Analysis and development of a sensor concept for multistable actuators with passive magnetic shape memory alloy

Based on the current state of research, the aim of this paper is to develop a position sensor for actuators using passive magnetic shape memory alloys. The presented sensor concept converts the strain dependent permeability of the magnetic shape memory alloy into an inductance change by using a sensor coil arrangement. The change in inductance of the sensor coil is converted into a change in the resonant frequency of a parallel oscillating circuit. A microcontroller detects the resonant frequency of the circuit and converts it into a position sensor signal. To evaluate the functionality of the sensor, a test rig is developed that deforms the magnetic shape memory element under realistic application conditions. Experimental measurements in a climate chamber are used to evaluate the performance and characteristics of the sensor. The characteristic, temperature drift and hysteresis behavior are analyzed. It is proven that the presented sensor concept can be used to determine the position of passive magnetic shape memory alloy actuators.