ROS笔记

ros-note-data.md

##创建msg

###msg是什么

msg是一个普通的文本文件，描述了一个消息的数据成员（数据结构），它将作为原型去生成各种编程语言能够使用的数据类型。

###Creating a msg

Firstly, we need a msg folder with a filename.msg file under the package folder.

Then, write the msg file with the format per line.

Then, open package.xml, and make sure these two lines are in it and uncommented:

  <build_depend>message_generation</build_depend>
  <run_depend>message_runtime</run_depend>

And in CMakeLists.txt, check the content below:

# Do not just add this to your CMakeLists.txt, 
# modify the existing text to add message_generation before the closing parenthesis
find_package(catkin REQUIRED COMPONENTS
   roscpp
   rospy
   std_msgs
   message_generation
)

catkin_package(
  ...
  CATKIN_DEPENDS message_runtime ...
  ...)

add_message_files(
  FILES
  yours.msg
)

##创建srv$ rosmsg sh $ rosmsg sh ###srv是什么

同msg一样，srv是用来描述service的纯文本和原型描述；特别地，它需要描述请求和响应两个部分。

###Creating a srv

Create .srv file in package_path/srv/your.srv

Check the content in package.xml:

  <build_depend>message_generation</build_depend>
  <run_depend>message_runtime</run_depend>

and check these content in CMakeLists.txt:

# Do not just add this line to your CMakeLists.txt, 
# modify the existing line
find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  std_msgs
 message_generation
)

add_service_files(
  FILES
  your.srv
)

Similar to msg, use `rossrv show <srvname>` to check it.

ros-note-instr.md

##topic

topic的主命令是rostopic，其子命令有：

1. bw - 输出topic使用的带宽

2. echo - 输出topic的msg内容

3. hz - 输出topic发布msg的频率

4. list - 输出所有活动的topic

5. pub - 手动发送msg给topic

6. type - 输出topic的msg类型名称

输出msg具体的数据结构使用：

$ rosmsg show `rostopic type [topic]`

rostopic pub的一些参数：

1. -1 这个msg只发布一次
2. -r 1 以频率(rate)1Hz发布msg
3. -- 在double-dash之后的字符串都不被认为是option，用于输入msg

---

##service

options:

rosservice list  # print information about active services
rosservice call  # call the service with the provided args
rosservice type  # print service type
rosservice find  # find services by service type
rosservice uri   # print service ROSRPC uri

---

##parameter

主要设置和修改一些背景参数：

$ rosparam set      # parameter
$ rosparam get      # get parameter
$ rosparam load     # load parameters from file
$ rosparam dump     # dump parameters to file
$ rosparam delete   # delete parameter
$ rosparam list     # list parameter names

---

##图形工具

使用rqt_graph来观察node之间的msg和topic：

$ rosrun rqt_graph rqt_graph

使用rqt_plot来观察msg数据的时间变化：

$ rosrun rqt_plot rqt_plot

---

##其他

###roslaunch

roslaunch可以一步启动多个包：

$ roslaunch [package] [filename.launch]

首先需要在workspace下准备launch文件夹，在launch文件夹内创建filename.launch文件，内容为xml，样例如下：

# start tag
<launch>
# ns = namespace
  <group ns="turtlesim1">
    <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
  </group>
  # 两个相同的node放在不同的namespace下，不会冲突
  <group ns="turtlesim2">
    <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
  </group>
  <node pkg="turtlesim" name="mimic" type="mimic">
  # 还需理解
    <remap from="input" to="turtlesim1/turtle1"/>
    <remap from="output" to="turtlesim2/turtle1"/>
  </node>
</launch>