Corrections and Comments to “Model Reduction of Discrete Linear Systems Via Frequency-Domain Balanced Structure”

2007 ◽  
Vol 54 (3) ◽  
pp. 682-683 ◽  
Author(s):  
Natthoo Lal Prajapati ◽  
Dinesh Chandra ◽  
Devarakonda Seshachalam
Keyword(s):  
Model Reduction ◽  
Frequency Domain ◽  
Linear Systems ◽  
Discrete Linear Systems ◽  
Balanced Structure

Principle of frequency-domain balanced structure in linear systems and model reduction

2003 ◽  
Vol 29 (3) ◽  
pp. 463-477 ◽  
Author(s):  
P. Karim Aghaee ◽  
Ali Zilouchian ◽  
S. Nike-Ravesh ◽  
Abbas H. Zadegan
Keyword(s):  
Model Reduction ◽  
Frequency Domain ◽  
Linear Systems ◽  
Balanced Structure

scholarly journals Discussion: “Model Reduction of Large-Scale Discrete Plants With Specified Frequency Domain Balanced Structure” (Zadegan, A., and Zilouchian, A., 2005, ASME J. Dyn. Syst. Meas., Control, 127, pp. 486–498)

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Hamid Reza Shaker ◽  
Rafael Wisniewski
Keyword(s):  
Model Reduction ◽  
Frequency Domain ◽  
Large Scale ◽  
Reduction Method ◽  
Order Reduction ◽  
Balanced Structure ◽  
Order Reduction Method

This work presents a commentary of the article published by A. Zadegan and A. Zilouchian (2005, ASME J. Dyn. Syst. Meas., Control, 127, pp. 486–498). We show their order reduction method is not always true and may lead to inaccurate results and is therefore erroneous. A framework for solving the problem is also suggested.

Model Reduction of Large-Scale Discrete Plants With Specified Frequency Domain Balanced Structure

2004 ◽  
Vol 127 (3) ◽  
pp. 486-498 ◽  
Author(s):  
Abbas H. Zadegan ◽  
Ali Zilouchian
Keyword(s):  
Model Reduction ◽  
Frequency Domain ◽  
Large Scale ◽  
Linear Time ◽  
Model Simulation ◽  
Large Scale Systems ◽  
Linear Time Invariant ◽  
Balanced Structure ◽  
Linear Time Invariant Systems ◽  
Model Reduction Technique

A new model reduction technique for linear time-invariant systems is proposed. A new method that reduces the order of large-scale systems by integrating singular perturbation with specified frequency domain balanced structure is proposed. Considering a frequency range at which the system actually operates guarantees a good approximation of the original full order model. Simulation experiments for model reduction of several large-scale systems demonstrate the effectiveness of the proposed technique.

Time-Domain Nonlinear SSI Analysis of Foundation Sliding Using Frequency-Dependent Foundation Impedance Derived From SASSI

2008 ◽  
Author(s):  
Mansour Tabatabaie ◽  
Thomas Ballard
Keyword(s):  
Frequency Domain ◽  
Linear Systems ◽  
Time Domain ◽  
Soil Structure ◽  
Wave Radiation ◽  
Far Field ◽  
Frequency Dependent ◽  
Nonlinear Springs ◽  
Mat Foundation ◽  
The Time Domain

Dynamic soil-structure interaction (SSI) analysis of nuclear power plants is often performed in frequency domain using programs such as SASSI [1]. This enables the analyst to properly a) address the effects of wave radiation in an unbounded soil media, b) incorporate strain-compatible soil shear modulus and damping properties and c) specify input motion in the free field using the de-convolution method and/or spatially variable ground motions. For structures that exhibit nonlinearities such as potential base sliding and/or uplift, the frequency-domain procedure is not applicable as it is limited to linear systems. For such problems, it is necessary to solve the problem in the time domain using the direct integration method in programs such as ADINA [2]. The authors recently introduced a sub-structuring technique called distributed parameter foundation impedance (DPFI) model that allows the structure to be partitioned from the total SSI system and analyzed in the time domain while the foundation soil is modeled using the frequency-domain procedure [3]. This procedure has been validated for linear systems. In this paper we have expanded the DPFI model to incorporate nonlinearities at the soil/structure interface by introducing nonlinear shear and normal springs arranged in series between the DPFI and structure model. This combination of the linear far-field impedance (DPFI) plus nonlinear near-field soil springs allows the foundation sliding and/or uplift behavior be analyzed in time domain while maintaining the frequency-dependent stiffness and radiation damping nature of the far-field foundation impedance. To check the accuracy of this procedure, a typical NPP foundation mat supported at the surface of a layered soil system and subjected to harmonic forced vibration was first analyzed in the frequency domain using SASSI to calculate the target linear response and derive a linear, far-field DPFI model. The target linear solution was then used to validate two linear time-domain ADINA models: Model 1 consisting of the mat foundation+DPFI derived from the linear SASSI model and Model 2 consisting of the total SSI system (mat foundation plus a soil block). After linear alignment, the nonlinear springs were added to both ADINA models and re-analyzed in time domain. Model 2 provided the target nonlinear solution while Model 1 provided the results using the DPFI+nonlinear springs. By increasing the amplitude of the vibration load, different levels of foundation sliding were simulated. Good agreement between the results of two models in terms of the displacement response of the mat and cyclic force-displacement behavior of the springs validates the accuracy of the procedure presented herein.

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