kdl_kinematics_plugin.cpp

Go to the documentation of this file.

/*********************************************************************
 * Software License Agreement (BSD License)
 *
 *  Copyright (c) 2012, Willow Garage, Inc.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   * Neither the name of Willow Garage nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 *  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 *  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 *  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *********************************************************************/
 
/* Author: Sachin Chitta, David Lu!!, Ugo Cupcic */
 
#include <moveit/kdl_kinematics_plugin/kdl_kinematics_plugin.h>
#include <moveit/kdl_kinematics_plugin/chainiksolver_vel_mimic_svd.hpp>
 
#include <tf2_kdl/tf2_kdl.hpp>
// TODO: Remove conditional include when released to all active distros.
#if __has_include(<tf2/transform_datatypes.hpp>)
#include <tf2/transform_datatypes.hpp>
#else
#include <tf2/transform_datatypes.h>
#endif
 
#include <kdl_parser/kdl_parser.hpp>
#include <kdl/chainfksolverpos_recursive.hpp>
#include <kdl/frames_io.hpp>
#include <kdl/kinfam_io.hpp>
 
namespace kdl_kinematics_plugin
{
static rclcpp::Logger LOGGER = rclcpp::get_logger("moveit_kdl_kinematics_plugin.kdl_kinematics_plugin");
 
rclcpp::Clock KDLKinematicsPlugin::steady_clock_{ RCL_STEADY_TIME };
 
KDLKinematicsPlugin::KDLKinematicsPlugin() : initialized_(false)
{
}
 
void KDLKinematicsPlugin::getRandomConfiguration(Eigen::VectorXd& jnt_array) const
{
  state_->setToRandomPositions(joint_model_group_);
  state_->copyJointGroupPositions(joint_model_group_, &jnt_array[0]);
}
 
void KDLKinematicsPlugin::getRandomConfiguration(const Eigen::VectorXd& seed_state,
                                                 const std::vector<double>& consistency_limits,
                                                 Eigen::VectorXd& jnt_array) const
{
  joint_model_group_->getVariableRandomPositionsNearBy(state_->getRandomNumberGenerator(), &jnt_array[0],
                                                       &seed_state[0], consistency_limits);
}
 
bool KDLKinematicsPlugin::checkConsistency(const Eigen::VectorXd& seed_state,
                                           const std::vector<double>& consistency_limits,
                                           const Eigen::VectorXd& solution) const
{
  for (std::size_t i = 0; i < dimension_; ++i)
    if (fabs(seed_state(i) - solution(i)) > consistency_limits[i])
      return false;
  return true;
}
 
void KDLKinematicsPlugin::getJointWeights()
{
  const std::vector<std::string>& active_names = joint_model_group_->getActiveJointModelNames();
  std::vector<std::string> names;
  std::vector<double> weights;
  if (lookupParam(node_, "joint_weights.weights", weights, weights))
  {
    if (!lookupParam(node_, "joint_weights.names", names, names) || (names.size() != weights.size()))
    {
      RCLCPP_ERROR(LOGGER, "Expecting list parameter joint_weights.names of same size as list joint_weights.weights");
      // fall back to default weights
      weights.clear();
    }
  }
  else if (lookupParam(node_, "joint_weights", weights,
                       weights))  // try reading weight lists (for all active joints) directly
  {
    std::size_t num_active = active_names.size();
    if (weights.size() == num_active)
    {
      joint_weights_ = weights;
      return;
    }
    else if (!weights.empty())
    {
      RCLCPP_ERROR(LOGGER, "Expecting parameter joint_weights to list weights for all active joints (%zu) in order",
                   num_active);
      // fall back to default weights
      weights.clear();
    }
  }
 
  // by default assign weights of 1.0 to all joints
  joint_weights_ = std::vector<double>(active_names.size(), 1.0);
  if (weights.empty())  // indicates default case
    return;
 
  // modify weights of listed joints
  assert(names.size() == weights.size());
  for (size_t i = 0; i != names.size(); ++i)
  {
    auto it = std::find(active_names.begin(), active_names.end(), names[i]);
    if (it == active_names.cend())
      RCLCPP_WARN(LOGGER, "Joint '%s' is not an active joint in group '%s'", names[i].c_str(),
                  joint_model_group_->getName().c_str());
    else if (weights[i] < 0.0)
      RCLCPP_WARN(LOGGER, "Negative weight %f for joint '%s' will be ignored", weights[i], names[i].c_str());
    else
      joint_weights_[it - active_names.begin()] = weights[i];
  }
  RCLCPP_INFO_STREAM(
      LOGGER, "Joint weights for group '"
                  << getGroupName() << "': \n"
                  << Eigen::Map<const Eigen::VectorXd>(joint_weights_.data(), joint_weights_.size()).transpose());
}
 
bool KDLKinematicsPlugin::initialize(const rclcpp::Node::SharedPtr& node, const moveit::core::RobotModel& robot_model,
                                     const std::string& group_name, const std::string& base_frame,
                                     const std::vector<std::string>& tip_frames, double search_discretization)
{
  node_ = node;
  storeValues(robot_model, group_name, base_frame, tip_frames, search_discretization);
  joint_model_group_ = robot_model_->getJointModelGroup(group_name);
  if (!joint_model_group_)
    return false;
 
  if (!joint_model_group_->isChain())
  {
    RCLCPP_ERROR(LOGGER, "Group '%s' is not a chain", group_name.c_str());
    return false;
  }
  if (!joint_model_group_->isSingleDOFJoints())
  {
    RCLCPP_ERROR(LOGGER, "Group '%s' includes joints that have more than 1 DOF", group_name.c_str());
    return false;
  }
 
  KDL::Tree kdl_tree;
 
  if (!kdl_parser::treeFromUrdfModel(*robot_model.getURDF(), kdl_tree))
  {
    RCLCPP_ERROR(LOGGER, "Could not initialize tree object");
    return false;
  }
  if (!kdl_tree.getChain(base_frame_, getTipFrame(), kdl_chain_))
  {
    RCLCPP_ERROR(LOGGER, "Could not initialize chain object");
    return false;
  }
 
  dimension_ = joint_model_group_->getActiveJointModels().size() + joint_model_group_->getMimicJointModels().size();
  for (std::size_t i = 0; i < joint_model_group_->getJointModels().size(); ++i)
  {
    if (joint_model_group_->getJointModels()[i]->getType() == moveit::core::JointModel::REVOLUTE ||
        joint_model_group_->getJointModels()[i]->getType() == moveit::core::JointModel::PRISMATIC)
    {
      solver_info_.joint_names.push_back(joint_model_group_->getJointModelNames()[i]);
      const std::vector<moveit_msgs::msg::JointLimits>& jvec =
          joint_model_group_->getJointModels()[i]->getVariableBoundsMsg();
      solver_info_.limits.insert(solver_info_.limits.end(), jvec.begin(), jvec.end());
    }
  }
 
  if (!joint_model_group_->hasLinkModel(getTipFrame()))
  {
    RCLCPP_ERROR(LOGGER, "Could not find tip name in joint group '%s'", group_name.c_str());
    return false;
  }
  solver_info_.link_names.push_back(getTipFrame());
 
  joint_min_.resize(solver_info_.limits.size());
  joint_max_.resize(solver_info_.limits.size());
 
  for (unsigned int i = 0; i < solver_info_.limits.size(); ++i)
  {
    joint_min_(i) = solver_info_.limits[i].min_position;
    joint_max_(i) = solver_info_.limits[i].max_position;
  }
 
  // Get Solver Parameters
  lookupParam(node_, "max_solver_iterations", max_solver_iterations_, 500);
  lookupParam(node_, "epsilon", epsilon_, 1e-5);
  lookupParam(node_, "orientation_vs_position", orientation_vs_position_weight_, 1.0);
 
  bool position_ik;
  lookupParam(node_, "position_only_ik", position_ik, false);
  if (position_ik)  // position_only_ik overrules orientation_vs_position
    orientation_vs_position_weight_ = 0.0;
  if (orientation_vs_position_weight_ == 0.0)
    RCLCPP_INFO(LOGGER, "Using position only ik");
 
  getJointWeights();
 
  // Check for mimic joints
  unsigned int joint_counter = 0;
  for (std::size_t i = 0; i < kdl_chain_.getNrOfSegments(); ++i)
  {
    const moveit::core::JointModel* jm = robot_model_->getJointModel(kdl_chain_.segments[i].getJoint().getName());
 
    // first check whether it belongs to the set of active joints in the group
    if (jm->getMimic() == nullptr && jm->getVariableCount() > 0)
    {
      JointMimic mimic_joint;
      mimic_joint.reset(joint_counter);
      mimic_joint.joint_name = kdl_chain_.segments[i].getJoint().getName();
      mimic_joint.active = true;
      mimic_joints_.push_back(mimic_joint);
      ++joint_counter;
      continue;
    }
    if (joint_model_group_->hasJointModel(jm->getName()))
    {
      if (jm->getMimic() && joint_model_group_->hasJointModel(jm->getMimic()->getName()))
      {
        JointMimic mimic_joint;
        mimic_joint.joint_name = kdl_chain_.segments[i].getJoint().getName();
        mimic_joint.offset = jm->getMimicOffset();
        mimic_joint.multiplier = jm->getMimicFactor();
        mimic_joints_.push_back(mimic_joint);
        continue;
      }
    }
  }
  for (JointMimic& mimic_joint : mimic_joints_)
  {
    if (!mimic_joint.active)
    {
      const moveit::core::JointModel* joint_model =
          joint_model_group_->getJointModel(mimic_joint.joint_name)->getMimic();
      for (JointMimic& mimic_joint_recal : mimic_joints_)
      {
        if (mimic_joint_recal.joint_name == joint_model->getName())
        {
          mimic_joint.map_index = mimic_joint_recal.map_index;
        }
      }
    }
  }
 
  // Setup the joint state groups that we need
  state_ = std::make_shared<moveit::core::RobotState>(robot_model_);
 
  fk_solver_ = std::make_unique<KDL::ChainFkSolverPos_recursive>(kdl_chain_);
 
  initialized_ = true;
  RCLCPP_DEBUG(LOGGER, "KDL solver initialized");
  return true;
}
 
bool KDLKinematicsPlugin::timedOut(const rclcpp::Time& start_time, double duration) const
{
  return ((steady_clock_.now() - start_time).seconds() >= duration);
}
 
bool KDLKinematicsPlugin::getPositionIK(const geometry_msgs::msg::Pose& ik_pose,
                                        const std::vector<double>& ik_seed_state, std::vector<double>& solution,
                                        moveit_msgs::msg::MoveItErrorCodes& error_code,
                                        const kinematics::KinematicsQueryOptions& options) const
{
  std::vector<double> consistency_limits;
 
  // limit search to a single attempt by setting a timeout of zero
  return searchPositionIK(ik_pose, ik_seed_state, 0.0, consistency_limits, solution, IKCallbackFn(), error_code,
                          options);
}
 
bool KDLKinematicsPlugin::searchPositionIK(const geometry_msgs::msg::Pose& ik_pose,
                                           const std::vector<double>& ik_seed_state, double timeout,
                                           std::vector<double>& solution,
                                           moveit_msgs::msg::MoveItErrorCodes& error_code,
                                           const kinematics::KinematicsQueryOptions& options) const
{
  std::vector<double> consistency_limits;
 
  return searchPositionIK(ik_pose, ik_seed_state, timeout, consistency_limits, solution, IKCallbackFn(), error_code,
                          options);
}
 
bool KDLKinematicsPlugin::searchPositionIK(const geometry_msgs::msg::Pose& ik_pose,
                                           const std::vector<double>& ik_seed_state, double timeout,
                                           const std::vector<double>& consistency_limits, std::vector<double>& solution,
                                           moveit_msgs::msg::MoveItErrorCodes& error_code,
                                           const kinematics::KinematicsQueryOptions& options) const
{
  return searchPositionIK(ik_pose, ik_seed_state, timeout, consistency_limits, solution, IKCallbackFn(), error_code,
                          options);
}
 
bool KDLKinematicsPlugin::searchPositionIK(const geometry_msgs::msg::Pose& ik_pose,
                                           const std::vector<double>& ik_seed_state, double timeout,
                                           std::vector<double>& solution, const IKCallbackFn& solution_callback,
                                           moveit_msgs::msg::MoveItErrorCodes& error_code,
                                           const kinematics::KinematicsQueryOptions& options) const
{
  std::vector<double> consistency_limits;
  return searchPositionIK(ik_pose, ik_seed_state, timeout, consistency_limits, solution, solution_callback, error_code,
                          options);
}
 
bool KDLKinematicsPlugin::searchPositionIK(const geometry_msgs::msg::Pose& ik_pose,
                                           const std::vector<double>& ik_seed_state, double timeout,
                                           const std::vector<double>& consistency_limits, std::vector<double>& solution,
                                           const IKCallbackFn& solution_callback,
                                           moveit_msgs::msg::MoveItErrorCodes& error_code,
                                           const kinematics::KinematicsQueryOptions& options) const
{
  const rclcpp::Time start_time = steady_clock_.now();
  if (!initialized_)
  {
    RCLCPP_ERROR(LOGGER, "kinematics solver not initialized");
    error_code.val = error_code.NO_IK_SOLUTION;
    return false;
  }
 
  if (ik_seed_state.size() != dimension_)
  {
    RCLCPP_ERROR(LOGGER, "Seed state must have size %d instead of size %zu\n", dimension_, ik_seed_state.size());
    error_code.val = error_code.NO_IK_SOLUTION;
    return false;
  }
 
  // Resize consistency limits to remove mimic joints
  std::vector<double> consistency_limits_mimic;
  if (!consistency_limits.empty())
  {
    if (consistency_limits.size() != dimension_)
    {
      RCLCPP_ERROR(LOGGER, "Consistency limits must be empty or have size %d instead of size %zu\n", dimension_,
                   consistency_limits.size());
      error_code.val = error_code.NO_IK_SOLUTION;
      return false;
    }
 
    for (std::size_t i = 0; i < dimension_; ++i)
    {
      if (mimic_joints_[i].active)
        consistency_limits_mimic.push_back(consistency_limits[i]);
    }
  }
  Eigen::Matrix<double, 6, 1> cartesian_weights;
  cartesian_weights.topRows<3>().setConstant(1.0);
  cartesian_weights.bottomRows<3>().setConstant(orientation_vs_position_weight_);
 
  KDL::JntArray jnt_seed_state(dimension_);
  KDL::JntArray jnt_pos_in(dimension_);
  KDL::JntArray jnt_pos_out(dimension_);
  jnt_seed_state.data = Eigen::Map<const Eigen::VectorXd>(ik_seed_state.data(), ik_seed_state.size());
  jnt_pos_in = jnt_seed_state;
 
  KDL::ChainIkSolverVelMimicSVD ik_solver_vel(kdl_chain_, mimic_joints_, orientation_vs_position_weight_ == 0.0);
  solution.resize(dimension_);
 
  KDL::Frame pose_desired;
  tf2::fromMsg(ik_pose, pose_desired);
 
  RCLCPP_DEBUG_STREAM(LOGGER, "searchPositionIK: Position request pose is "
                                  << ik_pose.position.x << " " << ik_pose.position.y << " " << ik_pose.position.z << " "
                                  << ik_pose.orientation.x << " " << ik_pose.orientation.y << " "
                                  << ik_pose.orientation.z << " " << ik_pose.orientation.w);
 
  unsigned int attempt = 0;
  do
  {
    ++attempt;
    if (attempt > 1)  // randomly re-seed after first attempt
    {
      if (!consistency_limits_mimic.empty())
        getRandomConfiguration(jnt_seed_state.data, consistency_limits_mimic, jnt_pos_in.data);
      else
        getRandomConfiguration(jnt_pos_in.data);
      RCLCPP_DEBUG_STREAM(LOGGER, "New random configuration (" << attempt << "): " << jnt_pos_in);
    }
 
    int ik_valid =
        CartToJnt(ik_solver_vel, jnt_pos_in, pose_desired, jnt_pos_out, max_solver_iterations_,
                  Eigen::Map<const Eigen::VectorXd>(joint_weights_.data(), joint_weights_.size()), cartesian_weights);
    if (ik_valid == 0 || options.return_approximate_solution)  // found acceptable solution
    {
      if (!consistency_limits_mimic.empty() &&
          !checkConsistency(jnt_seed_state.data, consistency_limits_mimic, jnt_pos_out.data))
        continue;
 
      Eigen::Map<Eigen::VectorXd>(solution.data(), solution.size()) = jnt_pos_out.data;
      if (solution_callback)
      {
        solution_callback(ik_pose, solution, error_code);
        if (error_code.val != error_code.SUCCESS)
          continue;
      }
 
      // solution passed consistency check and solution callback
      error_code.val = error_code.SUCCESS;
      RCLCPP_DEBUG_STREAM(LOGGER, "Solved after " << (steady_clock_.now() - start_time).seconds() << " < " << timeout
                                                  << "s and " << attempt << " attempts");
      return true;
    }
  } while (!timedOut(start_time, timeout));
 
  RCLCPP_DEBUG_STREAM(LOGGER, "IK timed out after " << (steady_clock_.now() - start_time).seconds() << " > " << timeout
                                                    << "s and " << attempt << " attempts");
  error_code.val = error_code.TIMED_OUT;
  return false;
}
 
// NOLINTNEXTLINE(readability-identifier-naming)
int KDLKinematicsPlugin::CartToJnt(KDL::ChainIkSolverVelMimicSVD& ik_solver, const KDL::JntArray& q_init,
                                   const KDL::Frame& p_in, KDL::JntArray& q_out, const unsigned int max_iter,
                                   const Eigen::VectorXd& joint_weights, const Twist& cartesian_weights) const
{
  double last_delta_twist_norm = DBL_MAX;
  double step_size = 1.0;
  KDL::Frame f;
  KDL::Twist delta_twist;
  KDL::JntArray delta_q(q_out.rows()), q_backup(q_out.rows());
  Eigen::ArrayXd extra_joint_weights(joint_weights.rows());
  extra_joint_weights.setOnes();
 
  q_out = q_init;
  RCLCPP_DEBUG_STREAM(LOGGER, "Input: " << q_init);
 
  unsigned int i;
  bool success = false;
  for (i = 0; i < max_iter; ++i)
  {
    fk_solver_->JntToCart(q_out, f);
    delta_twist = diff(f, p_in);
    RCLCPP_DEBUG_STREAM(LOGGER, "[" << std::setw(3) << i << "] delta_twist: " << delta_twist);
 
    // check norms of position and orientation errors
    const double position_error = delta_twist.vel.Norm();
    const double orientation_error = ik_solver.isPositionOnly() ? 0 : delta_twist.rot.Norm();
    const double delta_twist_norm = std::max(position_error, orientation_error);
    if (delta_twist_norm <= epsilon_)
    {
      success = true;
      break;
    }
 
    if (delta_twist_norm >= last_delta_twist_norm)
    {
      // if the error increased, we are close to a singularity -> reduce step size
      double old_step_size = step_size;
      step_size *= std::min(0.2, last_delta_twist_norm / delta_twist_norm);  // reduce scale;
      KDL::Multiply(delta_q, step_size / old_step_size, delta_q);
      RCLCPP_DEBUG(LOGGER, "      error increased: %f -> %f, scale: %f", last_delta_twist_norm, delta_twist_norm,
                   step_size);
      q_out = q_backup;  // restore previous unclipped joint values
    }
    else
    {
      q_backup = q_out;  // remember joint values of last successful step
      step_size = 1.0;   // reset step size
      last_delta_twist_norm = delta_twist_norm;
 
      ik_solver.CartToJnt(q_out, delta_twist, delta_q, extra_joint_weights * joint_weights.array(), cartesian_weights);
    }
 
    clipToJointLimits(q_out, delta_q, extra_joint_weights);
 
    const double delta_q_norm = delta_q.data.lpNorm<1>();
    RCLCPP_DEBUG(LOGGER, "[%3d] pos err: %f  rot err: %f  delta_q: %f", i, position_error, orientation_error,
                 delta_q_norm);
    if (delta_q_norm < epsilon_)  // stuck in singularity
    {
      if (step_size < epsilon_)  // cannot reach target
        break;
      // wiggle joints
      last_delta_twist_norm = DBL_MAX;
      delta_q.data.setRandom();
      delta_q.data *= std::min(0.1, delta_twist_norm);
      clipToJointLimits(q_out, delta_q, extra_joint_weights);
      extra_joint_weights.setOnes();
    }
 
    KDL::Add(q_out, delta_q, q_out);
 
    RCLCPP_DEBUG_STREAM(LOGGER, "      delta_q: " << delta_q);
    RCLCPP_DEBUG_STREAM(LOGGER, "      q: " << q_out);
  }
 
  int result = (i == max_iter) ? -3 : (success ? 0 : -2);
  RCLCPP_DEBUG_STREAM(LOGGER, "Result " << result << " after " << i << " iterations: " << q_out);
 
  return result;
}
 
void KDLKinematicsPlugin::clipToJointLimits(const KDL::JntArray& q, KDL::JntArray& q_delta,
                                            Eigen::ArrayXd& weighting) const
{
  weighting.setOnes();
  for (std::size_t i = 0; i < q.rows(); ++i)
  {
    const double delta_max = joint_max_(i) - q(i);
    const double delta_min = joint_min_(i) - q(i);
    if (q_delta(i) > delta_max)
      q_delta(i) = delta_max;
    else if (q_delta(i) < delta_min)
      q_delta(i) = delta_min;
    else
      continue;
 
    weighting[mimic_joints_[i].map_index] = 0.01;
  }
}
 
bool KDLKinematicsPlugin::getPositionFK(const std::vector<std::string>& link_names,
                                        const std::vector<double>& joint_angles,
                                        std::vector<geometry_msgs::msg::Pose>& poses) const
{
  if (!initialized_)
  {
    RCLCPP_ERROR(LOGGER, "kinematics solver not initialized");
    return false;
  }
  poses.resize(link_names.size());
  if (joint_angles.size() != dimension_)
  {
    RCLCPP_ERROR(LOGGER, "Joint angles vector must have size: %d", dimension_);
    return false;
  }
 
  KDL::Frame p_out;
  KDL::JntArray jnt_pos_in(dimension_);
  jnt_pos_in.data = Eigen::Map<const Eigen::VectorXd>(joint_angles.data(), joint_angles.size());
 
  bool valid = true;
  for (unsigned int i = 0; i < poses.size(); ++i)
  {
    if (fk_solver_->JntToCart(jnt_pos_in, p_out) >= 0)
    {
      poses[i] = tf2::toMsg(p_out);
    }
    else
    {
      RCLCPP_ERROR(LOGGER, "Could not compute FK for %s", link_names[i].c_str());
      valid = false;
    }
  }
  return valid;
}
 
const std::vector<std::string>& KDLKinematicsPlugin::getJointNames() const
{
  return solver_info_.joint_names;
}
 
const std::vector<std::string>& KDLKinematicsPlugin::getLinkNames() const
{
  return solver_info_.link_names;
}
 
}  // namespace kdl_kinematics_plugin
 
// register KDLKinematics as a KinematicsBase implementation
#include <class_loader/class_loader.hpp>
CLASS_LOADER_REGISTER_CLASS(kdl_kinematics_plugin::KDLKinematicsPlugin, kinematics::KinematicsBase)