CKinematicChain.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/opengl/CSetOfObjects.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/serialization/CSerializable.h>
#include <vector>

namespace mrpt
{
namespace kinematics
{
/** An individual kinematic chain element (one link) which builds up a
 * CKinematicChain.
 * The parameterization of the SE(3) transformation from the starting point to
 * the end point
 * follows a Denavit-Hartenberg standard parameterization: [theta, d, a,
 * alpha].
 */
struct TKinematicLink
{
    /** Rotation from X_i to X_{i+1} (radians) */
    double theta{0};
    /** Distance along Z_i to the common normal between Z_i and Z_{i+1} */
    double d{0};
    /** Distance along the common normal (in the same direction than the new
     * X_{i+1}) */
    double a{0};
    /** Rotation along X_{i+1} to transform Z_i into Z_{i+1} */
    double alpha{0};

    /** "false": Is revolute ("q_i" is "theta"), "true": is prismatic ("q_i" is
     * "d") */
    bool is_prismatic{false};

    TKinematicLink(
        double _theta, double _d, double _a, double _alpha, bool _is_prismatic)
        : theta(_theta),
          d(_d),
          a(_a),
          alpha(_alpha),
          is_prismatic(_is_prismatic)
    {
    }
    TKinematicLink() = default;
};

mrpt::serialization::CArchive& operator>>(
    mrpt::serialization::CArchive& in, TKinematicLink& o);
mrpt::serialization::CArchive& operator<<(
    mrpt::serialization::CArchive& out, const TKinematicLink& o);

/** A open-loop kinematic chain model, suitable to robotic manipulators.
 *  Each link is parameterized with standard Denavit-Hartenberg standard
 * parameterization [theta, d, a, alpha].
 *
 *  The orientation of the first link can be modified with setOriginPose(),
 * which defaults to standard XYZ axes with +Z pointing upwards.
 *
 * \sa CPose3D
 * \ingroup kinematics_grp
 */
class CKinematicChain : public mrpt::serialization::CSerializable
{
    DEFINE_SERIALIZABLE(CKinematicChain, mrpt::kinematics)

   private:
    /** Smart pointers to the last objects for each link, as returned in
     * getAs3DObject(), for usage within update3DObject() */
    mutable std::vector<mrpt::opengl::CRenderizable::Ptr> m_last_gl_objects;

    /** The links of this robot arm */
    std::vector<TKinematicLink> m_links;
    /** The pose of the first link. */
    mrpt::poses::CPose3D m_origin;

   public:
    /** Return the number of links */
    size_t size() const { return m_links.size(); }
    /** Erases all links and leave the robot arm empty. */
    void clear();

    /** Appends a new link to the robotic arm, with the given Denavit-Hartenberg
     * parameters (see TKinematicLink for further details) */
    void addLink(
        double theta, double d, double a, double alpha, bool is_prismatic);

    /** Removes one link from the kinematic chain (0<=idx<N) */
    void removeLink(const size_t idx);

    /** Get a ref to a given link (read-only) */
    const TKinematicLink& getLink(const size_t idx) const;

    /** Get a ref to a given link (read-write) */
    TKinematicLink& getLinkRef(const size_t idx);

    /** Can be used to define a first degree of freedom along a +Z axis which
     * does not coincide with the global +Z axis. */
    void setOriginPose(const mrpt::poses::CPose3D& new_pose);

    /** Returns the current pose of the first link. */
    const mrpt::poses::CPose3D& getOriginPose() const;

    /** Get all the DOFs of the arm at once, returning them in a vector with all
     * the "q_i" values, which
     * can be interpreted as rotations (radians) or displacements (meters)
     * depending on links being "revolute" or "prismatic".
     * The vector is automatically resized to the correct size (the number of
     * links).
     * \tparam VECTOR Can be any Eigen vector, mrpt::math::CVectorDouble, or
     * std::vector<double>
     */
    template <class VECTOR>
    void getConfiguration(VECTOR& v) const
    {
        const size_t N = m_links.size();
        v.resize(N);
        for (size_t i = 0; i < N; i++)
        {
            if (m_links[i].is_prismatic)
                v[i] = m_links[i].d;
            else
                v[i] = m_links[i].theta;
        }
    }

    /** Set all the DOFs of the arm at once, from a vector with all the "q_i"
     * values, which
     * are interpreted as rotations (radians) or displacements (meters)
     * depending on links being "revolute" or "prismatic".
     * \exception std::exception If the size of the vector doesn't match the
     * number of links.
     * \tparam VECTOR Can be any Eigen vector, mrpt::math::CVectorDouble, or
     * std::vector<double>
     */
    template <class VECTOR>
    void setConfiguration(const VECTOR& v)
    {
        ASSERT_EQUAL_(v.size(), this->size());
        const size_t N = m_links.size();
        for (size_t i = 0; i < N; i++)
        {
            if (m_links[i].is_prismatic)
                m_links[i].d = v[i];
            else
                m_links[i].theta = v[i];
        }
    }

    /** Constructs a 3D representation of the kinematic chain, in its current
     * state.
     * You can call update3DObject() to update the kinematic state of these
     * OpenGL objects in the future, since
     * an internal list of smart pointers to the constructed objects is kept
     * internally. This is more efficient
     * than calling this method again to build a new representation.
     * \param[out] out_all_poses Optional output vector, will contain the poses
     * in the format of recomputeAllPoses()
     * \sa update3DObject
     */
    void getAs3DObject(
        mrpt::opengl::CSetOfObjects::Ptr& inout_gl_obj,
        std::vector<mrpt::poses::CPose3D>* out_all_poses = nullptr) const;

    /** Read getAs3DObject() for a description.
     * \param[out] out_all_poses Optional output vector, will contain the poses
     * in the format of recomputeAllPoses()
     */
    void update3DObject(
        std::vector<mrpt::poses::CPose3D>* out_all_poses = nullptr) const;

    /** Go thru all the links of the chain and compute the global pose of each
     * link. The "ground" link pose "pose0" defaults to the origin of
     * coordinates,
     * but anything else can be passed as the optional argument.
     * The returned vector has N+1 elements (N=number of links), since [0]
     * contains the base frame, [1] the pose after the first link, and so on.
     */
    void recomputeAllPoses(
        std::vector<mrpt::poses::CPose3D>& poses,
        const mrpt::poses::CPose3D& pose0 = mrpt::poses::CPose3D()) const;

};  // End of class def.

}  // namespace kinematics

// Specialization must occur in the same namespace
// (This is to ease serialization)
namespace typemeta
{
MRPT_DECLARE_TTYPENAME_NAMESPACE(TKinematicLink, ::mrpt::kinematics)
}  // namespace typemeta

}  // namespace mrpt