add cpp version for urdf_tutorial

source/Tutorials/Intermediate/URDF/Using-URDF-with-Robot-State-Publisher-cpp.rst

@@ -0,0 +1,364 @@
+.. Redirect-from::
+
+    Tutorials/URDF/Using-URDF-with-Robot-State-Publisher
+
+.. _URDFPlusRSP:
+
+Using URDF with ``robot_state_publisher``
+=========================================
+
+**Goal:** Simulate a walking robot modeled in URDF and view it in Rviz.
+
+**Tutorial level:** Intermediate
+
+**Time:** 15 minutes
+
+.. contents:: Contents
+   :depth: 2
+   :local:
+
+Background
+----------
+
+This tutorial will show you how to model a walking robot, publish the state as a tf2 message and view the simulation in Rviz.
+First, we create the URDF model describing the robot assembly.
+Next we write a node which simulates the motion and publishes the JointState and transforms.
+We then use ``robot_state_publisher`` to publish the entire robot state to ``/tf2``.
+
+.. image:: images/r2d2_rviz_demo.gif
+
+Prerequisites
+-------------
+
+- `rviz2 <https://index.ros.org/p/rviz2/>`__
+
+As always, don’t forget to source ROS 2 in :doc:`every new terminal you open <../../Beginner-CLI-Tools/Configuring-ROS2-Environment>`.
+
+Tasks
+-----
+
+1 Create a package
+^^^^^^^^^^^^^^^^^^
+
+Go to your ROS 2 workplace and create a package names ``urdf_tutorial_cpp``:
+
+.. code-block:: console
+
+    cd src
+    ros2 pkg create --build-type ament_python --license Apache-2.0 urdf_tutorial_cpp --dependencies rclpy
+    cd urdf_tutorial_cpp
+
+You should now see a ``urdf_tutorial_cpp`` folder.
+Next you will make several changes to it.
+
+2 Create the URDF File
+^^^^^^^^^^^^^^^^^^^^^^
+
+Create the directory where we will store some assets:
+
+.. tabs::
+
+  .. group-tab:: Linux
+
+    .. code-block:: console
+
+      mkdir -p urdf
+
+  .. group-tab:: macOS
+
+    .. code-block:: console
+
+      mkdir -p urdf
+
+  .. group-tab:: Windows
+
+    .. code-block:: console
+
+      md urdf
+
+Download the :download:`URDF file <documents/r2d2.urdf.xml>` and save it as `urdf_tutorial_cpp/urdf/r2d2.urdf.xml`.
+Download the :download:`Rviz configuration file <documents/r2d2.rviz>` and save it as `urdf_tutorial_cpp/urdf/r2d2.rviz`.
+
+3 Publish the state
+^^^^^^^^^^^^^^^^^^^
+
+Now we need a method for specifying what state the robot is in.
+
+To do this, we must specify all three joints and the overall robot geometry.
+
+Fire up your favorite editor and paste the following code into
+
+``urdf_tutorial_cpp/src/urdf_tutorial.cpp``
+
+.. code-block:: cpp
+
+  #include <rclcpp/rclcpp.hpp>
+  #include <geometry_msgs/msg/quaternion.hpp>
+  #include <sensor_msgs/msg/joint_state.hpp>
+  #include <tf2_ros/transform_broadcaster.h>
+  #include <tf2_geometry_msgs/tf2_geometry_msgs.hpp>
+  #include <cmath>
+  #include <thread>
+  #include <chrono>
+
+  using namespace std::chrono;
+
+  class StatePublisher : public rclcpp::Node{
+      public:
+
+      StatePublisher(rclcpp::NodeOptions options=rclcpp::NodeOptions()):
+          Node("state_publisher",options){
+              joint_pub_ = this->create_publisher<sensor_msgs::msg::JointState>("joint_states",10);
+              // create a publisher to tell robot_state_publisher the JointState information.
+              // robot_state_publisher will deal with this transformation
+              broadcaster = std::make_shared<tf2_ros::TransformBroadcaster>(this);
+              // create a broadcaster to tell the tf2 state information
+              // this broadcaster will determine the position of coordinate system 'asix' in coordinate system 'odom'
+              RCLCPP_INFO(this->get_logger(),"Starting state publisher");
+
+              loop_rate_=std::make_shared<rclcpp::Rate>(33ms);
+
+              timer_=this->create_wall_timer(33ms,std::bind(&StatePublisher::publish,this));
+          }
+
+          void publish();
+      private:
+      rclcpp::Publisher<sensor_msgs::msg::JointState>::SharedPtr joint_pub_;
+      std::shared_ptr<tf2_ros::TransformBroadcaster> broadcaster;
+      rclcpp::Rate::SharedPtr loop_rate_;
+      rclcpp::TimerBase::SharedPtr timer_;
+
+      //Robot state variables
+
+      // degree means one degree
+      const double degree=M_PI/180.0;
+      double tilt = 0.;
+      double tinc = degree;
+      double swivel = 0.;
+      double angle = 0.;
+      double height = 0.;
+      double hinc = 0.005;
+  };
+
+  void StatePublisher::publish(){
+      // create msg subject
+      geometry_msgs::msg::TransformStamped t;
+      sensor_msgs::msg::JointState joint_state;
+
+      // add time stamp
+      joint_state.header.stamp=this->get_clock()->now();
+      // Specify joints' name which are defined in the r2d2.urdf.xml and their content
+      joint_state.name={"swivel","tilt","periscope"};
+      joint_state.position={swivel,tilt,height};
+
+      // add time stamp
+      t.header.stamp=this->get_clock()->now();
+      // specify the father and child frame
+
+      // odom is the base coordinate system of tf2
+      t.header.frame_id="odom";
+      // axis is defined in r2d2.urdf.xml file and it is the base coordiante of model
+      t.child_frame_id="axis";
+
+      // add translation change
+      t.transform.translation.x=cos(angle)*2;
+      t.transform.translation.y=sin(angle)*2;
+      t.transform.translation.z=0.7;
+      tf2::Quaternion q;
+      // ture euler angle into Quanternion and add rotation change
+      q.setRPY(0,0,angle+M_PI/2);
+      t.transform.rotation.x=q.x();
+      t.transform.rotation.y=q.y();
+      t.transform.rotation.z=q.z();
+      t.transform.rotation.w=q.w();
+
+      // update state for next time
+      tilt+=tinc;
+      if (tilt<-0.5 || tilt>0.0){
+          tinc*=-1;
+      }
+      height+=hinc;
+      if (height>0.2 || height<0.0){
+          hinc*=-1;
+      }
+      swivel+=degree;  // Increment by 1 degree (in radians)
+      angle+=degree;    // Change angle at a slower pace
+
+      // send message
+      broadcaster->sendTransform(t);
+      joint_pub_->publish(joint_state);
+
+      RCLCPP_INFO(this->get_logger(),"Publishing joint state");
+  }
+
+  int main(int argc, char * argv[]){
+      rclcpp::init(argc,argv);
+      rclcpp::spin(std::make_shared<StatePublisher>());
+      rclcpp::shutdown();
+      return 0;
+  }
+
+This file will send the ``joint_state`` to ``robot_state_publisher`` and ``robot_state_publisher`` will tell tf2 how to place model.
+
+This file will also tell ``tf2`` how to place the whole model by ``broadcaster``
+
+4 Create a launch file
+^^^^^^^^^^^^^^^^^^^^^^
+
+Create a new ``urdf_tutorial_cpp/launch`` folder.
+Open your editor and paste the following code, saving it as ``urdf_tutorial_cpp/launch/launch.py``
+
+.. code-block:: python
+
+  import os
+  from ament_index_python.packages import get_package_share_directory
+  from launch import LaunchDescription
+  from launch.actions import DeclareLaunchArgument
+  from launch.substitutions import LaunchConfiguration
+  from launch_ros.actions import Node
+
+  def generate_launch_description():
+
+      # ''use_sim_time'' is used to  determine whether ros2 use simulation time provided by simulation environment (Gazebo).
+      use_sim_time = LaunchConfiguration('use_sim_time', default='false')
+
+      urdf_file_name = 'r2d2.urdf.xml'
+
+      # urdf is path of urdf_file_name file. we use define it as the follow due to the CMakeLists.txt file.
+      urdf=os.path.join(
+          get_package_share_directory('urdf_tutorial_cpp'),
+          'urdf',
+          urdf_file_name
+      )
+
+      # open the whole urdf_file_name file and read it content to robot_desc
+      with open(urdf, 'r') as infp:
+          robot_desc = infp.read()
+
+          return LaunchDescription([
+          DeclareLaunchArgument(
+              'use_sim_time',
+              default_value='false',
+              description='Use simulation (Gazebo) clock if true'),
+         Node(
+              package='robot_state_publisher',
+              executable='robot_state_publisher',
+              name='robot_state_publisher',
+              output='screen',
+              parameters=[{'use_sim_time': use_sim_time, 'robot_description': robot_desc}],
+              arguments=[urdf]),
+          Node(
+              package='urdf_tutorial_cpp',
+              executable='urdf_tutorial_cpp',
+              name='urdf_tutorial_cpp',
+              output='screen'),
+      ])
+
+
+5 Edit the CMakeLists.txt file
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+You must tell the **colcon** build tool how to install your cpp package.
+Edit the ``CMakeLists.txt`` file as follows:
+
+.. code-block:: python
+
+  cmake_minimum_required(VERSION 3.8)
+  project(urdf_tutorial_cpp)
+
+  if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    add_compile_options(-Wall -Wextra -Wpedantic)
+  endif()
+
+  # find dependencies
+  find_package(ament_cmake REQUIRED)
+  find_package(geometry_msgs REQUIRED)
+  find_package(sensor_msgs REQUIRED)
+  find_package(tf2_ros REQUIRED)
+  find_package(tf2_geometry_msgs REQUIRED)
+  find_package(rclcpp REQUIRED)
+
+  add_executable(urdf_tutorial_cpp src/urdf_tutorial.cpp)
+
+  ament_target_dependencies(urdf_tutorial_cpp
+    geometry_msgs
+    sensor_msgs
+    tf2_ros
+    tf2_geometry_msgs
+    rclcpp
+  )
+
+  install(TARGETS
+    urdf_tutorial_cpp
+    DESTINATION lib/${PROJECT_NAME}
+  )
+
+  install(DIRECTORY
+    launch
+    DESTINATION share/${PROJECT_NAME}
+  )
+
+  install(DIRECTORY
+    urdf
+    DESTINATION share/${PROJECT_NAME}
+  )
+
+  ament_package()
+
+we use ``install`` command to put the r2d2.rviz into ``install`` dir
+
+6 Install the package
+^^^^^^^^^^^^^^^^^^^^^
+
+To visualize your results you will need to open a new terminal and run Rviz using your rviz configuration file. 
+
+.. code-block:: console
+
+    colcon build --symlink-install --packages-select urdf_tutorial_cpp
+
+Source the setup files:
+
+.. tabs::
+
+  .. group-tab:: Linux
+
+    .. code-block:: console
+
+      source install/setup.bash
+
+  .. group-tab:: macOS
+
+    .. code-block:: console
+
+      source install/setup.bash
+
+  .. group-tab:: Windows
+
+    .. code-block:: console
+
+      call install/setup.bat
+
+
+7 View the results
+^^^^^^^^^^^^^^^^^^
+
+To launch your new package run the following command:
+
+.. code-block:: console
+
+  ros2 launch urdf_tutorial_cpp launch.py
+
+To visualize your results you will need to open a new terminal and run Rviz using your rviz configuration file.
+
+.. code-block:: console
+
+  rviz2 -d install/urdf_tutorial_cpp/share/urdf_tutorial_cpp/urdf/r2d2.rviz
+
+See the `User Guide <http://wiki.ros.org/rviz/UserGuide>`__ for details on how to use Rviz.
+
+``install/urdf_tutorial_cpp/share/urdf_tutorial_cpp/urdf/r2d2.rviz`` is the dir where the r2d2.rviz stored.
+
+Summary
+-------
+
+Congratulations! You  have created a ``JointState`` publisher node and coupled it with ``robot_state_publisher`` to simulate a walking robot.