Achievable Thrust Expansion Control at Current Saturation of Variable-Pitch Propeller for Drones

Abstract

On drones, which have become popular in recent years, the installation of variable pitch propellers is being considered and researched for industrial applications such as large drones and flying mobility. A variable-pitch propeller not only provides higher responsiveness than control by rotational speed alone, but also expands the thrust that can be achieved by optimizing the combination of rotational speed and pitch angle. In this paper, it is experimentally verified that, in the current saturation region of a variable-pitch propeller motor, the control method using simple frequency-separated command values for rotational speed and pitch angle causes an inverse response in transient conditions, and we attempt to explain this response by a linearized model including unstable zero. Basing on the model, we proposed a control method in which the pitch angle is controlled by a first-order filter while the maximum current is applied. The proposed method enables control design with a trade-off between initial undershoot and settling time with one parameter. The effectiveness of the proposed method is verified by simulation and experiment.