Concept for rotation measurement of a rotor of an electric motor

The online calibration method for electric motor rotors using magnetic field sensors addresses systematic errors by updating sector lengths based on time duration sequences, ensuring accurate rotation measurement and reducing noise in multi-pole-pair motors.

WO2026132455A1PCT designated stage Publication Date: 2026-06-25MAXON MOTOR AG
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Patent Information

Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
MAXON MOTOR AG
Filing Date
2025-12-19
Publication Date
2026-06-25

AI Technical Summary

Technical Problem

Existing rotation measurement methods for electric motor rotors using magnetic field sensors, such as Hall sensors, suffer from systematic errors due to fabrication tolerances, leading to inaccuracies in velocity measurement and increased acoustic noise, especially in multi-pole-pair motors, which require offline calibration with incremental or absolute encoders.

Method used

A method for online calibration of rotor rotation measurement using magnetic field sensors, where the current average revolution time duration is determined from a sequence of time durations between sensor output changes, allowing for updates of stored sector lengths to compensate for measurement inaccuracies, without the need for offline calibration or additional encoders.

Benefits of technology

This approach provides stable and accurate rotation measurement by compensating for fabrication tolerances, reducing computational load, and eliminating the need for offline calibration, thus minimizing acoustic noise and vibration in multi-pole-pair motors.

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Abstract

A rotation measurement of a rotor of an electric motor is achieved in a more efficient manner by no longer adhering to an offline calibration concept which comes along with additional overhead before shipment and additional problems to cope with in case of using, for instance, multi-pole-pair motors. Rather, rotation measurement of a rotor of an electric motor using magnetic field sensors statically arranged around the rotor for measuring magnetic fields generated by magnetic poles of the rotor so that sensor signals of the magnetic field sensors change at borders between sectors into which a full rotation of the rotor is partitioned may be achieved in a manner which lends itself for an online calibration by making use of a sequence of time durations between consecutive changes of the magnetic field sensors' output signals: a current average revolution time duration of the rotor may be determined based on a sum of M recent time durations of the sequence of time durations, wherein M ≥ N and N is the number of sectors.
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