EPS Traction Steer Mitigation via CVR Gain Scalars
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Solution Overview
Problem
High torque output FWD/AWD vehicles experience traction steer events due to differences in tractive forces at the front wheels, leading to unbalanced steering rack forces, which can cause the handwheel to become stuck off-center, requiring extra driver input to compensate.
Innovation Solution
A control system for power steering that generates a motor command based on handwheel velocity and modifies it using a traction torque signal, applying the command to an actuator to mitigate traction steer by adjusting proportional and integral gains and blending factors within a PID control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high torque output is provided by the powertrain, then vehicle acceleration performance is improved, but traction steer events occur causing handwheel to become stuck off-center
Solution Approach 1:
The control system continuously monitors handwheel position and velocity, comparing actual position against desired center position. When off-center position is detected during high torque conditions, the system activates corrective torque through the actuator to return the handwheel to center, creating a closed-loop feedback mechanism that prevents traction steer from becoming stuck.
Solution Approach 2:
The patent replaces mechanical compensation methods with an electronic control system that uses sensors to detect handwheel position and actuators to apply corrective torque. This electronic substitution eliminates the need for mechanical adjustments or driver manual compensation, providing precise and consistent correction of traction steer effects.
2Ease of operation
If driver compensates for traction steer by forcing handwheel to center, then handwheel position control is improved, but extra input torque is required from driver
Solution Approach 1:
The power steering control system performs self-correction of traction steer effects without requiring driver intervention. The system autonomously detects off-center handwheel position during high torque conditions and automatically applies corrective torque through the actuator, making the steering system self-sufficient and eliminating the need for driver compensation efforts.
Solution Approach 2:
The control system uses feedback from handwheel position sensors to automatically adjust actuator torque output. When the system detects that the handwheel is off-center during high torque conditions, it calculates and applies the appropriate corrective torque, creating a closed-loop system that eliminates the need for additional driver input torque.
3Ease of operation
If corrective torque is applied to return handwheel to center during traction steer events, then handwheel position control is improved, but steering responsiveness may be degraded
Solution Approach 1:
The control system dynamically adjusts the corrective torque magnitude based on real-time operating conditions. During high torque acceleration events, the system applies stronger corrective torque to counteract traction steer. During normal driving conditions, the system reduces or eliminates corrective torque, allowing the steering system to respond naturally to driver input without artificial intervention.
Solution Approach 2:
The system applies corrective torque only when and where needed - specifically during high torque acceleration events when traction steer occurs. During normal operating conditions, the system allows natural steering response without intervention. This partial application of corrective action maintains steering responsiveness in most conditions while providing targeted correction during problematic high-torque events.
Data Source
AI summary
Technical solutions are described for mitigating traction steer using an electric power steering system (EPS). A control system for a power steering system including a processor and memory are provided. The memory includes instructions that, when executed by the processor, cause the processor to generate a motor command as a function of a handwheel velocity, and to modify the motor command based upon a traction torque signal. A method for controlling a power steering system is also provided. The method includes generating a motor command as a function of a handwheel velocity; modifying the motor command based upon a traction torque signal; and applying the motor command to an actuator of the power steering system.