Comparison of classical with robust control for SMA smart structures

Smart structures is now a vigorous area of study. One type of smart structure employs shape memory alloys, such as Nitinol, in the form of thin wire actuators to provide enhanced damping. To the authors knowledge, the only control algorithm that has been implemented heretofore has been a simple on-off control law. In this study, other control algorithms are employed, ranging from classical to a robust controller based on the LQG/LTR algorithm, and their relative effectiveness is compared. The robust control algorithm gave the best active damping enhancement. Two mechanical systems are studied. The first is an aluminium cantilever beam for which the free-vibration damping of the fundamental mode was enhanced. The second system studied is a three-mass system with its three natural frequencies below 3 Hz.