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

Abstract

The invention discloses a control method for drifting and obstacle avoidance of an electric vehicle, a vehicle controller and the electric vehicle, 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 in the running process that the vehicle speed of the electric vehicle is larger than the preset vehicle speed so that the electric vehicle can avoid a detected obstacle, and the control method comprises the steps that at the first moment after the distance between the electric vehicle and the obstacle is smaller than the preset distance, and controlling a steering wheel of the electric vehicle to rotate. And controlling the driving torque of the two rear wheels of the electric vehicle to be increased at a second time after the first time. 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 specifically, to a control method for electric vehicle drift obstacle avoidance, a vehicle controller and an electric vehicle. Background Art

[0002] During the driving process of an electric vehicle, if there is an obstacle on the driving path of the electric vehicle, at this time. If the distance between the electric vehicle and the obstacle is too close, it is not enough to achieve emergency braking. It is not the best way to avoid collision or reduce collision losses by braking. At this time, you can control the steering wheel and throttle to take drifting actions to avoid vehicle collision. However, drifting usually requires the driver to master driving skills and has certain requirements for the timing of operation. In extreme scenarios where the distance between the electric vehicle and the obstacle is too close, it is difficult to require the driver to drift to achieve effective obstacle avoidance. Therefore, how to effectively control the vehicle to drift and avoid obstacles is a problem that needs to be solved. Summary of the invention

[0003] The present application provides a control method for electric vehicle drift obstacle avoidance, a vehicle controller and an electric vehicle. When the distance to an obstacle is close, the steering is controlled and the rear wheel torque output is adjusted so that the rear wheels break through the critical adhesion limit, and the electric vehicle is automatically controlled to drift in a controlled manner to avoid collision with the obstacle, thereby improving the stability of the obstacle avoidance operation, responding accurately and quickly, and effectively improving the safety of the vehicle.

[0004] In a first aspect, the present application provides a control method for electric vehicle drift obstacle avoidance, which is used to control the steering system and drive system of the electric vehicle when the speed of the electric vehicle is greater than a preset speed so that the electric vehicle avoids a detected obstacle. The control method includes: at a first moment after the distance between the electric vehicle and the obstacle is less than a preset distance, controlling the steering wheel of the electric vehicle to rotate. At a second moment after the first moment, controlling the driving torque of the two rear wheels of the electric vehicle to increase.

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

[0006] Drifting is a special driving skill for a vehicle. By making the rear wheels of the vehicle lose friction and grip with the road surface or greatly reduce friction and grip with the road surface when turning, the vehicle will oversteer, the rear will be thrown outward, and the vehicle will slide through the corner. This process requires the driver to have a high degree of skill and sensitive control of the vehicle dynamics through the coordinated operation of the steering wheel, accelerator and brake, which is demanding. One way to drift is to drift by driving the tire to reduce or eliminate the lateral adhesion. In the obstacle avoidance scenario, it is difficult for the driver to operate the steering wheel and drive system to accurately complete the drift. The control method for electric vehicle drift obstacle avoidance provided in this application can be used for automatic control of the electric vehicle, that is, to complete the drift obstacle avoidance operation without the intervention of the driver, or to assist the driver in drifting obstacle avoidance, that is, the driver only needs a small amount of operation to complete the drift obstacle avoidance operation.

[0007] The electric vehicle can detect the environment around the electric vehicle and the running status information of the electric vehicle through the perception system. The perception system may include sensors such as cameras, laser radars, millimeter-wave radars, etc. for sensing the surrounding environment, and collecting and processing environmental information and in-vehicle information, mainly 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 for detecting the vehicle body status and driving information of the electric vehicle. The perception data signal may include information such as relative distance, relative vehicle speed, relative acceleration, and lane information. The perception signal may also include information such as the speed, acceleration, roll angle, and yaw angle of the electric vehicle. The electric vehicle can detect the information of the electric vehicle and obstacles based on the acquired 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 sensors such as cameras and radars, and determine whether to perform drift obstacle avoidance control based on the vehicle speed and the distance to the obstacle.

[0008] During the driving process of the electric vehicle at a speed greater than the preset speed, when it is detected that the distance between the electric vehicle and the obstacle is less than the preset distance, the drift 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 a more serious collision may occur when emergency braking starts from the preset speed, so the electric vehicle's drift obstacle avoidance control method is used to control the electric vehicle to drift to avoid the obstacle. The preset speed and preset distance can be pre-calibrated according to actual vehicle experiments and / or model calculations, or can be pre-set by comprehensively considering the vehicle requirements and vehicle performance.

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

[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 increases, breaking through the adhesion of the road surface, and the rear wheels begin to slip. The lateral force exerted on the electric vehicle is greater than the lateral friction limit of the tires, causing the electric vehicle to skid, and the wheels move along the tangent direction of the body's circumference, causing the electric vehicle to drift.

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

[0013] In the present application, the driving torque of a wheel may be understood as the torque output by a driving motor for driving the wheel.

[0014] The road adhesion coefficient is the friction between the wheels and the road. The road adhesion coefficient has an important impact on the safety and stability of vehicle driving. The road adhesion coefficient is affected by many factors, including road material, humidity, temperature, tire type and degree of wear. 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 used to drive the wheel will also change. Therefore, the change in the speed of the drive motor detected by the resolver sensor can be used to perceive and observe the change in road adhesion. The actual torque actually output by the drive motor reflects the adhesion ability of the road to a certain extent, so that the road adhesion ability can be accurately and quickly observed in real time based on the resolver signal and torque signal.

[0015] According to the solution of the present application, the road adhesion ability is observed in real time, the rear wheel drive torque is adjusted to make the rear wheels break through the critical adhesion limit, and the rear wheels are actively controlled to slip, creating favorable conditions for the vehicle to drift, so that the drifting and obstacle avoidance process is reliably controlled, thereby improving the safety of the vehicle.

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

[0017] At the third moment, the electric vehicle changes its driving trajectory through 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 goal is achieved, and the drift can be stopped, and the driving torque of the two rear wheels can be controlled to decrease so that the driving torque of the two rear wheels is within the road adhesion limit and no more slipping occurs. The second preset distance can be pre-calibrated according to actual vehicle experiments and / or model calculations, or can be pre-set by comprehensively considering the vehicle requirements 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 the obstacle avoidance according to the actual driving track of the electric vehicle. When the obstacle is no longer on the actual driving track of the electric vehicle, it can also be considered that the obstacle avoidance is completed.

[0019] According to the solution of the present application, after the electric vehicle avoids an obstacle by drifting, the rear wheel drive torque is controlled to decrease, so that the rear wheels stop slipping and obtain sufficient grip, the electric vehicle leaves the drifting state, and the electric vehicle is prevented from continuing to drift and causing other collisions, thereby improving the safety and controllability of the electric vehicle.

[0020] In combination with the first aspect, in certain implementations of the first aspect, at a fourth moment after the third moment, the driving torque of the two rear wheels is controlled to be reduced to zero, and the braking system of the electric vehicle is controlled to increase the output braking force.

[0021] At the fourth moment, after the electric vehicle completes the drift obstacle avoidance operation, the electric vehicle can be controlled to stop, the driving torque is controlled to be reduced to zero and the braking system is controlled to output braking force to brake the electric vehicle and stop the electric vehicle. Furthermore, the steering wheel of the electric vehicle can be controlled to return to the normal position.

[0022] It should be understood that after the third moment, the electric vehicle can also be controlled to continue running, 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 solution of the present application, after the electric vehicle completes drifting and obstacle avoidance, the electric vehicle is controlled to stop to avoid the danger of continuing to drive, thereby improving the safety and controllability of the electric vehicle.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the control method specifically includes: between the second moment and the third moment, controlling the driving torque of the two rear wheels to be greater than the driving torque of the two front wheels.

[0025] During drifting, the front wheels should maintain grip. The front wheels are steering wheels. If the front wheels lose grip first, it will lead to the loss of some or almost all grip, and the steering effect will be reduced or lost. Under the same steering wheel angle, the actual vehicle rotation angle is smaller than the rotation angle when there is grip, resulting in understeering. For the rear wheels, the rear wheels are in the critical stability range and the nonlinear range of the friction limit circle of the tires, and tend to skid. The control goal of the rear wheels is to make the rear wheels lose or partially lose grip, causing the electric vehicle to drift. 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 can be kept under control.

[0026] According to the solution 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, so that the drifting obstacle avoidance is controlled, thereby improving the safety and stability of the vehicle.

[0027] In combination with the first aspect, in certain implementations of the first aspect, the control method also includes: before the first moment, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, controlling the drive motor of the electric vehicle to output a reverse torque and controlling the drive motor to stop outputting the reverse torque at the first moment, and the direction of the reverse torque is opposite to the direction of the rotation speed of the drive motor.

[0028] Reverse torque can also be understood as a negative driving torque. The drive motor includes a stator winding and a rotor. By outputting alternating current to the three-phase stator winding, the output torque of the drive motor can be controlled. By adjusting the magnitude of the stator winding current and the phase of the three-phase current through the motor controller, the stator magnetic field strength and direction can be changed, thereby changing the interaction force between the stator and the rotor, that is, the driving motor torque. By changing the phase of the three-phase current output to the drive motor, the rotor cuts the magnetic field generated by the stator winding, and the kinetic energy of the rotor is converted into electrical energy and input into the power battery. At this time, the drive motor outputs negative torque. By changing the magnitude of the three-phase current output to the drive motor by the motor controller, the driving torque or reverse torque output by the motor can be increased or decreased.

[0029] When the driving torque of a wheel is negative, the driving motor that drives the wheel outputs a reverse torque, the direction of which is opposite to the rotational speed of the driving motor, and the reverse torque is used to brake the wheel.

[0030] The third preset distance may be the distance at which the electric vehicle starts braking. The third preset distance may be pre-calibrated based on actual vehicle experiments and / or model calculations, or may be pre-set based on comprehensive consideration of vehicle requirements and vehicle performance.

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

[0032] According to the solution of the present application, braking is performed before drifting to transfer the rear axle load, providing favorable conditions for the electric vehicle to drift. The driving motor is used to output reverse torque for braking, which has a quick response and improves the controllability and stability of the electric vehicle.

[0033] In combination with the first aspect, in certain implementations of the first aspect, the control method also includes: before the first moment, when the distance between the electric vehicle and the obstacle is greater than the preset distance and less than the third preset distance, 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 be reduced to zero at the first moment.

[0034] Before the drift starts, i.e. the first moment, the steering wheel has not been turned and the electric vehicle is still moving straight. At this time, the braking system can also output braking force to the wheels to brake, shift the center of gravity of the electric vehicle, and reduce the axle load on the rear axle of the electric vehicle, which is conducive to the rear axle wheels breaking through the adhesion of the road surface, thereby providing favorable conditions for the electric vehicle to drift. At the first moment, the braking system is controlled to stop outputting braking force to prevent the braking force from affecting the body balance of the electric vehicle during the drift process.

[0035] Controlling the braking force output by the braking system and controlling the reverse torque output by the drive motor can also be used in coordination. Within the capacity of the drive system, the reverse torque output by the drive motor is used for braking first. When the drive system capacity is insufficient, the braking force of the braking system is used as a supplement, with accurate and rapid response.

[0036] According to the solution of the present application, driving and braking are coordinated and controlled, the response is precise and rapid, braking is performed before drifting, and the rear axle load is transferred, which provides favorable conditions for the drift of the electric vehicle and improves the controllability and stability of the electric vehicle.

[0037] In combination with the first aspect, in certain implementations of the first aspect, the control method further includes: between the second moment and the third moment, controlling the slip rate of the two rear wheels to be greater than a preset value.

[0038] The rotation speed of the drive motor can be obtained through the rotation signal of the rotation sensor, the angular velocity of the wheel can be calculated through the rotation speed of the drive motor and the transmission ratio of the electric vehicle, and the slip rate of each wheel can be obtained by combining the wheel radius and the speed of the electric vehicle. In the present application, the slip rate can be a slip rate or a sliding rate. The electric vehicle can adjust the driving torque of the rear wheel according to the slip rate of the rear wheel. For the rear wheel, during the drift process, it is hoped that the slip rate of the wheel on the rear axle is in the critical stability range, in the nonlinear range of the friction limit circle of the tire, and tends to side slip. By controlling the slip rate of the two rear wheels to be greater than the preset value, the electric vehicle can be placed in a drifting state.

[0039] According to the solution of the present application, the rear wheel drive torque is changed according to the wheel slip rate, so that the rear wheel slip rate is greater than a preset value, thereby accurately controlling the electric vehicle to be in a drift state, responding quickly, and improving the controllability and stability of the electric vehicle.

[0040] In combination with the first aspect, in certain implementations of the first aspect, the control method specifically includes: at a first moment, controlling the steering wheel angle of the electric vehicle to increase as the speed of the electric vehicle increases, and controlling the steering wheel angle of the electric vehicle to decrease as the distance between the electric vehicle and the obstacle increases.

[0041] The faster the electric vehicle is going or the closer the electric vehicle is to the obstacle, the shorter the time it takes for the electric vehicle to hit the obstacle, and the larger the angle required for drifting to avoid the obstacle. Therefore, the steering angle of the control wheel increases with the increase of the vehicle speed and increases with the decrease of the distance from the obstacle. The slower the electric vehicle is going or the farther the electric vehicle is from the obstacle, the longer the time it takes for the electric vehicle to hit the obstacle, and the larger the margin required for drifting to avoid the obstacle. Therefore, the steering angle of the control wheel decreases with the decrease of the vehicle speed and decreases with the increase of the distance from the obstacle.

[0042] According to the solution of the present application, the steering wheel rotation angle 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.

[0043] In combination with the first aspect, in certain implementations of the first aspect, the control method specifically includes: at the second moment, controlling the driving torque of the two rear wheels of the electric vehicle to increase to a target value, the target value increases as the speed of the electric vehicle increases, and the target value decreases as the distance between the electric vehicle and the obstacle increases.

[0044] The target value is greater than the road adhesion capacity, which can be detected based on the resolver signal and the output torque of the drive motor, so as to avoid excessive slippage and danger caused by the target value far exceeding the road adhesion capacity.

[0045] The faster the electric vehicle speed is or the closer the electric vehicle is to the obstacle, the shorter the time it takes for the electric vehicle to hit the obstacle, and the rear wheels of the electric vehicle need to slip faster. Therefore, the driving torque for controlling the rear wheels increases with the increase of the vehicle speed and increases with the decrease of the distance from the obstacle. The slower the electric vehicle speed is or the farther the electric vehicle is from the obstacle, the longer the time it takes for the electric vehicle to hit the obstacle, and the margin of the rear wheels of the electric vehicle to slip is larger. Therefore, the driving torque for controlling the rear wheels decreases with the decrease of the vehicle speed and decreases with the increase of the distance from the obstacle.

[0046] According to the solution of the present application, the increase value of the rear wheel drive torque when the electric vehicle drifts 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 certain implementations of the first aspect, the control method specifically includes: between the second moment and the third moment, controlling the driving torque of the rear wheels of the electric vehicle to change with the change of the sideslip angle of the center of mass of the electric vehicle.

[0048] The electric vehicle can detect the information of the electric vehicle and the obstacle based on the acquired perception data, and plan a drifting obstacle avoidance path. The target center of mass sideslip angle of the electric vehicle during the drifting obstacle avoidance process can be determined based on the path and the actual path of the electric vehicle. Thus, the electric vehicle controls the magnitude of the rear wheel drive torque based on the actual center of mass sideslip angle of the electric vehicle. When the center of mass sideslip angle is less than the target center of mass sideslip angle, the rear wheel drive torque is increased, and when the center of mass sideslip angle is greater than the target center of mass sideslip angle, the rear wheel drive torque is reduced.

[0049] According to the solution of the present application, the center of mass sideslip angle is used as the control parameter in the process of drifting and avoiding obstacles of the electric vehicle. The path of the electric vehicle drifting and avoiding obstacles can be accurately controlled, the center of mass sideslip angle can be effectively controlled, the handling stability can be improved, and the uncontrollable danger of the electric vehicle during drifting and avoiding obstacles can be avoided, thereby improving the controllability and safety of the electric vehicle.

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

[0051] The accelerator pedal in this application may also be referred to as an accelerator pedal or an acceleration pedal. The opening of the accelerator pedal can indicate the size of the driving force required by the driver. The larger the opening of the accelerator pedal, the greater the driver's demand for driving, and the corresponding torque required to be output by the drive motor is also greater. When drift obstacle avoidance control is not performed, the torque indicated by the opening of the accelerator pedal can be controlled according to the opening of the accelerator pedal. The larger the opening of the accelerator pedal, the greater the torque output by the drive motor, and the smaller the opening of the accelerator pedal, the smaller the torque output by the drive motor. The driving torque of the rear wheels changes with the change of the opening of the accelerator pedal.

[0052] Between the second moment and the third moment, the electric vehicle is in the process of drifting and avoiding obstacles, and the rear wheel driving torque is different from the torque indicated by the opening of the accelerator pedal. The rear wheel driving torque does not change with the change of the opening of the brake pedal. At this time, the torque closed loop inside the motor controller directly determines the rear wheel driving torque, which is different from the torque indicated by the opening of the accelerator pedal.

[0053] According to the solution of the present application, the driving torque of the closed-loop rear wheels in the driving system during drift obstacle avoidance is determined instead of being determined according to the opening 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 certain implementations of the first aspect, the control method also includes: after the first moment, in response to changes in the opening of the accelerator pedal, the opening of the brake pedal, or the steering wheel angle operated by the user, stopping controlling the steering wheel rotation of the electric vehicle and controlling the driving torque of the two rear wheels to be equal to the torque indicated by the opening of the accelerator pedal.

[0055] It should be understood that drifting and obstacle avoidance are mainly controlled in the scenarios of intelligent driving or automatic driving of electric vehicles. When the user intervenes in the operation during this process, the human driving signal should be given priority. When it is detected that the driver has taken active actions, such as turning the steering wheel, stepping on the accelerator pedal or stepping on the brake pedal, the electric vehicle will determine that the driver has intervened, stop automatic drifting and obstacle avoidance, and respond to the driver's operation for control.

[0056] According to the solution of the present application, during the drifting obstacle avoidance process, the driver's operation is given priority. When the driver intervenes, the drifting obstacle avoidance is stopped, which improves the flexibility of handling emergency situations and improves the safety and reliability of the electric vehicle.

[0057] In combination with the first aspect, in certain implementations of the first aspect, the control method also includes: before the first moment, the user controls the electric vehicle to start the automatic obstacle avoidance mode by touching the central control screen of the electric vehicle or activating the automatic obstacle avoidance button. The automatic obstacle avoidance mode is used to control the steering system and drive system of the electric vehicle when the electric vehicle is traveling at a speed greater than a preset speed so that the electric vehicle can avoid obstacles.

[0058] Drift obstacle avoidance can be used as an optional operating mode for electric vehicles. Drift obstacle avoidance control will only be performed when a collision is about to occur if the user has previously activated the automatic obstacle avoidance mode.

[0059] An automatic obstacle avoidance button may be provided on the electric vehicle for the driver to operate. Exemplarily, the automatic obstacle avoidance button may be a physical button, and the driver may press the physical button to start the automatic obstacle avoidance mode of the electric vehicle, thereby starting the drift obstacle avoidance control when the distance between the electric vehicle and the obstacle is less than the preset distance when the speed of the electric vehicle is greater than the preset speed. Exemplarily, the automatic obstacle avoidance button may be a virtual button on the central control screen, and the driver may start the automatic obstacle avoidance mode of the electric vehicle by selecting the automatic obstacle avoidance mode. Exemplarily, the automatic obstacle avoidance button may also be provided indirectly, for example, by being combined with the button of the intelligent driving mode or by default starting the automatic obstacle avoidance mode of the electric vehicle when the driver turns off other buttons.

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

[0061] In a second aspect, the present application provides a vehicle controller for executing the control method as described in the first aspect and its various implementations.

[0062] The vehicle controller in this application can be a motor controller of an electric vehicle, or a whole vehicle controller, or an intelligent driving controller, or a separately set controller with control capabilities. The vehicle controller is suitable for electric vehicles or hybrid vehicles. The electric vehicle can be a distributed motor or a centralized motor architecture, with multiple drive motors and multiple motor controllers. The vehicle controller can be any one of the multiple motor controllers.

[0063] The intelligent driving controller in this application can be a domain controller for realizing 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 in driving. The intelligent driving controller receives the perception data signals sent by the electric vehicle perception components such as radar, camera and other sensors. The intelligent driving controller fuses the information perceived by various sensors and obtains the driving status and lane information of the electric vehicle according to the perception data signals. By parsing the distance, speed, acceleration and other signals, the target acceleration and target speed are obtained, and driving decisions / planning are made based on the fused information, and the operation command is issued to the vehicle controller. The vehicle controller sends the intelligent driving torque signal to the motor controller, thereby outputting the torque value indicated by the intelligent driving torque signal to complete the intelligent driving.

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

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

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

[0067] Figure 2 is a schematic diagram of an electric vehicle provided in an embodiment of the present application;

[0068] Figure 3 is a schematic diagram of the architecture of an electric vehicle provided in an embodiment of the present application;

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

[0070] Figure 5 This is a schematic diagram of electric vehicle drifting and obstacle avoidance provided by an embodiment of the present application;

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

[0072] Figure 7 It is a flow chart of the drift obstacle avoidance control of the vehicle controller provided in the embodiment of the present application. DETAILED DESCRIPTION

[0073] The following will describe the technical solution in the present application in conjunction with the accompanying drawings. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, 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 oversteering to make the vehicle drive sideways through a curve. Vehicle drifting is the interaction between the tires and the road surface, which generates lateral and longitudinal forces on the tires. When the rear-drive lateral force breaks through the adhesion of the road surface, the tires generate lateral speed, skid, and the wheels drive along the tangent direction of the body's circumference, which is called drifting. 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 turning in narrow areas. However, drifting by the driver requires the driver to master driving skills, which is difficult for ordinary drivers to achieve. The principle of drifting is to make the rear wheels of the vehicle lose most or all of their grip, while the front wheels must be able to maintain grip. At this time, as long as the front wheels have a certain lateral force, the vehicle will swing and drift.

[0075] like Figure 1 As shown in the figure, when driving at an intersection, especially an intersection without traffic lights, a T-type collision scenario may occur in both directions, where one car hits the side of another car. If the distance between the two cars is too close to achieve emergency braking, a collision may occur. Due to the lack of energy absorption devices in the side structure of the car, T-type collisions cause greater casualties and losses in traffic accidents compared to other collision modes.

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

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

[0078] Based on the above problems, the present application provides a control method for electric vehicle drift obstacle avoidance, a vehicle controller and an electric vehicle. When the distance to an obstacle is close, the electric vehicle is controlled to steer and the rear wheel torque output is adjusted so that the rear wheels break through the critical adhesion limit, and the electric vehicle is automatically controlled to drift in a controlled manner to avoid collision with the obstacle, thereby improving the stability of the obstacle avoidance operation, responding accurately and quickly, and effectively improving the safety of the vehicle.

[0079] Figure 2 and Figure 3 It is a schematic diagram of the architecture of the electric vehicle 10 provided in an embodiment of the present application.

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

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

[0082] It is understandable that the electric vehicle 10 in the embodiment 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 transport device for carrying people or goods such as a tricycle or a two-wheeled vehicle, or other types of vehicles driven by power batteries, which are not limited in the embodiment of the present application. Among them, the vehicle includes but is not limited to a pure electric vehicle (pure electric vehicle / battery electric vehicle, pure EV / batteryEV), a hybrid electric vehicle (hybrid electric vehicle, HEV), a range extended electric vehicle (range extended electric vehicle, REEV), a plug-in hybrid electric vehicle (plug-in hybrid electric vehicle, PHEV), etc.

[0083] The power battery in the embodiment 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., which is not limited in the present application. The power battery can also power other electrical devices in the vehicle, such as the air conditioner in the vehicle, the car player, etc.

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

[0085] In one embodiment, if Figure 3 As shown in (a) of FIG. 1 , the electric vehicle 10 may be a distributed four-drive motor drive architecture, where the drive motors are arranged on the sides of the driven wheels and controlled by separate motor controllers. The electric vehicle 10 may also be a Figure 3 The centralized four-drive motor drive architecture shown in (b) is configured such that two drive motors for driving two front wheels or two rear wheels are arranged together.

[0086] Exemplarily, the electric vehicle 10 includes four motor controllers, including a motor controller 41, a motor controller 42, a motor controller 43, and a motor controller 44. The four motors include a drive motor 31, a drive motor 31, a drive motor 33, and a drive motor 34. The motor controller 41 controls the drive motor 31 to drive the wheel 51, the motor controller 42 controls the drive motor 32 to drive the wheel 52, the motor controller 43 controls the drive motor 33 to drive the wheel 53, and the motor controller 44 controls the drive motor 34 to drive the wheel 54.

[0087] In one embodiment, the electric vehicle 10 may also be 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 uses two drive motors to drive the two rear wheels of the electric vehicle 10 respectively.

[0088] In one embodiment, the various architectures mentioned above may 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 the present application may be any motor controller among a plurality of motor controllers.

[0090] The electric vehicle 10 further 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 angle of the steering wheel 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 brake system 60 includes a brake controller and a plurality of wheel-end brake devices, and the brake controller is connected to the brake pedal signal. The brake controller can be used to determine the braking force according to the opening of the brake pedal. During the driving process, when the electric vehicle 10 needs to brake, the driver steps on the brake pedal, the brake controller receives the brake pedal signal from the brake pedal and outputs a braking force distribution signal to the wheel-end brake device, and the wheel-end brake device is used to receive the braking force distribution signal and output a clamping force to the brake disc according to the instruction of the braking force distribution signal, thereby generating a friction braking force, so that the electric vehicle 10 is braked.

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

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

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

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

[0096] In one embodiment, each motor controller 40 uses a resolver sensor through a signal interface, and the resolver sensor is used to detect the 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 resolver sensor. The motor controller 40 can also generate a speed signal according to the signal from the resolver sensor and send the speed signal to the other three motor controllers 40. Similarly, each motor controller 40 will also receive the 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 rotation speed of the drive motor. It has a high sampling rate and is directly connected to the motor controller 40, with short signal transmission time and higher stability.

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

[0099] In one embodiment, the motor controller 40 can be connected to 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 interact with signals.

[0100] In one embodiment, the electric vehicle 10 includes an automatic obstacle avoidance button. The automatic obstacle avoidance button is used to turn on the automatic obstacle avoidance mode, which is used to control the steering system and drive system of the electric vehicle 10 to avoid obstacles when the electric vehicle 10 is traveling at a speed greater than a preset speed.

[0101] An automatic obstacle avoidance button may be provided on the electric vehicle 10 for the driver to operate. Exemplarily, the automatic obstacle avoidance button may be a physical button, and the driver may press the physical button to start the automatic obstacle avoidance mode of the electric vehicle 10, thereby starting the drift obstacle avoidance control when the distance between the electric vehicle 10 and the obstacle is less than the preset distance when the speed of the electric vehicle 10 is greater than the preset speed. Also exemplarily, the automatic obstacle avoidance button may be a virtual button on the central control screen, and the driver may start the automatic obstacle avoidance mode of the electric vehicle 10 by selecting the automatic obstacle avoidance mode. Also exemplarily, the automatic obstacle avoidance button may also be set indirectly, for example, by being combined with the button of the smart driving mode or by default starting the automatic obstacle avoidance mode of the electric vehicle 10 when the driver turns off other buttons.

[0102] It should be understood that the vehicle controller provided in the present application may be a vehicle controller 20, a motor controller 40, an intelligent driving controller 70, or other separately configured controller with control capabilities.

[0103] The drift obstacle avoidance control method provided in the embodiment of the present application is used to control the electric vehicle 10 to drift to one side when the electric vehicle 10 encounters an obstacle, and use drift to make the electric vehicle oversteer to avoid the obstacle, thereby avoiding damage caused by collision. The vehicle controller senses the road adhesion, so that the rear wheels break through the road adhesion limit. There is no need to rely on the driver's operation for controlled drift, and the signal transmission time is short, which improves the safety of the vehicle. Figure 4 and Figure 5 The drift obstacle avoidance control method and vehicle controller provided in the embodiment of the present application are described at the first moment t1, the second moment t2, the third moment t3 and the fourth moment t4 during the driving process of the electric vehicle 10 when the speed is greater than the preset speed. Figure 4 is a signal timing diagram of the electric vehicle 10 during driving, Figure 4 This includes the relationship between the distance between the electric vehicle and the obstacle and the steering wheel angle, rear wheel drive torque, braking force, and the difference between the front and rear wheel drive torques during the driving of the electric vehicle.

[0104] In one embodiment, before the first moment t1, the user controls the electric vehicle to start the automatic obstacle avoidance mode by touching the central control screen of the electric vehicle 10 or activating the automatic obstacle avoidance button. The automatic obstacle avoidance mode is used to control the steering system and drive system of the electric vehicle 10 when the electric vehicle 10 is traveling at a speed greater than a preset speed so that the electric vehicle 10 avoids obstacles.

[0105] Drifting obstacle avoidance can be used as an optional operating mode of the electric vehicle 10. Only when the user has previously activated the automatic obstacle avoidance mode will drifting obstacle avoidance control be performed when a collision is about to occur.

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

[0107] The electric vehicle 10 can detect the environment around the electric vehicle and the running status information of the electric vehicle 10 through the perception system. The perception system may include sensors such as cameras, laser radars, millimeter wave radars, etc. for sensing the surrounding environment, and collecting and processing environmental information and in-vehicle information, mainly 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 for detecting vehicle body status and electric vehicle driving information. The perception data may include information such as relative distance, relative vehicle speed, relative acceleration, and lane information. The perception data may also include information such as electric vehicle speed, acceleration, roll angle, and yaw angle. The electric vehicle can detect the information of the electric vehicle 10 and obstacles based on the acquired perception data, and plan a driving path. The perception system sends the detected distance to the obstacle to the vehicle controller, and the vehicle controller determines whether to perform drift obstacle avoidance control based on the vehicle speed and the distance to the obstacle.

[0108] During the driving process of the electric vehicle 10 at a speed greater than the preset speed, when it is detected that the distance between the electric vehicle 10 and the obstacle is less than the preset distance, the drift obstacle avoidance control is started. It should be understood that when the distance between the electric vehicle 10 and the obstacle is less than the preset distance, the electric vehicle 10 may not be able to avoid a collision or a more serious collision may occur when emergency braking starts from the preset speed, so the drift obstacle avoidance control method of the electric vehicle 10 is started to control the electric vehicle 10 to drift to avoid the obstacle. The preset speed and the preset distance can be pre-calibrated according to actual vehicle experiments and / or model calculations, or can be pre-set by comprehensively considering the vehicle requirements and vehicle performance.

[0109] It is easy to understand that the speed at which the electric vehicle 10 can perform drifting to avoid obstacles has not only a lower limit but also an upper limit. When the speed of the electric vehicle 10 is greater than or equal to the speed limit, no matter whether the electric vehicle 10 adopts emergency braking or drifting to avoid obstacles, it may not be able to avoid collision with obstacles.

[0110] like Figure 4 and Figure 5 As shown, in one embodiment, during the driving process 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 is less than a preset distance, the steering wheel of the electric vehicle is controlled to rotate. At a second moment t2 after the first moment t1, the driving torque of the two rear wheels of the electric vehicle 10 is controlled to increase.

[0111] At the first moment t1, 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. At the second moment t2, the driving torque of the two rear wheels of the electric vehicle increases, breaking through the adhesion of the road surface, and the rear wheels begin 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 skids, and the wheels travel along the tangent direction of the body circumference, and the electric vehicle drifts. It should be understood that the second moment t2 can be very close to the first moment t1, and the electric vehicle 10 can adjust the driving torque of the rear wheels to increase after the steering wheel is turned, or it can start to adjust the driving torque of the rear wheels to increase during the steering wheel rotation. In this application, the driving torque of the wheel can be understood as the torque output by the drive motor used to drive the wheel. The road adhesion coefficient is the magnitude of the friction between the wheel and the road. The magnitude 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 degree of wear. Under different road conditions and weather conditions, the corresponding road adhesion coefficient may be different. When the wheel's adhesion to the road changes, the speed and torque of the drive motor used to drive the wheel will also change. Therefore, the change in the road adhesion can be sensed and observed through the change in the speed of the drive motor detected by the resolver sensor. The actual torque actually output by the drive motor reflects the road adhesion to a certain extent, so the road adhesion can be accurately and quickly observed in real time based on the resolver signal and the torque signal. According to the solution of the present application, the road adhesion is observed in real time, the rear wheel drive torque is adjusted so that the rear wheel breaks through the critical adhesion limit, the rear wheel is actively controlled to slip, and 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.

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

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

[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 moving straight, the electric vehicle 10 can be braked by controlling the drive motor 30 to output reverse torque and / or controlling the braking system 60 to output braking force, thereby shifting the center of gravity of the electric vehicle 10, reducing the axle load of the rear axle of the electric vehicle 10, and facilitating the rear axle wheels to break through the adhesion of the road surface, thereby providing favorable conditions for the electric vehicle to drift.

[0115] And at the first moment t1, the drive motor 30 is controlled to stop outputting the reverse torque and / or the brake 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 brake system 60 and the reverse torque output by the drive motor 30 can be used in coordination. Within the capacity of the drive system, the reverse torque output by the drive motor 30 is preferentially used for braking. When the drive system capacity is insufficient, the braking force of the brake system 60 is used as a supplement, and the response is accurate and rapid.

[0117] It should also be understood that in some cases, it may be too late to brake, and transferring the rear wheel load of the electric vehicle is not a necessary condition for drifting, so braking may not be performed before the first moment.

[0118] In one embodiment, at the first moment t1, the steering wheel angle of the electric vehicle 10 is controlled to increase as the speed of the electric vehicle 10 increases, and the steering wheel angle of the electric vehicle 10 is controlled to decrease as the distance between the electric vehicle 10 and the obstacle increases.

[0119] The faster the speed of the electric vehicle 10 or the closer the distance between the electric vehicle 10 and the obstacle, the shorter the time it takes for the electric vehicle 10 to hit the obstacle, and the larger the angle required for drifting to avoid the obstacle. Therefore, the steering angle of the steering wheel increases with the increase of the speed and increases with the decrease of the distance from the obstacle. The slower the speed of the electric vehicle 10 or the farther the distance between the electric vehicle 10 and the obstacle, the longer the time it takes for the electric vehicle 10 to hit the obstacle, and the larger the margin required for drifting to avoid the obstacle. Therefore, the steering angle of the steering wheel decreases with the decrease of the speed and decreases with the increase of the distance from the obstacle.

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

[0121] Continue to see 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 moment t2, the driving torque of the two rear wheels of the electric vehicle 10 increases, breaking through the adhesion of the road surface, and the rear wheels begin to slip. The lateral force on the electric vehicle 10 is greater than the lateral friction limit of the tires, so that the electric vehicle 10 skids, and the wheels travel along the tangent direction of the body circle, and the electric vehicle 10 drifts. The essence of achieving drift is to accurately control the electric vehicle 10 to be in a critical stable state of oversteering, and the rear wheels break through the critical adhesion limit, and consciously let the vehicle skid. It is necessary to accurately and quickly observe the adhesion limit of the road surface to achieve effective control of drift obstacle avoidance.

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

[0124] When the adhesion of the wheel to the road changes, the speed and torque of the drive motor 30 used to drive the wheel will also change. Therefore, the change in the speed of the drive motor 30 detected by the resolver sensor can be used to perceive the change in road adhesion. The actual torque actually output by the drive motor 30 reflects the adhesion ability of the road to a certain extent, so that the road adhesion ability can be accurately and quickly observed in real time based on the resolver signal and the torque signal.

[0125] In one embodiment, at the second moment 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 road adhesion capacity, which can be detected based on the resolver signal and the output torque of the drive motor, so as to avoid excessive slippage and danger caused by the target value far exceeding the road adhesion capacity.

[0127] The faster the speed of the electric vehicle 10 or the closer the distance between the electric vehicle and the obstacle, the shorter the time it takes for the electric vehicle 10 to hit the obstacle, and the rear wheels of the electric vehicle 10 need to slip faster. Therefore, the driving torque for controlling the rear wheels increases with the increase of the vehicle speed and increases with the decrease of the distance from the obstacle. The slower the speed of the electric vehicle 10 or the farther the distance between the electric vehicle 10 and the obstacle, the longer the time it takes for the electric vehicle 10 to hit the obstacle, and the margin of the slip degree of the rear wheels of the electric vehicle 10 is larger. Therefore, the driving torque for controlling the rear wheels decreases with the decrease of the vehicle speed and decreases with the increase of the distance from the obstacle.

[0128] Continue to see Figure 4 and Figure 5 In one embodiment, between the second moment t2 and the third moment 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 grip. The front wheels are steering wheels. If the front wheels lose grip first, it will lead to the loss of some or almost all grip, and the steering effect will be reduced or lost. Under the same steering wheel angle, the actual vehicle rotation angle is smaller than the rotation angle generated when there is grip, resulting in understeering. For the rear wheels, the rear wheels are in the critical stability range and the nonlinear range of the friction limit circle of the tire, and tend to skid. The control goal of the rear wheels is to make the rear wheels lose or partially lose grip, so that the electric vehicle will drift. 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 under control.

[0130] In one embodiment, the control method further includes: between the second moment t2 and the third moment t3, controlling the slip rate of the two rear wheels to be greater than a preset value.

[0131] The rotation speed of the drive motor can be obtained through the resolver signal of the resolver sensor. The angular velocity of the wheel can be calculated through the rotation speed of the drive motor and the transmission ratio of the electric vehicle. The slip rate of each wheel can be obtained by combining the wheel radius and the speed of the electric vehicle. The electric vehicle can adjust the driving torque of the rear wheel according to the slip rate of the rear wheel. For the rear wheel, during the drift process, it is hoped that the slip rate of the wheel on the rear axle is in the critical stability range, in the nonlinear range of the friction limit circle of the tire, and tends to slide sideways. By controlling the slip rate of the two rear wheels to be greater than the preset value, the electric vehicle can be placed in a drifting state.

[0132] In one embodiment, between the second time t2 and the third time t3 , the driving torque controlling the rear wheels of the electric vehicle 10 varies with the sideslip angle of the center of mass of the electric vehicle 10 .

[0133] The electric vehicle 10 can detect the information of the electric vehicle and the obstacle based on the acquired sensing 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 sideslip angle during the drifting obstacle avoidance process of the electric vehicle 10 can be determined. Thus, the electric vehicle 10 controls the magnitude of the rear wheel driving torque according to the actual center of mass sideslip angle of the electric vehicle 10. When the center of mass sideslip angle is less than the target center of mass sideslip angle, the rear wheel driving torque is increased, and when the center of mass sideslip angle is greater than the target center of mass sideslip angle, the rear wheel driving torque is reduced.

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

[0135] Between the second moment t2 and the third moment t3, the electric vehicle is in the process of drifting and avoiding obstacles, and the rear wheel driving torque is different from the torque indicated by the opening of the accelerator pedal. The rear wheel driving torque does not change with the change of the opening of the brake pedal. At this time, the torque closed loop is performed inside the motor controller 40, which directly determines the rear wheel driving torque, which is different from the torque indicated by the opening of the accelerator pedal.

[0136] Continue to see Figure 4 and Figure 5 At a third moment t3 after the second moment t2, the distance between the electric vehicle 10 and the obstacle is greater than a second preset distance, and the driving torque of the two rear wheels is controlled to decrease.

[0137] At the third moment t3, the electric vehicle 10 changes its driving trajectory through 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 obstacle avoidance is achieved, and drifting can be stopped. The driving torque of the two rear wheels is controlled to be reduced so that the driving torque of the two rear wheels is within the road adhesion limit and no slipping occurs.

[0138] Continue to see Figure 4 and Figure 5 In one embodiment, at a fourth moment t4 after the third moment t3, the driving torque of the two rear wheels is controlled to be reduced to zero, and the braking system 60 of the electric vehicle 10 is controlled to increase the output braking force.

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

[0140] Furthermore, the steering wheel of the electric vehicle 10 can also be controlled to return to the center position.

[0141] It should be understood that after the third moment t3, the electric vehicle 10 can also be controlled to continue running, 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.

[0142] In one embodiment, after a first moment t1, in response to a change in the opening of an accelerator pedal, a brake pedal, or a steering wheel angle operated by a user, control of the steering wheel rotation 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 drifting and obstacle avoidance are mainly controlled in the intelligent driving or automatic driving scenarios of the electric vehicle 10. When the user intervenes in the operation during this process, the human driving signal should be given priority. When it is detected that the driver has taken active actions, such as turning the steering wheel, stepping on the accelerator pedal or stepping on the brake pedal, the electric vehicle 10 determines that the driver has intervened, stops automatic drifting and obstacle avoidance, and performs control in response to the driver's operation.

[0144] According to the solution of the present application, when the distance to an obstacle is close, the steering is controlled and the rear wheel torque output is adjusted so that the rear wheels break through the critical adhesion limit, and multiple systems are coordinated to automatically control the controlled drift of the electric vehicle to avoid collision with the obstacle, thereby improving the stability of the obstacle avoidance operation, responding accurately and quickly, and effectively improving the safety of the vehicle.

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

[0146] It should be understood that the vehicle controller provided in the present application may be a vehicle controller 20, a motor controller 40, an intelligent driving controller 70, or other separately configured controller with control capabilities.

[0147] In one embodiment, the vehicle controller can be mounted in a separate power domain controller or in the motor controller 40. If it is mounted in the motor controller 40, it is necessary to transmit the drift obstacle avoidance trajectory information and chassis CAN information planned by the intelligent driving controller to the motor controller 40 side, and directly connect the motor controller 40 to the steering system and other components, and the motor controller 40 directly monitors the changes in the road adhesion ability in real time according to the rotary signal on the drive motor 30 side, so that the torque control delay can be reduced by at least 20ms. The motor controller sends the braking signal to the braking system 60 and the steering signal to the steering system. Thus, the drive system, the braking system 60 and the steering system cooperate to achieve controlled drift.

[0148] In one embodiment, the vehicle controller can also be mounted in the vehicle controller 20. The motor controller sends the resolver signal or the detected change in road adhesion to the vehicle controller 20 via CAN communication. The vehicle controller 20 controls the drift and obstacle avoidance by combining the distance to the obstacle obtained by the perception system and the drift and obstacle avoidance trajectory information planned by the intelligent driving controller, and sends the torque signal to the motor controller 40, the brake signal to the brake system 60, and the steering signal to the steering system. Thus, the drive system, the brake system 60 and the steering system cooperate to achieve controlled drift.

[0149] The vehicle controller can integrate longitudinal and lateral control into the same controller, coordinate driving and braking control, realize joint control, reduce time delay, and improve control accuracy and response speed.

[0150] like Figure 6 As shown, the perception system of the electric vehicle 10 perceives the information of 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 according to the actual trajectory of the electric vehicle 10 (including the heading angle, yaw angle, vehicle speed and other signals of the electric vehicle 10) and the target drift obstacle avoidance trajectory (including the target center of mass sideslip angle, target yaw angular velocity, target vehicle speed, etc.) parameters.

[0151] The vehicle controller observes the resolver signal and torque signal, and the observer observes the actual vehicle's center of mass side slip angle and actual trajectory parameters. Through the regulation of the vehicle controller, the torque command and steering angle / steering torque command are output to the execution structure. Among them, the torque command indicates the target driving torque to the drive system, and the steering angle / steering torque command indicates the actual steering angle / actual steering torque to the steering system.

[0152] The vehicle controller adjusts the output torque of the drive motor 30 by observing the road adhesion in real time, so that the rear wheels break through the critical adhesion limit, consciously slip, and create favorable conditions for the vehicle to drift.

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

[0154]

[0155] Where ω is the yaw angular velocity, represents the rate of change of yaw rate, β is the sideslip angle of center of mass, is the rate of change of the sideslip angle of the center of mass, a is the distance from the center of mass to the front axle, b is the distance from the center of mass to the rear axle, F yf is the lateral force of the front wheel, F yr is the lateral force of the rear wheel, Iz is the moment of inertia, F xr is the rear wheel longitudinal force, δ is the front wheel steering angle, m is the vehicle mass, is the rate of change of vehicle speed, e is the lateral error between the actual vehicle position and the target trajectory, and Δφ represents the heading angle error. Written in the form of state space:

[0156]

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

[0158] In one embodiment, the vehicle controller uses x(t) as the control target and u(t) as the control amount to perform trajectory control on the electric vehicle 10. Different from other trajectory tracking and control, the important control target of drift obstacle avoidance is a larger center of mass sideslip angle, so the weight of the center of mass sideslip angle will be relatively large.

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

[0160] T r =F xr ×r / RR.

[0161] Among them, r is the tire radius and RR is the reduction ratio.

[0162] The vehicle controller controls the rear wheel drive torque to break through the critical road adhesion limit and control Tr>road adhesion limit, thereby achieving drift.

[0163] The vehicle controller uses the resolver signal of the drive motor 30 to accurately determine the slip rate and perform a millisecond-level closed loop, while accurately identifying the adhesion ability of the corresponding wheel / axle of the electric drive to contact the road surface during slip.

[0164] Combination Figure 4 , Figure 5 as well as Figure 6 In one embodiment, during the driving process 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 is less than a preset distance, the steering wheel of the electric vehicle is controlled to rotate. At a second moment t2 after the first moment t1, the driving torque of the two rear wheels of the electric vehicle 10 is controlled to increase.

[0165] like Figure 4 and Figure 5As shown, in one 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 the first moment t1, the perception system detects that the distance between the electric vehicle 10 and the obstacle is less than the preset distance and sends a distance signal to the vehicle controller. The vehicle controller sends a steering angle command to the steering system in response to the distance signal. The steering system controls the steering wheel of the electric vehicle in response to the steering angle command to rotate, so that the electric vehicle generates a side slip angle and a lateral force. At the second moment after the first moment t1, the distance between the electric vehicle 10 and the obstacle is further reduced. The vehicle controller sends a torque command to the drive system. The drive system controls the two rear wheels of the electric vehicle to increase the driving torque in response to the torque command, breaking through the adhesion of the road surface, and the rear wheels begin 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 skids, and the wheels travel along the tangent direction of the body circumference. The electric vehicle drifts, so that the electric vehicle 10 avoids the obstacle. It should be understood that the second moment t2 can be very close to the first moment t1, and the electric vehicle 10 can adjust the driving torque of the rear wheel to increase after the steering wheel is turned, or it can start to adjust the driving torque of the rear wheel to increase during the steering wheel turning process. In the present application, the driving torque of the wheel can be understood as the torque output by the drive motor used to drive the wheel. The road adhesion coefficient is the magnitude of the friction between the wheel and the road, and the magnitude 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 degree of wear. 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 used to drive the wheel will also change. Therefore, the change in the road adhesion can be perceived by the change in the speed of the drive motor detected by the rotary sensor. The actual torque actually output by the drive motor reflects the adhesion of the road to a certain extent, so that the road adhesion can be accurately and quickly observed in real time according to the rotary signal and the torque signal. According to the solution of the present application, the road adhesion ability is observed in real time, the rear wheel drive torque is adjusted to make the rear wheels break through the critical adhesion limit, and the rear wheels are actively controlled to slip, creating favorable conditions for the vehicle to drift, so that the drifting and obstacle avoidance process is reliably controlled, thereby improving the safety of the vehicle.

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

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

[0168] The motor controller actually executes the torque based on the vehicle wheel speed, motor speed, torque signal feedback, and the current wheel / axle's corresponding road adhesion.

[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 determines whether the vehicle speed is greater than the preset speed and less than the speed limit. If the vehicle speed is within the applicable range of drift obstacle avoidance, drift obstacle avoidance control is performed.

[0170] The specific drift obstacle avoidance control method can be found in the above description.

[0171] Next, the target center of mass sideslip angle, target yaw angle, etc. are calculated based on the drift obstacle avoidance trajectory.

[0172] The vehicle controller calculates the driving motor torque and steering angle according to the road adhesion capability, and sends them to the motor controller 40 and the steering system respectively.

[0173] Finally, the motor controller controls the drive motor to output the calculated drive torque, and the steering system controls the electric vehicle 10 to turn to the calculated steering angle to complete drifting and obstacle avoidance.

[0174] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A control method for electric vehicle drifting and obstacle avoidance, characterized in that: The control method is used to control the steering system and the driving system of the electric vehicle when the speed of the electric vehicle is greater than a preset speed so that the electric vehicle avoids a detected obstacle, and the control method includes: At a first moment after the distance between the electric vehicle and the obstacle is less than a preset distance, controlling the steering wheel of the electric vehicle to rotate; At a second time after the first time, the driving torque of the two rear wheels of the electric vehicle is controlled to increase.

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

3. The control method according to claim 2, characterized in that: The control method further comprises: At a fourth time after the third time, the driving torque of the two rear wheels is controlled to be reduced to zero, and the brake system of the electric vehicle is controlled to increase the output braking force.

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

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

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

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

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

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

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

11. The control method according to claim 2, characterized in that: The control method further comprises: Between the second time point and the third time point, the driving torque for controlling the rear wheels of the electric vehicle is different from the torque indicated by the opening degree of the accelerator pedal.

12. The control method according to any one of claims 1 to 11, characterized in that: The control method further comprises: After the first moment, in response to changes in the opening of the accelerator pedal, the opening of the brake pedal or the steering wheel angle operated by the user, stop controlling the steering wheel rotation of the electric vehicle and control the driving torque of the two rear wheels to be equal to the torque indicated by the opening of the accelerator pedal.

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

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

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

Images