DESIGN AND DEVELOPMENT OF CONTROL SYSTEMS FOR UAVS

Abstract

In this work, the closed-loop control of a fixed-wing UAV system was designed and a mathematical model was derived and stabilized using the PID controller with the Feed-forward compensation method to reduce the non-minimum phase. In the first part of the thesis project, a comprehensive systematic literature review on general UAV structures and their types, as well as their application was presented. Later the overall aircraft dynamics alongside the generalized roll angle model of a fixed-wing was pointedly described. Moreover, the nonlinear dynamics of both matrix differential equations and vector forms (traditional state-space form) were derived. After modelling the system, the closed-loop control law was designed using the PID controller in MATLAB script. The reference generation was performed by using the two types of reference: simple (unit step signal and ramp) and complex (sine wave, square wave and their combination). Generated reference points were applied to test the controller behavior in various cases. The obtained closed-loop model had a negative transient behavior, which means it has a positive zero and caused the non-minimum phase system with even-numbered RHP (Right-hand plane) zeros. To reduce it, the various methods were tested and among them, the feed-forward compensation method showed the best performance in terms of usage, easy implementation, settling time, overshoot, and margin values.