.. _examples-3springsdistance:

*******************
3SpringsDistance.py
*******************

You can view and download this file on Github: `3SpringsDistance.py <https://github.com/jgerstmayr/EXUDYN/tree/master/main/pythonDev/Examples/3SpringsDistance.py>`_

.. code-block:: python
   :linenos:

   #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   # This is an EXUDYN example
   #
   # Details:  File to test ConnectorDistance and ConnectorSpringDamper with point mass
   #           NOTE: this is a very old example, still using dictionaries! check other examples, which use itemInterface!
   #
   # Author:   Johannes Gerstmayr
   # Date:     2019-07-15
   #
   # 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.
   #
   # Remark: check, why generalized alpha does work so badly for this example
   #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   
   import exudyn as exu
   
   SC = exu.SystemContainer()
   mbs = SC.AddSystem()
   
   nBodies = 4
   
   L = 0.1 #distance
   L2 = 1.414213562373095*L
   
   #add nodes:
   #n0=mbs.AddNode({'nodeType': 'Point','referenceCoordinates': [0,0,0]})
   #n1=mbs.AddNode({'nodeType': 'Point','referenceCoordinates': [L,L,0]})
   #n2=mbs.AddNode({'nodeType': 'Point','referenceCoordinates': [0,L,L]})
   n3=mbs.AddNode({'nodeType': 'Point','referenceCoordinates': [0,L,0]})
   
   #node2=mbs.GetNode(n3)
   #print(node2)
   
   graphics1 = {'type':'Line', 'color':[0.1,0.1,0.8,1], 'data':[-2*L,-2*L,0, 2*L,-2*L,0, 2*L,2*L,0, -2*L,2*L,0, -2*L,-2*L, 0]}
   
   #add mass points and ground object:
   mbs.AddObject({'objectType': 'Ground', 'referencePosition': [0,0,0], 'graphicsData': [graphics1]})
   mbs.AddObject({'objectType': 'Ground', 'referencePosition': [L,L,0]})
   mbs.AddObject({'objectType': 'Ground', 'referencePosition': [0,L,L]})
   mbs.AddObject({'objectType': 'MassPoint', 'physicsMass': 2.5, 'nodeNumber': n3}) #, 'graphicsData': [graphics1]})
   
   #add markers (needed for connectors and loads):
   for i in range(nBodies): mbs.AddMarker({'markerType': 'BodyPosition',  'bodyNumber': i,  'localPosition': [0.0, 0.0, 0.0], 'bodyFixed': False})
   
   k = 4000 #spring stiffness
   d = 200*0.1  #damping coefficient
   
   useConstraint = True
   if useConstraint:
       mbs.AddObject({'objectType': 'ConnectorDistance', 
                      'distance': L, 
                      'markerNumbers': [0,3], 
                      'drawSize': 0.01,
                      'color': [1,0,0,1]})
   else:
       mbs.AddObject({'objectType': 'ConnectorSpringDamper', 
                      'stiffness': k, 
                      'damping': d, 
                      'force': 0, 
                      'referenceLength':L, 
                      'markerNumbers': [0,3], 
                      'drawSize': 0.01})
   mbs.AddObject({'objectType': 'ConnectorSpringDamper', 
                  'stiffness': k, 
                  'damping': d, 
                  'force': 0, 
                  'referenceLength':L, 
                  'markerNumbers': [1,3], 
                  'drawSize': 0.01})
   mbs.AddObject({'objectType': 'ConnectorSpringDamper', 
                  'stiffness': k, 
                  'damping': d, 
                  'force': 0, 
                  'referenceLength':L, 
                  'markerNumbers': [2,3], 
                  'drawSize': 0.01})
   
   #add loads:
   #mbs.AddLoad({'loadType': 'ForceVector',  'markerNumber': nBodies-1,  'loadVector': [0, 20, 0]}) #gives 20N tension in Distance constraint
   mbs.AddLoad({'loadType': 'ForceVector',  'markerNumber': nBodies-1,  'loadVector': [10, 0, 0]}) #gives approx. 0.001 deformation in x-direction
   
   print(mbs)
   
   mbs.Assemble()
   exu.StartRenderer()
   
   simulationSettings = exu.SimulationSettings()
   
   SC.visualizationSettings.nodes.showNumbers = True
   SC.visualizationSettings.bodies.showNumbers = True
   SC.visualizationSettings.connectors.showNumbers = True
   SC.visualizationSettings.nodes.defaultSize = 0.05
   
   
   computeDynamic = True
   if computeDynamic:
       simulationSettings.timeIntegration.numberOfSteps = 100000000
       simulationSettings.timeIntegration.endTime = 500000
       simulationSettings.solutionSettings.writeSolutionToFile = True
       simulationSettings.solutionSettings.solutionWritePeriod = simulationSettings.timeIntegration.endTime/2000
       simulationSettings.displayComputationTime = True
       simulationSettings.timeIntegration.verboseMode = 1
   
       simulationSettings.timeIntegration.newton.relativeTolerance = 1e-8
       simulationSettings.timeIntegration.newton.absoluteTolerance = 1e-2
       simulationSettings.timeIntegration.newton.useModifiedNewton = True
       simulationSettings.timeIntegration.generalizedAlpha.useNewmark = True #example only works with Newmark
       simulationSettings.timeIntegration.generalizedAlpha.useIndex2Constraints = True
       simulationSettings.displayStatistics = True
   
       mbs.SolveDynamic(simulationSettings)
   
   else:
       simulationSettings.solutionSettings.coordinatesSolutionFileName = "staticSolution.txt"
       simulationSettings.solutionSettings.appendToFile = False
       simulationSettings.staticSolver.newton.numericalDifferentiation.relativeEpsilon = 1e-4
       #simulationSettings.staticSolver.newton.relativeTolerance = 1e-6
       simulationSettings.staticSolver.newton.absoluteTolerance = 1e-1
       simulationSettings.staticSolver.verboseMode = 2
   
       mbs.SolveStatic(simulationSettings)
   
   SC.WaitForRenderEngineStopFlag()
   exu.StopRenderer() #safely close rendering window!