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Output Error Method for Tiltrotor Unstable in Hover

Lichota P., Szulczyk J.

Archive of Mechanical Engineering

2017

Vol. LXIV, nr 1

23--36

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.

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

Sukhanovskii A., Evgrafova A., Popova E.

Archive of Mechanical Engineering

2017

Vol. LXIV, nr 2

177--188

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.

Maximum likelihood estimation for identification of aircraft aerodynamic derivatives

Lichota P., Lasek M.

Archive of Mechanical Engineering

2013

Vol. LX, nr 2

219--230

This article investigates identification of aircraft aerodynamic derivatives. The identification is performed on the basis of the parameters stored by Flight Data Recorder. The problem is solved in time domain by Quad-M Method. Aircraft dynamics is described by a parametric model that is defined in Body-Fixed-Coordinate System. Identification of the aerodynamic derivatives is obtained by Maximum Likelihood Estimation. For finding cost function minimum, Lavenberg-Marquardt Algorithm is used. Additional effects due to process noise are included in the state-space representation. The impact of initial values on the solution is discussed. The presented method was implemented in Matlab R2009b environment.

Artykuł zawiera informacje na temat identyfikacji pochodnych aerodynamicznych. Estymacja opiera się o parametry zapisywane przez Pokładowy Rejestrator Lotu. Zagadnienie jest rozważane w dziedzinie czasu przy użyciu podejścia Quad-M. Do opisu dynamiki samolotu wykorzystano model parametryczny zdefiniowany w układzie sztywno związanym z samolotem. Do identyfikacji wykorzystano Metodę Największej Wiarygodności. Do znalezienia minimum funkcji celu użyto algorytm Levenberga-Marquardta. W modelu uwzględniono wpływ dodatkowych czynników reprezentowany przez szum przetwarzania. Omówiono wpływ wartości początkowych na rozwiązanie. Prezentowane wyniki uzyskano w środowisku Matlab R2009b.