Control strategy of boeing 737-800 under gust loads

Dissertant

Muhammad, Manar Nashwan

Thesis advisor

Abd al-Wahhab, Imad Natiq
Atiyyah, Qasim Abbas

University

University of Technology

Faculty

Department of Mechanics and Equipments Engineering

University Country

Iraq

Degree

Master

Degree Date

2013

English Abstract

Aircrafts encountering with turbulence represent a serious safety threat for airlines.

A side of the human suffering, every year injuries to passengers and flight crews cost in lost work time and medical expenses.

Often in aircraft model simulation development, the gust effects are neglected for various reasons and removed in the final form of the equations of motion.

Here, gust effects are the key excitation of interest.

In this work, a methodology to predict the aircraft normal load factor due to flight in a turbulent environment, and a state variables transient motion analysis is presented.

Based on airworthiness requirements of dynamic structure loadings, discrete one-minus-cosine and statistical power spectral continuous turbulence models are employed.

Gusts loads, whether due to discrete or continuous turbulence, are ordinarily considered to be the results of a change of angle of attack due to a component of gust velocity at right angles to the flight path.

To demonstrate the state variables behavior of the system during turbulent flight, modified longitudinal short-period/pure-plunge aircraft equations of motion are solved.

A numerical model for a large civil transport aircraft Boeing 737-800 with different flight conditions is constructed to illustrate the results.

Pure-plunge and short-period dynamic models of severe gust velocity of 15.8 – 18.6 m/s excitation input is numerically developed to describe the normal load factor throughout the aircraft due to vertical gust.

The results indicated a short-period model was more reliable rather than the pure-plunging model.

Based on the peak load-factor values, a comparison between discrete and continuous methods shows that the one-minus-cosine method becomes the critical one for aircraft due to the relation between gust length and gust velocity.

Load factor values estimated via these methods remained within Federal Aviation Requirements of structure loadings.

Higher gust loading severity, more than 1g, occurred at the lower altitudes due to high air density while upper altitude encountered milder gust loadings.

Effects of compressibility on aircraft state variable response is evident as much as the Mach no.

above 0.6.

A methodology for the existence of Limit Cycle Oscillation L.C.O and system stability indication according to Lyapunov exponent criterion is applied.

Gust alleviation is an important object from the point of view of structure, pilot fatigue, passengers comfort and handling qualities.

In current work, a robust control scheme for suppressing gust effects is presented.

Neural network control system with NARMA-L2 controller is employed so that the system would give no error in a desired time.

The numerical results show that the amplitude response of the state variables reach their steady state condition without any error in desired time.

Also, the load factor is highly reduced as a consequence of controlling these state variables.

These results exhibit good agreements with published work.

A new analysis is obtained by tracking the Lyapunov values during all period to verify the control of state variables.

It has been found that the present work can be considered as an efficient numerical tool used for many dynamic systems in case of using the related mathematical model of the problem under consideration, such as robotics, traking control ship, engine control system, etc.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

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Language

English

Data Type

Arab Theses

Record ID

BIM-420223