Enhanced Structural Control with Discretely Attached Induced Strain Actuators

A new configuration where induced strain actuators such as piezoelectric ceramic patches or shape memory alloys are attached to a structure at discrete points (as opposed to being bonded) is presented. This paper specifically addresses discretely attached induced strain actuators like piezoceramic and electrostrictive actuators which are available in the form of plates or patches, and includes actuator flexural stiffness considerations. When activated, such actuators deform along with the structure (like bonded actuators), but in this case the actuator and the structure are free to deform independently. In such a scenario, the in-plane force of the actuator results in an additional moment on the structure and enhanced structural control. Also because now the actuator can be offset from the structure without an increase in the basic flexural stiffness of the structure, the actuator offset distance can be optimized to maximize actuator authority. Enhanced control is demonstrated by comparing the static response of a discretely attached actuator/beam system with its bonded counterpart system. Through a proper choice of the offset distance, the flexural control authority measured in terms of the moment applied to the substrate structure can be increased considerably for stiff and thick substrates. The advantage of this configuration over the bonded configuration is also verified experimentally. The limitations and considerations for the implementation of the concept in realistic structures are also discussed.