Optimal Tuning of Non-integer Order Controllers for Rotational Speed Control of UAV’s Propulsion Unit Based on an Iterative Batch Method

Abstract

The paper presents an optimal batch method for tuning easy-to-implement controllers with fixed parameters, which are widely used to control propulsion units in unmanned aerial vehicles (UAVs) in rotational speed control task of the propellers. As a result of the latter, this method might be used to satisfy thrust demand defined by profile of a reference thrust force. In the proposed approach, tuning of a fractional-order proportional-integral controller (FOPI) is performed on the basis of a linear model of the propulsion unit. By using Hermite-Biehler and Pontryagin theorem, the range of controller parameters ensuring stability of the closed-loop system (rotational speed control) is obtained. In this range, or withing the area of fail-safe parameters, the optimal choice of gains of a FOPI controller is performed, on the basis of the predefined cost function minimized off-line by a zero-order algorithm. In the paper, sample simulation results are presented, which have been obtained for the model of the propulsion unit used in multirotor UAVs. These results refer to data obtained in prior with a proportional-derivative-integral (PID) controller, CDM controller tuned by Coefficient Diagram Method, near-to-optimal fractional-order PID controller tuned by Best-from-the-best procedure and FOPI controller tuned by SCoMR-FOPI procedure.