the third time t3, the drive torque of the two rear wheels is reduced to zero, and the braking system 60 of the electric vehicle 10 is increased to increase the output braking force.

[0140] At the fourth moment t4, after the electric vehicle 10 completes the drift obstacle avoidance operation, the electric vehicle 10 can be controlled to stop. The driving torque is controlled to be reduced to zero and the braking system 60 is controlled to output braking force to brake the electric vehicle and bring it to a stop.

[0141] Furthermore, it can also control the steering wheel of the electric vehicle 10 to return to center.

[0142] It should be understood that after the third moment t3, the electric vehicle 10 can still be controlled to continue driving, that is, the drive torque of the two rear wheels can be controlled to be equal to the torque indicated by the accelerator pedal opening.

[0143] In one embodiment, after a first moment t1, in response to changes in the opening of the accelerator pedal, the opening of the brake pedal, or the steering wheel angle operated by the user, the steering wheel rotation of the electric vehicle 10 is stopped and the drive torque of the two rear wheels is controlled to be equal to the torque indicated by the opening of the accelerator pedal.

[0144] It should be understood that drifting obstacle avoidance is mainly controlled in the intelligent driving or autonomous driving scenarios of electric vehicles 10. When the user intervenes in the process, the human driving signal should take priority. When the driver is detected to have made an active operation, such as turning the steering wheel, pressing the accelerator pedal or pressing the brake pedal, the electric vehicle 10 judges that the driver has intervened, stops the automatic drifting obstacle avoidance, and responds to the driver's operation to take control.

[0145] According to the solution of this application, when the distance to an obstacle is close, the steering is controlled and the torque output of the rear wheels is adjusted so that the rear wheels break through the critical adhesion limit. The electric vehicle is automatically controlled by multiple systems to drift in a controlled manner, avoiding collision with the obstacle. This improves the stability of obstacle avoidance operation, and the response is precise and rapid, effectively improving vehicle safety.

[0146] The control architecture of the vehicle controller and the control flow of drift obstacle avoidance provided in the embodiments of this application will be described below with reference to Figures 6 and 7.

[0147] It should be understood that the vehicle controller provided in this application may be a vehicle controller 20, a motor controller 40, an intelligent driving controller 70, or other separately configured controllers with control capabilities.

[0148] In one embodiment, the vehicle controller can be integrated into a separate power domain controller or into the motor controller 40. If integrated into the motor controller 40, the drift obstacle avoidance path information planned by the intelligent driving controller and the chassis CAN information need to be transmitted to the motor controller 40. The motor controller 40 is also directly connected to components such as the steering system. The motor controller 40 directly monitors changes in road surface adhesion in real time based on the resolver signal from the drive motor 30, thereby reducing torque control delay by at least 20ms. The motor controller also sends braking signals to the braking system 60 and steering signals to the steering system. Thus, the drive system, braking system 60, and steering system cooperate to achieve controlled drift.

[0149] In one embodiment, the vehicle controller can also be integrated into the vehicle controller 20. The motor controller sends the resolver signal or detected changes in road surface adhesion to the vehicle controller 20 via CAN communication. The vehicle controller 20 combines the distance to obstacles obtained from the sensing system with the drift obstacle avoidance path information planned by the intelligent driving controller to control drift obstacle avoidance. It sends torque signals to the motor controller 40, braking signals to the braking system 60, and steering signals to the steering system. Thus, the drive system, braking system 60, and steering system cooperate to achieve controlled drift.

[0150] The vehicle controller can integrate longitudinal and lateral control into a single controller, and coordinate drive and braking control to achieve joint control, reduce latency, and improve control accuracy and response speed.

[0151] As shown in Figure 6, the perception system of electric vehicle 10 perceives information about the actual vehicle and obstacles, and the intelligent driving controller 70 plans a drift obstacle avoidance path. The vehicle controller performs drift obstacle avoidance control based on the actual path of electric vehicle 10 (including signals such as heading angle, yaw angle, and vehicle speed of electric vehicle 10) and the target drift obstacle avoidance path (including parameters such as target center of gravity sideslip angle, target yaw rate, and target vehicle speed).

[0152] The vehicle controller observes the actual vehicle's sideslip angle and path parameters using resolver and torque signals. Through adjustments by the vehicle controller, it outputs torque and steering angle / steering torque commands to the actuators. The torque command specifies the target driving torque for the drive system, while the steering angle / steering torque command specifies the actual steering angle / actual steering torque for the steering system.

[0153] The vehicle controller monitors the road surface adhesion in real time and adjusts the output torque of the drive motor 30 to make the rear wheels break through the critical adhesion limit, intentionally causing slippage and creating favorable conditions for the vehicle to drift.

[0154] In one embodiment, the vehicle controller can establish a vehicle dynamics model based on the following formula:

[0155] Where ω is the yaw rate. This represents the rate of change of yaw angular velocity, where β is the sideslip angle of the center of mass. Let F be the rate of change of the sideslip angle of the center of mass, a be the distance of the center of mass from the front axis, b be the distance of the center of mass from the rear axis, and F be the distance of the sideslip angle of the center of mass. yf F is the lateral force on the front wheel. yr F is the lateral force on the rear wheel, Iz is the moment of inertia, and F is the moment of inertia. xr δ is the longitudinal force of the rear wheel, δ is the steering angle of the front wheel, and m is the mass of the vehicle. Let be the rate of change of vehicle speed, e be the lateral error between the actual vehicle position and the target path, and ΔΦ be the heading angle error. This can be expressed in state-space form:

[0156] Where, x(t)=[ω β V e] T u(t)=[δ F xr ] T .

[0157] In one embodiment, the vehicle controller uses x(t) as the control objective and u(t) as the control variable to perform path control on the electric vehicle 10. Unlike other path tracking and control methods, the key control objective for drift obstacle avoidance is a large centroid sideslip angle, therefore the weight of the centroid sideslip angle is relatively large.

[0158] Furthermore, the longitudinal control variable based on the above vehicle dynamics model is F. xr This needs to be converted into a rear-wheel drive torque indication and sent to the motor controller 40 for drive motor torque control.

[0159] T r =F xr ×r / RR.

[0160] Where r is the tire radius and RR is the reduction ratio.

[0161] The vehicle controller controls the rear-wheel drive torque to exceed the critical road surface adhesion limit (Tr> road surface adhesion limit), thereby achieving drift.

[0162] The vehicle controller uses the resolver signal of the drive motor 30 to accurately determine the slip rate and perform millisecond-level closed-loop control. At the same time, it accurately identifies the adhesion ability of the corresponding wheel / axle of the electric drive to the road surface during slip.

[0163] Referring to Figures 4, 5, and 6, in one embodiment, during the operation of the electric vehicle 10 at a speed greater than a preset speed, at a first moment t1 after the distance between the electric vehicle 10 and the obstacle becomes less than a preset distance, the steering wheel of the electric vehicle is controlled to turn. At a second moment t2 after the first moment t1, the drive torque of the two rear wheels of the electric vehicle 10 is increased.

[0164] As shown in Figures 4 and 5, in one embodiment, the sensing system of the electric vehicle 10 is used to detect the driving path of the electric vehicle 10 and the distance between the electric vehicle 10 and the obstacle. At a first moment t1, the sensing system detects that the distance between the electric vehicle 10 and the obstacle is less than a preset distance and sends a distance signal to the vehicle controller. In response to the distance signal, the vehicle controller sends a steering angle command to the steering system. The steering system, in response to the steering angle command, controls the steering wheel of the electric vehicle to turn, causing the electric vehicle to generate a sideslip angle and lateral force. At a second moment after the first moment t1, the distance between the electric vehicle 10 and the obstacle further decreases. The vehicle controller sends a torque command to the drive system. In response to the torque command, the drive system controls the two rear wheels of the electric vehicle to increase the drive torque, breaking through the road surface adhesion. The rear wheels begin to slip, and the lateral force on the electric vehicle exceeds the lateral friction limit of the tires, thus causing the electric vehicle to sideslip. The wheels travel along the tangent of the vehicle body circumference, and the electric vehicle drifts, thereby allowing the electric vehicle 10 to avoid the obstacle. It should be understood that the second moment t2 can be very close to the first moment t1. The electric vehicle 10 can adjust the increase of the driving torque of the rear wheels after the steering wheel is turned, or it can start adjusting the increase of the driving torque of the rear wheels during the steering wheel rotation. In this application, the driving torque of the wheel can be understood as the torque output by the drive motor used to drive the wheel. The road surface adhesion coefficient is the magnitude of the friction between the wheel and the road, and the magnitude of the road surface adhesion coefficient has an important impact on the safety and stability of vehicle driving. The road surface adhesion coefficient is affected by a variety of factors, including road surface material, humidity, temperature, tire type, and wear degree. The corresponding road surface adhesion coefficient may be different under different road surface conditions and weather conditions. When the adhesion force of the wheel on the road surface changes, the speed and torque of the drive motor used to drive the wheel will also change. Therefore, the change in road surface adhesion can be perceived and observed by detecting the change in the speed of the drive motor through the resolver sensor. The actual torque output by the drive motor reflects the road surface adhesion capability to a certain extent. Thus, the road surface adhesion capability can be observed accurately and quickly in real time based on the resolver signal and torque signal. According to the solution in this application, the road surface adhesion capability is observed in real time, and the rear wheel drive torque is adjusted to make the rear wheel break through the critical adhesion limit. The rear wheel is actively controlled to slip, creating favorable conditions for the vehicle to drift. This makes the drift obstacle avoidance process reliably controllable and improves the vehicle's safety.

[0165] As shown in Figure 7, the control flow for drift obstacle avoidance is as follows:

[0166] First, the vehicle controller receives input signals, including the vehicle's driving path, target path, wheel speed, drive motor torque, drive motor speed, and drift obstacle avoidance enable signal.

[0167] The motor controller feeds back the actual torque based on the vehicle wheel speed, motor speed, torque signal, and the road surface adhesion corresponding to the current wheel / axle.

[0168] Then, when the distance between the electric vehicle 10 and the obstacle is detected to be less than a preset distance, the vehicle controller determines the vehicle speed to see if it is greater than a preset speed but less than a speed limit. If the speed is within the applicable range for drift obstacle avoidance, drift obstacle avoidance control is performed.

[0169] For specific drift obstacle avoidance control methods, please refer to the above text.

[0170] Next, the target's center of gravity sideslip angle and target yaw angle are calculated based on the drift obstacle avoidance path.

[0171] The vehicle controller calculates the drive motor torque and steering angle based on the road surface adhesion and sends them to the motor controller 40 and the steering system, respectively.

[0172] Finally, the motor controller controls the drive motor to output the calculated drive torque, and the steering system controls the electric vehicle 10 to calculate the steering angle to complete the drift and obstacle avoidance.

[0173] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for drifting and obstacle avoidance in electric vehicles, characterized in that, The control method is used to control the steering system and drive system of the electric vehicle during its travel at a speed greater than a preset speed, so that the electric vehicle avoids detected obstacles. The control method includes: At the first moment after the distance between the electric vehicle and the obstacle is less than a preset distance, the steering wheel of the electric vehicle is controlled to turn. At a second moment following the first moment, the drive torque of the two rear wheels of the electric vehicle is increased.

2. The control method according to claim 1, characterized in that, The control method further includes: At a third moment following the second moment, the distance between the electric vehicle and the obstacle is greater than a second preset distance, and the driving torque of the two rear wheels is reduced.

3. The control method according to claim 2, characterized in that, The control method further includes: At the fourth moment following the third moment, the driving torque of the two rear wheels is reduced to zero, and the braking system of the electric vehicle is increased to increase the output braking force.

4. The control method according to claim 2, characterized in that, The control method specifically includes: Between the second and third time points, the drive torque of the two rear wheels is controlled to be greater than the drive torque of the two front wheels.

5. The control method according to any one of claims 1-4, characterized in that, The control method further includes: Before the first moment, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, the drive motor of the electric vehicle is controlled to output a reverse torque, and the drive motor is controlled to stop outputting the reverse torque at the first moment. The direction of the reverse torque is opposite to the rotational speed direction of the drive motor.

6. The control method according to any one of claims 1-5, characterized in that, The control method further includes: Before the first moment, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, the braking system of the electric vehicle is controlled to output braking force to the four wheels of the electric vehicle, and the braking force output by the braking system is controlled to be reduced to zero at the first moment.

7. The control method according to claim 2, characterized in that, The control method further includes: Between the second and third time points, the slip ratio of the two rear wheels is controlled to be greater than a preset value.

8. The control method according to any one of claims 1-7, characterized in that, The control method specifically includes: At the first moment, the steering wheel rotation angle of the electric vehicle increases as the speed of the electric vehicle increases, and the steering wheel rotation angle of the electric vehicle decreases as the distance between the electric vehicle and the obstacle increases.

9. The control method according to any one of claims 1-8, characterized in that, The control method specifically includes: At the second moment, the drive torque of the two rear wheels of the electric vehicle is increased to a target value, which increases with the speed of the electric vehicle and decreases with the distance between the electric vehicle and the obstacle.

10. The control method according to claim 2, characterized in that, The control method specifically includes: Between the second and third time points, the driving torque of the rear wheels of the electric vehicle is controlled to vary with the sideslip angle of the electric vehicle's center of gravity.

11. The control method according to claim 2, characterized in that, The control method further includes: Between the second and third time points, the drive torque controlling the rear wheels of the electric vehicle differs from the torque indicated by the accelerator pedal opening.

12. The control method according to any one of claims 1-11, characterized in that, The control method further includes: After the first moment, in response to changes in the opening of the accelerator pedal, the opening of the brake pedal, or the angle of the steering wheel caused by the user's operation, the steering wheel rotation of the electric vehicle is stopped and the driving torque of the two rear wheels is controlled to be equal to the torque indicated by the opening of the accelerator pedal.

13. The control method according to any one of claims 1-12, characterized in that, The control method further includes: Before the first moment, the user controls the electric vehicle to activate the automatic obstacle avoidance mode by touching the central control screen of the electric vehicle or activating the automatic obstacle avoidance button. The automatic obstacle avoidance mode is used to control the steering system and drive system of the electric vehicle to avoid obstacles while the electric vehicle is traveling at a speed greater than a preset speed.

14. A vehicle controller, characterized in that, The vehicle controller is used to implement the control method as described in any one of claims 1-13.

15. An electric vehicle, characterized in that, The electric vehicle includes the vehicle controller, steering system, and drive system as described in claim 14; wherein: The drive system includes a motor controller and a drive motor, wherein the motor controller is used to control the drive motor to output drive torque to the two rear wheels of the electric vehicle; The steering system is used to control the steering angle of the two front wheels of the electric vehicle.

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