This study proposes a combined proportional–integral–derivative (PID) flight control strategy within a fixed-wing unmanned aerial vehicle (UAV). This type of UAV has high speed and high maneuverability. Considering relatively simple implementation, low computational effort,
and intuitive operation, the classic PID controller is still popular but imperfect because of several well-known reasons. A number of practical and improved PID control methods, such as integral separation, anti-windup, and gearshift integral, are always used separately in many control fields.
In this study, the combined PID flight control strategy is designed and applied to promote the classic PID control performance, along with the aforementioned methods, to fixed-wing UAV. The proposed approach adopts different controls depending on the deviation outputs and UAV physical limitations.
The design flowchart and flight control loop are also presented. The combined PID flight control strategy can achieve a smaller overshoot and a shorter settling time than the conventional PID control. Comparable typical flight parameter tracking results (i.e., pitch, roll, altitude, and path
angle) from principle simulation, hardware-in-the-loop simulation, and real flight experiment validate the efficacy and practicability of the combined PID flight control strategy.
