Identification and robust control of flexible structures using shape memory actuators

The application of shape memory alloy materials as actuators and sensors in the active control of flexible structures has been extensively reported in the literature. The design of active controllers plays an important role in the overall development of smart structures for a given application. To design active controllers for flexible structures, a mathematical representation of the system is needed. The process of constructing a model to describe the vibration properties of a structure based on experimental test data is known as structural identification method. To account for any uncertainties in the structural models and to accomplish good closed loop system performance and noise suppression properties, we have developed robust control design methodologies for flexible structures. We have utilized the eigensystem realization algorithm (ERA) for system identification and linear quadratic Gaussian with loop transfer recovery (LQG/LTR) method for designing robust controllers for a simple cantilever beam test article. The shape memory alloy, NiTiNOL, is used as an actuator. The LQG/LTR method has been modified to accommodate the limited control force provided by the actuators. The closed loop performance of the cantilever beam is experimentally determined for various types of uncertainties. The properties of robust controllers are demonstrated.