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Problems with multibody mechanical models (Version)
Problems with multibody mechanical models (Version)
I think this example used to work in earlier version of openmodelica (I use OpenModelica 1.9.1+dev (r18855) (Bootstrapping version)) on ubuntu 12.10. Could anyone help me to get this running again?
Hi, this is the error I get, when trying to simulate the "PointGravityWithPointMasses2" Example in Openmodelica:
Code:
/tmp/OpenModelica/OMEdit/Modelica.Mechanics.MultiBody.Examples.Elementary.PointGravityWithPointMasses2 -port=35254 -logFormat=xml -w -lv=LOG_STATS
stdout | warning | Failed to solve linear system of equations (no. 216) at time 0.000000, system is singular for U[7, 7].
LOG_LS | warning | linear system fails: Linear function (index 102, size 4) at t=0
| | | | | [1] der(referenceSystem.pointMass1.Q[1])
| | | | | [2] der(referenceSystem.pointMass1.Q[3])
| | | | | [3] der(referenceSystem.pointMass1.Q[2])
| | | | | [4] der(referenceSystem.pointMass1.Q[4])
stdout | warning | Error in initialization. Storing results and exiting.
Use -lv=LOG_INIT -w for more information.
Simulation process exited with code 255
and in the message browser:
Code:
[:0:0-0:0] Error: Failed to open simulation result /tmp/OpenModelica/OMEdit/Modelica.Mechanics.MultiBody.Examples.Elementary.PointGravityWithPointMasses2_res.mat: Too few rows in data_2 matrix
EDIT: I just tried it with the "RML version" version of omc and it doesn't work, too. Same error message
EDIT: And I also just found out that the error has nee reported to track from someone three months ago: https://trac.openmodelica.org/OpenModel … #comment:1
If this really is a bug it is rather serious I think, because multibody systems is a really important simulation domain in Openmodelica
Thank you
Re: Problems with multibody mechanical models (Version)
ok.. ... I did a little bit more research and found this in the openmodelica model:
Code:
PointMass pointMass1(r_0(start = {3,0,0}, each fixed = true), v_0(start = {0,0,-1}, each fixed = true));
PointMass pointMass2 annotation(Placement(transformation(extent = {{-60,-10},{-40,10}}, rotation = 0)));
PointMass pointMass3(r_0(start = {2,1,0}, each fixed = true), v_0(start = {0,0,-1}, each fixed = true)) ;with r_0(start = {3,0,0}, each fixed = true) defined int Pointmass1 AND Pointmass3 and each set fixed to true, that means we have an overdetermined system ....
if I just remove one of the "fixed=true" inits from the the openmodelica example, it works ... :
So the big question is: is this a bug from modelica or from openmodelica?
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