Robust nonlinear control of the longitudinal flight dynamics of a circulation control fixed wing UAV

Circulation Control (CC) is an effective technique to increase lift and improve aerodynamic efficiency of Unmanned Aerial Vehicles (UAVs). This paper introduces a novel, robust nonlinear controller for the longitudinal flight dynamics of a CC-based fixed-wing Unmanned Aerial Vehicle (UC²AV) that operates in cascaded fashion and takes into account changing mass. The controller consists of a dynamic inversion inner-loop and a μ-synthesis outer-loop controller. CC introduces changes of the aerodynamic coefficients that are difficult to determine using strict mathematical formulas. This creates a specific type of model uncertainty in the UC²AV model, which is tackled by the use of μ-analysis. Simulation results demonstrate the efficacy of the proposed control scheme and the ability of the U C² AV to adapt to challenging CC-on-demand scenarios. The technique can be generalized and applied on CC-based and conventional UAVs, seeking to address uncertainty challenges regarding the aircraft's aerodynamic coefficients.

I. Introduction

Research conducted on navigation and control of Unmanned Aerial Vehicles (UAVs) has witnessed exponential growth over the last two decades and it is expected to dominate the Unmanned Aviation field in the forthcoming years. The term Unmanned Circulation Control Aerial Vehicle (UC² AV) refers to a unique kind of UAV design, which was developed and tested in the Unmanned Systems Research Institute of the University of Denver and it is the first of its kind [6].