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Negative displacements of translational springs should be permitted #446

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modelica-trac-importer opened this issue Jan 14, 2017 · 6 comments
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Negative displacements of translational springs should be permitted #446

modelica-trac-importer opened this issue Jan 14, 2017 · 6 comments
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bug Critical/severe issue L: Mechanics.Translational Issue addresses Modelica.Mechanics.Translational
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MSL3.2.1

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Reported by beutlich on 29 Oct 2010 11:11 UTC
The partial models Modelica.Mechanics.Translational.Interfaces.PartialCompliant and Modelica.Mechanics.Translational.Interfaces.PartialCompliantWithRelativeStates have s_rel as component which is of type Modelica.SIunits.Distance which means that the minimum length is zero.

From the simulation point of view there is no actual need to restict the spring displacement of model Modelica.Mechanics.Translational.Components.Spring (which is derived from Modelica.Mechanics.Translational.Interfaces.PartialCompliant) to non-negative values (beside that real physical springs always have a positive dimension). Thus the relative displacement s_rel should instead be of type Modelica.SIunits.Position to allow negative spring displacements and hence to generalize the element usage.

Some example: It is common modeling practice that for instance the translational spring is connected to a model Modelica.Mechanics.MultiBody.Joints.Prismatic to implement a massless spring in MBS. Now the two displacement variables Modelica.Mechanics.Translational.Components.Spring.s_rel and Modelica.Mechanics.MultiBody.Joints.Prismatic.s are identified by the Modelica simulation tool. However, Modelica.Mechanics.MultiBody.Joints.Prismatic.s is of the type Modelica.SIunits.Position where no such length requirement is to be met.

Migrated-From: https://trac.modelica.org/Modelica/ticket/446
@modelica-trac-importer modelica-trac-importer added bug Critical/severe issue L: Mechanics.Translational Issue addresses Modelica.Mechanics.Translational labels Jan 14, 2017
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Comment by hubertus on 3 Dec 2010 22:50 UTC
Fixed in 07fdd0c for 3.1 maintenance branch

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Comment by hubertus on 3 Dec 2010 22:53 UTC
Fixed in bd9a17d for 3.2 maintenance branch

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Comment by hubertus on 3 Dec 2010 22:58 UTC
Fixed in 145462a for trunk, 3.3dev

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Comment by hubertus on 3 Dec 2010 22:59 UTC
Fixed in 3.1, 3.2, trunk, see previous comments for revisions

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Modified by dietmarw on 3 Dec 2010 23:57 UTC

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Comment by dietmarw on 8 Dec 2010 07:53 UTC
Also fixed (by Toni) in 1c80cd0, 7ee43e7 for 3.0 and 3.0.1 maintenance branch.

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@modelica-trac-importer modelica-trac-importer modified the milestone: MSL3.2.1 Jan 14, 2017
@beutlich beutlich mentioned this issue Jun 15, 2018
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bug Critical/severe issue L: Mechanics.Translational Issue addresses Modelica.Mechanics.Translational
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