Antisway Control of a Multirotor with Cable-Suspended Payload

This brief presents a new trajectory generation and an effective antisway tracking control (ATC) method for a multirotor unmanned aerial vehicle (UAV) with a cable-suspended payload. The UAV transportation system has been developed due to its ability to easily deliver small packages. However, existing methods lack research on transient response accompanied by aggressive rotation of the UAV and inevitable payload swing. Unfortunately, these motions become intensified when the input is dynamically unfeasible, such as step-like changes. Trajectory generation to minimize the swing motion provides a dynamically feasible trajectory between waypoints. The proposed method provides fast settling time with remarkably little payload swing. In addition, the ATC is developed on the basis of linear-quadratic (LQ) control to deal with motion coupling issues. A payload state estimator is also designed that requires no sensor for the payload. Finally, the performance of the proposed method is verified by numerical simulation and experimental results that show the possibility of safe and fast transportation with a minimal swing.