scholarly journals Designing a Control System for an Airplane Wing Flutter Employing Gas Actuators

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
A. R. Ansari ◽  
A. R. B. Novinzadeh
Keyword(s):  
Good Accuracy ◽  
Dynamic Instability ◽  
Pulse Frequency ◽  
Primary Control ◽  
Wing Flutter ◽  
Supersonic Regime ◽  
Process Output ◽  
Gas Consumption ◽  
Airplane Wing ◽  
Layer Flow

The wing flutter is a dynamic instability of a flight vehicle associated with the interaction of aerodynamic, elastic, and inertial forces (aeroelastics phenomena). In this study, just the primary control is investigated. Also, in order to control the two-dimensional wing flutter, the force jet and pulse width pulse frequency (PWPF) are suggested. The PWPF modulator has the advantage of almost linear operation, low jet gas consumption, flexibility in addressing various needs, and good accuracy in presence of oscillations. This scheme makes use of quasi-steady dynamic premises and incompressible flow, as well as the thin airfoil theory. It should be noted that, to justify the application of the aerodynamic theory, we have speculated that the thruster jet ejected through a nozzle with a diameter smaller than several millimeters has a supersonic regime (with Mach number of the order of M≈3.5). Consequently, the interference of the thruster jet in the boundary layer, flow, and circulation around the airfoil which are characterized by low speed would be negligible. The operation of the jet as a thruster is handled by the PWPF modulator, and the process output is fed back to the system via a PD controller. In order to control the wing flutter oscillation, the location of installing the actuator on the airfoil is investigated.

A Method for the Calculation of 3D Boundary Layers on Practical Wing Configurations

1981 ◽  
Vol 103 (1) ◽  
pp. 104-111 ◽  
Author(s):  
J. P. F. Lindhout ◽  
G. Moek ◽  
E. De Boer ◽  
B. Van Den Berg
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Boundary Layer Flow ◽  
Eddy Viscosity ◽  
Separated Flow ◽  
Laminar Boundary Layers ◽  
Eddy Viscosity Model ◽  
Airplane Wing ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow

This paper gives a description of a calculation method for 3D turbulent and laminar boundary layers on nondevelopable surfaces. A simple eddy viscosity model is incorporated in the method. Special attention is given to the organization of the computations to circumvent as much as possible stepsize limitations. The method is also able to proceed the computation around separated flow regions. The method has been applied to the laminar boundary layer flow over a flat plate with attached cylinder, and to a turbulent boundary layer flow over an airplane wing.

Self-Induced Vibrations

1933 ◽  
Vol 1 (1) ◽  
pp. 5-12
Author(s):  
J. G. Baker
Keyword(s):  
Transmission Lines ◽  
Forced Vibration ◽  
Electrical Engineering ◽  
Musical Instruments ◽  
Vacuum Tube ◽  
Wing Flutter ◽  
Airplane Wing

Abstract A “self-induced” vibration is defined as a phenomenon in which the alternating forces furnishing the energy to the vibration are controlled by the motion, in contradistinction to a “forced” vibration, where the force depends on time only. The following are examples of self-induced vibrations: (1) All bowed string or blown musical instruments, (2) the vacuum-tube oscillator, (3) fluttering of valves in air or water lines, (4) nosing of locomotives and street cars, (5) airplane-wing flutter, (6) certain cases of hunting of generators, and (7) certain cases of vibration of transmission lines due to wind. In physics and electrical engineering self-induced vibrations are common and often very useful, whereas most mechanical or machinery vibrations do not fall in this classification, since unbalance forces and other alternating forces unaffected by the motion are very common. Kimball and Newkirk were the first to call attention to and to explain self-induced vibration phenomena capable of causing serious mechanical difficulties. This paper discusses methods of studying self-induced vibrations and describes several representative cases that have been studied by the author and his colleagues in the last few years.

Wind Tunnel Testing of Composite Wing Flutter Speed due to Control Surface Excitation

2013 ◽  
Vol 315 ◽  
pp. 359-363 ◽  
Author(s):  
Mahzan Muhammad Iyas ◽  
Muhamad Sallehuddin ◽  
Mat Ali Mohamed Sukri ◽  
Mansor Mohd Shuhaimi
Keyword(s):  
Wind Tunnel ◽  
Dynamic Instability ◽  
Wind Tunnel Test ◽  
Control Surface ◽  
Wind Tunnel Testing ◽  
Structural Stiffness ◽  
Wing Flutter ◽  
Flutter Speed ◽  
Surface Excitation ◽  
Composite Wing

Flutter is a dynamic instability problem represents the interaction among aerodynamic forces and structural stiffness during flight. The study was conducted to investigate whether deflecting the control surface will affect the flutter speed and the flutter frequency. A wind tunnel test was performed using a flat plate wing made of composite material. It was found that by deflecting the control surface at 45°, the wing entered flutter state at wind speed of 28.1 m/s instead of 33.4 m/s. In addition, the flutter frequency also reduced from 224.52 Hz to 198.96 Hz. It was concluded that by deflecting the control surface, the wing experienced flutter at lower speed and frequency.

Composite Wing Flutter Speed and Frequency due to Variable Control Surface Deflection in Low Speed Wind Tunnel

2013 ◽  
Vol 390 ◽  
pp. 3-7
Author(s):  
Muhammad Iyas Mahzan ◽  
Sallehuddin Muhamad ◽  
Sa’ardin Abdul Aziz ◽  
Mohamed Sukri Mat Ali
Keyword(s):  
Wind Tunnel ◽  
Dynamic Instability ◽  
Wind Tunnel Test ◽  
Control Surface ◽  
Wing Flutter ◽  
Flutter Speed ◽  
Surface Deflection ◽  
Relationship Of ◽  
Low Speed Wind Tunnel ◽  
The Relationship

Flutter is a dynamic instability problem represents the interaction among structural, aerodynamic, elastic and inertial forces and occurred when the energy is continuously transformed by the surrounding fluids to a flying structure in the form of kinetic energy. The study was conducted to investigate the relationship of the control surface deflection angle to the flutter speed and the flutter frequency. A wind tunnel test was performed using a flat plate wing made of composite material. It was found that by deflecting the control surface up to 45°, the flutter speed reduced almost linearly from 35.6 m/s to 22.7 m/s. The flutter frequency greatly reduced from 48 Hz without the control surface deflected to 34 Hz with the control surface deflected at 15°. After 15° deflection up to 45°, the flutter frequency reduced almost linearly.

scholarly journals Modeling the Male Reproductive Endocrine Axis: Potential Role for a Delay Mechanism in the Inhibitory Action of Gonadal Steroids on GnRH Pulse Frequency

Endocrinology ◽  
2016 ◽  
Vol 157 (5) ◽  
pp. 2080-2092 ◽  
Author(s):  
Teuku R. Ferasyi ◽  
P. Hugh R. Barrett ◽  
Dominique Blache ◽  
Graeme B. Martin
Keyword(s):  
Negative Feedback ◽  
Time Delays ◽  
Model Development ◽  
Computer Software ◽  
Critical Factor ◽  
Pulse Frequency ◽  
Primary Control ◽  
Reproductive Endocrine ◽  
Endocrine Axis ◽  
Male Sheep

Abstract We developed a compartmental model so we could test mechanistic concepts in the control of the male reproductive endocrine axis. Using SAAM II computer software and a bank of experimental data from male sheep, we began by modeling GnRH-LH feed-forward and LH-T feedback. A key assumption was that the primary control signal comes from a hypothetical neural network (the PULSAR) that emits a digital (pulsatile) signal of variable frequency that drives GnRH secretion in square wave-like pulses. This model produced endocrine profiles that matched experimental observations for the testis-intact animal and for changes in GnRH pulse frequency after castration and T replacement. In the second stage of the model development, we introduced a delay in the negative feedback caused by the aromatization of T to estradiol at the brain level, a concept supported by empirical observations. The simulations showed how changes in the process of aromatization could affect the response of the pulsatile signal to inhibition by steroid feedback. The sensitivity of the PULSAR to estradiol was a critical factor, but the most striking observation was the effect of time delays. With longer delays, there was a reduction in the rate of aromatization and therefore a decrease in local estradiol concentrations, and the outcome was multiple-pulse events in the secretion of GnRH/LH, reflecting experimental observations. In conclusion, our model successfully emulates the GnRH-LH-T-GnRH loop, accommodates a pivotal role for central aromatization in negative feedback, and suggests that time delays in negative feedback are an important aspect of the control of GnRH pulse frequency.

scholarly journals Ballistic Range Testing Data Analysis of Tianwen-1 Mars Entry Capsule

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Haogong Wei ◽  
Xin Li ◽  
Jie Huang ◽  
Qi Li ◽  
Wei Rao
Keyword(s):  
Dynamic Instability ◽  
Linear Regression Method ◽  
Ballistic Range ◽  
Mass Properties ◽  
Testing Data ◽  
Supersonic Regime ◽  
Range Testing ◽  
Mach Numbers ◽  
Scaled Models ◽  
Range Test

A typical blunt body such as Tianwen-1 Mars entry capsule suffers dynamic instability in supersonic regime. To investigate the unstable Mach range of flight and to confirm the design of aerodynamic shape and mass properties, a ballistic range test was carried out aiming at capturing supersonic dynamic characteristics of Tianwen-1. Aerodynamic coefficients of free-flight scaled models were derived by modified linear regression method based on position and attitude data, while the dynamic coefficients were established under the assumption of small angle linearization. The static moment coefficients and dynamic derivatives were identified thereafter. Results show that models in untrimmed configuration are dynamically unstable at certain Mach numbers, whereas models in trimmed configuration are dynamically stable at other Mach numbers tested. Both trimmed and untrimmed configurations are statically stable in all testing cases.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 502-503
Author(s):  
Eva-Maria Mandelkow ◽  
Ron Milligan
Keyword(s):  
Electron Microscopy ◽  
Dynamic Instability ◽  
Entire Solution ◽  
Reaction Scheme ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
A Chain ◽  
Ray Scattering

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?

An Input–Process–Output Model of Pilot Core Competencies

2017 ◽  
Vol 7 (2) ◽  
pp. 78-85 ◽  
Author(s):  
Heikki Mansikka ◽  
Don Harris ◽  
Kai Virtanen
Keyword(s):  
Path Analysis ◽  
Team Performance ◽  
Core Competencies ◽  
Core Competency ◽  
Principal Component ◽  
Analysis Model ◽  
Input Process ◽  
The Core ◽  
Performance Framework ◽  
Process Output

Abstract. The aim of this study was to investigate the relationship between the flight-related core competencies for professional airline pilots and to structuralize them as components in a team performance framework. To achieve this, the core competency scores from a total of 2,560 OPC (Operator Proficiency Check) missions were analyzed. A principal component analysis (PCA) of pilots’ performance scores across the different competencies was conducted. Four principal components were extracted and a path analysis model was constructed on the basis of these factors. The path analysis utilizing the core competencies extracted adopted an input–process–output’ (IPO) model of team performance related directly to the activities on the flight deck. The results of the PCA and the path analysis strongly supported the proposed IPO model.

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