Computation of inverse of magnetostriction model for Terfenol-D

The use of a non-linear model or non-linear inverse model in a control configuration has been shown to significantly improve the performance of actuators that use hysteretic materials to drive them. A method to calculate the inverse of a model for the hysteretic material Terfenol-D is presented here, to be used as part of a full control configuration for Terfenol-D actuators. This inverse is based on a magnetostriction model that has been shown to characterize the behavior of Terfenol-D well. Initially unbounded, accumulating errors in the inverse are analyzed and a method to bound the error for periodic input is presented. Simulations show steady-state tracking of strain waveforms that reach 95% of saturation to within 2% in an open-loop configuration. For use with inputs as high as 95% of saturation, though, the ratio of the input frequency to the sampling rate must be kept below specified levels. With inputs that reach only 85% of saturation, the error from inversion is below 0.2% and can be controlled by a parameter choice.