Method and control system for measuring the rotor position of an electric motor

By generating test signals in the motor and combining filtering and phase-locked loop technology, the predicted value is iteratively adjusted, which solves the problem of insufficient rotor position measurement accuracy at low and high speeds, and realizes high-precision rotor position measurement and control across the entire speed range.

CN122316153APending Publication Date: 2026-06-30SCHAEFFLER TECHNOLOGIES AG & CO KG
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Patent Information

Application Number
CN202510479535.X
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-04-16
Publication Date
2026-06-30

AI Technical Summary

Technical Problem

Existing sensorless motor rotor position measurement methods suffer from insufficient accuracy at low and high speeds. In particular, traditional open-loop methods are susceptible to integral drift and parameter changes, observer methods are computationally complex and costly, and model reference adaptive systems are inaccurate in speed identification at low speeds.

Method used

By generating test signals and superimposing them in the dq coordinate system, the motor response current is measured, the estimated value is iteratively adjusted, and by combining filtering and phase-locked loop technology, the rotor position is accurately measured in different speed ranges using back electromotive force. A modular control system is used for precise measurement.

Benefits of technology

High-precision measurement of rotor position was achieved across the entire speed range of the motor, especially at low speeds, which improved the adaptive capability and measurement stability of the control system and reduced the impact of noise.

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Abstract

This invention relates to a method for measuring the rotor position of a motor, characterized by the following steps: (a) superimposing a test signal for measuring the rotor position and an adjustment signal for adjusting the motor in a d-q coordinate system; (b) measuring the motor's response current to the test signal; (c) providing a predicted value for the rotor position; (d) transforming the response current to a coordinate system offset by ±45° from the predicted value, thereby obtaining a first current component and a second current component; (e) calculating the difference between the vector lengths of the first current component and the second current component; (f) if the difference is less than or equal to a predetermined threshold, feeding back the predicted value as the rotor position; if the difference is greater than the predetermined threshold, iteratively adjusting the predicted value and repeating the measurement steps until the difference is less than or equal to the predetermined threshold. This method achieves accurate sensorless rotor position determination.
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