Modeling and control of an agile tail-sitter aircraft

TL;DR

This paper develops a comprehensive model and control strategy for an agile tail-sitter aircraft capable of seamless helicopter and fixed-wing operations, including aerodynamic analysis, observer design, and transition control.

Contribution

It introduces a novel finite-time convergent observer for nonlinear term estimation and a quaternion-based controller for smooth mode transition.

Findings

Successful modeling of co-axial propeller aerodynamics

Effective estimation of uncertainties and disturbances

Smooth mode transition achieved with the proposed control method

Abstract

This paper presents a model of an agile tail-sitter aircraft, which can operate as a helicopter as well as capable of transition to fixed-wing flight. Aerodynamics of the co-axial counter-rotating propellers with quad rotors are analysed under the condition that the co-axial is operated at equal rotor torque (power). A finite-time convergent observer based on Lyapunov function is presented to estimate the unknown nonlinear terms in co-axial counter-rotating propellers, the uncertainties and external disturbances during mode transition. Furthermore, a simple controller based on the finite-time convergent observer and quaternion method is designed to implement mode transition.