L1 Adaptive Control of Flexible Spacecraft Despite Disturbances

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The development of an L1 adaptive control system for the control of an orbiting spacecraft with flexible appendages is the subject of this paper. It is assumed that the system parameters are unknown and that disturbance input is acting on the spacecraft. The spacecraft is controlled by a moment producing device located on the central rigid body. Based on the L1 adaptive control theory, a new control law for large angle rotational maneuver of the spacecraft is derived. The control system includes a state predictor for generating the estimates of the unknown parameters for feedback. The control moment is obtained by passing an estimated control signal through a lowpass filter. The controller is synthesized using only the pitch angle and its derivative. In the closed-loop system, the pitch angle is controlled to the target angle and flexible modes are stabilized. The designed control law achieves quantifiable performance bounds by the choice of large adaptation gain. Interestingly, the controller structure is independent of the number of elastic modes retained in the model. Simulation results show that precise rotational maneuver of the spacecraft and vibration suppression in the presence of large parameter uncertainties and disturbance moment are accomplished using the L1 adaptive control law.


Aerospace Engineering | Controls and Control Theory | Space Vehicles | Systems and Communications