Magnetostrictive torque sensor performance-nonlinear analysis

The effects on performance of magnetostrictive torque sensors due to nonlinear properties of magnetic materials are analyzed. A solution for the nonlinear problem is described. For constant magnetomotive force (constant current) excitation, nonlinear effects dramatically reduce the predicted output signal of the sensor from that computed using linear models. Saturation and the subsequent fall-off of a sensor signal as excitation current is increased are predicted and agree well with experimental results. The sensor signal continually increases with the increase of excitation frequency. As is shown, this gain must be balanced against growing problems of sensor signal-to-noise ratio, surface-localized noise, and requirements for higher-power/higher-voltage excitation sources.>