Box slips on pallet when moved using LinearMovementProjectiveConstraint

[PatrickDNeobird]

Hi all,

I'm simulating deformable boxes placed on a rigid pallet. The pallet moves horizontally using a LinearMovementProjectiveConstraint, and the boxes are expected to stay on the pallet due to friction. However, in my simulation, the box slips off as soon as the pallet starts moving, despite gravity acting on it and a mu=0.5 friction coefficient set.

Here is a simple setup with one box:

<Node name="root" dt="0.0005">
    
    <VisualStyle displayFlags="showVisualModels showForceFields" />
    <FreeMotionAnimationLoop parallelCollisionDetectionAndFreeMotion="true" parallelODESolving="true" />
    <GenericConstraintSolver tolerance="0.001" maxIt="1000" computeConstraintForces="1" />
    <CollisionPipeline verbose="0" depth="6" draw="0" />
    <BruteForceBroadPhase />
    <BVHNarrowPhase />
    <LocalMinDistance alarmDistance="0.005" contactDistance="0.001" angleCone="0" />
    <CollisionResponse response="FrictionContactConstraint" responseParams="mu=0.5" />
    
    <Node name="Palette">
        <MeshSTLLoader name="Loader-Palette" filename="Meshes\palette.stl" translation="0 -0.17 0" rotation="0 0 0" />
        <EulerImplicitSolver rayleighMass="0.1" rayleighStiffness="0.01" />
        <CGLinearSolver template="CompressedRowSparseMatrixMat3x3d" iterations="200" tolerance="1E-09" threshold="1E-09" />
        <MechanicalObject template="Rigid3" />
	<LinearSolverConstraintCorrection />
        <LinearMovementProjectiveConstraint name="LMPC-Palette" keyTimes="0 2 " movements="0 0 0  0 0 0 1 0 0  0 0 0" />
        <Node name="Visual-Palette">
            <OglModel name="Model-Visual-Palette" src="@../Loader-Palette" color="blue" />
            <RigidMapping input="@.." output="@Model-Visual-Palette" />
        </Node>
        <Node name="Surface-Palette">
            <MeshTopology src="@../Loader-Palette" />
            <MechanicalObject src="@../Loader-Palette" name="MO-Surface-Palette" template="Vec3" />
            <TriangleCollisionModel />
            <LineCollisionModel />
            <PointCollisionModel />
            <RigidMapping />
        </Node>
    </Node>
    
    <Node name="Box-27-0-978">
        <MeshGmshLoader name="VolumeMesh-Loader-27-0-978" filename="Meshes\box_284x154x189.msh" translation="0.027 0 0.978" rotation="0 0 0" />
        <MeshSTLLoader name="SurfaceMesh-Loader-27-0-978" filename="Meshes\box_284x154x189.stl" translation="0.027 0 0.978" rotation="0 0 0" />
        <TetrahedronSetTopologyContainer name="Topo-27-0-978" src="@VolumeMesh-Loader-27-0-978" />
        <EulerImplicitSolver rayleighMass="0.01" rayleighStiffness="0.001" />
        <CGLinearSolver template="CompressedRowSparseMatrixMat3x3d" iterations="200" tolerance="1E-09" threshold="1E-09" />
        <MechanicalObject template="Vec3d" name="MO-27-0-978" src="@VolumeMesh-Loader-27-0-978" />
        <UniformMass totalMass="1.5" />
        <TetrahedronFEMForceField youngModulus="100000" poissonRatio="0.3" computeGlobalMatrix="false" plasticYieldThreshold="0.01" plasticMaxThreshold="0.05" plasticCreep="0.5" />
        <LinearSolverConstraintCorrection />
        <Node name="Visual-27-0-978">
            <OglModel name="Model-Visual-27-0-978" src="@../SurfaceMesh-Loader-27-0-978" color="red" />
            <BarycentricMapping template="Vec3d,Vec3d" input="@.." output="@Model-Visual-27-0-978" />
        </Node>
        <Node name="Surface-27-0-978">
            <MeshTopology src="@../SurfaceMesh-Loader-27-0-978" />
            <MechanicalObject name="Surface-MO-27-0-978" />
            <TriangleCollisionModel />
            <LineCollisionModel />
            <PointCollisionModel />
            <BarycentricMapping template="Vec3d,Vec3d" input="@.." />
        </Node>
    </Node>
</Node>

What I tried:

• Confirmed that collision contact points are detected (force fields and constraints are active).

• Increased the friction coefficient (mu) to higher values.

• Increased the mass of the boxes.

• Verified solver, constraint correction, and mechanical setup on both objects.

My questions are:

• Does the LinearMovementProjectiveConstraint integrate correctly with the FrictionContactConstraint in this setup?

• Is there a special setup required to make friction constraints apply correctly between a Rigid3 object and a deformable one?

Any insight or suggestions would be greatly appreciated!

Thanks in advance!

[bakpaul]

Hello !

I am sorry but the way the component imposes the displacement is not compatible with using friction. In fact, this component will override the position of the pallet at a moment where the contact solver will not be aware of. So the cube will never follow the motion.

Could you try using the LinearVelocityProjectiveConstraint instead ? I am not sure this will solve the issue but it is worth the try. Here, instead of imposing the position, you are imposing a velocity. If was I hope is right, the position will be computed correctly and be taken into account by the solver. But this is a part of the API that I don't master entirely.

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