Sensorless position estimation of linear voice-coil transducers

In this paper, a method for sensorless position estimation of linear transducers at standstill is suggested. The method makes use of current pulses, which is a common sensorless starting technique for three-phase synchronous motors. Most transducers, however, possess only one phase. In order to find a unique solution, the proposed method differs in some important aspects from the methods used in three-phase systems. A general discussion of different inductance phenomena is presented. A combination of these phenomena makes it possible to find a unique position. The proposed method is verified using a linear voice-coil transducer with permanent magnets, which is taken from a hard-disk drive. The experimental results are presented and discussed.