functionDot.C

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#include "functionDot.H"
#include "rigidBodyModelState.H"
#include "addToRunTimeSelectionTable.H"

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
namespace RBD
{
namespace joints
{
    defineTypeNameAndDebug(functionDot, 0);

    addToRunTimeSelectionTable
    (
        joint,
        functionDot,
        dictionary
    );
}
}
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

Foam::RBD::joints::functionDot::functionDot
(
    const rigidBodyModel& model,
    const dictionary& dict
)
:
    joint(model, 0),
    f_(Function1<scalar>::New("function", dict)),
    delta_(dict.lookupOrDefault<scalar>("delta", rootSmall))
{}


Foam::autoPtr<Foam::RBD::joint> Foam::RBD::joints::functionDot::clone() const
{
    return autoPtr<joint>(new functionDot(*this));
}


// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //

Foam::RBD::joints::functionDot::~functionDot()
{}


// * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //

void Foam::RBD::joints::functionDot::jcalc
(
    joint::XSvc& J,
    const rigidBodyModelState& state
) const
{
    const label lambda = model_.lambda()[index_];
    const joint& parent = model_.joints()[lambda];

    spatialVector x(Zero), v(Zero), c(Zero);
    for(label i = 0; i < model_.joints()[lambda].nDoF(); ++ i)
    {
        const scalar qDot = state.qDot()[parent.qIndex() + i];
        const scalar qDdot = state.qDdot()[parent.qIndex() + i];
        const scalar qDddot = 0; // the third derivative is not stored

        const scalar f = f_->value(qDot);
        const scalar fMinusDf = f_->value(qDot - delta_/2);
        const scalar fPlusDf = f_->value(qDot + delta_/2);
        const scalar dfdqDot = (fPlusDf - fMinusDf)/delta_;
        const scalar d2fdqDot2 = (fPlusDf - 2*f + fMinusDf)/sqr(delta_);

        const spatialVector& s = parent.S()[i];

        x += f*s;
        v += dfdqDot*qDdot*s;
        c += (dfdqDot*qDddot + d2fdqDot2*sqr(qDdot))*s;
    }

    const scalar magW = mag(x.w());

    const tensor X(magW > vSmall ? quaternion(x.w(), magW).R() : tensor::I);

    J.X = spatialTransform(X, x.l());
    J.S = Zero;
    J.S1 = Zero;
    J.v = v;
    J.c = c;
}


// ************************************************************************* //