Reverse compensation to the angle estimate error using multi-groups sensor

The magnetoresistance(MR) sensor has been successfully demonstrated in rotational speed and position detection, however, the uneven magnetic field or the installation eccentricity are all decrease the signal quality and influence the reliability of measurement. Therefore, this paper presents the theory of time grating in displacement calculation and proposes a reverse compensation method using multi-groups sensor to improve measurement performance. A pair of linear tunnel magnetorsistance (TMR) sensors are spatially displaced by 90 degrees electrical and excited by sin or cos signals. Another pair of sensors is reversed and diametrically apart to the former. A compensated traveling wave is got whose phase is proportional to the displacement of rotation. The angle displacement is measured by counting the time pulses that serve as measurement standards. The effectiveness of the proposed scheme is verified through a prototype permanent magnet motor system. That shows the amplitude of the measurement error from 0.17 degrees to 0.04 degrees, which reduces 75% by the special arrangement of the multi-groups TMR sensor. Even though the magnetic sensor presented here uses TMR sensors, the proposed technique is suited without any modification for Hall and other MR sensors as well.