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Summary from ELEC4260 & 5660 @ HKUST (By Yiyan PENG)

Version: Ubuntu 20.04 & ROS 1 (noetic)

Last primary update: 2025-Feb-15

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ROS connects robots and supports communications and infrastructure.

ROS is better in Ubuntu. There are multiple ways to run Ubuntu and then ROS.

• Docker + GUI
• local Ubuntu + local ROS

Basic Commands

# check topics
rostopic list

# manually publish topics
rostopic pub -r 10 /cmd_vel geometry_msgs/Twist "xxx"
# rostopic pub --rate <freq_in_Hz> <topic_name> <msgs_data_type> <msgs_content>

# check topic content
rostopic echo <topic_name>

# save topic content in bags
rosbag record <topic_name_1> <topic_name_2> <xxx> # as many as want
# replay
rosbag replay <rosbag_name> # check the flag to see specific function features

Clean ROS Log files

Standard Workflow

Workspace Initialization

# Create a Workspace folder
mkdir -p ~/catkin_ws/src

# initialize the Workspace for the Package
cd ~/catkin_ws/src
# init workspace for workspace's src folder
catkin_init_workspace # CMakeLists.txt will be created for the "src" package folder

# Return to main Workspace & Build the Workspace
cd .. # pwd: ~/catkin_ws
catkin_make # build workspace -> "build" & "devel" folder will be created under the main Workspace

# Create ROS Package with <pkg_name> definition and dependences
cd ~/catkin_ws/src
catkin_create_pkg <pkg_name> std_msgs roscpp rospy

# Build again the Main Workspace
cd .. # pwd: ~/catkin_ws
catkin_make

Build Method in ROS (example)

Your code should be in this path → workspace/src/package/src/your_code

Example code

Publisher (Romeo)

#include <ros/ros.h>
#include <std_msgs/String.h>
int main(int argc, char **argv)
{
    ros::init(argc, argv, "romeo_node");
    printf("This is Romeo!\\n");

    ros::NodeHandle nh;
    ros::Publisher romeo_pub = nh.advertise<std_msgs::String>("romeo_topic", 2);

    ros::Rate loop_rate(2);

    while (ros::ok())
    {
        std_msgs::String msg;
        msg.data = "Romeo is still alive!";
        romeo_pub.publish(msg);
        loop_rate.sleep();
    }

    return 0;
}

Subscriber (Godfather subscribe romeo_topic)