Magnetostrictive torque sensor performance-nonlinear analysis

Effects on performance of magnetostrictive torque sensors due to nonlinear properties of magnetic materials are analyzed. A method of 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 subsequent fall-off of sensor signal as excitation current is increased are predicted and the prediction agrees well with experimental results. Sensor signal continually increases with increase of excitation frequency. It is shown that 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