Rear-Wheel Steering Yaw Control for Emergency Obstacle Avoidance
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Solution Overview
Problem
Existing vehicle control systems using electronic power to steer rear wheels can compromise vehicle stability and turning radius at high speeds, particularly in emergency situations, making collision avoidance difficult.
Innovation Solution
A method and system for determining target yaw rates and controlling rear wheel turning based on magnitude relationships between actual yaw rates and preset conditions to enhance stability and reduce turning radius during emergency obstacle avoidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the rear wheel turns in the same direction as the front wheel at high speed to improve vehicle stability, then the vehicle stability is improved, but the turning radius is increased making collision avoidance difficult
Solution Approach 1:
The patent applies dynamics by making the rear wheel turning angle adaptive rather than fixed. The control system dynamically adjusts the rear wheel turning angle based on real-time vehicle speed and steering angle inputs. At different speed ranges, the system optimizes the rear wheel turning strategy: at lower speeds allowing larger opposite-direction turning for reduced turning radius, and at higher speeds using smaller same-direction turning for maintained stability, thus resolving the contradiction between stability and turning radius
Solution Approach 2:
The patent changes the parameter of rear wheel turning angle based on vehicle operating conditions. By using speed and steering angle as input parameters, the system calculates and adjusts the optimal rear wheel turning angle parameter in real-time. This parameter adaptation allows the vehicle to achieve appropriate turning radius at low speeds while maintaining stability at high speeds, effectively resolving the technical contradiction
2Length of moving object
If the rear wheel turns in the opposite direction to the front wheel to reduce turning radius, then the turning radius is reduced for easier steering, but the vehicle stability deteriorates at high speed
Solution Approach 1:
The system dynamically adjusts the rear wheel turning strategy based on real-time vehicle speed. When vehicle speed is below a threshold, the system permits the rear wheel to turn in the opposite direction with a larger angle to achieve reduced turning radius. When speed exceeds the threshold, the system transitions to same-direction turning with smaller angle to maintain stability. This dynamic adaptation resolves the contradiction between turning radius and stability
3Device complexity
If fixed high and low speed thresholds are used for rear wheel turning control, then the control logic is simplified, but the vehicle cannot effectively adapt to emergency situations requiring different turning characteristics
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing optimal rear wheel turning angles for different speed and steering angle combinations in lookup tables. During emergency situations, the system quickly retrieves pre-computed values based on current speed and steering angle, enabling rapid response without complex real-time calculations. This approach maintains simple control logic while achieving high adaptability to emergency situations
Solution Approach 2:
The system uses feedback from speed sensors and steering angle sensors to continuously monitor vehicle state and adjust rear wheel turning angle accordingly. The control algorithm receives real-time feedback on vehicle dynamics and modifies the rear wheel command to achieve optimal turning characteristics for the current situation, including emergency maneuvers. This feedback mechanism enables adaptability while keeping the control logic structured and manageable
Data Source
AI summary
A vehicle control method includes: determining a target yaw rate of a vehicle when the vehicle meets a rear wheel turning control condition; acquiring a first yaw rate of the vehicle when a front wheel of the vehicle turns at a front-wheel maximum turning angle and a rear wheel of the vehicle turns at a rear-wheel maximum turning angle in a turning direction opposite to the front wheel, and a second yaw rate of the vehicle when the front wheel turns at the front-wheel maximum turning angle and the rear wheel does not turn; determining a magnitude relationship between the first yaw rate and the target yaw rate, and a magnitude relationship between the second yaw rate and the target yaw rate, respectively; and controlling the rear wheel of the vehicle according to whether the magnitude relationships meet a preset control condition.