Accurate positioning of a payload suspended to a quadrotor unmanned aircraft

This paper presents a trajectory control strategy for a quadrotor carrying a suspended load. Following the derivation of a set of simplified equations of motion for the coupled vehicle slung-load systems, the inverse simulation method based on an integration algorithm allows for the determination of the control action to track an assigned trajectory, with the pendular payload acting as a disturbance on vehicle dynamics. Results concerning two situations relevant from the perspective of practical applications, namely payload in the air and towed in water, are presented and discussed. The approach appears suitable and effective for the selection of feedforward control laws that account of hanging load loads, either as a preliminary step in control system design or to assess vehicle performance limits in specified missions.