4wis mode controller based on road adhesion coefficient and speed

Abstract

The application discloses a 4WIS mode controller based on a road adhesion coefficient and speed, and the method is based on a road adhesion coefficient and a longitudinal vehicle speed in the aspect of trajectory tracking control of a four-wheel independent steering vehicle, three self-adaptive steering modes of high adhesion low speed, high adhesion high speed and low adhesion steady running are designed, and the optimization matching of steering characteristics under different working conditions is realized.

Description

Technical Field

[0001] This invention relates to the field of intelligent driving, and more particularly to a 4WIS mode controller based on road surface adhesion coefficient and speed. Background Technology

[0002] The road surface adhesion coefficient, as the mechanical transmission link between the vehicle and the road, directly affects the amplitude boundary of tire forces and dynamic response characteristics. Under different road surface conditions, the saturation characteristics of tire lateral and longitudinal forces change significantly, thereby altering the vehicle's steady-state response and transient characteristics. Especially on low-adhesion surfaces such as ice, snow, and wet surfaces, the tire's linear working zone shrinks sharply, making the vehicle highly susceptible to dangerous conditions such as center of gravity sideslip angle divergence, yaw instability, and even skidding due to lateral force saturation. Traditional vehicle dynamics control systems are mostly designed based on a single fixed operating condition assumption, making it difficult to balance control quality under different adhesion conditions across the entire operating range. Therefore, conducting research on vehicle dynamics control based on the road surface adhesion coefficient has significant theoretical and engineering value for improving the active safety performance of vehicles in complex driving environments. Summary of the Invention

[0003] The purpose of this invention is to address the inherent limitations of traditional front-wheel steering systems, which are constrained by the mechanical transmission link and Ackermann steering geometry. These limitations include a large low-speed turning radius and limited ability to maneuver in narrow spaces. Furthermore, traditional systems cannot achieve real-time identification of the four-wheel road surface adhesion coefficient and dynamic adaptation of steering strategies. Under extreme conditions of low-adhesion and variable-adhesion road surfaces, they are prone to steering characteristic mismatch or even sideslip and loss of control, failing to meet the core requirements of stable driving and precise trajectory tracking in all scenarios for intelligent vehicles. Based on the road surface adhesion coefficient and longitudinal vehicle speed, three adaptive steering modes are designed. In high-adhesion, low-speed conditions, front and rear wheel counter-phase steering is used, placing the instantaneous steering center between the front and rear axles, effectively reducing the turning radius and improving vehicle maneuverability. In high-adhesion, high-speed conditions, front and rear wheel in-phase steering is used, placing the instantaneous steering center behind the rear axle, reducing yaw rate and sideslip angle, and enhancing high-speed lane-changing stability. In low-adhesion conditions, a stable driving mode combining front-wheel steering and rear-wheel toe-in is used, generating symmetrical lateral constraints through rear wheel toe-in to delay rear axle lateral force saturation. This mode switching strategy lays the kinematic foundation for trajectory tracking and stability control under all operating conditions.

[0004] The present invention solves the above-mentioned technical problems through the following technical means:

[0005] The 4WIS mode controller based on road surface adhesion coefficient and speed is characterized in that: the method takes the Ackermann pure rolling criterion as the core control basis, and combines the road surface adhesion conditions and vehicle driving conditions to match differentiated steering control logic, thereby deriving three core steering modes: high adhesion low speed 4WIS mode, high adhesion high speed 4WIS mode, and low adhesion stable driving 4WIS mode.

[0006] The high-traction low-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to low-speed driving conditions on high-traction surfaces. In this mode, the front and rear wheels deflect in opposite directions (when turning left). >0、 <0, when turning right <0、 >0), ICR is located within the longitudinal range between the front and rear axles of the vehicle. By matching the opposite steering angles of the front and rear wheels, the turning radius of the vehicle can be significantly reduced, and zero-radius turning on the spot can be achieved under extreme conditions. This significantly improves the vehicle's maneuverability in scenarios such as parking in tight spaces and turning on narrow roads. At the same time, it strictly follows the Ackermann pure rolling principle to eliminate tire lateral slippage from a geometric perspective and reduce tire wear.

[0007] The high-adhesion, high-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to high-speed driving conditions on high-adhesion surfaces. In this mode, the front and rear wheels deflect in the same direction (when turning left). , When turning right , Furthermore, the rear wheel steering angle amplitude is always smaller than the front wheel steering angle, and the ICR is located outside the longitudinal range behind the rear axle of the vehicle. By matching the steering angles of the front and rear wheels in the same direction, the yaw rate and body slip angle during vehicle steering can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved. At the same time, the Ackermann pure rolling principle is always met to avoid abnormal tire wear.

[0008] The low-traction stable driving 4WIS mode is the core steering mode for 4WIS vehicles to adapt to low-traction road conditions. In this mode, the ICR is determined by the front wheel steering angle and the ICR is located on the extension line of the rear axle of the vehicle. That is, the front wheel steering angle conforms to the front wheel Ackerman steering mode, while the rear wheel steering angle is determined by the rear wheel toe angle. , By matching the front wheel steering with the rear wheel toe-in, the vehicle's yaw rate and body slip angle can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved.

[0009] This technical solution has the following advantages:

[0010] 1. By independently controlling the steering angle of each wheel, the spatial position of the instantaneous steering center can be flexibly adjusted according to driving conditions, thereby optimizing the vehicle's steering maneuverability and yaw response characteristics;

[0011] 2. Under low-speed conditions, using front and rear wheel counter-phase steering can significantly reduce the turning radius and improve the ability to pass through narrow spaces;

[0012] 3. Under high-speed conditions, the use of front and rear wheel same-phase steering can effectively suppress the sideslip angle and yaw rate of the center of gravity, and enhance the handling stability when changing lanes and avoiding obstacles.

[0013] 4. Under low-adhesion conditions, the active adjustment of the rear wheel toe angle can delay the saturation process of the rear axle lateral force and maintain the vehicle's understeer characteristics. Attached Figure Description

[0014] Figure 1 This is a four-wheel steering mode distribution diagram of the 4WIS mode controller based on road surface adhesion coefficient and speed according to the present invention.

[0015] Figure 2 This is a schematic diagram of the high-adhesion, low-speed 4WIS mode of the 4WIS mode controller based on road surface adhesion coefficient and speed of the present invention.

[0016] Figure 3 This is a schematic diagram of the high-adhesion, high-speed 4WIS mode of the 4WIS mode controller based on road surface adhesion coefficient and speed of the present invention.

[0017] Figure 4 This is a schematic diagram of the low-adhesion stable driving 4WIS mode of the 4WIS mode controller based on road surface adhesion coefficient and speed of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0019] like Figure 1 As shown, the present invention is a 4WIS mode controller based on road surface adhesion coefficient and speed. The method is characterized by taking the Ackermann pure rolling criterion as the core control basis and combining road surface adhesion conditions with vehicle driving conditions to match differentiated steering control logic, thereby deriving three core steering modes: high adhesion low speed 4WIS mode (front and rear wheels reverse phase steering), high adhesion high speed 4WIS mode (front and rear wheels in the same phase steering), and low adhesion stable driving 4WIS mode (front wheel steering and rear wheel toe-in).

[0020] like Figure 2 As shown, the high-traction low-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to low-speed driving conditions on high-traction surfaces. In this mode, the front and rear wheels deflect in opposite directions (when turning left). >0、 <0, when turning right <0、 >0), ICR is located within the longitudinal range between the front and rear axles of the vehicle. By matching the opposite steering angles of the front and rear wheels, the turning radius of the vehicle can be significantly reduced, and zero-radius turning on the spot can be achieved under extreme conditions. This significantly improves the vehicle's maneuverability in scenarios such as parking in tight spaces and turning on narrow roads. At the same time, it strictly follows the Ackermann pure rolling principle to eliminate tire lateral slippage from a geometric perspective and reduce tire wear.

[0021] like Figure 3 As shown, the high-adhesion, high-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to high-speed driving conditions on high-adhesion surfaces. In this mode, the front and rear wheels deflect in the same direction (when turning left). , When turning right , Furthermore, the rear wheel steering angle amplitude is always smaller than the front wheel steering angle, and the ICR is located outside the longitudinal range behind the rear axle of the vehicle. By matching the steering angles of the front and rear wheels in the same direction, the yaw rate and body slip angle during vehicle steering can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved. At the same time, the Ackermann pure rolling principle is always met to avoid abnormal tire wear.

[0022] like Figure 4 As shown, the 4WIS low-traction stable driving mode is the core steering mode for 4WIS vehicles to adapt to low-traction road conditions. In this mode, the ICR is determined by the front wheel steering angle and the ICR is located on the extension line of the rear axle of the vehicle. That is, the front wheel steering angle conforms to the front wheel Ackerman steering mode, while the rear wheel steering angle is determined by the rear wheel toe angle. , By matching the front wheel steering with the rear wheel toe-in, the vehicle's yaw rate and body slip angle can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved.

Claims

1. A 4WIS mode controller based on road surface adhesion coefficient and speed, characterized in that: The method is based on the Ackermann pure rolling criterion as the core control basis, and combines road surface adhesion conditions with vehicle driving conditions to match differentiated steering control logic, resulting in three core steering modes: high adhesion low speed 4WIS mode (front and rear wheels reverse phase steering), high adhesion high speed 4WIS mode (front and rear wheels in the same phase steering), and low adhesion stable driving 4WIS mode (front wheel steering and rear wheel toe-in).

2. The 4WIS mode controller based on road surface adhesion coefficient and speed according to claim 1, characterized in that: The high-traction low-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to low-speed driving conditions on high-traction surfaces. In this mode, the front and rear wheels deflect in opposite directions (when turning left). >0、 <0, when turning right <0、 >0), the instantaneous center of rotation (ICR) is located within the longitudinal range between the front and rear axles of the vehicle. By matching the opposite steering angles of the front and rear wheels, the turning radius of the vehicle can be significantly reduced, and zero-radius turning on the spot can be achieved under extreme conditions. This significantly improves the vehicle's maneuverability in scenarios such as parking in tight spaces and turning on narrow roads. At the same time, it strictly follows the Ackermann pure rolling principle, eliminating tire lateral slippage from a geometric perspective and reducing tire wear.

3. The 4WIS mode controller based on road surface adhesion coefficient and speed according to claim 1, characterized in that: The high-adhesion, high-speed 4WIS mode is the core steering mode for 4WIS vehicles to adapt to high-speed driving conditions on high-adhesion surfaces. In this mode, the front and rear wheels deflect in the same direction (when turning left). , When turning right , Furthermore, the rear wheel steering angle amplitude is always smaller than the front wheel steering angle, and the ICR is located outside the longitudinal range behind the rear axle of the vehicle. By matching the steering angles of the front and rear wheels in the same direction, the yaw rate and body slip angle during vehicle steering can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved. At the same time, the Ackermann pure rolling principle is always met to avoid abnormal tire wear.

4. The 4WIS mode controller based on road surface adhesion coefficient and speed according to claim 1, characterized in that: The low-traction stable driving 4WIS mode is the core steering mode for 4WIS vehicles to adapt to low-traction road conditions. In this mode, the ICR is determined by the front wheel steering angle and the ICR is located on the extension line of the rear axle of the vehicle. That is, the front wheel steering angle conforms to the front wheel Ackerman steering mode, while the rear wheel steering angle is determined by the rear wheel toe angle. , By matching the front wheel steering with the rear wheel toe-in, the vehicle's yaw rate and body slip angle can be effectively reduced, the steering response time can be shortened, and the handling stability and driving safety of the vehicle under conditions such as high-speed lane changes and emergency obstacle avoidance can be improved.

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