ROS学习笔记（六）ROS TF初探

 StampedTransform函数参数定义

  ros::Time stamp_; ///< The timestamp associated with this transform
  std::string frame_id_; ///< The frame_id of the coordinate frame  in which this transform is defined
  std::string child_frame_id_; ///< The frame_id of the coordinate frame this transform defines
  StampedTransform(const tf::Transform& input, const ros::Time& timestamp, const std::string & frame_id, const std::string & child_frame_id):
    tf::Transform (input), stamp_ ( timestamp ), frame_id_ (frame_id), child_frame_id_(child_frame_id){ }

 transformPoint函数参数定义

  /** \brief Transform a Stamped Point Message into the target frame 
   * This can throw all that lookupTransform can throw as well as tf::InvalidTransform */
  void transformPoint(const std::string& target_frame, const geometry_msgs::PointStamped& stamped_in, geometry_msgs::PointStamped& stamped_out) const;

参数收发的小例子： 

tf_broadcaster.cpp

#include <ros/ros.h>
#include <tf/transform_broadcaster.h>
 
int main(int argc, char** argv) {
  ros::init(argc, argv, "robot_tf_publisher");
  ros::NodeHandle n;
 
  ros::Rate r(100);
 
  tf::TransformBroadcaster broadcaster;
 
  while (n.ok()) {
    tf::Transform transform;  //这里transform为一个类
    tf::Quaternion q;         // Quaternion是一个类
    q.setRPY(0.0, 0.0, 0.0);
    // setRPY是类Quaternion的一个成员函数  rpy 转换为四元数
 
    transform.setRotation(q);
    transform.setOrigin(tf::Vector3(0.1, 0.0, 0.2));
 
    broadcaster.sendTransform(tf::StampedTransform(transform, ros::Time::now(),
                                                   "base_link", "base_laser"));
    r.sleep();
  }
}

tf_listener.cpp

#include <geometry_msgs/PointStamped.h>
#include <ros/ros.h>
#include <tf/transform_listener.h>
 
void transformPoint(const tf::TransformListener& listener) {
  // we'll create a point in the base_laser frame that we'd like to transform to
  // the base_link frame
  geometry_msgs::PointStamped laser_point;
  laser_point.header.frame_id = "base_laser";
 
  // we'll just use the most recent transform available for our simple example
  laser_point.header.stamp = ros::Time();
 
  // just an arbitrary point in space
  static int x = 1;
  laser_point.point.x = x++;
  laser_point.point.y = 0.2;
  laser_point.point.z = 0.0;
 
  try {
    geometry_msgs::PointStamped base_point;
    listener.transformPoint("base_link", laser_point, base_point);
 
    ROS_INFO(
        "base_laser: (%.2f, %.2f. %.2f) -----> base_link: (%.2f, %.2f, %.2f) "
        "at time %.2f",
        laser_point.point.x, laser_point.point.y, laser_point.point.z,
        base_point.point.x, base_point.point.y, base_point.point.z,
        base_point.header.stamp.toSec());
  } catch (tf::TransformException& ex) {
    ROS_ERROR(
        "Received an exception trying to transform a point from \"base_laser\" "
        "to \"base_link\": %s",
        ex.what());
  }
}
 
int main(int argc, char** argv) {
  ros::init(argc, argv, "robot_tf_listener");
  ros::NodeHandle n;
 
  tf::TransformListener listener(ros::Duration(10));
 
  // we'll transform a point once every second
  ros::Timer timer = n.createTimer(
      ros::Duration(1.0), boost::bind(&transformPoint, boost::ref(listener)));
 
  ros::spin();
}