Model based robust control and automation design for a micro-gravity enabling multi-rotor test bed

This paper addresses the design of a robust control law and an automation strategy for a multi-rotor to enable microgravity. A 1-D vertical maneuver is proposed for the multi-rotor to perform such that the on-board payload experiences microgravity for a specified time period. An automation strategy is also proposed so that the multi-rotor executes this maneuver au-tonomously. To verify the proposed automation strategy through simulations, a mathematical model that accurately predicts the multi-rotor behavior is developed by incorporating the high axial velocity effects–drag and rotor thrust variation due to axial airflow–on the multi-rotor. To successfully execute the proposed maneuver, a traditional control law such as PID will not suf-fice, as the drag force and rotor-aerodynamic interactions are non-linear in nature. Therefore, a robust controller FL-SMI—sliding mode control (with integral action) on feedback linearized multi-rotor acceleration dynamics—is designed to ensure a constant microgravity. A theoretical proof that the resultant feedback linearized dynamics is invariant to model parameter estimation errors is provided. The 6-DoF simulations presented demonstrate the efficacy of the proposed automation and control strategies in providing constant microgravity for 2 seconds. Finally, to validate the robustness of FL-SMI controller, its microgravity acceleration response is compared with PID and FL-PID responses.