connectorRigidBodySpringDamperTest.py
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1#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2# This is an EXUDYN example
3#
4# Details: Test for RigidBodySpringDamper with springForceTorqueUserFunction;
5# the RigidBodySpringDamper can be used to model complicance effects in joints where
6# one axis undergoes large rotations, and the other rotations are small
7#
8# Author: Johannes Gerstmayr
9# Date: 2021-01-07
10#
11# 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.
12#
13#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
14
15import sys
16sys.path.append('../TestModels') #for modelUnitTest as this example may be used also as a unit test
17
18import exudyn as exu
19from exudyn.utilities import *
20from exudyn.graphicsDataUtilities import *
21import numpy as np
22
23useGraphics = True #without test
24#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
25#you can erase the following lines and all exudynTestGlobals related operations if this is not intended to be used as TestModel:
26try: #only if called from test suite
27 from modelUnitTests import exudynTestGlobals #for globally storing test results
28 useGraphics = exudynTestGlobals.useGraphics
29except:
30 class ExudynTestGlobals:
31 pass
32 exudynTestGlobals = ExudynTestGlobals()
33#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
34
35SC = exu.SystemContainer()
36mbs = SC.AddSystem()
37
38oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0]))
39nGround = mbs.AddNode(NodePointGround(referenceCoordinates=[0,0,0]))
40
41#example with rigid body at [0,0,0], 1kg under initial velocity
42graphicsBody = GraphicsDataOrthoCubePoint(centerPoint=[0,0,0],size=[0.09,0.09,0.2], color=color4lightred)
43nBody = mbs.AddNode(RigidRxyz(initialVelocities=[0,10,0, 2*pi*4,0,0]))
44oBody = mbs.AddObject(RigidBody(physicsMass=1, physicsInertia=[1,1,1,0,0,0], nodeNumber=nBody,
45 visualization=VRigidBody(graphicsData=[graphicsBody])))
46
47mBody = mbs.AddMarker(MarkerNodeRigid(nodeNumber=nBody))
48mGround = mbs.AddMarker(MarkerBodyRigid(bodyNumber=oGround,
49 localPosition = [0,0,0]))
50
51def UFforce(mbs, t, itemIndex, displacement, rotation, velocity, angularVelocity, stiffness, damping, rotJ0, rotJ1, offset):
52 k = stiffness
53 u = displacement
54 v = velocity
55 w = angularVelocity
56 rot = rotation
57 return [u[0]*k[0][0],u[1]*k[1][1]+v[1]*0.01*k[1][1],u[2]*k[2][2],
58 rot[0]*k[0][0]+w[0]*0.001*k[0][0],rot[1]*k[0][0],rot[2]*k[0][0]]
59
60#markerNumbers and parameters taken from mini example
61k=5000
62mbs.AddObject(RigidBodySpringDamper(markerNumbers = [mGround, mBody],
63 stiffness = np.diag([k,k,k, 0,0,0]),
64 damping = np.diag([0,k*0.01,0, 0,0,0]),
65 offset = [0,1,0, 0,0,0],
66 springForceTorqueUserFunction = UFforce))
67
68mbs.Assemble()
69
70tEnd = 0.1
71h=1e-3
72if useGraphics:
73 tEnd = 1 #parameters sucht that we can see some motion
74 h=1e-5
75
76
77simulationSettings = exu.SimulationSettings()
78simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
79simulationSettings.timeIntegration.endTime = tEnd
80simulationSettings.solutionSettings.writeSolutionToFile = False
81
82simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 1 #no numerical damping
83
84simulationSettings.displayStatistics = True
85simulationSettings.timeIntegration.verboseMode = 1
86
87if useGraphics:
88 exu.StartRenderer() #start graphics visualization
89 mbs.WaitForUserToContinue() #wait for pressing SPACE bar to continue
90
91#start solver:
92mbs.SolveDynamic(simulationSettings)
93
94if useGraphics:
95 SC.WaitForRenderEngineStopFlag()#wait for pressing 'Q' to quit
96 exu.StopRenderer() #safely close rendering window!
97
98p0=mbs.GetObjectOutputBody(oBody, localPosition=[0.1,0.1,0.1],
99 variableType = exu.OutputVariableType.Position)
100result = p0[0]+p0[1]
101exu.Print('solution of connectorRigidBodySpringDamperTest=',result) #use x-coordinate
102
103exudynTestGlobals.testError = result - (0.18276224743714353) #2021-01-07:
104exudynTestGlobals.testResult = result