In this paper we present a hybrid Sliding Mode Control (SMC) and Constant Amplitude Feedback Control (CAFC) architecture for a slewing flexible adaptive structure. The SMC controller is used to servo the adaptive structure and the CAFC is used to suppress vibrations of the flexible structure. In addition a traditional Linear-Quadratic Regulator (LQR) controller was developed and tested. This system consists of 1) a single-axis servo DC motor and encoder for large angle slewing and 2) a graphite/epoxy composite structure with embedded strain sensors/actuators for active vibration suppression. The results of this study include the analytical development and numerical simulation verification. Minimum time maneuvers based on an equivalent rigid structure are used to slew the flexible active structure. Numerical simulation studies were performed to compare the SMC/CAFC controller with the LQR controller. A nonlinear optimization algorithm was used to determine optimal component weights for the LQR control weighting matrices Q and R. Both controllers were also compared to a passive SMC case to show benefits of using active vibration control. Several case studies are reviewed that involve minimizing tracking and residual tip deflection errors. The results showed a reduction in residual vibration for both cases studied. A final test was performed that investigated the robustness to parameter variations by increasing the tip mass. Both control architectures showed favorable results, but the LQR controller required larger control effort.

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