You can view and download this file on Github: hydraulicActuatorSimpleTest.py
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details: A one arm mechanism is actuated by the HydraulicActuatorSimple;
# The actuator contains internal dynamics based on GenericODE1 node
#
# Author: Johannes Gerstmayr
# Date: 2022-06-16
#
# 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 *
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()
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
import numpy as np
from math import sin, cos, sqrt,pi
SC = exu.SystemContainer()
mbs = SC.AddSystem()
L = 1 #x-dim of arm
b = 0.1 #y-dim of arm
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#one arm mechanism
background = GraphicsDataCheckerBoard(point=[0,0.5*L*0,-2*b],size=2)
oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0], visualization=VObjectGround(graphicsData= [background])))
massRigid = 12*10
inertiaRigid = massRigid/12*(L)**2
g = 9.81 # gravity
graphicsList = [GraphicsDataOrthoCubePoint(size= [L,b,0.1*b], color= color4dodgerblue, addEdges=True)]
graphicsList += [GraphicsDataCylinder(pAxis=[-0.5*L,0,-0.7*b], vAxis= [0,0,1.4*b], radius = 0.55*b,
color= color4lightgrey, addEdges=True, nTiles=32)]
#print(graphicsList[2])
nRigid = mbs.AddNode(Rigid2D(referenceCoordinates=[0.5*L,0,0], initialVelocities=[0,0,0]));
oRigid = mbs.AddObject(RigidBody2D(physicsMass=massRigid, physicsInertia=inertiaRigid,nodeNumber=nRigid,
visualization=VObjectRigidBody2D(graphicsData= graphicsList)))
mR1 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[-0.5*L,0.,0.])) #support point
mR2 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[ 0.,0.,0.])) #end point
#add joint
mG0 = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oGround, localPosition=[0,0,0]))
mbs.AddObject(RevoluteJoint2D(markerNumbers=[mG0,mR1]))
mbs.AddLoad(Force(markerNumber = mR2, loadVector = [0, -massRigid*g, 0]))
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#add hydraulics actuator:
mGH = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oGround, localPosition=[0,-0.25*L-0.5*b*0,0.]))
mRH = mbs.AddMarker(MarkerBodyPosition(bodyNumber=oRigid, localPosition=[-0.25*L,-0.5*b*0,0.]))
LH0 = sqrt(2*(0.25*L)**2) #zero length of actuator
#hydraulics parameters:
V0 = 1. #oil volume (could actually change ...)
V1 = V0 #oil volume (could actually change ...)
A=[0.01,0.01] #piston area side 1/2
Eoil = 1e11
Av1 = 1 #valve opening (factor)
Av2 = 0.0 #valve opening (factor)
Qn = 2e-5 #nominal flow
pS = 200.*1e5 #system pressure (200bar)
pT = 0.*1e5 #tank pressure;
dampingHA = 2e5
#ODE1 for pressures:
nODE1 = mbs.AddNode(NodeGenericODE1(referenceCoordinates=[0,0],
initialCoordinates=[2e6,2e6], #initialize with 20 bar
numberOfODE1Coordinates=2))
oHA = mbs.AddObject(HydraulicActuatorSimple(markerNumbers=[mGH, mRH],
nodeNumbers=[nODE1],
offsetLength=LH0, strokeLength=LH0*0.5,
chamberCrossSection0=A[0], chamberCrossSection1=A[1],
hoseVolume0=V0, hoseVolume1=V1,
valveOpening0=0, valveOpening1=0,
oilBulkModulus=Eoil, actuatorDamping=dampingHA, nominalFlow=Qn,
systemPressure=pS, tankPressure=pT,
useChamberVolumeChange=False,
visualization=VHydraulicActuatorSimple(cylinderRadius= 0.6*b, rodRadius= 0.3*b,
baseMountLength = 0.4*b, baseMountRadius = 0.4*b,
rodMountRadius = 0.3*b, pistonLength = 0.2*b, pistonRadius = 0.55*b,
colorCylinder=color4blue, colorPiston=color4lightgrey),
))
def PreStepUserFunction(mbs, t):
LHact = mbs.GetObjectOutput(oHA, variableType=exu.OutputVariableType.Distance)
x = (max(0.5, min(1.5,(1-cos(t*pi*2*0.5))) ) - 0.5)*0.1+LH0
#if t>2: x=LH0
Av0 = (x-LHact)*2 #valve position control ==> penalize set value LH0
#print('Av0=',Av0)
Av1 = -Av0
mbs.SetObjectParameter(oHA, "valveOpening0", Av0)
mbs.SetObjectParameter(oHA, "valveOpening1", Av1)
return True
mbs.SetPreStepUserFunction(PreStepUserFunction)
sForce = mbs.AddSensor(SensorObject(objectNumber=oHA, storeInternal=True, outputVariableType=exu.OutputVariableType.Force))
sDistance = mbs.AddSensor(SensorObject(objectNumber=oHA, storeInternal=True, outputVariableType=exu.OutputVariableType.Distance))
sVelocity = mbs.AddSensor(SensorObject(objectNumber=oHA, storeInternal=True, outputVariableType=exu.OutputVariableType.Velocity))
sPressures = mbs.AddSensor(SensorNode(nodeNumber=nODE1, storeInternal=True, outputVariableType=exu.OutputVariableType.Coordinates))
mbs.Assemble()
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
simulationSettings = exu.SimulationSettings() #takes currently set values or default values
tEnd = 0.4
stepSize = 1e-3
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/stepSize)
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.timeIntegration.startTime = 0
simulationSettings.timeIntegration.newton.relativeTolerance = 1e-8*100 #10000
simulationSettings.timeIntegration.newton.absoluteTolerance = 1e-10
simulationSettings.timeIntegration.verboseMode = 1
# simulationSettings.timeIntegration.simulateInRealtime = True #to see what happens ...
simulationSettings.timeIntegration.newton.useModifiedNewton = True
simulationSettings.timeIntegration.newton.numericalDifferentiation.minimumCoordinateSize = 1
simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 0.5
simulationSettings.displayStatistics = True
simulationSettings.solutionSettings.solutionInformation = 'Hydraulics user function test'
SC.visualizationSettings.openGL.multiSampling = 4
SC.visualizationSettings.openGL.lineWidth = 2
if useGraphics:
exu.StartRenderer()
mbs.WaitForUserToContinue()
mbs.SolveDynamic(simulationSettings, showHints=False)
if useGraphics:
SC.WaitForRenderEngineStopFlag()
exu.StopRenderer() #safely close rendering window!
exu.Print('hydraulics C++:')
exu.Print('pressures=', mbs.GetSensorValues(sPressures))
exu.Print('velocity=', mbs.GetSensorValues(sVelocity))
#for stepSize=1e-6: error about 1e-5 compared to user function implementation; with initialVelocities=[0,0,2] and tEnd=0.4
# hydraulics C++:
# pressures= [6441296.09086297 3008420.04232005]
# velocity= [-0.0050061 0.20338669 0. ]
#
# mbs.PlotSensor(sensorNumbers=sForce, components=exudyn.plot.componentNorm, labels=['connector force norm'], yLabel='force (N)', closeAll=True)
# mbs.PlotSensor(sensorNumbers=sDistance, components=0)
# mbs.PlotSensor(sensorNumbers=[sPressures]*2, components=[0,1], labels=['p1', 'p2'], yLabel='pressure (N/m^2)')
#mbs.PlotSensor(sensorNumbers=p01, components=0, labels=['differential hydraulic force'], yLabel='hydraulic force (N)')
#compute error for test suite:
sol2 = mbs.systemData.GetODE2Coordinates();
sol1 = mbs.systemData.GetODE1Coordinates();
u = np.linalg.norm(sol2);
u += np.linalg.norm(sol1)*1e-6;
exu.Print('solution of hydraulicActuatorSimpleTest =',u)
exudynTestGlobals.testResult = u