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1

Concept of tiltrotor UAV control system

Ciopcia M., Szczepański C.

Journal of KONES

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2017

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Vol. 24, No. 1

83--89

EN

Nowadays, civil UAV industry market grows rapidly. This expansion is followed by the new requirements and expectations against UAVs, which force their constructors to look for less typical solutions. Expected long time endurance and range are the typical examples of such expectations. Clients are often looking for UAV with VTOL ability and time of flight much greater than 30 minutes and long range. They want to inspect large areas, i.e. between major cities without need of paying for building and maintaining developed aircraft infrastructure. Example of UAV with low infrastructure requirements are multirotors. Major disadvantage of them is short flight time. Elongating time of flight is hard to achieve by classical multirotor with standard Li-Pol batteries available on the market. They have too low energy density in currently used technology. Alternative power solutions, like fuel cells, have low financially rewarding factor, which cause whole projects to be unprofitable. Foregoing circumstances force engineers to find less usual ways for improvement energy efficiency, which will cause extending the time and range of flight. One of them is a tiltrotor. Tiltrotors are hybrid solutions – they combine airplane and multirotor capabilities to achieve features, which exclude each other in classical constructions. Aircraft-like wing make it able to use its lift-to-drag ratio to achieve energy savings, higher top speed and extended range in comparison with multirotors. UAV is also equipped with multiple multirotor-style engines with additional capability to rotate itself in pitch. In horizontal engine position, vehicle behaves like classical multirotor – allowing pilot to hover and perform VTOL manoeuvres. When engines are tilted to vertical position, whole UAV get performance similar to airplane – high speed and flight endurance. In the other hand, practical implementation of tiltrotor solution can be problematic: simulation, steering and controlling such aircraft in transition state are complex tasks. Moreover, designed aircraft should follow major rule connected with multirotors: Should have as simple, robust mechanical design as it can. Proposed article will concentrate on concept and preliminary design of fly-by-wire steering system with unique properties for tiltrotor. One of such properties will be unification of steering method – which eliminates need for switch and setting initial conditions for control subsystems, when flight procedure requires changing flight mode. Second important improvement will be possibility to use transitional states as intermediate state between propeller driven fly and gliding – which allow achieving wide spectrum of flight speeds. Moreover, huge number degrees of freedom (at least 9) create new opportunities for steering optimization. Extensive thrust vectoring abilities of such UAV could not only implicate substantial efficiency improvement of multirotors, but also improve its manoeuvrability. The article will focus on basic concepts of kinematics, steering of such UAV and show proposition of energyusage oriented optimization for its control trajectories. To let mechanical design be simple, all control and steering methods will be implemented in software, which will implicate complex structure of steering system. Overcoming complexity of software should be profitable in relation to expected improvements of UAV capabilities.

2

Output Error Method for Tiltrotor Unstable in Hover

Lichota P., Szulczyk J.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 1

23--36

EN

This article investigates unstable tiltrotor in hover system identification from flight test data. The aircraft dynamics was described by a linear model defined in Body-Fixed-Coordinate System. Output Error Method was selected in order to obtain stability and control derivatives in lateral motion. For estimating model parameters both time and frequency domain formulations were applied. To improve the system identification performed in the time domain, a stabilization matrix was included for evaluating the states. In the end, estimates obtained from various Output Error Method formulations were compared in terms of parameters accuracy and time histories. Evaluations were performed in MATLAB R2009b environment.

3

Helicity of Convective Flows from Localized Heat Source in a Rotating Layer

Sukhanovskii A., Evgrafova A., Popova E.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 2

177--188

EN

Experimental and numerical study of the steady-state cyclonic vortex from isolated heat source in a rotating fluid layer is described. The structure of laboratory cyclonic vortex is similar to the typical structure of tropical cyclones from observational data and numerical modelling including secondary flows in the boundary layer. Differential characteristics of the flow were studied by numerical simulation using CFD software Flow Vision. Helicity distribution in rotating fluid layer with localized heat source was analysed. Two mechanisms which play role in helicity generation are found. The first one is the strong correlation of cyclonic vortex and intensive upward motion in the central part of the vessel. The second one is due to large gradients of velocity on the periphery. The integral helicity in the considered case is substantial and its relative level is high.

4

Tiltrotor modelling for simulation in various flight conditions

Miller M., Narkiewicz J.

Journal of Theoretical and Applied Mechanics

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2006

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Vol. 44 nr 4

881-906

EN

A computer model of a tilt-rotor has been developed for calculating performance, simulating flight and investigating stability and control. The model is composed of a fuselage, wings, an empennage, engine nacelles and rotors. Tiltrotor equations of motion have been obtained by summing up inertia, gravity and aerodynamic loads acting on each part of the aircraft. Aerodynamic loads at wings, empennage and rotor blades have been calculated using a quasisteady model. For rotor induced velocity, the Glauert model has been used. The influence of the rotor inflow wing and empennage aerodynamic loads has been found using the actual value of induced velocity. The computer program of tilt-rotor model has been developed in the MatLab environment. The sub-programs for load calculation have been supplemented by modules for calculation of trim states and stability and control matrices. During the first stage of model investigation, steady flight conditions were calculated, which gave insight into rotorcraft behaviour and model quality.

PL

Opracowano symulacyjny model statku powietrznego typu tiltrotor przeznaczony do symulacji lotu oraz analizy osiągów, stabilności i sterowania. Model wiropłata złożony jest z kadłuba, usterzenia ogonowego, gondoli silnikowych i wirników. Równania ruchu zostały uzyskane przez sumowanie obciążeń od sił bezwładności, grawitacyjnych i aerodynamicznych działających na każdy element statku powietrznego. Obciążenia aerodynamiczne skrzydeł, stateczników i łopat wirników zostały obliczone z zastosowaniem quasistacjonarnego modelu opływu. Do wyznaczania prędkości indukowanej wirników zastosowano model Glauerta. Wpływ strumienia zawirnikowego na skrzydła i stateczniki jest obliczany z wykorzystaniem aktualnej wartości prędkości indukowanej wirników. Program do modelowania wiropłata został opracowany w środowisku MatLab. Program zbudowany jest z modułów obliczeń obciążeń poszczególnych elementów wiropłata, które wykorzystywane są również do wyznaczania warunków lotu ustalonego, stateczności i sterowności. Podczas pierwszego etapu badań wyznaczono warunki ustalonego lotu tiltrotora w różnych konfiguracjach, co pozwoliło zbadać zachowanie i potwierdzić poprawność modelu

5

Symulacja numeryczna podstawowych manewrów wiropłata typu tiltrotor

Miller M., Narkiewicz J.

Prace Instytutu Lotnictwa

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2004

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Nr 2-3 (177-178)

148-155

PL

Opracowano symulacyjny model statku powietrznego typu tiltrotor dla potrzeb analizy stabilności i sterowania. Statek powietrzny składa się ze sztywnych elementów: kadłuba, skrzydeł, gondoli silnikowych i wirników, dla których wyznaczane są obciążenia masowe i aerodynamiczne. W tej pracy przedstawiono metodę wyprowadzania równań ruchu i wstępne wyniki symulacji.

EN

A computer model of a tiltrotor is under development for calculating performance and simulating control behaviour. A generic approach is assumed in the model building. An aircraft is composed of rigid elements: fuselage, wings, engine nacelles and rotors on which inertia, gravity and aerodynamics loads are calculated. In the paper the details of derivation of equation of motion and preliminary simulation results are presented.

6

Sterowanie wiropłatem typu tiltrotor

Miller M., Narkiewicz J.

Prace Instytutu Lotnictwa

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2002

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z. 1-2 (168-169)

59-64

PL

Tiltrotor to wiropłat z wirnikami przestawianymi względem kadłuba, co pozwala na uzyskanie prędkości przelotowej większej niż śmigłowiec, posiadający możliwość zawisu, pionowego startu i lądowania. W pracy przedstawiono: przegląd konstrukcji wiropłatów typu tiltrotor, w tym prototypów (załogowych i bezzałogowych) oraz zasady sterowania tego typu statkami powietrznymi. Jest to pierwszy etap prac prowadzących do budowy modelu matematycznego tiltrotora. Podano założenia przyjęte przy tworzeniu modelu matematycznego.

EN

A tiltrotor is an aircraft which can fly fast and efficiently in forward flight like a turboprop airplane and also takeoff, hover, and land vertically like a helicopter. Two rotors, engines and gearboxes are typically in wingtip nacelles which rotate from a horizontal position (airplane or cruise mode) to the vertical one (helicopter or hover mode) providing capability of vertical take off and landing and propulsive force in a cruise flight. In the paper the principles of tiltrotor control are reviewed, which is the first phase of building general simulation model.