Magnetic field distribution of magnetic encoder with TMR sensor using finite element analysis

Abstract

Selecting a cost effective magnetic encoder is an important step in electrical machines motor drive system design. Resolvers and high-resolution encoders provide excellent measurement accuracy. However, market competition has forced designers to look into less expensive solutions that have relatively large measurement errors. This paper studies the effect of TMR sensor measurement errors on magnetic field performance. The magnetic flux distribution of the encoder, and the distance effect between magnet and TMR sensor were simulated using finite element method. The simulation results of different types of materials for bearings of the encoder are compared. The magnetic field distribution performance degradation due to different types of materials for encoder is identified. The results show an acceptable magnetic flux distribution on ceramic material with the bearings of the encoder. The material of the disc magnet were determined to achieve high performance characteristics. In addition, the flux density become decreases and increases when TMR sensor is located at far-off or near distances from a field source, magnet. Therefore, there is optimal flux density need for investigating new allocation between magnetic sensors and magnet. The distance of magnet with TMR sensor also the main factor and 2 mm is identified as the best position and ceramic is good for bearing to reduce magnetic interference.