Terfenol-D Nonlinear Vibration Absorber

An active nonlinear vibration absorber scheme for flexible structures is demonstrated. The absorber exploits the nonlinear transduction of nonbiased Terfenol-D actuators. It uses a quadratic feedback control law and the "quadratic" strain-field characteristic of a nonbiased Terfenol-D actuator to achieve a nonlinear coupling between the absorber and the forced structure. A saturation phenomenon is induced by tuning the frequency of the underdamped second-order absorber to one-half that of the primary structure. As a result, the structural vibrations are greatly reduced. This type of control has been demonstrated previously using linear actuators; the nonlinearities have been introduced via the control algorithm. Here, we show that nonbiased Terfenol-D actuators can perform effectively the "squaring" operation, instead of the algorithm, and achieve similar results. We develop the theory and present experimental results for the control of the first and second modes of a cantilever beam. We also consider application of the strategy experimentally when the forcing is due to a rotating imbalance. In this case, the excitation source is nonideal. Our results indicate that the saturation-based control technique implemented with a Terfenol-D actuator constitutes an effective nonlinear vibration absorber.