从ros parameter server 获取URDF

// get the general robot description, the lwr class will take care of parsing what’s useful to itself
std::string urdf_string = getURDF(lwr_nh, “/robot_description”);

// Get the URDF XML from the parameter server
std::string getURDF(ros::NodeHandle &model_nh_, std::string param_name)
{
  std::string urdf_string;
  std::string robot_description = "/robot_description";

  // search and wait for robot_description on param server
  while (urdf_string.empty())
  {
    std::string search_param_name;
    if (model_nh_.searchParam(param_name, search_param_name))
    {
      ROS_INFO_ONCE_NAMED("LWRHWFRIL", "LWRHWFRIL node is waiting for model"
        " URDF in parameter [%s] on the ROS param server.", search_param_name.c_str());

      model_nh_.getParam(search_param_name, urdf_string);
    }
    else
    {
      ROS_INFO_ONCE_NAMED("LWRHWFRIL", "LWRHWFRIL node is waiting for model"
        " URDF in parameter [%s] on the ROS param server.", robot_description.c_str());

      model_nh_.getParam(param_name, urdf_string);
    }

    usleep(100000);
  }
  ROS_DEBUG_STREAM_NAMED("LWRHWFRIL", "Recieved urdf from param server, parsing...");

  return urdf_string;
}

参考：
[1] https://github.com/epfl-lasa/kuka-lwr-ros