{"action":"closed","issue":{"url":"https://api.github.com/repos/tbeu/Modelica/issues/446","repository_url":"https://api.github.com/repos/tbeu/Modelica","labels_url":"https://api.github.com/repos/tbeu/Modelica/issues/446/labels{/name}","comments_url":"https://api.github.com/repos/tbeu/Modelica/issues/446/comments","events_url":"https://api.github.com/repos/tbeu/Modelica/issues/446/events","html_url":"https://github.com/tbeu/Modelica/issues/446","id":196969015,"number":446,"title":"Negative displacements of translational springs should be permitted","user":{"login":"modelica-trac-importer","id":22202507,"avatar_url":"https://avatars.githubusercontent.com/u/22202507?v=3","gravatar_id":"","url":"https://api.github.com/users/modelica-trac-importer","html_url":"https://github.com/modelica-trac-importer","followers_url":"https://api.github.com/users/modelica-trac-importer/followers","following_url":"https://api.github.com/users/modelica-trac-importer/following{/other_user}","gists_url":"https://api.github.com/users/modelica-trac-importer/gists{/gist_id}","starred_url":"https://api.github.com/users/modelica-trac-importer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/modelica-trac-importer/subscriptions","organizations_url":"https://api.github.com/users/modelica-trac-importer/orgs","repos_url":"https://api.github.com/users/modelica-trac-importer/repos","events_url":"https://api.github.com/users/modelica-trac-importer/events{/privacy}","received_events_url":"https://api.github.com/users/modelica-trac-importer/received_events","type":"User","site_admin":false},"labels":[{"id":504692710,"url":"https://api.github.com/repos/tbeu/Modelica/labels/bug","name":"bug","color":"ee0701","default":true},{"id":504700530,"url":"https://api.github.com/repos/tbeu/Modelica/labels/Mechanics.Translational","name":"Mechanics.Translational","color":"0000aa","default":false}],"state":"closed","locked":false,"assignee":{"login":"beutlich","id":14896695,"avatar_url":"https://avatars.githubusercontent.com/u/14896695?v=3","gravatar_id":"","url":"https://api.github.com/users/beutlich","html_url":"https://github.com/beutlich","followers_url":"https://api.github.com/users/beutlich/followers","following_url":"https://api.github.com/users/beutlich/following{/other_user}","gists_url":"https://api.github.com/users/beutlich/gists{/gist_id}","starred_url":"https://api.github.com/users/beutlich/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/beutlich/subscriptions","organizations_url":"https://api.github.com/users/beutlich/orgs","repos_url":"https://api.github.com/users/beutlich/repos","events_url":"https://api.github.com/users/beutlich/events{/privacy}","received_events_url":"https://api.github.com/users/beutlich/received_events","type":"User","site_admin":false},"assignees":[{"login":"beutlich","id":14896695,"avatar_url":"https://avatars.githubusercontent.com/u/14896695?v=3","gravatar_id":"","url":"https://api.github.com/users/beutlich","html_url":"https://github.com/beutlich","followers_url":"https://api.github.com/users/beutlich/followers","following_url":"https://api.github.com/users/beutlich/following{/other_user}","gists_url":"https://api.github.com/users/beutlich/gists{/gist_id}","starred_url":"https://api.github.com/users/beutlich/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/beutlich/subscriptions","organizations_url":"https://api.github.com/users/beutlich/orgs","repos_url":"https://api.github.com/users/beutlich/repos","events_url":"https://api.github.com/users/beutlich/events{/privacy}","received_events_url":"https://api.github.com/users/beutlich/received_events","type":"User","site_admin":false}],"milestone":null,"comments":4,"created_at":"2016-12-21T16:03:10Z","updated_at":"2016-12-21T16:04:09Z","closed_at":"2016-12-21T16:04:09Z","body":"**Reported by beutlich&#64;iti&#46;de on 29 Oct 2010 11:11 UTC**\nThe 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.\n\nFrom 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.\n\nSome 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.\n\n----\n\nMigrated-From: https://trac.modelica.org/Modelica/ticket/446"}}
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