Posted 2022-04-12Updated 2024-11-02Note3 minutes read (About 505 words)

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

Posted 2022-04-11Updated 2024-11-02Notea minute read (About 211 words)

How I set up my blog site

This post record the steps I set up this blog site.

Catalog

Env preparation
Github
- Connection
- Setup Github Pages repository
Install Hexo
Deploy to Github server

Env preparation

Installation

Install Node.js
Install Git

Use following command to confirm:

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$ node -v
$ npm -v
$ git --version

Github

Connection

Create and copy SSH key:

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$ ssh-keygen -t rsa -C "GitHub email"
$ cd ~/.ssh
$ vim id_rsa.pub

Copy the contents

Go to Github -> Settings and Add SSH key

Confirm the connection:

1	$ ssh -T git@github.com

Setup Github Pages repository

Create Username.github.io(your URL)

Install Hexo

1	$ npm install -g hexo-cli

Setup a local workspace:

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$ git init
$ hexo init
$ npm install

launch local server:

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$ hexo cl
$ hexo g
$ hexo s

or use following command to specify port:

1	$ hexo server -p 5000

visit http://localhost:4000

Deploy to Github server

Install hexo-developer-git:

1	$ npm install hexo-deployer-git --save

edit _config file’s Deployment part:

deploy:
  type: git
  repository: git@github.com:Chen-Yulin/Chen-Yulin.github.io.git
  branch: master

then run in bash:

$ hexo d

Posted 2022-04-04Updated 2024-11-02Notea minute read (About 123 words)

Hexo Start

Welcome to Hexo! This is your very first post. Check documentation for more info. If you get any problems when using Hexo, you can find the answer in troubleshooting or you can ask me on GitHub.

Quick Start

Create a new post

1	$ hexo new "My New Post"

More info: Writing

Run server

1	$ hexo server

More info: Server

Generate static files

1	$ hexo generate

More info: Generating

Deploy to remote sites

1	$ hexo deploy

More info: Deployment