Wheel Longitudinal Force Control for Steering Effectiveness
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Solution Overview
Problem
Existing vehicle behavior control methods fail to effectively suppress the decrease in steering effectiveness (rudder effectiveness) across varying lateral acceleration conditions, particularly when lateral acceleration is large, due to reliance on incomplete information and lack of consideration for road disturbances.
Innovation Solution
A method and device that calculate and independently control the longitudinal force difference between left and right wheels based on input parameters, using a control map to adjust the steering ratio and yaw moment, thereby correcting the longitudinal force to maintain steering effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback configuration is used to correct the yaw moment based on the difference between reference lateral acceleration and actual lateral acceleration, then the control accuracy is improved, but the device complexity increases due to requiring all state quantities for calculation
Solution Approach 1:
The patent extracts and directly measures only the necessary longitudinal force difference between left and right wheels using sensors, rather than calculating reference lateral acceleration from multiple state quantities. This selective measurement approach reduces computational complexity while maintaining control accuracy by focusing only on the critical parameter needed for correction.
Solution Approach 2:
The control device integrates multiple functions into a single system: it measures longitudinal force differences, calculates yaw moments, determines speed increasing ratios, and executes steering corrections all within one unified control unit. This multi-functional integration simplifies the overall device architecture while preserving the sophisticated control capabilities needed for accurate steering effectiveness maintenance.
2Device complexity
If the control method does not take road surface disturbance into consideration, then the device complexity is reduced, but the steering effectiveness decreases in high lateral acceleration scenarios
Solution Approach 1:
The patent implements a feedback mechanism where the actual longitudinal force difference measured by sensors is compared with the target longitudinal force difference calculated from steering angle and speed. The control system continuously adjusts the steering actuator based on this feedback to maintain the desired steering effectiveness, automatically compensating for road surface disturbances without requiring complex disturbance detection systems.
Solution Approach 2:
The control system uses the vehicle's own operational parameters (steering wheel angle, vehicle speed, actual longitudinal force measurements) to self-regulate and maintain steering effectiveness. The system serves itself by using internally available data and self-measured forces rather than requiring external disturbance detection, achieving reliable performance through self-contained measurement and control.
Data Source
AI summary
A difference in a longitudinal force indicating a difference between the longitudinal force acting on left and right wheels is obtained. A correction amount of the longitudinal force acting on each wheel is calculated based on the difference in the longitudinal force, and each wheel is independently controlled. When the difference in the longitudinal force is obtained, a speed increasing ratio of a front wheel steering angle for changing an overall steering ratio is calculated based on a preset control map and an input parameter including a vehicle speed and a lateral acceleration or the vehicle speed and steering wheel angle. A yaw moment to be generated around a weighted center of the vehicle is calculated based on the speed increasing ratio and a steering wheel angle of the vehicle as the input parameter. The difference in the longitudinal force is then calculated based on this yaw moment.