IMPEDANCE-BASED MODELLING OF INDUCED STRAIN ACTUATORS BONDED ON RING STRUCTURES

Abstract

An impedance-based model to describe the in-phase, out-of-phase and unsymmetric actuation of induced strain actuators bonded to the surface of a circular ring has been developed. The essence of the impedance approach is to match the actuator impedance with the structural impedance at the ends of the actuators, which includes the dynamic effects of the system. In the model derivation, the dynamics of the ring are based on the Rayleigh-Ritz method. The appropriate representation of the loading due to induced strain actuation is discussed. The in-phase and out-of-phase actuation authority is compared. It is shown that out-of-phase actuation has higher authority in exciting the lower order bending modes, while in-phase actuation has higher authority in exciting the higher order circumferential modes. In-phase actuation does excite the lower order bending modes through the in-plane and out-of-plane displacement coupling, but with an order of magnitude lower than out-of-phase actuation. A good correlation between the dynamic finite element analysis using piezoelectric elements available in ANSYS 5.0 is found. Experimental results of a circular ring actuated in-phase and out-of-phase are also presented. Differential methods of bonding straight actuators on curved surfaces are investigated. Experimental verification of the impedance-based models is conclusive, particularly for the out-of-phase actuation.