# Position Detection System for Moving-Magnet Linear Motors Based on a Magnetoresistive Sensor Array

## TL;DR

This paper presents a new position detection system for moving-magnet linear motors using magnetoresistive sensors, offering high accuracy and no length limitations.

## Contribution

A novel position detection system using magnetoresistive sensor arrays for moving-magnet linear motors is proposed.

## Key findings

- The system achieves a linear correlation coefficient higher than magnetic grid rulers.
- Position detection accuracy of ±9 μm is demonstrated experimentally.
- The method supports long-distance position detection without length limitations.

## Abstract

The moving-magnet linear motor has received considerable attention in the development of logistic and factory automation in recent years. A reliable position detection system is the key to achieving the precise position and control of the motor. At present, the magnetic grid-scale and grating-scale are the most widely used traditional detection methods. However, these are not suitable for position detection with moving-magnet linear motors. They have the disadvantages of being easy to disturb, having a high cost, and exhibiting a limited measurement range. In this work, a moving-magnet linear motor position detection system based on an array of magnetoresistive sensors is used. The array is configured by arranging the magnetoresistive sensors at equal intervals along a line parallel to the trajectory of the armature. Then, the permanent magnet is fixed on the rotor and detected by sensors. When the rotor crosses the sensors in a parallel line, the changes in the magnetic field cause the magnetoresistive sensors to output two voltage signals directly proportional to the corresponding position changes. The signals are collected by the AD7606 and transmitted to the FPGA and STM32 controller for data processing, and the actual position of the rotor is calculated. This method has no length limitation and can be used for long-distance position detection. The experimental results show that the position detection system has a higher linear correlation coefficient compared with the magnetic grid ruler, in addition to a capability of ±9 μm accuracy, which verifies the validity of the position detection method for the moving-magnet linear motor.