Development and Analysis of a Self-Sensing Magnetostrictive Actuator Design

A self-sensing magnetostrictive actuator design based on a linear systems model of magnetostrictive transduction for Terfenol-D is developed and analyzed. Self-sensing, or the ability of a transducer to sense its own motion as it is being driven, has been demonstrated for electromechanical transducers such as moving voice coil loudspeakers and, most recently, piezoelectric distributed moment actuators. In these devices, self-sensing was achieved by constructing a bridge circuit to extract a signal proportional to transducer motion even as the transducer was being driven. This approach is analyzed for a magnetostrictive device. Working from coupled electromechanical magnetostrictive transduction equations found in the literature, the concept of the transducer's "blocked" electrical impedance and motional impedance are developed, and a bridge design suggested and tested. However, results presented in this paper will show that magnetostrictive transduction is inherently non-linear, and does not, therefore, lend itself well to the traditional bridge circuit approach to self-sensing.