| Piezoelectric elements, which have the ability to convert mechanical energy into electrical energy and vice versa, are often used in active and passive vibration control applications. When attached to a vibrating structure, the piezoelectric element deforms and energy is dissipated as current is driven through a shunt connected to its electrodes. This thesis examines piezoelectric vibration control methods that provide adaptability to environmental changes and flexibility in implementation. First, an autonomous controller is developed which maximizes energy dissipation using synchronized switching, a technique that periodically switches the elements to an external resistor-inductor shunt. The instants of switching are identified through a filtered velocity signal, and the technique's performance is optimized when the filter's center frequency approximately matches the structure's natural frequency of interest. In simulation and laboratory measurements, the controller measures the tip velocity of a cantilever beam and adaptively aligns the filter with the beam's fundamental frequency using a fuzzy logic algorithm. With minimal a priori knowledge of the system, the controller adapts to changes in the beam's frequency and excitation, thus outperforming traditional synchronized switching. The thesis then shifts its focus to the attachment mechanism between piezoelectric elements and vibrating structures. Piezoelectric elements are bonded to permanent magnets, which are attached to the surface of a steel cantilever beam through their magnetic attraction. The magnetic-piezoelectric control mounts provide a viable alternative to traditional epoxy attachment methods for piezoelectric elements which allows for easy in-the-field reconfiguration. The resonant shunt technique is used to demonstrate the control mounts' vibration characteristics, and a finite element model, which accounts for the contact stiffness between the beam and control mounts, is used to determine the beam's tip velocity. Three magnetic-piezoelectric control mount designs, each with a different magnetic configuration, are considered. By alternating the magnetic dipoles along the length of the mounts, the attachment force is increased, which results in larger vibration reduction. Even with an imperfect bond, the control mounts provide significant attenuation, while also providing the flexibility to easily reconfigure the elements on a vibrating structure. |
