Adaptive Feedback Control of Spacecraft with Flexible Appendages by Modeling Error Compensation

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A new adaptive control system for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages is designed. The model of the spacecraft includes unstructured modeling uncertainties. For the purpose of control, a moment generating device is located on the rigid hub. For the synthesis of the control law, only the output variable (pitch angle) is used for feedback. An adaptive feedback linearizing control law is derived for the trajectory control of the pitch angle. Interestingly, the structure of the controller is independent of the elastic mode dynamics of the spacecraft, since unmodeled functions appearing in the inverse (feedback linearizing) control law are estimated using a high-gain observer for feedback. It is shown that the closed-loop system is exponentially stable. An additional attractive feature of the control system is that it accomplishes compensation of unstructured uncertainties in the model. Simulation results for the spacecraft model show precise trajectory control and vibration suppression.


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