Directional decoupling of piezoelectric sheet actuators for high-precision shape and vibration control of plate structures

In this thesis, two directional decoupling methods are proposed for high-precision shape and vibration control, namely the Active Stiffener (AS) and the MacroFiber Composite (MFC). The objectives of the investigation are to analyze the two configurations, understand their characteristics, provide insights for better design and control, and experimentally validate the theoretical findings.; The Active Stiffener is a new stiffener-piezoceramic actuator pair concept that consists of a passive insert (stiffener) placed between the host structure and the active piezoelectric actuator. The basic premise is that the insert (stiffener) will reduce the transmitted moment to the host structure in the direction desired for decoupling while allowing an adequate moment to transmit in the actuation direction. In this study, a local analysis of the AS actuator is first developed to gain a proficient understanding of the actuator and determine parameters that can best achieve the decoupling actions. Using finite element analysis techniques, investigations of a single AS attached to rigid and flexible host structures are presented. The effects of various material and system parameters on the applied bending moments (active authority in both directions) to the host structure are illustrated. It is shown that, with proper design, the AS can significantly reduce the active authority in a selected direction while maintaining sufficient authority in the orthogonal direction.; To demonstrate the effectiveness of the new AS configuration for shape and vibration control, analytical and experimental efforts are carried out to examine the performance of the AS actuators in controlling 2-dimensional plate structures. Analysis is performed on two large flexible circular plate structures, one having the Direct Attached (DA) actuators and the other utilizing the AS actuators. For shape control, more reductions in surface error can be achieved with the AS compared to equivalent systems having DA actuators. The DA actuators generate more localized deformation than the AS in the structure due to the coupled planar actuation of the DA actuator. The analysis results performed for each deformation shape demonstrate that a stiffener height greater than zero maximizes the shape control performance, i.e. the DA actuator is never the ideal actuator. The experimental results verify the analytical predictions and clearly demonstrate the performance improvement of the AS concept over the DA actuator. (Abstract shortened by UMI.)...