scholarly journals Model Reduction and Sensor Placement Methods for Finite Element Model Correlation

AIAA Journal ◽  
2016 ◽  
Vol 54 (12) ◽  
pp. 3941-3955 ◽  
Author(s):  
J. F. Mercer ◽  
G. S. Aglietti ◽  
A. M. Kiley
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Reduction ◽  
Sensor Placement ◽  
Element Model ◽  
Model Correlation

Design of Robust Vibration Controller for a Smart Panel Using Finite Element Model

2002 ◽  
Vol 124 (2) ◽  
pp. 265-276 ◽  
Author(s):  
W. Chang ◽  
Senthil V. Gopinathan ◽  
V. V. Varadan ◽  
V. K. Varadan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Reduction ◽  
State Space ◽  
State Space Model ◽  
Element Model ◽  
Robust Controller ◽  
Space Model ◽  
Smart Panel ◽  
Low Order

This paper presents a model reduction method and uncertainty modeling for the design of a low-order H∞ robust controller for suppression of smart panel vibration. A smart panel with collocated piezoceramic actuators and sensors is modeled using solid, transition, and shell finite elements, and then the size of the model is reduced in the state space domain. A robust controller is designed not only to minimize the panel vibration excited by applied uniform acoustic pressure, but also to be reliable in real world applications. This paper introduces the idea of Modal Hankel Singular values (MHSV) to reduce the finite element model to a low-order state space model with minimum model reduction error. MHSV measures balanced controllability and observability of each resonance mode to deselect insignificant resonance modes. State space modeling of realistic control conditions are formulated in terms of uncertainty variables. These uncertainty variables include uncertainty in actuators and sensors performances, uncertainty in the knowledge of resonance frequencies of the structure, damping ratio, static stiffness, unmodeled high resonance vibration modes, etc. The simplified model and the uncertainty model are combined as an integrated state space model, and then implemented in the H∞ control theory for controller parameterization. The low-order robust controller is easy to implement in an analog circuit to provide a low cost solution in a variety of applications where cost may be a limiting factor.

Impact of Accelerometer Placement on Modal Extraction of Offshore Wind Structures

2020 ◽  
Author(s):  
M. Richmond ◽  
S. Siedler ◽  
M. Häckell ◽  
U. Smolka ◽  
A. Kolios
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Sensor Placement ◽  
Element Model ◽  
Offshore Wind ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Optimal Sensor Placement ◽  
Permanent Campaign

Abstract The modal parameters extracted from a structure by accelerometers can be used for damage assessment as well as model updating. To extract modal parameters from a structure, it is important to place accelerometers at locations with high modal displacements. Sensor placement can be restricted by practical considerations, and installation might be conducted more based on engineering judgement rather than analysis. This leads to the question of how important the optimal sensor placement is, and if fewer sensors suffice to extract the modal parameters. In this work, an offshore wind substation (OSS) from the Wikinger offshore wind farm (owned by Iberdrola) is instrumented with 12, 3-axis accelerometers. This sensor setup consists of 6 sensors in a permanent campaign where sensors were placed based purely on engineering judgement, as well as 6 sensors in a temporary campaign, placed based on a placement analysis. An optimal sensor placement study was conducted using a finite element model of the structure in the software package FEMtools, resulting in optimal layouts. The temporary campaign sensors were placed such that they, in combination with the permanent campaign, can be used to complete the proposed layouts. Samples for each setup are processed using the software ARTeMIS modal to extract the mode shapes and natural frequencies through the Stochastic Subspace Identification (SSI) technique. The frequencies found by this approach are then clustered together using a k-means algorithm for a comparison within clusters. The modal assurance criterion (MAC) values are calculated for each result and compared to the finite element model from which the optimal sensor placement study was conducted. This is to match mode shapes between the two and thus determine the importance of off diagonal MAC elements in the sensor optimization process. MAC values are also calculated relative to a cluster-averaged set of eigenvectors to determine how they vary over the 1.5 months. The results show that for all sensor layouts, the three lower frequency modes are consistently identified. The most optimized sensor layout, consisting of only 3 sensors, was able to distinguish an additional, higher frequency mode which was never identified in the 6-sensor permanent layout. However, the reduced sensor layout shows slightly more scatter in the results than the 6-sensor layout. There is a higher signal to noise ratio in the temporary campaign which results in scatter. We conclude that with an optimized placement of accelerometers, more modes can be identified and distinguished. However, off diagonal elements in the original MAC matrix, as well as loss of sensor degrees of freedom, can result in additional scatter in the measurements. Some of these findings can be extended to other offshore jacket structures, such as those of wind turbines, in that it gives a better understanding of the consequence of an optimal sensor placement study.

Finite Element Model Reduction Applied to Nonlinear Impact Simulation for Squeak and Rattle Prediction

2020 ◽  
Author(s):  
Mohsen Bayani Khaknejad ◽  
Anoob Basheer ◽  
Filip Godborg ◽  
Rikard Söderberg ◽  
Casper Wickman
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Reduction ◽  
Element Model ◽  
Impact Simulation

scholarly journals A time-domain finite element model reduction method for viscoelastic linear and nonlinear systems

2015 ◽  
Vol 12 (6) ◽  
pp. 1182-1201 ◽  
Author(s):  
Antônio Marcos Gonçalves de Lima ◽  
Noureddine Bouhaddi ◽  
Domingos Alves Rade ◽  
Marcelo Belonsi
Keyword(s):  
Finite Element ◽  
Nonlinear Systems ◽  
Finite Element Model ◽  
Model Reduction ◽  
Time Domain ◽  
Reduction Method ◽  
Element Model ◽  
Linear And Nonlinear ◽  
Linear And Nonlinear Systems

MODEL REDUCTION WITH GEOMETRIC STIFFENING NONLINEARITIES FOR DYNAMIC SIMULATIONS OF MULTIBODY SYSTEMS

2013 ◽  
Vol 13 (08) ◽  
pp. 1350046 ◽  
Author(s):  
FENGXIA WANG
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Reduction ◽  
Reduction Process ◽  
Flexible Multibody Dynamics ◽  
Element Model ◽  
Reduced Model ◽  
Matrix Operation ◽  
Reduced Models ◽  
Geometric Stiffening

This work investigates the implementation of nonlinear model reduction to flexible multibody dynamics. Linear elastic theory will lead to instability issues with rotating beam-like structures, due to the neglecting of the membrane-bending coupling on the beam cross-section. During the past decade, considerable efforts have been focused on the derivation of geometric nonlinear formulation based on nodal coordinates. In order to reduce the computation cost in flexible multibody dynamics, which is extremely important for complex large system simulations, modal reduction is usually implemented to a rotating flexible structure with geometric nonlinearities retained in the model. In this work, a standard model reduction process based on matrix operation is developed, and the essential geometric stiffening nonlinearities are retained in the reduced model. The time responses of a tip point on a rotating Euler–Bernoulli blade are calculated based on two nonlinear reduced models. The first reduced model is derived by the standard matrix operation from a full finite element model and the second reduced model is obtained via the Galerkin method. The matrix operation model reduction process is validated through the comparison of the simulation results obtained from these two different reduced models. An interesting phenomenon is observed in this work: In the nonlinear model, if only quadratic geometric stiffing term is retained, the two reduced models converge to the full finite element model with only one bending mode and two axial modes. While if both quadratic and cubic geometric stiffing terms are retained in the nonlinear equation, the modal-based reduced model will not converge to the finite element model unless all eigenmodes are retained, that is the reduced model has no degree of freedom reduction at all.

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