scholarly journals A generalized constraint reduction method for reduced order MBS models

2016 ◽  
Vol 41 (3) ◽  
pp. 259-274 ◽  
Author(s):  
Daniel Stadlmayr ◽  
Wolfgang Witteveen ◽  
Wolfgang Steiner
Keyword(s):  
Reduction Method ◽  
Constraint Reduction ◽  
Reduced Order ◽  
Generalized Constraint

scholarly journals A hyper-reduction method using adaptivity to cut the assembly costs of reduced order models

2021 ◽  
Vol 380 ◽  
pp. 113723
Author(s):  
Jack S. Hale ◽  
Elisa Schenone ◽  
Davide Baroli ◽  
Lars A.A. Beex ◽  
Stéphane P.A. Bordas
Keyword(s):  
Reduction Method ◽  
Reduced Order Models ◽  
Reduced Order

scholarly journals A Reduced-Order Model of Detuned Cyclic Dynamical Systems With Geometric Modifications Using a Basis of Cyclic Modes

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Moustapha Mbaye ◽  
Christian Soize ◽  
Jean-Philippe Ousty
Keyword(s):  
Reduction Method ◽  
Reduced Order Model ◽  
Cyclic Symmetry ◽  
Order Model ◽  
Element Analysis ◽  
Disk Model ◽  
Reduced Order ◽  
Bladed Disk ◽  
Forced Responses ◽  
Sector Matrix

A new reduction method for vibration analysis of intentionally mistuned bladed disks is presented. The method is built for solving the dynamic problem of cyclic structures with geometric modifications. It is based on the use of the cyclic modes of the different sectors, which can be obtained from a usual cyclic symmetry modal analysis. Hence the projection basis is constituted; as well as, on the whole bladed disk, each sector matrix is reduced by its own modes. The method is validated numerically on a real bladed disk model, by comparing free and forced responses of a full model finite element analysis to those of a reduced-order model using the new reduction method.

scholarly journals Empirical Reduced-Order Modeling for Boundary Feedback Flow Control

2008 ◽  
Vol 2008 ◽  
pp. 1-11 ◽  
Author(s):  
Seddik M. Djouadi ◽  
R. Chris Camphouse ◽  
James H. Myatt
Keyword(s):  
Model Reduction ◽  
Reduction Method ◽  
Linear Subspace ◽  
Balanced Truncation ◽  
Order Model ◽  
Reduced Order ◽  
Domain Identification ◽  
Controllability And Observability ◽  
Obstacle Geometry ◽  
Proper Orthogonal

This paper deals with the practical and theoretical implications of model reduction for aerodynamic flow-based control problems. Various aspects of model reduction are discussed that apply to partial differential equation- (PDE-) based models in general. Specifically, the proper orthogonal decomposition (POD) of a high dimension system as well as frequency domain identification methods are discussed for initial model construction. Projections on the POD basis give a nonlinear Galerkin model. Then, a model reduction method based on empirical balanced truncation is developed and applied to the Galerkin model. The rationale for doing so is that linear subspace approximations to exact submanifolds associated with nonlinear controllability and observability require only standard matrix manipulations utilizing simulation/experimental data. The proposed method uses a chirp signal as input to produce the output in the eigensystem realization algorithm (ERA). This method estimates the system's Markov parameters that accurately reproduce the output. Balanced truncation is used to show that model reduction is still effective on ERA produced approximated systems. The method is applied to a prototype convective flow on obstacle geometry. AnH∞feedback flow controller is designed based on the reduced model to achieve tracking and then applied to the full-order model with excellent performance.

A Model Reduction Method for Bladed Disks With Large Geometric Mistuning Using a Partially Reduced Intermediate System Model

2020 ◽  
Author(s):  
Lukas Schwerdt ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Reduction Method ◽  
Axial Compressor ◽  
Reduction Process ◽  
Computational Effort ◽  
System Model ◽  
Bladed Disks ◽  
Element Mesh ◽  
Modal Expansion ◽  
Reduced Order ◽  
Intermediate System

Abstract Reduced order models (ROMs) are widely used to enable efficient simulation of mistuned bladed disks. ROMs based on projecting the system dynamics into a subspace spanned by the modes of the tuned structure work well for small amounts of mistuning. When presented with large mistuning, including changes of geometry and number of finite element mesh nodes, advanced methods such as the the pristine-rogue-interface modal expansion (PRIME) are necessary. PRIME builds a reduced model from two full cyclic symmetric analyses, one for the nominal and one for the modified type of sector. In this paper a new reduced order model suitable for large mistuning with arbitrary mesh modifications is presented. It achieves higher accuracy than PRIME, while saving approximately 25% computational effort during the reduction process, when using the same number of cyclic modes. The new method gains its efficiency by recognizing that large modifications from damage or repair are unlikely to be exactly the same for multiple blades. It works by building a partially reduced intermediate model: All nominal sectors are reduced using cyclic modes of the tuned structure. The single modified sector is kept as the full model. For this reason, the new reduction method is called Partially Reduced Intermediate System Model (PRISM) method. The accuracy of the PRISM method is demonstrated on an axial compressor blisk and an academic blisk geometry.

A Model Reduction Method for Bladed Disks with Large Geometric Mistuning Using a Partially Reduced Intermediate System Model

2020 ◽  
Author(s):  
Lukas Schwerdt ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Reduction Method ◽  
Axial Compressor ◽  
Reduction Process ◽  
Computational Effort ◽  
System Model ◽  
Bladed Disks ◽  
Element Mesh ◽  
Modal Expansion ◽  
Reduced Order ◽  
Intermediate System

Abstract Reduced order models (ROMs) are widely used to enable efficient simulation of mistuned bladed disks. ROMs based on projecting the system dynamics into a subspace spanned by the modes of the tuned structure work well for small amounts of mistuning. When presented with large mistuning, including changes of geometry and number of finite element mesh nodes, advanced methods such as the the pristine-rogue-interface modal expansion (PRIME) are necessary. PRIME builds a reduced model from two full cyclic symmetric analyses, one for the nominal and one for the modified type of sector. In this paper a new reduced order model suitable for large mistuning with arbitrary mesh modifications is presented. It achieves higher accuracy than PRIME, while saving approximately 25% computational effort during the reduction process, when using the same number of cyclic modes. The new method gains its efficiency by recognizing that large modifications from damage or repair are unlikely to be exactly the same for multiple blades. It works by building a partially reduced intermediate model: All nominal sectors are reduced using cyclic modes of the tuned structure. The single modified sector is kept as the full model. For this reason, the new reduction method is called Partially Reduced Intermediate System Model (PRISM) method. The accuracy of the PRISM method is demonstrated on an axial compressor blisk and an academic blisk geometry.

Reduced-Order Modeling of Bladed Disks Considering Small Mistuning of the Disk Sectors

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Lukas Schwerdt ◽  
Sebastian Willeke ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Reduction Method ◽  
Order Reduction ◽  
Bladed Disks ◽  
Small Disk ◽  
Model Order ◽  
Reduced Order ◽  
Mass Matrices ◽  
Dense Matrices ◽  
The Individual ◽  
Order Reduction Method

A model order reduction method based on the component mode synthesis for mistuned bladed disks is introduced, with one component for the disk and one component for each blade. The interface between the components at the blade roots is reduced using the wave-based substructuring (WBS) method, which employs tuned system modes. These system modes are calculated first, and used subsequently during the reduction of the individual components, which eliminates the need to build a partially reduced intermediate model with dense matrices. For the disk, a cyclic Craig–Bampton (CB) reduction is applied. The deviations of the stiffness and mass matrices of individual disk sectors are then projected into the cyclic basis of interior and interface modes of the disk substructure. Thereby, it is possible to model small disk mistuning in addition to large mistuning of the blades.

Reduced-Order H∞ Controller Design Using the μ-Synthesis Applied to Lateral Control of Highly Flexible Aircraft

2013 ◽  
Vol 373-375 ◽  
pp. 1374-1377
Author(s):  
Li Zhang ◽  
Shuai Tang ◽  
Zhi Qiang Zheng
Keyword(s):  
Reduction Method ◽  
Controller Design ◽  
Order Reduction ◽  
Reduced Order Model ◽  
Balanced Truncation ◽  
Order Model ◽  
Flexible Aircraft ◽  
Reduced Order ◽  
Analysis And Synthesis ◽  
Time Domains

A lateral flight reduced-order controller for a flexible aircraft is presented. It is based on the reduced-order model of the flexible aircraft and theμ-analysis and synthesis toolbox. The first step deals with the order reduction of the full-model by using the balanced-truncation model reduction method. Then the reduced-orderHcontroller is achieved by using theμ-analysis and synthesis theory and applied to the reduced-order model and full-order model of the flexible aircraft. Finally, numerical results are presented and discussed. The simulation results show the efficiency of the reduced-order controller based on the reduced-order model since the close-loop system of the full-order model meets a set of realistic specifications in the frequency and time domains.

A Comparison of Two Reduced Order Methods for Probabilistic Mistuning Investigations

2017 ◽  
Author(s):  
Christian U. Waldherr ◽  
Damian M. Vogt
Keyword(s):  
Reduction Method ◽  
Periodic Structures ◽  
Rotating Machinery ◽  
Theoretical Point ◽  
Reduced Order Models ◽  
Structural Dynamic ◽  
Turbine Wheel ◽  
Reduced Order ◽  
Reduction Methods ◽  
Reduced Order Methods

Slight variances in the manufacturing of rotating machinery can lead to significant changes in the structural dynamic behavior compared to the behavior of ideal cyclic periodic structures. Therefore it is necessary to consider deviations from the perfect cyclic periodic structures in the mechanical design process of rotating machinery. To minimize the effort of numerical calculations, the application of reduced order models is indispensable. The objective of this paper is the comparison of two reduction methods which are not widespread in application of rotationally periodic structures. For the validation of the implemented methods, a generic model of a thin plate meshed with shell elements and a representative large size FE model of a radial turbine wheel are used. The first reduction method is called Improved Reduced System and is based on the classical Guyan reduction. The second reduction method is called SEREP method and is from a theoretical point of view closely related to the first method although the procedure to obtain the reduction basis is quite different. The results show for both test cases an excellent agreement between the reduced order models and the unreduced finite element model. Both reduction methods are also able to capture the phenomena of mode localization. It is also found that through the application of the reduced order methods the computation time can be reduced by two orders of magnitude. Based on the first reduction method, the statistical mistuning behavior is studied using the accelerated Monte Carlo simulation.

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