joint_state_listener.cpp

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/* Author: Wim Meeussen */

#include <ros/ros.h>
#include <urdf/model.h>
#include <kdl/tree.hpp>
#include <kdl_parser/kdl_parser.hpp>

#include "robot_state_publisher/robot_state_publisher.h"
#include "robot_state_publisher/joint_state_listener.h"

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

JointStateListener::JointStateListener(const KDL::Tree& tree, const MimicMap& m, const urdf::Model& model)
  : state_publisher_(tree, model), mimic_(m)
{
  ros::NodeHandle n_tilde("~");
  ros::NodeHandle n;

  // set publish frequency
  double publish_freq;
  n_tilde.param("publish_frequency", publish_freq, 50.0);
  // set whether to use the /tf_static latched static transform broadcaster
  n_tilde.param("use_tf_static", use_tf_static_, false);
  // get the tf_prefix parameter from the closest namespace
  std::string tf_prefix_key;
  n_tilde.searchParam("tf_prefix", tf_prefix_key);
  n_tilde.param(tf_prefix_key, tf_prefix_, std::string(""));
  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
  // if using static transform broadcaster, this will be a oneshot trigger and only run once
  timer_ = n_tilde.createTimer(publish_interval_, &JointStateListener::callbackFixedJoint, this, use_tf_static_);
}


JointStateListener::~JointStateListener()
{}


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

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;
  }

  // check if we moved backwards in time (e.g. when playing a bag file)
  ros::Time now = ros::Time::now();
  if (last_callback_time_ > now) {
    // force re-publish of joint transforms
    ROS_WARN("Moved backwards in time (probably because ROS clock was reset), re-publishing joint transforms!");
    last_publish_time_.clear();
  }
  last_callback_time_ = now;

  // determine least recently published joint
  ros::Time last_published = 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]));
    }

    for (MimicMap::iterator i = mimic_.begin(); i != mimic_.end(); i++) {
      if(joint_positions.find(i->second->joint_name) != joint_positions.end()) {
        double pos = joint_positions[i->second->joint_name] * i->second->multiplier + i->second->offset;
        joint_positions.insert(make_pair(i->first, pos));
      }
    }

    state_publisher_.publishTransforms(joint_positions, state->header.stamp, tf_prefix_);

    // 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;

  std::string exe_name = argv[0];
  std::size_t slash = exe_name.find_last_of("/");
  if (slash != std::string::npos) {
    exe_name = exe_name.substr(slash + 1);
  }
  if (exe_name == "state_publisher") {
    ROS_WARN("The 'state_publisher' executable is deprecated. Please use 'robot_state_publisher' instead");
  }

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

  MimicMap mimic;

  for (std::map< std::string, boost::shared_ptr< urdf::Joint > >::iterator i = model.joints_.begin(); i != model.joints_.end(); i++) {
    if (i->second->mimic) {
      mimic.insert(make_pair(i->first, i->second->mimic));
    }
  }

  JointStateListener state_publisher(tree, mimic, model);
  ros::spin();

  return 0;
}