Electric Power Steering Phase Compensation Stability
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Solution Overview
Problem
Existing electric power steering devices experience instability and vibration when switching phase compensation characteristics with vehicle speed, due to the influence of previous phase compensation results on current calculations, leading to adverse effects on steering wheel behavior.
Innovation Solution
An electric power steering device with a phase compensation unit that stores multiple phase compensation characteristics for different vehicle speed regions, determines the appropriate characteristic based on current and previous results, and selects the phase-compensated torque signal within an allowable range or frequency region to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase compensation characteristic is switched in accordance with vehicle speed, then phase compensation effect is improved, but steering wheel stability deteriorates due to influence of previous calculation results
Solution Approach 1:
The system pre-calculates phase compensation values for multiple vehicle speed regions and stores them in advance. When the vehicle speed changes, the system switches between pre-calculated values rather than performing real-time recalculation, which prevents instability caused by transitional calculation states.
Solution Approach 2:
The phase compensation characteristic is made dynamic by switching between different compensation values based on detected vehicle speed. The system adapts the phase compensation amount according to the current vehicle speed region, optimizing performance for different operating conditions while maintaining stability through proper switching logic.
2Productivity
If phase compensation calculation uses previous calculation results, then calculation continuity is improved, but vibration occurs when parameter value switches
Solution Approach 1:
The vehicle speed range is segmented into multiple discrete regions, each with its own optimized phase compensation characteristics. By dividing the continuous speed range into segments and assigning specific compensation values to each segment, the system achieves both calculation efficiency and vibration suppression at transition points.
Solution Approach 2:
The system changes the phase compensation parameter based on vehicle speed regions. By adjusting the compensation parameter according to pre-defined speed thresholds and characteristics, the system optimizes phase compensation for different operating conditions while preventing harmful vibrations during transitions.
Data Source
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AI summary
Provided is an electric power steering device including a phase compensation unit having a desirable phase compensation characteristic for each vehicle speed region, which suppresses deterioration in stability of a steering system in a case where the phase compensation characteristic is changed to a different phase compensation characteristic, in which the phase compensation unit includes: a plurality of phase compensation calculation units configured to execute phase compensation calculation based on each phase compensation characteristic; a phase compensation characteristic determination unit configured to determine a phase compensation characteristic based on a vehicle speed signal output from a vehicle speed sensor; and a selection unit configured to select a phase-compensated torque signal output by the phase compensation unit from phase compensation calculation results output by the plurality of phase compensation calculation units in consideration of an amount of change in phase compensation calculation result at a time of switching the phase compensation characteristic.