Sensitivity of NL-RDM to Errors in the Non-Linear Test Process

2009 ◽  
Author(s):  
Mehdi Sarmast ◽  
Saeed Bostan Manesh M. ◽  
Mahmood R. Mehran
Keyword(s):  
System Identification ◽  
Linear System ◽  
Continuous Systems ◽  
Negative Effects ◽  
Practical Applications ◽  
Lumped Parameter ◽  
Non Linear ◽  
Linear System Identification ◽  
Non Linear System ◽  
Test Process

NL-RDM is a non-linear system identification method that combines a number of linear and non-linear system identification methods and offers a practical approach to the identification of lumped parameter and continuous systems using a classical linear modal model with additional non-linear terms. The method was started by identifying the modal parameters of the underlying linear system via the FRF, MMIF and appropriated force vector. The criteria for an ideal method are detailed in the some earlier papers, but the reality creates a limitation. This paper is divided into several sections relating to the “Nonlinear Test Process”. Error which arise from test, environmental and equipment effects, are quantization errors, input (or process) noise and measurement noise. So, the effects of these inaccuracies and possible solutions for decreasing any negative effects are considered. Then, The sensitivities to noise and quantization which could be encountered in practical applications of the NL-RDM, are discussed in concept, generated, applied and analyzed through simulation programme for two degree of freedom uncoupled and coupled examples.

Non-linear system identification and fault diagnosis using a new GUI interpretation tool

2001 ◽  
Vol 54 (6) ◽  
pp. 425-449 ◽  
Author(s):  
Jui-Jung Liu ◽  
Shan-Jen Cheng ◽  
I-Chung Kung ◽  
Hui-Chen Chang ◽  
S.A. Billings
Keyword(s):  
Fault Diagnosis ◽  
System Identification ◽  
Linear System ◽  
Non Linear ◽  
Linear System Identification ◽  
Non Linear System

scholarly journals Current efforts towards a non-linear system identification methodology of broad applicability

2011 ◽  
Vol 225 (11) ◽  
pp. 2497-2515 ◽  
Author(s):  
A F Vakakis ◽  
L A Bergman ◽  
D M McFarland ◽  
Y S Lee ◽  
M Kurt
Keyword(s):  
System Identification ◽  
Linear System ◽  
Hilbert Transforms ◽  
Broad Applicability ◽  
Open Questions ◽  
Non Linear ◽  
Global Aspect ◽  
Linear System Identification ◽  
Non Linear System ◽  
Global And Local

A review of current efforts towards developing a non-linear system identification (NSI) methodology of broad applicability [ 1 – 4 ] is provided in this article. NSI possess distinct challenges, since, even the task of identifying a set of (linearized) modal matrices modified (‘perturbed’) by non-linear corrections might be an oversimplification of the problem. In that context, the integration of diverse analytical, computational, and post-processing methods, such as slow flow constructions, empirical mode decompositions, and wavelet/Hilbert transforms to formulate a methodology that holds promise of broad availability, especially to systems with non-smooth non-linearities such as clearances, dry friction and vibro-impacts is proposed. In particular, the proposed methodology accounts for the fact that, typically, non-linear systems are energy- and initial condition-dependent, and has both global and local components. In the global aspect of NSI, the dynamics is represented in a frequency–energy plot (FEP), whereas in the local aspect of the methodology, sets of intrinsic modal oscillators are constructed to model specific non-linear transitions on the FEP. The similarity of the proposed methodology to linear experimental modal analysis is discussed, open questions are outlined, and some applications providing a first demonstration of the discussed concepts and techniques are provided.

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