Mid-Ranging Control Concept for a Multirotor UAV with Moving Masses

This paper addresses the problem of actuators saturation that occur when one applies a moving mass concept to control the attitude of a mul-tirotor UAV. In particular, we propose to combine the moving mass control (MMC) with rotors' variations in a paradigm known as a mid-ranging control. We show that this control structure ensures reference tracking and disturbance rejection with the moving masses operating in the middle of their range, which eventually reduces the possibility to violate their saturation limits. We also address the stability and design of the proposed controller by employing Routh-Hourwitz criterion and root-locus analysis. The controller is verified within a simulation environment, where we test its performance and compare it with a basic MMC concept under various disturbances. Finally, we present experimental results that we obtained with a modified ArduCopter vehicle, which serves as an experimental platform for the MMC verification.