Learning ROS: Ubuntu16.04下kinetic开发环境安装和初体验 Install + Configure + Navigating(look around) + Creating a Package(catkin_create_pkg) + Building a Package(catkin_make) + Understanding Nodes

本文主要部分来源于ROS官网的Tutorials.

Ubuntu install of ROS Kinetic

# Setup your sources.list
sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
# Set up your keys
sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 421C365BD9FF1F717815A3895523BAEEB01FA116
# Installation
sudo apt-get update
sudo apt-get install ros-kinetic-desktop-full  # Desktop-Full Install: (Recommended)
# Initialize rosdep
sudo rosdep init
rosdep update
# Environment setup, so ROS environment variables are automatically added to your bash session every time a new shell is launched
echo "source /opt/ros/kinetic/setup.bash" >> ~/.bashrc
source ~/.bashrc
# Install this tool and other dependencies for building ROS packages
sudo apt-get install python-rosinstall python-rosinstall-generator python-wstool build-essential

Configuring Your ROS Environment

#  check to ensure that environment variables like ROS_ROOT and ROS_PACKAGE_PATH are set 
printenv | grep ROS
source /opt/ros/kinetic/setup.bash # if no ROS variable are set, run this command

# Create a ROS Workspace (use the recommended catkin)
mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/
catkin_make

# source your new setup.*sh file when a new shell is launched
echo 'source /home/youruser/catkin_ws/devel/setup.bash' >> ~/.bashrc
source ~/.bashrc
echo $ROS_PACKAGE_PATH # you will see /home/youruser/catkin_ws/src:/opt/ros/kinetic/share

Navigating the ROS Filesystem

sudo apt-get install ros-kinetic-ros-tutorials
rospack find roscpp # rospack find [package_name], returns the path to package

roscd roscpp
pwd # You can see that YOUR_INSTALL_PATH/share/roscpp is the same path that rospack find gave in the previous example

echo $ROS_PACKAGE_PATH #  ROS_PACKAGE_PATH should contain a list of directories where you have ROS packages separated by colons

roscd roscpp/cmake # roscd can also move to a subdirectory of a package or stack
pwd

roscd log # take you to the folder where ROS stores log files
               # Note that if you have not run any ROS programs yet, this will yield an error saying that it does not yet exist.

rosls roscpp_tutorials # rosls is part of the rosbash suite. It allows you to ls directly in a package by name rather than by absolute path. 

# Tab Completion
roscd roscpp_tut<<< now push the TAB key >>>

Creating a ROS Package

cd ~/catkin_ws/src
# catkin_create_pkg <package_name> [depend1] [depend2] [depend3]
catkin_create_pkg beginner_tutorials std_msgs rospy roscpp #  create a new package called 'beginner_tutorials' which depends on std_msgs, roscpp, and rospy

# build the packages in the catkin workspace
cd ~/catkin_ws
catkin_make
# To add the workspace to your ROS environment you need to source the generated setup file
. ~/catkin_ws/devel/setup.bash

rospack depends1 beginner_tutorials # First-order dependencies

roscd beginner_tutorials
cat package.xml # These dependencies for a package are stored in the package.xml file

rospack depends beginner_tutorials # Indirect dependencies， rospack can recursively determine all nested dependencies

Building a ROS Package

cd ~/catkin_ws/
ls src
catkin_make # build all catkin projects found in the src folder.
catkin_make install  # (optionally)
ls

Understanding ROS Nodes

sudo apt-get install ros-kinetic-ros-tutorials # install a lightweight simulator
roscore # the first thing you should run when using ROS
rosnode list # lists active nodes
rosnode info /rosout # display information about a specific node

# in a new terminal:
rosrun turtlesim turtlesim_node # You will see the turtlesim window

# in a new termina
rosnode list # lists active nodes
rosrun turtlesim turtlesim_node __name:=my_turtle # change the node's name to my_turtle
rosnode list # lists active nodes
rosnode ping my_turtle # test that it's up

Review

• Nodes: A node uses ROS to communicate with other nodes. A node really isn't much more than an executable file within a ROS package.
• Messages: ROS data type used when subscribing or publishing to a topic.
• Topics: Nodes can publish messages to a topic as well as subscribe to a topic to receive messages.
• Master: Name service for ROS (i.e. helps nodes find each other)
• rosout: ROS equivalent of stdout/stderr
• roscore: Master + rosout + parameter server (parameter server will be introduced later)

You may have noticed a pattern with the naming of the ROS tools，This naming pattern holds for many of the ROS tools.

• rospack = ros + pack(age)
• roscd = ros + cd
• rosls = ros + ls
• roscore = ros+core : master (provides name service for ROS) + rosout (stdout/stderr) + parameter server (parameter server will be introduced later)
• rosnode = ros+node : ROS tool to get information about a node.
• rosrun = ros+run : runs a node from a given package.