| Previous researchers have demonstrated that a piezoelectric vibration absorber can be constructed by shunting a piezoelectric actuator with an inductive (RL) circuit. These devices have been shown to be useful for both modal damping and suppression of fixed harmonic excitations. Semiactive piezoelectric vibration absorbers, which have the ability to track a varying excitation frequency, have also been proposed. Various implementation problems have been identified with these methods, however.; This thesis presents a new active-passive adaptive piezoelectric vibration absorber design for the purpose of suppressing harmonic excitations with varying frequency. This design uses a passive inductive shunt circuit together with active control to achieve performance that is superior to semi-active absorbers while still requiring relatively little power. The active control consists of three parts: an adaptive inductor tuning action, which provides the frequency tracking ability, a negative resistance action , which increases performance, and a coupling enhancement action, which increases the performance and robustness of the absorber.; The performance of the new design is experimentally validated using a cantilever beam test stand. Parametric studies are also used to demonstrate that the adaptive absorber concept can provide superior performance while requiring less control effort, compared to several state-of-the-art vibration control methods. It is observed that excellent vibration suppression performance can be obtained, even when the excitation frequency is changing quickly. In order to optimally design the adaptive absorber, it is necessary to gain a better understanding of the transient dynamics of a time-varying system. A series of nondimensional parametric studies are used for this purpose, and the insight obtained is used to construct a design methodology for the adaptive active-passive absorber.; The new design is also extended to allow independent suppression of multiple harmonic excitations with varying frequencies. A multi-frequency passive circuit and an active decoupling control action are introduced for this purpose, and an optimal tuning algorithm is also derived. The performance of the multi-frequency adaptive absorber is verified using an active isolation mount test stand, which demonstrates the versatility of the piezoelectric absorber concept. Practical implementation issues such as experimental modeling and experimental tuning are also addressed. Finally, recommendations are given for future research in this area. |
