Cooperative Transportation of a Cable-Suspended Load using Rotorcraft: A Minimal Swing Approach

Abstract

In this paper cooperative transportation of a cable-suspended load by two rotorcraft is analyzed. A control law is proposed that allows the agents in the formation to simultaneously perform trajectory-tracking, formation geometry keeping, and payload swing stabilization. The controller is generated for a system made of three point masses and a set of two linear-elastic cables, according to Newton-Euler approach. A proof of local exponential stability is derived for closed-loop system with the requirement that the loaded formation exhibits a two-time-scale behavior: the fast dynamics develops with formation geometry stabilization and payload swing damping while the slow dynamics characterizes the trajectory-tracking task. Validation is performed in a realistic simulation scenario where multirotors are modeled as rigid bodies under the effect of external disturbances and rotor-generated forces and moments obtained by Blade Element Theory approach. The proposed method has the merit of relative simplicity and is shown to significantly improve vehicle flying qualities while minimizing hazardous payload oscillations.