Experiments and simulations of large-angle flexible beam control using an adaptive truss

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Virginia Tech


The objective of this thesis is to study the vibration suppression capabilities of a double-octahedral adaptive truss with an appended flexible beam. Three cases are studied. The first case is an experimental and analytical investigation of flexible beam control using an adaptive truss positioned in an equilibrium configuration such that the beam is parallel to the gravity field. A linear model of the system is derived, and a linear LQR control law is designed. Control experiments are conducted and show that the adaptive truss performs good vibration control of the flexible beam with the effective modal damping increased from 0.012 for the uncontrolled vibrations to 0.19 for the controlled vibrations. Good agreement between the open-loop and closed-loop simulations and experiments is achieved such that a correlation coefficient of 0.92 is observed between the experiment and simulation open-loop data and a correlation coefficient of 0.85 is observed for the experiment and simulation closed-loop data. The second case is the analysis and vibration control of the flexible beam while the adaptive truss is positioned at some large-angle configuration such that the flexible beam is severely affected by gravity. In this case a nonlinear beam model is developed and a linear LQR control law is implemented. Simulations show vibration control of the flexible beam for large-angle configurations of the truss, and that the vibration control performance is highly dependent on the linearization point of the control law. The third case is the analysis and control of large-angle slewing of a flexible beam using the adaptive truss. In this case the nonlinear beam model is implemented with both linear LQR and nonlinear gain-scheduled control laws. Simulations indicate that the adaptive truss achieves vibration control of the beam during slewing manuvers for all control laws tested with the nonlinear control law achieving superior vibration control performance in comparison to all control laws tested.