DEVELOPMENT AND ANALYSIS OF A SELF-SENSING MAGNETOSTRICTIVE ACTUATOR DESIGN

A self-sensing magnetostrictive actuator design based on a linear syst ems model of magnetostrictive transduction for Terfenol-D is developed and analyzed. Self-sensing, or the ability of a transducer to sense i ts own motion as it is being driven, has been demonstrated for electro mechanical transducers such as moving voice coil loudspeakers and, mos t recently, piezoelectric distributed moment actuators. In these devic es, self-sensing was achieved by constructing a bridge circuit to extr act a signal proportional to transducer motion even as the transducer was being driven. This approach is analyzed for a magnetostrictive dev ice. Working from coupled electromechanical magnetostrictive transduct ion 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 inheren tly non-linear, and does not, therefore, lend itself well to the tradi tional bridge circuit approach to self-sensing.