TF坐标变换

一、什么是TF

 二、TF使用方法

三、TF包内的指令工具

四、相关API

1、广播变换
发布坐标之间的坐标关系

#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();

  tf::TransformBroadcaster broadcaster;

  while(n.ok()){

//发布坐标变换
    broadcaster.sendTransform(tf::StampedTransform(tf::Transform(
                            tf::Quaternion(, , , ), //四元数
                            tf::Vector3(-0.25, 0.0, 0.0)),
                            ros::Time::now(),
                            "base_link",
                            "laser"));
    r.sleep();
  }
}

2、使用变换

通过监听到上面发布的坐标变换，把坐标中的一个点变换到另一个坐标中的坐标

#include <ros/ros.h>
#include <geometry_msgs/PointStamped.h>
#include <tf/transform_listener.h>

//我们将创建一个函数，给定一个TransformListener，在“base_laser”坐标系中取一点，并将其转换为“base_link”坐标系。
// 这个函数将作为在我们程序的main()中创建的ros::Timer的回调，并且每秒都会触发。
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();//时间戳

  //just an arbitrary point in space
  laser_point.point.x = 1.0;
  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);//坐标中的点的位置变换

    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;

//我们需要创建一个tf::TransformListener。一个TransformListener对象自动订阅了ROS变换消息主题和管理所有将在网络中广播的变换数据。
  tf::TransformListener listener(ros::Duration());

  //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();

}

wiki.ros.org/tf/Overview

http://wiki.ros.org/cn/tf/Tutorials

https://www.ncnynl.com/archives/201708/1881.html