Practical Complete Tracking Through Gimbaled Unidirectional Actuation with Application to Multirotor UAVs

Overview & Synopsis

This paper addresses the problem of practical tracking control for robotic vehicles with gimbaled unidirectional actuators, with special application to multirotor unmanned aerial vehicles. A widely recognized obstacle to tracking control for multirotors is the free-fall singularity --- when a multirotor is commanded to free fall, the vehicle's target attitude becomes undefined. This singularity is a pathology pertinent to all robotic vehicles with gimbaled unidirectional actuators. This paper considers the general theoretical problem for vehicles with gimbaled actuators. Starting from a baseline robust controller that assumes unconstrained inputs, we redesign the control law to be compatible with the gimbaled actuator. This is accomplished by driving the output of the gimbaled actuator to a ball centered at the target input value. The baseline controller's tracking guarantees are recovered in a practical sense. We apply our results to synthesize a global practical complete position tracking controller for multirotor unmanned aerial vehicles. The theory is demonstrated in simulation.