Course_T3InstructionManual_Unit1.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Mastering with ROS: Turtlebot3"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/robotis_logo.png\" width=\"400\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/t3_burger.png\" width=\"500\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/robotignite_logo_text.png\" width=\"400\"/>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit 1: Basic Usage"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:green;color:white;\">SUMMARY</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Estimated time of completion: <b>1h</b><br><br>\n",
    "In this Unit, you are going to see some basic information you need to know before you start working with the Turtlebot3 robot. Relevant topics, basic motion, etc..."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:green;color:white;\">END OF SUMMARY</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The very first thing you will want to do when you start working with a mobile robot, is to be able to move it, right?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Well then, in this first Chapter, you are going to see how you can easily move the robot by using two basic methods:\n",
    "\n",
    "* Publishing directly to topics\n",
    "* Using the keyboard teleop"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "So... let's stop the talking and go for it!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Move the robot publishing to topics"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The first we need to know in order to move the hand through topics, is which topics are the ones that will allow us to do that, right? Let's then have a look at the topics provided by the simulation and see if we can figure that out."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "rostopic list"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Can you guess which one it is? "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/t3_topics.png\" width=\"400\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Did you know? Well, the topic used in order to control the velocities of the robot is **/cmd_vel**. Publishing to this topic, we will be able to control the movement of the Turtlebot3 robot. But how is that done? What do we need to publish into this topic? Let's have a look at how this works!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "rostopic info /cmd_vel"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/cmd_vel_info.png\" width=\"500\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "As you can see, this topic uses the **geometry_msgs/Twist** message. So this is the type of message that we will need to send to the topic in order to control the hand. So, let's have a look at this message!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "rosmsg show geometry_msgs/Twist"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/twist_msg.png\" width=\"500\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "As you can see, the message contains 2 vectors: one for the linear velocities, and the other one for the angular velocities. Each of this vectors has its corresponding component in x,y and z. Anyways, the Turtlebot uses the differential drive mechanism in order to move. So what does this mean? This means that we just need to worry about the linear x and angular z components, which are the only ones that have effect into a differential drive robot. So, not all the fields need to be filled, but just the ones we are interested in. So now, if you want to see how you can fill this message in order to control the hand, just follow the next exercise!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">Exercise 1.1</p>\n",
    "<br>\n",
    "a) Execute the following command in order to generate the structure of the geometry_msgs/Twist message.\n",
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
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    "collapsed": true
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   "source": [
    "rostopic pub /cmd_vel [TAB][TAB]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You will see something like this:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/cmd_structure.png\" width=\"700\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "b) Now, fill in the message with the proper velocities you want to send to your robot. For this exercise, let's set the **linear velocity in x to 0.5**, and the **angular velocity in z to 0.5**, aswell."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "c) Finally, just press enter in order to send the message! If everything went OK, you should see your Turtlebot3 robot doing a circular movement."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/t3_circle.gif\" width=\"600\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "d) In order to stop the robot's movement, you will have to set again the velocities to 0."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">End of Exercise 1.1</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Great! So you have been able to move the robot by publishing directly into the **/cmd_vel** topic. Now let's how else you can achieve this."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Moving the robot with the keyboard"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "Sometimes, it's just too cumberstome to have to publish the velocities into a topic each time we want to move the robot, and gets much more complicated when we want to execute more complex trajectories. Fortunately, there is a very ROS program that allows us to control the movement of the robot by just using the keyboard. Sounds good, right?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "In order to see how you can control the Turtlebot3 robot with the keyboard, follow the next exercise!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">Exercise 1.2</p>\n",
    "<br>\n",
    "a) Execute the following command in order to start the keyboard teleoperation program."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "roslaunch turtlebot_teleop keyboard_teleop.launch"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now, you will be able to control the robot by using the keyboard. You can have a look at how the different keys work in the instructions below:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "Control Your Turtlebot!\n",
    "---------------------------\n",
    "Moving around:\n",
    "   u    i    o\n",
    "   j    k    l\n",
    "   m    ,    .\n",
    "\n",
    "q/z : increase/decrease max speeds by 10%\n",
    "w/x : increase/decrease only linear speed by 10%\n",
    "e/c : increase/decrease only angular speed by 10%\n",
    "space key, k : force stop\n",
    "anything else : stop smoothly\n",
    "\n",
    "CTRL-C to quit"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "b) Just move the robot around!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">End of Exercise 1.2</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "As you can see, it is much more easy to control the movement of the robot by using this method, right?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Well, now you already have some more knowledge and tools in order to control the Turtlebot3 robot, let's have a look at some of the sensros it brings."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "For the case of the **Turtlebot3 burger**, which is the one we are using in this Unit, it brings a 360 degrees LIDAR, which is perfect for Navigation and SLAM (which you'll see in the following Unit). So let's have a look at this laser in the following exercise:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">Exercise 1.3</p>\n",
    "<br>\n",
    "a) Before starting with the exercise itself, make sure that your robot is quite close to the wall that appears in the simulation. Something like this will be enough:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/robot_wall.png\" width=\"600\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "b) Now, launch RViz using the following command:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "rosrun rviz rviz"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "c) Click on the \"Add\" button and select the LaserScan element."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<div style=\"text-align: left\">\n",
    "<img src=\"img/add_btn.png\" width=\"350\" style=\"float: left; margin: 0px 0px 15px 15px;\"/>\n",
    "<img src=\"img/scan_element.png\" width=\"400\" style=\"inline\" />\n",
    "</div>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "d) Configure the LaserScan display with the corresponding topic. You can also make the size of the marker a little bit bigger in order to visualize it better."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/scan_config.png\" width=\"300\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "e) Finally, set the Fixed Frame to **base_scan**, which is the frame of the laser. You should end up with something like the image below:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/scan_rviz.png\" width=\"450\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">End of Exercise 1.3</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Excellent! So... what have you just done in this exercise? Basically, what you've done is to **visualize the readings of the laser mounted on top of the Turtlebot3 robot**. And you've used RViz to do so. Furthermore, you are able to visualize this data because, in fact, it is being published into a topic!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "While you were configuring the laser element in RViz, you did have to set a topic. Do you remember? This topic was the **/scan** topic. So, this means that this is the topic where the data of the reading of the laser is being published. Want to have a look at this topic? Let's go then!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "rostopic echo /scan -n1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You should see something like this:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"img/scan_msg.png\" width=\"1000\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Wow! This is quite a lot of data, right? Keep calm, it's not that complicated. Let's analyze the most important parts of this message."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "* **angle_min, angle_max and angle_increment**: This values tell us information about the angles related to the laser beams. We have the angle where they start and where they end (angle_min and angle_max), which show us that the laser beams have an scope of 360º. Also, the angle_increment value tells us which is the angle (separation) between each laser beam."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "* **range_min and range_max**: This values provide information about the ranges of the laser. Basically, we can see here that the range of these laser beams are of 3.5 meters. So, objects beyond this distance will not be detected by the laser."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "* **ranges**: This is the most important parameter of the message. It contains an array with all the values associated to the readings of the laser beams."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "So basically, the most important part of the message is the **ranges** array, which actually contains the data of the readings of the laser sensor. The other parameters, though, will help us interpret this values. For instance, with the values of the angles, we can have an idea of what is the area associated to each of the laser readings contained in the ranges array."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">Exercise 1.4</p>\n",
    "<br>\n",
    "a) Create a new ROS package which is called **object_detection**."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<table style=\"float:left;background: #407EAF\">\n",
    "<tr>\n",
    "<th>\n",
    "Execute in WebShell #1\n",
    "</th>\n",
    "</tr>\n",
    "</table>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "catkin_create_pkg exercise_1_4 rospy"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "b) Now, inside the **src** folder of the package, create a new Python file named **object_detection.py**"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "c) Inside this Python file, write an script that does the following:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "1. First, it moves the robot in the direction of the wall.\n",
    "2. When the distance between the robot and the wall is less than 1 meter, the robot will stop."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "d) Create a directory named **launch** inside the package, which will contains a launch file in order to execute your ROS program."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p style=\"background:#EE9023;color:white;\">End of Exercise 1.4</p>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "And that's it! With this Unit you've learnt a couple of basic concepts about the usage of the Turtlebot3 robot. Now, you're ready to go through the hard stuff!"
   ]
  }
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