Abstract

This article studies the model, control and simulation on transition flight of a novel tail-sitter with vertical takeoff and landing capability. The proposed tail-sitter adopts an innovative varying fuselage shape design to break the technical bottleneck in the balance of efficient horizontal flight and agile vertical flight. Overset grids and computational fluid dynamic methods are used to explore the vehicle’s prestall aerodynamics, which are relative to not only the angle of attack and sideslip angle but also to the varying angle between two rear fuselage’s parts. High angle of attack aerodynamics based on the improved Viterna and Corrigan stall model is also established for this novel tail-sitter. Meanwhile, an accurate model of the propeller is tested in a wind tunnel. Combining the forces and moments generated by propellers, aerodynamics and gravity, a 6DoF nonlinear time-varying dynamic model is built. A robust controller based on incremental dynamic inversion method is designed for this tail-sitter, which is good at dealing with uncertainties and external forces. Nominal and model mismatch conditions are simulated to verify the controller’s performance. Different varying strategies for the mechanism are analyzed during the transition flight. Simulation results show that this novel tail-sitter can transform between vertical and horizontal flight mode easily and the varying strategy related to pitch angle is a prior choice for transition flight.

Highlights

  • Unmanned aerial vehicle (UAV) technology has developed rapidly and been applied in various fields such as photography, cargo delivery, environmental observation, etc

  • Reference [1], [2] combining the long endurance and high speed of the fixed-wing and vertical take-off and landing (VTOL) ability of rotorcraft, hybrid type UAVs have attracted a lot of attention in recent years

  • Compared to the tilt wing or tilt rotors, most of tail-sitters are less controllable in pitch motion during low-speed flight conditions, for example the early stage of the forward transition flight

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Summary

INTRODUCTION

Unmanned aerial vehicle (UAV) technology has developed rapidly and been applied in various fields such as photography, cargo delivery, environmental observation, etc. Compared to the tilt wing or tilt rotors, most of tail-sitters are less controllable in pitch motion during low-speed flight conditions, for example the early stage of the forward transition flight. A safe transition flight is necessary for the hybrid UAV During this process, the pitch angle’s variation is close to 90◦, which results in strong nonlinearity of the dynamic model and difficulty in controller design. Many researches have tried to using INDI based controller in the transition flight control of hybrid UAVs. For example, a robust transition controller for a fly-wing tail-sitter based on INDI is designed to deal with model uncertainties and validated by simulations under a variety of conditions [32]. The main contribution of this article is the validation of a novel tail-sitter UAV’s transition flight capability and the effectiveness of modelling and controlling methods used on it.

OBJECT DESCRIPTION
MOTORS AND PROPELLERS
SIMULATION AND VALIDATION
NOMINAL CONDITION
Findings
VARYING STRATEGIES
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