Liu D., Zhang Z., Hua H.

For lightly damped structures under periodic excitation, vibration responses are generally composed of forced vibration and the natural vibration. Lightly damped modes and periodic vibration render the synthesis of active controllers very difficult and high order controllers are usually generated with less feasibility in practical implementation. To obviate this difficulty, two active control strategies, active damping and harmonic cancellation, are considered to control vibration over a broad frequency band. In the experiment of active vibration suppression, harmonic cancellation and active damping are implemented simultaneously, where harmonic cancellation is based on an inverse modeling technique and no observer is needed. The inverse of the dynamic model of a test rig with two elastic plates is guaranteed by the collocated placement of transducer and actuator, which theoretically results in a minimum phase system. The inverse model was realized on a digital controller, and the experimental results show that vibration suppression can be achieved if the time delay of control signal is sufficiently small.