double_integrator_dynamics_solver.cpp

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//
// Copyright (c) 2019, Wolfgang Merkt
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#include <exotica_double_integrator_dynamics_solver/double_integrator_dynamics_solver.h>

REGISTER_DYNAMICS_SOLVER_TYPE("DoubleIntegratorDynamicsSolver", exotica::DoubleIntegratorDynamicsSolver)

namespace exotica
{
void DoubleIntegratorDynamicsSolver::AssignScene(ScenePtr scene_in)
{
    const int num_positions_in = scene_in->GetKinematicTree().GetNumControlledJoints();
    if (debug_) HIGHLIGHT_NAMED("DoubleIntegratorDynamicsSolver::AssignScene", "Dimension: " << num_positions_in);

    num_positions_ = num_positions_in;
    num_velocities_ = num_positions_in;
    num_controls_ = num_positions_in;

    // Cf. https://en.wikipedia.org/wiki/Double_integrator
    A_ = Eigen::MatrixXd::Zero(num_positions_ + num_velocities_, num_positions_ + num_velocities_);
    A_.topRightCorner(num_velocities_, num_velocities_) = Eigen::MatrixXd::Identity(num_velocities_, num_velocities_);

    B_ = Eigen::MatrixXd::Zero(num_positions_ + num_velocities_, num_controls_);
    B_.bottomRightCorner(num_controls_, num_controls_) = Eigen::MatrixXd::Identity(num_controls_, num_controls_);

    fx_ = A_;
    fu_ = B_;

    // Set up state transition derivative
    DynamicsSolver::ComputeDerivatives(Eigen::VectorXd(num_positions_ + num_velocities_), Eigen::VectorXd(num_controls_));
}

Eigen::VectorXd DoubleIntegratorDynamicsSolver::f(const StateVector& x, const ControlVector& u)
{
    return A_ * x + B_ * u;
}

void DoubleIntegratorDynamicsSolver::ComputeDerivatives(const StateVector& x, const ControlVector& u)
{
    // If the integrator changed, set up state transition derivatives again:
    if (integrator_ != last_integrator_)
    {
        DynamicsSolver::ComputeDerivatives(x, u);
        last_integrator_ = integrator_;
    }
}

Eigen::MatrixXd DoubleIntegratorDynamicsSolver::fx(const StateVector& x, const ControlVector& u)
{
    return A_;
}

Eigen::MatrixXd DoubleIntegratorDynamicsSolver::fu(const StateVector& x, const ControlVector& u)
{
    return B_;
}

}  // namespace exotica