joint_state_listener.cpp

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/* Author: Wim Meeussen */

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

using namespace std;
using namespace ros;
using namespace KDL;
using namespace robot_state_chain_publisher;


JointStateListener::JointStateListener(const KDL::Tree& tree)
  : n_tilde_("~"), state_publisher_(tree)
{
  // set publish frequency
  double publish_freq, min_publish_freq;
  n_tilde_.param("publish_frequency", publish_freq, 50.0);
  n_tilde_.param("min_publish_frequency", min_publish_freq, 1.0);
  publish_delay_ = Duration(1/publish_freq);
  max_publish_delay_ = Duration(1/min_publish_freq);
  //Time::waitForValid(); // new method which was introduced later?
  last_publish_time_ = Time::now();
  // subscribe to mechanism state
  joint_state_sub_ = n_.subscribe("joint_states", 10, &JointStateListener::callbackJointState, this);

  timer_ = n_tilde_.createTimer(max_publish_delay_, &JointStateListener::timerCallback, this);
};


JointStateListener::~JointStateListener()
{};


void JointStateListener::timerCallback(const ros::TimerEvent& e)
{
  Time now = Time::now();
  if( now >= last_publish_time_ + max_publish_delay_*0.9 )
  {
    // time to publish something, with or without joint states
    state_publisher_.publishTransforms(joint_positions, now, (now - max_publish_delay_));

    if( last_publish_time_ - now > max_publish_delay_*2 || last_publish_time_ - now < max_publish_delay_*2)
      last_publish_time_ = now;
    else
      last_publish_time_ += max_publish_delay_;
  }
}

void JointStateListener::callbackJointState(const JointStateConstPtr& state)
{
  if (state->name.size() == 0){
    ROS_ERROR("Robot state publisher received an empty joint state vector");
    return;
  }

  if (state->name.size() != state->position.size()){
    ROS_ERROR("Robot state publisher received an invalid joint state vector");
    return;
  }

  // early-simtime bug - if we compute a negative time, ros throws an exception
  if(last_publish_time_.toSec() <= max_publish_delay_.toSec()) {
    last_publish_time_ = Time::now();
    return;
  }

  // get joint positions from state message
  for (unsigned int i=0; i<state->name.size(); i++) {
    RobotStatePublisher::JointState s;
    s.pos = state->position[i];
    s.time = state->header.stamp;
    s.published = false;
    joint_positions[state->name[i]] = s;

  }

  Time now = Time::now();
  if( now >= last_publish_time_ + publish_delay_ )
  {
    state_publisher_.publishTransforms(joint_positions, now, (now - max_publish_delay_));

    if( last_publish_time_ - now > publish_delay_*2 || last_publish_time_ - now < publish_delay_*2)
      last_publish_time_ = now;
    else
      last_publish_time_ += publish_delay_;
  }
}