Transfer from existing flight control of under-actuated aerial vehicles to interaction control of aerial slung load systems

This paper investigates a framework to design the interaction control of the aerial slung load system which is composed of an underactuated aerial vehicle, a cable, and a load. Instead of designing new controller for the system, we show that the interaction control of the system can be totally transferred from the controllers for under-actuated aerial systems. Selecting the differentially at output as the configuration, the equation of motion of the two systems is written in the same format. The flight controller of the under-actuated aerial vehicle is thus migrated to control the aerial slung load system. We adopt the admittance filter to generate the compliant trajectory of the load under external interaction force. Furthermore, from the boundedness of the vehicle attitude tracking error and the external force estimation error, the convergence of the entire system is proved. Based on this theoretical foundation, an example interaction controller for the aerial slung load is derived from an existing flight controller directly, by including an external force estimator. The example controller is demonstrated in the numerical simulation.