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| Study note for ROS
* Core Concept
** Node and ROS Master
*** Node
implement functions for purposes
support various language
can have thousands of nodes
*** ROS Master
mange the registion and name of various nodes
support(trace and record) communication between different nodes
for nodes to find each other
provide parameter server(store global variables...)[[about parameter]]
** Communication between nodes
| | Topic | Service |
|--------------------+---------------------+----------------|
| sync | n | y |
| model | publish/subscribe | service/client |
| protocol | ROSTCP/ROSUDP | ROSTCP/ROSUDP |
| response | n | y |
| buffer | y | n |
| real-time | weak | strong |
| nodes relationship | multi/one to multi | one to multi |
| scene | data transformation | logic process |
*** Topic
Node(publisher)->Topic(/example)&Message_Tyoe(std_msgs/String)->other ROS nodes(subscriber)
Message: define the data type and struct of data, defined by .msg file
async
*** Service
C/S model(Client/Server)
client send requests, server return response data
defined by .srv file, defines the structure of the requests and response
ROS node(Service Server)
^ |response
request| v
ROS node(Service Client)
sync
** Parameter
<<about parameter>>
talker -> ROS master : setParam("foo",1)
listener -> ROS master: getParam("foo")
ROS master ->listener: {"foo",1}
multiple variable dictionary
for storing static nonbinary configuration, not suitable for dynamic
** File system
*** package
Basic unit in ROS, include the src of nodes, cfg, data def
*** package manifest
record the basic information of packages
*** Meta packages
orgnize multi packages for one common purpose
* Commond Line Tools
** rqt_graph
visualize tool
display the calculate process graph
** rosnode
display node information
*** rosnode list
list all node
default node /rosout
*** rosnode info /turtle_sim
show info of a node
** rostopic
usage like rosnode(list,info)
*** rostopic pub /../.. data_structure data
publish message as a topic
add -r num to repeat sending at rate num/s
** rosmsg
*** rosmsg show data_structure
show the data structure
** rosservice
| commond addition | |
|------------------------+-----------------------------------|
| list | list all service the node provide |
| call service_name data | |
** rosbag
| command addition | | | |
|-------------------------+-----------------------------------------------+--------+-----------------|
| record -a -O cmd_record | record the topic data in the system | -a:all | -O as a package |
| play cmd_record.bag | play the recorded data of previous simulation | | |
| | | | |
* setup workspace and function package
** workspace
*** overview
| src | source space | |
| build | build space | no need to touch |
| devel | develop space | script, executable file |
| install | install sapce | |
work space folder/
src/
CmakeLists.txt
package_1/
CmakeList.txt
package.xml
...
package_n/
CmakeList.txt
package.xml
...
build/
CATKIN_IGNORE
devel/
bin/
etc/
include/
lib/
share/
.catkin
env.bash
setup.bash
setup.sh
...
install/
bin/
etc/
include/
lib/
share/
.catkin
env.bash
setup.bash
setup.sh
...
*** setup
**** establish ws
mkdir -p ./catkin_ws/src
cd ./catkin_ws/src
catkin_init_workspace
**** compile ws
cd ./catkin_ws/
catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3
catkin_make install
**** set env variables
source devel/setup.bash
**** check env variables
echo $ROS_PACKAGE_PATHH
** fucntion package
*** setup
| establish package | cd ./src | |
| | catkin_create_pkg <pkg_name> [depend1] [depend2].. (rospy,roscpp,std_msgs) | |
| source env path | source devel/setup.bash | make sure that ros can detect the pkg |
*** package.xml
| label | description |
|------------------------------+-----------------------------------------------------|
| <name> | |
| <version> | |
| <description> | |
| <maintainer email=""> | maintainer's name and email |
| <license> | |
| <buildtool depend> | usually catkin |
| <build_depend>/<exec_depend> | package dependencies ,usually roscpp rospy std_msgs |
*** CmakeList.txt
TODO
|
