kinematicTreeTest.py

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

  1#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  2# This is an EXUDYN example
  3#
  4# Details:  Test model for KinematicTree, using simple 3D chain;
  5#           results have been compared to redundant links in Examples/kinematicTreeAndMBS.py
  6#
  7# Author:   Johannes Gerstmayr
  8# Date:     2022-05-05
  9#
 10# 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.
 11#
 12#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 13
 14import exudyn as exu
 15from exudyn.utilities import *
 16
 17import numpy as np
 18
 19useGraphics = True #without test
 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
 31SC = exu.SystemContainer()
 32mbs = SC.AddSystem()
 33
 34
 35L = 2 #length of links
 36w = 0.1 #width of links
 37J = InertiaCuboid(density=1000, sideLengths=[L,w,w]) #w.r.t. reference center of mass
 38J = J.Translated([0.5*L,0,0])
 39com = J.com
 40
 41gravity3D = [0,-10,0]
 42
 43n=5 #5#number of coordinates
 44
 45linkMasses = []
 46linkCOMs = exu.Vector3DList()
 47linkInertiasCOM=exu.Matrix3DList()
 48
 49jointTransformations=exu.Matrix3DList()
 50jointOffsets = exu.Vector3DList()
 51for i in range(n):
 52    #create some rotated axis and offsets...
 53    A=np.eye(3)
 54    if i%2 != 0:
 55        A=RotXYZ2RotationMatrix([0*0.5*pi,0.25*pi,0])
 56    if i%3 >= 1:
 57        A=RotXYZ2RotationMatrix([0.5*pi,0.25*pi,0])
 58
 59    v = np.array([L,0,0])
 60    if i==0:
 61        v = np.array([0,0,0])
 62
 63    #now add joint/link to lists:
 64    jointTransformations.Append(A)
 65    jointOffsets.Append(v)
 66
 67    linkMasses += [J.Mass()]
 68    linkCOMs.Append(J.COM())
 69    linkInertiasCOM.Append(J.InertiaCOM())
 70
 71
 72# linkForces = exu.Vector3DList([[0.,0.,0.]]*n)
 73# linkTorques = exu.Vector3DList([[0.,0.,0.]]*n)
 74
 75#create per-link graphics:
 76gLink =  GraphicsDataOrthoCubePoint(centerPoint= [0.5*L,0,0], size= [L,w,w], color= color4dodgerblue)
 77gJoint = GraphicsDataCylinder([0,0,-1.25*w], [0,0,2.5*w], 0.4*w, color=color4grey)
 78gList = [[gJoint,gLink]]*n #one list per link; add joint first, then it will be visible with transparency setting
 79
 80#create node for unknowns of KinematicTree
 81nGeneric = mbs.AddNode(NodeGenericODE2(referenceCoordinates=[0.]*n,
 82                                       initialCoordinates=[0.]*n,
 83                                       initialCoordinates_t=[0.]*n,
 84                                       numberOfODE2Coordinates=n))
 85
 86#create KinematicTree
 87mbs.AddObject(ObjectKinematicTree(nodeNumber=nGeneric, jointTypes=[exu.JointType.RevoluteZ]*n, linkParents=np.arange(n)-1,
 88                                  jointTransformations=jointTransformations, jointOffsets=jointOffsets,
 89                                  linkInertiasCOM=linkInertiasCOM, linkCOMs=linkCOMs, linkMasses=linkMasses,
 90                                  baseOffset = [0.,0.,0.], gravity=gravity3D,
 91                                  #jointForceVector=[0.]*n,
 92                                  visualization=VObjectKinematicTree(graphicsDataList = gList)))
 93
 94
 95mbs.Assemble()
 96
 97tEnd = 1     #end time of simulation
 98h = 0.005    #step size; leads to 1000 steps
 99
100simulationSettings = exu.SimulationSettings()
101simulationSettings.solutionSettings.writeSolutionToFile=False
102simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h) #must be integer
103simulationSettings.timeIntegration.endTime = tEnd
104simulationSettings.timeIntegration.verboseMode = 1
105
106SC.visualizationSettings.bodies.kinematicTree.frameSize = 1
107SC.visualizationSettings.bodies.kinematicTree.showJointFrames = True
108SC.visualizationSettings.general.drawWorldBasis = True
109SC.visualizationSettings.general.worldBasisSize = 2
110SC.visualizationSettings.openGL.multiSampling = 4
111
112if useGraphics:
113    exu.StartRenderer()              #start graphics visualization
114    mbs.WaitForUserToContinue()    #wait for pressing SPACE bar to continue
115
116mbs.SolveDynamic(simulationSettings, solverType = exu.DynamicSolverType.RK44)
117
118if useGraphics:
119    SC.WaitForRenderEngineStopFlag()#wait for pressing 'Q' to quit
120    exu.StopRenderer()               #safely close rendering window!
121
122#evaluate final (=current) output values
123q = mbs.GetNodeOutput(nGeneric, exu.OutputVariableType.Coordinates)
124exu.Print('coordinates=',q)
125
126u=sum(q)
127exu.Print('solution of genericODE2test=',u)
128#solution converged to 14 digits (h=5e-5): -1.3093839514061
129
130exudynTestGlobals.testError = u - (-1.309383960216414 ) #2022-05-05: -1.309383960216414 (accurate to 8 digits)
131exudynTestGlobals.testResult = u