Resolver Speed Estimation Using FFT for Eccentric Motor Shafts
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Solution Overview
Problem
The existing electric motor speed control systems using resolvers face accuracy issues due to shaft eccentricity, which complicates precise speed control of electric motors.
Innovation Solution
An electric motor speed control apparatus comprising a rotation speed estimation unit that performs FFT analysis on the speed detection signal to generate an estimated rotation speed value, and a control unit that implements speed control to reduce deviations between the estimated value and the speed command, using eccentricity compensation to correct for eccentricity-induced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resolver is used to detect the rotation speed of an electric motor, then the speed control function is implemented, but detection accuracy deteriorates when the resolver shaft is eccentric with respect to the motor shaft
Solution Approach 1:
The patent introduces an intermediary processing system (FFT analysis unit and rotation speed estimation unit) between the resolver and the speed control system. The resolver output signal is subjected to FFT analysis to extract frequency components, and the rotation speed is estimated from these components rather than using the raw resolver signal directly. This intermediary processing eliminates the impact of shaft eccentricity on detection accuracy while preserving the speed control function.
2Measurement precision
If the resolver shaft is aligned with the motor shaft to eliminate eccentricity, then detection accuracy improves, but device complexity and alignment difficulty increase
Solution Approach 1:
The patent replaces the mechanical alignment approach with a signal processing approach. Instead of requiring precise mechanical alignment between the resolver shaft and motor shaft to achieve accurate detection, the system uses FFT analysis and rotation speed estimation algorithms to process the resolver output signal. This substitution of mechanical precision requirements with computational processing simplifies the mechanical assembly while maintaining or improving detection accuracy.
Data Source
AI summary
The electric motor speed control apparatus in an embodiment comprises a rotation speed estimation unit and a control unit. The rotation speed estimation unit generates an estimated value of a rotation speed of an electric motor by using a result of FFT analysis of a speed detection signal ωFBK, which is based on a detection result from a resolver for detecting the rotation speed of the electric motor, and the speed detection signal ωFBK. The control unit implements speed control so as to reduce deviation between the estimated value of the rotation speed and a speed command value for speed control of the electric motor.