joint_state_listener.cpp

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/* Author: Wim Meeussen */

#include <kdl/tree.hpp>
#include <ros/ros.h>
#include "robot_state_publisher/robot_state_publisher.h"
#include "robot_state_publisher/joint_state_listener.h"
#include <kdl_parser/kdl_parser.hpp>


using namespace std;
using namespace ros;
using namespace KDL;
using namespace robot_state_publisher;


JointStateListener::JointStateListener(const KDL::Tree& tree)
  : state_publisher_(tree)
{
  ros::NodeHandle n_tilde("~");
  ros::NodeHandle n;

  // set publish frequency
  double publish_freq;
  n_tilde.param("publish_frequency", publish_freq, 50.0);
  publish_interval_ = ros::Duration(1.0/max(publish_freq,1.0));
  

  // subscribe to joint state
  joint_state_sub_ = n.subscribe("joint_states", 1, &JointStateListener::callbackJointState, this);

  // trigger to publish fixed joints
  timer_ = n_tilde.createTimer(publish_interval_, &JointStateListener::callbackFixedJoint, this);

};


JointStateListener::~JointStateListener()
{};


void JointStateListener::callbackFixedJoint(const ros::TimerEvent& e)
{
  state_publisher_.publishFixedTransforms();
}

void JointStateListener::callbackJointState(const JointStateConstPtr& state)
{
  if (state->name.size() != state->position.size()){
    ROS_ERROR("Robot state publisher received an invalid joint state vector");
    return;
  }

  // determine least recently published joint
  ros::Time last_published = ros::Time::now();
  for (unsigned int i=0; i<state->name.size(); i++)
  {
    ros::Time t = last_publish_time_[state->name[i]];
    last_published = (t < last_published) ? t : last_published;
  }
  // note: if a joint was seen for the first time,
  //       then last_published is zero.


  // check if we need to publish
  if (state->header.stamp >= last_published + publish_interval_){
    // get joint positions from state message
    map<string, double> joint_positions;
    for (unsigned int i=0; i<state->name.size(); i++)
      joint_positions.insert(make_pair(state->name[i], state->position[i]));
    state_publisher_.publishTransforms(joint_positions, state->header.stamp);

    // store publish time in joint map
    for (unsigned int i=0; i<state->name.size(); i++)
      last_publish_time_[state->name[i]] = state->header.stamp;
  }
}





// ----------------------------------
// ----- MAIN -----------------------
// ----------------------------------
int main(int argc, char** argv)
{
  // Initialize ros
  ros::init(argc, argv, "robot_state_publisher");
  NodeHandle node;

  // gets the location of the robot description on the parameter server
  KDL::Tree tree;
  if (!kdl_parser::treeFromParam("robot_description", tree)){
    ROS_ERROR("Failed to extract kdl tree from xml robot description");
    return -1;
  }

  JointStateListener state_publisher(tree);
  ros::spin();

  return 0;
}