Drifting-assisting motor controller, control method and electric vehicle

Abstract

The invention discloses a drifting-assisting motor controller, a drifting-assisting motor control method and an electric vehicle, relates to the field of new energy vehicles, and can be applied to pure electric vehicles and hybrid vehicles. The motor controller is used for controlling the driving motor to output torque so as to drive wheels of the electric automobile, and is used for responding to the situation that the ratio of the transverse acceleration of the electric automobile to the speed of the electric automobile is larger than a drift threshold value in the running process of the electric automobile. And the torque output by the driving motor is actively adjusted according to the change of the slip rate of the wheels. According to the scheme, the torque output of the driving motor is rapidly closed in the motor controller, it is guaranteed that the tires are located in the friction limit circle nonlinear interval, have the steering capacity and are located in the drifting controllable area, the requirement for a driver is lowered, and the pleasure of driving is achieved.

Description

Technical Field

[0001] This application relates to the field of new energy vehicles, and more specifically, to a motor controller for assisting drift, a control method, and an electric vehicle. Background Technology

[0002] Drifting is a car driving technique commonly used in racing or performances. Drifting occurs when some of the vehicle's tires lose traction, causing the vehicle to turn at a large sideslip angle. Drivers can perform drifts by manipulating the drive, brakes, and steering wheel to achieve small-radius turns, catering to the needs of racing, driving pleasure, and maneuvering in tight spaces.

[0003] However, drifting usually requires the driver to have a high level of driving skill and a certain degree of timing. When the road surface is uneven, the wheel slip ratio will fluctuate, requiring the driver to quickly perceive the vehicle's state and make adjustments. Novices find it difficult to perform controlled drifting, and inaccurate slip ratios will accelerate tire wear, leading to excessive tire wear.

[0004] Therefore, improving the control accuracy during drift operation is a problem that needs to be solved. Summary of the Invention

[0005] This application provides a motor controller, control method, and electric vehicle for assisting drifting. During the drifting and cornering process of the electric vehicle, the change in road surface adhesion coefficient is accurately determined by the resolver sensor signal of the drive motor, and the torque output is adjusted instantaneously to control the drifting state of the electric vehicle. The solution of this application has low control loop delay and fast response speed, which reduces the skill requirements of the driver for drifting operation and improves the driving experience and safety of the vehicle.

[0006] In a first aspect, this application provides a motor controller for assisting drifting. The motor controller is used to control the output torque of the drive motor to drive the wheels of an electric vehicle. During the driving process of the electric vehicle, in response to the ratio of the lateral acceleration of the electric vehicle to the speed of the electric vehicle being greater than a drift threshold, the motor controller actively adjusts the magnitude of the output torque of the drive motor according to the change in the slip ratio of the wheels.

[0007] This motor controller is suitable for pure electric vehicles or hybrid vehicles. The electric vehicle can have a distributed motor or centralized motor architecture, possessing multiple drive motors and multiple motor controllers. The motor controller can be any one of these multiple motor controllers. The drive motor can be a wheel-side motor or a hub motor, capable of independently driving one wheel or simultaneously driving two wheels on the same axle. The motor controller can output three-phase AC power to the drive motor, thereby controlling the output torque of the drive motor.

[0008] Drifting is a special driving technique that involves causing the rear wheels to lose or significantly reduce traction while turning, resulting in oversteer, rear-end swing, and a sliding motion through the corner. This process requires a high level of skill from the driver, as well as sensitive control over the vehicle's dynamics through coordinated operation of the steering wheel, accelerator, and brakes. Drifting typically involves two methods: one is to reduce or eliminate lateral traction through braking, and the other is to reduce or eliminate lateral traction through driving. The motor controller provided in this application can be used to assist in drifting by reducing rear-end traction through driving. The assisted drifting in this application refers to the electric vehicle using algorithms to assist the driver in adjusting and better sensing the vehicle's posture to complete the drifting maneuver.

[0009] The timing for assisted drift control can be determined by monitoring the lateral acceleration and speed of the electric vehicle. When the ratio of lateral acceleration to speed exceeds a drift threshold, the vehicle is considered to be in a drift state, requiring assisted drift control. The drift threshold can be a given value, obtained through vehicle calibration or input by the driver. The motor controller can obtain the vehicle speed and lateral acceleration from the vehicle controller, or it can directly connect to the vehicle's sensors to obtain these parameters. This application does not limit the method by which the motor controller obtains the vehicle speed and lateral acceleration.

[0010] The motor controller adjusts the output torque of the drive motor based on vehicle speed and the rotational speed of the drive motor indicated by the electric vehicle's resolver sensor. During drifting, due to uneven road surface adhesion, the adhesion force on the tires fluctuates in real time. When the tire adhesion force changes, the tire slip ratio also changes, and correspondingly, the rotational speed and torque of the drive motor driving the tires change. Therefore, the change in road surface adhesion can be sensed by detecting the change in the rotor speed of the drive motor by the resolver sensor. The motor controller can then adjust the actual output torque of the drive motor based on the resolver signal, thereby precisely controlling the tire slip ratio, causing the rear wheels to tend to sideslip while the front wheels maintain steering.

[0011] Resolver sensors can accurately detect the position, direction, and speed of the drive motor rotor, and are responsible for monitoring and extracting the rotational speed of the drive motor. They have a high sampling rate, are directly connected to the motor controller, have short signal transmission time, and are more stable.

[0012] According to the solution of this application, the change in road surface adhesion coefficient is accurately determined by the resolver sensor signal of the drive motor, and the actual torque adjustment required is accurately calculated in the motor controller. The torque output is adjusted instantaneously to control the drift state of the electric vehicle. The motor controller has a fast closed loop and a rapid response, which reduces the skill requirements of the driver for drifting operations and improves the driving experience and safety of the vehicle.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the motor controller is used to control the drive motor to output torque indicated by the opening of the accelerator pedal of the electric vehicle during the operation of the electric vehicle, in response to the ratio of the lateral acceleration of the electric vehicle to the vehicle speed being less than or equal to a drift threshold. The motor controller is also used to actively control the drive motor to adjust its torque output so that the torque output by the drive motor differs from the torque indicated by the opening of the accelerator pedal, in response to the ratio of the lateral acceleration of the electric vehicle to the vehicle speed being greater than the drift threshold.

[0014] The accelerator pedal in this application can also be called the power pedal or throttle pedal. The opening degree of the accelerator pedal indicates the amount of driving force required by the driver. The larger the opening degree of the accelerator pedal, the greater the driver's demand for driving force, and the greater the torque required from the drive motor. When the motor controller is not performing auxiliary drift control, it can control the drive motor to output the torque indicated by the accelerator pedal opening degree. The larger the accelerator pedal opening degree, the greater the torque output by the drive motor; the smaller the accelerator pedal opening degree, the smaller the torque output by the drive motor. The torque output by the drive motor controlled by the motor controller changes with the change in the accelerator pedal opening degree.

[0015] During the process of the electric vehicle drifting to one side with the assistance of the motor controller, i.e., when the motor controller is in drift control mode, the torque output by the drive motor is different from the torque indicated by the accelerator pedal opening. The torque output by the drive motor does not change with the brake pedal opening. At this time, the motor controller performs a closed-loop torque calculation, which directly determines the torque output by the drive motor, and is different from the torque indicated by the torque signal sent by the vehicle controller.

[0016] According to the scheme of this application, the torque output of the drive motor during drifting is determined by the motor controller according to the algorithm, rather than by the opening of the accelerator pedal, thereby reducing the operating threshold of the driver for drifting, improving the control accuracy and speed, and improving the safety and efficiency of drifting.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the drive motor is used to drive the rear wheels of the electric vehicle. The motor controller adjusts the output torque of the drive motor by: in response to the rear wheel slip ratio increasing to a value greater than the upper limit of the rear wheel slip ratio, controlling the drive motor used to drive the rear wheels to decrease its output torque; and in response to the rear wheel slip ratio decreasing to a value less than the lower limit of the rear wheel slip ratio, controlling the drive motor used to drive the rear wheels to increase its output torque. Wherein, the upper limit of the rear wheel slip ratio is greater than the lower limit of the rear wheel slip ratio.

[0018] An electric vehicle has multiple wheels, including front and rear wheels, and may include a drive motor for driving the rear wheels. A motor controller adjusts the torque output of the drive motor for driving the rear wheels based on the rear wheel slip ratio, which is indicated by the vehicle speed and a resolver sensor corresponding to the drive motor. Specifically, the motor controller controls the drive motor to reduce its output torque in response to a decrease in the rear wheel slip ratio indicated by the vehicle speed and the resolver sensor exceeding an upper limit value. Conversely, in response to a decrease in the rear wheel slip ratio indicated by the vehicle speed and the resolver sensor falling below a lower limit value, the controller controls the drive motor to increase its output torque.

[0019] The motor controller obtains the rotational speed of the drive motor through the resolver signal from the resolver sensor. The angular velocity of the wheels can be calculated from the drive motor speed and the transmission ratio of the electric vehicle. Therefore, by combining the wheel radius with the speed of the electric vehicle, the slip ratio of each wheel can be obtained. In this application, the slip ratio can be either the slip ratio or the rotational slip ratio.

[0020] The motor controller can adjust the torque of the drive motor used to drive the rear wheels based on the slip ratio of the rear wheels.

[0021] For the rear wheels, during drifting, it is desirable for the slip ratio of the rear axle wheels to be within the critical stability range, which is within the non-linear range of the tire's friction limit circle, tending towards sideslip. Therefore, the upper and lower limits of the rear wheel slip ratio are the upper and lower limits, respectively. When the rear wheel slip ratio is higher than the upper limit, the motor controller can control the drive motor used to drive the rear wheels to reduce torque output; when the rear wheel slip ratio is lower than the lower limit, the motor controller can control the drive motor used to drive the rear wheels to increase torque output.

[0022] According to the solution in this application, a rapid closed loop is established within the motor controller to respond to changes in road surface adhesion and control the slip ratio of the rear wheels. This ensures that the rear-wheel drive tends to sideslip and remains within the nonlinear region of the friction limit circle, reducing additional tire wear and improving the safety and controllability of drifting.

[0023] In conjunction with the first aspect, in some implementations of the first aspect, the drive motor is used to drive the front wheels of the electric vehicle. The motor controller adjusts the magnitude of the torque output by the drive motor, specifically by controlling the drive motor to reduce its output torque in response to an increase in the slip ratio of the front wheels exceeding an upper limit value. Conversely, in response to a decrease in the slip ratio of the front wheels exceeding a lower limit value, the drive motor to increase its output torque. The upper limit value for the front wheels is greater than the lower limit value.

[0024] An electric vehicle has multiple wheels, including front and rear wheels. The electric vehicle may include a drive motor for driving the rear wheels and a drive motor for driving the front wheels. A motor controller adjusts the torque output of the drive motor for driving the front wheels based on the slip ratio of the front wheels, indicated by the vehicle speed and a resolver sensor corresponding to the drive motor. Specifically, the motor controller controls the drive motor to reduce its output torque in response to a change in the vehicle speed and the resolver sensor indicating a slip ratio greater than an upper limit for the front wheels. Conversely, in response to a change in the vehicle speed and the resolver sensor indicating a slip ratio less than a lower limit for the front wheels, the controller controls the drive motor to increase its output torque.

[0025] The motor controller can adjust the torque of the drive motor used to drive the front wheels based on the slip ratio of the front wheels.

[0026] For the front wheels, it's desirable for them to maintain traction during a drift. Since the front wheels are the steering wheels, if they lose traction first, a high slip ratio can lead to a loss of some or almost all of that traction, resulting in reduced or lost steering performance. With the same steering wheel angle, the actual turning angle produced by the vehicle is smaller than that produced with a lower slip ratio, leading to understeer.

[0027] Therefore, the upper and lower limits of the slip ratio for the front wheels are the upper and lower limits, respectively. When the slip ratio of the front wheels is higher than the upper limit, the motor controller can control the drive motor used to drive the front wheels to reduce torque output; when the slip ratio of the front wheels is lower than the lower limit, the motor controller can control the drive motor used to drive the front wheels to increase torque output.

[0028] According to the solution in this application, a rapid closed loop is established within the motor controller to respond to changes in road surface adhesion and control the slip ratio of the front wheels. This enables the electric vehicle to have steering ability during drifting, keeping it within the controllable drift zone, reducing the demands on the driver, and improving the safety and controllability of drifting.

[0029] In conjunction with the first aspect, in some implementations of the first aspect, the upper limit value of the rear wheel is greater than the upper limit value of the front wheel, and the lower limit value of the rear wheel is greater than the lower limit value of the front wheel.

[0030] The slip ratio control target ranges for front-wheel drive and rear-wheel drive tires differ. The motor controller adjusts the torque output of the drive motor to control the slip ratio of the front and rear wheels within a set range to achieve the goal of assisting drifting. The slip ratio control target for rear-wheel drive wheels is to cause the rear wheels to lose or partially lose traction, causing the electric vehicle to fishtail. The slip ratio control target for front-wheel drive wheels is to maintain the steering ability of the front wheels. Therefore, the slip ratios of front-wheel drive and rear-wheel drive are controlled separately.

[0031] According to the scheme of this application, the motor controller senses the road surface adhesion and realizes the adjustment of the actual output torque of the front and rear drives. The adjusted torque is quickly closed-looped inside the motor controller. The front drive slip ratio control target and the rear drive control target are adapted respectively to ensure that the rear drive tends to sideslip and the front drive has steering ability, which is in the drift controllable zone.

[0032] In conjunction with the first aspect, in some implementations of the first aspect, the opening of the accelerator pedal of the electric vehicle is also used to indicate the upper limit value of the rear wheel, the lower limit value of the rear wheel, the upper limit value of the front wheel, and the lower limit value of the front wheel, which change with the opening of the accelerator pedal.

[0033] The motor controller can receive the target range of front and rear wheel slip ratios from the vehicle controller. The vehicle controller detects the driver's controlled drift position and the accelerator pedal opening to calculate the target range of front and rear wheel slip ratios, and then sends it to the motor controller.

[0034] The motor controller can also directly obtain the front and rear drive slip ratio control target range from the accelerator pedal opening.

[0035] According to the scheme in this application, slip ratio control is performed on the front and rear wheels respectively, which improves the controllability and safety of the electric vehicle drifting process.

[0036] In one possible implementation, the motor controller adjusts the torque output of the drive motor to achieve target slip ratios for multiple wheels, each indicated by a vehicle speed and a resolver sensor of the electric vehicle. The target slip ratios for the multiple wheels are indicated by the accelerator pedal opening of the electric vehicle, with the target slip ratio for the front wheels being less than that for the rear wheels.

[0037] Slip ratio control for front and rear wheels can also be a target slip ratio rather than a range. By controlling the torque of the drive motor in a closed loop within the motor controller, the magnitude of the slip ratio is changed, allowing for precise control of the slip ratio of the front and rear wheels.

[0038] According to the solution in this application, the motor controller senses changes in road surface adhesion and adjusts the front and rear drive slip ratio control targets accordingly to precisely control the tire slip ratio and reduce additional tire wear.

[0039] In conjunction with the first aspect, in some implementations of the first aspect, the motor controller is used to actively adjust the magnitude of the torque output by the drive motor according to the change in the wheel slip ratio when the opening of the accelerator pedal of the electric vehicle is greater than the accelerator threshold and the steering angle of the electric vehicle is greater than the angle threshold.

[0040] The motor controller will only enter the auxiliary drift control mode when the following conditions are met: the accelerator pedal opening is greater than the accelerator threshold, the steering wheel angle is greater than the angle threshold, and the ratio of the lateral acceleration to the vehicle speed is greater than the drift threshold.

[0041] According to the solution in this application, the driver's operation is simplified during drifting cornering. The slip ratio is controlled by the motor controller, which makes it easier to achieve drifting operation of electric vehicles, lowers the operating threshold for drivers to drift, and improves the driving experience of the vehicle.

[0042] In conjunction with the first aspect, in some implementations of the first aspect, the motor controller is used to control the drive motor to output torque indicated by the opening of the accelerator pedal in response to the electric vehicle's accelerator pedal being less than or equal to a throttle threshold or the electric vehicle's steering wheel angle being less than or equal to an angle threshold, while actively adjusting the magnitude of the torque output by the drive motor according to the change in wheel slip ratio.

[0043] During a drift in an electric vehicle, the driver can exit or prematurely end the drift by operating certain actions. For example, the driver can end the drift by releasing the accelerator pedal, turning the steering wheel in the opposite direction or straightening it, or pressing the brake pedal. Therefore, when the motor controller detects that one or more of the following conditions are met—that the accelerator pedal opening is less than or equal to a throttle threshold or the steering wheel angle is less than or equal to an angle threshold—the motor controller can terminate the auxiliary drift control and re-respond to changes in the accelerator pedal opening to control the output torque of the drive motor.

[0044] According to the solution proposed in this application, the driver can flexibly control the end of the drift, which improves the safety of drifting, lowers the operational threshold for the driver to drift, and enhances the driving experience of the vehicle.

[0045] In conjunction with the first aspect, in some implementations of the first aspect, the electric vehicle is used to control the electric vehicle to enter drift mode by touching the central control screen of the electric vehicle or activating the drift button, and the motor controller is used to actively adjust the torque output of the drive motor according to the change of the wheel slip ratio when the electric vehicle is in drift mode and the ratio of the lateral acceleration of the electric vehicle to the speed of the electric vehicle is greater than the drift threshold.

[0046] When an electric vehicle is drifting, it enters an assisted drift mode, which can be activated by the driver. The motor controller will only engage assisted drift control when the electric vehicle is in assisted drift mode and the ratio of its speed to the drift threshold is greater than the threshold. Therefore, the motor controller being in assisted drift mode does not necessarily mean it is performing assisted drift control, but rather that the electric vehicle must be in assisted drift mode.

[0047] In one possible embodiment, the electric vehicle includes a drift button. When the drift button is off, the motor controller does not perform assisted drift control and controls the drive motor to output the torque indicated by the accelerator pedal opening. When the drift button is on, the motor controller enters assisted drift mode, detecting the lateral acceleration and vehicle speed of the electric vehicle. When the ratio of the lateral acceleration to the vehicle speed is less than or equal to a drift threshold, the drive motor is controlled to output the torque indicated by the accelerator pedal opening. When the ratio of the lateral acceleration to the vehicle speed is detected to be greater than the drift threshold, the drive motor is controlled to output an adjusted torque. At this time, the torque output by the drive motor is different from the torque indicated by the accelerator pedal opening. That is, the actual torque output by the drive motor is different from the torque indicated by the torque signal sent by the vehicle controller.

[0048] Electric vehicles can be equipped with a drift button for driver operation. For example, the drift button can be a physical button; pressing this physical button activates the electric vehicle's drift assistance mode, causing the motor controller to initiate drift assistance control when the vehicle detects that certain conditions are met. Alternatively, the drift button can be a virtual button on the central control screen, which the driver can select to activate the drift assistance mode. Furthermore, the drift button can also be indirectly configured, for example, integrated into a sport mode button or other function buttons. This application does not limit the method or form of the drift button's configuration.

[0049] According to the proposed solution, by setting a drift mode that the driver can freely choose whether to activate, the controllability and safety of the vehicle are improved, and the driving experience and enjoyment are enhanced.

[0050] Secondly, this application provides a control method for assisting electric vehicle drifting. The electric vehicle includes a motor controller, a drive motor, and multiple wheels. The motor controller controls the output torque of the drive motor to drive the wheels. The control method includes, during the operation of the electric vehicle, when the ratio of the lateral acceleration of the electric vehicle to its speed is less than or equal to a drift threshold, the motor controller controls the drive motor to output torque indicated by the opening of the accelerator pedal. In response to the ratio of the lateral acceleration of the electric vehicle to its speed being greater than the drift threshold, the motor controller actively adjusts the magnitude of the torque output by the drive motor according to changes in the wheel slip ratio. The torque output by the drive motor is different from the torque indicated by the opening of the accelerator pedal.

[0051] In conjunction with the second aspect, in some implementations of the second aspect, the multiple wheels include front wheels and rear wheels. The electric vehicle includes a drive motor for driving the front wheels and a drive motor for driving the rear wheels. The control method further includes a motor controller controlling the drive motor for driving the rear wheels to reduce its output torque in response to an increase in the slip ratio of the rear wheels exceeding an upper limit value. In response to an increase in the slip ratio of the rear wheels exceeding a lower limit value, the drive motor for driving the rear wheels is controlled to increase its output torque. In response to an increase in the slip ratio of the front wheels exceeding an upper limit value, the drive motor for driving the front wheels is controlled to reduce its output torque. In response to an increase in the slip ratio of the front wheels exceeding a lower limit value, the drive motor for driving the front wheels is controlled to increase its output torque. Wherein, the upper limit value of the rear wheels is greater than the lower limit value of the rear wheels, the upper limit value of the front wheels is greater than the lower limit value of the front wheels, the upper limit value of the rear wheels is greater than the upper limit value of the front wheels, and the lower limit value of the rear wheels is greater than the lower limit value of the front wheels.

[0052] The control method includes controlling the drive motor driving the rear wheels to reduce its output torque in response to a vehicle speed and a resolver sensor corresponding to the drive motor driving the rear wheels indicating an increase in the rear wheel slip ratio to a value greater than the upper limit of the rear wheel slip ratio. Conversely, controlling the drive motor driving the rear wheels to increase its output torque in response to a vehicle speed and a resolver sensor corresponding to the drive motor driving the rear wheels indicating a decrease in the rear wheel slip ratio to a value less than the lower limit of the rear wheel slip ratio. Similarly, controlling the drive motor driving the front wheels to reduce its output torque in response to a vehicle speed and a resolver sensor corresponding to the drive motor driving the front wheels indicating an increase in the front wheel slip ratio to a value greater than the upper limit of the front wheel slip ratio. Finally, controlling the drive motor driving the front wheels to increase its output torque in response to a vehicle speed and a resolver sensor corresponding to the drive motor driving the front wheels indicating a decrease in the front wheel slip ratio to a value less than the lower limit of the front wheel slip ratio.

[0053] In conjunction with the second aspect, in some implementations of the second aspect, the control method specifically includes, during the process of the motor controller actively adjusting the magnitude of the torque output by the drive motor according to the change in the wheel slip ratio, in response to the accelerator pedal opening of the electric vehicle being less than or equal to an accelerator threshold or the steering wheel angle of the electric vehicle being less than or equal to an angle threshold, the motor controller controls the drive motor to output the torque indicated by the accelerator pedal opening.

[0054] In conjunction with the second aspect, in some implementations of the second aspect, the control method includes the electric vehicle being controlled to enter drift mode by touching the central control screen of the electric vehicle or activating a drift button. During the operation of the electric vehicle, in response to the electric vehicle being in drift mode and the ratio of the electric vehicle's lateral acceleration to its speed being greater than a drift threshold, the motor controller is used to actively adjust the torque output of the drive motor according to changes in the wheel slip ratio.

[0055] Thirdly, this application provides an electric vehicle including a motor controller, a vehicle controller, an accelerator pedal, a brake pedal, and a steering wheel as described in the first aspect and its various implementations, wherein the accelerator pedal is used to indicate the output torque to the wheels of the electric vehicle, and the brake pedal is used to indicate the output braking force to a plurality of wheels of the electric vehicle.

[0056] In conjunction with the second aspect, in some implementations of the second aspect, the vehicle controller is used to send a torque signal to the motor controller, the torque signal indicating the torque indicated by the opening of the accelerator pedal of the electric vehicle. The vehicle controller is also used to indicate to the motor controller the upper limit value of the rear wheels, the lower limit value of the rear wheels, the upper limit value of the front wheels, and the lower limit value of the front wheels indicated by the opening of the accelerator pedal of the electric vehicle.

[0057] Other beneficial effects can be found in the description of the first aspect, and will not be repeated here. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the vehicle tire friction limit circle provided in an embodiment of this application;

[0059] Figure 2 This is a schematic diagram of an electric vehicle provided in an embodiment of this application;

[0060] Figure 3 This is a schematic diagram of the architecture of an electric vehicle provided in an embodiment of this application;

[0061] Figure 4 This is a schematic diagram of the electric vehicle drifting mode provided in an embodiment of this application;

[0062] Figure 5 This is a schematic diagram of electric vehicle drifting provided in an embodiment of this application;

[0063] Figure 6 This is a schematic diagram of the motor controller provided in an embodiment of this application;

[0064] Figure 7 This is a schematic diagram of the auxiliary drift control provided in the embodiments of this application. Detailed Implementation

[0065] The technical solutions in this application will now be described in conjunction with the accompanying drawings. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments.

[0066] Drifting is a sport that focuses on specific driving techniques. Car drifting involves using oversteer to steer the vehicle sideways through a corner. Drifting occurs through the interaction between the tires and the road surface, generating lateral and longitudinal forces on the tires. When the rear-wheel drive lateral force exceeds the road surface's grip, the tires generate lateral velocity, causing sideslip, and the wheels travel along the tangent of the car's circumference—this is drifting. Drivers can drift by manipulating the drivetrain, brakes, and steering wheel to achieve small-radius turns, satisfying the needs of racing, driving pleasure, and maneuvering in tight areas. However, drifting by a driver requires highly skilled driving techniques, making it difficult for ordinary drivers to perform.

[0067] The principle behind drifting is to cause the rear wheels of a vehicle to lose most or all of their traction, while the front wheels maintain traction. If the front wheels experience any lateral force, the vehicle will fishtail and drift. The rear wheels can typically lose traction through braking or other means.

[0068] Here's an example of drifting via a driving mechanism: First, in the initial stage, the electric vehicle travels straight before drifting and then brakes, as shown below. Figure 1 As shown at point A on the circle representing the limit of friction, shifting the vehicle's center of gravity reduces the axle load on the rear axle, which is beneficial for the rear axle to break through road adhesion. Then comes the sideslip drift phase, during which the driver can adjust the steering wheel, such as... Figure 1 Point B, representing the friction limit circle, generates a sideslip angle and lateral force. Constrained by the friction limit circle, the increased driving force causes the lateral force to decrease, exceeding the rear wheel friction limit circle, generating lateral velocity, and causing sideslip. The wheels travel along the tangent of the vehicle's circumference. Finally, as the drift enters the recovery phase, the driver releases the accelerator, reduces the driving torque, and gradually straightens the steering wheel to reduce the lateral force, thus exiting the drift state.

[0069] In one possible implementation, drifting can be performed by a skilled driver, requiring precise timing of the driving maneuvers. The vehicle's electronic stability program (ESP) controls vehicle stability based on wheel-vehicle speed observations of slip ratio and coefficient of adhesion, requiring the driver to quickly perceive and adjust the vehicle's status.

[0070] It should be understood that due to uneven road surface adhesion, real-time fluctuations in driving force, and slip ratio fluctuations, the time delay of slip ratio and adhesion coefficient observations based on wheel speed and vehicle speed leads to long time delays and low bandwidth in the control closed loop. This results in insufficient bandwidth for controlling yaw acceleration and tire slip ratio, easily causing the vehicle to lose control and spin in circles. Drifting requires skilled driving techniques and has poor controllability, making controlled drifting difficult for novices. Inaccurate slip ratio control by ESP exacerbates tire wear, leading to additional tire wear.

[0071] To address the aforementioned issues, this application provides a motor control unit (MCU) for drift assistance, a control method, and an electric vehicle. During the drifting cornering process of the electric vehicle, the change in road surface adhesion coefficient is accurately determined using the resolver sensor signal of the drive motor, and the torque output is adjusted instantaneously to control the drifting state of the electric vehicle. The control loop has low latency and fast response speed, reducing the skill requirements of the driver for drifting operations and improving the driving experience and safety of the vehicle.

[0072] Figure 2 and Figure 3 This is a schematic diagram of the electric vehicle 10 architecture provided in an embodiment of this application.

[0073] like Figure 2 As shown, the electric vehicle 10 includes a vehicle controller 20, a drive system, a braking system, and multiple wheels 40. The drive system includes a drive motor 30 and a motor controller 50. The motor controller 50 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 braking system is used to brake the electric vehicle 10 by outputting braking force.

[0074] The electric vehicle 10 can be a wheel-side four-motor drive architecture, with the drive motors 30 mounted on the sides of the driving wheels and controlled by individual motor controllers 50. Alternatively, the electric vehicle 10 can be a centralized drive motor architecture, with two drive motors for driving the two front wheels or the two rear wheels mounted together. There can be one or more motor controllers 50. The motor controllers 50 and drive motors 30 can be in one-to-one correspondence, or one motor controller 50 can correspond to multiple drive motors 30. The motor controllers 50 are used to control the output torque of one or more drive motors 30 to drive the electric vehicle 10.

[0075] In one embodiment, such as Figure 3 As shown in (a), the electric vehicle 10 can be a wheel-side four-wheel drive motor drive architecture, with the drive motors mounted on the sides of the driving wheels and controlled by separate motor controllers. The electric vehicle 10 can also be as follows: Figure 3 The centralized four-motor drive architecture shown in (b) has two drive motors for driving the two front wheels or the two rear wheels set together.

[0076] For example, the electric vehicle 10 includes four motor controllers: motor controller 51, motor controller 52, motor controller 53, and motor controller 54. The four motors include drive motor 31, drive motor 32, drive motor 33, and drive motor 34. Motor controller 51 controls drive motor 31 to drive wheel 41, motor controller 52 controls drive motor 32 to drive wheel 42, motor controller 53 controls drive motor 33 to drive wheel 43, and motor controller 54 controls drive motor 34 to drive wheel 44.

[0077] Based on wheel position, the four wheels can be divided into left front wheel, right front wheel, left rear wheel, and right rear wheel. According to axle arrangement, the left and right front wheels are coaxial and connected via the front axle, while the left and right rear wheels are coaxial and connected via the rear axle. Based on location, the left and left rear wheels are on the same side (left side), and the right front and right rear wheels are on the same side (right side). Of the four drive motors, the two motors driving the two front wheels are coaxial, and the two motors driving the two rear wheels are also coaxial.

[0078] In one embodiment, the electric vehicle 10 can also be as follows: Figure 3 As shown in (c), one drive motor drives the two front wheels of the electric vehicle 10, and two motors drive the two rear wheels of the electric vehicle 10 respectively.

[0079] In one embodiment, the various architectures mentioned above can also be combined, for example, the front drive adopts a wheel-side drive motor architecture, and the rear drive adopts a centralized drive motor architecture.

[0080] The motor controller provided in this application can be any one of multiple motor controllers. The following embodiment only uses one motor controller 50 as an example. The operation of other motor controllers can be understood similarly by referring to the description.

[0081] The electric vehicle 10 also includes an accelerator pedal, a brake pedal, and a steering wheel. The accelerator pedal is used to indicate the torque output to the wheels of the electric vehicle 10, and the brake pedal is used to indicate the braking force output to the multiple wheels of the electric vehicle 10.

[0082] In one embodiment, the motor controller 50 includes a signal interface, through which the motor controller 50 is connected to the vehicle controller 20 and other motor controllers 50. The vehicle controller 20 is signal-connected to the accelerator pedal, and calculates the vehicle torque demand based on the accelerator pedal opening during the operation of the electric vehicle 10, and sends a torque signal to the motor controllers 50 according to the vehicle torque demand. Each motor controller 50 controls the corresponding drive motor 30 to output torque to drive the corresponding wheel according to the torque signal indication.

[0083] In one embodiment, each motor controller 50 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.

[0084] In one embodiment, the vehicle controller 20 is connected to the brake pedal 120. The vehicle controller 20 calculates the vehicle braking demand based on the brake pedal opening of the electric vehicle 10 during driving and controls the corresponding braking device to brake the corresponding wheels according to the vehicle braking demand.

[0085] In one embodiment, each motor controller 50 may also be directly connected to the brake pedal.

[0086] In one embodiment, the motor controller 50 is connected to a resolver sensor via a signal interface. The resolver sensor is used to detect the rotational speed of the drive motor 30 controlled by the motor controller 50, and the motor controller 50 is used to receive signals from the resolver sensor.

[0087] The resolver sensor can accurately detect the position, direction and speed of the motor rotor, and is responsible for monitoring and extracting the rotational speed of the drive motor. It has a high sampling rate and is directly connected to the motor controller 50, with a short signal transmission time and higher stability.

[0088] In one embodiment, the motor controller 50 also acquires vehicle speed signals and lateral acceleration signals from the vehicle controller 20 or other sensors of the electric vehicle 10 via a signal interface. The vehicle speed signals are used to indicate the speed of the electric vehicle 10, and the lateral acceleration signals are used to indicate the lateral acceleration of the electric vehicle 10.

[0089] like Figure 4 As shown, in one embodiment, the electric vehicle 10 includes a drift button. When the drift button is off, the vehicle controller 20 controls the four wheel-end braking devices 110 to output braking force indicated by the brake pedal opening. When the drift button is on, the vehicle controller 20 controls the braking force output by the wheel-end braking devices 110 corresponding to the two rear wheels to be different from the braking force indicated by the brake pedal opening.

[0090] A drift button can be provided on the electric vehicle 10 for driver operation. For example, the drift button can be a physical button; pressing this physical button activates the assisted drift mode of the electric vehicle 10, thereby initiating assisted drift control when the motor controller 50 detects that the vehicle meets the conditions. Alternatively, the drift button can be a virtual button on the central control screen, which the driver can select to activate the assisted drift mode of the electric vehicle 10. Furthermore, the drift button can also be indirectly provided, for example, by incorporating it into a sport mode button or other function buttons. This application does not limit the method or form of setting the drift button.

[0091] Figure 5 This is a schematic diagram of the route taken by the electric vehicle 10 during drifting.

[0092] During the drift, the rear wheels of the electric vehicle 10 will lose or significantly reduce their grip on the road surface, resulting in a sideslip and the vehicle body will steer at a large sideslip angle.

[0093] The following describes the motor controller 50 provided in this application for assisting drift control of the electric vehicle 10.

[0094] like Figure 6 and Figure 7 As shown, during the driving of the electric vehicle 10, the motor controller 50 actively adjusts the torque output of the drive motor in response to the ratio of the lateral acceleration of the electric vehicle 10 to the speed of the electric vehicle 10 being greater than the drift threshold, based on the change in the wheel slip ratio.

[0095] The timing for assisted drift control can be determined by monitoring the lateral acceleration and speed of the electric vehicle 10. When the ratio of lateral acceleration to speed exceeds a drift threshold, the electric vehicle 10 is considered to be in a drift state, requiring assisted drift control. The drift threshold can be a given value, obtained through vehicle calibration or input by the driver. The motor controller 50 can acquire the vehicle speed and lateral acceleration of the electric vehicle 10 from the vehicle controller 20, or it can directly connect to the sensors of the electric vehicle 10 to acquire the vehicle speed and lateral acceleration directly from the sensors.

[0096] In one possible embodiment, the motor controller 50 sends the adjusted torque output of the drive motor 30 to the vehicle controller 20. That is, the motor controller 50 is used to send the front-wheel drive and rear-wheel drive operating states to the vehicle controller 20.

[0097] The motor controller 50 adjusts the torque output of the drive motor 30 based on the vehicle speed and the rotational speed of the drive motor 30 indicated by the resolver sensor of the electric vehicle 10. During the drifting process of the electric vehicle 10, due to the uneven road surface adhesion, the adhesion force on the tires fluctuates in real time. When the tire adhesion force changes, the tire slip ratio also changes. Correspondingly, the rotational speed and torque of the drive motor 30 used to drive the tires will change. Therefore, the change in road surface adhesion can be sensed and observed by the change in the rotor speed of the drive motor 30 detected by the resolver sensor. Thus, the motor controller 50 can adjust the actual output torque of the drive motor 30 based on the resolver signal of the drive motor 30, thereby precisely controlling the tire slip ratio, making the rear wheels tend to sideslip while ensuring the steering ability of the front wheels.

[0098] The resolver sensor can accurately detect the position, direction and speed of the rotor of the drive motor 30, and is responsible for monitoring and extracting the rotational speed of the drive motor 30. It has a high sampling rate and is directly connected to the motor controller 50, resulting in short signal transmission time and higher stability.

[0099] According to the solution of this application, the change in road surface adhesion coefficient is accurately determined by the resolver sensor signal of the drive motor 30, and the actual torque adjustment required is accurately calculated in the motor controller 50. The torque output is adjusted instantaneously to control the drift state of the electric vehicle. The motor controller 50 has a fast closed loop and a rapid response, which reduces the skill requirements of the driver for drifting operations and improves the driving experience and safety of the vehicle.

[0100] During the driving of the electric vehicle 10, the motor controller 50 controls the drive motor 30 to output the torque indicated by the opening of the accelerator pedal of the electric vehicle 10 in response to the ratio of the lateral acceleration of the electric vehicle 10 to the speed of the electric vehicle 10 being less than or equal to the drift threshold.

[0101] The motor controller 50 is used to actively control the drive motor 30 to adjust the torque output in response to the ratio of the lateral acceleration of the electric vehicle 10 to the speed of the electric vehicle 10 being greater than a drift threshold, so that the torque output by the drive motor 30 is different from the torque indicated by the opening of the accelerator pedal.

[0102] The motor controller 50 receives torque signals and drift function enable signals from the vehicle controller 20 via a signal interface. The torque signal indicates the torque indicated by the accelerator pedal, and the drift function enable signal indicates the activation of auxiliary drift control.

[0103] In one possible embodiment, the electric vehicle 10 includes a drift button. When the drift button is off, the motor controller 50 does not perform assisted drift control and controls the drive motor 30 to output the torque indicated by the accelerator pedal opening of the electric vehicle 10. When the drift button is on, the motor controller 50 enters assisted drift mode, detects the lateral acceleration and speed of the electric vehicle 10. When the ratio of the lateral acceleration to the speed is less than or equal to a drift threshold, the drive motor 30 is controlled to output the torque indicated by the accelerator pedal opening. When the motor controller 50 detects that the ratio of the lateral acceleration to the speed is greater than the drift threshold, the drive motor 30 is controlled to output an adjusted torque. At this time, the torque output by the drive motor 30 is different from the torque indicated by the accelerator pedal opening. That is, the actual torque output by the drive motor 30 is different from the torque indicated by the torque signal sent by the vehicle controller 20.

[0104] During the process of the motor controller 50 assisting in drifting the electric vehicle 10 to one side, i.e., when the motor controller 50 is in assisted drift control, the torque output by the drive motor 30 is different from the torque indicated by the accelerator pedal opening. The torque output by the drive motor 30 does not change with the change in the brake pedal opening.

[0105] In one possible embodiment, the electric vehicle 10 has multiple wheels, including front wheels and rear wheels. The electric vehicle 10 may be a rear-wheel drive vehicle, and includes a drive motor 30 for driving the rear wheels. The drive motor 30 drives the rear wheels of the electric vehicle. A motor controller 50 controls the drive motor 30 to reduce its output torque in response to a rear wheel slip ratio increasing to a value greater than an upper limit value. Conversely, it controls the drive motor 30 to increase its output torque in response to a rear wheel slip ratio decreasing to a value less than a lower limit value. The upper limit value is greater than the lower limit value.

[0106] The motor controller 50 adjusts the torque output of the drive motor 30 for driving the rear wheels based on the rear wheel slip ratio, which is indicated by the vehicle speed and the resolver sensor corresponding to the drive motor 30. Specifically, in response to the vehicle speed and the resolver sensor indicating that the rear wheel slip ratio increases to a value greater than the upper limit of the rear wheel slip ratio, the motor controller 50 controls the drive motor 30 to reduce its output torque. Conversely, in response to the vehicle speed and the resolver sensor indicating that the rear wheel slip ratio decreases to a value less than the lower limit of the rear wheel slip ratio, the motor controller 50 controls the drive motor 30 to increase its output torque.

[0107] The motor controller 50 obtains the rotational speed of the drive motor 30 through the resolver signal from the resolver sensor. The angular velocity of the wheels can be calculated using the rotational speed of the drive motor 30 and the transmission ratio of the electric vehicle 10. Therefore, by combining the wheel radius with the speed of the electric vehicle 10, the slip ratio of each wheel can be obtained. In this application, the slip ratio can be either the slip ratio or the rotational slip ratio.

[0108] The motor controller 50 can adjust the torque of the drive motor 30 used to drive the rear wheels according to the slip ratio of the rear wheels.

[0109] For the rear wheels, during drifting, it is desirable for the slip ratio of the rear axle wheels to be within the critical stability range, which is within the nonlinear range of the tire's friction limit circle, tending towards sideslip. Therefore, the upper and lower limits of the rear wheel slip ratio are the upper and lower limits, respectively. When the rear wheel slip ratio is higher than the upper limit, the motor controller 50 can control the drive motor used to drive the rear wheels to reduce torque output; when the rear wheel slip ratio is lower than the lower limit, the motor controller 50 can control the drive motor used to drive the rear wheels to increase torque output.

[0110] It should be understood that the rear-wheel drive control method described in the above embodiments can be applied to rear-wheel drive vehicles or four-wheel drive vehicles.

[0111] In one possible embodiment, the drive motor 30 is used to drive the front wheels of the electric vehicle. The motor controller 50 controls the drive motor 30 to reduce its output torque in response to an increase in the slip ratio of the front wheels exceeding an upper limit value. Conversely, the controller controls the drive motor 30 to increase its output torque in response to a decrease in the slip ratio of the front wheels exceeding a lower limit value. The upper limit value for the front wheels is greater than the lower limit value.

[0112] The motor controller 50 adjusts the torque output of the drive motor 30 for driving the front wheels based on the slip ratio of the front wheels, which is indicated by the vehicle speed and the resolver sensor corresponding to the drive motor 30. Specifically, in response to the vehicle speed and the resolver sensor indicating the front wheels increasing to a value greater than the upper limit of the front wheel slip ratio, the motor controller 50 controls the drive motor 30 to reduce its output torque. Conversely, in response to the vehicle speed and the resolver sensor indicating the front wheels decreasing to a value less than the lower limit of the front wheel slip ratio, the motor controller 50 controls the drive motor 30 to increase its output torque.

[0113] The motor controller 50 can adjust the torque of the drive motor 30 used to drive the front wheels according to the slip ratio of the front wheels.

[0114] For the front wheels, it's desirable for them to maintain traction during a drift. Since the front wheels are the steering wheels, if they lose traction first, a high slip ratio can lead to a loss of some or almost all of that traction, resulting in reduced or lost steering performance. With the same steering wheel angle, the actual turning angle produced by the vehicle is smaller than that produced with a lower slip ratio, leading to understeer.

[0115] Therefore, the upper and lower limits of the slip ratio corresponding to the front wheel are the upper limit and lower limit of the front wheel, respectively. When the slip ratio of the front wheel is higher than the upper limit of the front wheel, the motor controller 50 can control the drive motor 30 used to drive the front wheel to reduce the torque output. When the slip ratio of the front wheel is lower than the lower limit of the front wheel, the motor controller 50 can control the drive motor 30 used to drive the front wheel to increase the torque output.

[0116] In one possible embodiment, the upper limit value of the rear wheel is greater than the upper limit value of the front wheel, and the lower limit value of the rear wheel is greater than the lower limit value of the front wheel.

[0117] The slip ratio control target ranges for front and rear drive tires differ. The motor controller 50 controls the slip ratio of the front and rear drives within a set range by adjusting the torque output of the drive motor 30 to achieve the goal of assisted drifting. The slip ratio control target for the rear drive wheels is to cause the rear wheels to lose or partially lose traction, resulting in a fishtailing motion in the electric vehicle. The slip ratio control target for the front drive wheels is to maintain the steering ability of the front wheels. Therefore, the slip ratios of the front and rear drives are controlled separately.

[0118] It should be understood that front-wheel drive vehicles cannot use drifting methods that cause the rear wheels to lose some or all of their traction through driving. Therefore, the method of controlling the front-wheel drive in the above embodiments can be applied to four-wheel drive vehicles with both front-wheel drive and rear-wheel drive, and can be used in conjunction with the aforementioned motor controller 50 that controls the rear-wheel drive.

[0119] According to the scheme of this application, the motor controller 50 senses the road surface adhesion and realizes the adjustment of the actual output torque of the front and rear drives. The adjusted torque is quickly closed-looped within the motor controller 50. The front drive slip ratio control target and the rear drive control target are adapted respectively to ensure that the rear drive tends to sideslip and the front drive has steering ability, which is in the drift controllable zone, reducing the requirements for the driver and improving the drift safety boundary control capability.

[0120] For example, the specific execution process of slip ratio control by the motor controller 50 based on vehicle speed and the resolver signal from the resolver sensor is as follows:

[0121] First, the motor controller 50 obtains the angle θ that the drive motor rotates through in time t through the resolver signal of the resolver sensor, and calculates the speed n of the drive motor 30 using the following formula (1):

[0122]

[0123] Then, the angular velocity w of the wheel can be calculated by formula (2) using the rotational speed n of the drive motor 30 and the transmission ratio i of the electric vehicle 10:

[0124]

[0125] Next, the wheel slip ratio λ can be calculated using the wheel's angular velocity w, wheel radius r, and electric vehicle speed v.

[0126]

[0127] The upper and lower limits of the slip ratio for front-wheel drive control are λ. fc , λ ff The upper and lower limits of the slip ratio for rear-wheel drive control are λ and λ, respectively. rc , λ rf .

[0128] In the auxiliary drift control, the motor controller 50 monitors the slip ratio of the front and rear wheels respectively. When the slip ratio is lower than the target lower limit, it controls the drive motor 30 to increase the torque output. When the slip ratio is higher than the target upper limit, it controls the drive motor 30 to decrease the torque output.

[0129] In one possible embodiment, the opening of the accelerator pedal of the electric vehicle 10 is also used to indicate the upper limit value of the rear wheel, the lower limit value of the rear wheel, the upper limit value of the front wheel, and the lower limit value of the front wheel, which change with the opening of the accelerator pedal.

[0130] The motor controller 50 can receive the target range of front and rear drive slip ratio from the vehicle controller 20. The vehicle controller 20 detects the driver's controlled drift position and the accelerator pedal opening to calculate the target range of front and rear drive slip ratio, and then sends it to the motor controller 50.

[0131] The motor controller 50 can also directly obtain the front and rear drive slip ratio control target range from the accelerator pedal opening.

[0132] According to the scheme of this application, slip ratio control is performed on the front and rear wheels respectively, which improves the controllability and safety of the electric vehicle 10 during the drift process.

[0133] In one possible embodiment, the slip ratio control for the front and rear wheels can be a target slip ratio rather than a range. The slip ratio is precisely controlled by changing the torque of the drive motor 30 through closed-loop control in the motor controller 50. The motor controller 50 adjusts the torque output of the drive motor 30 to ensure that the slip ratios of multiple wheels reach their respective target slip ratios, which are indicated by the vehicle speed and the resolver sensor of the electric vehicle 10. The target slip ratios for the multiple wheels are indicated by the accelerator pedal opening of the electric vehicle 10, with the target slip ratio for the front wheels being less than that for the rear wheels.

[0134] According to the solution in this application, the motor controller senses changes in road surface adhesion and adjusts the front and rear drive slip ratio control targets accordingly to precisely control the tire slip ratio and reduce additional tire wear.

[0135] In one possible embodiment, the motor controller 50 is configured to adjust the torque output of the drive motor based on the vehicle speed and the rotational speed of the drive motor indicated by the resolver sensor of the electric vehicle when the opening of the accelerator pedal of the electric vehicle 10 is greater than the accelerator threshold and the steering wheel angle of the electric vehicle 10 is greater than the angle threshold, in response to the ratio of the lateral acceleration of the electric vehicle 10 to the vehicle speed of the electric vehicle 10 being greater than the drift threshold.

[0136] When the electric vehicle 10 is drifting, it is in an assisted drift mode, which can be activated by the driver. The motor controller 50 will only enter the assisted drift control when the electric vehicle 10 is in the assisted drift mode and the following conditions are met: the accelerator pedal opening is greater than the accelerator threshold, the steering wheel angle is greater than the angle threshold, and the ratio of the lateral acceleration to the vehicle speed of the electric vehicle 10 is greater than the drift threshold.

[0137] According to the solution in this application, the driver's operation is simplified during drifting cornering. The slip ratio is controlled by the motor controller, which makes it easier to achieve drifting operation of electric vehicles, lowers the operating threshold for drivers to drift, and improves the driving experience of the vehicle.

[0138] In one possible embodiment, the motor controller 50 is used to control the drive motor 30 to output the torque indicated by the accelerator pedal opening in response to the accelerator pedal opening being less than or equal to a throttle threshold or the steering wheel angle of the electric vehicle 10 being less than or equal to an angle threshold during the process of adjusting the torque output of the drive motor 30 according to the vehicle speed and the rotational speed of the drive motor 30 indicated by the resolver sensor of the electric vehicle 10.

[0139] During the drift of electric vehicle 10 to one side, the driver can also exit or end the drift early by operating the system. For example, the driver can end the drift by releasing the accelerator pedal, or by turning the steering wheel in the opposite direction or straightening it, or by pressing the brake pedal. Therefore, when the motor controller 50 detects that one or more of the following conditions are met: the accelerator pedal opening is less than or equal to the accelerator threshold, or the steering wheel angle of electric vehicle 10 is less than or equal to the angle threshold, the motor controller 50 can terminate the auxiliary drift control and re-respond to changes in the accelerator pedal opening to control the output torque of the drive motor 30.

[0140] Since the rear axle slip ratio of the electric vehicle 10 is in the critical stable range when it is sideslipping and drifting, releasing the accelerator or straightening the steering wheel can restore the vehicle's stable control.

[0141] According to the solution proposed in this application, the driver can flexibly control the end of the drift, which improves the safety of drifting, lowers the operational threshold for the driver to drift, and enhances the driving experience of the vehicle.

[0142] In one possible embodiment, the electric vehicle 10 is used to control the electric vehicle 10 to enter the drift mode by touching the central control screen of the electric vehicle 10 or activating the drift button. The motor controller 50 is used to actively adjust the torque output of the drive motor according to the change of the wheel slip ratio when the electric vehicle 10 is in the drift mode and the ratio of the lateral acceleration of the electric vehicle 10 to the speed of the electric vehicle is greater than the drift threshold.

[0143] When the electric vehicle 10 is drifting, it is in an assisted drift mode, which can be activated by the driver. The motor controller will only enter assisted drift control when the electric vehicle 10 is in assisted drift mode and the ratio of its speed to the drift threshold is greater than the specified conditions. Therefore, the motor controller 50 being in assisted drift mode does not necessarily mean that it is performing assisted drift control, but rather that the electric vehicle 10 must be in assisted drift mode.

[0144] This application provides a control method for assisting the drift mode of an electric vehicle 10.

[0145] This method can be applied to the electric vehicle 10 mentioned above.

[0146] The control method includes, during the operation of the electric vehicle 10, when the ratio of the lateral acceleration of the electric vehicle 10 to its speed is less than or equal to a drift threshold, the motor controller 50 controls the drive motor 30 to output torque indicated by the accelerator pedal opening of the electric vehicle 10. In response to the ratio of the lateral acceleration of the electric vehicle 10 to its speed being greater than the drift threshold, the drive motor 30 actively adjusts the magnitude of its output torque based on changes in wheel slip ratio; the torque output by the drive motor 30 differs from the torque indicated by the accelerator pedal opening.

[0147] The control method further includes a motor controller 50 that, in response to a rear wheel slip ratio increasing to a value greater than the rear wheel upper limit, controls the drive motor driving the rear wheels to reduce its output torque; in response to a rear wheel slip ratio decreasing to a value less than the rear wheel lower limit, controls the drive motor driving the rear wheels to increase its output torque; in response to a front wheel slip ratio increasing to a value greater than the front wheel upper limit, controls the drive motor driving the front wheels to reduce its output torque; and in response to a front wheel slip ratio decreasing to a value less than the front wheel lower limit, controls the drive motor driving the front wheels to increase its output torque. Wherein, the rear wheel upper limit is greater than the rear wheel lower limit, the front wheel upper limit is greater than the front wheel lower limit, the rear wheel upper limit is greater than the front wheel upper limit, and the rear wheel lower limit is greater than the front wheel lower limit.

[0148] The motor controller 50 controls the drive motor 30 to reduce its output torque in response to a vehicle speed and a rear wheel slip ratio (indicated by the resolver sensor corresponding to the drive motor 30 for driving the rear wheels) increasing to a value greater than the upper limit of the rear wheel slip ratio. Conversely, in response to a vehicle speed and a rear wheel slip ratio (indicated by the resolver sensor corresponding to the drive motor 30 for driving the rear wheels) decreasing to a value less than the lower limit of the rear wheel slip ratio, the motor controller 50 controls the drive motor 30 for driving the rear wheels to increase its output torque. Similarly, in response to a vehicle speed and a front wheel slip ratio (indicated by the resolver sensor corresponding to the drive motor 30 for driving the front wheels) increasing to a value greater than the upper limit of the front wheel slip ratio, the motor controller 50 controls the drive motor 30 for driving the front wheels to decrease its output torque. Conversely, in response to a vehicle speed and a front wheel slip ratio (indicated by the resolver sensor corresponding to the drive motor 30 for driving the front wheels) decreasing to a value less than the lower limit of the front wheel slip ratio, the motor controller 50 controls the drive motor 30 for driving the front wheels to increase its output torque.

[0149] In one embodiment, the control method includes the electric vehicle 10 controlling the electric vehicle to enter a drift mode by touching the central control screen of the electric vehicle or activating a drift button. During the operation of the electric vehicle 10, in response to the electric vehicle being in drift mode and the ratio of the electric vehicle's lateral acceleration to its speed being greater than a drift threshold, the motor controller 50 actively adjusts the torque output of the drive motor 30 according to changes in the wheel slip ratio.

[0150] In one embodiment, the control method specifically includes, during the process of actively adjusting the magnitude of the torque output by the drive motor 30 according to the change in wheel slip ratio, controlling the drive motor 30 to output the torque indicated by the accelerator pedal opening in response to the accelerator pedal opening being less than or equal to a throttle threshold or the steering wheel angle of the electric vehicle 10 being less than or equal to an angle threshold.

[0151] According to the solution of this application, the change in road surface adhesion coefficient is accurately determined by the resolver sensor signal of the drive motor, and the torque output is adjusted instantaneously to control the drift state of the electric vehicle. The control loop has low latency and fast response speed, which reduces the skill requirements of the driver for drift operation and improves the driving experience and safety of the vehicle.

[0152] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0153] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0154] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0155] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electric motor controller for assisting drift, characterized by, The motor controller is configured to control the drive motor to output a torque to drive a wheel of the electric vehicle, and the motor controller is configured to: in response to a ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than a drift threshold, actively adjust a magnitude of the torque output by the drive motor based on a change in slip ratio of the wheel during driving of the electric vehicle.

2. The motor controller of claim 1, wherein, The motor controller is configured to: in response to the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being less than or equal to the drift threshold, control the drive motor to output a torque indicated by an opening of an accelerator pedal of the electric vehicle during driving of the electric vehicle; in response to the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than the drift threshold, actively control the drive motor to adjust the torque output such that the torque output by the drive motor is different from the torque indicated by the opening of the accelerator pedal.

3. The motor controller of claim 1, wherein, The drive motor is configured to drive a rear wheel of the electric vehicle; The motor controller is configured to adjust the magnitude of the torque output by the drive motor, and the adjusting comprises: in response to the slip ratio of the rear wheel increasing to be greater than a rear wheel upper limit value, control the drive motor driving the rear wheel to decrease the output torque; in response to the slip ratio of the rear wheel decreasing to be less than a rear wheel lower limit value, control the drive motor driving the rear wheel to increase the output torque; wherein the rear wheel upper limit value is greater than the rear wheel lower limit value.

4. The motor controller of claim 3, wherein, The drive motor is configured to drive a front wheel of the electric vehicle; The motor controller is configured to adjust the magnitude of the torque output by the drive motor, and the adjusting comprises: in response to the slip ratio of the front wheel increasing to be greater than a front wheel upper limit value, control the drive motor driving the front wheel to decrease the output torque; in response to the slip ratio of the front wheel decreasing to be less than a front wheel lower limit value, control the drive motor driving the front wheel to increase the output torque; wherein the front wheel upper limit value is greater than the front wheel lower limit value.

5. The motor controller of claim 4, wherein, The rear wheel upper limit value is greater than the front wheel upper limit value, and the rear wheel lower limit value is greater than the front wheel lower limit value.

6. The motor controller of claim 4, wherein, The opening of the accelerator pedal of the electric vehicle is further configured to indicate the rear wheel upper limit value, the rear wheel lower limit value, the front wheel upper limit value and the front wheel lower limit value, and the rear wheel upper limit value, the rear wheel lower limit value, the front wheel upper limit value and the front wheel lower limit value vary with the opening of the accelerator pedal.

7. The motor controller of claim 1, wherein, The motor controller is configured to: in response to the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than a drift threshold, actively adjust a magnitude of the torque output by the drive motor based on a change in slip ratio of the wheel during driving of the electric vehicle when the opening of the accelerator pedal of the electric vehicle is greater than an accelerator threshold and a steering angle of a steering wheel of the electric vehicle is greater than an angle threshold.

8. The motor controller of claim 2, wherein, The motor controller is configured to: in response to the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than a drift threshold, actively adjust a magnitude of the torque output by the drive motor based on a change in slip ratio of the wheel during driving of the electric vehicle when the opening of the accelerator pedal of the electric vehicle is greater than an accelerator threshold and a steering angle of a steering wheel of the electric vehicle is greater than an angle threshold.

9. The motor controller of any one of claims 1-8, wherein, The electric vehicle is configured to enter a drift mode by touching a center control screen of the electric vehicle or activating a drift button, and the motor controller is configured to: During driving of the electric vehicle, in response to the electric vehicle being in the drift mode and a ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than a drift threshold, the motor controller is configured to actively adjust a magnitude of torque output by the drive motor according to a change in slip ratio of the wheels.

10. A control method for assisting drift of an electric vehicle, characterized by, The electric vehicle includes a motor controller, a drive motor, and a plurality of wheels, the motor controller is configured to control the drive motor to output torque to drive the wheels, and the control method includes: During driving of the electric vehicle, the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle is less than or equal to a drift threshold, and the motor controller is configured to control the drive motor to output torque indicated by an opening degree of an accelerator pedal of the electric vehicle; In response to the ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than the drift threshold, the motor controller is configured to actively adjust the magnitude of torque output by the drive motor according to a change in slip ratio of the wheels, the torque output by the drive motor being different from the torque indicated by the opening degree of the accelerator pedal.

11. The control method according to claim 10, characterized by, The plurality of wheels includes front wheels and rear wheels, the electric vehicle includes a drive motor for driving the front wheels and a drive motor for driving the rear wheels, and the control method further includes: The motor controller is configured to, in response to the slip ratio of the rear wheels increasing to be greater than a rear wheel upper limit value, control the drive motor for driving the rear wheels to decrease output torque; In response to the slip ratio of the rear wheels decreasing to be less than a rear wheel lower limit value, control the drive motor for driving the rear wheels to increase output torque; In response to the slip ratio of the front wheels increasing to be greater than a front wheel upper limit value, control the drive motor for driving the front wheels to decrease output torque; In response to the slip ratio of the front wheels decreasing to be less than a front wheel lower limit value, control the drive motor for driving the front wheels to increase output torque; wherein the rear wheel upper limit value is greater than the rear wheel lower limit value, the front wheel upper limit value is greater than the front wheel lower limit value, the rear wheel upper limit value is greater than the front wheel upper limit value, and the rear wheel lower limit value is greater than the front wheel lower limit value.

12. The control method according to claim 10, characterized by, The control method specifically includes: During the process in which the motor controller actively adjusts the magnitude of torque output by the drive motor according to the change in slip ratio of the wheels, in response to the opening degree of the accelerator pedal of the electric vehicle being less than or equal to an accelerator threshold or the steering angle of the steering wheel of the electric vehicle being less than or equal to an angle threshold, the motor controller is configured to control the drive motor to output torque indicated by the opening degree of the accelerator pedal.

13. The control method according to claim 10, characterized by, The control method includes: The electric vehicle is configured to enter a drift mode by touching a center control screen of the electric vehicle or activating a drift button; During the driving of the electric vehicle, in response to the electric vehicle being in a drift mode and a ratio of lateral acceleration of the electric vehicle to vehicle speed of the electric vehicle being greater than a drift threshold, the motor controller is configured to actively adjust a magnitude of torque output by the drive motor according to a change in the slip ratio of the wheel.

14. An electric vehicle, characterized by The electric vehicle includes the motor controller of any one of claims 1-9, a vehicle controller, an accelerator pedal, a brake pedal, and a steering wheel, the accelerator pedal being configured to indicate a torque output to a wheel of the electric vehicle, the brake pedal being configured to indicate a brake force output to a plurality of wheels of the electric vehicle.

15. The electric vehicle of claim 14, wherein, The vehicle controller is configured to send a torque signal to the motor controller, the torque signal being configured to indicate a torque indicated by an opening of the accelerator pedal of the electric vehicle. The vehicle controller is further configured to indicate to the motor controller a rear wheel upper limit value, a rear wheel lower limit value, a front wheel upper limit value, and a front wheel lower limit value indicated by the opening of the accelerator pedal of the electric vehicle.

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