Frequency domain analysis of time integration operators

1982 ◽  
Vol 10 (5) ◽  
pp. 691-697 ◽  
Author(s):  
A. Preumont
Keyword(s):  
Frequency Domain ◽  
Time Integration ◽  
Domain Analysis ◽  
Frequency Domain Analysis

Modelling of Seabed Interaction in Frequency Domain Analysis of Mooring Cables

2003 ◽  
Author(s):  
Paul P. A. Ong ◽  
Sergio Pellegrino
Keyword(s):  
Frequency Domain ◽  
Equations Of Motion ◽  
Time Integration ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Wave Loading ◽  
Computational Overhead ◽  
Spring System ◽  
Seabed Interaction ◽  
Domain Integration

Mooring cables under wave loading interact dynamically with the seabed; this interaction is nonlinear and can be modelled in full only by performing lengthy time integration of the equations of motion. However, time domain integration is far too computationally expensive to be carried out for all load cases. A new method of modelling the interaction between a cable and the seabed in the frequency domain, but without considering frictional effects and impact, is therefore proposed. The section of cable interacting with the seabed is truncated and replaced with a system of coupled linear springs, with stiffnesses linearised from static catenary equations. These springs would model the behaviour of the truncated cable and hence the time-varying boundary condition at the touchdown. The entire cable-spring system is then analysed in the frequency domain with a centred finite difference scheme. The proposed method has shown to increase the accuracy of frequency domain analysis in certain cases with affordable computational overhead.

On the Derivation of Nonlinear and Linearized Models of Flexible Bodies in Large Global Motion

1993 ◽  
Author(s):  
Jung-Hwan Lee ◽  
John J. Uicker
Keyword(s):  
Frequency Domain ◽  
Dynamic Properties ◽  
Equations Of Motion ◽  
Time Integration ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Global Motion ◽  
Flexible Bodies ◽  
Linearized Equations ◽  
Transformation Matrices

Abstract This paper presents a systematic modeling technique for systems of flexible bodies in large global motion. 4 × 4 homogeneous coordinate transformation matrices are used together with the Finite Element Method. By using homogeneous coordinates, derivatives of the transformation matrices can be represented by differential operator matrices. Due to this fact, one can derive the equations of motion in explicit matrix form. In this paper, the derivation of the general linearized as well as the nonlinear equations of motion are presented. Two typical mechanisms are chosen to show the validity of the procedures. Time history analysis and frequency domain analysis have been done using the mechanism models. The modal time integration technique has been applied to show the validity of the linearized equations of motion. The eigenvalues and eigenvectors of the mechanisms are used for the time integration of the linearized equations. For the frequency domain analysis, plots of changes in natural frequencies of the mechanisms are shown. These results show not only the dynamic properties of the structural parts of mechanism, but also those of the rigid body motions of the mechanism.

scholarly journals Analysis of Three-Phase Wye-Delta Connected LLC

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3606
Author(s):  
Jing-Yuan Lin ◽  
Chuan-Ting Chen ◽  
Kuan-Hung Chen ◽  
Yi-Feng Lin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Operation Time ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Complete Analysis ◽  
Plane Analysis ◽  
Analysis Methods ◽  
Three Phase

Three-phase wye–delta LLC topology is suitable for voltage step down and high output current, and has been used in the industry for some time, e.g., for server power and EV charger. However, no comprehensive circuit analysis has been performed for three-phase wye–delta LLC. This paper provides complete analysis methods for three-phase wye–delta LLC. The analysis methods include circuit operation, time domain analysis, frequency domain analysis, and state–plane analysis. Circuit operation helps determine the circuit composition and operation sequence. Time domain analysis helps understand the detail operation, equivalent circuit model, and circuit equation. Frequency domain analysis helps obtain the curve of the transfer function and assists in circuit design. State–plane analysis is used for optimal trajectory control (OTC). These analyses not only can calculate the voltage/current stress, but can also help design three-phase wye-delta connected LLC and provide the OTC control reference. In addition, this paper uses PSIM simulation to verify the correctness of analysis. At the end, a 5-kW three-phase wye–delta LLC prototype is realized. The specification of the prototype is a DC input voltage of 380 V and output voltage/current of 48 V/105 A. The peak efficiency is 96.57%.

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