High-Resolution Tunneling Magneto-Resistance (TMR) Angular Displacement Sensor With Enhanced Subdivision Interpolation Technique

This article proposed an enhanced subdivision interpolation technique for tunneling magneto-resistance (TMR)-based angular displacement sensor. The resistances of TMR angle sensor vary as a sine and cosine function of the rotation angle. The innovative circuit employs subdivision interpolation circuit, in conjunction with 90° phase shift and high-precision dc bias-voltage techniques, converting an analog signal with sinusoidal characteristics from a single TMR device into standard incremental digital signals that vary linearly over full-circle range. Owing to its rapid response capabilities, the enhanced interpolation method is capable of accurately tracking the angular displacement of the rotation axis even at higher speed. The novel methodology ensures that its performance is least affected by the phase imbalance, offset error, and amplitude mismatch of the paired TMR devices. It possesses low dependence on many circuit and sensor nonidealities. Detailed simulation, optimization, and experimentation studies have been conducted to validate the proposed methodology. Experimental results reveal that the TMR angular displacement sensor achieved an angular displacement resolution of 0.009°, the nonlinearity of 0.146%, as well as an accuracy of ±0.58° over a range of 360° at the speed of 60 r/min. This work provides a significant guide for the development of high-performance angular displacement sensors in practical applications.