.. _examples-switchingconstraintspendulum:

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switchingConstraintsPendulum.py
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You can view and download this file on Github: `switchingConstraintsPendulum.py <https://github.com/jgerstmayr/EXUDYN/tree/master/main/pythonDev/Examples/switchingConstraintsPendulum.py>`_

.. code-block:: python
   :linenos:

   #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   # This is an EXUDYN example
   #
   # Details:  Rigid pendulum with tip mass
   #           The functionality mbs.SetPreStepUserFunction is used to deactivate a constraint after a given time
   #           Shows how to load solution to animate an existing solution
   #
   # Author:   Johannes Gerstmayr
   # Date:     2019-11-22
   #
   # 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.
   #
   #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   
   import exudyn as exu
   from exudyn.itemInterface import *
   from exudyn.utilities import * #includes itemInterface and rigidBodyUtilities
   import exudyn.graphics as graphics #only import if it does not conflict
   
   SC = exu.SystemContainer()
   mbs = SC.AddSystem()
   
   #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   #rigid pendulum with initial velocities
   #constraints and joints are deactivated during simulation
   
   rect = [-2.5,-1.5,0.5,1.5] #xmin,ymin,xmax,ymax
   background = {'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
   oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0], visualization=VObjectGround(graphicsData= [background])))
   #nGround=mbs.AddNode(NodePointGround(referencePosition= [0,0,0]))
   a = 0.5     #x-dim of pendulum
   b = 0.05    #y-dim of pendulum
   massRigid = 12
   mass = 2 #of additional mass
   inertiaRigid = massRigid/12*(2*a)**2
   
   omega0 = 4
   
   graphics2 = {'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
   nRigid = mbs.AddNode(Rigid2D(referenceCoordinates=[-0.5,0,0], initialVelocities=[0,omega0*a,omega0]));
   oRigid = mbs.AddObject(RigidBody2D(physicsMass=massRigid, physicsInertia=inertiaRigid,nodeNumber=nRigid,visualization=VObjectRigidBody2D(graphicsData= [graphics2])))
   
   mR1 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[-0.5,0.,0.])) #support point
   mG0 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oGround, localPosition=[-0.5-a,0.,0.]))
   oRJoint = mbs.AddObject(RevoluteJoint2D(markerNumbers=[mG0,mR1],activeConnector=True))
   
   #mass point is attached with coordinate constraints:
   mCoordR0 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nRigid, coordinate=0)) 
   mCoordR1 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nRigid, coordinate=1)) 
   
   #additional mass point attached to COM of rigid body:
   nMass = mbs.AddNode(Point2D(referenceCoordinates=[-0.5,0], initialVelocities=[0,omega0*a]));
   oMass = mbs.AddObject(MassPoint2D(physicsMass=mass, nodeNumber=nMass) )
   
   mCoordM0 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nMass, coordinate=0)) 
   mCoordM1 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nMass, coordinate=1)) 
   
   oConstraint0 = mbs.AddObject(CoordinateConstraint(markerNumbers=[mCoordM0, mCoordR0],activeConnector=True))
   oConstraint1 = mbs.AddObject(CoordinateConstraint(markerNumbers=[mCoordM1, mCoordR1],activeConnector=True))
   
   mbs.Assemble()
   
   simulationSettings = exu.SimulationSettings() #takes currently set values or default values
   simulationSettings.timeIntegration.numberOfSteps = 4000
   simulationSettings.timeIntegration.endTime = 2
   simulationSettings.timeIntegration.newton.relativeTolerance = 1e-8
   simulationSettings.timeIntegration.newton.absoluteTolerance = 1e-6
   simulationSettings.timeIntegration.verboseMode = 1
   
   def UFswitchConnector(mbs, t):
       if t > 0.3: 
           mbs.SetObjectParameter(oRJoint, 'activeConnector', False)
       if t > 0.1: 
           mbs.SetObjectParameter(oConstraint0, 'activeConnector', False)
           mbs.SetObjectParameter(oConstraint1, 'activeConnector', False)
       return True #True, means that everything is alright, False=stop simulation
   
   mbs.SetPreStepUserFunction(UFswitchConnector)
   
   simulationSettings.timeIntegration.newton.useModifiedNewton = False
   simulationSettings.timeIntegration.newton.numericalDifferentiation.minimumCoordinateSize = 1
   simulationSettings.timeIntegration.generalizedAlpha.useNewmark = True
   simulationSettings.timeIntegration.generalizedAlpha.useIndex2Constraints = True
   simulationSettings.solutionSettings.solutionInformation = "Rigid pendulum with switching constraints"
   simulationSettings.displayStatistics = True
   
   SC.visualizationSettings.openGL.multiSampling = 1
   
   SC.renderer.Start()
   
   mbs.SolveDynamic(simulationSettings)
   print('end time =',mbs.systemData.GetTime()) #time after time integration ...
   #print('solution =',mbs.systemData.GetODE2Coordinates()) #solution coordinates after time integration ...
   
   
   SC.renderer.DoIdleTasks()
   SC.renderer.Stop() #safely close rendering window!
   
   mbs.SolutionViewer()