On the directional decoupling characteristics of active stiffeners for shape control oftwo-dimensional structures

Abstract

A substantial amount of research exists concerning shape control of two-dimensional opticalmirror structures with attached piezoelectric ceramic sheet actuators. Researchers haveinvestigated the optimal placement, size, and electrode pattern of the piezoceramicactuators for maximizing the system performance. In many situations, the performancecould be further improved with tailoring of the actuator configuration. For example, it wasfound that to avoid ‘exciting’ higher order deformation modes (the wrinkling effect) intwo-dimensional structures, the ideal actuator would be one that is directionally decoupled,i.e., only actuates in one direction when controlling certain deformation modes ofinterest. The active stiffener (AS) concept has been proposed to realize such aneffect, where a stiffener is inserted between a host structure and the piezoelectricceramic actuator patch. The objective of the research presented in this paperis to develop a local analysis of the AS actuator to gain good insight into itscharacteristics and determine parameters that can best achieve the decoupling actions.Using a three-dimensional finite element model, analyses of a single active stiffenerattached to rigid and flexible host structures are presented. The effects of variousmaterial and system parameters on the bending moments applied to the hoststructure are illustrated. It is shown that, with proper design, the active stiffener cansignificantly reduce the bending moment (active authority) in a selected direction whilemaintaining sufficient authority in the orthogonal direction. The results of thisinvestigation should provide valuable guidelines for the design of effective ASactuators.