Flight Mode Transitions Research Articles

Nonlinear Robust Flight Mode Transition Control for Tail-Sitter Aircraft

In this paper, the nonlinear robust control problem for tail-sitter aircraft in flight mode transitions is addressed. The problem is challenging due to the nonlinearities and uncertainties including parametric uncertainties, unmodeled uncertainties, and external disturbances involved in the vehicle dynamics during the mode transitions. The proposed controller is designed in two steps: first, the dynamic inversion technique is adopted to establish a tracking error model; then, for the tracking error model, a robust controller consisting of a nominal controller and a robust compensator is designed. The nominal controller is designed to obtain the desired tracking performances for the nominal system. The compensator is introduced to restrain the effects of uncertainties. Tracking errors of the closed-loop system are proven to converge into a neighborhood of the origin in a finite time. Simulation results are presented to demonstrate the advantages of the proposed controller, compared with the controller based on the standard loop-shaping method.

Design of a Symmetrical Quad-rotor Biplane Tail-Sitter Aircraft without Control Surfaces and Experimental Verification

This paper presents the design of a symmetrical quad-rotor biplane tail-sitter VTOL UAV (Vertical Take-off and Landing Unmanned Aerial Vehicle) which is composed of four rotors and two symmetrically mounted fixed wings. This aircraft achieves high accuracy in the attitude control and smooth flight mode transition with four rotors rather than the conventional VTOL UAVs using control surfaces. The proposal of angled rotor mounting is adopted to address the issue of insufficient yaw control authority. The layout of symmetrically mounted fixed wings makes the aircraft have capability of rapid bidirectional flight mode transition to improve maneuverability. To validate the performance of the aircraft, simulation and flight experiments are both implemented. These results show that the aircraft has a rapid yaw response under condition of the stable attitude control. In comparative experiment, it is shown that the aircraft is more flexible than other similar configuration of aircrafts. This symmetrical quad-rotor biplane tail-sitter VTOL UAV will have a wide range of potential applications in the military and civilian areas due to its superior performance..

The hybrid bio-inspired aerial vehicle: Concept and SIMSCAPE flight simulation.

This paper introduces a Silver Gull-inspired hybrid aerial vehicle, the Super Sydney Silver Gull (SSSG), which is able to vary its structure, under different manoeuvre requirements, to implement three flight modes: the flapping wing flight, the fixed wing flight, and the quadcopter flight (the rotary wing flight of Unmanned Air Vehicle). Specifically, through proper mechanism design and flight mode transition, the SSSG can imitate the Silver Gull's flight gesture during flapping flight, save power consuming by switching to the fixed wing flight mode during long-range cruising, and hover at targeted area when transferring to quadcopter flight mode. Based on the aerodynamic models, the Simscape, a product of MathWorks, is used to simulate and analyse the performance of the SSSG's flight modes. The entity simulation results indicate that the created SSSG's 3D model is feasible and ready to be manufactured for further flight tests.

Transition Management for the Smooth Flight of a Small Autonomous Helicopter

This work is centered in the definition of a transition management system for a small autonomous helicopter based on trajectory smoothing and a finite state machine (FSM). A smooth flight schedule decreases transients originated by direction changes and flight mode transitions (e.g., horizontal flight to hover mode). Although previous works have presented trajectory generation and FSM oriented controls, no previous studies have mixed these approaches in a single framework together with speed transitions. The proposed methods are validated in simulation with a realistic dynamic model of a small helicopter.

Terminal-Area Aircraft Tracking Using Hybrid Estimation

A bottleneck to the flow of air traffic is in the traffic around airports. Accurate tracking of aircraft movements around airports is important to improve traffic capacity and safety. We propose a hybrid estimation algorithm that uses the knowledge of departure or arrival aircraft flight plans and nominal flight profiles to improve tracking of aircraft movements around airports. The algorithm also provides an accurate estimation of aircraft flight modes that is often used in conflict detection, intent inference, and trajectory prediction algorithms. In the algorithm, we first develop a methodology to model flight mode transitions based on typical aircraft landing profiles, takeoff profiles, and standard flight routes around airports. Based on the model, we derive a conditional mode transition matrix that is dependent (or conditioned) on the continuous state of the aircraft. The aircraft-tracking problem is then solved using a hybrid estimation algorithm. We also present an analytical result that reduces the dimension, and hence the computational cost, of a multivariate integral that arises due to the continuous-state-dependent mode transition matrix. We present two simulation examples to illustrate the performance of our aircraft-tracking algorithm.

A Study on Transient Performance Characteristics of the Canard Rotor Wing Type Unmanned Aerial Vehicle Propulsion System During Flight Mode Transition

A propulsion system of the CRW (Canard rotor wing) type UAV (unmanned aerial vehicle) was composed of the turbojet engine, exhaust nozzles (including some tip jet nozzles and a main nozzle), and the duct system (including straight ducts, curved ducts, and master valve). The CRW-type UAV has three different flight modes, such as the rotary wing mode for takeoff and landing, the high-speed forward flight mode with the fixed wing, and the transition flight mode between the previously mentioned two flight modes. In order to evaluate transient performance characteristics of the CRW-type UAV propulsion system during flight mode transition, the propulsion system was modeled using SIMULINK®, which is a user-friendly graphical-user-interface-(GUI) type dynamic analysis tool provided by MATLAB, in this study. The transition flight mode between the rotary wing mode and the fixed wing mode was simulated by considering area variation of the master valve and the main exhaust nozzle. In order to verify acceptability of the main turbojet engine model, performance simulation results using SIMULINK were compared to results using the commercial program GSP. Through this simulation, proper operation of the master valve and the variable area main nozzle can be found for safe flight transition. Therefore, performance characteristics were investigated depending on various angle positions of the master valve.