Robust coordinated control for on-orbit substructure transportation under distributed information

On-orbit assembling technology provides a promising way for deploying large space systems. Transporting a substructure by adjusting its orbit and attitude states is a key to assembling it to the main body of a large space system. This paper develops a robust coordinated control mechanism for multiple modular robots when they cooperate to control the orbit and attitude movements of a substructure. By designing a distributed information-based scheme for control allocation, the modular robots are able to obtain their control inputs through their local interaction. The computation and communication burdens are therefore distributed among the modular robots. Nonlinear disturbance observers are introduced to suppress the adverse effects caused by external disturbances, parameters uncertainties and orbit-attitude coupling effect of the substructure. A new input saturation compensator is designed to suppress the effect caused by input saturation whenever the commanded control inputs of the modular robots exceed the permissible range. The stability of the closed-loop system is analyzed using the Lyapunov method, and the tuning conditions of the coordinated control mechanism are obtained. Numerical simulations demonstrate the effectiveness of the proposed method.