Abstract: The design and implementation of control strategies for large, flexible smart structures presents challenging problems. Uncertainties stem from control structure interaction, modeling errors, and parameter variations (such as fuel consumption). We developed a new algorithm called H$-$INF$/ robust control for natural frequency variations (H$-$INF$//NF) that includes the knowledge of the natural frequency uncertainty bounds. In addition, we were successful in implementing this algorithm on a flexible smart structure in our laboratory. This smart structure was a cantilever beam that used NiTiNOL shape memory alloy (SMA) actuators. The performance of H$-$INF$//NF algorithm was compared with the modified LQG/LTR algorithm using a settling time specification. The H$-$INF$//NF controller exhibited dramatically reduced sensitivity to natural frequency uncertainty as compared to the modified LQG/LTR controller. The standard LQG/LTR control algorithm produced controllers that saturated the NiTiNOL actuators used on the test article. To overcome this saturation problem, we used a modified LQG/LTR design algorithm. We successfully implemented the proposed algorithm on a simple cantilever beam test article. !10
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