kinematicTreeConstraintTest.py

You can view and download this file on Github: kinematicTreeConstraintTest.py

  1#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  2# This is an EXUDYN python utility library
  3#
  4# Details:  test of MarkerKinematicTreeRigid in combination with loads and joint
  5#
  6# Author:   Johannes Gerstmayr
  7# Date:     2022-05-29
  8#
  9# 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.
 10#
 11#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 12
 13import exudyn as exu
 14from exudyn.utilities import *
 15from exudyn.FEM import *
 16
 17import numpy as np
 18
 19useGraphics = True
 20#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 21#you can erase the following lines and all exudynTestGlobals related operations if this is not intended to be used as TestModel:
 22try: #only if called from test suite
 23    from modelUnitTests import exudynTestGlobals #for globally storing test results
 24    useGraphics = exudynTestGlobals.useGraphics
 25except:
 26    class ExudynTestGlobals:
 27        pass
 28    exudynTestGlobals = ExudynTestGlobals()
 29#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 30
 31from math import pi, sin, cos#, sqrt
 32from copy import copy, deepcopy
 33from exudyn.rigidBodyUtilities import Skew, Skew2Vec
 34from exudyn.robotics import *
 35
 36SC = exu.SystemContainer()
 37mbs = SC.AddSystem()
 38
 39# useGraphics = False
 40
 41useMBS = True
 42useKinematicTree = True
 43addForce = True #add gravity as body / link forces
 44addConstraint = True #add constraint at tip of chain
 45
 46
 47gGround =  GraphicsDataCheckerBoard(point= [0,0,-2], size = 12)
 48objectGround = mbs.AddObject(ObjectGround(referencePosition = [0,0,0],
 49                                          visualization=VObjectGround(graphicsData=[gGround])))
 50baseMarker = mbs.AddMarker(MarkerBodyRigid(bodyNumber=objectGround, localPosition=[0,0,0]))
 51
 52L = 0.5 #length
 53w = 0.1 #width of links
 54pControl = 20000 #we keep the motion of the prismatic joint fixed
 55dControl = pControl*0.02
 56
 57gravity3D = [0,-9.81*0,0]
 58graphicsBaseList = [GraphicsDataOrthoCubePoint(size=[L*4, 0.8*w, 0.8*w], color=color4grey)] #rail
 59
 60newRobot = Robot(gravity=gravity3D,
 61              base = RobotBase(visualization=VRobotBase(graphicsData=graphicsBaseList)),
 62              tool = RobotTool(HT=HTtranslate([0,0.5*L,0]), visualization=VRobotTool(graphicsData=[
 63                  GraphicsDataOrthoCubePoint(size=[w, L, w], color=color4orange)])),
 64              referenceConfiguration = []) #referenceConfiguration created with 0s automatically
 65
 66#cart:
 67Jlink = InertiaCuboid(density=5000, sideLengths=[L,w,w]) #w.r.t. reference center of mass
 68link = RobotLink(Jlink.Mass(), Jlink.COM(), Jlink.InertiaCOM(),
 69                 jointType='Px', preHT=HT0(),
 70                 PDcontrol=(pControl, dControl),
 71                 visualization=VRobotLink(linkColor=color4lawngreen))
 72newRobot.AddLink(link)
 73linksList = [copy(link)]
 74
 75nChainLinks = 4 #5
 76for i in range(nChainLinks):
 77    Jlink = InertiaCuboid(density=1000, sideLengths=[w,L,w]) #w.r.t. reference center of mass
 78    Jlink = Jlink.Translated([0,0.5*L,0])
 79    preHT = HT0()
 80    if i > 0:
 81        preHT = HTtranslateY(L)
 82
 83    link = RobotLink(Jlink.Mass(), Jlink.COM(), Jlink.InertiaCOM(),
 84                     jointType='Rz', preHT=preHT,
 85                     PDcontrol=(pControl*0, dControl*0),
 86                     visualization=VRobotLink(linkColor=color4blue))
 87    newRobot.AddLink(link)
 88    linksList += [copy(link)]
 89
 90newRobot.referenceConfiguration[0] = 0.5*0
 91# for i in range(nChainLinks):
 92#     newRobot.referenceConfiguration[i+1] = (2*pi/360) * 5
 93newRobot.referenceConfiguration[1] = -(2*pi/360) * 90 #-0.5*pi
 94# newRobot.referenceConfiguration[2] = (2*pi/360) * 12 #-0.5*pi
 95
 96# locPos = [0.1,0.2,0.3]
 97locPos = [0,0,0]
 98nLinks = newRobot.NumberOfLinks()
 99
100sMBS = []
101if useMBS:
102    #newRobot.gravity=[0,-9.81,0]
103    robDict = newRobot.CreateRedundantCoordinateMBS(mbs=mbs, baseMarker=baseMarker, createJointTorqueLoads=False)
104    bodies = robDict['bodyList']
105
106    sMBS+=[mbs.AddSensor(SensorBody(bodyNumber=bodies[nLinks-1], localPosition=locPos, storeInternal=True,
107                                    outputVariableType=exu.OutputVariableType.Position))]
108
109    if addForce:
110        for i in range(len(bodies)):
111            mBody = mbs.AddMarker(MarkerBodyRigid(bodyNumber=bodies[i], localPosition=linksList[i].COM))
112            mbs.AddLoad(Force(markerNumber=mBody, loadVector=[0,-9.81*linksList[i].mass, 0]))
113
114    if addConstraint:
115        mTip = mbs.AddMarker(MarkerBodyRigid(bodyNumber=bodies[-1], localPosition=[0,L,0]))
116        mTipGround = mbs.AddMarker(MarkerBodyRigid(bodyNumber=objectGround, localPosition=[L*nChainLinks,0,0]))
117        mbs.AddObject(SphericalJoint(markerNumbers=[mTip, mTipGround], constrainedAxes=[0,1,0]))
118
119sKT = []
120if useKinematicTree:
121    #newRobot.gravity=[0,-9.81,0]
122    dKT = newRobot.CreateKinematicTree(mbs)
123    oKT = dKT['objectKinematicTree']
124
125    sKT+=[mbs.AddSensor(SensorKinematicTree(objectNumber=oKT, linkNumber=nLinks-1, localPosition=locPos, storeInternal=True,
126                                            outputVariableType=exu.OutputVariableType.Position))]
127
128    if addForce:
129        for i in range(nLinks):
130            mLink = mbs.AddMarker(MarkerKinematicTreeRigid(objectNumber=oKT, linkNumber=i, localPosition=linksList[i].COM))
131            mbs.AddLoad(Force(markerNumber=mLink, loadVector=[0,-9.81*linksList[i].mass, 0]))
132
133    if addConstraint:
134        mTip = mbs.AddMarker(MarkerKinematicTreeRigid(objectNumber=oKT, linkNumber=nLinks-1, localPosition=[0,L,0]))
135        mTipGround = mbs.AddMarker(MarkerBodyRigid(bodyNumber = objectGround, localPosition=[L*nChainLinks,0,0]))
136        mbs.AddObject(SphericalJoint(markerNumbers=[mTip, mTipGround], constrainedAxes=[0,1,0]))
137
138#exu.Print(mbs)
139mbs.Assemble()
140
141simulationSettings = exu.SimulationSettings()
142
143tEnd = 0.5
144h = 4*1e-3
145#tEnd = h
146
147simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
148simulationSettings.timeIntegration.endTime = tEnd
149# simulationSettings.timeIntegration.numberOfSteps = 1#int(tEnd/h)
150# simulationSettings.timeIntegration.endTime = h*1#tEnd
151simulationSettings.solutionSettings.solutionWritePeriod = 0.01*100
152simulationSettings.solutionSettings.sensorsWritePeriod = 0.001*20
153simulationSettings.timeIntegration.verboseMode = 1
154#simulationSettings.solutionSettings.solutionWritePeriod = tEnd/steps
155simulationSettings.timeIntegration.newton.useModifiedNewton=True
156
157# simulationSettings.displayComputationTime = True
158# simulationSettings.linearSolverType=exu.LinearSolverType.EigenSparse
159
160simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 0.95 #SHOULD work with 0.9 as well
161
162SC.visualizationSettings.general.autoFitScene=False
163SC.visualizationSettings.window.renderWindowSize = [1600,1200]
164SC.visualizationSettings.general.drawCoordinateSystem=True
165SC.visualizationSettings.general.drawWorldBasis=True
166SC.visualizationSettings.openGL.multiSampling=4
167SC.visualizationSettings.nodes.showBasis = True
168SC.visualizationSettings.nodes.basisSize = 0.5
169if useGraphics:
170
171    exu.StartRenderer()
172    if 'renderState' in exu.sys: SC.SetRenderState(exu.sys['renderState']) #load last model view
173
174    mbs.WaitForUserToContinue() #press space to continue
175
176# mbs.SolveDynamic(simulationSettings, solverType = exu.DynamicSolverType.ExplicitMidpoint)
177mbs.SolveDynamic(simulationSettings)
178
179if not useGraphics or True:
180    #check results for test suite:
181    u = 0.
182    for i in range(len(sMBS)):
183        v = mbs.GetSensorValues(sMBS[i])
184        exu.Print('sensor MBS '+str(i)+'=',v)
185        u += np.linalg.norm(v)
186        v = mbs.GetSensorValues(sKT[i])
187        exu.Print('sensor KT '+str(i)+' =',v)
188        u += np.linalg.norm(v)
189
190exu.Print("solution of kinematicTreeConstraintTest=", u)
191exudynTestGlobals.testResult = u #1.8135975385993548
192
193
194if False and useGraphics: #use this to reload the solution and use SolutionViewer
195    #sol = LoadSolutionFile('coordinatesSolution.txt')
196
197    mbs.SolutionViewer() #can also be entered in IPython ...
198
199if useGraphics:
200    SC.WaitForRenderEngineStopFlag()
201    exu.StopRenderer() #safely close rendering window!