ROS入门学习（基于Ubuntu16.04+kinetic）

本文主要部分全部来源于ROS官网的Tutorials.

Setup

roscore # making sure that we have roscore running
rosrun turtlesim turtlesim_node
rosrun turtlesim turtle_teleop_key # Now you can use the arrow keys of the keyboard to drive the turtle around.

ROS Topics

sudo apt-get install ros-kinetic-rqt
sudo apt-get install ros-kinetic-rqt-common-plugins
rosrun rqt_graph rqt_graph

rostopic -h
rostopic echo /turtle1/cmd_vel # you will now see topic datas when you press the arrow key in turtle_teleop_key terminal 

rostopic list -h # figure out what argument the list sub-command needs
rostopic list -v # displays a verbose list of topics to publish to and subscribe to and their type

rostopic type /turtle1/cmd_vel  # You should get the message type of the topic: geometry_msgs/Twist
rosmsg show geometry_msgs/Twist  #  look at the details of the message using rosmsg

Using rostopic pub

# publishes data on to a topic, rostopic pub [topic] [msg_type] [args]
rostopic pub -1 /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'
#  publishes the velocity commands at a rate of 1 Hz on the velocity topic
rostopic pub /turtle1/cmd_vel geometry_msgs/Twist -r 1 -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, -1.8]'
# Now We can also look at what is happening in rqt_graph.
# and see the data published by our turtlesim
rostopic echo /turtle1/pose

# see how fast the turtlesim_node is publishing /turtle1/pose, $ rostopic hz [topic]
rostopic hz /turtle1/pose

# get in depth information about a topic
rostopic type /turtle1/cmd_vel | rosmsg show

Using rqt_plot

rosrun rqt_plot rqt_plot
# a text box in the upper left corner gives you the ability to add any topic to the plot.
# Typing /turtle1/pose/x and add it.
# Typing /turtle1/pose/y and add it.

ROS Services and Parameters

rosservice list # shows us that the turtlesim node provides nine services
rosservice type /clear # find out what type the clear service is
rosservice call /clear # clears the background of the turtlesim_node

#  look at the case where the service has arguments by looking at the information for the service spawn
rosservice type /spawn | rossrv show
rosservice call /spawn 2 2 0.2 "" # spawn a new turtle at a given location and orientation

rosparam list # look at what parameters are currently on the param server
rosparam set /background_r 150  # change the red channel of the background color
rosservice call /clear # call the clear service for the parameter change to take effect
rosparam get /background_g # get the value of the green background channel
rosparam get / # show us the contents of the entire Parameter Serve

rosparam dump params.yaml #  write all the parameters to the file ./params.yaml (current directory)
rosparam load params.yaml copy # load these yaml files into new namespaces
rosparam get /copy/background_b

Using rqt_console and roslaunch

This tutorial introduces ROS using rqt_console and rqt_logger_level for debugging and roslaunch for starting many nodes at once.

sudo apt-get install ros-kinetic-rqt ros-kinetic-rqt-common-plugins ros-kinetic-turtlesim

# in two new terminals start rqt_console and rqt_logger_level
rosrun rqt_console rqt_console
rosrun rqt_logger_level rqt_logger_level

rosrun turtlesim turtlesim_node # Since the default logger level is INFO you will see any info that the turtlesim publishes when it starts up

roscd beginner_tutorials
mkdir launch
cd launch
gedit turtlemimic.launch

<launch>

  <group ns="turtlesim1">
    <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
  </group>

  <group ns="turtlesim2">
    <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
  </group>

  <node pkg="turtlesim" name="mimic" type="mimic">
    <remap from="input" to="turtlesim1/turtle1"/>
    <remap from="output" to="turtlesim2/turtle1"/>
  </node>

</launch>

roslaunch beginner_tutorials turtlemimic.launch
rostopic pub /turtlesim1/turtle1/cmd_vel geometry_msgs/Twist -r 1 -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, -1.8]' #  the two turtlesims start moving even though the publish command is only being sent to turtlesim1

Using rosed to edit files in ROS

rosed roscpp Logger.msg #  demonstrates how you would edit the Logger.msg file within the roscpp package

rosed roscpp <tab><tab> # tab auto complete

echo "export EDITOR='gedit -w'" >> ~/.bashrc
source ~/.bashrc
echo $EDITOR
rosed roscpp Logger.msg # This time file will be open by The more beginner-friendly editor

Creating a ROS msg and srv

• msg: msg files are simple text files that describe the fields of a ROS message. They are used to generate source code for messages in different languages.
• srv: an srv file describes a service. It is composed of two parts: a request and a response.

Aboat Msg

$ roscd beginner_tutorials
$ mkdir msg
$ echo "int64 num" > msg/Num.msg

rosed beginner_tutorials package.xml

Open package.xml, and make sure these two lines are in it.

  <build_depend>message_generation</build_depend>
  <exec_depend>message_runtime</exec_depend>

rosed beginner_tutorials CMakeLists.txt

Modify it like this:

find_package(catkin REQUIRED COMPONENTS
   roscpp
   rospy
   std_msgs
   message_generation
)
...
catkin_package(
  ...
  CATKIN_DEPENDS message_runtime ...
  ...)
...
add_message_files(
  FILES
  Num.msg
)
...
generate_messages(
  DEPENDENCIES
  std_msgs
)
...

Make sure ROS can see it.

rosmsg show beginner_tutorials/Num # You will see: int64 num
rosmsg show Num # You will see: [beginner_tutorials/Num]: int64 num

Aboat srv

$ roscd beginner_tutorials
$ mkdir srv
$ roscp rospy_tutorials AddTwoInts.srv srv/AddTwoInts.srv
$ rosed beginner_tutorials CMakeLists.txt

Modify it like this:

...
add_service_files(
  FILES
  AddTwoInts.srv
)
...

make sure that ROS can see it using the rossrv show command

rossrv show beginner_tutorials/AddTwoInts
rossrv show AddTwoInts

Now that we have made some new messages we need to make our package again:

$ roscd beginner_tutorials
$ cd ../..
$ catkin_make install
$ cd -

Any .msg file in the msg directory will generate code for use in all supported languages. The C++ message header file will be generated in ~/catkin_ws/devel/include/beginner_tutorials/.

rosmsg -h

Review

Let's just list some of the commands we've used so far:

• rospack = ros+pack(age) : provides information related to ROS packages

• roscd = ros+cd : changes directory to a ROS package or stack

• rosls = ros+ls : lists files in a ROS package

• roscp = ros+cp : copies files from/to a ROS package

• rosmsg = ros+msg : provides information related to ROS message definitions
• rossrv = ros+srv : provides information related to ROS service definitions
• catkin_make : makes (compiles) a ROS package
  • rosmake = ros+make : makes (compiles) a ROS package (if you're not using a catkin workspace)