Roll-channel fractional order controller design for a small fixed-wing unmanned aerial vehicle

Low-cost small unmanned aerial vehicles (UAVs) attracted researchers and developers around the world for use in both military and civilian applications. However, there are challenges in designing stable and robust flight controllers that handle the UAV model and environmental uncertainties. This paper focuses on the design and implementation of a roll-channel fractional order proportional integral (PIλPIλ) flight controller for a small fixed-wing UAV. Time domain system identification methods are used to obtain a simple auto-regressive with exogenous input (ARX) model of the UAV roll-channel. A new fractional order PI controller design method is introduced based on the identified simple model. The fractional order PIλPIλ controller outperforms the optimized traditional integer order proportional integral derivative (PID) controller due to the fractional order introduced as a design parameter. The simulation results show the effectiveness of the proposed controller design strategy and the robustness of fractional order controller under conditions of wind gusts and payload variations. Further real flight test results are also provided to show the advantages of the proposed PIλPIλ controller.