Control method for drift obstacle avoidance of electric vehicle, vehicle controller and electric vehicle

Abstract

The application discloses a control method for drift obstacle avoidance of an electric vehicle, a vehicle controller and the electric vehicle, and relates to the field of new energy vehicles, and can be applied to pure electric vehicles and hybrid vehicles. The control method is used for controlling a steering system and a driving system of the electric vehicle to make the electric vehicle avoid a detected obstacle during a driving process of the electric vehicle with a vehicle speed greater than a preset vehicle speed. The control method comprises the following steps: at a first time point when a distance between the electric vehicle and the obstacle is less than a preset distance, a steering wheel of the electric vehicle is controlled to rotate. At a second time point after the first time point, driving torques of two rear wheels of the electric vehicle are controlled to increase. According to the scheme, the electric vehicle is automatically controlled to drift, collision with the obstacle is avoided, the stability of obstacle avoidance operation is improved, response is accurate and rapid, and the safety of the vehicle is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric vehicles, and more particularly, to a control method for avoiding obstacles by drifting for an electric vehicle, a vehicle controller and an electric vehicle. BACKGROUND

[0002] In the process of driving an electric vehicle, in the case that there is an obstacle on the driving path of the electric vehicle, if the distance between the electric vehicle and the obstacle is too close, it is not the best way to avoid collision or reduce collision loss by braking. At this time, the driver can take the action of drifting by controlling the steering wheel and the accelerator, so as to avoid collision of the vehicle. However, drifting usually requires the driver to be proficient in driving skills and have certain requirements for the timing of operation. In the extreme scenario that the distance between the electric vehicle and the obstacle is too close, it is difficult for the driver to perform drifting to achieve effective obstacle avoidance. Therefore, how to effectively control the vehicle to drift to avoid obstacles is a problem to be solved. SUMMARY

[0003] The present application provides a control method for avoiding obstacles by drifting for an electric vehicle, a vehicle controller and an electric vehicle. When the distance to the obstacle is close, the steering is controlled and the rear wheel torque output is adjusted to make the rear wheel break through the critical adhesion limit, the electric vehicle is automatically controlled to drift, the collision with the obstacle is avoided, the stability of the obstacle avoidance operation is improved, the response is accurate and rapid, and the vehicle safety is effectively improved.

[0004] In a first aspect, the present application provides a control method for avoiding obstacles by drifting for an electric vehicle. The control method is used to control a steering system and a driving system of the electric vehicle to make the electric vehicle avoid a detected obstacle in the process of driving the electric vehicle at a vehicle speed greater than a preset vehicle speed. The control method comprises: controlling a steering wheel of the electric vehicle to rotate at a first time after a distance between the electric vehicle and the obstacle is less than a preset distance. At a second time after the first time, the driving torque of two rear wheels of the electric vehicle is increased.

[0005] The electric vehicle can be an electric vehicle or a hybrid electric vehicle. The electric vehicle can be a distributed drive motor or a centralized drive motor architecture, having multiple drive motors and multiple motor controllers. The drive motor can be a wheel motor or a hub motor, and the drive motor can independently drive one wheel of the vehicle.

[0006] Drifting is a special driving skill of a vehicle, which makes the rear wheels lose or greatly reduce the frictional grip with the road surface when the vehicle is turning, so that the vehicle produces excessive steering, the rear part swings outward, and the vehicle slides through the turn. This process requires the driver to have high skills and sensitive control ability of the vehicle dynamics through the coordination of the steering wheel, accelerator and brake. One way of drifting is to make the lateral adhesion of the tire drop or disappear by driving. It is difficult for the driver to operate the steering wheel and the driving system to accurately complete drifting in an obstacle avoidance scenario. The electric vehicle drifting obstacle avoidance control method provided in the application can be used to automatically control the electric vehicle to complete the drifting obstacle avoidance operation without the intervention of the driver, or to assist the driver to complete the drifting obstacle avoidance operation with only a small amount of operation.

[0007] The electric vehicle can detect the environment around the electric vehicle and the running state information of the electric vehicle through a perception system. The perception system can include cameras, lidar, millimeter wave radar and other sensors for sensing the surrounding environment and collecting and processing environmental information and in-vehicle information, mainly involving road boundary monitoring, vehicle detection, pedestrian detection and other technologies. The perception system can also include speed sensors, acceleration sensors, inertial measurement units and other sensors for detecting vehicle body state and electric vehicle travel information. The perception data signal can include relative distance, relative speed, relative acceleration, lane information and other information. The perception signal can also include electric vehicle speed, acceleration, roll angle, yaw angle and other information. The electric vehicle can detect the information of the electric vehicle and the obstacle according to the obtained perception data, and plan a driving path. The electric vehicle can detect the distance between the electric vehicle and the obstacle in real time through cameras, radars and other sensors, and determine whether to perform drifting obstacle avoidance control according to the vehicle speed and the distance from the obstacle.

[0008] During the driving process of the electric vehicle at a speed greater than a preset speed, when it is detected that the distance between the electric vehicle and the obstacle is less than a preset distance, drifting obstacle avoidance control is started. It should be understood that when the distance between the electric vehicle and the obstacle is less than the preset distance, the electric vehicle may not be able to avoid a collision or may have a more serious collision when starting emergency braking from the preset speed, so the drifting obstacle avoidance control method of the electric vehicle is started to avoid the obstacle by controlling the electric vehicle to drift. The preset speed and the preset distance can be pre-calibrated according to real vehicle experiments and / or model calculations, or can be pre-set by considering the overall vehicle demand and vehicle performance.

[0009] The vehicle speed of the electric vehicle is greater than the preset vehicle speed and less than the vehicle speed limit value at the first moment. The vehicle speed of the electric vehicle is also an important factor affecting the obstacle avoidance. By detecting the vehicle speed of the electric vehicle in real time, it can be determined whether to perform the drift obstacle avoidance control. It is easy to understand that the vehicle speed at which the electric vehicle can perform the drift obstacle avoidance not only has a lower limit, but also has an upper limit. When the vehicle speed of the electric vehicle is greater than or equal to the vehicle speed limit value, no matter whether the electric vehicle adopts the emergency braking or the drift obstacle avoidance method, it is possible that the collision with the obstacle cannot be avoided.

[0010] At the first moment, the electric vehicle starts to turn, and the steering wheel of the electric vehicle is controlled to rotate, so that the electric vehicle generates a side slip angle and a lateral force.

[0011] At the second moment, the driving torque of the two rear wheels of the electric vehicle is increased, the road adhesion is broken through, the rear wheels start to slip, the lateral force received by the electric vehicle is greater than the lateral friction limit of the tire, so that the electric vehicle side slips, and the wheels travel along the circumferential tangent direction of the vehicle body, and the electric vehicle drifts.

[0012] It should be understood that the second moment can be very close to the first moment, and the electric vehicle can adjust the driving torque of the rear wheels to increase after the steering wheel is rotated, or can start to adjust the driving torque of the rear wheels to increase during the steering wheel rotation.

[0013] In this application, the driving torque of the wheel can be understood as the torque output by the driving motor for driving the wheel.

[0014] The road adhesion coefficient is the friction between the wheel and the road, and the size of the road adhesion coefficient has an important influence on the safety and stability of the vehicle. The road adhesion coefficient is affected by many factors, including road material, humidity, temperature, tire type and wear degree, etc. Under different road conditions and weather conditions, the corresponding road adhesion coefficient may be different. When the adhesion of the wheel on the road changes, the speed and torque of the driving motor for driving the wheel also change, so the change of the road adhesion can be perceived and observed by detecting the driving motor speed change through the resolver sensor, and the actual torque actually output by the driving motor reflects the adhesion capacity of the road to a certain extent, so the road adhesion capacity can be observed in real time, accurately and quickly according to the resolver signal and the torque signal.

[0015] According to the scheme of the present application, the road adhesion capacity is observed in real time, the driving torque of the rear wheels is adjusted to make the rear wheels break through the critical adhesion limit, the rear wheels are actively controlled to slip, and the favorable conditions for the vehicle to drift are created, so that the drift obstacle avoidance process is reliably controlled, and the safety of the vehicle is improved.

[0016] With reference to the first aspect, in some implementations of the first aspect, the control method further includes: at a third time after the second time, the distance between the electric vehicle and the obstacle is greater than the second preset distance, and the driving torque of the two rear wheels is controlled to decrease.

[0017] At the third time, the electric vehicle changes the driving trajectory by drifting, avoids the obstacle and gradually moves away from the obstacle, the distance between the electric vehicle and the obstacle increases to be greater than the second preset distance, at this time, the obstacle avoidance target is completed, the drifting can be stopped, the driving torque of the two rear wheels is controlled to decrease, so that the driving torque of the two rear wheels is within the road adhesion limit range and no slip occurs. The second preset distance can be pre-calibrated according to real vehicle experiments and / or model calculations, or can be pre-set by comprehensively considering the vehicle demand and vehicle performance.

[0018] 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, and also includes the distance between the body of the electric vehicle and the obstacle. The electric vehicle can also determine whether to complete obstacle avoidance according to the actual driving trajectory of the electric vehicle. When the obstacle is no longer located on the actual driving trajectory of the electric vehicle, it can also be considered that the obstacle avoidance is completed.

[0019] According to the scheme of the present application, after the electric vehicle avoids the obstacle by drifting, the driving torque of the rear wheels is controlled to decrease, so that the rear wheels stop slipping to obtain sufficient grip, the electric vehicle exits the drifting state, and other collisions caused by continuous drifting of the electric vehicle are avoided, thereby improving the safety and controllability of the electric vehicle.

[0020] With reference to 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 controlled to decrease to zero, and the brake system of the electric vehicle is controlled to increase the output braking force.

[0021] At the fourth time, after the electric vehicle completes the drifting obstacle avoidance operation, the electric vehicle can be controlled to stop, the driving torque is controlled to decrease to zero, and the brake system is controlled to output the braking force to brake the electric vehicle, so that the electric vehicle stops. Further, the steering wheel of the electric vehicle can also be controlled to return to normal.

[0022] It should be understood that after the third time, the electric vehicle can also be controlled to continue driving, that is, the driving torque of the two rear wheels is controlled to be equal to the torque indicated by the opening degree of the accelerator pedal.

[0023] According to the scheme of the present application, after the electric vehicle completes the drifting obstacle avoidance, the electric vehicle is controlled to stop, so as to avoid the danger caused by continuous driving, thereby improving the safety and controllability of the electric vehicle.

[0024] With reference to the first aspect, in some implementations of the first aspect, the control method specifically includes: between the second time and the third time, controlling the driving torque of the two rear wheels to be greater than the driving torque of the two front wheels.

[0025] During the drifting process, the front wheels should maintain the grip. The front wheels are steering wheels, and if the front wheels lose the grip first, it will lead to losing part or almost all of the grip, and the steering effect will be reduced or lost. With the same steering wheel angle, the actual vehicle produces a smaller turning angle than when there is grip, resulting in understeering. For the rear wheels, the rear wheels are in the critical stability interval and in the nonlinear interval of the tire friction limit circle, and tend to slide sideways. The control target of the rear wheels is to make the rear wheels lose or partially lose the grip, so that the electric vehicle spins. Therefore, by controlling the driving torque of the rear wheels to be greater than the driving torque of the front wheels, favorable conditions for drifting can be provided, and the drifting process of the electric vehicle can be in a controlled state.

[0026] According to the scheme of the present application, during the drifting process, the driving torque of the rear wheels is controlled to be greater than the driving torque of the front wheels, which provides a critical condition for drifting, makes the drifting obstacle avoidance controlled, and improves the safety and stability of the vehicle.

[0027] With reference to the first aspect, in some implementations of the first aspect, the control method further includes: before the first time, 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 driving motor of the electric vehicle to output a reverse torque and stopping the driving motor from outputting the reverse torque at the first time, the direction of the reverse torque being opposite to the direction of the rotation speed of the driving motor.

[0028] The reverse torque can also be understood as a driving torque with a negative value. The driving motor includes a stator winding and a rotor. By outputting alternating current to the three-phase stator winding, the driving torque of the driving motor can be controlled. By adjusting the size of the stator winding current and the phase of the three-phase current through the motor controller, the stator magnetic field strength and direction can be changed, thereby changing the interaction force between the stator and the rotor, i.e., the driving torque of the driving motor. By changing the phase of the three-phase current output to the driving motor, the kinetic energy of the rotor cutting the magnetic field generated by the stator winding is converted into electrical energy input into the power battery, at which time the driving motor outputs a negative torque. By changing the size of the three-phase current output to the driving motor, the motor controller can increase or decrease the driving torque or reverse torque output by the motor.

[0029] When the driving torque of one wheel is negative, the driving motor driving the wheel outputs a reverse torque, the direction of the reverse torque being opposite to the direction of the rotation speed of the driving motor, and the reverse torque is used to brake the wheel.

[0030] The third preset distance can be a distance at which the electric vehicle starts braking, and the third preset distance can be pre-calibrated according to real vehicle experiments and / or model calculation, or pre-set by comprehensively considering the whole vehicle demand and vehicle performance.

[0031] Before the first time, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, the steering wheel has not been turned, and the electric vehicle is still straight driving, the electric vehicle can start braking, at this time, braking can be performed by controlling the driving motor to output a reverse torque, the center of gravity of the electric vehicle is shifted, so that the axle load of the rear axle of the electric vehicle is reduced, which is beneficial to the rear axle wheel breaking through the road adhesion, thereby providing favorable conditions for the electric vehicle to drift. At the first time, the driving motor is controlled to stop outputting the reverse torque to avoid the reverse torque affecting the body balance of the electric vehicle during the drifting process.

[0032] According to the scheme of the present application, braking is performed before drifting, the rear axle load is shifted, and favorable conditions are provided for the electric vehicle to drift, the driving motor is used to output a reverse torque for braking, the response is rapid, and the controllability and stability of the electric vehicle are improved.

[0033] In combination with the first aspect, in some implementations of the first aspect, the control method further includes: before the first time, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the 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 time.

[0034] Before the first time when the drifting starts, the steering wheel has not been turned, and the electric vehicle is still straight driving, at this time, braking can also be performed by the braking system outputting braking force to the wheels, the center of gravity of the electric vehicle is shifted, so that the axle load of the rear axle of the electric vehicle is reduced, which is beneficial to the rear axle wheel breaking through the road adhesion, thereby providing favorable conditions for the electric vehicle to drift. At the first time, the braking system is controlled to stop outputting the braking force to avoid the braking force affecting the body balance of the electric vehicle during the drifting process.

[0035] The control of the braking system to output the braking force and the control of the driving motor to output the reverse torque can also be used cooperatively, within the driving system capability, the driving motor is preferentially used to output the reverse torque for braking, and when the driving system capability is insufficient, the braking force of the braking system is used as a supplement, the response is accurate and rapid.

[0036] According to the scheme of the present application, the driving and braking are cooperatively controlled, the response is accurate and rapid, braking is performed before drifting, the rear axle load is shifted, and favorable conditions are provided for the electric vehicle to drift, and the controllability and stability of the electric vehicle are improved.

[0037] With reference to 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 time and the third time.

[0038] The rotational speed of the driving motor can be obtained through the rotational variable signal of the rotational variable sensor. The angular velocity of the wheel can be calculated through the rotational speed of the driving motor and the transmission ratio of the electric vehicle. The slip ratio of each wheel can be obtained in combination with the wheel radius and the speed of the electric vehicle. The slip ratio in this application can be the slip ratio or the slip rate. The electric vehicle can adjust the driving torque of the rear wheels according to the slip ratio of the rear wheels. For the rear wheels, it is desired that the slip ratio of the wheels of the rear axle is in the critical stable interval during drifting, in the nonlinear interval of the friction limit circle of the tire, and tends to slide sideways. 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.

[0039] According to the scheme of the application, the driving torque of the rear wheels is changed according to the wheel slip ratio, so that the slip ratio of the rear wheels is greater than a preset value, thereby accurately controlling the electric vehicle to be in a drifting state, responding quickly, and improving the controllability and stability of the electric vehicle.

[0040] With reference to the first aspect, in some implementations of the first aspect, the control method specifically includes: at the first time, controlling the steering wheel rotation angle of the electric vehicle to increase with the increase of the speed of the electric vehicle, and controlling the steering wheel rotation angle of the electric vehicle to decrease with the increase of the distance between the electric vehicle and the obstacle.

[0041] The faster the electric vehicle is or the closer the distance between the electric vehicle and the obstacle is, the shorter the time for the electric vehicle to hit the obstacle, and the greater the angle required for drifting to avoid the obstacle. Therefore, the steering wheel rotation angle is controlled to increase with the increase of the speed and the decrease of the distance to the obstacle. The slower the electric vehicle is or the farther the distance between the electric vehicle and the obstacle is, the longer the time for the electric vehicle to hit the obstacle, and the greater the margin for the angle required for drifting to avoid the obstacle. Therefore, the steering wheel rotation angle is controlled to decrease with the decrease of the speed and the increase of the distance to the obstacle.

[0042] According to the scheme of the application, the steering wheel rotation angle of the electric vehicle during drifting to avoid the obstacle is determined according to the speed and the distance to the obstacle, thereby improving the effect of drifting to avoid the obstacle and improving the controllability and safety of the electric vehicle.

[0043] With reference to the first aspect, in some implementations of the first aspect, the control method specifically includes: at the second time, controlling the driving 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.

[0044] The target value is greater than the road adhesion capacity, and the road adhesion capacity can be detected according to the slip signal and the output torque of the driving motor. Thus, the target value is far greater than the road adhesion capacity, which leads to excessive skidding and causes danger.

[0045] The faster the electric vehicle speed or the closer the distance between the electric vehicle and the obstacle, the shorter the time for the electric vehicle to hit the obstacle, and the faster the rear wheel of the electric vehicle needs to skid, so the driving torque of the rear wheel is controlled to increase with the increase of the vehicle speed and the decrease of the distance to the obstacle. The slower the electric vehicle speed or the farther the distance between the electric vehicle and the obstacle, the longer the time for the electric vehicle to hit the obstacle, and the more the degree of skidding of the rear wheel of the electric vehicle, so the driving torque of the rear wheel is controlled to decrease with the decrease of the vehicle speed and the increase of the distance to the obstacle.

[0046] According to the scheme of the present application, the increase value of the driving torque of the rear wheel of the electric vehicle when drifting to avoid obstacles is determined according to the vehicle speed and the distance to the obstacle, which improves the effect of drifting to avoid obstacles and improves the controllability and safety of the electric vehicle.

[0047] In combination with the first aspect, in some implementations of the first aspect, the control method specifically includes: between the second time and the third time, controlling the driving torque of the rear wheel of the electric vehicle to change with the change of the center of mass side slip angle of the electric vehicle.

[0048] The electric vehicle can detect the information of the electric vehicle and the obstacle according to the acquired perception data, and plan a path for drifting to avoid obstacles, and according to the path and the actual path of the electric vehicle, the target center of mass side slip angle in the process of drifting to avoid obstacles of the electric vehicle can be determined. Thus, the electric vehicle controls the size of the driving torque of the rear wheel according to the actual center of mass side slip angle of the electric vehicle, and when the center of mass side slip angle is less than the target center of mass side slip angle, the driving torque of the rear wheel is increased, and when the center of mass side slip angle is greater than the target center of mass side slip angle, the driving torque of the rear wheel is decreased.

[0049] According to the scheme of the present application, the center of mass side slip angle is used as a control parameter in the process of drifting to avoid obstacles of the electric vehicle, which can accurately control the path of drifting to avoid obstacles of the electric vehicle, effectively control the center of mass side slip angle, improve the control stability, avoid the occurrence of uncontrollable danger of the electric vehicle when drifting to avoid obstacles, and improve the controllability and safety of the electric vehicle.

[0050] In combination with the first aspect, in some implementations of the first aspect, the control method further includes: between the second time and the third time, controlling the driving torque of the rear wheel of the electric vehicle to be different from the torque indicated by the opening degree of the accelerator pedal.

[0051] The accelerator pedal in the present application can also be referred to as a throttle pedal or an acceleration pedal. The opening degree of the accelerator pedal can indicate the driving power required by the driver. When the opening degree of the accelerator pedal is larger, the driver requires more driving power, and the driving motor needs to output more torque. When the drift obstacle avoidance control is not performed, the driving motor can output the torque indicated by the opening degree of the accelerator pedal. When the opening degree of the accelerator pedal is larger, the driving motor outputs more torque, and when the opening degree of the accelerator pedal is smaller, the driving motor outputs less torque. The driving torque of the rear wheels changes with the opening degree of the accelerator pedal.

[0052] Between the second time and the third time, the electric vehicle is in the drift obstacle avoidance process, and the driving torque of the rear wheels is different from the torque indicated by the opening degree of the accelerator pedal. The driving torque of the rear wheels does not change with the change of the opening degree of the brake pedal. At this time, the torque is closed-loop controlled by the motor controller, and the driving torque of the rear wheels is directly determined, which is different from the torque indicated by the opening degree of the accelerator pedal.

[0053] According to the scheme of the present application, the driving system internally closes the driving torque of the rear wheels during drift obstacle avoidance, rather than determining the driving torque according to the opening degree of the accelerator pedal, which reduces the signal transmission delay, improves the control accuracy and speed, and improves the safety and efficiency of drift obstacle avoidance.

[0054] In combination with the first aspect, in some implementations of the first aspect, the control method further includes: after the first time, in response to a change in the opening degree of the accelerator pedal, the opening degree of the brake pedal, or the steering angle of the steering wheel operated by the user, stopping controlling the steering of the steering wheel of the electric vehicle and controlling the driving torque of the two rear wheels to be equal to the torque indicated by the opening degree of the accelerator pedal.

[0055] It should be understood that drift obstacle avoidance is mainly a control process in the intelligent driving or automatic driving scenario of an electric vehicle. When the user intervenes in the operation during the process, the human driving signal should be given priority. When it is detected that the driver has performed an active operation, such as turning the steering wheel, stepping on the accelerator pedal, or stepping on the brake pedal, the electric vehicle determines that the driver intervenes and stops the automatic drift obstacle avoidance, and controls in response to the operation of the driver.

[0056] According to the scheme of the present application, the operation of the driver is given priority during the drift obstacle avoidance process. When the driver intervenes, the drift obstacle avoidance is stopped, the flexibility of handling in emergency situations is improved, and the safety and reliability of the electric vehicle are improved.

[0057] In some implementations of the first aspect, the control method further includes: before the first time, the user controls the electric vehicle to start the automatic obstacle avoidance mode by touching a central control screen of the electric vehicle or activating an automatic obstacle avoidance button, the automatic obstacle avoidance mode being used to control the steering system and the driving system of the electric vehicle to avoid obstacles during the driving of the electric vehicle at a speed greater than the preset speed.

[0058] The drift obstacle avoidance can be an optional operation mode of the electric vehicle, and the drift obstacle avoidance control is performed only when the user has started the automatic obstacle avoidance mode in advance before the collision occurs.

[0059] The automatic obstacle avoidance button can be provided on the electric vehicle for the driver to operate. For example, the automatic obstacle avoidance button can be a physical button, and the driver can start the automatic obstacle avoidance mode of the electric vehicle by pressing the physical button, so as to start the drift obstacle avoidance control when the distance between the electric vehicle and the obstacle is less than the preset distance during the driving of the electric vehicle at a speed greater than the preset speed. For another example, the automatic obstacle avoidance button can be a virtual button on the central control screen, and the driver can start the automatic obstacle avoidance mode of the electric vehicle by selecting the automatic obstacle avoidance mode. For another example, the automatic obstacle avoidance button can also be indirectly provided, for example, in combination with a button of the intelligent driving mode or by default starting the automatic obstacle avoidance mode of the electric vehicle when the driver closes other buttons.

[0060] According to the scheme of the present application, the automatic obstacle avoidance switch is provided for the driver to set, which can improve the driving experience of the driver and improve the safety of the electric vehicle.

[0061] In the second aspect, the present application provides a vehicle controller, which is used to execute the control method as described in the first aspect and various implementations thereof.

[0062] The vehicle controller in the present application can be a motor controller of the electric vehicle, or a vehicle controller, or an intelligent driving controller, or a separately provided controller with control capability. The vehicle controller is applicable to an electric vehicle or a hybrid vehicle, the electric vehicle can be a distributed motor or a centralized motor architecture, has multiple driving motors and multiple motor controllers, and the vehicle controller can be any one of the multiple motor controllers.

[0063] The intelligent driving controller in the present application can be a domain controller for implementing functions such as perception, positioning, path planning, decision control, etc. When the electric vehicle is in the intelligent driving mode, the intelligent driving controller performs intelligent active driving or assists the user to drive at this time, and the intelligent driving controller receives the perception data signals sent by the sensors such as radar, camera and the like of the electric vehicle perception component. The intelligent driving controller fuses the information perceived by various sensors and obtains the driving state and lane information of the electric vehicle according to the perception data signals, obtains target acceleration and target speed and the like by analyzing distance, speed, acceleration and the like signals, makes a driving decision / planning based on the fused information, issues an operation command to the vehicle controller, and sends the intelligent driving torque signal to the motor controller by the vehicle controller, so as to output the torque value indicated by the intelligent driving torque signal, and complete intelligent driving.

[0064] In a third aspect, the present application provides an electric vehicle, which comprises the vehicle controller, the steering system and the driving system as described in the second aspect. The driving system comprises a motor controller and a driving motor, and the motor controller is configured to control the driving motor to output driving torque to two rear wheels of the electric vehicle. The steering system is configured to control the steering angle of two front wheels of the electric vehicle.

[0065] The beneficial effects of other aspects can refer to the beneficial effects described in the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 is a schematic diagram of T-type collision of the electric vehicle provided by the embodiments of the present application;

[0067] Figure 2 is a schematic diagram of the electric vehicle provided by the embodiments of the present application;

[0068] Figure 3 is a schematic diagram of the architecture of the electric vehicle provided by the embodiments of the present application;

[0069] Figure 4 is a schematic diagram of the drift obstacle avoidance control process of the electric vehicle provided by the embodiments of the present application;

[0070] Figure 5 is a schematic diagram of the drift obstacle avoidance of the electric vehicle provided by the embodiments of the present application;

[0071] Figure 6 is a schematic diagram of the vehicle controller architecture provided by the embodiments of the present application;

[0072] Figure 7 is a schematic diagram of the drift obstacle avoidance control process of the vehicle controller provided by the embodiments of the present application. DETAILED DESCRIPTION

[0073] The technical solutions in the present application will be described below with reference to the drawings. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, i.e., the present application is not limited to the described embodiments.

[0074] Drifting is a sport that focuses on specific driving techniques. Vehicle drifting is to use excessive steering to make the vehicle laterally run through a curve. Vehicle drifting is to generate lateral and longitudinal forces of the tire through the interaction between the tire and the road surface. When the rear-wheel lateral force exceeds the road adhesion, the tire generates lateral speed, and side slip occurs, and the wheel runs along the circumferential tangent direction of the vehicle body, i.e., drifting occurs. The driver can drift by operating the drive, brake, and steering wheel to achieve a small radius turn to meet the needs of racing, driving pleasure, and narrow area turning. However, drifting by the driver's operation requires the driver to be proficient in driving skills, and ordinary drivers are difficult to achieve. The principle of drifting is to make the rear wheels of the vehicle lose most or all of the grip, while the front wheels can maintain the grip. At this time, as long as the front wheels have a certain lateral force, the vehicle will spin and drift.

[0075] As shown in Figure 1 , when driving at an intersection, especially at an intersection without a traffic light, a T-type collision scenario of two directions may occur, in which one vehicle collides with the side of another vehicle. If the distance between the two vehicles is too close at this time, it is not enough to achieve emergency braking, and a collision may occur. Compared with other collision modes, T-type collision causes more casualties and losses in traffic accidents due to the lack of energy absorption devices in the side structure of the vehicle.

[0076] In one possible implementation, the collision can be avoided by turning to one side and emergency braking.

[0077] It should be understood that if the distance between the two vehicles is close, the angle of turning may not be enough, and the deceleration degree of emergency braking may not be enough to achieve the effect of avoiding collision.

[0078] Based on the above problems, the present application provides a control method for drifting obstacle avoidance of an electric vehicle, a vehicle controller, and an electric vehicle. When the distance from the obstacle is close, the electric vehicle is controlled to turn and adjust the output of the rear-wheel torque so that the rear wheels exceed the critical adhesion limit, and the electric vehicle is automatically controlled to drift, thereby avoiding collision with the obstacle, improving the stability of obstacle avoidance operation, responding accurately and quickly, and effectively improving the safety of the vehicle.

[0079] Figure 2 and Figure 3 is a schematic diagram of the electric vehicle 10 architecture provided by the embodiments of the present application.

[0080] As shown in Figure 2As shown, the electric vehicle 10 includes a vehicle controller 20, a drive system, a brake system 60, an intelligent driving controller 70, a power battery (not shown in the figure), and a plurality of wheels. The drive system includes a drive motor 30 and a motor controller 40. The motor controller 40 is configured to output a current to the drive motor 30 to control the drive motor 30 to output a torque to drive the electric vehicle 10. The intelligent driving controller 70 is configured to plan a driving trajectory according to obstacle information detected by sensors of the electric vehicle 10 and driving information of the electric vehicle 10.

[0081] The vehicle controller in the present application can be the motor controller 40 of the electric vehicle 10, or the vehicle controller 20, or the intelligent driving controller 70, or a separately arranged controller with control capability.

[0082] It can be understood that the electric vehicle 10 in the embodiments of the present application can be any one of different types of vehicles such as a car, a truck, a passenger bus, etc., and can also be a three-wheeled vehicle, a two-wheeled vehicle, or other transportation devices for carrying people or goods, or other types of transportation tools driven by a power battery, and the embodiments of the present application do not limit this. The vehicle includes but is not limited to a pure electric vehicle (pure EV / battery EV), a hybrid electric vehicle (HEV), a range extended electric vehicle (REEV), a plug-in hybrid electric vehicle (PHEV), etc.

[0083] The power battery in the embodiments of the present application can be a lithium ion battery, a lithium metal battery, a lead-acid battery, a nickel-cadmium battery, a nickel-hydrogen battery, a lithium-sulfur battery, a lithium-air battery, or a sodium-ion battery, etc., and the present application does not limit this. The power battery can also supply power to other electrical devices in the vehicle, such as the air conditioner in the vehicle, the vehicle-mounted player, etc.

[0084] The electric vehicle 10 can be a rear-wheel drive vehicle, with two rear wheels driven by the drive motor 30. The electric vehicle 10 can also be a distributed four-wheel drive motor driving architecture, with the drive motor arranged on the driven wheels and controlled by a separate motor controller 40. The electric vehicle 10 can also be a centralized drive motor driving architecture, with the drive motor for driving two front wheels or two rear wheels arranged together. The motor controller 40 can be one or more. The motor controller 40 can be one-to-one corresponding to the drive motor 30, and one motor controller 40 can also correspond to a plurality of drive motors 30. The motor controller 40 is configured to control one or more drive motors 30 to output a torque to drive the electric vehicle 10.

[0085] In one embodiment, such as Figure 3 As shown in (a), the electric vehicle 10 can be a distributed four-motor drive architecture, with the drive motors positioned beside the driving wheels and controlled by individual motor controllers. The electric vehicle 10 can also be as follows: Figure 3 The centralized four-drive motor drive architecture shown in (b) has two drive motors for driving the two front wheels or the two rear wheels set together.

[0086] 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.

[0087] In one embodiment, the electric vehicle 10 may also be as follows: Figure 3 The centralized drive motor architecture shown in (c) uses one drive motor to drive the two front wheels of the electric vehicle 10, and two drive motors to drive the two rear wheels of the electric vehicle 10 respectively.

[0088] 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.

[0089] The vehicle controller provided in this application can be any one of multiple motor controllers.

[0090] 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.

[0091] In one embodiment, the braking system 60 comprises a brake controller and a plurality of wheel end brake devices, the brake controller and the brake pedal are connected. The brake controller can be used to determine the braking force according to the opening of the brake pedal. During the driving process of the driver, when the electric vehicle 10 needs to be braked, the driver steps on the brake pedal, the brake controller receives the brake pedal signal from the brake pedal and outputs the braking force distribution signal to the wheel end brake device, the wheel end brake device is used to receive the braking force distribution signal and output the clamping force to the brake disc according to the indication of the braking force distribution signal, so as to generate the friction braking force, so that the electric vehicle 10 is braked.

[0092] In one embodiment, the motor controller 40 comprises a signal interface, the motor controller 40 is connected to the vehicle controller 20 and other motor controllers 40 through the signal interface. The vehicle controller 20 and the accelerator pedal are connected, the vehicle controller 20 calculates the vehicle torque demand according to the opening of the accelerator pedal during the driving process of the electric vehicle 10, and sends a torque signal to the motor controller 40 according to the vehicle torque demand, and each motor controller 40 controls the corresponding drive motor to output torque according to the indication of the torque signal.

[0093] In one embodiment, each motor controller 40 can also be directly connected to the accelerator pedal and control the corresponding motor to output torque according to the torque signal output by the accelerator pedal.

[0094] In one embodiment, the vehicle controller 20 is connected to the brake pedal through the signal interface, the vehicle controller 20 calculates the vehicle braking demand according to the opening of the brake pedal during the driving process of the electric vehicle 10, and sends a braking signal to the brake controller according to the vehicle braking demand, the brake controller controls the corresponding wheel end brake device to output braking force according to the indication of the braking signal to brake the corresponding wheel.

[0095] In one embodiment, the vehicle controller 20 can also be directly connected to the brake pedal, and control the wheel end brake device to output braking force according to the opening of the brake pedal.

[0096] In one embodiment, each motor controller 40 is connected to the rotary variable sensor through the signal interface, the rotary variable sensor is used to detect the rotating speed of the drive motor 30 controlled by the motor controller 40, and the motor controller 40 is used to receive the signal from the rotary variable sensor. The motor controller 40 can also generate a rotating speed signal according to the signal from the rotary variable sensor and send the rotating speed signal to the other three motor controllers 40. Similarly, each motor controller 40 also receives the rotating speed signal sent by the other three motor controllers 40.

[0097] The resolver sensor can accurately detect the position, direction and speed of the motor rotor, and is responsible for monitoring and extracting the driving motor rotation speed. The sampling rate is high, and the signal is directly connected to the motor controller 40, the signal transmission time is short, and the stability is higher.

[0098] In an embodiment, the motor controller 40 also obtains vehicle signals from the vehicle controller 20 or other sensors of the electric vehicle 10 through the signal interface, and the vehicle signals are used to indicate the vehicle speed, yaw rate, center of mass side slip angle, etc. of the electric vehicle 10.

[0099] In an embodiment, the motor controller 40 can be connected with the vehicle controller 20, the intelligent driving controller 70 and the steering system through 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 the signals are interacted.

[0100] In an embodiment, the electric vehicle 10 comprises an automatic obstacle avoidance button. The automatic obstacle avoidance button is used to start the automatic obstacle avoidance mode, and the automatic obstacle avoidance mode is used to control the steering system and the driving system of the electric vehicle 10 to avoid obstacles during the driving process of the electric vehicle 10 at a speed greater than a preset speed.

[0101] The automatic obstacle avoidance button can be provided on the electric vehicle 10 for the driver to operate. Exemplarily, the automatic obstacle avoidance button can be a physical button, and the driver can press the physical button to start the automatic obstacle avoidance mode of the electric vehicle 10, so as to start the drift obstacle avoidance control when the distance between the electric vehicle 10 and the obstacle is less than a preset distance during the driving process of the electric vehicle 10 at a speed greater than a preset speed. Exemplarily, the automatic obstacle avoidance button can be a virtual button on the center screen, and the driver can select the automatic obstacle avoidance mode to start the automatic obstacle avoidance mode of the electric vehicle 10. Exemplarily, the automatic obstacle avoidance button can also be indirectly provided, for example, combined in the button of the intelligent driving mode or automatically started when the driver closes other buttons.

[0102] It should be understood that the vehicle controller provided in the present application can be the vehicle controller 20, the motor controller 40, the intelligent driving controller 70, or other separately provided controllers with control capability.

[0103] The drift obstacle avoidance control method provided by the embodiments of the present application is used to control the electric vehicle 10 to drift to one side in the case that the electric vehicle 10 encounters an obstacle, and to avoid the obstacle in the way that the electric vehicle is turned too much by drifting, so as to avoid the damage caused by collision. The road adhesion is sensed by the vehicle controller, so that the rear wheel breaks through the road adhesion limit, and the controlled drifting does not need to rely on the operation of the driver. The signal transmission time is short, and the safety of the vehicle is improved. The drift obstacle avoidance control method provided by the embodiments of the present application will be described below in combination with Figure 4 and Figure 5 The drift obstacle avoidance control method and the vehicle controller provided by the embodiments of the present application are described in the first time t1, the second time t2, the third time t3 and the fourth time t4 in the driving process of the electric vehicle 10 with a speed greater than a preset speed. Figure 4 The signal timing diagram of the electric vehicle 10 in the driving process, Figure 4 The distance between the electric vehicle and the obstacle, the steering wheel angle, the rear wheel driving torque, the braking force and the difference between the front and rear wheel driving torques in the driving process of the electric vehicle are included in the embodiments of the present application.

[0104] In an embodiment, before the first time t1, the user controls the electric vehicle to start the automatic obstacle avoidance mode by touching the center 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 the driving system of the electric vehicle 10 to avoid the obstacle in the driving process of the electric vehicle 10 with a speed greater than a preset speed.

[0105] The drift obstacle avoidance can be an optional operation mode of the electric vehicle 10. Only when the user starts the automatic obstacle avoidance mode in advance, the drift obstacle avoidance control is performed when the collision is about to occur.

[0106] In an embodiment, after the automatic obstacle avoidance mode of the control method is activated, the control method provided by the embodiments of the present application includes detecting the distance between the electric vehicle 10 and the obstacle in the driving process of the electric vehicle 10.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] like Figure 4 and Figure 5 As shown, 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.

[0111] At the first time t1, the electric vehicle starts to turn, the steering wheel of the electric vehicle is controlled to rotate, so that the electric vehicle generates a side slip angle and a lateral force. At the second time t2, the driving torque of the two rear wheels of the electric vehicle is increased, the road adhesion is broken through, the rear wheels start to slip, the lateral force received by the electric vehicle is greater than the lateral friction limit of the tire, so that the electric vehicle slides sideways, the wheels travel along the circumferential tangent direction of the vehicle body, and the electric vehicle drifts. It should be understood that the second time t2 can be very close to the first time t1, and the electric vehicle 10 can adjust the driving torque increase of the rear wheels after the steering wheel rotation is completed, or can start to adjust the driving torque increase 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 driving motor for driving the wheel. The road adhesion coefficient is the friction between the wheel and the road, and the size of the road adhesion coefficient has an important influence on the safety and stability of the vehicle. The road adhesion coefficient is affected by many factors, including road material, humidity, temperature, tire type and wear degree, etc. Under different road conditions and weather conditions, the corresponding road adhesion coefficient may be different. When the adhesion of the wheel on the road changes, the speed and torque of the driving motor for driving the wheel will also change, so the change of the road adhesion can be perceived and observed by detecting the change of the driving motor speed through the resolver sensor, and the actual torque output by the driving motor reflects the adhesion capacity of the road to a certain extent, so that the road adhesion capacity can be observed in real time, accurately and quickly according to the resolver signal and the torque signal. According to the scheme of the present application, the road adhesion capacity is observed in real time, the driving torque of the rear wheels is adjusted to make the rear wheels break through the critical adhesion limit, the rear wheels are actively controlled to slip, and the favorable conditions for the vehicle to drift are created, so that the drifting obstacle avoidance process is reliably controlled, and the safety of the vehicle is improved.

[0112] In one embodiment, before the first time t1, at the time t0 when the distance between the electric vehicle 10 and the obstacle is greater than the preset distance and less than the third preset distance, the driving motor 30 of the electric vehicle 10 is controlled to output a reverse torque, and at the first time t1, the driving motor is controlled to stop outputting the reverse torque. The direction of the reverse torque is opposite to the direction of the rotation speed of the driving motor.

[0113] In one embodiment, before the first time t1, at the time t0 when the distance between the electric vehicle 10 and the obstacle is greater than the preset distance and less than the third preset distance, the brake system 60 of the electric vehicle 10 is controlled to output a braking force to the four wheels of the electric vehicle 10, and at the first time t1, the braking force output by the brake system 60 is controlled to decrease to zero.

[0114] When the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, the steering wheel has not been turned, and the electric vehicle 10 is still straight, at this time, braking can be performed by controlling the driving motor 30 to output a reverse torque and / or controlling the braking system 60 to output a braking force, shifting the center of gravity of the electric vehicle 10 so that the axle load of the rear axle of the electric vehicle 10 is reduced, which is beneficial to the rear axle wheels breaking through the road adhesion, thereby providing favorable conditions for the electric vehicle to drift.

[0115] At the first time t1, the driving motor 30 is controlled to stop outputting the reverse torque and / or the braking system 60 is controlled to stop outputting the braking force, so as to avoid affecting the body balance of the electric vehicle 10 during the drifting process.

[0116] It should be understood that the braking force output by the braking system 60 and the reverse torque output by the driving motor 30 can be used cooperatively, and within the driving system capability, the reverse torque output by the driving motor 30 is preferentially used for braking, and when the driving system capability is insufficient, the braking force of the braking system 60 is used as a supplement, which is responsive, accurate and rapid.

[0117] It should also be understood that in some cases, it may not be possible to brake in time, and shifting the load of the rear wheels of the electric vehicle is not a necessary condition for drifting, so braking can also not be performed before the first time.

[0118] In an embodiment, at the first time t1, the steering angle of the electric vehicle 10 is controlled to increase with the increase of the speed of the electric vehicle 10, and the steering angle of the electric vehicle 10 is controlled to decrease with the increase of the distance between the electric vehicle 10 and the obstacle.

[0119] The faster the electric vehicle 10 or the closer the distance between the electric vehicle 10 and the obstacle, the shorter the time for the electric vehicle 10 to hit the obstacle, and the greater the angle required for drifting to avoid the obstacle, so the steering angle is controlled to increase with the increase of the speed and the decrease of the distance from the obstacle. The slower the electric vehicle 10 or the farther the distance between the electric vehicle 10 and the obstacle, the longer the time for the electric vehicle 10 to hit the obstacle, and the greater the margin for the angle required for drifting to avoid the obstacle, so the steering angle is controlled to decrease with the decrease of the speed and the increase of the distance from the obstacle.

[0120] At the first time t1, the electric vehicle 10 starts to turn, and the steering wheel of the electric vehicle 10 is controlled to turn, so that the electric vehicle 10 generates a side slip angle and a lateral force.

[0121] Continuing to refer to Figure 4 and Figure 5 At a second time t2 after the first time t1, the driving torque of the two rear wheels of the electric vehicle 10 is controlled to increase.

[0122] At the second time t2, the driving torque of the two rear wheels of the electric vehicle 10 is increased, the road adhesion is broken through, the rear wheels start to slip, the lateral force received by the electric vehicle 10 is greater than the lateral friction limit of the tire, so that the electric vehicle 10 slides sideways, the wheels travel along the circumferential tangent direction of the vehicle body, and the electric vehicle 10 drifts. The essence of realizing drifting is to accurately control the electric vehicle 10 to be in a critical stable state of oversteering, the rear wheels break through the critical adhesion limit, and the vehicle is intentionally caused to slide sideways. It is necessary to accurately and quickly observe the adhesion limit capability of the road to effectively control the drifting obstacle avoidance.

[0123] It should be understood that the second time t2 can be very close to the first time t1, and the electric vehicle 10 can adjust the driving torque of the rear wheels to increase after the steering wheel rotation is completed, or can start to adjust the driving torque of the rear wheels to increase during the steering wheel rotation.

[0124] When the adhesion of the wheels on the road changes, the speed and torque of the driving motor 30 used to drive the wheels will also change, so the change in the driving motor 30 speed detected by the resolver sensor can be used to perceive and observe the change in the adhesion of the road, and the actual torque actually output by the driving motor 30 to some extent reflects the adhesion capability of the road, so the adhesion capability of the road can be accurately and quickly observed in real time according to the resolver signal and the torque signal.

[0125] In one embodiment, at the second time t2, the driving torque of the two rear wheels of the electric vehicle 10 is controlled to increase to a target value, the target value increases as the speed of the electric vehicle 10 increases, and the target value decreases as the distance between the electric vehicle 10 and the obstacle increases.

[0126] The target value is greater than the adhesion capability of the road, which can be detected according to the resolver signal and the driving motor output torque. Thus, the target value is far beyond the adhesion capability of the road, which leads to excessive slipping and causes danger.

[0127] The faster the electric vehicle 10 travels or the closer the distance between the electric vehicle 10 and the obstacle, the shorter the time for the electric vehicle 10 to hit the obstacle, and the rear wheels of the electric vehicle 10 need to slip faster, so the driving torque of the rear wheels is controlled to increase as the speed increases and to increase as the distance to the obstacle decreases. The slower the electric vehicle 10 travels or the farther the distance between the electric vehicle 10 and the obstacle, the longer the time for the electric vehicle 10 to hit the obstacle, and the rear wheels of the electric vehicle 10 have more margin for slipping, so the driving torque of the rear wheels is controlled to decrease as the speed decreases and to decrease as the distance to the obstacle increases.

[0128] Referring back to Figure 4 and Figure 5 In one embodiment, between the second time t2 and the third time t3, the driving torque of the two rear wheels is controlled to be greater than the driving torque of the two front wheels.

[0129] During the drifting process, the front wheels should maintain the grip. The front wheels are steering wheels, and if the front wheels lose the grip first, it will lead to losing part or almost all of the grip, and the steering effect will be reduced or lost. With the same steering wheel angle, the actual vehicle produces a smaller turning angle than the turning angle when there is grip, resulting in understeering. For the rear wheels, the rear wheels are in the critical stability interval and in the nonlinear interval of the tire friction limit circle, and tend to slide sideways. The control target of the rear wheels is to enable the rear wheels to lose or partially lose the grip, so that the electric vehicle 10 spins out. Therefore, by controlling the driving torque of the rear wheels to be greater than the driving torque of the front wheels, favorable conditions can be provided for drifting, and the drifting process of the electric vehicle 10 can be in a controlled state.

[0130] In an embodiment, the control method further comprises: between the second time t2 and the third time t3, controlling the slip ratio of the two rear wheels to be greater than a preset value.

[0131] The rotational speed of the driving motor can be obtained through the rotational variable signal of the rotational variable sensor, the angular velocity of the wheel can be calculated through the rotational speed of the driving motor and the transmission ratio of the electric vehicle, and the slip ratio of each wheel can be obtained in combination with the wheel radius and the speed of the electric vehicle. The electric vehicle can adjust the driving torque of the rear wheels according to the slip ratio of the rear wheels. For the rear wheels, during the drifting process, it is desirable that the slip ratio of the wheels of the rear axle is in the critical stability interval and in the nonlinear interval of the tire friction limit circle, and tends to slide sideways. 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.

[0132] In an embodiment, between the second time t2 and the third time t3, the driving torque of the rear wheels of the electric vehicle 10 changes with the change of the center of mass side slip angle of the electric vehicle 10.

[0133] The electric vehicle 10 can detect the information of the electric vehicle and the obstacle according to the obtained perception data, and plan a drifting obstacle avoidance path. According to the path and the actual path of the electric vehicle, the target center of mass side slip angle of the electric vehicle 10 during the drifting obstacle avoidance process can be determined. Therefore, the electric vehicle 10 controls the size of the driving torque of the rear wheels according to the actual center of mass side slip angle of the electric vehicle 10. When the center of mass side slip angle is less than the target center of mass side slip angle, the driving torque of the rear wheels is increased. When the center of mass side slip angle is greater than the target center of mass side slip angle, the driving torque of the rear wheels is reduced.

[0134] In an embodiment, between the second time t2 and the third time t3, the driving torque of the rear wheels of the electric vehicle 10 is different from the torque indicated by the opening degree of the accelerator pedal.

[0135] At the second time t2 to the third time t3, the electric vehicle is in the process of drifting to avoid the obstacle, the driving torque of the rear wheels is different from the torque indicated by the opening of the accelerator pedal. The driving torque of the rear wheels does not change with the change of the opening of the brake pedal. At this time, the closed loop of the torque is carried out inside the motor controller 40, which directly determines the driving torque of the rear wheels, which is different from the torque indicated by the opening of the accelerator pedal.

[0136] Continuing to refer to Figure 4 and Figure 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 controlled to decrease.

[0137] At the third time t3, the electric vehicle 10 changes the driving trajectory by drifting, avoids the obstacle and gradually moves away from the obstacle, the distance between the electric vehicle 10 and the obstacle increases to be greater than the second preset distance, at this time the goal of avoiding the obstacle is achieved, the drifting can be stopped, the driving torque of the two rear wheels is controlled to decrease, and the driving torque of the two rear wheels is within the range of the road adhesion limit, and the slipping no longer occurs.

[0138] Continuing to refer to Figure 4 and Figure 5 In an embodiment, at the fourth time t4 after the third time t3, the driving torque of the two rear wheels is controlled to decrease to zero, and the brake system 60 of the electric vehicle 10 is controlled to increase the output braking force.

[0139] At the fourth time t4, after the electric vehicle 10 completes the drifting obstacle avoidance operation, the electric vehicle 10 can be controlled to stop, the driving torque is controlled to decrease to zero, and the brake system 60 outputs the braking force to brake the electric vehicle, so that the electric vehicle 10 stops.

[0140] Further, the steering wheel of the electric vehicle 10 can also be controlled to return to normal.

[0141] It should be understood that after the third time t3, the electric vehicle 10 can also be controlled to continue driving, that is, the driving torque of the two rear wheels is controlled to be equal to the torque indicated by the opening of the accelerator pedal.

[0142] In an embodiment, after the first time t1, in response to the change of the opening of the user-operated accelerator pedal, the opening of the brake pedal or the turning angle of the steering wheel, the rotation of the steering wheel of the electric vehicle 10 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.

[0143] It should be understood that the drift obstacle avoidance is mainly the control in the intelligent driving or automatic driving scenario of the electric vehicle 10. When the user intervenes in the operation in the process, the human driving signal should be given priority. When it is detected that the driver actively operates, for example, turns the steering wheel, steps on the accelerator pedal or the brake pedal, the electric vehicle 10 judges that the driver intervenes, stops the automatic drift obstacle avoidance, and controls in response to the operation of the driver.

[0144] According to the scheme of the present application, when the distance from the obstacle is close, the steering is controlled and the rear wheel torque output is adjusted so that the rear wheel breaks through the critical adhesion limit, and the electric vehicle is automatically controlled to drift in cooperation with multiple systems to avoid collision with the obstacle, improve the stability of the obstacle avoidance operation, respond accurately and quickly, and effectively improve the safety of the vehicle.

[0145] The control architecture of the vehicle controller and the control process of the drift obstacle avoidance provided in the embodiments of the present application will be described below. Figure 6 and Figure 7 The control architecture of the vehicle controller and the control process of the drift obstacle avoidance provided in the embodiments of the present application will be described below.

[0146] It should be understood that the vehicle controller provided in the present application can be the whole vehicle controller 20, the motor controller 40, the intelligent driving controller 70, or other separately arranged controllers with control capability.

[0147] In an embodiment, the vehicle controller can be carried in a separate power domain controller, or can be carried in the motor controller 40. If it is carried in the motor controller 40, the drift obstacle avoidance trajectory information planned by the intelligent driving controller and the chassis CAN information need to be transmitted to the motor controller 40 side, and the motor controller 40 is directly connected to the steering system and other components. The motor controller 40 directly monitors the change of the road adhesion capacity in real time according to the rotary variable signal of the driving motor 30 side, so that the torque control time delay can be reduced by at least 20 ms. The motor controller sends the brake signal to the brake system 60 and the steering signal to the steering system. Thus, the driving system, the brake system 60 and the steering system cooperate to realize controlled drift.

[0148] In an embodiment, the vehicle controller can also be carried in the whole vehicle controller 20. The motor controller sends the rotary variable signal or the detected change of the road adhesion capacity to the whole vehicle controller 20 through CAN communication. The whole vehicle controller 20 controls the drift obstacle avoidance in combination with the distance from the obstacle obtained by the perception system and the drift obstacle avoidance trajectory information planned by the intelligent driving controller, sends the torque signal to the motor controller 40, sends the brake signal to the brake system 60, and sends the steering signal to the steering system. Thus, the driving system, the brake system 60 and the steering system cooperate to realize controlled drift.

[0149] 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.

[0150] like Figure 6 As shown, 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 trajectory. The vehicle controller performs drift obstacle avoidance control based on the actual trajectory 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 trajectory (including parameters such as target center of gravity sideslip angle, target yaw rate, and target vehicle speed).

[0151] The vehicle controller observes the actual vehicle's sideslip angle and trajectory 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.

[0152] 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.

[0153] In one embodiment, the vehicle controller can establish a vehicle dynamics model according to the following formula:

[0154]

[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 trajectory, and Δφ be the heading angle error. This can be expressed in state-space form:

[0156]

[0157] Where, x(t)=[ω β V e] T u(t)=[δ F xr ] T .

[0158] In an embodiment, the vehicle controller takes x(t) as the control target and u(t) as the control variable to perform trajectory control on the electric vehicle 10. Unlike other trajectory tracking and control, the important control target of drift obstacle avoidance is the large mass center side slip angle, so the weight of the mass center side slip angle will be larger.

[0159] In addition, the longitudinal control variable based on the above vehicle dynamics model is F xr , which needs to be converted into the rear wheel drive torque to indicate the motor controller 40 to drive the motor torque control:

[0160] T r = F xr × r / RR.

[0161] Where r is the tire radius and RR is the reduction ratio.

[0162] The vehicle controller breaks through the critical road adhesion limit control Tr> road adhesion limit by controlling the rear wheel drive torque, so as to realize drift.

[0163] The vehicle controller accurately judges the slip rate using the resolver signal of the drive motor 30 and performs millisecond-level closed loop, and accurately identifies the adhesion ability of the electric drive corresponding wheel / axle to the contact road surface during slip.

[0164] In combination with Figure 4 , Figure 5 and Figure 6 , in an embodiment, the steering wheel of the electric vehicle 10 is controlled during the driving process when the speed of the electric vehicle 10 is greater than the preset speed, and the distance between the electric vehicle 10 and the obstacle is less than the preset distance at the first time t1. The drive torque of the two rear wheels of the electric vehicle 10 is increased at the second time t2 after the first time t1.

[0165] As Figure 4 and Figure 5As shown, in an embodiment, the perception system of the electric vehicle 10 is used to detect the driving trajectory of the electric vehicle 10 and the distance between the electric vehicle 10 and the obstacle. At a first time t1, the perception 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, the vehicle controller sends a steering angle instruction to the steering system in response to the distance signal, the steering system controls the steering wheel of the electric vehicle to turn in response to the steering angle instruction, so that the electric vehicle generates a side slip angle and a lateral force. At a second time after the first time t1, the distance between the electric vehicle 10 and the obstacle is further reduced, the vehicle controller sends a torque instruction to the drive system, the drive system controls the drive torque of the two rear wheels of the electric vehicle to increase in response to the torque instruction, the road adhesion is broken through, the rear wheels start to slip, the lateral force received by the electric vehicle is greater than the lateral friction limit of the tire, so that the electric vehicle slips, the wheels travel along the circumferential tangent direction of the vehicle body, and the electric vehicle drifts, so that the electric vehicle 10 avoids the obstacle. It should be understood that the second time t2 can be very close to the first time t1, and the electric vehicle 10 can adjust the drive torque increase of the rear wheels after the steering wheel is turned, or can start to adjust the drive torque increase of the rear wheels during the steering wheel is turned. In this application, the drive torque of the wheel can be understood as the torque output by the drive motor for driving the wheel. The road adhesion coefficient is the friction between the wheel and the road, and the size of the road adhesion coefficient has an important influence on the safety and stability of the vehicle. The road adhesion coefficient is affected by many factors, including road material, humidity, temperature, tire type and wear degree, etc. Under different road conditions and weather conditions, the corresponding road adhesion coefficient may be different. When the adhesion of the wheel on the road changes, the speed and torque of the drive motor for driving the wheel will also change, so the change of the drive motor speed detected by the resolver sensor can be used to perceive and observe the change of the road adhesion, and the actual torque output by the drive motor reflects the adhesion capacity of the road to a certain extent, so that the road adhesion capacity can be observed in real time, accurately and quickly according to the resolver signal and the torque signal. According to the scheme of the present application, the road adhesion capacity is observed in real time, the drive torque of the rear wheels is adjusted to make the rear wheels break through the critical adhesion limit, the rear wheels are actively controlled to slip, and the favorable conditions for drifting are created, so that the drifting obstacle avoidance process is reliably controlled, and the safety of the vehicle is improved.

[0166] As shown in the figure, Figure 7 The control flow of drift obstacle avoidance is as follows:

[0167] First, the vehicle controller inputs signals, including vehicle driving trajectory, target trajectory, wheel speed, drive motor torque, drive motor speed, drift obstacle avoidance enable signal, etc.

[0168] The actual executed torque is fed back by the motor controller according to the vehicle wheel speed, the motor speed, the torque signal, and the current road adhesion capacity of the corresponding wheel / axle.

[0169] Then, when it is detected that the distance between the electric vehicle 10 and the obstacle is less than the preset distance, the vehicle controller judges whether the vehicle speed is greater than the preset vehicle speed and less than the vehicle speed limit value. If the vehicle speed is within the drift obstacle avoidance applicable range, drift obstacle avoidance control is performed.

[0170] The specific drift obstacle avoidance control method can be referred to the foregoing description.

[0171] Next, the target mass center side slip angle, target yaw angle, etc. are calculated according to the drift obstacle avoidance trajectory.

[0172] The driving motor torque and the steering angle are calculated by the vehicle controller according to the road adhesion capacity, and are respectively sent to the motor controller 40 and the steering system.

[0173] Finally, the driving motor is controlled by the motor controller to output the calculated driving torque, and the steering system controls the electric vehicle 10 to steer at the calculated steering angle to complete the drift obstacle avoidance.

[0174] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A control method for drift obstacle avoidance of an electric vehicle, characterized by, The control method is used for controlling a steering system and a driving system of the electric vehicle to make the electric vehicle avoid the detected obstacle during a driving process in which a vehicle speed of the electric vehicle is greater than a preset vehicle speed, and the control method comprises: controlling a steering wheel of the electric vehicle to rotate at a first time after a distance between the electric vehicle and the obstacle is less than a preset distance, and controlling a steering wheel rotation angle of the electric vehicle to increase with an increase of the vehicle speed of the electric vehicle and to decrease with an increase of the distance between the electric vehicle and the obstacle; controlling driving torques of two rear wheels of the electric vehicle to increase to make the two rear wheels break through a road surface adhesion limit at a second time after the first time, so that the electric vehicle is caused to perform a side slip.

2. The control method according to claim 1, characterized by, The control method further comprises: controlling the driving torques of the two rear wheels to decrease at a third time after the second time, when the distance between the electric vehicle and the obstacle is greater than a second preset distance.

3. The control method according to claim 2, characterized by, The control method further comprises: controlling the driving torques of the two rear wheels to decrease to zero and controlling a braking system of the electric vehicle to increase an output braking force at a fourth time after the third time.

4. The control method according to claim 2, characterized by, The control method specifically comprises: controlling the driving torques of the two rear wheels to be greater than driving torques of two front wheels between the second time and the third time.

5. The control method according to any one of claims 1 to 4, characterized by, The control method further comprises: controlling a driving motor of the electric vehicle to output a reverse torque in a direction opposite to a rotation direction of the driving motor when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than a third preset distance before the first time, and controlling the driving motor to stop outputting the reverse torque at the first time.

6. The control method according to any one of claims 1 to 4, characterized by, The control method further comprises: controlling a braking system of the electric vehicle to output a braking force to four wheels of the electric vehicle when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than a third preset distance before the first time, and controlling the braking force output by the braking system to decrease to zero at the first time.

7. The control method according to claim 2, characterized by, The control method further comprises: controlling a slip ratio of the two rear wheels to be greater than a preset value between the second time and the third time.

8. The control method according to any one of claims 1 to 4, characterized by, The control method specifically comprises: controlling the driving torques of the two rear wheels of the electric vehicle to increase to target values at the second time, the target values increasing with an increase of the vehicle speed of the electric vehicle and decreasing with an increase of the distance between the electric vehicle and the obstacle.

9. The control method according to claim 2, characterized by, The control method specifically comprises: controlling the driving torques of the rear wheels of the electric vehicle to change with a change of a center of mass side slip angle of the electric vehicle between the second time and the third time.

10. The control method according to claim 2, characterized by, The control method further comprises: controlling the driving torques of the rear wheels of the electric vehicle to be different from a torque indicated by an opening degree of an accelerator pedal between the second time and the third time.

11. The control method according to any one of claims 1 to 4, characterized by, The control method further comprises: After the first time, in response to a change in an opening degree of an accelerator pedal, an opening degree of a brake pedal, or a steering angle of a steering wheel of the user operation, the steering wheel of the electric vehicle is stopped from rotating and the driving torque of the two rear wheels is controlled to be equal to a torque indicated by the opening degree of the accelerator pedal.

12. The control method according to any one of claims 1 to 4, characterized by, The control method further comprises: Before the first time, the user controls the electric vehicle to start an automatic obstacle avoidance mode by touching a central control screen of the electric vehicle or activating an automatic obstacle avoidance button, the automatic obstacle avoidance mode being used to control a steering system and a driving system of the electric vehicle to make the electric vehicle avoid obstacles during a driving process of the electric vehicle at a speed greater than a preset vehicle speed.

13. A vehicle controller characterized by comprising: The vehicle controller is used to implement the control method according to any one of claims 1-12.

14. An electric vehicle characterized by comprising: The electric vehicle comprises the vehicle controller, the steering system, and the driving system according to claim 13; wherein: The driving system comprises a motor controller and a driving motor, the motor controller being used to control the driving motor to output a driving torque to the two rear wheels of the electric vehicle; The steering system is used to control a steering angle of the two front wheels of the electric vehicle.

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