1,353 research outputs found
Balanced Truncation of Networked Linear Passive Systems
This paper studies model order reduction of multi-agent systems consisting of
identical linear passive subsystems, where the interconnection topology is
characterized by an undirected weighted graph. Balanced truncation based on a
pair of specifically selected generalized Gramians is implemented on the
asymptotically stable part of the full-order network model, which leads to a
reduced-order system preserving the passivity of each subsystem. Moreover, it
is proven that there exists a coordinate transformation to convert the
resulting reduced-order model to a state-space model of Laplacian dynamics.
Thus, the proposed method simultaneously reduces the complexity of the network
structure and individual agent dynamics, and it preserves the passivity of the
subsystems and the synchronization of the network. Moreover, it allows for the
a priori computation of a bound on the approximation error. Finally, the
feasibility of the method is demonstrated by an example
Model reduction for linear delay systems using a delay-independent balanced truncation approach
A model reduction approach for asymptotically stable linear delay-differential equations is presented in this paper. Specifically, a balancing approach is developed on the basis of energy functionals that provide (bounds on) a measure of energy related to observability and controllability, respectively. The reduced-order model derived in this way is again a delay-differential equation, such that the method is structure preserving. In addition, asymptotic stability is preserved and an a priori bound on the reduction error is derived, providing a measure of accuracy of the reduction. The results are illustrated by means of application on an example
Doped microporous hybrid silica membranes for gas separation
Hybrid silica (i.e., bis-triethoxysilylethane: BTESE) membranes doped with B, Ta or Nb were made through a sol–gel process. Triethyl borate, tantalum (V) ethoxide (TPE) and niobium (V) ethoxide (NPE) were selected as doping precursors. The doping concentration was optimized to produce sols, suitable for membrane fabrication. Thermal stability, structural analysis, cross-sectional micrographs and single gas permeation experiments were performed on these membranes, and results are compared with an undoped BTESE membrane. It was observed that the synthesized doped BTESE materials and membranes resulted into a more open (and, in one occurrence, SF6 permeable) pore microstructure, showing high permeances of larger gas molecules, while having a cross-sectional thickness comparable to undoped BTESE membrane
Mode Selection for Component Mode Synthesis with Guaranteed Assembly Accuracy
In this work, a modular approach is introduced to select the most important
eigenmodes for each component of a composed structural dynamics system to
obtain the required accuracy of the reduced-order assembly model. To enable the
use of models of complex (structural) dynamical systems in engineering
practice, e.g., in a design, optimization and/or control context, the
complexity of the models needs to be reduced. When the model consist of an
assembly of multiple interconnected structural components, component mode
synthesis is often the preferred model reduction method. The standard approach
to component mode synthesis for such system is to select the eigenmodes of a
component that are most important to accurately model the dynamic behavior of
this component in a certain frequency range of interest. However, often, a more
relevant goal is to obtain, in this frequency range, an accurate model of the
assembly. In the proposed approach, accuracy requirements on the level of the
assembly are translated to accuracy requirements on component level, by
employing techniques from the field of systems and control. With these
component-level requirements, the eigenmodes that are most important to
accurately model the dynamic behavior of the assembly can be selected in a
modular fashion. We demonstrate with two structural dynamics benchmark systems
that this method based on assembly accuracy allows for a computationally
efficient selection of eigenmodes that 1) guarantees satisfaction of the
assembly accuracy requirements and 2) results in most cases in reduced-order
models of significantly lower order with respect to the industrial standard
approach in which component eigenmodes are selected using a frequency
criterion
Translating Assembly Accuracy Requirements to Cut-Off Frequencies for Component Mode Synthesis
One of the most popular methods for reducing the complexity of assemblies of
finite element models in the field of structural dynamics is component mode
synthesis. A main challenge of component mode synthesis is balancing model
complexity and model accuracy, because it is difficult to predict how component
reduction influences assembly model accuracy. This work introduces an approach
that allows for the translation of assembly model accuracy requirements in the
frequency domain to the automatic selection of the cut-off frequencies for the
model-order reduction (MOR) of components. The approach is based on a
mathematical approach for MOR for coupled linear systems in the field of
systems and control. We show how this approach is also applicable to structural
dynamics models. We demonstrate the use of this approach in the scope of
component mode synthesis (CMS) methods with the aim to reduce the complexity of
component models while guaranteeing accuracy requirements of the assembly
model. The proposed approach is illustrated on a mechanical, three-component
structural dynamics system for which reduced-order models are computed that are
reduced further compared to reduction using standard methods. This results in
lower simulation cost, while maintaining the required accuracy
Modular Redesign of Mechatronic Systems: Formulation of Module Specifications Guaranteeing System Dynamics Specifications
Complex mechatronic systems are typically composed of interconnected modules,
often developed by independent teams. This development process challenges the
verification of system specifications before all modules are integrated. To
address this challenge, a modular redesign framework is proposed in this paper.
Herein, first, allowed changes in the dynamics (represented by frequency
response functions (FRFs)) of the redesigned system are defined with respect to
the original system model, which already satisfies system specifications.
Second, these allowed changes in the overall system dynamics (or system
redesign specifications) are automatically translated to dynamics (FRF)
specifications on module level that, when satisfied, guarantee overall system
dynamics (FRF) specifications. This modularity in specification management
supports local analysis and verification of module design changes, enabling
design teams to work in parallel without the need to iteratively rebuild the
system model to check fulfilment of system FRF specifications. A modular
redesign process results that shortens time-to-market and decreases redesign
costs. The framework's effectiveness is demonstrated through three examples of
increasing complexity, highlighting its potential to enable modular mechatronic
system (re)design
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