A Frequency Domain Identification Scheme for Flexible Structure Control

1990 ◽  
Vol 112 (3) ◽  
pp. 427-434 ◽  
Author(s):  
A. P. Tzes ◽  
S. Yurkovich
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Time Domain ◽  
Flexible Manipulator ◽  
Flexible Structure ◽  
Structure Control ◽  
Identification Schemes ◽  
Domain Identification ◽  
Frequency Domain Methods ◽  
Self Tuning

Transfer function identification schemes for use in self-tuning control applications are considered. Frequency domain methods generally require less computational load than time domain methods, and for certain classes of systems may be more accurate. For control purposes, however, a time domain parameterization of the system transfer function is often preferred, because of the direct relationship to controller parameters. In this paper we present a new method called Time-varying Transfer Function Estimation (TTFE) in which system parameters are computed through identification in the frequency domain. The method is particularly well suited for flexible structure control problems, and a self-tuning control law with frequency shaping is derived and demonstrated on a flexible manipulator system.

Frequency Domain Identification Experiment on a Large Flexible Structure

1989 ◽  
Author(s):  
D.S. Bayard ◽  
F.Y. Hadaegh ◽  
Y. Yam ◽  
R.E. Scheid ◽  
E. Mettler ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Flexible Structure ◽  
Domain Identification ◽  
Frequency Domain Identification

A Frequency Domain Versus a Time Domain Identification Technique for Nonlinear Parameters Applied to Wire Rope Isolators

2000 ◽  
Vol 123 (4) ◽  
pp. 645-650 ◽  
Author(s):  
Gaetan Kerschen ◽  
Vincent Lenaerts ◽  
Stefano Marchesiello ◽  
Alessandro Fasana
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Nonlinear Dynamical Systems ◽  
Wire Rope ◽  
Restoring Force ◽  
Nonlinear Parameters ◽  
Nonlinear Dynamical ◽  
Domain Identification ◽  
Identification Technique ◽  
Reverse Path Method

The present paper aims to compare two techniques for identification of nonlinear dynamical systems. The Conditioned Reverse Path method, which is a frequency domain technique, is considered together with the Restoring Force Surface method, a time domain technique. Both methods are applied for experimental identification of wire rope isolators and the results are compared. Finally, drawbacks and advantages of each technique are underlined.

On the Application of Frequency-Domain Methods to Multistage Turbomachinery

2015 ◽  
Author(s):  
Laura Junge ◽  
Graham Ashcroft ◽  
Peter Jeschke ◽  
Christian Frey
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Harmonic Balance ◽  
Axial Compressor ◽  
Harmonic Balance Method ◽  
Nonlinear Frequency ◽  
Solution Quality ◽  
Multi Stage ◽  
Frequency Domain Methods ◽  
Blade Row

Due to the relative motion between adjacent blade rows the aerodynamic flow fields within turbomachinery are normally dominated by deterministic, periodic phenomena. In the numerical simulation of such unsteady flows (nonlinear) frequency-domain methods are therefore attractive as they are capable of fully exploiting the given spatial and temporal periodicity, as well as capturing or modelling flow nonlinearity. Central to the efficiency and accuracy of such frequency-domain methods is the selection of the frequencies and the circumferential modes to be resolved in simulations. Whilst trivial in the context of the simulation of a single compressor- or turbine-stage, the choice of solution modes becomes substantially more involved in multi-stage configurations. In this work the importance of mode scattering, in the context of the unsteady aerodynamic field, is investigated and quantified. It is shown that scattered modes can substantially impact the unsteady flow field and are essential for the accurate modelling of wake propagation within multistage configurations. Furthermore, an iterative approach is outlined, based on the spectral analysis of the circumferential modes at the interfaces between blade rows, to identify the dominant solution modes that should be resolved in the adjacent blade row. To demonstrate the importance of mode scattering and validate the approach for their identification the unsteady blade row interaction within a 4.5 stage axial compressor is computed using both the harmonic balance method and, based on a full annulus midspan simulation, a time-domain method. Through the inclusion of scattered modes it is shown that the solution quality of the harmonic balance results is comparable to that of the nonlinear time-domain simulation.

On Frequency-Domain and Time-Domain Input Shaping for Multi-Mode Flexible Structures

2003 ◽  
Vol 125 (3) ◽  
pp. 494-497 ◽  
Author(s):  
Lucy Y. Pao ◽  
Craig F. Cutforth
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Flexible Structures ◽  
Design Methods ◽  
Input Shaping ◽  
Residual Vibration ◽  
Know How ◽  
Frequency Domain Methods ◽  
Multi Mode

The technique of input shaping has been successfully applied to the problem of maneuvering flexible structures without excessive residual vibration. Because a shaper is designed such that vibration is eliminated at the end of the shaped input, a short shaper length means that vibration is eliminated sooner. As different shaper design methods yield different shapers, it is advantageous to know how the shaper lengths of these different methods compare. In this paper we draw comparisons between time-domain input shaping methods and frequency-domain input shaping methods after outlining conditions when non-negative amplitude shapers exist when using frequency-domain methods.

Application of an Advanced Frequency Domain Identification Method for Modelling of Flexible-Link Manipulators

2003 ◽  
Author(s):  
G. M. Y. Lai ◽  
K. Ziaei ◽  
D. W. L. Wang ◽  
G. R. Heppler
Keyword(s):  
System Identification ◽  
Transfer Function ◽  
Frequency Domain ◽  
Contact Force ◽  
Strain Gauges ◽  
Flexible Link ◽  
Domain Identification ◽  
Frequency Responses ◽  
System Frequency ◽  
Identification Tool

This paper investigates the Comprehensive Identification from FrEquency Responses (CIFER) technique as a system identification tool for the Single Flexible Link (SFL) manipulator system. Frequency responses are identified for both the constrained and unconstrained motions. For the constrained case, two sets of frequency responses are identified based on actual contact force and an approximated contact force obtained through strain gauges readings. Identification results from CIFER® are compared to those from the Empirical Transfer Function Estimate (ETFE).

scholarly journals Sex Differences in Time-Domain and Frequency-Domain Heart Rate Variability Measures of Fatigued Drivers

2020 ◽  
Vol 17 (22) ◽  
pp. 8499
Author(s):  
Chao Zeng ◽  
Wenjun Wang ◽  
Chaoyang Chen ◽  
Chaofei Zhang ◽  
Bo Cheng
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Sex Differences ◽  
Frequency Domain ◽  
Time Domain ◽  
Mental States ◽  
Male And Female ◽  
Frequency Domain Methods ◽  
The Difference ◽  
Electrocardiogram Ecg

The effects of fatigue on a driver’s autonomic nervous system (ANS) were investigated through heart rate variability (HRV) measures considering the difference of sex. Electrocardiogram (ECG) data from 18 drivers were recorded during a simulator-based driving experiment. Thirteen short-term HRV measures were extracted through time-domain and frequency-domain methods. First, differences in HRV measures related to mental state (alert or fatigued) were analyzed in all subjects. Then, sex-specific changes between alert and fatigued states were investigated. Finally, sex differences between alert and fatigued states were compared. For all subjects, ten measures showed significant differences (Mann-Whitney U test, p < 0.01) between different mental states. In male and female drivers, eight and four measures, respectively, showed significant differences between different mental states. Six measures showed significant differences between males and females in an alert state, while ten measures showed significant sex differences in a fatigued state. In conclusion, fatigue impacts drivers’ ANS activity, and this impact differs by sex; more differences exist between male and female drivers’ ANS activity in a fatigued state than in an alert state.

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