EPS Motor Control Using Frequency-Segmented Torque Signals
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Solution Overview
Problem
Existing electric power assisted steering systems face challenges in maintaining consistent steering feel due to friction changes from road conditions and hardware limitations, requiring a more adaptive and lightweight friction control logic.
Innovation Solution
A motor control method that generates low and high frequency assist torque signals using band pass filtering, with a high frequency assist torque signal calculated as a product of the high pass torque signal and a gain reflecting factor, allowing for adaptive control based on vehicle speed and amplitude differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If friction control logic is made adaptive to road conditions, then steering feeling consistency is improved, but control system complexity increases
Solution Approach 1:
The control logic is segmented into two distinct parts: a lightweight friction compensator that provides basic adaptive friction compensation, and an optional advanced friction compensator for more complex scenarios. This segmentation allows the system to maintain simplicity while providing adaptability, resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The system changes parameters (friction compensation values) based on detected road conditions and vehicle operating states. By dynamically adjusting these parameters, the system achieves adaptability to friction changes without requiring complex control logic, thus resolving the technical contradiction.
2Speed
If friction control logic is simplified for lightweight operation, then system responsiveness is improved, but adaptability to varying road conditions deteriorates
Solution Approach 1:
The friction compensator operates autonomously by detecting road conditions and vehicle states, then automatically adjusting friction compensation without requiring complex external control logic. This self-service approach enables rapid response while maintaining adaptability, resolving the contradiction between response speed and adaptability.
Solution Approach 2:
The system rapidly adjusts friction compensation parameters based on real-time detection of road conditions and vehicle operating states. This parameter-based approach enables fast control response while maintaining adaptability to varying road conditions, resolving the technical contradiction.
3Ease of operation
If high frequency assist torque gain is increased to improve steering responsiveness, then steering feeling is improved, but excessive amplitude components cause instability
Solution Approach 1:
The system uses feedback from the detected input steering torque signal and vehicle speed to dynamically adjust the high frequency assist torque gain. By monitoring the actual steering torque and comparing it with reference values, the system can increase gain for responsiveness while detecting and correcting excessive amplitude components, thus resolving the contradiction between responsiveness and stability.
Solution Approach 2:
The high frequency assist torque gain is made dynamic rather than fixed, allowing it to change based on vehicle speed and detected torque amplitude. This dynamic adjustment enables the system to optimize responsiveness at different operating points while preventing instability through automatic gain reduction when amplitude becomes excessive, resolving the technical contradiction.
Data Source
AI summary
A motor control method for controlling a motor of an electric power assisted steering system includes: generating a low pass torque signal and a high pass torque signal, respectively; generating a low frequency assist torque signal using the low pass torque signal and the vehicle speed; generating a high frequency assist torque signal using a high pass torque signal and the vehicle speed; generating a torque command signal using a sum of the low frequency assist torque signal and the high frequency assist torque signal; and generating a voltage output signal for driving the motor using the torque command signal.