Electric Power Steering High-Frequency Compensation Reduces CPU Load
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Solution Overview
Problem
Conventional electric power steering apparatuses face high CPU load due to real-time calculation of assist gradient, leading to excessive memory usage, and suffer from instability and reduced responsiveness when assist gradient is not accurately obtained, especially in regions with large steering torque or varying vehicle speed.
Innovation Solution
An electric power steering apparatus with a control apparatus that includes an assist torque command calculator and a high-frequency compensator, where the assist torque command calculator receives a corrected steering torque signal produced by feeding back a high-frequency compensation signal to the steering torque signal, allowing for reduced calculation load and memory usage while maintaining stability and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time calculation of assist gradient is performed, then stability and responsiveness are improved, but CPU load increases and memory usage becomes excessive
Solution Approach 1:
The patent extracts only the necessary high-frequency components from the assist torque command signal through filtering, rather than performing complete real-time assist gradient calculation. This selective extraction reduces computational complexity while maintaining the essential stability and responsiveness functions.
Solution Approach 2:
The patent applies preliminary filtering to extract high-frequency components before further processing. By pre-processing the signal to isolate relevant frequency components, the system reduces subsequent calculation requirements while preserving stability and responsiveness characteristics.
2Device complexity
If assist gradient calculation is avoided to reduce CPU load, then calculation load and memory usage are reduced, but stability and responsiveness deteriorate
Solution Approach 1:
The patent applies local quality by focusing computational resources only on the high-frequency components of the signal that are most critical for responsiveness. Instead of uniformly processing the entire signal spectrum, the system selectively enhances relevant frequency bands, maintaining responsiveness while reducing overall calculation load.
Solution Approach 2:
The patent performs partial action by implementing only the essential high-frequency filtering and compensation functions needed for responsiveness, rather than completing the full assist gradient calculation. This partial implementation achieves the critical responsiveness function with reduced computational burden.
3Device complexity
If fixed filter characteristic is used, then device complexity is reduced, but ability to adapt to varying assist gradient conditions deteriorates
Solution Approach 1:
The patent implements dynamic adaptation by making the filter characteristic variable based on operating conditions such as vehicle speed and steering torque. The system dynamically adjusts filter parameters to match the current assist gradient conditions, enabling adaptability without requiring excessively complex fixed-filter designs.
Solution Approach 2:
The patent changes filter parameters dynamically according to operating conditions. By adjusting filter characteristics based on detected variables like vehicle speed and steering torque, the system adapts to varying assist gradient conditions while maintaining manageable device complexity through parameter variation rather than structural complexity.
Data Source
AI summary
An electric power steering apparatus includes a high-frequency compensation unit that outputs a high-frequency compensation signal obtained by filtering the high-frequency components of an assist torque command signal and multiplying the filtered high-frequency components by a gain; a corrected steering torque signal obtained by negatively or positively feeding back the high-frequency compensation signal to a steering torque signal is inputted to an assist torque command calculation unit; the assist torque command calculation unit outputs the assist torque command signal in accordance with the corrected steering torque signal.