Steer-by-Wire Angle Limiting With Trajectory Feedback
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Solution Overview
Problem
In steer-by-wire steering systems, the maximum wheel setting angle is not optimally set for non-linear driving situations, leading to suboptimal driving behavior.
Innovation Solution
A steer-by-wire steering system with a control unit that outputs a characteristic map for the target wheel setting angle based on steering angle and vehicle speed, allowing for dynamic adjustment of the maximum settable wheel setting angle based on deviations between actual and calculated vehicle trajectories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum wheel setting angle is limited based on vehicle speed, then the steering system ensures stable driving at high speeds, but the driving behavior becomes suboptimal in non-linear driving situations
Solution Approach 1:
The patent applies dynamics by making the maximum wheel setting angle dynamically adjustable based on real-time vehicle trajectory deviation. Instead of using a fixed speed-based limit, the system continuously adapts the angle limit according to whether the vehicle is understeering or oversteering, allowing optimal performance across different driving conditions while maintaining stability when needed
Solution Approach 2:
The system implements feedback by comparing the actual vehicle trajectory with the calculated trajectory and using this deviation information to adjust the maximum wheel setting angle. The control unit receives feedback on trajectory error and modifies the angle limit accordingly, creating a closed-loop control system that optimizes steering behavior based on actual vehicle response
2Ease of operation
If a fixed virtual gear ratio function is used, then the steering system is simple to control, but the wheel setting angle cannot be optimized for different driving situations
Solution Approach 1:
The patent transforms the static virtual gear ratio function into a dynamic one by introducing trajectory deviation as an additional control variable. The system maintains functional simplicity while adapting the wheel setting angle to different driving situations through real-time adjustments based on actual versus calculated trajectory comparison
Data Source
AI summary
A steer-by-wire steering system (10) for a vehicle is specified, having a control element (12) that can be actuated by a driver for inputting a steering angle, an actuating mechanism (14) for setting a wheel setting angle, and a control unit (28) that is configured to output a characteristic map for the target value of a position of the actuating mechanism (14) based on a steering angle of the control element (12) and a vehicle speed. A nominal wheel setting angle (y) adjustable by the actuating mechanism (14) depends on a set steering angle and on a vehicle speed, wherein the maximum settable nominal wheel setting angle (ym,n) is limited depending on the vehicle speed, and wherein the control unit (28) is configured to calculate a vehicle trajectory based on a vehicle speed and a wheel setting angle and, in the event of a deviation of an actual vehicle trajectory from the calculated vehicle trajectory, to adjust the maximum settable nominal wheel setting angle (ym,n) based on the deviation. Furthermore, a method for method for adjusting a wheel setting angle is specified.