Enhancing Induced Strain Actuator Authority Through Discrete Attachment to Structural Elements
In structural control, induced strain actuators are used by bonding them or embedding them in a structure. With bonded or embedded actuators used for inducing flexure, the developed in-plane force contributes indirectly through a locally generated moment. Control authority in this configuration is thus limited by actuator offset distance. In this paper, a new concept of flexural or shape control is presented, whereby 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). 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. This configuration is different from the bonded actuator configuration in two ways. One, because the actuator and the structure are free to deform independently, the in-plane force of the actuator can result in an additional moment on the structure and enhanced control. Second, the actuator can be offset from the structure without an increase in the flexural stiffness of the basic structure. This allows for the optimization of the offset distance to maximize control. Enhanced control is demonstrated by comparing the static response of a discretely attached actuator beam system with its bonded counterpart system. The advantage of this configuration over the bonded configuration is also verified experimentally.