VectorSpringForceField not working with ArticulatedSystemMapping

[BrunoB81HK]

Hi!

I’m currently trying to use the ArticulatedSystemMapping to implement a grabbing system in a scene. It seems to work as expected.

My next step would be to link the articulated system to a reference model with a VectorSpringForceField like in the Geomagic plugin examples. When trying to do this, I can’t seems to make it move.

As a sanity check, I tried to use input2 with the reference model directly and it moved with the reference. The thing is, I need a VectorSpringForceField for contact stability reasons.

My scene can be illustrated as this image :

where :
(1) is 3 Rigid3d mechanical objects (Shaft, LeftJaw and RightJaw). (@Instrument/Trex/DOFs in scene)
(2) is a Vec3d mechanical object (Shaft). (@Instrument/Trex/Ref/RefModel in scene)
(3) is 3 Vec3d mechanical objects (a -> Shaft, b -> LeftJaw and c -> RightJaw). (@Instrument/Jaw/Models/*Col/*ColModel in scene)
(4) is 3 Rigid3d mechanical object using the ArticulatedSystemMapping. (@Instrument/Jaw/Models/DOFs in scene)

The significant part of the scene is as follow :

<Node name="Instrument">

    <Node name="Trex">

        <MechanicalObject name="DOFs" template="Rigid3d" size="3" position="@TrexDriver.positionsGrab"/>

        <Node name="Ref">
            <MeshObjLoader name="loader" filename="../../mesh/Instrument/ShaftCol.obj"/>
            <MeshTopology src="@loader"/>
            <MechanicalObject name="RefModel" src="@loader"/>
            <RigidMapping input="@../DOFs" output="@RefModel" index="0"/>
        </Node>

        <Node name="ShaftVis" activated="true" >
            <MeshObjLoader name="loader" filename="../../mesh/Instrument/Shaft.obj"/>
            <OglModel name="TrexVisModel" src="@loader" color="0.17 1.00 1.00 1.00"/>
            <RigidMapping input="@../DOFs" output="@TrexVisModel" index="0"/>
        </Node>

        <Node name="LeftJawVis" activated="true" >
            <MeshObjLoader name="loader" filename="../../mesh/Instrument/PokeL.obj"/>
            <OglModel name="TrexVisModel" src="@loader" color="0.17 1.00 1.00 1.00"/>
            <RigidMapping input="@../DOFs" output="@TrexVisModel" index="1"/>
        </Node>

        <Node name="RightJawVis" activated="true" >
            <MeshObjLoader name="loader" filename="../../mesh/Instrument/PokeR.obj"/>
            <OglModel name="TrexVisModel" src="@loader" color="0.17 1.00 1.00 1.00"/>
            <RigidMapping input="@../DOFs" output="@TrexVisModel" index="2"/>
        </Node>

        <Node name="Base">
            <MechanicalObject name="DOFs" template="Rigid3d" position="@TrexDriver.positionPoke"/>
        </Node>

    </Node>

    <Node name="Jaws">
        <MechanicalObject name="Joints" template="Vec1d" size="2" position="@TrexDriver.pliersAngles"/>

        <Node name="Models">

            <MechanicalObject name="DOFs" template="Rigid3d" size="3"/>

            <!-- Shaft -->
            <Node name="ShaftVis">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/Shaft.obj"/>
                <OglModel name="ShaftVisualModel" src="@loader"/>
                <RigidMapping input="@../DOFs" output="@ShaftVisualModel" index="0"/>
            </Node>

            <Node name="ShaftCol">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/ShaftCol.obj"/>
                <MeshTopology src="@loader"/>
                <MechanicalObject name="InstrumentColModel" src="@loader"/>
                <PointCollisionModel contactStiffness="10"/>
                <RigidMapping input="@../DOFs" output="@InstrumentColModel" index="0"/>
            </Node>

            <!-- Left jaw -->
            <Node name="JawLeftVis">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/PokeL.obj"/>
                <OglModel name="JawLeftVisualModel" src="@loader"/>
                <RigidMapping input="@../DOFs" output="@JawLeftVisualModel" index="1"/>
            </Node>

            <Node name="JawLeftCol">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/JawCol.obj"/>
                <MeshTopology src="@loader"/>
                <MechanicalObject name="JawLeftColModel" src="@loader"/>
                <PointCollisionModel contactStiffness="10"/>
                <RigidMapping input="@../DOFs" output="@JawLeftColModel" index="1"/>
            </Node>

            <!-- Right jaw -->
            <Node name="JawRightVis">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/PokeR.obj"/>
                <OglModel name="JawRightVisualModel" src="@loader"/>
                <RigidMapping input="@../DOFs" output="@JawRightVisualModel" index="2"/>
            </Node>

            <Node name="JawRightCol">
                <MeshObjLoader name="loader" filename="../../mesh/Instrument/JawCol.obj"/>
                <MeshTopology src="@loader"/>
                <MechanicalObject name="JawRightColModel" src="@loader"/>
                <PointCollisionModel contactStiffness="10"/>
                <RigidMapping input="@../DOFs" output="@JawRightColModel" index="2"/>
            </Node>

            <ArticulatedSystemMapping input1="@../Joints" input2="@../../Trex/Base/DOFs" output="@DOFs"/>

        </Node>

        <ArticulatedHierarchyContainer/>

        <Node name="ArticulationDef">
            <Node name="Left">
                <ArticulationCenter parentIndex="0" childIndex="1" posOnParent="0 0 0" posOnChild="0 0 0"/>
                <Node name="Articulation">
                    <Articulation translation="0" rotation="1" rotationAxis="0 0 1" articulationIndex="0"/>
                </Node>
            </Node>

            <Node name="Right">
                <ArticulationCenter parentIndex="0" childIndex="2" posOnParent="0 0 0" posOnChild="0 0 0"/>
                <Node name="Articulation">
                    <Articulation translation="0" rotation="1" rotationAxis="0 0 1" articulationIndex="1"/>
                </Node>
            </Node>

        </Node>

    </Node>

    <VectorSpringForceField  template="Vec3d" object1="@Trex/Ref/RefModel"
                             object2="@Jaws/Models/ShaftCol/InstrumentColModel" stiffness="1000" viscosity="0" printLog="1"/>

</Node>

I’m not quite sure where to go from here and I would like some help!

Thanks a lot and have a nice day.

Bruno

[Hugo]

Hey @brunob81hk

Sorry for replying so late but I was hoping someone else (better than me on the topic) would have answered.

I never built a simulation with a jaw model for grasping. I guess you got inspired from both the Xitact and Geomagic examples.

Without the meshes I cannot run the scene, let me know if you are willing to share them.

Could you try using : input2="@DOFs" ?
You would have the articulated system independent from the Trex position but managing the opening/closing of the jaw. The “Trex” node in charge of following the Trex device and the VectorSpringFF connecting the two for stability.

Let me know if it helps.

@epernod if you recall how to build a jaw model it is also welcome 😉

Sorry for being approximated Bruno,

Hugo

[Author]

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