Electric Power-Assisted Steering Torque Compensation
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Solution Overview
Problem
Existing electric power-assisted steering systems face challenges in maintaining a uniform steering feel for drivers, particularly during rapid corrective steering at the on-center position, due to inconsistent torque feedback.
Innovation Solution
An electric power-assisted steering apparatus that includes a rack force estimator, a target torque calculator, and a motor controller, which calculate and apply a compensation torque based on the difference between the target torque and driver torque, using parameters determined by vehicle velocity to ensure consistent steering feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an excessive current for reducing joggling caused by steering is output to maintain vehicle yaw stability, then vehicle yaw stability is improved, but the feeling of steering becomes inconsistent during rapid corrective steering at the on-center position
Solution Approach 1:
The patent applies dynamics by making the current output adaptive based on steering conditions. The controller dynamically adjusts the current magnitude according to whether the steering wheel is at the on-center position or off-center position, and according to the steering angle range. This dynamic adjustment allows the system to maintain vehicle yaw stability during general steering while avoiding excessive torque during rapid corrective steering at the on-center position, thus resolving the contradiction between stability and steering feel consistency.
Solution Approach 2:
The patent applies local quality by differentiating the control strategy for different steering conditions. Specifically, it applies different current output characteristics for on-center position steering versus off-center position steering, and for different steering angle ranges. This localized differentiation allows the system to optimize for specific scenarios (e.g., reducing joggling during general steering) without negatively impacting other scenarios (e.g., rapid corrective steering), thereby resolving the technical contradiction.
2Ease of operation
If a motor current is generated according to steering torque to assist driver steering, then steering assistance is improved, but torque feedback becomes inconsistent during rapid corrective steering
Solution Approach 1:
The patent applies feedback by continuously monitoring the steering wheel angle and comparing it with the target angle. The controller uses this feedback information to adjust the motor current output in real-time. During rapid corrective steering at the on-center position, the feedback mechanism allows the system to detect the deviation and adjust the torque output accordingly, maintaining consistent torque feedback while still providing steering assistance.
Solution Approach 2:
The patent makes the motor current generation dynamic by adjusting the current magnitude based on the steering wheel angle range and whether the wheel is at the on-center position. This dynamic current generation ensures that the torque feedback remains consistent during rapid corrective steering while maintaining effective steering assistance during normal driving conditions.
Data Source
AI summary
Provided are an electric power-assisted steering apparatus and a method of controlling the same. A lateral acceleration is calculated on the basis of an estimated rack force, and a target torque is calculated by using the calculated lateral acceleration and a target torque parameter set according to a vehicle velocity. Then, a compensation torque corresponding to a difference between the target torque and a driver torque is applied to uniformly maintain the feeling of steering even when a steering rate is changed. Also, a steering control logic based on a driver torque and a steering control logic based on a compensation torque are separated, thus facilitating steering control appropriate for steering circumstance.