Unit and method for controlling rear wheels to assist in vehicle drifting

Abstract

This application relates to a unit and method for controlling the rear wheels to assist vehicle drifting. The unit includes: a first determination module configured to determine whether the vehicle is performing a pre-drift maneuver; a second determination module configured to determine whether the vehicle is performing a first drift maneuver; a third determination module configured to determine whether the vehicle is performing a second drift maneuver; and a rear wheel control module configured to, when the first determination module determines that the vehicle is performing a pre-drift maneuver, control the steering angle of the rear wheels to deflect from zero degrees to a desired angle and lock the steering angle of the rear wheels at the desired angle; when the second determination module determines that the vehicle is performing a first drift maneuver, control the steering angle of the rear wheels to return to zero degrees; and when the third determination module determines that the vehicle is performing a second drift maneuver, continue to control the steering angle of the rear wheels to return to zero degrees and lock the steering angle of the rear wheels at zero degrees. The unit and method can efficiently identify the driver's drifting intention and assist the vehicle in performing a drift.

Description

Technical Field

[0001] This application relates to the field of vehicle rear-wheel steering technology, and more specifically, to units and methods for controlling the rear wheels to assist vehicle drifting. Background Technology

[0002] With the development of modern vehicle technology and the improvement of road conditions, the requirements for vehicle comfort, handling, and safety are becoming increasingly higher. To improve vehicle cornering agility, straight-line stability, and comfort, rear-wheel steering technology has been applied to vehicles. In other words, by utilizing rear-wheel steering technology, when the vehicle is turning at low speeds or experiencing understeer, the rear wheels steer in the opposite direction to the front wheels to reduce the turning radius. Conversely, when the vehicle is turning at high speeds and tends towards oversteer, especially when fishtailing, the rear wheels steer in the same direction as the front wheels to improve the stability of lane changes.

[0003] However, for drifting enthusiasts, steering the rear wheels in the same direction as the front wheels at high speeds helps prevent rear wheel slippage and instability, making drifting much more difficult. Clearly, the requirements for rear-wheel steering in assisting normal driving and assisting drifting are diametrically opposed. Current technological solutions involve placing buttons on the dashboard and / or switches on the vehicle's HMI (Human Machine Interface). Drivers can manually switch between normal driving and drift modes by pressing these buttons and / or touching these switches. In normal driving mode, the vehicle has rear-wheel steering, while in drift mode, it is completely disabled. This solution places a significant burden on the driver, as frequent switching of rear-wheel steering can cause sudden wobbling of the rear axle, resulting in uneven driving and distraction, posing a safety risk. Summary of the Invention

[0004] One object of this application is to provide a unit and method for controlling the rear wheels to assist vehicle drifting, which can efficiently identify the driver's drifting intention and assist the vehicle in drifting.

[0005] According to one aspect of this application, a unit for controlling the rear wheels to assist vehicle drifting is provided, comprising: a first determination module configured to determine, based on a first plurality of signals, whether the vehicle is performing a pre-drift maneuver, the pre-drift maneuver representing the front wheels rapidly turning along a first steering direction; a second determination module configured to, when the first determination module determines that the vehicle is performing a pre-drift maneuver, determine, based on a second plurality of signals, whether the vehicle is performing a first drift maneuver, the first drift maneuver representing the front wheels turning along a second steering direction opposite to the first steering direction and the rear wheels slipping; and a third determination module configured to, when the second determination module determines that the vehicle is performing a first drift maneuver, determine, based on a third plurality of signals, whether the vehicle is performing a first drift maneuver. The system includes a second drift maneuver, characterized by the front wheels turning along the first steering direction and the vehicle drifting; and a rear wheel control module configured to: when the first judgment module determines that the vehicle is performing a pre-drift maneuver, based on the steering angle of the front wheels rapidly turning along the first steering direction, control the steering angle of the rear wheels to deflect from zero degrees to a desired angle and lock the steering angle of the rear wheels at the desired angle; when the second judgment module determines that the vehicle is performing a first drift maneuver, control the steering angle of the rear wheels to return to zero degrees; and when the third judgment module determines that the vehicle is performing a second drift maneuver, continue to control the steering angle of the rear wheels to return to zero degrees and lock the steering angle of the rear wheels at zero degrees, or lock the steering angle of the rear wheels at zero degrees.

[0006] Optionally, the unit for controlling the rear wheels to assist vehicle drifting also includes a fourth judgment module, which is configured to determine whether the vehicle drift is in a stable state based on a fourth plurality of signals when the third judgment module determines that the vehicle is performing a second drift operation; and the rear wheel control module is further configured to continue to lock the steering angle of the rear wheels at zero degrees when the fourth judgment module determines that the vehicle drift is in a stable state.

[0007] Optionally, the rear wheel control module is further configured to perform one of the following: when the second judgment module determines that the vehicle is not performing the first drift, release the control of the steering angle of the rear wheels; when the third judgment module determines that the vehicle is not performing the second drift, release the control of the steering angle of the rear wheels; and when the fourth judgment module determines that the vehicle drift is not in a stable state, release the control of the steering angle of the rear wheels.

[0008] Optionally, the unit for controlling the rear wheels to assist vehicle drifting also includes a fifth judgment module, which is configured to determine whether the vehicle is performing a straightening action based on a fifth plurality of signals when the fourth judgment module determines that the vehicle drifting is in a stable state. The straightening action indicates that the steering angle of the front wheels has returned to zero degrees and the vehicle has stopped drifting. The rear wheel control module is also configured to release the control of the steering angle of the rear wheels when the fifth judgment module determines that the vehicle is performing a straightening action.

[0009] Optionally, the first plurality of signals include an average vehicle speed signal, a steering wheel angle signal, a steering wheel angle acceleration signal, a yaw rate signal, a yaw rate acceleration signal, a lateral speed signal, a lateral acceleration signal, and a longitudinal speed signal in the first plurality of cycles. The first determination module determines that the vehicle is performing a pre-drift maneuver by: confirming, based on the average vehicle speed signal in the first plurality of cycles, that the vehicle speed is within a first safe range suitable for vehicle drifting; confirming, based on the steering wheel angle signal and the steering wheel angle acceleration signal in the first plurality of cycles, that the steering wheel is rapidly rotating along a first rotation direction; confirming, based on the yaw rate signal and the yaw rate acceleration signal in the first plurality of cycles, that the vehicle's yaw angle is rapidly changing; and confirming, based on the lateral speed signal, the lateral acceleration signal, and the longitudinal speed signal in the first plurality of cycles, that the vehicle's center of gravity sideslip angle is rapidly changing.

[0010] Optionally, the second plurality of signals include an average vehicle speed signal, a steering wheel angle signal, an accelerator pedal depth signal, a brake pedal depth signal, and a longitudinal speed signal in the second plurality of cycles, and the second determination module determines that the vehicle is performing a first drift action by: confirming that the vehicle speed is within a second safe range suitable for vehicle drifting based on the average vehicle speed signal in the second plurality of cycles; confirming that the steering wheel is rotating in a second rotation direction opposite to the first rotation direction based on the steering wheel angle signal in the second plurality of cycles; and confirming that the vehicle is decelerating based on at least one of the accelerator pedal depth signal, the brake pedal depth signal, and the longitudinal speed signal in the second plurality of cycles.

[0011] Optionally, the third plurality of signals include steering wheel angle signal, yaw rate signal, yaw acceleration signal, lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the third plurality of cycles, and the third determination module determines that the vehicle is performing a second drift action by: confirming that the steering wheel is rotating along the first rotation direction based on the steering wheel angle signal in the third plurality of cycles; confirming that the yaw angle is gradually stabilizing based on the yaw rate signal and / or yaw acceleration signal in the third plurality of cycles; and confirming that the center of gravity sideslip angle is gradually stabilizing based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the third plurality of cycles.

[0012] Optionally, the fourth plurality of signals include a steering wheel angle signal, a yaw rate signal, a yaw acceleration signal, a lateral velocity signal, a lateral acceleration signal, and a longitudinal velocity signal in the fourth plurality of cycles, and the fourth determination module determines that the vehicle drift is in a stable state by: confirming that the steering wheel rotation angle remains stable based on the steering wheel angle signal in the fourth plurality of cycles; confirming that the vehicle's yaw angle remains stable based on the yaw rate signal and the yaw acceleration signal in the fourth plurality of cycles; and confirming that the vehicle's center of gravity sideslip angle remains stable based on the lateral velocity signal, the lateral acceleration signal, and the longitudinal velocity signal in the fourth plurality of cycles.

[0013] Optionally, the fifth plurality of signals include a steering wheel angle signal, a lateral velocity signal, a lateral acceleration signal, and a longitudinal velocity signal in the fifth plurality of cycles, and the fifth determination module determines that the vehicle is performing a return-to-center action by: confirming, based on the steering wheel angle signal in the fifth plurality of cycles, that the steering wheel rotation angle has returned to zero degrees or near it; and confirming, based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fifth plurality of cycles, that the center of gravity sideslip angle is gradually approaching zero degrees.

[0014] According to another aspect of this application, a method for controlling the rear wheels to assist vehicle drifting is provided, optionally executed by the aforementioned unit for controlling the rear wheels to assist vehicle drifting. The method includes: determining, based on a first plurality of signals, whether the vehicle is performing a pre-drift maneuver, the pre-drift maneuver indicating that the front wheels are rapidly turning along a first steering direction; when it is determined that the vehicle is performing a pre-drift maneuver, determining, based on a second plurality of signals, whether the vehicle is performing a first drift maneuver, the first drift maneuver indicating that the front wheels are turning along a second steering direction opposite to the first steering direction and that the rear wheels are slipping; when it is determined that the vehicle is performing a first drift maneuver, determining, based on a third plurality of signals, whether... The system determines whether the vehicle is performing a second drift, whereby the front wheels are turning along the first steering direction and the vehicle is drifting. When it is determined that the vehicle is performing a pre-drift maneuver, based on the steering angle of the front wheels turning rapidly along the first steering direction, the system controls the steering angle of the rear wheels to deflect from zero degrees to a desired angle and locks the steering angle of the rear wheels at the desired angle. When it is determined that the vehicle is performing a first drift, the system controls the steering angle of the rear wheels to return to zero degrees. When it is determined that the vehicle is performing a second drift, the system continues to control the steering angle of the rear wheels to return to zero degrees and locks the steering angle of the rear wheels at zero degrees, or locks the steering angle of the rear wheels at zero degrees.

[0015] The unit and method for controlling the rear wheels to assist vehicle drifting provided in this application can lock the steering angle of the rear wheels at a desired angle when the vehicle is performing a pre-drift maneuver, so that the vehicle automatically switches from normal driving mode to drift mode. During the first and second drift maneuvers, the steering angle of the rear wheels can be returned to zero degrees at a safe steering angular velocity, which helps the rear wheels to lose stability and slip more quickly, thus meeting the rear wheel steering requirements for assisting vehicle drifting. When the vehicle is performing the second drift maneuver and in a stable drift state, the steering angle of the rear wheels is locked at zero degrees, so that the vehicle drifts through corners with a stable sideslip angle and yaw rate. When the vehicle is straightening, the control of the rear wheel steering angle is released, so that the vehicle returns to normal driving mode. Furthermore, the unit and method for controlling the rear wheels to assist vehicle drifting provided in this application can release the control of the rear wheel steering angle when it is determined that the vehicle will not perform any further drift maneuvers or that the drift is not in a stable state, so as to exit drift mode at any time, thus simultaneously meeting the rear wheel steering requirements for assisting normal vehicle driving and assisting vehicle drifting. This can effectively reduce the frequency of manual operation by the driver and improve the safety and smoothness of vehicle operation.

[0016] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, illustrate embodiments of this application and, together with the specification, serve to explain the principles of this application.

[0018] Figure 1 This is a schematic diagram of the tire friction circle theory of a wheel.

[0019] Figure 2 This is a diagram illustrating a vehicle turning in normal driving mode.

[0020] Figure 3 This is a schematic diagram of a vehicle drifting process. The vehicle can achieve such a vehicle drifting process using a unit and method for controlling the rear wheels to assist vehicle drifting according to one embodiment of this application.

[0021] Figure 4 This is a schematic block diagram of a unit for controlling the rear wheels to assist vehicle drifting according to one embodiment of this application.

[0022] Figure 5 This is a flowchart of the judgment process of the first judgment module of a unit for controlling the rear wheels to assist vehicle drifting, according to one embodiment of this application.

[0023] Figure 6This is a flowchart of the judgment process of the second judgment module of a unit for controlling the rear wheels to assist vehicle drifting, according to one embodiment of this application.

[0024] Figure 7 This is a flowchart of the judgment process of the third judgment module of a unit for controlling the rear wheels to assist vehicle drifting, according to one embodiment of this application.

[0025] Figure 8 This is a flowchart of the judgment process of the fourth judgment module of a unit for controlling the rear wheels to assist vehicle drifting, according to one embodiment of this application.

[0026] Figure 9 This is a flowchart of the judgment process of the fifth judgment module of a unit for controlling the rear wheels to assist vehicle drifting, according to one embodiment of this application.

[0027] Figure 10 This is a flowchart of a method for controlling the rear wheels to assist vehicle drifting according to one embodiment of this application. Detailed Implementation

[0028] Various exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this application.

[0029] Techniques, devices, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, devices, and equipment should be considered part of the specification.

[0030] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary implementations may have different values.

[0031] Reference Figure 1 The grip force of a wheel and tire can generally be divided into lateral force and longitudinal force. Lateral force is used to evaluate the cornering ability of a wheel and tire, while longitudinal force is used to evaluate the braking or acceleration performance of a wheel and tire. When a vehicle is cornering, accelerating, or decelerating, the usable range of grip force is called the "friction circle." The size of the friction circle varies depending on the tire's contact patch load, road conditions, and tire performance. For example, when the tire's contact patch load decreases, the friction circle will also change from... Figure 1 The size indicated by the solid line is correspondingly reduced to as... Figure 1 The size is indicated by the dashed line.

[0032] like Figure 2As shown, when the vehicle 10 is expected to turn in normal driving mode, the steering wheel angle, the front wheel steering angle, and the direction of the vehicle's front end will all be consistent with the curvature of the curve 20 that the vehicle is turning through. Vehicles with rear-wheel steering can make the rear wheels turn in the opposite direction to the front wheels when turning at low speeds to reduce the turning radius, and make the rear wheels turn in the same direction as the front wheels when turning at high speeds to suppress lateral acceleration. This prevents the rear tires from becoming too saturated due to excessive lateral force, exceeding the friction circle boundary, which could lead to rear wheel instability and slippage, thus preventing the vehicle 10 from driving normally.

[0033] like Figure 3As shown, when the vehicle is expected to turn in drift mode, for example, when the vehicle is expected to turn in drift mode in the manner of "Scandi flick", the vehicle's drift process can be divided into several stages in chronological order. These stages include: pre-drift stage L0, first drift stage L1, second drift stage L2, stable drift stage L3, and straightening stage L4. In the pre-drift phase L0, the vehicle performs a pre-drift maneuver under the driver's control. Specifically, the driver rapidly applies a first torque to the steering wheel, causing it to rotate rapidly in the first direction of rotation. This causes the front wheels to turn rapidly in the first steering direction away from the center of the curve. The steering wheel's rotation angle in the first direction of rotation deviates only slightly from zero degrees. Immediately following, in the first drift phase L1, the vehicle performs a first drift maneuver under the driver's control. The driver applies a second torque to the steering wheel, causing it to rotate in the second direction of rotation, opposite to the first direction. This causes the front wheels to turn in the second steering direction towards the center of the curve. The steering wheel's rotation angle passes zero degrees and then deviates slightly from zero degrees along the second direction of rotation. Simultaneously, the driver reduces the vehicle's speed by releasing the accelerator pedal and / or deepening the brake pedal, resulting in a forward shift of the vehicle's center of gravity, a reduction in rear axle load, and a decrease in the contact load on the rear tires. Consequently, the friction radius of the rear tires decreases. The smaller the rear tires, the easier it is for them to reach saturation, leading to rear wheel slippage and vehicle fishtailing. Next, in the second drift phase L2, the vehicle performs a second drift maneuver under the driver's control. The driver applies a third torque to the steering wheel, causing it to turn in the first direction, thus steering the front wheels in the first direction, suppressing oversteer, and ensuring the vehicle's sideslip angle gradually stabilizes. The vehicle drifts, with the steering wheel again passing zero degrees and then shifting a certain angle relative to zero along the first direction of rotation. Next, in the stable drift phase L3, the vehicle is in a stable drift state under the driver's control. The driver holds the steering wheel still, maintaining a stable steering angle, and the vehicle drifts out of the corner with a stable posture. Finally, in the straightening phase L4, the vehicle performs a straightening maneuver under the driver's control. The driver applies a fourth torque to the steering wheel, returning the steering angle to zero degrees or near zero degrees, allowing the vehicle to travel normally in a straight line after drifting out of the corner.

[0034] This demonstrates that the requirements for rear-wheel steering in assisted vehicle driving and assisted vehicle drifting are diametrically opposed, especially in the second drift stage (L2) and the stable drift stage (L3). During these stages, the steering wheel angle and the front wheel steering angle will not match the curvature of the curve the vehicle is navigating, and the direction of the car's front end will be at a significant angle to the curve's curvature. For vehicles with rear-wheel steering, recognizing the driver's drifting intentions and assisting the vehicle in drifting to improve the intelligence of rear-wheel steering remains a challenge.

[0035] Reference Figure 4 According to one embodiment of this application, the unit 12 for controlling the rear wheels to assist vehicle drifting can be integrated into the RWS (Rear Wheel Steering) control ECU (Electronic Control Unit) as part of the RWS control ECU.

[0036] Unit 12 generally includes a first judgment module 14, a second judgment module 16, a third judgment module 18, and a rear wheel control module 26, which can communicate and operate simultaneously. The first judgment module 14, the second judgment module 16, and the third judgment module 18 can acquire relevant signals for identifying the driver's drift intention via, for example, the vehicle CAN bus. These signals include, but are not limited to, average vehicle speed signals, steering wheel angle signals, steering wheel angle acceleration signals, yaw rate signals, yaw rate acceleration signals, lateral speed signals, lateral acceleration signals, longitudinal speed signals, longitudinal acceleration signals, accelerator pedal depth signals, and brake pedal depth signals in each cycle. The relevant signals propagated in the vehicle CAN bus can originate from sensors installed on relevant components of the vehicle. For example, the average vehicle speed signal represents the average vehicle speed detection value U, which is calculated from the wheel speed detection values ​​detected by the wheel speed sensors associated with each wheel in each cycle. The steering wheel angle signal and the steering wheel angle acceleration signal respectively represent the steering wheel angle detection values ​​S detected by the steering wheel angle sensor associated with the steering wheel in each cycle. ang And the steering wheel angle acceleration detection value A ang The yaw rate signal and yaw acceleration signal respectively characterize the vehicle yaw rate detected by the yaw rate sensor associated with the vehicle chassis in each cycle. aw And vehicle yaw acceleration detection value A aw The lateral velocity signal and lateral acceleration signal respectively characterize the lateral velocity detection value V of the vehicle's center of gravity, which is directly acquired (e.g., a related signal from the IBS module propagated on the CAN bus) or indirectly calculated in each cycle. c The lateral acceleration detection value A of the vehicle's center of gravityc The longitudinal velocity signal and the longitudinal acceleration signal respectively represent the longitudinal velocity detection value V of the vehicle's center of gravity, which is directly acquired or indirectly calculated in each cycle. z The longitudinal acceleration value A of the vehicle's center of gravity z The accelerator pedal depth signal represents the accelerator pedal depth detected by the accelerator pedal position sensor associated with the vehicle's accelerator pedal in each cycle, and the brake pedal depth signal represents the brake pedal depth detected by the brake pedal position sensor associated with the vehicle's brake pedal in each cycle.

[0037] The first judgment module 14 is configured to determine whether the vehicle is performing a pre-drift maneuver based on a first plurality of signals. For example, the first plurality of signals may include the average vehicle speed signal, steering wheel angle signal, steering wheel angle acceleration signal, yaw rate signal, yaw acceleration signal, lateral speed signal, lateral acceleration signal, and longitudinal speed signal in the first plurality of cycles.

[0038] like Figure 5 As shown, the first judgment module 14 determines that the vehicle is performing a pre-drift maneuver by sequentially or simultaneously performing the following confirmations: confirming that the vehicle speed is within a first safe range suitable for vehicle drifting based on the average vehicle speed signal in the first plurality of cycles, for example, the average vehicle speed detection value U represented by the average vehicle speed signal is within the range [U1, U2]; and confirming that the steering wheel is continuously and rapidly rotating along the first rotation direction based on the steering wheel angle signal and the steering wheel angle acceleration signal in the first plurality of cycles, for example, the steering wheel angle detection value S represented by the steering wheel angle signal. ang Within the range [-S] where the angle changes slightly relative to zero degrees ang1 ,S ang1 Within, simultaneously, the steering wheel angular acceleration detection value A, characterized by the steering wheel angular acceleration signal, is... ang Within the range of larger accelerations [A] ang1 A ang2 [Within; based on the yaw rate and yaw acceleration signals in the first plurality of cycles, it is confirmed that the yaw angle is changing rapidly, for example, the vehicle yaw rate detection value Y characterized by the yaw rate signal.] aw Within the range of smaller yaw rate changes [-Y] aw1 ,Y aw1 Within this range, simultaneously, the vehicle yaw acceleration detection value A, characterized by the yaw acceleration signal, is... aw Within the range of larger accelerations [A] aw1 A aw2Within; and based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the first plurality of cycles, it is confirmed that the center of gravity sideslip angle δ is changing rapidly, for example, the center of gravity sideslip angle δ is within the range of small angle changes [-δ1, δ1], while the lateral acceleration detection value A of the vehicle's center of gravity characterized by the lateral acceleration signal is... c When the lateral acceleration of the vehicle's center of gravity exceeds the minimum limit, the vehicle will be more prone to instability.

[0039] Alternatively, the lateral velocity detection value V can be corrected using a Kalman filter algorithm. c This is used to calculate the centroid sideslip angle δ.

[0040] The Kalman filter algorithm includes a prediction model (1) and an update model (2).

[0041]

[0042]

[0043] First, using prediction model (1), where, This represents the lateral velocity detection value corrected by the Kalman filter algorithm in the previous cycle; V at P represents the detected lateral acceleration value in the current cycle. t-1 Q represents the covariance of the lateral velocity in the previous cycle; A and B are coefficient matrices, which can be calibrated, for example, through experience and real vehicle testing. Therefore, the average lateral velocity in the current cycle can be predicted using the prediction model (1). And the predicted lateral velocity covariance in the current cycle.

[0044] Then, the updated model (2) is used to correct the lateral velocity detection value in the current cycle, where R represents the covariance of the measurement error; K t Represents the Kalman gain coefficient; y t =CV t Where C = 1, V t This represents the detected lateral velocity value in the current cycle; I is the identity matrix. Therefore, the average wheel speed in the current cycle can be updated iteratively. The corrected lateral velocity detection value in the current cycle is used to take into account random errors and sensor measurement errors.

[0045] Therefore, the centroid sideslip angle in the current cycle can be expressed as:

[0046]

[0047] When all the above confirmations performed by the first judgment module 14 are "yes", the first judgment module 14 determines that the vehicle is performing a pre-drift maneuver. The rear wheel control module 26 is configured to, when determining that the vehicle is performing a pre-drift maneuver, control the steering angle of the rear wheels to shift from zero degrees to a desired angle based on the steering angle of the front wheels turning rapidly along the first steering direction, and lock the steering angle of the rear wheels at this desired angle. In other words, when the first judgment module 14 determines that the vehicle is performing a pre-drift maneuver, the rear wheel control module 26 switches the vehicle from normal driving mode to drift mode. Therefore, the desired angle can be based on the angle at which the rear wheels should turn with the front wheels in normal driving mode. Alternatively, the desired angle can be pre-set based on the vehicle's needs in drift mode, so that the vehicle's steering angle can return to zero degrees from the desired angle when the vehicle performs the first drift maneuver, to assist the vehicle in drifting, as will be described in detail below. Of course, in any case, the desired angle is very small, possibly even less than 1 degree.

[0048] In addition, if any of the above confirmations performed by the first judgment module 14 are negative, the first judgment module 14 determines that the vehicle has not performed a pre-drift action, and the vehicle continues to operate in normal driving mode.

[0049] The second judgment module 16 is configured to determine, based on a second plurality of signals, that the vehicle is performing a first drift action when the first judgment module 14 determines that the vehicle is performing a pre-drift action. For example, the second plurality of signals may include a steering wheel angle signal, an accelerator pedal depth signal, a brake pedal depth signal, and a longitudinal acceleration signal in a second plurality of cycles immediately following the first plurality of cycles.

[0050] like Figure 6 As shown, the second judgment module 16 determines that the vehicle is performing a first drift action by performing the following confirmations in sequence or simultaneously: confirming that the vehicle speed is within a second safe range suitable for vehicle drifting based on the average vehicle speed signal in the second plurality of cycles, for example, the average vehicle speed detection value U is within the range [U3, U4]; confirming that the steering wheel is continuously rotating along the second rotation direction based on the steering wheel angle signal in the second plurality of cycles, so as to offset a certain angle relative to zero degrees along the second rotation direction; confirming that the accelerator pedal is released based on the accelerator pedal depth signal, and / or confirming that the brake pedal is depressed based on the brake pedal depth signal, and / or confirming that the longitudinal acceleration of the vehicle is decreasing based on the longitudinal acceleration signal, that is, the vehicle is decelerating.

[0051] When all the above confirmations performed by the second judgment module 16 are "yes", the second judgment module 16 determines that the vehicle is performing a first drift, and the rear wheel control module 26 is configured to control the steering angle of the rear wheels to return to zero degrees according to a safe steering angle rate calibrated based on the actual vehicle when the second judgment module 16 determines that the vehicle is performing a first drift. Because the vehicle decelerates during the first drift, the vehicle's center of gravity shifts forward, the rear axle load decreases, and the ground contact load of the rear tires decreases. Consequently, the friction circle of the rear tires decreases, and the adhesion of the rear tires is more easily saturated. In this situation, by returning the steering angle of the rear wheels to zero degrees, the lateral force of the rear tires can be increased, causing the adhesion to reach saturation more quickly, and the rear wheels to slip and destabilize more rapidly. Furthermore, after the steering angle of the rear wheels returns to zero degrees, the steering angle can be locked at zero degrees to reduce the width of the rear of the vehicle when turning, preventing the vehicle from hitting objects such as guardrails during subsequent drifts.

[0052] In addition, if any of the above confirmations performed by the second judgment module 16 are negative, the second judgment module 16 determines that the vehicle is not performing the first drift action, and the rear wheel control module 26 will release the control of the steering angle of the rear wheels so that the vehicle returns to the normal driving mode to ensure the safety and smoothness of the vehicle driving.

[0053] The third judgment module 18 is configured to determine whether the vehicle is performing a second drift operation based on a third plurality of signals when the second judgment module 16 determines that the vehicle is performing a first drift operation. The third plurality of signals include a steering wheel angle signal, a yaw rate signal, a yaw acceleration signal, a lateral velocity signal, a lateral acceleration signal, and a longitudinal velocity signal in the third plurality of cycles immediately following the second plurality of cycles.

[0054] like Figure 7 As shown, the third judgment module 18 determines that the vehicle is performing a second drift operation by performing the following confirmations sequentially or simultaneously: confirming, based on the steering wheel angle signal in the third plurality of cycles, that the steering wheel is continuously rotating along the first rotation direction to deviate a certain angle relative to zero along the first rotation direction; and determining, based on the yaw rate signal and / or yaw acceleration signal in the third plurality of cycles, that the yaw angle is gradually stabilizing, for example, the yaw rate detection value Y in the current cycle of the third plurality of cycles. aw,t Compared to the yaw rate detection value Y in the previous cycle of the third or more cycles aw,t-1 rate of change (Y) aw,t -Y aw,t-1 ) / Y aw,t-1 Less than or equal to the first threshold ΔA, and / or the yaw acceleration detection value A in the third or more cycles. aw Within the range of smaller accelerations [0, A] aw3[Within; and based on the average vehicle speed signal, lateral velocity signal, and lateral acceleration signal in the third or more cycles, it is determined that the centroid sideslip angle gradually stabilizes, for example, the calculated centroid sideslip angle δ in the current cycle of the third or more cycles.] t Compared to the centroid sideslip angle δ in the previous cycle of the third or more cycles t-1 rate of change (δ) t -δ t-1 ) / δ t-1 Less than or equal to the second threshold ΔB, and / or the lateral acceleration detection value A in the third or more cycles. c Within the range of smaller accelerations [0, A] c1 ]Inside.

[0055] When all the above confirmations performed by the third judgment module 18 are "yes", the third judgment module 18 determines that the vehicle is performing a second drift, and the rear wheel control module 26 is configured to continue controlling the steering angle of the rear wheels to return to zero degrees and lock the steering angle of the rear wheels at zero degrees when the third judgment module 18 determines that the vehicle is performing a second drift. Alternatively, the steering angle of the rear wheels may have already returned to zero degrees when the vehicle is performing the first drift; in this case, the steering angle of the rear wheels is directly locked at zero degrees.

[0056] In addition, if any of the above confirmations performed by the third judgment module 18 are negative, the third judgment module 18 determines that the vehicle is not performing the second drift action, and the rear wheel control module 26 will release the control of the steering angle of the rear wheels so that the vehicle returns to the normal driving mode to ensure the safety and smoothness of the vehicle driving.

[0057] The fourth judgment module 22 is configured to determine whether the vehicle drift is in a stable state based on a fourth plurality of signals when the third judgment module 18 determines that the vehicle is performing a second drift operation. For example, the fourth plurality of signals may include steering wheel angle signal, yaw rate signal, yaw acceleration signal, lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fourth plurality of cycles immediately following the third plurality of cycles.

[0058] like Figure 8 As shown, the fourth judgment module 22 determines that the vehicle drift is in a stable state by performing the following confirmations sequentially or simultaneously: confirming that the steering wheel rotation angle remains relatively stable based on the steering wheel angle signal in the fourth multiple cycles, that is, the steering wheel rotation angle when the vehicle is in a stable drift state does not change or does not change too much compared to the steering angle when the vehicle is performing the second drift operation; and determining that the yaw angle remains stable based on the yaw rate signal and / or yaw acceleration signal in the fourth multiple cycles, for example, the yaw rate detection value Y in the current cycle of the fourth multiple cycles. aw,tCompared to the yaw rate detection value Y in the previous cycle of the fourth or more cycles aw,t-1 rate of change (Y) aw,t -Y aw,t-1 ) / Y aw,t-1 Less than or equal to the third threshold ΔC, and / or the yaw acceleration detection value A in the fourth or more cycles. aw Within the range of smaller accelerations [0, A] aw4 [Within; and based on the average vehicle speed signal, lateral velocity signal, and lateral acceleration signal in the fourth or more cycles, it is determined that the centroid sideslip angle remains stable, for example, the calculated centroid sideslip angle δ in the current cycle of the fourth or more cycles.] t Compared to the centroid sideslip angle δ in the previous cycle of the fourth or more cycles t-1 rate of change (δ) t -δ t-1 ) / δ t-1 Less than or equal to the fourth threshold ΔD, and / or the lateral acceleration detection value A in the fourth or more cycles. c Within the range of smaller accelerations [0, A] a2 ]Inside.

[0059] When all the above confirmations performed by the fourth judgment module 22 are true, the fourth judgment module 22 determines that the vehicle drift is in a stable state, and the rear wheel control module 26 is also configured to continue to lock the steering angle of the rear wheels at zero degrees when the fourth judgment module 22 determines that the vehicle drift is in a stable state.

[0060] In addition, if any of the above confirmations performed by the fourth judgment module 22 are negative, the fourth judgment module 22 determines that the vehicle drift is not in a stable state. If the vehicle drift is unsafe, the rear wheel control module 26 will release the control of the steering angle of the rear wheels so that the vehicle returns to the normal driving mode to assist the vehicle in safe operations such as steering and obstacle avoidance.

[0061] The fifth judgment module 24 is configured to determine whether the vehicle is performing a straightening action based on a fifth plurality of signals when the fourth judgment module 22 determines that the vehicle drift is in a stable state. For example, the fifth plurality of signals include the steering wheel angle signal, lateral speed signal, lateral acceleration signal, and longitudinal speed signal in the fifth plurality of cycles immediately following the fourth plurality of cycles.

[0062] like Figure 9As shown, the fifth judgment module 24 determines that the vehicle is performing a straightening action by sequentially or simultaneously performing the following confirmations: confirming that the steering wheel rotation angle has returned to zero degrees or near zero degrees based on the steering wheel angle signal in the fifth plurality of cycles; and confirming that the center of gravity sideslip angle is gradually approaching zero degrees based on the average vehicle speed signal, lateral speed signal, and lateral acceleration signal in the fifth plurality of cycles, for example, the calculated center of gravity sideslip angle δ in the fifth plurality of cycles. t Gradually approaching zero degrees, and the lateral acceleration detection value A in the fifth or more cycles. c It gradually approaches zero.

[0063] When all the above confirmations executed by the fifth judgment module 24 are true, the fifth judgment module 24 determines that the vehicle is performing a straightening action, that is, the direction of the vehicle's front, the direction of the front wheels, and the direction of the vehicle's travel gradually become aligned on the same straight line. Furthermore, the rear wheel control module 26 is also configured to release the control of the steering angle of the rear wheels when the fifth judgment module 24 determines that the vehicle is performing a straightening action, so that the vehicle returns to the normal driving mode to ensure the safety and smoothness of the vehicle's driving.

[0064] It is understandable that all the above-mentioned limits, ranges, thresholds, cycle durations and frequencies can be calibrated through real vehicle testing. For example, the range of the average vehicle speed detection value U can be selected from medium to high vehicle speeds of 70km / h to 150km / h.

[0065] Reference Figure 10 The method for controlling the rear wheels to assist vehicle drifting accordingly includes the following steps:

[0066] S1. Based on the first multiple signals in the first multiple cycles, determine whether the vehicle is performing a pre-drift action, the pre-drift action being characterized by the front wheels rapidly turning along the first steering direction;

[0067] S2. When it is determined that the vehicle is performing a pre-drift action, based on the second multiple signals in the second multiple cycles, it is determined whether the vehicle is performing a first drift action. The first drift action indicates that the front wheels are turning in a second steering direction opposite to the first steering direction and the rear wheels are slipping.

[0068] S3. When it is determined that the vehicle is performing a first drift, based on the third signal in the third multiple cycle, it is determined whether the vehicle is performing a second drift, whereby the second drift indicates that the front wheels are turning along the first steering direction and the vehicle is drifting; and

[0069] S4. When it is determined that the vehicle is performing a pre-drift maneuver, based on the steering angle of the front wheels turning rapidly along the first steering direction, control the steering angle of the rear wheels to deflect from zero degrees to the desired angle and lock the steering angle of the rear wheels at the desired angle.

[0070] S5. When it is determined that the vehicle is performing its first drift maneuver, control the steering angle of the rear wheels to return to zero degrees; and

[0071] S6. When it is determined that the vehicle is performing a second drift, continue to control the steering angle of the rear wheels to return to zero degrees and lock the steering angle of the rear wheels at zero degrees, or lock the steering angle of the rear wheels at zero degrees.

[0072] The method for controlling the rear wheels to assist vehicle drifting provided in this application is intended to be performed using a unit for controlling the rear wheels to assist vehicle drifting. Therefore, the features of the unit and the features of the method described herein can correspond to, combine, and be interchanged with each other.

[0073] Furthermore, the RWS control ECU and each sensor described above each actually include a memory and a processor. On one hand, the memory can store various executable instructions and their parameters. The memory can include electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples of memory include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusion structures storing instructions thereon, and any suitable combination thereof. On the other hand, when the executable instructions and their parameters are executed by the processor, means are created to implement the steps described in the specification and the functions / operations specified in one or more boxes in the flowcharts and / or block diagrams in the accompanying drawings.

[0074] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of control units, control methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based unit that performs the specified function or action, or using a combination of dedicated hardware and computer instructions. It will be well known to those skilled in the art that implementation in hardware, implementation in software, and implementation using a combination of software and hardware are equivalent.

[0075] While some specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A unit (12) for controlling the rear wheels to assist vehicle drifting, characterized in that, include: The first judgment module (14) is configured to determine whether the vehicle is performing a pre-drift action based on a first plurality of signals. The pre-drift action indicates that the front wheels are turning rapidly along the first steering direction. The second judgment module (16) is configured to determine whether the vehicle is performing a first drift action based on a second plurality of signals when the first judgment module (14) determines that the vehicle is performing a pre-drift action. The first drift action indicates that the front wheels are turning in a second steering direction opposite to the first steering direction and the rear wheels are slipping. The third judgment module (18) is configured to determine whether the vehicle is performing a second drift operation based on a third plurality of signals when the second judgment module (16) determines that the vehicle is performing a first drift operation. The second drift operation indicates that the front wheels are turning along the first steering direction and the vehicle is drifting. as well as The rear wheel control module (26) is configured as follows: When the first judgment module (14) judges that the vehicle is performing a pre-drift action, based on the steering angle of the front wheel turning quickly along the first steering direction, it controls the steering angle of the rear wheel to shift from zero degrees to the desired angle and locks the steering angle of the rear wheel at the desired angle. When the second judgment module (16) determines that the vehicle is performing the first drifting action, it controls the steering angle of the rear wheels to return to zero degrees; as well as When the third judgment module (18) determines that the vehicle is performing the second drifting action, it continues to control the steering angle of the rear wheel to return to zero degrees and locks the steering angle of the rear wheel at zero degrees, or locks the steering angle of the rear wheel at zero degrees.

2. The unit (12) for controlling the rear wheels to assist vehicle drifting according to claim 1, characterized in that, It also includes a fourth judgment module (22), which is configured to determine whether the vehicle drift is in a stable state based on a fourth set of signals when the third judgment module (18) determines that the vehicle is performing a second drift operation. and The rear wheel control module (26) is also configured to continue locking the steering angle of the rear wheels at zero degrees when the fourth judgment module (22) determines that the vehicle drift is in a stable state.

3. The unit (12) for controlling the rear wheels to assist vehicle drifting according to claim 2, characterized in that, The rear wheel control module (26) is also configured to perform one of the following: When the second judgment module (16) determines that the vehicle is not performing the first drifting action, the control of the steering angle of the rear wheels is released; When the third judgment module (18) determines that the vehicle is not performing the second drifting action, the control of the steering angle of the rear wheels is released; as well as When the fourth judgment module (22) determines that the vehicle is not in a stable state due to drift, it releases the control of the steering angle of the rear wheels.

4. The unit (12) for controlling the rear wheels to assist vehicle drifting according to claim 3, characterized in that, It also includes a fifth judgment module (24), which is configured to, when the fourth judgment module (22) determines that the vehicle is in a stable state of drifting, determine whether the vehicle is performing a straightening action based on the fifth multiple signals. The straightening action indicates that the steering angle of the front wheels has returned to zero degrees and the vehicle has stopped drifting; and The rear wheel control module (26) is also configured to release the control of the steering angle of the rear wheels when the fifth judgment module (24) determines that the vehicle is performing a return-to-center action.

5. The unit (12) for controlling the rear wheels to assist vehicle drifting according to any one of claims 1 to 4, characterized in that, The first plurality of signals include an average vehicle speed signal, a steering wheel angle signal, a steering wheel angle acceleration signal, a yaw rate signal, a yaw rate acceleration signal, a lateral speed signal, a lateral acceleration signal, and a longitudinal speed signal in the first plurality of cycles, and the first judgment module (14) determines that the vehicle is performing a pre-drift action by: confirming that the vehicle speed is within a first safe range suitable for vehicle drifting based on the average vehicle speed signal in the first plurality of cycles; confirming that the steering wheel is rapidly rotating along a first rotation direction based on the steering wheel angle signal and the steering wheel angle acceleration signal in the first plurality of cycles; confirming that the yaw rate of the vehicle is rapidly changing based on the yaw rate signal and the yaw rate acceleration signal in the first plurality of cycles; and confirming that the center of gravity sideslip angle of the vehicle is rapidly changing based on the lateral speed signal, the lateral acceleration signal, and the longitudinal speed signal in the first plurality of cycles.

6. The unit (12) for controlling the rear wheels to assist vehicle drifting according to any one of claims 1 to 4, characterized in that, The second plurality of signals include an average vehicle speed signal, a steering wheel angle signal, an accelerator pedal depth signal, a brake pedal depth signal, and a longitudinal speed signal in the second plurality of cycles, and the second determination module (16) determines that the vehicle is performing a first drift action by: confirming that the vehicle speed is within a second safe range suitable for vehicle drifting based on the average vehicle speed signal in the second plurality of cycles; confirming that the steering wheel is rotating in a second rotation direction opposite to the first rotation direction based on the steering wheel angle signal in the second plurality of cycles; and confirming that the vehicle is decelerating based on at least one of the accelerator pedal depth signal, the brake pedal depth signal, and the longitudinal speed signal in the second plurality of cycles.

7. The unit (12) for controlling the rear wheels to assist vehicle drifting according to any one of claims 1 to 4, characterized in that, The third plurality of signals include the steering wheel angle signal, yaw rate signal, yaw acceleration signal, lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the third plurality of cycles, and the third judgment module (18) determines that the vehicle is performing a second drift action by: confirming that the steering wheel is rotating along the first rotation direction based on the steering wheel angle signal in the third plurality of cycles; confirming that the yaw angle is gradually stabilizing based on the yaw rate signal and / or yaw acceleration signal in the third plurality of cycles; and confirming that the center of gravity sideslip angle is gradually stabilizing based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the third plurality of cycles.

8. The unit (12) for controlling the rear wheels to assist vehicle drifting according to any one of claims 2 to 4, characterized in that, The fourth plurality of signals include the steering wheel angle signal, yaw rate signal, yaw acceleration signal, lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fourth plurality of cycles, and the fourth judgment module (22) judges that the vehicle drift is in a stable state by: confirming that the steering wheel rotation angle remains stable based on the steering wheel angle signal in the fourth plurality of cycles; confirming that the vehicle yaw angle remains stable based on the yaw rate signal and yaw acceleration signal in the fourth plurality of cycles; and confirming that the vehicle's center of gravity sideslip angle remains stable based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fourth plurality of cycles.

9. The unit (12) for controlling the rear wheels to assist vehicle drifting according to claim 4, characterized in that, The fifth plurality of signals include the steering wheel angle signal, lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fifth plurality of cycles, and the fifth judgment module (24) judges that the vehicle is performing a return-to-center action by: confirming that the steering wheel rotation angle returns to zero degrees or near it based on the steering wheel angle signal in the fifth plurality of cycles; and confirming that the center of gravity sideslip angle gradually approaches zero degrees based on the lateral velocity signal, lateral acceleration signal, and longitudinal velocity signal in the fifth plurality of cycles.

10. A method for controlling the rear wheels to assist vehicle drifting, optionally performed by the unit (12) for controlling the rear wheels to assist vehicle drifting according to any one of claims 1-9, characterized in that, The method includes: Based on the first multiple signals, it is determined whether the vehicle is performing a pre-drift action. The pre-drift action indicates that the front wheels are turning rapidly along the first steering direction. When it is determined that the vehicle is performing a pre-drift action, based on the second multiple signals, it is determined whether the vehicle is performing a first drift action. The first drift action indicates that the front wheels are turning in a second steering direction opposite to the first steering direction and the rear wheels are slipping. When it is determined that the vehicle is performing a first drift, based on a third set of signals, it is determined whether the vehicle is performing a second drift. The second drift indicates that the front wheels are turning in the first steering direction and the vehicle is drifting; and When it is determined that the vehicle is performing a pre-drift maneuver, based on the steering angle of the front wheels as they turn rapidly along the first steering direction, the steering angle of the rear wheels is controlled to deflect from zero degrees to the desired angle and locked at the desired angle. When it is determined that the vehicle is performing its first drift maneuver, the steering angle of the rear wheels is returned to zero degrees; and When it is determined that the vehicle is performing a second drift, continue to control the steering angle of the rear wheels to return to zero degrees and lock the steering angle of the rear wheels at zero degrees, or lock the steering angle of the rear wheels at zero degrees.

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