Bond Graph Models for Linear Motion Magnetostrictive Actuators

Abstract

Bond graph models for the audio range response of a dynamically continuous, linear motion magnetostrictive actuator are formulated and presented. The actuator involves a continuous rod of magnetostrictive material that extends, contracts, and vibrates in modes when energized by magnetic flux produced by a coil. The left end is fixed, force is extracted from the right end. The bond graph model includes dynamics of the energizing coil, the flux routing circuit, magnetic to mechanical energy conversion, and mechanical elements. Constitutive relations for magnetostriction suggest use of a multipart capacitor with ports for magnetic and mechanical power flow; constraints imposed by modal dynamics require a separate mechanical port for each vibration mode. Values were assigned to bond graph parameters in a non-empirical manner: solely from theory and handbook data. State equations and transfer functions were extracted from the bond graph. For audio range operation, theory (the bond graph model) compared well with experiment (measurements taken on a magnetostrictive actuator designed and built by the author).