Two-time-scale control of a multirotor aircraft for suspended load transportation

This paper presents a trajectory control strategy for a multirotor aircraft carrying a suspended load. The load is modeled as a pendulum connected by a rigid link to the center of gravity of the vehicle. Starting from the dynamic equations describing the motion of the coupled vehicle slung-load systems, a nonlinear controller is proposed that simultaneously performs trajectory tracking and payload swing damping. Controller gains are chosen so that the system exhibits a two-time-scale behavior, with fast dynamics for the pendulum and slow dynamics for the positioning task. Under these conditions, the basic results of singular perturbation theory are evoked for both the proof of stability and the preliminary design of control gains. Results of numerical simulations are provided in order to assess the stability and performance of the considered approach.