2016, Controller for a Load Suspended From an Aerial Vehicle
Over the last years, unmanned quadcopters and other multicopters have been used
frequently in research in various areas including many aspects of automatic control. Multicopters are controlled by adjusting the speed of the propellers individually, but what happens when you attach a load to the vehicle with a rope?
Manuel Herzog's master thesis "Design, Implementation and Analysis of a Controller for a Load Suspended From an Aerial Vehicle" presents a trajectory tracking controller structure for a system composed of a load and an aerial vehicle, which are connected by a rope. The main goal is to design a controller that guarantees that the load tracks a desired trajectory asymptotically. The load is modeled as a point mass while the aerial vehicle is assumed to be fully actuated. The load and the aerial vehicle are connected via a rope like structure of fixed length that can only exert tensile forces along its orientation. This system can be transformed into a form that resembles systems used to describe underactuated aerial vehicles. A backstepping procedure is used to design a nonlinear control law, which is based on a controller for a double integrator. A bounded control law for double integrators can be found such that the load converges to the desired trajectory for initial positions that are arbitrarily far away. The proposed controller structure has been verified both in simulations and with experiments using quadcopters at the Smart Mobility Lab at KTH.
