Concepts and methods

Momentum balance implementation in Dymola

Written by: Maura Gallarotti – Project Engineer When starting to work on fluids in Dymola, it is of paramount importance to build base classes where the momentum, energy and mass balances are performed, in order to have a common base class for several models and a strong foundation to build your own library. A good starting read more

Posted on Monday, March 27th, 2017

Linearised Mean Value Engine Model-based Idle Control

Written by: Xiaoran Han – Project Engineer 1. Introduction PID controllers have been widely used for control design due to their simplicities and non-model based design. However, they lack robustness with respect to uncertainties and external disturbances. This blog post describes a method for developing a mean value model of intake manifold pressure and engine speed read more

Posted on Friday, March 10th, 2017

Hierarchical Connectors in Dymola

Written by: Romain Gillot – Project Engineer A convenient way to pass a number of variables/signals between components or subsystems in Dymola is to use hierarchical connectors. Modelica supports hierarchical connectors (Connectors which contain sub connectors). As a result, it is possible to connect several sub connectors together with a reduced number of connection lines. read more

Posted on Friday, February 24th, 2017

Dymola/Modelica: Tips & Tricks – Part 1: ‘Li-ion Battery Partial Modelling and Parameterisation’

Written by: Raees B. K. Parambu – project Engineer Download a copy of this article as a pdf: Dymola  Modelica: Tips & Tricks – Part 1: ‘Li-ion Battery Partial Modelling and Parameterisation’ Abstract This article is aimed to present a methodology to develop a partial acasual equivalent-circuit based model (ECM) of Lithium-ion (Li-ion) battery in Dymola, read more

Posted on Friday, February 17th, 2017

Stability Analysis in Dymola – Part 2

Written by: Sas Harrison – Systems Engineer Anatomy of Linear Feedback – Closed Loops & Root Loci Introduction This article will explain the nature of linear feedback. Models laid out intuitively in the DYMOLA GUI are connected systematically with the ideas of Laplace-domain block diagrams commonly used in controller development, while the concepts of proportional, integral & read more

Posted on Friday, February 10th, 2017

Comparing the optimisation of gear ratios for different drive cycles

Written by: David Briant – Project Engineer When considering fuel consumption tests, comparatively little information is required to generate a reasonable understanding of the effects of changes to a vehicle’s design. In Europe, the fuel consumption of a vehicle is evaluated using the New European Drive Cycle (NEDC), with the United States the equivalent termed the read more

Posted on Monday, February 6th, 2017

Understanding State Selection in Multibody Simulation

Written by: Theodor Ensbury – Project Engineer Unique to Modelica based tools, such as Dymola, state selection is a topic which affects every model produced which can manifest itself in several possible ways; a brief introduction and overview to the topic of state selection can be found here. Ever seen a multibody simulation initialise in an apparently read more

Posted on Friday, January 27th, 2017

Exporting Models & Licensing

Written by: Garron Fish – Chief Engineer Introduction This article looks at the different model export methods, their limitations and the respective Dymola licensing requirements. Ways to Export a Model  Models can be exported in several different forms: Executable Whenever a model is translated, an executable file is created, called dymosim.exe. When the model is simulated read more

Posted on Friday, January 20th, 2017

Stability Analysis in Dymola – Part 1

Written by: Sas Harrison – Systems Engineer Introduction This article introduces several ideas that provide foundations for stability analysis in DYMOLA. Those ideas have several applications, including the creation of root locus diagrams, which provide information about transient behaviour (and therefore stability) and assessment of frequency-response that details how well an input is translated to read more

Posted on Monday, January 9th, 2017

Reading structures from .mat files

Written by: Garron Fish – Chief Engineer This blog post shows how to assign Dymola model parameters to elements of a structure stored in a .mat file. In Modelica 3.2.2 a new function is introduced called Modelica.Utilities.Stream.readRealMatrix() which allows users to read a Matlab .mat file saved in the v4, v6 or v7 formats (see Figure read more

Posted on Tuesday, January 3rd, 2017

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