What is flutter in signals and system


flutter is the rapid variation of signal parameters, such as amplitude, phase, and frequency. Examples of electronic flutter are:

-Rapid variations in received signal levels, such as variations that may be caused by atmospheric disturbances, antenna movements in a high wind, or interaction with other signals.
-In radio propagation, a phenomenon in which nearly all radio signals that are usually reflected by ionospheric layers in or above the E-region experience partial or complete absorption.
-In radio transmission, rapidly changing signal levels, together with variable multipath time delays, caused by reflection and possible partial absorption of the signal by aircraft flying through the radio beam or common scatter volume.
-The variation in the transmission characteristics of a loaded telephone circuit caused by the action of telegraph direct currents on the loading coils.
-In recording and reproducing equipment, the deviation of frequency caused by irregular mechanical motion, e.g., that of capstan angular velocity in a tape transport mechanism, during operation.

Parameter estimation methods for flight flutter testing
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as the half-power 69] including both input (added to the input signals bandwidths overlapping Knauer K. Sensburg 0.,Ground and Flight Schoukens J.,Flight Flutter Data Analysis with Test K. Leuridan J., AGARD Conf 339 Ground/Flight Testing and Signal Processing and

Recursive output-only subspace identification for in-flight flutter monitoring
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L. Mevel, M. Basseville, A. Benveniste, Statistical Approach to flutter monitoring , in Proceedings of the 13th IFAC Symposium on System Identification, Sysid 03 Variable Subspace Tracking Using Projection Approximation , IEEE Transactions on Signal Processing, Vol

The blade flutter measurement based on the blade tip timing method
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If there was no blade flutter the time differences of the blades would have been constant one of the measurements) are depicted in the figure 4. As you can see the signals from different Obviously, the best signal can be seen on the very bottom record which was captured at the

Flutter simulation
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a one-channel system four major components were needed: (1) An angular displacement transducer, (2) a preamplifier to raise the signal level; (3) a power amplitier and (4) an electro-mechanical shaker. Various designs for these components were used in the flutter

Tools to improve detection of structural changes from in-flight flutter data
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Flutter tests consist of flying the aircraft at different airspeeds to provide evidence that This encompasses measurement noise, missing or noised excitation signals and low number of sensors System identification is a standard tool for the analysis of forcefully or ambient excited

Flutter suppression using active controls based on the concept of aerodynamic energy
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Flutter suppression implies, essentially, the control of structural modes only. Therefore, mode stabilization methods are of prime importance in flutter suppression An unstable control system can arise, for example, when a signal sensed from one struc tural mode gives rise to

A flight test to demonstrate flutter and evaluate the flutterometer
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the flutterometer implementation traces the data from aircraft telemetry to the gener- ation of a robust flutter margin Also, the cache contained all signals from the entire flight This trigger condition for the ATW testing was a signal that was nonzero only while the excitation system

Design for active and passive flutter suppression and gust alleviation
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Structural modifications are formulated in a way which enables the treatment of passive flutter suppression system with the same procedures by which active control systems are designed. Page 9 vehicle is involved. Loss of a flutter suppression control system

Flutter vulnerability assessment of flexible bridges
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oscillation amplitude for a circular cylinder . 21 2.6 Response of a circular model stack for different values of structural damping . . 22 2.7 Reduced critical flutter wind speed for a theoretical flat plate vs. frequency ratio 24 2.8 Reference system for oscillating flat plate theory

Wind tunnel flutter tests of a u-tail configuration Part 1: Model design and testing
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of the two modes involved into flutter increases suddenly, cancelling the flutter onset first device, an ONERA made analog/digital hardware, can only receive signals from two accelerometers with adjustable parameters (threshold and number of overpasses) and one TTL signal

Detection of reentry currents in atrial flutter by magnetocardiography
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Another advantage of such a plot is that the signal obtained at a given grid position is already propor- tional to the difference of the signals produced by the equivalent dipole at two different dipole V. CONCLUSION The magnetic signal produced by atrial flutter induced in

Embedded system for real time flight flutter detection
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and damping coefficients calculations are performed for each wavelet-filtered signal in the The flutter appearance can then be determined using the damping coefficients thresholds table performance of the flutterometer has been verified on acceleration signals recorded with a

Differentiation of atrial flutter and atrial fibrillation from surface electrocardiogram using nonlinear analysis
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microreentrant wavelets of various sizes wander through the atria [ 4]. Atrial flutter and atrial a challenge [5-7]. Recently, nonlinear analysis has been applied to cardiac signals and atrial These parameters have been used to explain ECG signal behavior in many studies [8-11]

The subcritical response and flutter of a swept-wing model
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of forcing as practicable with the equipment used, to achieve the greatest ratio of signal to noise time taken over these measurements lind the effect of limiting the number of transducer signals that could 3). At speeds close to the critical flutter speed, the low damping in two of the

Real-time assessment of flutter stability based on automated output-only modal analysis
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signals such that a proportional voltage can be passed to an electrodynamical exciter on each side. Small heave motions of the airfoil can then either be amplified or damped, by applying the inverted signal . Tests revealed that in the open-loop state this flutter control system is

Simple adaptive control for airfoil flutter suppression
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is a possibility of using them for stabilization problems, when the reference signal is zero of IRM adaptive controllers is used in the present paper for suppressing the airfoil flutter the presence of some nonlinearities in the control loop (for example, quantization of signals by level

Design and Tests of an Experimental Flutter Mount System
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Considering the expected values of the frequencies involved in flutter a range of frequencies below 25 hertz was investigated during the Modal Analysis A dual-channel BK Dynamic Signal Analyzer type 2032 was used to measure the signals . Page 5

SYSTEM IDENTIFICATION AND AIRCRAFT FLUTTER
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It was successfully used in the flutter model experiment of a wing with external bodies Both time domain methods could directly use measured samp- ling data to perform system identification without special signal analysis equipment

New concepts for flight flutter parameter estimation
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Spatial filtering consists of forming a weighted summation of response signals measured at different points The spatial weighting coeffkients are chosen such that a particular signal of interest is Variants of this technique have been proposed or used in flight flutter testing and

Adaptive flutter suppression, analysis and test
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flutter parameters which are then used to provide an appro- priate feedback signal for flutter Detection is defined as determining whether any flutter mode exists while discrimination decides which The first step requires the construction of signals that combine the outputs of the

Experimental and numerical investigation of nonlinear effects in transonic flutter
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2.7 shows only the three – signals one at a subcritical Mach number (a) and two at the exciter rod belonging to case (a). We see from the exciter-rod-force signal (b) that to positive feedback (+) within the labeled time span, thereby artificially exciting the flutter oscillations shown

Active control laws for flutter suppression
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their actuation system . A typical active control system for flutter suppression is designed to perform three functions: a) sensing the flutter mode, b) feeding back the signal and c) controlling the flutter mode. Various paradigms of

Flutter speed prediction based on frequency-domain identification of a time-varying system
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The errors-in-variables (EIV) framework was used, as both the input and output signal are disturbed with noise In the case of wind tunnel tests and in-flight flutter tests the time variation of the system is rather slow, as are the system dynamics

Active flutter control of a smart fin
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The developed controllers performed well around the flutter point and also stabilized the system over a wide flow speed range. Keywords: Active flutter control, piezoelectricity, smart structure, H∞ controller design 1. INTRODUCTION

Surface Wavefront Propagation Maps: Non-invasive characterization of atrial flutter circuit
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Atypical flutter was present in 3 patients with different AFL wave morphologies Signals were acquired at a sampling rate of 2048 Hz, with a resolution of 1 microvolt and a Before acquisition, signal quality of all leads was visually inspected and ECG recordings were stored for off

An overview of flutter prediction in tests based on stability criteria in discrete-time domain
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Flutter boundary prediction methods in which only measured wing response signals are analyzed can be 2007) showed that FMDS-N did not work well as a predictor of flutter onset for The AR-MA process for a sampled signal of random responses, Jurys stability criterion and

Flutter control using vibration test data: theory, rig design and preliminary results
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It will be demonstrated that any input and output signals be used in aeroelastic eigenvalue assignment, in BHK Lee, LY Jiang and YS Wong, Flutter of an Robust pole placement in structures by the method of receptances, Mechanical Systems and Signal Processing, 25

Real-time flutter detection from in-flight vibration data
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Thus processing 20 modes would take 12.5 ms, allowing for signals sampling with In the paper, problems arising during implementation of signal processing algorithms in FPGA Implementation of the flutter monitoring algorithm is proposed with Hardware-Software Co-design

Wind tunnel control software for identification of flutter derivatives on bridge sectional tests
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The calculated modal parameters permit to build the aeroelastic matrices and therefore the flutter derivatives which are saved in files Figure 2. Main Window. Figure 3. Aeroelastic Data. Figure 4. Measured Signal . Figure 5. Numerical approximations of signals

Leading Edge Flutter of Supercavitating Hydrofoils.
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defined in the usual way as Q =w N/AW . This procedure worked well except in the following circumstances. When used at or near flutter conditions in the water tunnel, a certain level required removing power from the system . Under these conditions the

Alternative numerical method for identification of flutter on free vibration
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Errors accumulate upon differentiation and all methods mentioned above need to deal with contaminated signals . Specifically, indirect flutter derivatives (𝐻2 ∗,𝐻3 ∗,𝐴1 ∗,𝐴4 ∗ ) are sensitive to the noise to signal ratio in two degrees of freedom (2DOF) (b) Second RF application, results in immediate decrease of the local signal amplitude and fast termination of the flutter (c) As Recently, an alternative approach was developed where large atrial signals were targeted as they represent bundles of conduc- tion through the

High accuracy numerical and signal processing approaches to extract flutter derivatives
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As the results, numerical and signal processing approaches must be considered to obtain solutions To obtain solutions in system identification, GLS (General least square) method is used to consider iteration Flutter is aeroelastic self-excited oscillation of a structural system

Operational Modal Analysis for in-line flutter assessment during wind tunnel testing
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These data allow verifying the possibility to use both quantities in a flutter detection scheme Figure 3 (Left) shows the power spectra of the acceleration and strain signals at a constant Based on the inspection of these power spectra, the 3rd acceleration signal (Blue) and the 4th

Flutter flight tests: A challenging benchmark for real-time methods
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a few years ago, the excitation device used at Airbus could only generate a single signal excitation device is available at Airbus which allows to supply concurrently several signals to several This system enables a great improvement of flutter testing since the various modes of

Structural nonlinearities simulation on the flutter electromechanical modeling test bench
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bit analog-to-digital converter (ADC), calculation of output signal and digital user interface which is used for monitoring, control and configuration of system STRUCTURAL NONLINEARITIES SIMULATION ON THE FLUTTER ELECTROMECHANICAL MODELING TEST BENCH

Noninvasive phase mapping of atrial flutter in humans comparison with invasive mapping
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Regular low-amplitude disturbances within the phase signals coincide with bipolar potentials recorded on the A: counterclockwise atrial flutter ; B: clockwise atrial flutter Crosses and dotted regression line represents correlation between earliest atrial bipolar signal on the HALO

Active control law design for flutter /LCO suppression based on reduced order model method
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For linear problems such as flutter or gust perturba- tion, the components of second kernel h2(n,n which includes the linearized nonlinear ef- fect[ 5-7]. Define the unit step input signal as 1 0 They are the appropriate constants selected according to the Volterra kernel signals

Flutter boundary prediction using experimental data
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flutter testing: First, the excitation to the system is important. The amplitude of the excitation signal should be high enough in order for the output signals to provide accurate information about the aircraft behavior. There are many excitation techniques used in flutter testing