You can view and download this file on Github: ANCFslidingAndALEjointTest.py
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details: Test model for rigid bodies sliding on cables
#
# Author: Andreas Zwölfer, Johannes Gerstmayr
# Date: 2019-12-18
#
# 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.utilities import * #includes itemInterface and rigidBodyUtilities
import exudyn.graphics as graphics #only import if it does not conflict
useGraphics = True #without test
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#you can erase the following lines and all exudynTestGlobals related operations if this is not intended to be used as TestModel:
try: #only if called from test suite
from modelUnitTests import exudynTestGlobals #for globally storing test results
useGraphics = exudynTestGlobals.useGraphics
except:
class ExudynTestGlobals:
pass
exudynTestGlobals = ExudynTestGlobals()
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
SC = exu.SystemContainer()
mbs = SC.AddSystem()
##################################################################################################################################################################
def AddBodyWithSlidingJoints(mbs,xPositionOfFirstNodes=0,referencePositionOfBodyAlongCable=0,gravityFieldConstant=0):
a = 0.8*2 #y-dim/2 of Body
b = 0.02 #x-dim/2 of Body
massRigid = 5000 #moving mass
inertiaRigid = massRigid/12*(2*a)**2
#rigid body which slides:
graphicsRigid1 = GraphicsDataRectangle(-b,-a,b,a) #drawing of rigid body
yCOM = a #COM distance to attachment point on suspension rope; in vertical direction
nRigid = mbs.AddNode(Rigid2D(referenceCoordinates=[xPositionOfFirstNodes+referencePositionOfBodyAlongCable,-yCOM,0]));
oRigid = mbs.AddObject(RigidBody2D(physicsMass=massRigid, physicsInertia=inertiaRigid,nodeNumber=nRigid,visualization=VObjectRigidBody2D(graphicsData= [graphicsRigid1])))
markerRigidTop=mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[0.,yCOM,0.])) #support point
markerRigidTopAle = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[0.,yCOM-offset,0.])) #support point
if gravityFieldConstant:
mR2 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[ 0.,0.,0.])) #center of mass (for load)
mbs.AddLoad(Force(markerNumber=mR2, loadVector=[0,-massRigid*gravityFieldConstant,0]))
#find index of cable element associated with "referencePositionOfBodyAlongCable"
cummulativeLength=0
count=0
while referencePositionOfBodyAlongCable >= cummulativeLength:
cummulativeLength+=mbs.GetObjectParameter(cable2ObjectList[count],'physicsLength')
count+=1
count+=-1
#AleSlidingJoint:
oAleSlidingJoint=GenerateAleSlidingJoint(mbs,cable1ObjectList,markerRigidTopAle,AleNode=nALE,localMarkerIndexOfStartCable=count,AleSlidingOffset=referencePositionOfBodyAlongCable)[0]
#slidingJoint:
oSlidingJoint=GenerateSlidingJoint(mbs,cable2ObjectList,markerRigidTop,localMarkerIndexOfStartCable=count,slidingCoordinateStartPosition=referencePositionOfBodyAlongCable)[0]
return [oRigid,nRigid, oAleSlidingJoint, oSlidingJoint]
#Background:
rect = [-2,-2,4,2] #xmin,ymin,xmax,ymax
background0 = {'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
background1 = {'type':'Line', 'color':[0.1,0.1,0.8,1], 'data':[0,-1,0, 2,-1,0]} #background
oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0]))
L=100 #length of ropes
gravityFieldConstant=9.81
complianceFactBend = 1
complianceFactAxial = 1
nEl=6 #must be even number
vALE=0
offset=0.35 #distance between the two ropes
offsetCarrier=-0.515 #distance between suspension rope and slack carrier wheel
nGlobalGround = mbs.AddNode(NodePointGround(referenceCoordinates=[0,0,0]))
mGlobalGround = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber = nGlobalGround, coordinate=0))
fixANCFRotation = 0
#######################ROPE2 (Carrier rope)########################################################################################################################
cable2Template=Cable2D(physicsMassPerLength=10, physicsBendingStiffness=50000*complianceFactBend, physicsAxialStiffness=2e8*complianceFactAxial)
[cable2NodeList, cable2ObjectList, suspensionLoadList, cable2NodePositionList, dummy]=GenerateStraightLineANCFCable2D(mbs=mbs,
positionOfNode0=[0,0,0], positionOfNode1=[L,0,0], numberOfElements=nEl,
cableTemplate=cable2Template, massProportionalLoad=[0,-gravityFieldConstant,0],
fixedConstraintsNode0=[1,1,0,fixANCFRotation], fixedConstraintsNode1=[1,1,0,fixANCFRotation])
##################################################################################################################################################################
######################ROPE1#######################################################################################################################################
nALE = mbs.AddNode(NodeGenericODE2(numberOfODE2Coordinates=1, referenceCoordinates=[0], initialCoordinates=[0], initialCoordinates_t=[vALE]))
mALE = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber = nALE, coordinate=0)) #ALE velocity marker
cable1Template=ALECable2D(physicsMassPerLength=3, physicsBendingStiffness=4000*complianceFactBend,
physicsAxialStiffness=5e7*complianceFactAxial,physicsUseCouplingTerms=False,
physicsAddALEvariation=False) #for compatibility with test suite results
cable1Template.nodeNumbers[2]=nALE
[cable1NodeList, cable1ObjectList, haulageLoadList, cable1NodePositionList, dummy]=GenerateStraightLineANCFCable2D(mbs=mbs,
positionOfNode0=[0,-offset,0], positionOfNode1=[L,-offset,0], numberOfElements=nEl,
cableTemplate=cable1Template, massProportionalLoad=[0,-gravityFieldConstant,0],
fixedConstraintsNode0=[1,1,0,fixANCFRotation], fixedConstraintsNode1=[1,1,0,fixANCFRotation])
cAleConstraint=mbs.AddObject(CoordinateConstraint(markerNumbers=[mGlobalGround,mALE]))
###################################################################################################################################################################
#Slack carrier:
carrierWheelRadius=0.42/2
mSuspensionRopeAttachmentNodeX=mbs.AddMarker(MarkerNodeCoordinate(nodeNumber = cable2NodeList[int(nEl/2)], coordinate=0))
mSuspensionRopeAttachmentNodeY=mbs.AddMarker(MarkerNodeCoordinate(nodeNumber = cable2NodeList[int(nEl/2)], coordinate=1))
graphicsCarrier={'type':'Circle', 'color':[.1,0.1,0.8,1], 'position':[0,0,0], 'radius': carrierWheelRadius}
nCarrierRigidBody = mbs.AddNode(Rigid2D(referenceCoordinates=[L/2,offsetCarrier-carrierWheelRadius,0]))
oCarrierRigidBody = mbs.AddObject(RigidBody2D(physicsMass=200, physicsInertia=1,
nodeNumber=nCarrierRigidBody,visualization=VObjectRigidBody2D(graphicsData= [graphicsCarrier])))
mCarrierX = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nCarrierRigidBody,coordinate=0))
mCarrierY = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nCarrierRigidBody,coordinate=1))
mCarrierRot = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nCarrierRigidBody,coordinate=2))
mbs.AddObject(CoordinateConstraint(markerNumbers=[mSuspensionRopeAttachmentNodeX,mCarrierX]))
mbs.AddObject(CoordinateConstraint(markerNumbers=[mSuspensionRopeAttachmentNodeY,mCarrierY]))
mbs.AddObject(CoordinateConstraint(markerNumbers=[mGlobalGround,mCarrierRot]))
#mCarrierWheelLoad = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oCarrierRigidBody, localPosition=[ 0.,0.,0.])) #center of mass (for load)
#mbs.AddLoad(Force(markerNumber=mConnectionWheelLoad, loadVector=[0,-CarrierMass*gravityFieldConstant,0]))
nSegments = 4 #number of contact segments; must be consistent between nodedata and contact element
useFriction = True
nFactFriction = 1
if useFriction: nFactFriction = 3
initialGapList = [0.1]*(nSegments*nFactFriction) #initial gap of 0.1
cStiffness = 1e7
mContactCarrier=mbs.AddMarker(MarkerBodyRigid(bodyNumber = oCarrierRigidBody))
for i in cable1ObjectList:
mContactCable = mbs.AddMarker(MarkerBodyCable2DShape(bodyNumber=i, numberOfSegments = nSegments))
nodeDataContactCable = mbs.AddNode(NodeGenericData(initialCoordinates=initialGapList,numberOfDataCoordinates=nSegments*nFactFriction))
if useFriction:
mbs.AddObject(ObjectContactFrictionCircleCable2D(markerNumbers=[mContactCarrier, mContactCable],
nodeNumber = nodeDataContactCable, numberOfContactSegments=nSegments,
contactStiffness = cStiffness, circleRadius = carrierWheelRadius))
else:
mbs.AddObject(ObjectContactCircleCable2D(markerNumbers=[mContactCarrier, mContactCable],
nodeNumber = nodeDataContactCable, numberOfContactSegments=nSegments,
contactStiffness = cStiffness, circleRadius = carrierWheelRadius, offset = 0))
#Add Bodys
cRigidBodyRotList=[]
cRigidBodyTranslationXlist=[]
cRigidBodyTranslationYlist=[]
distanceBetweenBodys=32
numberOfBodys=2
positionOfBody=0
for i in range(numberOfBodys):
#Add Body
[oRigid,nRigid,oAleSlidingJoint,oSlidingJoint]=AddBodyWithSlidingJoints(mbs,xPositionOfFirstNodes=0,referencePositionOfBodyAlongCable=positionOfBody,gravityFieldConstant=gravityFieldConstant)
mbs.SetObjectParameter(oSlidingJoint, 'classicalFormulation', False) #test model computed with new sliding joint formulation
#fix rotation of rigid body
mRigidBodyRot = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber = nRigid, coordinate=2)) #add rigid body marker
cRigidBodyRot = mbs.AddObject(CoordinateConstraint(markerNumbers=[mGlobalGround,mRigidBodyRot]))
cRigidBodyRotList+=[cRigidBodyRot]
#add damper for rotation of rigid body
mbs.AddObject(CoordinateSpringDamper(markerNumbers=[mGlobalGround,mRigidBodyRot],damping = 1e6, visualization=VObjectConnectorCoordinateSpringDamper(show=False)))
positionOfBody+=distanceBetweenBodys
#++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
# Assemble multibody system
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
mbs.Assemble()
#exu.Print(mbs)
#++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
# Simualtion settings:
#++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
simulationSettings = exu.SimulationSettings()
#simulationSettings.staticSolver.loadStepGeometric = True
#simulationSettings.staticSolver.adaptiveStep = False
simulationSettings.staticSolver.numberOfLoadSteps=10
#simulationSettings.staticSolver.loadStepGeometricRange = 100
simulationSettings.staticSolver.newton.relativeTolerance = 1e-7 #with this error tolerance, the adaptive step selection needs 4 steps
#simulationSettings.staticSolver.verboseMode=1
#simulationSettings.staticSolver.verboseModeFile=2
simulationSettings.staticSolver.stabilizerODE2term = 2
SC.visualizationSettings.general.circleTiling = 64
SC.visualizationSettings.nodes.defaultSize=0.125
SC.visualizationSettings.contour.outputVariable = exu.OutputVariableType.Displacement
SC.visualizationSettings.contour.outputVariableComponent = 1 # plot y-component
SC.visualizationSettings.contact.contactPointsDefaultSize = .005
SC.visualizationSettings.connectors.showContact = True
if useGraphics:
exu.StartRenderer()
#get initial velocities
vInit = mbs.systemData.GetODE2Coordinates_t(configuration = exu.ConfigurationType.Initial)
#start static calculation
mbs.SolveStatic(simulationSettings)
#++++++++++++++++++++++++++++++++++++++++
#compute error for test suite:
ltgCable = mbs.systemData.GetObjectLTGODE2(cable1ObjectList[int(len(cable1ObjectList)/2)])
nc = ltgCable[1] #vertical displacement
exu.Print("select cable coordinate", nc)
sol = mbs.systemData.GetODE2Coordinates();
uStatic = sol[nc]; #y-displacement of first node of four bar mechanism
exu.Print('static solution of cable1 =',uStatic)
exudynTestGlobals.testError = uStatic - (-2.1973218891272532) #before 2023-05-01 (new loads jacobian): -2.1973218869310713 #before 2022-03-09 (old ObjectContactFrictionCircleCable2D): -2.197321886974786 2020-03-05(corrected Cable2DshapeMarker): -2.197321886974786 #2019-12-26: 2.1973218859908146
exudynTestGlobals.testResult = uStatic
#++++++++++++++++++++++++++++++++++++++++
#store solution for next computation
u = mbs.systemData.GetODE2Coordinates()
data = mbs.systemData.GetDataCoordinates()
#Add drive via ALE:
def userLoadDriveAle(mbs, t, load):
#if t < 1:
return t*50000*5
#else: return 0
mbs.AddLoad(LoadCoordinate(markerNumber = mALE, loadUserFunction=userLoadDriveAle))
mbs.Assemble() #because of new load
#++++++++++++++++++++++++++++++++++++++++
#resuse old solution
mbs.systemData.SetODE2Coordinates(u,configuration = exu.ConfigurationType.Initial)
mbs.systemData.SetODE2Coordinates_t(vInit,configuration = exu.ConfigurationType.Initial)
mbs.systemData.SetDataCoordinates(data,configuration = exu.ConfigurationType.Initial)
# remove rigid body motion constraints for dynamic analysis
for item in cRigidBodyRotList:
mbs.SetObjectParameter(item, 'activeConnector', False)
mbs.SetObjectParameter(cAleConstraint, 'activeConnector', False)
solveDynamic = True
if solveDynamic:
# time related settings:
steps=400
tend=0.8
h=tend/steps
SC.visualizationSettings.openGL.lineWidth = 2
simulationSettings.timeIntegration.numberOfSteps = steps
simulationSettings.timeIntegration.endTime = tend
simulationSettings.timeIntegration.generalizedAlpha.useIndex2Constraints = True
simulationSettings.timeIntegration.generalizedAlpha.useNewmark = simulationSettings.timeIntegration.generalizedAlpha.useIndex2Constraints
simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 0.3
simulationSettings.timeIntegration.verboseMode = 1
simulationSettings.displayStatistics = True
mbs.SolveDynamic(simulationSettings)
if useGraphics:
#SC.WaitForRenderEngineStopFlag()
exu.StopRenderer() #safely close rendering window!
sol = mbs.systemData.GetODE2Coordinates();
uDynamic = sol[nc]; #y-displacement of first node of four bar mechanism
exu.Print('dynamic solution of cable1 =',uDynamic)
exudynTestGlobals.testError += uDynamic - (-2.2290865056280076) #before 2023-05-01 (loads jacobian): -2.229086503625397 #before 2022-12-25(resolved BUG 1274): -2.229081157258582; before 2022-03-09 (old ObjectContactFrictionCircleCable2D) : (-2.2290811574753953) #2020-03-05(corrected Cable2DshapeMarker): -2.2290811574753953 #2019-12-26: -2.2290811558815617; 2019-12-18: -2.229126333291627
exudynTestGlobals.testResult += uDynamic
exu.Print('result of ANCFslidingAndALEjointTest=',exudynTestGlobals.testResult)