Longitudinal control of a fixed wing UAV

Abstract

This article presents an approach to the mathematical model of a fixed wing unmanned aerial vehicle prototype. The model is split in two different parts, related to the longitudinal and lateral stability, respectively. For this, Newton-Euler formulation is used as well as basic aerodynamic theory. Aerodynamic coefficients, inertias and characteristic points of the aircraft are obtained through simulations with an open-source software called XFLR-5, and the physical parameters of the model match the prototype's. Then, a longitudinal control strategy describes the altitude control in a cascade architecture, whose inner loop conveniently manoeuvres the pitch angle by acting on the symmetric flag deflection. Frequency domain techniques are used to design PID controllers.

Immersion and invariance control for Euler angles of a fixed‐wing unmanned aerial vehicle

“…Different techniques are developed to control fixed‐wing UAVs in the literature. Traditionally, linearized models of aircraft dynamics are used in several studies based on Proportional‐Integral‐Derivative control (PID) [1], Linear Quadratic Regulator control (LQR), and Linear Quadratic Gaussian control (LQG) [2]. Besides, based on nonlinear models, there are studies that utilize model predictive [3], H ∞ [4–6], dynamic inversion [7], disturbance observer‐based [8], sliding mode [9], adaptive sliding mode [10], adaptive model predictive [11], and adaptive backstepping control methods [12–16].…”

“…Fixed‐wing UAVs have nonlinear dynamics. However, as previously mentioned, there are some studies that utilize linear control techniques like PID and LQR control for flight control of the system by linearizing its dynamics at specific operating points [1,2]. Since these linear controllers are designed based on approximated linear models, stability and precise control are not guaranteed outside of the operating point.…”