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1

Measurements of flutter derivatives of a bridge deck sectional model

Gunawan L., Hafizh H., Muhammad H.

Journal of KONES

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2013

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Vol. 20, No. 4

107--116

EN

Aeroelastic phenomena should be considered during the design phase of long span bridges. One of the aeroelastic problems is flutter, the dynamic instability that may cause structural failure at a wind speed called the flutter speed. The prediction of flutter speed of a bridge needs a thorough modelling of bridge stiffness, inertias, and especially its unsteady aerodynamic forces. The potential flow theory is not applicable to calculate unsteady aerodynamics of oscillating bridges due to their non-streamlined complex geometry, and the non-avoidable flow separation. For these reasons, a semi empirical model proposed by Scanlan is used to describe unsteady aerodynamic forces on an oscillating bridge deck. In this model, relation between unsteady aerodynamic forces and motion of the bridge is modelled using parameters known as flutter derivatives. The values of flutter derivatives can be identified from the free vibration responses of an elastic bridge at several wind-speeds. This paper presents wind tunnel tests and flutter derivatives identification of a sectional aeroelastic bridge model. Modified Ibrahim Time Domain method was applied to identify the eigenvalues and eigenvectors of the model at each wind speed, from which the flutter derivatives can be calculated. The results show that the measurement procedure is able produce flutter derivatives, which are in good agreement with those obtained by other researchers.

2

Aerodynamic model identification of turboprop aircraft based on flight test data

Muhammad H., Hariowibowo H.

Journal of KONES

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2013

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Vol. 20, No. 3

275---282

EN

The aerodynamic model of an aircraft can be considered as a mathematical representation of the forces and moments acting on the aircraft. These forces and moments are usually approximated by polynomials as function of aircraft’s state variables. The coefficients in the polynomials are known as the aerodynamic parameters. These aerodynamic parameters are of importance in the evaluation of aircraft performance and stability-control characteristics of an aircraft. These parameters also can be used in the design of, for example, automatic flight control systems and mathematical model of flight simulator. This paper will discuss the principles of the aerodynamic model identification of the aircraft based on flight test data using parameter identification techniques. The paper starts with discussion of a mathematical model of an aircraft. Next, parameter identification techniques will be described. Two techniques often used for estimation of the aerodynamic parameters will be discussed. Results of the modelling and estimation of the aerodynamic parameters, state trajectory of the aircraft, bias errors in the instrumentation system, and calibration factors of the vane-angle of attack from flight test data of the N-250 turboprop aircraft will be presented in this paper. Original achievement of that paper is the mathematical model of a turboprop aircraft.

3

Mathematical modeling, simulation and identification of micro coaxial helicopter

Muhammad H., Thien H. P., Mulyanto T.

Journal of KONES

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2012

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Vol. 19, No. 2

353-364

EN

Micro Coaxial Helicopter with compact size and vertical takeoff ability offers a good Micro Aerial Vehicle (MAV) configuration to handle indoor mission such as search, rescue and surveillance. An autonomous MAV helicopter equipped with micro vision devices could provide more information of the scene, in which the human present is risky. Toward an autonomous flight, mathematical model of the helicopter should be obtained before controller design takes place. This paper will discuss the mathematical modelling, simulation and identification of a micro coaxial helicopter. The mathematical model of the micro coaxial helicopter will be presented, in which total forces and moment are expressed as a Taylor series expansion as function of the state and control variables. The mathematical model will be used to simulate the helicopter responses due to control input. The simulation was used to obtain better understanding of the characteristics of the helicopter before flight test program are performed. Flight test program dedicated to identify the parameter of the micro coaxial helicopter have been carried out. The micro coaxial helicopter was instrumented with sensory system to measure some input and output variables. The use of Kalman filter to estimate the state and total least squares to estimate the aerodynamic parameter of micro coaxial helicopter based on the flight test data will be presented. Some identification results and model validation will be given in this paper.