EPS Torque Feedback Compensation for Resonance Stability
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Solution Overview
Problem
EPS steering systems experience diminished stability at resonance frequencies due to increasing gain, leading to reduced system response and noise interference.
Innovation Solution
Implementing a low pass filter (LPF) and proportional-integral-derivative (PID) controller to compensate for torque deviations, using a gain map to adjust filter characteristics based on vehicle speed, and controlling the motor with a torque command value to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gain is increased to improve system response, then steering assist performance is improved, but stability at resonance frequencies deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the measured torque is compared with the filtered calculated torque, and the difference is used to generate a compensation signal that adjusts the motor torque command. This closed-loop feedback stabilizes the system at resonance frequencies while maintaining responsiveness, directly resolving the contradiction between gain increase and stability.
Solution Approach 2:
The patent dynamically adjusts the filter characteristics based on vehicle speed through a gain map, changing the filtering parameters adaptively. This allows the system to optimize both response speed and stability across different operating conditions, resolving the contradiction by making the system parameters variable rather than fixed.
2Reliability
If filter characteristics are adjusted to reduce noise interference, then signal quality is improved, but system response accuracy deteriorates
Solution Approach 1:
The patent makes the filter characteristics dynamic by adjusting them based on vehicle speed through a gain map. The filter adapts its characteristics according to operating conditions, allowing optimal noise reduction at low speeds while maintaining response accuracy at higher speeds, thus resolving the contradiction between signal quality and measurement precision.
Solution Approach 2:
The patent changes the filter parameters adaptively based on vehicle speed, using a gain map to adjust the filtering strength. This dynamic parameter adjustment allows the system to optimize both noise rejection and response accuracy across different operating regimes, resolving the contradiction between these two opposing requirements.
3Stability of the object's composition
If torque compensation is increased to improve stability, then system stability is improved, but control complexity increases
Solution Approach 1:
The patent uses a feedback approach where the torque compensation is generated based on the difference between measured and filtered torque signals. This systematic feedback mechanism provides stability through a structured control loop, managing complexity through algorithmic organization rather than adding unnecessary system components.
Solution Approach 2:
The patent introduces a filter as an intermediary component that processes the calculated torque signal before it is used for control. This intermediary filtering step simplifies the overall control strategy by separating the torque estimation function from the control function, making the system more manageable while achieving stability through the coordinated action of the filter and controller.
Data Source
AI summary
A method for steering system stability compensation includes receiving a calculated torque value associated with the steering system, providing the calculated torque value to a filter, receiving an output value from the filter, and determining a difference between the output value of the filter and a measured torque value associated with the steering system. The method also includes determining a torque command value based on the calculated torque value and the difference between the output value of the filter and the measured torque value, and controlling a motor associated with the steering system using the torque command value.