Unified motion control for multi-lift unmanned rotorcraft systems in forward flight

SALINAS, LUCIO; GIMENEZ ROMERO, JAVIER ALEJANDRO; GANDOLFO, DANIEL C.; ROSALES, CLAUDIO; CARELLI, RICARDO

IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Año: 2023 vol. 31 p. 1607 - 1621

1063-6536

Interest in multi-lift rotorcraft systems has re-emerged in recent years to overcome some of the problems in single unmanned aerial vehicle handling and delivery systems. Using multiple unmanned rotorcrafts (URs) the load weight can be evenly distributed among the vehicles, extending the flight time and therefore increasing the working distance of such systems. Moreover, with a slung-load configuration, bigger-size packages with complex shape and equipment that may interfere with the on-board electronics can be carried. In this context, this paper presents a payload-based unified motion control that allows any number of URs to cooperatively transport a slung load in forward flight. The motion control comprises path-following and trajectory-tracking algorithms, considers obstacle avoidance, implements a specific strategy for load weight distribution (load equalization) by regulating the relative altitude of each UR, and is robust to disturbances such as wind. In addition, this work shows that load equalization is essential for slung-load cooperative transport, especially in forward flight. The controller´s stability is analytically studied and the good performance of the system is demonstrated through exhaustive simulations using validated dynamic models for mini-helicopters, cables and payload. Finally, the relation between load weight and number of URs is analyzed considering several scenarios.