Multi-satellite systems are getting more and more prominent in recent years. They enable various new application areas from distributed communication networks and science missions as well as close-range applications. These new applications demand suitable control methods, especially for close-range satellite formation applications, which impose the highest demands. Control approaches that are both distributed and robust are required. Distributed to be scalable, fail-safe and to achieve a common goal. Robust to guarantee stability in the presence of uncertainties like sensor noise, disturbances, actuator errors and orbit perturbations. This paper presents a combination of robust H_∞ control and distributed control using consensus approach. A distributed consensus-based generalized plant description has been derived that includes disturbances as well as noise on each satellite and that suits the requirements for H_∞ synthesis. By applying H_∞ synthesis individual controllers for all satellites in a specific formation setup can be computed that guarantee robustness with respect to the given uncertainties and that work in a distributed manner. This is guaranteed by using the consensus approach which enables the satellites to follow a common goal (reaching a specific formation configuration) and to pursue the common goal even if any of the satellites fails. In addition to describing the principles of of this approach, spccial focus is set on the development of a potential field based collision avoidance method and its implementation within the controller, since collision avoidance is of major importance especially in close-range formation flying. Simulations based on realistic scenarios show the applicability of the developed distributed robust control method to a realistic space scenario, as well as the additional safety provided by collision avoidance.
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