目錄

• 創建功能包
• 如何實現一個tf廣播器
• • 創建tf廣播器代碼（C++）
• 如何實現一個tf監聽器
• • 創建tf監聽器代碼（C++）
• 配置編譯規則
• 編譯并運行
• python
• • 編寫程序
  • • turtle_tf_broadcaster.py
    • turtle_tf_listener.py
  • 運行

平臺：華碩 Thinker Edge R 瑞芯微 RK3399Pro
固件版本：Tinker_Edge_R-Debian-Stretch-V1.0.4-20200615

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記錄自【古月居】古月·ROS入門21講 | 一學就會的ROS機器人入門教程 —— 古月居GYH P18 18.tf坐標系廣播與監聽的編程實現

創建功能包

cd ~/catkin_workspace/src catkin_create_pkg learning_tf roscpp rospy tf turtlesim

如何實現一個tf廣播器

定義TF廣播器（TransformBroadcaster）

創建坐標變換值；

發布坐標變換（sendTransform）

創建tf廣播器代碼（C++）

nano ~/catkin_workspace/src/learning_tf/src/turtle_tf_broadcaster.cpp /*********************************************************************** Copyright 2020 GuYueHome (www.guyuehome.com). ***********************************************************************//*** 該例程產生tf數據，并計算、發布turtle2的速度指令*/#include <ros/ros.h> #include <tf/transform_broadcaster.h> #include <turtlesim/Pose.h>std::string turtle_name;void poseCallback(const turtlesim::PoseConstPtr& msg) {// 創建tf的廣播器static tf::TransformBroadcaster br;// 初始化tf數據tf::Transform transform;transform.setOrigin( tf::Vector3(msg->x, msg->y, 0.0) );tf::Quaternion q;q.setRPY(0, 0, msg->theta);transform.setRotation(q);// 廣播world與海龜坐標系之間的tf數據br.sendTransform(tf::StampedTransform(transform, ros::Time::now(), "world", turtle_name)); }int main(int argc, char** argv) {// 初始化ROS節點ros::init(argc, argv, "my_tf_broadcaster");// 輸入參數作為海龜的名字if (argc != 2){ROS_ERROR("need turtle name as argument"); return -1;}turtle_name = argv[1];// 訂閱海龜的位姿話題ros::NodeHandle node;ros::Subscriber sub = node.subscribe(turtle_name+"/pose", 10, &poseCallback);// 循環等待回調函數ros::spin();return 0; };

如何實現一個tf監聽器

定義TF監聽器；（TransformListener）

查找坐標變換；（waitForTransform，lookupTransform）

創建tf監聽器代碼（C++）

nano ~/catkin_workspace/src/learning_tf/src/turtle_tf_listener.cpp /*********************************************************************** Copyright 2020 GuYueHome (www.guyuehome.com). ***********************************************************************//*** 該例程監聽tf數據，并計算、發布turtle2的速度指令*/#include <ros/ros.h> #include <tf/transform_listener.h> #include <geometry_msgs/Twist.h> #include <turtlesim/Spawn.h>int main(int argc, char** argv) {// 初始化ROS節點ros::init(argc, argv, "my_tf_listener");// 創建節點句柄ros::NodeHandle node;// 請求產生turtle2ros::service::waitForService("/spawn");ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");turtlesim::Spawn srv;add_turtle.call(srv);// 創建發布turtle2速度控制指令的發布者ros::Publisher turtle_vel = node.advertise<geometry_msgs::Twist>("/turtle2/cmd_vel", 10);// 創建tf的監聽器tf::TransformListener listener;ros::Rate rate(10.0);while (node.ok()){// 獲取turtle1與turtle2坐標系之間的tf數據tf::StampedTransform transform;try{listener.waitForTransform("/turtle2", "/turtle1", ros::Time(0), ros::Duration(3.0));listener.lookupTransform("/turtle2", "/turtle1", ros::Time(0), transform);}catch (tf::TransformException &ex) {ROS_ERROR("%s",ex.what());ros::Duration(1.0).sleep();continue;}// 根據turtle1與turtle2坐標系之間的位置關系，發布turtle2的速度控制指令geometry_msgs::Twist vel_msg;vel_msg.angular.z = 4.0 * atan2(transform.getOrigin().y(),transform.getOrigin().x());vel_msg.linear.x = 0.5 * sqrt(pow(transform.getOrigin().x(), 2) +pow(transform.getOrigin().y(), 2));turtle_vel.publish(vel_msg);rate.sleep();}return 0; };

配置編譯規則

nano ~/catkin_workspace/src/learning_tf/CMakeLists.txt add_executable(turtle_tf_broadcaster src/turtle_tf_broadcaster.cpp) target_link_libraries(turtle_tf_broadcaster ${catkin_LIBRARIES})add_executable(turtle_tf_listener src/turtle_tf_listener.cpp) target_link_libraries(turtle_tf_listener ${catkin_LIBRARIES})

編譯并運行

cd ~/catkin_workspace catkin_make# 新建一個終端 source ~/catkin_workspace/devel/setup.bash roscore # 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun turtlesim turtlesim_node# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_broadcaster __name:=turtle1_tf_broadcaster /turtle1 # 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_broadcaster __name:=turtle2_tf_broadcaster /turtle2# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_listener # 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun turtlesim turtle_teleop_key# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rqt_graph

python

編寫程序

cd ~/catkin_workspace/src/learning_tf mkdir scripts

turtle_tf_broadcaster.py

nano ~/catkin_workspace/src/learning_tf/scripts/turtle_tf_broadcaster.py #!/usr/bin/env python # -*- coding: utf-8 -*-######################################################################## #### Copyright 2020 GuYueHome (www.guyuehome.com). ### ######################################################################### 該例程將請求/show_person服務，服務數據類型learning_service::Personimport roslib roslib.load_manifest('learning_tf') import rospyimport tf import turtlesim.msgdef handle_turtle_pose(msg, turtlename):br = tf.TransformBroadcaster()br.sendTransform((msg.x, msg.y, 0),tf.transformations.quaternion_from_euler(0, 0, msg.theta),rospy.Time.now(),turtlename,"world")if __name__ == '__main__':rospy.init_node('turtle_tf_broadcaster')turtlename = rospy.get_param('~turtle')rospy.Subscriber('/%s/pose' % turtlename,turtlesim.msg.Pose,handle_turtle_pose,turtlename)rospy.spin()

turtle_tf_listener.py

nano ~/catkin_workspace/src/learning_tf/scripts/turtle_tf_listener.py #!/usr/bin/env python # -*- coding: utf-8 -*-######################################################################## #### Copyright 2020 GuYueHome (www.guyuehome.com). ### ######################################################################### 該例程將請求/show_person服務，服務數據類型learning_service::Personimport roslib roslib.load_manifest('learning_tf') import rospy import math import tf import geometry_msgs.msg import turtlesim.srvif __name__ == '__main__':rospy.init_node('turtle_tf_listener')listener = tf.TransformListener()rospy.wait_for_service('spawn')spawner = rospy.ServiceProxy('spawn', turtlesim.srv.Spawn)spawner(4, 2, 0, 'turtle2')turtle_vel = rospy.Publisher('turtle2/cmd_vel', geometry_msgs.msg.Twist,queue_size=1)rate = rospy.Rate(10.0)while not rospy.is_shutdown():try:(trans,rot) = listener.lookupTransform('/turtle2', '/turtle1', rospy.Time(0))except (tf.LookupException, tf.ConnectivityException, tf.ExtrapolationException):continueangular = 4 * math.atan2(trans[1], trans[0])linear = 0.5 * math.sqrt(trans[0] ** 2 + trans[1] ** 2)cmd = geometry_msgs.msg.Twist()cmd.linear.x = linearcmd.angular.z = angularturtle_vel.publish(cmd)rate.sleep()

運行

sudo chmod +x ~/catkin_workspace/src/learning_tf/scripts/turtle_tf_broadcaster.py sudo chmod +x ~/catkin_workspace/src/learning_tf/scripts/turtle_tf_listener.py# 新建一個終端 source ~/catkin_workspace/devel/setup.bash roscore # 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun turtlesim turtlesim_node# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_broadcaster.py __name:=turtle1_tf_broadcaster _turtle:=turtle1 # 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_broadcaster.py __name:=turtle2_tf_broadcaster _turtle:=turtle2# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun learning_tf turtle_tf_listener.py# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rosrun turtlesim turtle_teleop_key# 新建一個終端 source ~/catkin_workspace/devel/setup.bash rqt_graph

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