MORPACK is a MATLAB software package for MOR of finite element models (mainly stemming from ANSYS, NASTRAN, and ABAQUS) that is developed at the technical university of Dresden, Chair of Dynamics and Mechanism Design. The reduced order models generated can be reimported to the mentioned FE-software or further used in multi-body-simulation software, e.g. SIMPACK.
Objective
The utilization of elastic bodies in elastic multi-body-simulation (EMBS) is state of the art, when simulating dynamic processes close to reality in machinery and its drive trains. The generation of elastic bodies based on FE-models makes up a crucial step, which nevertheless is little standardized yet. The whole process chain including model preparation, model reduction and export of the elastic body requires a lot of sub steps in different software. Thus, the process is barely automated, little user-friendly and very error-prone due to the variety of possible settings. The aim of the software MORPACK is to overcome these drawbacks. In the first place all sub steps and set-tings are systematized. In the following, the settings shall be determined automatically depending on the model, leading to the greatest possible automatization and standardization of the whole process.
The tool MORPACK is designed to reduce and validate FE-models by using alternative reduction techniques and suitable correlation techniques. By using MORPACK, the whole process for generating elastic bodies is combined in one tool. The generation is done automatically using a comfortable GUI and tailored to the special user requirements within the EMBS-process. MORPACK acts as an interface between FE-program and MBS-software.
MORPACK is completely implemented in MATLAB and under research at the moment. The software is extended and improved continuously. Currently, MORPACK is not commercially available. For research-related cooperation or student research projects a temporary test version can be provided.
Features
Model order reduction with conventional FE-software:
- 2 available reduction methods: Guyan-reduction and Component-Mode-Synthesis (CMS), e.g. in ANSYS
- no elaborate validation
- no user feedback
- no automatization
Advantages of MORPACK compared to conventional FE-software:
- qualitatively better reduced and smaller models compared to standard techniques by using sophisticated reduction methods
- reduction quality independent from choice of master-nodes
- efficient data handling
- large variety of methods and selections for advanced users
- standard selections for beginners, which were determined by numerous tests
Module overview of MORPACK
- Import-Module: interfaces for different software packages available (ABAQUS, ANSYS, NASTRAN and SIMPACK) as well as import of measurement data from experimental modal analyses
- Connection-Module: automated definition of interface connections (rigid/elastic)
- Additional-Nodes-Module: automated and optimal selection of additional master-nodes (for correlation and reduc-tion purposes)
- Reduction-Module: numerous combined reduction methods for generation of minimal models (including back-transformation as well as generation of additional modes)
- Correlation-Module: numerous correlation methods for validation of interface connections and reduction quality (based upon modal data, frequency response function and system matrices)
- Export-Module: model export to SIMPACK, ANSYS and NASTRAN
- EMBS-Module: simplified and 3-dimensional EMBS-algorithm in MATLAB for validation of elastic bod-ies and consideration of boundary conditions under inset-conditions (EMBS-assembly)
Further features:
- modular concept for individual solutions
- implemented in MATLAB with comfortable GUI and batch-modus
- interactive help and user feedback including plausibility check
- models with a degree of freedom larger 1 Mio. can be handled on conventional desktop PCs
- for larger models an out-of-core library can be used
Reduction Module
The core of MORPACK is the reduction-module. A total of 12 basic methods including conventional and modern methods are available. By an appropriate combination (multi-step methods) 6 further methods are possible, leading to minimal models. For the calculation, 8 solvers are available, whereby a suitable solver is proposed depending on the reduction method used.
MOR-features:
- conventional reduction methods (e.g. Guyan, CMS, IRS, SEREP)
- modern methods (e.g. Krylov-subspace method, second order balanced truncation)
- generation of minimal models by using multi-step methods and mode-truncation
- generation of reliable models by application of convergence criteria
- methods with semi-automated parameter choice (e.g. Krylov-subspace-method with convergence criterion)
- large variety of methods and selections for advanced users as well as optimised standard selections for beginners
- back-transformation into physical configuration space for a physical interpretation of the reduced order model
- definition of additional modes (e.g. FRM)
References
- M. Beitelschmidt, C. Lein. "Back-Transformation into Physical Configuration Space after Model Order Reduction onto a General Subspace". PAMM-Proceedings of Applied Mathematics and Mechanics, Vol. 15, November 2015, accepted.
- C. Lein, M. Beitelschmidt, D. Bernstein. "Improvement of Krylov-Subspace-Reduced Models by Iterative Mode-Truncation". 8th MathMOD (Vienna International Conference on Mathematical Modelling), Vienna, Austria, 2015.
- C. Lein, M. Beitelschmidt. "Comparative study of model correlation methods with application to model order reduction". Proceedings 26th ISMA (International Conference on Noise and Vibration Engineering), Leuven, Belgium, pp. 2683-2700, 2014.
- C. Lein, M. Beitelschmidt. "MORPACK-Schnittstelle zum Import von FE-Strukturen nach SIMPACK". at-Automatisierungstechnik, vol. 60 (2012) issue 9, Germany, pp. 547-559.
- C. Lein, M. Beitelschmidt. "MORPACK interface for importing FE-structures into SIMPACK by using alternative MOR-methods". SIMPACK User Meeting, Salzburg, Austria, 2011.
- P. Koutsovasilis. "Model Order Reduction in Structural Mechanics - Coupling the Rigid and Elastic Multi Body Dynamics". Dissertation, Technische Universität Dresden, 2009.
Links
- Official website: MORPACK
- Chair of Dynamics and Mechanism Design: http://www.tu-dresden.de/mw/dmt