Electromechanical Simulation of Helicopter Blade Responses to Random Excitation During Forward Flight

1974 ◽  
Vol 96 (2) ◽  
pp. 405-410
Author(s):  
D. D. Kana ◽  
Wen-Hwa Chu
Keyword(s):  
Transfer Functions ◽  
Function Analysis ◽  
Power Spectra ◽  
Random Excitation ◽  
Analog Computer ◽  
Excitation Power ◽  
Aerodynamic Load ◽  
Forward Flight ◽  
Transfer Function Analysis ◽  
Advance Ratio

The response of a model helicopter rotor blade to random excitation while in simulated forward flight is studied analytically and experimentally by means of an electromechanical apparatus. Generalized transfer functions are defined which relate steady-state responses in bending, flapping, and torsion modes to a sine input. Responses occur at the input and side-band frequencies. These transfer functions are then used along with excitation power spectra to predict the nonstationary time-averaged power spectrum of the response. Validity of the transfer function analysis is investigated by means of the electromechanical model which includes analog computer simulation of the interaction of blade deflections and aerodynamic load. Generalized transfer functions are measured for sinusoidal excitation. They are then used with measured excitation power spectra to predict the response, and the result is compared with measured response power spectra. Agreement is generally good for low advance ratio, but discrepancies diverge with increasing advance ratio.

A Transfer Function Analysis of a Geomagnetic Depth Sounding-Profile across Central British Columbia

1973 ◽  
Vol 10 (7) ◽  
pp. 1089-1098 ◽  
Author(s):  
H. Dragert
Keyword(s):  
British Columbia ◽  
Transfer Functions ◽  
Function Analysis ◽  
Three Dimensional ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Three Dimensional Model ◽  
Transfer Function Analysis ◽  
Single Station ◽  
Depth Sounding

Time variations of the geomagnetic field observed across British Columbia at a mean latitude of 54 °N are analyzed using 'single-station' and 'paired-station' optimum transfer functions. The frequency and spatial dependence of both coastal and inland geomagnetic anomalies are estimated with the following results. (1) The normal coast effect is strongly perturbed by lateral conductivity inhomogeneities both north and south of the profile. (2) A simple, single NW–SE striking conductivity contrast between the Cordillera and plains cannot account for the total geomagnetic anomaly in the area of the Rocky Mountain Trench; a three-dimensional model is required, incorporating (i) a lateral inhomogeneity striking east–west and located to the south of the profile, (ii) the effect of induction by the vertical component of source or secondary fields.

A Transfer-Function Formulation For Nonuniformly Distributed Parameter Systems

1994 ◽  
Vol 116 (4) ◽  
pp. 426-432 ◽  
Author(s):  
B. Yang ◽  
H. Fang
Keyword(s):  
Transfer Function ◽  
State Space ◽  
Fundamental Matrix ◽  
Transfer Functions ◽  
Function Analysis ◽  
System Response ◽  
Approximate Methods ◽  
Arbitrary Boundary ◽  
Transfer Function Analysis ◽  
Function Formulation

This paper studies a transfer-function formulation for general one-dimensional, nonuniformly distributed systems, subject to arbitrary boundary conditions and external disturbances. In the development, the governing equations of the nonuniform system are cast into a state-space form in the Laplace transform domain. The system response and distributed transfer functions are derived in term of the fundamental matrix of the state-space equation. Two approximate methods, the step-function approximation and truncated Taylor series, are proposed to evaluate the fundamental matrix. With the transfer-function formulation, various dynamics and control problems for the nonuniformly distributed system can be conveniently addressed. The transfer-function analysis also is applied to constrained/combined nonuniformly distibuted systems. The method developed is illustrated on two nonuniform beams.

Transfer function analysis of autonomic regulation. I. Canine atrial rate response

1989 ◽  
Vol 256 (1) ◽  
pp. H142-H152 ◽  
Author(s):  
R. D. Berger ◽  
J. P. Saul ◽  
R. J. Cohen
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Function Analysis ◽  
Cardiac Pacemaker ◽  
Corner Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Atrial Rate ◽  
Transfer Function Analysis ◽  
Functional Components

We present a useful technique for analyzing the various functional components that comprise the cardiovascular control network. Our approach entails the imposition of a signal with broad frequency content as an input excitation and the computation of a system transfer function using spectral estimation techniques. In this paper, we outline the analytical methods involved and demonstrate the utility of our approach in studying the dynamic behavior of the canine cardiac pacemaker. In particular, we applied frequency-modulated pulse trains to either the right vagus or the cardiac sympathetic nerve and computed transfer functions between nerve stimulation rate and the resulting atrial rate. We found that the sinoatrial node (and associated automatic tissue) responds as a low-pass filter to fluctuations in either sympathetic or parasympathetic tone. For sympathetic fluctuations, however, the filter has a much lower corner frequency than for vagal fluctuations and is coupled with a roughly 1.7-s pure delay. We further found that the filter characteristics, including the location of the corner frequency and rate of roll-off, depend significantly on the mean level of sympathetic or vagal tone imposed.

Transfer function analysis of the circulation: unique insights into cardiovascular regulation

1991 ◽  
Vol 261 (4) ◽  
pp. H1231-H1245 ◽  
Author(s):  
J. P. Saul ◽  
R. D. Berger ◽  
P. Albrecht ◽  
S. P. Stein ◽  
M. H. Chen ◽  
...  
Keyword(s):  
Transfer Function ◽  
Arterial Pressure ◽  
Transfer Functions ◽  
Function Analysis ◽  
Pressure Fluctuations ◽  
Rate Of Change ◽  
Phase Delay ◽  
Sinus Arrhythmia ◽  
Mechanical Effects ◽  
Transfer Function Analysis

We have demonstrated previously that transfer function analysis can be used to precisely characterize the respiratory sinus arrhythmia (RSA) in normal humans. To further investigate the role of the autonomic nervous system in RSA and to understand the complex links between respiratory activity and arterial pressure, we determined the transfer functions between respiration, heart rate (HR), and phasic, systolic, diastolic, and pulse arterial pressures in 14 healthy subjects during 6-min periods in which the respiratory rate was controlled in a predetermined but erratic fashion. Pharmacological autonomic blockade with atropine, propranolol, and both, in combination with changes in posture, was used to characterize the sympathetic and vagal contributions to these relationships, as well as to dissect the direct mechanical links between respiration and arterial pressure from the effects of the RSA on arterial pressure. We found that 1) the pure sympathetic (standing + atropine) HR response is characterized by markedly reduced magnitude at frequencies greater than 0.1 Hz and a phase delay, whereas pure vagal (supine + propranolol) modulation of HR is characterized by higher magnitude at all frequencies and no phase delay; 2) both the mechanical links between respiration and arterial pressure and the RSA contribute significantly to the effects of respiration on arterial pressure; 3) the RSA contribution to arterial pressure fluctuations is significant for vagal but not for sympathetic modulation of HR; 4) the mechanical effects of respiration on arterial pressure are related to the negative rate of change of instantaneous lung volume; 5) the mechanical effects have a higher magnitude during systole than during diastole; and 6) the mechanical effects are larger in teh standing than the supine position. Most of these findings can be explained by a simple model of circulatory control based on previously published experimental transfer functions from our laboratory.

scholarly journals Continuously measured renal blood flow does not increase in diabetes if nitric oxide synthesis is blocked

2008 ◽  
Vol 295 (5) ◽  
pp. F1449-F1456 ◽  
Author(s):  
Tracy D. Bell ◽  
Gerald F. DiBona ◽  
Rachel Biemiller ◽  
Michael W. Brands
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Renal Blood Flow ◽  
Function Analysis ◽  
Control Period ◽  
Power Spectra ◽  
Tubuloglomerular Feedback ◽  
Left Renal Artery ◽  
Renal Vasculature ◽  
Transfer Function Analysis

This study used 16 h/day measurement of renal blood flow (RBF) and arterial pressure (AP) to determine the role of nitric oxide (NO) in mediating the renal vasodilation caused by onset of type 1 diabetes. The AP and RBF power spectra were used to determine the autoregulatory efficiency of the renal vasculature. Rats were instrumented with artery and vein catheters and a Transonic flow probe on the left renal artery and were divided randomly into four groups: control (C), diabetes (D), control plus nitro-l-arginine methyl ester (l-NAME; CL), and diabetes plus l-NAME (DL). Mean AP averaged 90 ± 1 and 121 ± 1 mmHg in the D and DL groups, respectively, during the control period, and RBF averaged 5.9 ± 1.2 and 5.7 ± 0.7 ml/min, respectively. Respective C and CL groups were not different. Onset of diabetes (streptozotocin 40 mg/kg iv) in D rats increased RBF gradually, but it averaged 55% above control by day 14. In DL rats, on the other hand, RBF remained essentially constant, tracking with RBF in the nondiabetic C and CL groups for the 2-wk period. Diabetes did not change mean AP in any group. Transfer function analysis revealed impaired dynamic autoregulation of RBF overall, including the frequency range of tubuloglomerular feedback (TGF), and l-NAME completely prevented those changes as well. These data strongly support a role for NO in causing renal vasodilation in diabetes and suggest that an effect of NO to blunt RBF autoregulation may play an important role.

Frequency response characteristics of cerebral blood flow autoregulation in rats

2007 ◽  
Vol 292 (1) ◽  
pp. H432-H438 ◽  
Author(s):  
Brittany Kolb ◽  
Diane L. Rotella ◽  
Harald M. Stauss
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Carotid Artery ◽  
Cerebral Perfusion Pressure ◽  
Cerebral Perfusion ◽  
Perfusion Pressure ◽  
Transfer Functions ◽  
Function Analysis ◽  
Cerebrovascular Autoregulation ◽  
Transfer Function Analysis

Transfer function analysis of blood pressure and cerebral blood flow in humans demonstrated that cerebrovascular autoregulation operates most effectively for slow fluctuations in perfusion pressure, not exceeding a frequency of ∼0.15 Hz. No information on the dynamic properties of cerebrovascular autoregulation is available in rats. Therefore, we tested the hypothesis that cerebrovascular autoregulation in rats is also most effective for slow fluctuations in perfusion pressure below 0.15 Hz. Normotensive Wistar-Kyoto rats ( n = 10) were instrumented with catheters in the left common carotid artery and jugular vein and flow probes around the right internal carotid artery. During isoflurane anesthesia, fluctuations in cerebral perfusion pressure were elicited by periodically occluding the abdominal aorta at eight frequencies ranging from 0.008 Hz to 0.5 Hz. The protocol was repeated during inhibition of myogenic vascular function (nifedipine, 0.25 mg/kg body wt iv). Increases in cerebral perfusion pressure elicited initial increases in cerebrovascular conductance and decreases in resistance. At low occlusion frequencies (<0.1 Hz), these initial responses were followed by decreases in conductance and increases in resistance that were abolished by nifedipine. At occlusion frequencies of 0.1 Hz and above, the gains of the transfer functions between pressure and blood flow and between pressure and resistance were equally high in the control and nifedipine trial. At occlusion frequencies below 0.1 Hz, the gains of the transfer functions decreased twice as much under control conditions than during nifedipine application. We conclude that dynamic autoregulation of cerebral blood flow is restricted to very low frequencies (<0.1 Hz) in rats.

A new method for evaluation of transformer drying process using transfer function analysis and artificial neural network

2013 ◽  
Vol 62 (1) ◽  
pp. 153-162
Author(s):  
Hormatollah Firoozi ◽  
Mehdi Bigdeli
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Transfer Functions ◽  
Power Transformer ◽  
Function Analysis ◽  
Active Part ◽  
Drying Process ◽  
Transfer Function Analysis ◽  
Artificial Neural ◽  
Artificial Neural Network Ann

Abstract Since a few years ago, there is an increasing interest for utilization of transfer functions (TF) as a reliable method for diagnosing of mechanical faults in transformer structure. However, this paper aims to develop the application of TF method in order to evaluate the drying quality of active part during the manufacturing process of transformer. To reach this goal, the required measurements are carried out on 50 MVA 132 KV/33 KV power transformer when active part is placed in the drying chamber. Two different features extracted from the measured TFs are then used as the inputs to artificial neural network (ANN) to give an estimate for required time in drying process. Results show that this new represented method could well forecast the required time. The results obtained from this method are valid for all the transformers which have the same design.

Seismoelectric wave conversions in porous media: Field measurements and transfer function analysis

Geophysics ◽  
2001 ◽  
Vol 66 (5) ◽  
pp. 1417-1430 ◽  
Author(s):  
Stéphane Garambois ◽  
Michel Dietrich
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Electric Field ◽  
Electric Fields ◽  
Field Experiments ◽  
Transfer Functions ◽  
Function Analysis ◽  
Transfer Function Analysis ◽  
Electromagnetic Disturbances ◽  
The Magnetic Field

We present a series of field experiments showing the transient electric fields generated by a seismic excitation of the subsurface. After removing the powerline noise by adaptive filtering, the most prominent feature of the seismoelectric recordings is the presence of electric signals very similar to conventional seismic recordings. In one instance, we identified small‐amplitude precursory electromagnetic disturbances showing a polarity reversal on either side of the shotpoint. Concentrating on the dominant seismoelectric effect, we theoretically show that the electric field accompanying the compressional waves is approximately proportional to the grain acceleration. We also demonstrate that the magnetic field moving along with shear waves is roughly proportional to the grain velocity. These relationships hold true as long as the displacement currents are much smaller than the conduction currents (diffusive regime), which is normally the case in the low‐frequency range used in seismic prospecting. Furthermore, the analytical transfer functions thus obtained indicate that the electric field is mainly sensitive to the salt concentration and dielectric constant of the fluid, whereas the magnetic field principally depends on the shear modulus of the framework of grains and on the fluid’s viscosity and dielectric constant. Both transfer functions are essentially independent of the permeability. Our results suggest that the simultaneous recording of seismic, electric, and magnetic wavefields can be useful for characterizing porous layers at two different levels of investigation: near the receivers and at greater depth.

An improved statistical methodology to estimate and analyze impedances and transfer functions

1997 ◽  
Vol 83 (6) ◽  
pp. 2146-2157 ◽  
Author(s):  
Douglas Curran-Everett ◽  
Yiming Zhang ◽  
M. Douglas Jones ◽  
Richard H. Jones
Keyword(s):  
Time Series ◽  
Transfer Function ◽  
Fourier Transforms ◽  
Transfer Functions ◽  
Function Analysis ◽  
Statistical Methodology ◽  
Test Statistic ◽  
Discrete Fourier Transforms ◽  
Repeated Observations ◽  
Transfer Function Analysis

Curran-Everett, Douglas, Yiming Zhang, M. Douglas Jones, Jr., and Richard H. Jones. An improved statistical methodology to estimate and analyze impedances and transfer functions. J. Appl. Physiol. 83: 2146–2157, 1997.—Estimating the mathematical relationship between pulsatile time series (e.g., pressure and flow) is an effective technique for studying dynamic systems. The frequency-domain relationship between time series, often calculated as an impedance (pressure/flow), is known more generally as a frequency-response or transfer function (output/input). Current statistical methods for transfer function analysis 1) assume erroneously that repeated observations on a subject are independent, 2) have limited statistical value and power, or 3) are restricted to use in single subjects rather than in an entire sample. This paper develops a regression model for transfer function analysis that corrects each of these deficiencies. Spectral densities of the input and output time series and the cross-spectral density between them are first estimated from discrete Fourier transforms and then used to obtain regression estimates of the transfer function. Statistical comparisons of the transfer function estimates use a test statistic that is distributed as χ2. Confidence intervals for amplitude and phase can also be calculated. By correctly modeling repeated observations on each subject, this improved statistical approach to transfer function estimation and analysis permits the simultaneous analysis of data from all subjects in a sample, improves the power of the transfer function model, and has broad relevance to the study of dynamic physiological systems.

scholarly journals A general transfer function representation for a class of hyperbolic distributed parameter systems

2013 ◽  
Vol 23 (2) ◽  
pp. 291-307 ◽  
Author(s):  
Krzysztof Bartecki
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Function Analysis ◽  
Semigroup Theory ◽  
Distributed Parameter Systems ◽  
Hyperbolic Partial Differential Equations ◽  
Distributed Parameter ◽  
Function Representation ◽  
Tube Heat Exchanger ◽  
Transfer Function Analysis

Results of transfer function analysis for a class of distributed parameter systems described by dissipative hyperbolic partial differential equations defined on a one-dimensional spatial domain are presented. For the case of two boundary inputs, the closed-form expressions for the individual elements of the 2×2 transfer function matrix are derived both in the exponential and in the hyperbolic form, based on the decoupled canonical representation of the system. Some important properties of the transfer functions considered are pointed out based on the existing results of semigroup theory. The influence of the location of the boundary inputs on the transfer function representation is demonstrated. The pole-zero as well as frequency response analyses are also performed. The discussion is illustrated with a practical example of a shell and tube heat exchanger operating in parallel- and countercurrent-flow modes.

Sign in / Sign up

Export Citation Format

Share Document