# Low-Speed Permanent Magnet Synchronous Motor Rotor Position Estimation Using Structural Vibration Modal Phase Carrier

## TL;DR

This paper introduces a new method for estimating rotor position in low-speed motors using structural vibrations instead of electrical signals.

## Contribution

A novel sensorless control method using structural vibration modal phase for rotor position estimation in low-speed motors.

## Key findings

- The proposed method achieves stable rotor position estimation even under strong noise.
- Estimation error is significantly lower than conventional back-EMF-based methods at low speeds.

## Abstract

To address the challenges of diminished back-EMF, high noise interference, and reduced accuracy in traditional low-speed sensorless control, this study proposes a rotor position estimation method based on structural vibration characteristics. The coupling mechanism between air-gap electromagnetic force density and stator structural vibration modes is analyzed. This analysis reveals that rotor spatial information is embedded within specific modal phases, establishing the physical basis for utilizing vibration phase as a position carrier. Accordingly, a workflow encompassing signal acquisition, modal selection, and phase calculation is developed and integrated into a sensorless control system. Simulation results demonstrate that the proposed method achieves stable estimation even under strong noise. The estimation error shows clear performance advantages over conventional back-EMF-based methods in the low-speed region, validating its effectiveness and robustness at low speeds. This research provides a new approach that introduces non-electrical structural information as a complementary channel to overcome the inherent limitations of electrical-signal-based position estimation at low speeds.