Formation control of multi-robots for on-orbit assembly of large solar sails

• Using four space walking robots to deploy a large solar sail is proposed.
• Formation control of the four robots is considered.
• Adaptive sliding mode control is applied to the formation operating of the robots.
• A disturbance observer with finite-time convergence is embedded in the controller.
• The stability and the effectiveness of the control strategy are both proven.

This study focuses on the formation control of four robots used for the on-orbit construction of a large solar sail. The solar sail under consideration is non-spinning and has a 1 km2 area. It includes a hub as the central body and four large booms supporting the lightweight films. Four formation operating space robots capable of walking on the boom structure are utilized to deploy the sail films. Because of the large size and mass of the sail, the robots should remain in formation during the sail deployment to avoid dramatic changes in the system properties. In this paper, the formation control issue of the four robots is solved by an adaptive sliding mode controller. A disturbance observer with finite-time convergence is embedded to improve the control performance. The proposed controller is capable of resisting the strong uncertainties in the operation and do not require the accurate parameters of the system. The stability is proven, and numerical simulations are provided to validate the effectiveness of the control strategy.