Configuration Optimization and Distributed Formation Control for Tethered Multirotor UAS

This article improves the robustness of tethered multirotor unmanned aircraft systems (UASs) through configuration optimization and controller design. Capacity margin and stiffness matrix are defined to measure the robustness of the system. The relationship between capacity margin and system configuration is analyzed based on a new optimization method. Moreover, the mathematical expression of system stiffness matrix argument with configuration is derived. Based on these two relations, the optimal configuration is determined to strengthen the robustness of the system. Under composite disturbances, it is not trivial to maintain the designed optimal configuration. Thus, a disturbance observer (DO) is developed to eliminate the disturbance generated by the tension force, which is a constant or harmonic signal. In addition, a fixed-time extended state observer (FTESO) is designed to mitigate the external aerodynamic force acting on the UAS. Accordingly, a distributed formation control algorithm based on the designed DO and FTESO is constructed for formation tracking control. Finally, the indoor experiments are demonstrated to validate the proposed strategy.