Energy Optimal Control Allocation in a Redundantly Actuated Omnidirectional UAV

Abstract

This paper presents a novel actuation model and control allocation strategy for a redundantly-actuated multirotor unmanned aerial vehicle (UAV), referred to as the omnicopter. With an unconventional configuration, the omnicopter's eight propellers are able to produce all the six components of net force/torque, with two degrees of actuation redundancy. This enables the vehicle to execute motion trajectories unattainable with conventional underactuated multi-rotors. A new inverse actuator model is proposed that accounts for the significant interactions between propeller airflows by relating their output thrust forces to their input motor commands. Actuation redundancy is resolved by solving a convex constrained optimization problem. Its solution yields the most power efficient set of propellers thrusts that would produce a required net force/torque, while respecting the propeller thrust limits. When the required force/torque is infeasible due to the thrust limits, the solution would minimize the norm of the error between the desired and actual net force/torque vectors. Experimental results demonstrate the effectiveness of the proposed model and control allocation strategy.