You can view and download this file on Github: chatGPTupdate.py
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an Exudyn file
#
# Details: this file serves as a list of examples that shall be used by
# ChatGPT to update information on its internal knowledge of Exudyn
# dating to 2021; the examples use the mainSystemExtensions
# which are heavily simplifying usage of point masses and rigid bodies
# Version: V1
#
# Author: Johannes Gerstmayr
# Date: 2023-06-30
#
# 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.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#copy the text below here into a ChatGPT input window:
#Use the following information as an update of the internal data of the Python multibody code Exudyn.
#See the following examples to create multibody systems in Exudyn.
#NOTE: mbs.Create...(...) calls several functions in the background to create nodes, objects, markers and loads in Exudyn.
#all quantities are giving as 3D lists [x,y,z] for positions, velocities, ....
#rotations are usually given as rotation matrix (numpy array);
#RotationVector2RotationMatrix([rotX, rotY, rotZ]) computes a rotation around the global x,y,z rotation axis
#%%++++++++++++++++++++++++++++++++++++++++++++++++++++
#create rigid bodies and mass points with distance constraint and joints
import exudyn as exu
from exudyn.utilities import * #includes itemInterface, graphicsDataUtilities and rigidBodyUtilities
import numpy as np
SC = exu.SystemContainer()
mbs = SC.AddSystem() #create a MainSystem 'mbs' to work with
#draw orthonormal cube in local frame where it is added to;
#cube is added to reference point of object, usually the center of mass (COM):
graphicsCube = GraphicsDataOrthoCubePoint(centerPoint = [0,0,0],
size=[1,0.1,0.1], color=color4orange)
#create inertia (mass, COM, inertia tensor) to be used in rigid body:
inertiaCube = InertiaCuboid(density=5000, sideLengths=[1,0.1,0.1])
#create simple rigid body
#note that graphics is always attached to reference point of body, which is by default the COM
b0 = mbs.CreateRigidBody(inertia = inertiaCube,
referencePosition = [0.5,0,0], #reference position x/y/z of COM
referenceRotationMatrix=RotationVector2RotationMatrix([0,0,pi*0.5]),
initialAngularVelocity=[2,0,0],
initialVelocity=[0,4,0],
gravity = [0,-9.81,0],
graphicsDataList = [graphicsCube])
#add an load with user function:
def UFforce(mbs, t, loadVector):
#define time-dependent function:
return [10+5*np.sin(t*10*2*pi),0,0]
mbs.CreateForce(bodyNumber=b0, localPosition=[-0.5,0,0],
loadVector=[10,0,0],
loadVectorUserFunction=UFforce,
) #load is 10N in x-direction
#add torque to rigid body at left end
mbs.CreateTorque(bodyNumber=b0, localPosition=[0.5,0,0],
loadVector=[0,1,0]) #torque of 1N around y-axis
#create a simple mass point at [1,-1,0] with initial velocity
m1 = mbs.CreateMassPoint(referencePosition=[1,-1,0],
initialVelocity = [2,5,0], #initial velocities for mass point
physicsMass=1, drawSize = 0.2)
#we can obtain the node number from the mass point:
n1 = mbs.GetObject(m1)['nodeNumber']
#add a ground object:
#graphics data for sphere:
gGround0 = GraphicsDataSphere(point=[3,1,0], radius = 0.1, color=color4red, nTiles=16)
#graphics for checkerboard background:
gGround1 = GraphicsDataCheckerBoard(point=[3,0,-2], normal=[0,0,1], size=10)
oGround = mbs.CreateGround(graphicsDataList=[gGround0,gGround1])
#create a rigid distance between bodies (using local position) or between nodes
mbs.CreateDistanceConstraint(bodyOrNodeList=[oGround, b0],
localPosition0 = [ 0. ,0,0],
localPosition1 = [-0.5,0,0],
distance=None, #automatically computed
drawSize=0.06)
#distance constraint between body b0 and mass m1
mbs.CreateDistanceConstraint(bodyOrNodeList=[b0, m1],
localPosition0 = [0.5,0,0],
localPosition1 = [0.,0.,0.], #must be [0,0,0] for Node
distance=None, #automatically computed
drawSize=0.06)
#add further rigid body, which will be connected with joints
b1 = mbs.CreateRigidBody(inertia = InertiaCuboid(density=5000, sideLengths=[1,0.1,0.1]),
referencePosition = [2.5,0,0], #reference position x/y/z
gravity = [0,-9.81,0],
graphicsDataList = [graphicsCube])
b2 = mbs.CreateRigidBody(inertia = InertiaCuboid(density=5000, sideLengths=[1,0.1,0.1]),
referencePosition = [3.5,0,0], #reference position x/y/z
gravity = [0,-9.81,0],
graphicsDataList = [graphicsCube])
#create revolute joint with following args:
# name: name string for joint; markers get Marker0:name and Marker1:name
# bodyNumbers: a list of object numbers for body0 and body1; must be rigid body or ground object
# position: a 3D vector as list or np.array: if useGlobalFrame=True it describes the global position of the joint in reference configuration; else: local position in body0
# axis: a 3D vector as list or np.array: if useGlobalFrame=True it describes the global rotation axis of the joint in reference configuration; else: local axis in body0
# useGlobalFrame: if False, the point and axis vectors are defined in the local coordinate system of body0
# show: if True, connector visualization is drawn
# axisRadius: radius of axis for connector graphical representation
# axisLength: length of axis for connector graphical representation
# color: color of connector
#returns list [oJoint, mBody0, mBody1], containing the joint object number, and the two rigid body markers on body0/1 for the joint
mbs.CreateRevoluteJoint(bodyNumbers=[b1, b2], position=[3,0,0], axis=[0,0,1], #rotation along global z-axis
useGlobalFrame=True, axisRadius=0.02, axisLength=0.14)
#create prismatic joint with following args:
# name: name string for joint; markers get Marker0:name and Marker1:name
# bodyNumbers: a list of object numbers for body0 and body1; must be rigid body or ground object
# position: a 3D vector as list or np.array: if useGlobalFrame=True it describes the global position of the joint in reference configuration; else: local position in body0
# axis: a 3D vector as list or np.array containing the global translation axis of the joint in reference configuration
# useGlobalFrame: if False, the point and axis vectors are defined in the local coordinate system of body0
# show: if True, connector visualization is drawn
# axisRadius: radius of axis for connector graphical representation
# axisLength: length of axis for connector graphical representation
# color: color of connector
#returns list [oJoint, mBody0, mBody1], containing the joint object number, and the two rigid body markers on body0/1 for the joint
mbs.CreatePrismaticJoint(bodyNumbers=[oGround, b1], position=[2,0,0], axis=[1,0,0], #can move in global x-direction
useGlobalFrame=True, axisRadius=0.02, axisLength=1)
# #instead of the prismatic joint, we could add another revolute joint to b1 to get a double-pendulum:
# mbs.CreateRevoluteJoint(bodyNumbers=[oGround, b1], position=[2,0,0], axis=[0,0,1],
# useGlobalFrame=True, axisRadius=0.02, axisLength=0.14)
#create simple mass point, connected with ground
m2 = mbs.CreateMassPoint(referencePosition = [7,2,0],
physicsMass = 10, gravity = [0,-9.81,0],
drawSize = 0.5, color=color4blue)
#create spring damper between bodies (using local position) or between nodes
#spring-damper may not have size 0; spring reference length is computed from reference configuration
oSD = mbs.CreateSpringDamper(bodyOrNodeList=[oGround, m2],
localPosition0=[6,0,0],
localPosition1=[0,0,0],
stiffness=1e3, damping=1e1,
drawSize=0.2)
#alternatively, we can use a CartesianSpringDamper; has spring and damper coefficients as list of x/y/z components
#it has no reference length and acts on the coordinates of both objects:
oCSD = mbs.CreateCartesianSpringDamper(bodyOrNodeList=[oGround, m2],
localPosition0=[7,2,0],
localPosition1=[0,0,0],
stiffness=[20,0,1e4], #stiffness in x/y/z direction
damping=[0.1,0,10],
drawSize=0.2)
#prepare mbs for simulation:
mbs.Assemble()
#some simulation parameters:
simulationSettings = exu.SimulationSettings() #takes currently set values or default values
simulationSettings.timeIntegration.numberOfSteps = 1000
simulationSettings.timeIntegration.endTime = 5
#for redundant constraints, the following two settings:
simulationSettings.linearSolverSettings.ignoreSingularJacobian=True
simulationSettings.linearSolverType = exu.LinearSolverType.EigenDense
mbs.SolveDynamic(simulationSettings = simulationSettings,
solverType=exu.DynamicSolverType.GeneralizedAlpha)
SC.visualizationSettings.nodes.drawNodesAsPoint=False #draw nodes as spheres; better graphics for nodes
#visualize results:
mbs.SolutionViewer()