Conference article

Natural Unit Representation in Modelica

Kevin L. Davies
Georgia Institute of Technology, Atlanta, Georgia USA

Christiann J. J. Paredis
Georgia Institute of Technology, Atlanta, Georgia USA

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Published in: Proceedings of the 9th International MODELICA Conference; September 3-5; 2012; Munich; Germany

Linköping Electronic Conference Proceedings 76:82, p. 801-808

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Published: 2012-11-19

ISBN: 978-91-7519-826-2

ISSN: 1650-3686 (print), 1650-3740 (online)


A method is presented by which alternative systems of physical units may be represented and utilized in Modelica. The method may be useful in simulating models of physical systems where the base units of the International System of Units (SI)--the standard unit system in Modelica--are poorly scaled. It also provides a convenient means to express the values of physical quantities in fields of science and engineering where data is typically represented in other systems of units or constants (i.e.; "natural units"). By explicitly expressing the value of a physical quantity as the product of a number and a unit (where the unit is an algebraic variable); the method uses variables that are unit-neutral. Unfortunately; workarounds are necessary in order to implement the method in the current version of the Modelica language. Nonetheless; it may be useful in special applications; and the related discussion may provide valuable insight. In particular; it is shown that there is an apparent conflict in the interpretation of "number" and "value" between Modelica and the International Bureau of Weights and Measures (BIPM).


natural units; physical quantities; Modelica; SI


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