A Transfer Function Synthesis for Model Approximation with Resonance Peak Value

2008 ◽  
Vol 22 (1) ◽  
pp. 118-123
Keyword(s):  
Transfer Function ◽  
Resonance Peak ◽  
Model Approximation ◽  
Peak Value

scholarly journals Design of Low-Ripple and Fast-Response DC Filters in DC Distribution Networks

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3128 ◽  
Author(s):  
Jianquan Liao ◽  
Niancheng Zhou ◽  
Qianggang Wang
Keyword(s):  
Transfer Function ◽  
Distribution Network ◽  
Low Frequency ◽  
Distribution Networks ◽  
Optimization Method ◽  
Fast Response ◽  
Resonance Peak ◽  
Dc Distribution ◽  
Filtering Effect ◽  
Peak Value

The design and parameter selection of low-ripple and fast-response direct current (DC) filters are discussed in this study with the aim of alleviating the influence of a DC-side low-frequency voltage pulsation on a sensitive load in a DC distribution network. A method for determining the DC filter parameters by using a mofatching most flat response algorithm is presented. The voltage transfer function of the DC-side filter in the DC distribution network is deduced to analyze its voltage transfer characteristics. The resonance peak value of the filter network is an important factor affecting the transfer speed of a filter. A pole-circle-based parameter optimization method is proposed to move the poles of the filter transfer function down and to the left of pole plane for finding the appropriate capacitance, inductance, and damping parameters. This approach effectively restricts the resonance peak value, accelerates the transfer speed, and maintains steady filtering results. Simulation and test results verify that the filter has low resonance value, rapid convergence ability, and an excellent filtering effect.

Optimal design of inerter-based isolators minimizing the compliance and mobility transfer function versus harmonic and random ground acceleration excitation

2020 ◽  
pp. 107754632094017
Author(s):  
Marcial Baduidana ◽  
Aurelien Kenfack-Jiotsa
Keyword(s):  
Transfer Function ◽  
Vibration Absorber ◽  
Engineering Practice ◽  
Primary System ◽  
Optimal Parameters ◽  
Dynamic Vibration Absorber ◽  
Ground Acceleration ◽  
Dynamic Vibration ◽  
Optimum Parameters ◽  
Peak Value

This study is concerned with the problem of analysis and optimization of inerter-based systems. A main inerter system is generally composed of an inerter, a spring, and viscous damper. Series – parallel inerter system s and series inerter system s are two commonly used configurations of inerter-based system s . First , in this study , the H∞ optimum parameters of inerter-based isolators are derived to minimize the compliance and mobility transfer function of a single-degree -of-freedom system under a harmonic ground acceleration excitation. Under the optimum tuning condition, it is shown that the proposed inerter-based isolators when compared with the traditional dynamic vibration absorber provide larger suppression of the peak value of the magnitude of compliance and mobility transfer function s of the primary system. For the studied cases, more than 40% and 45% improvement can be attained in terms of minimizing the compliance and mobility transfer function s , respectively, as compared with the traditional dynamic vibration absorber for the series – parallel inerter system and 15% and 11% improvement can be attained respectively , for the series inerter system . Finally, further comparison between the inerter-based isolators and traditional dynamic vibration absorber under white noise excitation also shows that the series – parallel inerter system and series inerter system s are superior to the traditional dynamic vibration absorber . The results of the studied systems show that m ore than 23% and 16% improvement are attained in terms of minimizing the compliance and mobility transfer function s respectively , as compared with the traditional dynamic vibration absorber for the series – parallel inerter system and 26% and 13% improvement can be attained respectively , for the series inerter system . The optimal parameters for different cases are obtained. It is shown that the optimal parameters obtained using the minimized mobility transfer function are smaller than those using the compliance transfer function at all mass ratios or inertance-to-mass ratio. The results of this study can provide theoretical basis for design of the optimal inerter-based isolators in engineering practice.

The Research of Vehicle Seat Dynamic Comfort Characteristic

2013 ◽  
Vol 310 ◽  
pp. 244-248
Author(s):  
Rui Li ◽  
Li Xin Guo
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Peak Frequency ◽  
Resonance Peak ◽  
Order Resonance ◽  
First Order ◽  
Seat Comfort ◽  
Result Show ◽  
Vehicle Seat ◽  
Peak Value

Increasing consumption of the automobile make vehicle seat comfort characteristic paid more attention to. Damping performance as the third important factors is not allowed to ignore. A three freedom "human - seat" system model has been created for simulation. The result show that as the natural frequency f0 improved, the two resonance peak frequency of the system also improved, the growth of the first order resonance frequency is quite obvious, the second is less growth. And the higher the f0 the less change is. With the improvement of f0, the first order resonance peak to peak value obviously reduced, and the second order resonance peak to peak value increased. So, it is said that the higher the f0 the poor damping effect in high frequency area. The influence of ξ for the damping ratio of work frequency is not big, but the influence for the amplitude value is significant. Increase the natural frequency can make phase angle decreased when resonance, but the change of damping ratio, do not have obviously changes.

A Study on the Influence of Ship Roll Characteristics on the Risk of Cargo Shifting

2004 ◽  
Vol 41 (02) ◽  
pp. 51-59
Author(s):  
Anna Ryrfeldt
Keyword(s):  
Sensitivity Analysis ◽  
Transfer Function ◽  
Computational Efficiency ◽  
Transfer Functions ◽  
Resonance Peak ◽  
Roll Motion ◽  
Ship Motions ◽  
Load Case ◽  
Contributing Factors ◽  
Ship Roll

In a previous work a methodology for assessing the risk of cargo shifting has been developed and used to study the influence of different parameters on the risk of cargo shifting. It has been found that ship rolling is one of the major contributing factors of cargo shifting. Linear theory of ship motions is presently used in the methodology because of computational efficiency and simplicity. Because the roll motion is complex and difficult to predict because of nonlinearities, the present study has been performed in order to study the influence of the roll motion on the risk of cargo shifting. This study may be seen as a sensitivity analysis of roll motion with respect to cargo shifting. The risk has been studied by the number of potentially dangerous conditions and how they depend on such parameters as wave height and period, and ship heading toward waves. The influence of roll amplitude and phase, as well as the influence of roll stabilizing devices, on the number of dangerous conditions is studied for two vessels and two load cases each. Roll amplitude influence is analyzed by changing the amplitude of the transfer function, and the results show that the influence of roll amplitude is very large. This influence is especially marked when the roll amplitude is large and the vertical and horizontal accelerations are small to moderate. The influence of roll stabilizing devices is studied by cutting of the resonance peak in the transfer functions. The results show that roll stabilizing is often efficient but that it can be more important to choose load case in order to attain good seakeeping characteristics, especially with respect to roll motion.

scholarly journals Low-Cost Experimental Methodology for the Dynamic Model Approximation of Multirotor Actuators

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Walter A. Mayorga-Macías ◽  
Luis E. González-Jiménez ◽  
Marco A. Meza-Aguilar ◽  
Luis F. Luque-Vega
Keyword(s):  
Transfer Function ◽  
Embedded System ◽  
Duty Cycle ◽  
Transfer Functions ◽  
Electronic Control Unit ◽  
Low Cost ◽  
Design Procedure ◽  
Open Loop ◽  
Experimental Methodology ◽  
Model Approximation

A methodology for the experimental modelling of the electric actuators of a multirotor is presented in this work. These actuators are usually brushless DC motors which are driven by electronic speed controllers in an open loop. The duty cycle of a PWM signal, generated by the electronic control unit, is the input of the electronic controller. However, during the control design procedure for the multirotor, it is important to account with a model of the actuators as its dynamical features define the closed-loop performance of the overall aircraft. Hence, a procedure, based on low-cost electronic components, to obtain approximated transfer functions of the actuators of a multirotor is presented. Moreover, as the proposed signal processing algorithms are simple, the computational capabilities of the required embedded system are also low. Given that different control schemes require different information from the actuator, two models were obtained: a duty cycle vs. angular velocity transfer function and a duty cycle vs. consumed current transfer function. The effectivity of the proposal is validated with experimental results on common electric actuators of a multirotor.

Statistical Determination of Bit-Rock Interaction and Drill String Mechanics for Automatic Drilling Optimization

2020 ◽  
Author(s):  
Adrian Ambrus ◽  
Benoît Daireaux ◽  
Liv A. Carlsen ◽  
Rodica G. Mihai ◽  
Mohsen Karimi Balov ◽  
...  
Keyword(s):  
Transfer Function ◽  
Dynamic Models ◽  
Drill String ◽  
Model Parameters ◽  
Drilling Process ◽  
Transfer Function Model ◽  
Transient Effects ◽  
Model Approximation ◽  
Function Model ◽  
Rock Interaction

Abstract The ability to predict the response of a drill bit to the topside axial and rotational velocities of the drill-string is a prerequisite for any system aimed at automatically controlling the drilling parameters to optimize the rate of penetration and the overall quality of the well construction process. When drilling with a Polycrystalline Diamond Compact (PDC) bit, even the steady-state response can exhibit complex behavior, characterized by the presence of (at least) three different regimes whose range and parameters depend upon the bit characteristics and the mechanical properties of the formations being drilled. Transient effects significantly complicate the situation, especially when vibrations (axial, rotational or lateral) disturb the drilling process. Often, the root cause of these vibrations lies in the bit-rock interaction itself, while the drill string, through its elasticity and interaction with the borehole wall, may amplify or attenuate these vibrations. Therefore, continuous calibration of the drill string and bit-rock parameters from available surface and downhole measurements is critical for any automated control system relying on dynamic models of the drilling process. We present a calibration procedure whose goal is two-fold: first, to identify the time-varying parameters involved in the bit-rock interaction, and second, to provide a low-order, transfer function model approximation of the drill string axial and rotational dynamics. Our approach is based on particle filter techniques and a refined instrumental variable method for transfer function model estimation, and allows for real-time estimation of the various model parameters. We illustrate its behavior against recorded drilling data, where the proposed methods are shown to capture the different dynamics in place. We explain, in addition, how the calibrated drill string and bit-rock interaction models can be integrated in a framework to identify drilling parameter regions prone to axial or rotational vibrations.

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

Possible applications of fraunhofer holography in high resolution electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 222-223 ◽  
Author(s):  
N. Bonnet ◽  
M. Troyon ◽  
P. Gallion
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Far Field ◽  
Field Region ◽  
Crystalline Materials ◽  
Resolution Electron ◽  
The Ideal

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.

Ultimate resolution and information in electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 496-497
Author(s):  
D. Van Dyck
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Transfer Function ◽  
Information Transfer ◽  
Communication Channel ◽  
Structural Information ◽  
Information Rate ◽  
Noise Power ◽  
Signal Power ◽  
Imaging Device

An (electron) microscope can be considered as a communication channel that transfers structural information between an object and an observer. In electron microscopy this information is carried by electrons. According to the theory of Shannon the maximal information rate (or capacity) of a communication channel is given by C = B log2 (1 + S/N) bits/sec., where B is the band width, and S and N the average signal power, respectively noise power at the output. We will now apply to study the information transfer in an electron microscope. For simplicity we will assume the object and the image to be onedimensional (the results can straightforwardly be generalized). An imaging device can be characterized by its transfer function, which describes the magnitude with which a spatial frequency g is transferred through the device, n is the noise. Usually, the resolution of the instrument ᑭ is defined from the cut-off 1/ᑭ beyond which no spadal information is transferred.

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