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(testmodels-genericode2test)=
# genericODE2test.py

You can view and download this file on Github: [genericODE2test.py](https://github.com/jgerstmayr/EXUDYN/tree/master/python/TestModels/genericODE2test.py)

```{code-block} python
:linenos:

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details:  Test model for GenericODE2
#
# Author:   Johannes Gerstmayr
# Date:     2020-03-09
#
# 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

import numpy as np

testIsActive = exu.sys.get('testIsActive', False)

SC = exu.SystemContainer()
mbs = SC.AddSystem()


#linear spring-damper
L=0.5
mass = 1.6
k = 4000
omega0 = 50 # sqrt(4000/1.6)
dRel = 0.05
d = dRel * 2 * 80 #80=sqrt(1.6*4000)
u0=-0.08
v0=1
f = 80
#static result = f/k = 0.01; 
x0 = f/k
#(exact) dynamic result with u0 and v0: (see bottom of file)

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#node for mass point:
n1=mbs.AddNode(Point(referenceCoordinates = [L,0,0], initialCoordinates = [u0,0,0], initialVelocities= [v0,0,0]))

#add mass points and ground object:
objectGround = mbs.AddObject(ObjectGround(referencePosition = [0,0,0]))
massPoint1 = mbs.AddObject(MassPoint(mass = mass, nodeNumber = n1))

#marker for constraint / springDamper
groundMarker = mbs.AddMarker(MarkerBodyPosition(bodyNumber = objectGround, localPosition= [0, 0, 0]))
bodyMarker = mbs.AddMarker(MarkerBodyPosition(bodyNumber = massPoint1, localPosition= [0, 0, 0]))

mbs.AddObject(CartesianSpringDamper(markerNumbers = [groundMarker, bodyMarker], stiffness = [k,k,k], damping = [d,0,0], offset = [L,0,0]))

#add loads:
mbs.AddLoad(Force(markerNumber = bodyMarker, loadVector = [f, 0, 0]))


#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#node for mass point:

n2=mbs.AddNode(Point(referenceCoordinates = [2*L,0,0], initialCoordinates = [u0,f/k*0.999,0], initialVelocities= [v0,0,0]))

M=np.diag([mass,mass,mass])
#exu.Print("M =",M)
K=np.diag([k,k,k])
#exu.Print("K =",K)
D=np.diag([d,0,d])
#exu.Print("D =",D)
fv=np.array([f,f,0])
#exu.Print("fv =",fv)

fdyn=np.array([0,0,10])

def Sweep(t, t1, f0, f1):
    k = (f1-f0)/t1
    return np.sin(2*np.pi*(f0+k*0.5*t)*t) #take care of factor 0.5 in k*0.5*t, in order to obtain correct frequencies!!!

def UFgenericODE2(mbs, t, itemIndex, q, q_t):
    #f = np.sin(t*2*np.pi*10)*fdyn
    f = Sweep(t,10,1,100)*fdyn
    return f
    #exu.Print("t =", t, ", f =", f)

def UFmassGenericODE2(mbs, t, itemIndex, q, q_t):
    return 1*M

mbs.AddObject(ObjectGenericODE2(nodeNumbers = [n2], massMatrix=M, stiffnessMatrix=K, dampingMatrix=D, forceVector=fv, 
                                forceUserFunction=UFgenericODE2, massMatrixUserFunction=UFmassGenericODE2))

#exu.Print(mbs)
mbs.Assemble()

simulationSettings = exu.SimulationSettings()
simulationSettings.timeIntegration.newton.useModifiedNewton = False #Just for the test; modified Newton is usually faster

tEnd = 1
steps = 2000
simulationSettings.timeIntegration.numberOfSteps = steps
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.solution.file.writePeriod = tEnd/steps
simulationSettings.timeIntegration.verboseMode = 1
#simulationSettings.solution.file.writePeriod = tEnd/steps

simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 1 #SHOULD work with 0.9 as well

mbs.SolveDynamic(simulationSettings)

u1 = mbs.GetNodeOutput(n1, exu.OutputVariableType.Coordinates)
#exu.Print("u1 =", u1)
u2 = mbs.GetNodeOutput(n2, exu.OutputVariableType.Coordinates)
#exu.Print("u2 =", u2)

u=np.linalg.norm(u1) + np.linalg.norm(u2)
exu.Print('solution of genericODE2test=',u)

exu.sys['testResult'] = u
```