lab1

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Georgia Institute Of Technology *

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8750

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Mechanical Engineering

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Apr 3, 2024

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pdf

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CS/ME/ECE/AE/BME 7785 Lab 1 Due: September 15, 2023 by 4 pm Overview The objective of this lab is to get you familiar with the robot and to get started writing code. Specifically, this lab consists of two parts: • Part 1a (individual) : run provided Turtlebot3 code to get experience interfacing with the robot. • Part 1b (group) : answer the ROS related questions. • Part 2 (group) : create your own image processing script that enables the robot to identify a desired object in its camera image. The code generated in Part 2 can be reused in Lab 2 to have your robot move to track whichever object you have chosen. Note Part 1 will take far less time than Part 2, so budget your time wisely. Part 1 is an individual assignment, each person must demonstrate ability to run the robot from a machine that they have access to. You can use your own laptop or the lab machines. You can not use your partner’s laptop to demo. We strongly encourage you to use all available resources to complete this assignment. This includes looking at the sample code provided with the robot, borrowing pieces of code from online tutorials, and talking to classmates. You may discuss solutions and problem solve with other groups in the class, but each group must submit their own solution. Multiple groups should not jointly write the same program and each submit a copy, this will not be considered a valid submission. Submission instruction and grading details are included at the end of the document. Handle your robot with care! • Battery Handling : The robots can be powered up using 2 methods: 1. Power the OpenCR board through the AC adapter. This is recommended if you’re debugging code and the robot doesn’t need to be mobile. 1

Introduction to Robotics Research, Lab 1: Spring, 2024 2. LiPo (Lithium Polymer) battery: LiPo batteries are high energy density batteries which are a popular power source for mobile robots such as UAVs, Rovers, (and Turtlebots!). They must be operated with care as they may explode and catch fire if mishandled. Here are some tips for handling LiPo batteries: 1. Do not hot swap batteries. This means do not plug in the AC adapter and switch batteries. Always power the robot down fully before removing and plugging in batteries. 2. NEVER puncture/pierce the LiPo battery and keep it away from sharp objects. 3. Do not leave batteries plugged into the robot, always unplug them after use. 4. If you notice any swollen/puffed batteries, notify the staff at once. 5. Use the LiPo battery chargers for recharging batteries. Red LED indicates charging, Green indicates charged. 6. If you are the last one leaving the lab, please unplug batteries from the chargers. A constant beeping sound indicates low battery. Ensure to save your work and shutdown your robot before replacing the battery. • Robot shutdown procedure : Before plugging out the power supply, please run the com- mand: sudo shutdown now Wait for the LIDAR to stop spinning and the Raspberry Pi’s green LED to stop blinking. At this point, it is safe to remove the power supply. Abruptly powering off may lead to your SD card getting corrupted and data loss. Part 1a: Interfacing with the Turtlebot3 All instructions for the Turtlebot3 are available online at http://emanual.robotis.com/docs/en/platform/turtlebot3/overview/ Complete the following steps: 1. Ensure you’ve completed the PC Setup and Turtlebot3 package installation as outlined in Lab 0. 2. Note : Section 3.1.5 has you place the line export ROS_DOMAIN_ID=30 # TURTLEBOT3 in the bashrc. This number should be edited depending on what robot you are using (the robot domain IDs are listed on the OLED on boot). 3. You will be able to ping, SSH, transfer files, and exchange ROS 2 messages to the robot if you are on the 7785/7785-5G network. Password is robot-wifi 2

Introduction to Robotics Research, Lab 1: Spring, 2024 4. Make sure you can access the Raspberry Pi on the robot. You will need to SSH ( secure shell) into the robot using the command, ssh burger@192.168.1.152 (The IP 192.168.1.152 should be replaced by your Raspberry Pi’s IP or hostname) The password is “ burger ” for all the robots. Once entering the password you should see the terminal environment on the Raspberry Pi of your Turtlebot3! 5. Complete the Quick Start guide on the above website (listed as item 3 on the left side menu) and verify that you are able to teleoperate the robot using the keyboard (Sections 3.5 and 3.6.1.1). Optionally, feel free to run any other examples, such as Turtlebot Follower to test out the robot functionality. Note: For ROS2 the robot and your laptop have to be on the same network for messages to communicate (e.g. run teleop on your PC rather than on the robot). Thus, switch the network you are on to CS3660 for controlling the robot. Part 1b: ROS Related Questions Please answer the following questions (from Lab 0) and submit them as a PDF with your code submission from part 2. • What is a ROS_DOMAIN_ID? (2pt) • What is a node? (2pt) • What is a topic? (2pt) • What is a message? (2pt) • What is a subscriber? Write the syntax to create a subscriber that subscribes to the topic amazing_int , which takes message of type UInt64 , and uses the callback function magic_fun , in C++ or Python. Note: This should only be a few lines of code, not a full script. (5pt) • What is a publisher? Write the syntax to create a publisher that publishes to the topic amazing_bool , which takes message of type Bool , in Python. Note: This should only be a few lines of code, not a full script. (5pt) • Can a node have multiple subscribers? Can a node have multiple publishers? (2pt) Part 2: Object Following Objective: Create a program to reliably locate and track an object of your choice from a real-time images stream on your computer. You are encouraged to use libraries such as OpenCV to complete this assignment. Note: This cannot be done using a pre-made tag tracker package like ArUco nor using premade ML packages like ImageAI. In this part of the lab, you will use OpenCV to locate an object from your laptop’s webcam. This is a valuable step towards Lab 2, in which you will track the object from your robots camera frame 3

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