Properties of non-parametric time-domain methods for estimating transfer functions

1983 ◽  
Author(s):  
Lennart Ljung ◽  
Zhen-dong Yuan
Keyword(s):  
Time Domain ◽  
Transfer Functions ◽  
Non Parametric

scholarly journals STEADY-STATE ANALYSIS OF NONLINEARLY COUPLED CHUA'S CIRCUITS WITH PERIODIC INPUT

2003 ◽  
Vol 13 (11) ◽  
pp. 3395-3407 ◽  
Author(s):  
F. A. SAVACI ◽  
M. E. YALÇIN ◽  
C. GÜZELIŞ
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Transfer Functions ◽  
Piecewise Linear ◽  
Time Domain Analysis ◽  
Steady State Analysis ◽  
Linear Dynamic Systems ◽  
Periodic Input ◽  
The Time Domain ◽  
State Analysis

In this paper, nonlinearly coupled identical Chua's circuits, when driven by sinusoidal signal have been analyzed in the time-domain by using the steady-state analysis techniques of piecewise-linear dynamic systems. With such techniques, it has become possible to obtain analytical expressions for the transfer functions in terms of the circuit parameters. The proposed system under consideration has also been studied by analog simulations of the overall system on a hardware realization using off-the-shelf components as well as by a time-domain analysis of the synchronization error.

PROCESSING AND INTERPRETATION OF MAGNETOTELLURIC SOUNDINGS

Geophysics ◽  
1972 ◽  
Vol 37 (6) ◽  
pp. 1005-1021 ◽  
Author(s):  
G. Kunetz
Keyword(s):  
Transfer Function ◽  
Time Domain ◽  
Transfer Functions ◽  
Seismic Analysis ◽  
Magnetotelluric Soundings ◽  
Automatic Interpretation ◽  
Uniqueness Of The Solution ◽  
Experimental Values ◽  
The Time Domain ◽  
Analytical Expressions

A few methods in the processing and interpretation of magnetotelluric soundings over a stratified earth are investigated, with emphasis on the less commonly used time‐domain procedures. Analytical expressions of the theoretical transfer function between the magnetic‐ and electric‐field variations, both in frequency and time domain, are derived. Their properties are studied, and recursive algorithms are given for their numerical computation. On the other hand, a procedure is outlined which leads directly in the time domain to the experimental values of this transfer function. It is similar to the methods used in seismic analysis for signal determination and makes use of the auto‐ and crosscorrelation functions of the measured field variations. Finally, methods of interpretation, based either on a visual or on an automatic comparison of these theoretical and experimental transfer functions, are proposed. For the case of automatic interpretation, complementary geologic data should be used where possible to take care of the lack of uniqueness of the solution.

Dynamic Force Identification in Peripheral Milling Based on CGLS Using Filtered Acceleration Signals and Averaged Transfer Functions

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Chenxi Wang ◽  
Xingwu Zhang ◽  
Baijie Qiao ◽  
Hongrui Cao ◽  
Xuefeng Chen
Keyword(s):  
Time Domain ◽  
Transfer Functions ◽  
Milling Process ◽  
Dynamic Force ◽  
Band Pass Filter ◽  
Peripheral Milling ◽  
Milling Force ◽  
Force Identification ◽  
Milling Forces ◽  
Acceleration Signals

Dynamic milling forces have been widely used to monitor the condition of the milling process. However, it is very difficult to measure milling forces directly in operation, particularly in the industrial scene. In this paper, a dynamic force identification method in time domain, conjugate gradient least square (CGLS), is employed for reconstructing the time history of milling forces using acceleration signals in the peripheral milling process. CGLS is adopted for force identification because of its high accuracy and efficiency, which handles the ill-conditioned matrix well. In the milling process, the tool with high-speed rotation has different transfer functions between tool nose and accelerometers at different angular positions. Based on this fact, the averaged transfer functions are employed to reduce the error amplification of regularization processing for milling force identification. Moreover, in order to eliminate the effect of idling and high-frequency components on identification accuracy, the Butterworth band-pass filter is adopted for acceleration signals preprocessing. Finally, the proposed method is validated by milling tests under different cutting parameters. Experimental results demonstrate that the identified and measured milling forces are in good agreement on the whole time domain, which verifies the effectiveness and generalization of the indirect method for milling force measuring. In addition, the Tikhonov regularization method is also implemented for comparison, which shows that CGLS has higher accuracy and efficiency.

scholarly journals Introduction to the method of estimating time-domain response based on amplitude-frequency characteristics

2021 ◽  
Vol 2087 (1) ◽  
pp. 012061
Author(s):  
Mingrui Wang ◽  
Mei Xu ◽  
Jiangfeng Wang ◽  
Yingying Guo
Keyword(s):  
Research And Development ◽  
Time Domain ◽  
Electromagnetic Pulse ◽  
Parametric Modeling ◽  
Frequency Characteristics ◽  
Practical Applications ◽  
Time Domain Response ◽  
The Time Domain ◽  
Non Parametric

Abstract How to use the amplitude-frequency characteristics to reconstruct the signal to obtain the time-domain response has always been a concern in the field of nuclear electromagnetic protection. So far, in practical applications, parametric modeling and non-parametric modeling have been used to solve related problems. This article summarizes the research and development of using amplitude-frequency characteristics to recover time-domain signals in the field of nuclear electromagnetic pulse protection, and briefly introduces the shortcomings of the two methods in combination with specific experiments.

Optimization of Frequency Domain Fatigue Analysis for Unbonded Flexible Risers

2021 ◽  
Author(s):  
Jiabei Yuan ◽  
Yucheng Hou ◽  
Zhimin Tan
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Transfer Functions ◽  
Hybrid Approach ◽  
Fatigue Analysis ◽  
System Response ◽  
Similar Response ◽  
Potential Cost ◽  
Spectrum Prediction ◽  
Flexible Risers

Abstract Fatigue analysis of flexible risers is a demanding task in terms of time and computational resources. The traditional time domain approach may take weeks of time in global simulation, local modelling and post-processing of riser responses to get fatigue results. Baker Hughes developed a fast hybrid approach, which is based on a frequency domain technique. The new approach was first implemented at the end fitting region and then to all other regions of the riser. Studies showed that the hybrid approach achieved convenient and conservative results in a significant shorter period of time. To improve the accuracy and reduce conservatism of the method, Baker Hughes has further optimized the analysis procedure to seek better results approaching true solutions. Several methods were proposed and studied. The duration of representative cases and noncritical cases have been extended. The steps to predict stress spectrum based on transfer functions have also been updated. From previous studies, only one transfer function was built for fatigue load cases with similar response spectra. This assumption linearizes the system response and produces certain level of discrepancy against true time domain solution. In this study, multiple ways of spectrum prediction are evaluated and compared. The paper summarizes several techniques to further optimize the hybrid frequency domain approach. The updated fatigue results are found to be more accurate. The optimized approach therefore gives more flexibility to engineers to approach the true solutions, which were originally acquired from full 3-hr time domain simulations. The approach requires less analysis time and reduces iterations in pipe structure and riser configuration design, which leads to faster project execution and potential cost reduction.

Time-Domain Models and Wave Energy Converters Performance Assessment

2008 ◽  
Author(s):  
Pierpaolo Ricci ◽  
Jean-Baptiste Saulnier ◽  
Anto´nio F. de O. Falca˜o ◽  
M. Teresa Pontes
Keyword(s):  
Differential Equations ◽  
Wave Energy ◽  
Time Domain ◽  
Transfer Functions ◽  
General Scheme ◽  
Domain Model ◽  
Floating Body ◽  
Storage Device ◽  
Domain Models ◽  
Energy Chain

To evaluate the performance of a Wave Energy Converter (WEC) with realistic Power Take-Off (PTO) configurations, moorings, control systems and other contributions, time-domain models are required to deal with the non-linearities arising from the different elements of the energy chain. Future developers, in order to give a correct estimation of the expected power output of their devices, will have to apply these models and will be asked about the accuracy they can provide, particularly on what concerns the performance of the device in a determined location. A general mathematical outline of this approach was firstly proposed by Cummins by using, under linear assumptions, a classical way of representing the equation of motion of a floating body with a system of integro-differential equations with convolution terms that involve frequency-dependent coefficients. Many methods have been proposed, in literature, to solve this system in the most efficient and accurate way. Some of them relied on a direct numerical integration using standard methods for the solution of Ordinary Differential Equations, while, in turn, others are based on the approximation of the radiation convolution term with a determined number of linear sub-systems or properly chosen transfer functions. This paper presents a general scheme for a simple heaving single-body WEC, whose hydraulic Power Take-Off is coupled to a gas accumulator that serves as a storage device. Different time-domain methods will be used and compared. Particular attention will be paid to the accuracy of the performance calculation of this WPA. It is expected that the results of the simulations provide deeper understanding of the importance of the numerical parameters used in the estimation of the device performance and in this way will constitute an additional suggestion for the choice of a time-domain model for the evaluation of a WPA performance.

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