Performance Investigation of a Simplified TMR-Based Rotary Position Sensing System

Measurement of angular position of a rotating shaft is required in several industrial, medical, and aerospace applications. In this article, a simplified position measurement system using Tunneling Magneto-Resistance (TMR) sensing technique is proposed to cater this objective. The TMR-based rotary position-sensing system (TRPS) uses inherent merits of the TMR technology for shaft angle measurement. It processes the sensor signals, possessing sine-cosine behavior, and renders a linearly varying output. The TRPS is primarily designed and tested for angle measurement over full-circle range. However, a modified design, with lower component count, is also proposed and verified for half-circle range measurements. The circuit architecture of the TRPS and its operation are discussed in detail. Owing to its faster response, the TRPS can be used to track the angular position of the shaft, even at high speeds. The effects of non-idealities of sensor and circuit, on the TRPS output, are analyzed. Several simulation- and emulation-based tests are conducted to validate the suitability of the TRPS for static and dynamic inputs. The TRPS is found to be useful for angle measurement up to shaft speeds of 12000 rpm. A TRPS hardware is fabricated using AAT003-10E TMR integrated circuit (IC) as the sensor and tested. Experiments show that the TRPS output varies linearly for 360 degrees range. Finally, a performance comparison study is carried out to highlight the achievements of the TRPS over the existing schemes.