Passivity-Based Control of Multiple Quadrotors Carrying a Cable-Suspended Payload

In this article, a new passivity-based controller is proposed for stable cotransportation of a cable-suspended payload by a number of quadrotors. Nominal proportional–derivative position controllers with desired acceleration feedforward are augmented with time-varying dissipative terms to account for the drones' underactuation. A storage function is defined that includes terms inspired by the kinetic and potential energies of the system components as well as virtual energy of the controller. A time-domain passivity observer is used in conjunction with an adaptive dissipative term to ensure that the value of the storage function is continuously decreased and, hence, guarantees closed-loop stability. Moreover, barrier Lyapunov functions are employed to avoid interdrone collisions. The proposed controller makes no assumption about and requires no knowledge of the cables' tension status. Additionally, it requires no measurement from the payload. The cables can be attached to the quadrotors and the payload at arbitrary points. Experiments with a system of three quadrotors and a cable-suspended payload demonstrate the effectiveness of the proposed approach.