How to add an external force on an object

[kittykisser]

I want to add a concentrated load to this object. I use the component LinearForceField, but it doesn't seem to get the desired effect. Please help me see what is wrong with the code. In the LinearForceField component, "force" is the value of the force and "points" is the point where the force is used. Am I understanding this correctly?

from stlib.physics.deformable import ElasticMaterialObject
from stlib.physics.constraints import FixedBox
from stlib.physics.collision import CollisionMesh
from stlib.scene import Node 
from softrobots.actuators import PullingCable
from splib.loaders import loadPointListFromFile

import Sofa
class BlanketController1(Sofa.PythonScriptController):
    def __init__(self, node, cable):
        self.cableconstraintvalue = cable.getObject("CableConstraint").findData('value')
        self.name = "BlanketController"

    def onKeyPressed(self,c):
        if (c == "1"):
            self.cableconstraintvalue.value =  self.cableconstraintvalue.value[0][0] + 1.
        if (c == "2"):
            self.cableconstraintvalue.value =  self.cableconstraintvalue.value[0][0] - 1.

class BlanketController2(Sofa.PythonScriptController):
    def __init__(self, node, cable):
        self.cableconstraintvalue = cable.getObject("CableConstraint").findData('value')
        self.name = "BlanketController"

    def onKeyPressed(self,c):
        if (c == "3"):
            self.cableconstraintvalue.value =  self.cableconstraintvalue.value[0][0] + 1.
        if (c == "4"):
            self.cableconstraintvalue.value =  self.cableconstraintvalue.value[0][0] - 1.


def Blanket(parentNode=None, name="Blanket",rotation=[0.0, 0.0, 0.0], translation=[0.0, 0.0, 0.0],fixingBox=[0.0,0.0,0.0], pullPointLocation=[0.0,0.0,0.0]):

    blanket = Node(parentNode, "Blanket")
    eobject = ElasticMaterialObject(blanket,
                                    volumeMeshFileName="data/blanket.vtk",
                                    surfaceMeshFileName="data/blanket.stl",
                                    poissonRatio=0.45,
                                    youngModulus=100,
                                    surfaceColor=[0.0,0.7,0.8]
                                    )
    externalForceField = eobject.createObject('LinearForceField', template='Vec3d', name='myExternalForceField')
    externalForceField.findData('forces').value = '0 -10000000 0' 
    externalForceField.findData('points').value = '617'  

    FixedBox(eobject, doVisualization=True, atPositions=[-390,390,-10,-330,330,70])
    FixedBox(eobject, doVisualization=True, atPositions=[390,390,-10,330,330,70])
    FixedBox(eobject, doVisualization=True, atPositions=[-390,-390,-10,-330,-330,70])
    FixedBox(eobject, doVisualization=True, atPositions=[390,-390,-10,330,-330,70])

    cable_numX = 12
    cable_numY = 2

    for i in range(1,cable_numX+1):
        docu_position='data/cableX'+str(i)+'.json'
        i = PullingCable(eobject,cableGeometry=loadPointListFromFile(docu_position))
        BlanketController1(blanket, i)

    for i in range(cable_numX+1,cable_numX+cable_numY+1):
        docu_position ='data/cableY'+str(i-cable_numX)+'.json'
        i = PullingCable(eobject,cableGeometry=loadPointListFromFile(docu_position))
        BlanketController2(blanket, i)


   
    CollisionMesh(eobject,
         surfaceMeshFileName="data/blanket.stl", name="part0")



def createScene(rootNode):
    # -*- coding: utf-8 -*-
    from stlib.scene import MainHeader, ContactHeader
    from stlib.visuals import ShowGrid
    from stlib.physics.rigid import Floor
    from stlib.physics.rigid import Cube
    m=MainHeader(rootNode, plugins=["SoftRobots"],gravity=[0.0,0.0,981.0])
    m.getObject("VisualStyle").displayFlags='showForceFields showBehaviorModels showInteractionForceFields showCollisionModels'
    ContactHeader(rootNode, alarmDistance=4, contactDistance=3, frictionCoef=0.08)

    ShowGrid(rootNode)
    Blanket(rootNode)

    return rootNode

[hugtalbot]

Hey @kittykisser

Which version of SOFA are you using please?
Is your object (without the force) behaving as you expect?

About the force you want to apply, do you want this force to evolve linearly with regards to time while the simulation is running?

• if yes : the LinearForceField is the good component
• if no, simply use a ConstantForceField specifying the point "indices" and the associated nodal "forces"

Hope this helps

[hugtalbot]

Up @kittykisser

[hugtalbot]

⚠️ ⚠️ ⚠️
@kittykisser
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@kittykisser
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@kittykisser
In accordance with our forum management policy, the last reply is more than 4 months old and is therefore closed. Our objective is to keep the forum up to date and offer the best support experience.

Please feel free to reopen it if the topic is still active by providing us with an update. Please feel free to open a new thread at any time - we'll be happy to help where and when we can.