Lock coordinate while creating the model

[Hao Lee]

I am modifying the DynamicWalkingStarter to more degree of freedom. I add a FreeJoint in the model, but only want it to have 3 DOF. I try to call the "setLocked" in my matlab code but failed to execute it.
Part of code is shown as below (without setLocked since it failed, now I set the range to 0 but this isn't what I want)

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platformToPelvis = FreeJoint('PlatformToPelvis',platform,locationInParent,orientationInParent,pelvis,locationInChild,orientationInChild,false);

% Update the coordinates of the new joint
jointCoordinateSet1  = platformToPelvis.upd_CoordinateSet();

jointCoordinateSet1.get(0).setRange([0, 0]);
jointCoordinateSet1.get(0).setName('Pelvis_rx');
jointCoordinateSet1.get(0).setDefaultValue(0);
jointCoordinateSet1.get(0).setLocked(true);

jointCoordinateSet1.get(1).setRange([0, 0]);
jointCoordinateSet1.get(1).setName('Pelvis_ry');
jointCoordinateSet1.get(1).setDefaultValue(0);


jointCoordinateSet1.get(2).setRange([-pi, pi]);
jointCoordinateSet1.get(2).setName('Pelvis_rz');
jointCoordinateSet1.get(2).setDefaultValue(0);

jointCoordinateSet1.get(3).setRange([0, 10]);
jointCoordinateSet1.get(3).setName('Pelvis_px');
jointCoordinateSet1.get(3).setDefaultValue(0.9);

jointCoordinateSet1.get(4).setRange([0, 10]);
jointCoordinateSet1.get(4).setName('Pelvis_py');
jointCoordinateSet1.get(4).setDefaultValue(0);

jointCoordinateSet1.get(5).setRange([0, 0]);
jointCoordinateSet1.get(5).setName('Pelvis_pz');
jointCoordinateSet1.get(5).setDefaultValue(0);

The whole m file could be download in the below link
https://drive.google.com/open?id=0B4Av7 ... TlHb0pOVDA

I checked the API, it said the setLocked function is defined as

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setLocked (SimTK::State &s, bool aLocked) const

I wonder how could I get the State in matlab?

[jimmy d]

I wonder how could I get the State in matlab?

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state  = model.initSystem()

[Ibraheem Al-Dhamari]

I there a way to do this in cpp?

I tried something like

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        myJoint->getCoordinate().setLocked(state, true);  

the model is created but there is no lock. It works correctly in the visualizer but not in the gui interface as I have to lock the joint manually using the coordinates tab. Here is part of the code. The complete example can be found in this post
https://simtk.org/plugins/phpBB/viewt ... t=0&view=

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        Model pendulumDF;  // DF =Drag Force
        pendulumDF.setName("pendulumDF");
        pendulumDF.setGravity(SimTK::Vec3(0, gravity, 0));
        Ground& ground = pendulumDF.updGround();


         //                         body name, mass ,massCenter, inertia
        Body* rodBdy = new    Body("rod", rodMass,         rodCoM,     rodInertia );
        Cylinder rodGeom (rodRd , rodHeight);
        rodGeom.setColor(rodColor);    //set the color of the first block so they are different
        SimTK::Transform rodTrsfrm(SimTK::Vec3(0,0,0));
        auto* rodCenter = new PhysicalOffsetFrame("rodCenter", *rodBdy, rodTrsfrm);
        rodBdy->addComponent(rodCenter);     rodCenter->attachGeometry(rodGeom.clone());
        pendulumDF.addBody(rodBdy);

        // Connect the bodies with pin joints. Assume each body is 1 m long.
        auto* groundTrodJnt = new PinJoint("groundTrodJnt", pendulumDF.getGround(), Vec3(0),  Vec3(0),  *rodBdy, rodPos, rodOrient);
        pendulumDF.addJoint(groundTrodJnt);

        Body* sphBdy = new    Body("sph", sphMass,     sphCoM,     sphInertia );
        Sphere sphGeom (sphRd);
        sphGeom.setColor(sphColor); //set the color of the first block so they are different
        SimTK::Transform sphTrsfrm(SimTK::Vec3( 0, 0, 0));
        auto* sphCenter = new PhysicalOffsetFrame("sphCenter", *sphBdy, sphTrsfrm);
        sphBdy->addComponent(sphCenter);        sphCenter->attachGeometry(sphGeom.clone());
        pendulumDF.addBody(sphBdy);

        auto*  rodTsphJnt= new  PinJoint ("rodTsphJnt", *rodBdy,Vec3(0), Vec3(0),     *sphBdy, Vec3(0), Vec3(0));
        rodTsphJnt = new  PinJoint ("rodTsphJnt", *rodBdy, Vec3(sphX-rodHeight,sphY,0), rodOrient,     *sphBdy, sphPos, sphOrient);
        pendulumDF.addJoint(rodTsphJnt);

        pendulumDF.finalizeConnections();

        // Initialize the system and get the default state
        SimTK::State& si = pendulumDF.initSystem();

        rodTsphJnt->getCoordinate().setLocked(si, true);  // the sphere is fixed to rod
        
        pendulumDF.print(pendulumDF.getName()+".osim");

[Thomas Uchida]

The line

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rodTsphJnt->getCoordinate().setLocked(si, true);

modifies the state, which is not written to the model file. I think you want to set the default value of the "locked" property, which you can do with the setDefaultLocked() method: https://simtk.org/api_docs/opensim/api_ ... 9fa818c53a.

[Ibraheem Al-Dhamari]

Thanks for the info, I tried :

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       rodTsphJnt->getCoordinate().setDefaultLocked( true);

and I get

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BodyDragExampleComplete/pendulumDF.cpp:117: error: passing  const OpenSim::Coordinate as this argument discards qualifiers -fpermissive

I also tried

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         rodTsphJnt->getCoordinate().setDefaultLocked( true);

The code is compiled but there is no effect, the joints still unlocked when I load the model to the gui.

[Ayman Habib]

Hello,

Calling

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setDefaultLocked( true);

is the correct solution, however you need to use

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rodTsphJnt->updCoordinate();

so that you get a writable reference rather than a constant reference and the side effects are propagated.

Hope this helps,
-Ayman

[Ibraheem Al-Dhamari]

Thanks for your input. Still doesn't work

rodTsphJnt->getCoordinate() does not have setDefaultLocked function same error above


with this

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        Coordinate jntCord = rodTsphJnt->getCoordinate();
        jntCord.setDefaultLocked(true);
        rodTsphJnt->updCoordinate();

still the same effect. No lock in the model file or in the gui.

[Ibraheem Al-Dhamari]

A workaround is to add this to joint coordinate xml part

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							<locked>true</locked>

[Thomas Uchida]

I would try something like this:

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Coordinate& coord = rodTsphJnt->updCoordinate();
coord.setDefaultLocked(true);

[Ibraheem Al-Dhamari]

Thanks Thomas for the reply.

I would try something like this:

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Coordinate& coord = rodTsphJnt->updCoordinate();
coord.setDefaultLocked(true);

I don't see a difference, or am I missing something?

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        Coordinate jntCord = rodTsphJnt->getCoordinate();
        jntCord.setDefaultLocked(true);

with or without the third line rodTsphJnt->updCoordinate(); there is no effect.