Autonomous Precision Control of Satellite Formation Flight under Unknown Time-Varying Model and Environmental Uncertainties

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Autonomous Precision Control of Satellite Formation Flight under Unknown Time-Varying Model and Environmental Uncertainties

Cho, Hancheol / Udwadia, Firdaus E. / Wanichanon, Thanapat

This paper presents a new methodology for autonomous precision control of satellite formations in the presence of uncertainties and external disturbances. The methodology is developed in two steps. First, using a nominal system model that provides the best assessment of real-life uncertainties, a nonlinear controller that satisfies the formation configuration requirements is developed without making any linearizations/approximations. This closed-form control strategy is inspired by results from analytical dynamics and uses the fundamental equation of constrained motion. In the second step, an adaptive continuous robust controller is developed to compensate for model uncertainties and field disturbances to which the satellite formation may be subjected. This controller is based on a generalization of the concept of sliding mode control, and produces no chattering. The control gain is automatically updated in real time and the norm of the trajectory error is guaranteed to lie within user-provided desired bounds without a priori knowledge of the uncertainty/disturbance bounds. Since the control force is explicitly obtained, the approach is not computationally intensive, thereby making the approach ideal for on-orbit autonomous real-time satellite formation control. Numerical simulations demonstrate the effectiveness of the proposed control methodology, in which a desired formation configuration is required to be precisely and autonomously maintained despite large initial trajectory errors in the presence of uncertain satellite mass and environmental disturbances.