Phase demodulation of magnetic GMR signal for virtual sensing applications by using hilbert transform

GMR (Giant MagnetoResistance) sensors, which are used in conjunction with magnetic encoders (magnetic pole wheels), have a huge number of applications in automotive and machine industry, where they are used to compute the rotational speed of rotating parts like wheels and shafts. In this paper, we present an analytical model of magnetic pole wheel signal as it is sensed by a GMR sensor. Experimental measurements are performed to check the validity of the mathematical model. Furthermore, we present a novel digital signal processing technique, which incorporates the Hilbert transformer to phase demodulate this GMR signals to compute high resolution instantaneous position and speed information. A frequency domain analysis is then deployed to analyze the signal for any low frequency vibrations present in the rotating part.