A practical approach to cooperative aerial transportation of a load by UAVs

Sammanfattning: A path following controller for a system, composed of a single cylindrical load and connected totwo unmanned aerial vehicles by two cables, is designed. The load is modeled as a uniformlydistributed mass while the aerial vehicles are assumed to be fully actuated point masses. Theinputs to the UAVs-load system are the 3D force inputs of each UAV. During this report theassumption that there are not input disturbances has been made. An additional assumption isthat the load and the aerial vehicles are connected by cables of xed length, which is equivalent toconnection by massless rigid links while under tensile forces. Next, the state space is transformedto another description that is locally full state controllable. The system is linearized around aNominal Equilibrium in which the bar is horizontal and the cables vertical. The linearized systemundergoes a similarity transformation which decouples it into three 2nd and three 4nd ordersubsystems. A stabilizing feedback controller is then designed for each subsystem independently.This stabilizing controller can be applied to every nominal equilibrium. Then the controller istested over model uncertainties and integral actions are also added to it. A practical controlpolicy for trajectory tracking is designed based around a zero equilibrium. In detail, a trajectorythat comprises of a series of Nominal Equilibria and respects the stability characteristics of thecontroller can then be tracked. All the proposed control algorithms are validated by simulation.