Electric Power Steering Control for Vibration Suppression
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Solution Overview
Problem
The existing electric power steering apparatus experiences unstable control and self-excited vibration due to large deviations between actual and target turning angles, leading to driver discomfort and difficulty in calculating appropriate assist torque.
Innovation Solution
An electric power steering apparatus with a control unit that calculates a first assist component based on steering torque and a turning angle command value, and includes a turning angle feedback control unit to calculate a second assist component. When the deviation between the turning angle and the command value exceeds an allowable range, the control unit removes the second assist component and changes the ideal model to enhance convergence, suppressing self-excited vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turning angle feedback control is continued when deviation is large, then control stability is improved, but self-excited vibration occurs and convergence cannot be ensured
Solution Approach 1:
The patent extracts the second assist component from the assist command value when the deviation between actual and target turning angles exceeds the allowable range. This removal prevents the feedback control from generating self-excited vibration and ensures convergence of the ideal model, while still allowing the control system to remain stable through the first assist component alone.
Solution Approach 2:
The patent dynamically adjusts the control system characteristics by switching between different ideal models based on the deviation magnitude. When deviation is within the allowable range, the first ideal model is used for normal feedback control. When deviation exceeds the range, the system switches to the second ideal model with modified characteristics to enhance convergence and suppress vibration.
2Reliability
If second assist component is removed from assist command value, then control stability is improved, but settling time increases and assist torque becomes unstable
Solution Approach 1:
The patent performs preliminary calculation of the second assist component even when it is removed from the assist command value. The turning angle feedback control unit continues to calculate the second assist component based on the deviation, so that when the deviation returns to within the allowable range and the second assist component is reintroduced, the system can quickly converge without requiring a long settling time.
3Object-generated harmful factors
If ideal model characteristics are changed to enhance convergence, then self-excited vibration is suppressed, but control system characteristics change substantially
Solution Approach 1:
The patent applies different ideal model characteristics to different operating conditions. The first ideal model is used under normal conditions (deviation within allowable range) to maintain standard control characteristics. The second ideal model with enhanced convergence characteristics is applied only when deviation exceeds the allowable range to suppress vibration, thus localizing the characteristic change to specific operational states rather than permanently altering the control system.
Data Source
AI summary
The control apparatus calculates the first assist component on the basis of the steering torque. The control apparatus calculates the turning angle command value from the steering torque and the first assist component on the basis of the ideal model, executes turning angle feedback control for matching the actual turning angle with the turning angle command value, and calculates the second assist component. The control apparatus adds the second assist component to the first assist component to calculate the assist command value. When the deviation between the actual turning angle and the turning angle command value is out of the allowable range, the control apparatus changes the ideal model to remove the second assist component from the assist command value and enhance convergence of the turning angle feedback control system.