Electric Power Steering Control Unit Stabilizing Vibration Mode
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Solution Overview
Problem
Conventional electric power steering apparatuses face challenges in stabilizing the vibration mode of a two-inertia system without deteriorating responsiveness, particularly in the vicinity of the on-center steering position, where existing solutions either compromise responsiveness or stability.
Innovation Solution
A control unit incorporating a feedforward control section, a feedback control section, and a response control section that adjust the current command value based on input and output angle information, enabling pole-and-zero cancellation and phase compensation to stabilize the vibration mode while maintaining responsiveness, with the feedback control section arranging poles to enhance damping and the feedforward control section setting stability and responsiveness independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional feedback control is used to stabilize the vibration mode of the two-inertia system, then stability is improved, but responsiveness deteriorates
Solution Approach 1:
The control system is segmented into multiple independent control sections: a feedforward control section that processes input angle information to generate a first compensation signal, and a feedback control section that processes output angle information to generate a second compensation signal. These sections operate independently and their outputs are combined, allowing stability and responsiveness to be optimized separately without compromising either characteristic.
Solution Approach 2:
The feedforward control section performs preliminary action by processing input angle information before the system response occurs. This allows the system to anticipate and prepare for changes, improving responsiveness while the feedback control section simultaneously stabilizes vibrations through error correction.
2Stability of the object's composition
If existing solutions suppress vibration mode are applied, then stability is improved, but responsiveness is compromised
Solution Approach 1:
The feedback control section continuously monitors output angle information and generates a second compensation signal based on the deviation from desired behavior. This feedback mechanism stabilizes the vibration mode by correcting errors in real-time without interfering with the feedforward control's responsiveness to input changes.
Solution Approach 2:
The system changes control parameters dynamically by combining two different compensation signals: the first compensation signal from feedforward control optimizes responsiveness to input changes, while the second compensation signal from feedback control optimizes stability by suppressing vibrations. The superposition of these signals achieves both objectives simultaneously.
Data Source
AI summary
A control unit of an electric power steering apparatus including a feedforward control section, that inputs input angle information and calculates a first compensation signal compensating the current command value, a feedback control section, that inputs output angle information and calculates a second compensation signal compensating the current command value, and a response control section that adjusts the current command value based on the first compensation signal and the second compensation signal.