On analog feedback control for magnetostrictive transducer linearization

The magnetostrictive transducer output force, displacement, and bandwidth characteristics are well suited for a variety of active vibration control applications. However, their use is limited in part because these transducers are known to be non-linear. The transducer in this study is assumed to be a linear system and its output harmonics are assumed to be disturbance inputs. Two feedback control models are proposed and one is used to obtain expressions for predicting the change in harmonic amplitudes of displacement and acceleration as functions of frequency and parameters for the controller, load, and transducer. An approach based on magnetostrictive transduction modelling is presented for experimentally determining appropriate transducer model parameters for use in the feedback control model. Experimental measurements using simple, analog, PD (proportional plus derivative) acceleration feedback control are presented to validate the expressions. The closed loop feedback control system model resulted in predicted changes in harmonic acceleration amplitudes ranging from +2 to -30 dB (depending upon the frequency of the disturbance input) that were verified experimentally. A significant extension of the linear range of transducer behavior, due to feedback control, is also demonstrated. (C) 1998 Academic Press Limited.