# Magnetic Circuit Design and Optimization of Tension–Compression Giant Magnetostrictive Force Sensor

## TL;DR

This paper proposes and optimizes a magnetostrictive force sensor for helicopter components to improve load monitoring accuracy and reliability.

## Contribution

A novel GM force sensor with permanent magnet bias and optimized magnetic circuit design is introduced.

## Key findings

- The magnetic flux uniformity of the optimized sensor increased by 7.44%.
- The Hall output voltage increased linearly by 1.125% with improved magnetic flux density.
- Removing the magnetic side wall improved magnetic flux guidance through the GMM rod.

## Abstract

The variable-pitch connecting rod of a helicopter bears axial tensile and compressive loads during operation. The traditional load monitoring method using strain gauge is easily affected by external conditions. Therefore, a giant magnetostrictive (GM) tension and compression force sensor with permanent magnet bias is proposed and optimized. Because the bias magnetic field plays a decisive role in the performance of the sensor, this paper has carried out in-depth research on this. Firstly, the mathematical model of the magnetic circuit is established, and the various magnetic circuits of the sensor are simulated and analyzed. Secondly, the magnetic flux uniformity of the GMM rod is used as the evaluation index, and the relative permeability of the magnetic material and the structure are systematically studied. The influence of parameters on the magnetic flux of the magnetic circuit, and finally the optimal parameter combination of the magnetic circuit is determined by orthogonal test. The results show that when the magnetic circuit without the magnetic side wall is used, the magnetic material can better guide the magnetic flux through the GMM rod; the magnetic flux uniformity of the optimized GMM force sensor is increased by 7.44%, the magnetic flux density is increased by 13.9 mT and the Hall output voltage increases linearly by 1.125% in the same proportion. This provides an important reference for improving the utilization rate of GMM rods and also improves the safety of flight operation and reduces maintenance costs.