Steering Anti-Catch Algorithm for Active Front Steering
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Solution Overview
Problem
Active Front Steering (AFS) systems experience 'steering catch-up' situations at higher steering rates, where power steering cannot provide sufficient assist, leading to increased torque felt by the driver, especially during slow steering and center position changes.
Innovation Solution
The system determines the vehicle's steering state and calculates an offset reduction factor using existing vehicle sensors, applying it to the desired road wheel angle to reduce undesirable torque, by selectively enabling a Steering Anti-Catch-Up (SAC) algorithm that adjusts the steering offset based on steering wheel velocity and vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If AFS system increases steering wheel angle via electronically controlled superposition angle to improve steering responsiveness, then steering speed is improved, but steering catch-up occurs causing increased torque at steering wheel
Solution Approach 1:
The system dynamically adjusts the steering offset based on real-time steering wheel velocity and vehicle speed conditions. The SAC algorithm modifies the superposition angle dynamically, reducing it when catch-up conditions are detected (high steering rate combined with low vehicle speed), thereby preventing excessive torque while maintaining steering responsiveness under normal conditions
Solution Approach 2:
The system changes the steering offset parameter adaptively based on operating conditions. By monitoring steering wheel velocity and vehicle speed, the system adjusts the magnitude of the superposition angle applied to the driver's input, reducing the offset when catch-up is likely and maintaining full offset benefit when conditions are favorable
2Ease of operation
If AFS system applies steering offset to improve steering performance, then steering responsiveness is improved, but steering catch-up situations occur during slow steering and center position changes
Solution Approach 1:
The system implements feedback by continuously monitoring steering wheel velocity and vehicle speed to detect catch-up conditions. When the SAC algorithm detects high steering rates combined with low vehicle speeds (conditions prone to catch-up), it reduces the steering offset accordingly, preventing torque spikes while maintaining assist performance during normal operation
Data Source
AI summary
A vehicle implements a steering anti-catch (SAC) algorithm that reduces a superimposition angle added to the steering wheel angle in order to reduce occurrence of steering catch. The superimposition angle may be determined according to an AFS system. The reduction of the superimposition angle according to the SAC algorithm is amplified when the driver is steering away from a center position, the vehicle speed is below a threshold, and a voltage for powering the power steering system is below a threshold. The amount by which the superimposition angle is reduced may be limited to a maximum reduction and may be subject to a limit in its rate of change as well.