switchingConstraintsPendulum.py
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1#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2# This is an EXUDYN example
3#
4# Details: Rigid pendulum with tip mass
5# The functionality mbs.SetPreStepUserFunction is used to deactivate a constraint after a given time
6# Shows how to load solution to animate an existing solution
7#
8# Author: Johannes Gerstmayr
9# Date: 2019-11-22
10#
11# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
12#
13#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
14
15import exudyn as exu
16from exudyn.itemInterface import *
17from exudyn.utilities import *
18
19SC = exu.SystemContainer()
20mbs = SC.AddSystem()
21
22#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
23#rigid pendulum with initial velocities
24#constraints and joints are deactivated during simulation
25
26rect = [-2.5,-1.5,0.5,1.5] #xmin,ymin,xmax,ymax
27background = {'type':'Line', 'color':[0.1,0.1,0.8,1], 'data':[rect[0],rect[1],0, rect[2],rect[1],0, rect[2],rect[3],0, rect[0],rect[3],0, rect[0],rect[1],0]} #background
28oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0], visualization=VObjectGround(graphicsData= [background])))
29#nGround=mbs.AddNode(NodePointGround(referencePosition= [0,0,0]))
30a = 0.5 #x-dim of pendulum
31b = 0.05 #y-dim of pendulum
32massRigid = 12
33mass = 2 #of additional mass
34inertiaRigid = massRigid/12*(2*a)**2
35
36omega0 = 4
37
38graphics2 = {'type':'Line', 'color':[0.1,0.1,0.8,1], 'data':[-a,-b,0, a,-b,0, a,b,0, -a,b,0, -a,-b,0]} #background
39nRigid = mbs.AddNode(Rigid2D(referenceCoordinates=[-0.5,0,0], initialVelocities=[0,omega0*a,omega0]));
40oRigid = mbs.AddObject(RigidBody2D(physicsMass=massRigid, physicsInertia=inertiaRigid,nodeNumber=nRigid,visualization=VObjectRigidBody2D(graphicsData= [graphics2])))
41
42mR1 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[-0.5,0.,0.])) #support point
43mG0 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oGround, localPosition=[-0.5-a,0.,0.]))
44oRJoint = mbs.AddObject(RevoluteJoint2D(markerNumbers=[mG0,mR1],activeConnector=True))
45
46#mass point is attached with coordinate constraints:
47mCoordR0 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nRigid, coordinate=0))
48mCoordR1 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nRigid, coordinate=1))
49
50#additional mass point attached to COM of rigid body:
51nMass = mbs.AddNode(Point2D(referenceCoordinates=[-0.5,0], initialVelocities=[0,omega0*a]));
52oMass = mbs.AddObject(MassPoint2D(physicsMass=mass, nodeNumber=nMass) )
53
54mCoordM0 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nMass, coordinate=0))
55mCoordM1 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nMass, coordinate=1))
56
57oConstraint0 = mbs.AddObject(CoordinateConstraint(markerNumbers=[mCoordM0, mCoordR0],activeConnector=True))
58oConstraint1 = mbs.AddObject(CoordinateConstraint(markerNumbers=[mCoordM1, mCoordR1],activeConnector=True))
59
60mbs.Assemble()
61
62simulationSettings = exu.SimulationSettings() #takes currently set values or default values
63simulationSettings.timeIntegration.numberOfSteps = 4000
64simulationSettings.timeIntegration.endTime = 2
65simulationSettings.timeIntegration.newton.relativeTolerance = 1e-8
66simulationSettings.timeIntegration.newton.absoluteTolerance = 1e-6
67simulationSettings.timeIntegration.verboseMode = 1
68
69def UFswitchConnector(mbs, t):
70 if t > 0.3:
71 mbs.SetObjectParameter(oRJoint, 'activeConnector', False)
72 if t > 0.1:
73 mbs.SetObjectParameter(oConstraint0, 'activeConnector', False)
74 mbs.SetObjectParameter(oConstraint1, 'activeConnector', False)
75 return True #True, means that everything is alright, False=stop simulation
76
77mbs.SetPreStepUserFunction(UFswitchConnector)
78
79simulationSettings.timeIntegration.newton.useModifiedNewton = False
80simulationSettings.timeIntegration.newton.numericalDifferentiation.minimumCoordinateSize = 1
81simulationSettings.timeIntegration.generalizedAlpha.useNewmark = True
82simulationSettings.timeIntegration.generalizedAlpha.useIndex2Constraints = True
83simulationSettings.solutionSettings.solutionInformation = "Rigid pendulum with switching constraints"
84simulationSettings.displayStatistics = True
85
86SC.visualizationSettings.openGL.multiSampling = 1
87
88exu.StartRenderer()
89
90mbs.SolveDynamic(simulationSettings)
91print('end time =',mbs.systemData.GetTime()) #time after time integration ...
92#print('solution =',mbs.systemData.GetODE2Coordinates()) #solution coordinates after time integration ...
93
94mbs.WaitForUserToContinue()
95
96animate = True
97if animate:
98 fileName = 'coordinatesSolution.txt'
99 solution = LoadSolutionFile('coordinatesSolution.txt')
100 AnimateSolution(mbs, solution, 1, 0.05)
101
102
103#SC.WaitForRenderEngineStopFlag()
104exu.StopRenderer() #safely close rendering window!