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rigidBodyTutorial3.py

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#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details:  3D rigid body tutorial with 2 bodies and revolute joints, using new mainSystemExtension functionality
#
# Author:   Johannes Gerstmayr
# Date:     2023-05-16
#
# 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 * #includes itemInterface, graphicsDataUtilities and rigidBodyUtilities
import numpy as np

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


#%%++++++++++++++++++++++++++++++++++++++++++++++++++++
#physical parameters
g =     [0,-9.81,0] #gravity
L = 1               #length
w = 0.1             #width
bodyDim=[L,w,w] #body dimensions
p0 =    [0,0,0]     #origin of pendulum
pMid0 = np.array([L*0.5,0,0]) #center of mass, body0

#ground body, located at specific position (there could be several ground objects)
oGround = mbs.CreateGround(referencePosition=[0,0,0])

#%%++++++++++++++++++++++++++++++++++++++++++++++++++++
#first link:
iCube0 = InertiaCuboid(density=5000, sideLengths=bodyDim)
iCube0 = iCube0.Translated([-0.25*L,0,0]) #transform COM, COM not at reference point!

#graphics for body
graphicsBody0 = GraphicsDataOrthoCubePoint(centerPoint=[0,0,0],size=[L,w,w],color=color4red)
graphicsCOM0 = GraphicsDataBasis(origin=iCube0.com, length=2*w) #COM frame

#create rigid node and body
b0=mbs.CreateRigidBody(inertia = iCube0, #includes COM
                       referencePosition = pMid0,
                       gravity = g,
                       graphicsDataList = [graphicsCOM0, graphicsBody0])
#revolute joint (free z-axis), axis and position given in global coordinates
#  using reference configuration
mbs.CreateRevoluteJoint(bodyNumbers=[oGround, b0], position=[0,0,0],
                        axis=[0,0,1], axisRadius=0.2*w, axisLength=1.4*w)


#%%++++++++++++++++++++++++++
#second link:
graphicsBody1 = GraphicsDataRigidLink(p0=[0,0,-0.5*L],p1=[0,0,0.5*L],
                                     axis0=[1,0,0], axis1=[0,0,0], radius=[0.06,0.05],
                                     thickness = 0.1, width = [0.12,0.12], color=color4lightgreen)

b1=mbs.CreateRigidBody(inertia = InertiaCuboid(density=5000, sideLengths=[0.1,0.1,1]),
                            referencePosition = np.array([L,0,0.5*L]), #reference pos = center of mass, body1
                            gravity = g,
                            graphicsDataList = [graphicsBody1])

#revolute joint (free x-axis), axis and position given in global coordinates,
#  using reference configuration
mbs.CreateRevoluteJoint(bodyNumbers=[b0, b1], position=[L,0,0],
                        axis=[1,0,0], axisRadius=0.2*w, axisLength=1.4*w)

#forces can be added like in the following
force = [0,0.5,0]       #0.5N   in y-direction
torque = [0.1,0,0]      #0.1Nm around x-axis
mbs.CreateForce(bodyNumber=b1,
                loadVector=force,
                localPosition=[0,0,0.5], #at tip
                bodyFixed=False) #if True, direction would corotate with body
mbs.CreateTorque(bodyNumber=b1,
                loadVector=torque,
                localPosition=[0,0,0],   #at body's reference point/center
                bodyFixed=False) #if True, direction would corotate with body

#position sensor at tip of body1
sens1=mbs.AddSensor(SensorBody(bodyNumber=b1, localPosition=[0,0,0.5*L],
                               fileName='solution/sensorPos.txt',
                               outputVariableType = exu.OutputVariableType.Position))

#%%++++++++++++++++++++++++++++++++++++++++++++++++++++++
#assemble system before solving
mbs.Assemble()

mbs.ComputeSystemDegreeOfFreedom(verbose=True) #print out DOF and further information

simulationSettings = exu.SimulationSettings() #takes currently set values or default values

tEnd = 4 #simulation time
h = 1e-3 #step size
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.timeIntegration.verboseMode = 1
simulationSettings.solutionSettings.solutionWritePeriod = 0.005 #store every 5 ms

SC.visualizationSettings.window.renderWindowSize=[1600,1200]
SC.visualizationSettings.openGL.multiSampling = 4

SC.visualizationSettings.nodes.showBasis=True

#start solver
mbs.SolveDynamic(simulationSettings = simulationSettings,
                 solverType=exu.DynamicSolverType.TrapezoidalIndex2)

#load solution and visualize
mbs.SolutionViewer()


if True:

    mbs.PlotSensor(sensorNumbers=[sens1],components=[1],closeAll=True)

if False:
    mbs.DrawSystemGraph(useItemTypes=True) #draw nice graph of system