Double-Hoist Dynamics and Oscillation Control of a Quadcopter Carrying a Swinging and Twisting Load

Quadcopters can serve as aerial cranes that are able to suspend large-size loads below the fuselage for material-handling services. Double-hoist mechanisms help quadcopter to transport bulky loads effectively. However, double-hoist mechanisms exhibit strong coupling effect among the quadcopter’s attitude, load swing, and load twisting. Different from the single-hoist mechanisms, no effects have been directed at quadcopter slung loads with double-hoist mechanisms. A novel nonlinear dynamics model of a quadcopter carrying a distributed-mass load by double-hoist mechanisms is given in this paper. This explicit model captures the coupling between the quadcopter and load motion. Then a novel control method is proposed to reduce the swing and twisting of the load simultaneously. The simulation results illustrate that the control method succeeds in limiting the unwanted oscillations of quadcopter attitudes, load swing and twisting.