2020/10/22
ROS初級Tutorialを実施しました[Vol.2]
概要
ROSの入門編その2です。前回の記事の続きです。
- rosedは単純だったので飛ばしました
- 「シンプルなPublisherとSubscriberを実行してみる」のPython編も飛ばしました
- 動作環境や本記事の目的などは前回の記事をみてください
ROSメッセージ
$ cd ~/catkin_ws/src/beginner_tutorials
$ mkdir msg
# int64のnumというフィールドだけのNumメッセージを作成します
$ echo "int64 num" > msg/Num.msg
- rosed を使って、beginner_tutorialsのpackage.xmlを修正します。
$ rosed beginner_tutorials package.xml
# 以下をそれぞれ追記します
# <build_depend>message_generation</build_depend>
# <exec_depend>message_runtime</exec_depend>
$ cat ~/catkin_ws/src/beginner_tutorials/package.xml
<?xml version="1.0"?>
<package format="2">
<name>beginner_tutorials</name>
<version>0.0.0</version>
<description>The beginner_tutorials package</description>
<maintainer email="[email protected]">Hiroki Tanaka</maintainer>
<license>MIT</license>
<author email="[email protected]">Hiroki Tanaka</author>
<buildtool_depend>catkin</buildtool_depend>
<build_depend>roscpp</build_depend>
<build_depend>rospy</build_depend>
<build_depend>std_msgs</build_depend>
<build_depend>message_generation</build_depend>
<build_export_depend>roscpp</build_export_depend>
<build_export_depend>rospy</build_export_depend>
<build_export_depend>std_msgs</build_export_depend>
<exec_depend>roscpp</exec_depend>
<exec_depend>rospy</exec_depend>
<exec_depend>std_msgs</exec_depend>
<exec_depend>message_runtime</exec_depend>
</package>
- CMakeLists.txtを編集します
$ rosed beginner_tutorials CMakeLists.txt
find_package(catkin REQUIRED COMPONENTS
roscpp
rospy
std_msgs
message_generation # この行を追加
)
catkin_package(
CATKIN_DEPENDS roscpp rospy std_msgs message_runtime # この行を追加
)
# 以下のblockを追加
add_message_files(
FILES
Num.msg
)
# 以下のblockを追加
generate_messages(
DEPENDENCIES
std_msgs
)
- ROSメッセージの定義を確認
$ rosmsg show Num
[beginner_tutorials/Num]:
int64 num
サービス(srv)
$ roscd beginner_tutorials
$ mkdir srv
# rospy_tutorialsのAddTwoInts.srvサービスをコピーします
$ roscp rospy_tutorials AddTwoInts.srv srv/AddTwoInts.srv
- CMakeLists.txtを編集します
$ rosed beginner_tutorials CMakeLists.txt
# 以下のblockを追加
add_service_files(
FILES
AddTwoInts.srv
)
- srvの定義を確認
rossrv show AddTwoInts
[beginner_tutorials/AddTwoInts]:
int64 a
int64 b
---
int64 sum
[rospy_tutorials/AddTwoInts]:
int64 a
int64 b
---
int64 sum
build
ソースコードを書くまえにいったんbuildします
$ cd ~/catkin_ws
$ catkin_make
Publisher & Subscriber in C++
$ roscd beginner_tutorials/src
$ cat <<EOF > talker.cpp
#include "ros/ros.h"
#include "std_msgs/String.h"
#include <sstream>
/**
* This tutorial demonstrates simple sending of messages over the ROS system.
*/
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "talker");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The advertise() function is how you tell ROS that you want to
* publish on a given topic name. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. After this advertise() call is made, the master
* node will notify anyone who is trying to subscribe to this topic name,
* and they will in turn negotiate a peer-to-peer connection with this
* node. advertise() returns a Publisher object which allows you to
* publish messages on that topic through a call to publish(). Once
* all copies of the returned Publisher object are destroyed, the topic
* will be automatically unadvertised.
*
* The second parameter to advertise() is the size of the message queue
* used for publishing messages. If messages are published more quickly
* than we can send them, the number here specifies how many messages to
* buffer up before throwing some away.
*/
ros::Publisher chatter_pub = n.advertise<std_msgs::String>("chatter", 1000);
ros::Rate loop_rate(10);
/**
* A count of how many messages we have sent. This is used to create
* a unique string for each message.
*/
int count = 0;
while (ros::ok())
{
/**
* This is a message object. You stuff it with data, and then publish it.
*/
std_msgs::String msg;
std::stringstream ss;
ss << "hello world " << count;
msg.data = ss.str();
ROS_INFO("%s", msg.data.c_str());
/**
* The publish() function is how you send messages. The parameter
* is the message object. The type of this object must agree with the type
* given as a template parameter to the advertise<>() call, as was done
* in the constructor above.
*/
chatter_pub.publish(msg);
ros::spinOnce();
loop_rate.sleep();
++count;
}
return 0;
}
EOF
$ cat <<EOF > listener.cpp
#include "ros/ros.h"
#include "std_msgs/String.h"
/**
* This tutorial demonstrates simple receipt of messages over the ROS system.
*/
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
ROS_INFO("I heard: [%s]", msg->data.c_str());
}
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "listener");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The subscribe() call is how you tell ROS that you want to receive messages
* on a given topic. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. Messages are passed to a callback function, here
* called chatterCallback. subscribe() returns a Subscriber object that you
* must hold on to until you want to unsubscribe. When all copies of the Subscriber
* object go out of scope, this callback will automatically be unsubscribed from
* this topic.
*
* The second parameter to the subscribe() function is the size of the message
* queue. If messages are arriving faster than they are being processed, this
* is the number of messages that will be buffered up before beginning to throw
* away the oldest ones.
*/
ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
/**
* ros::spin() will enter a loop, pumping callbacks. With this version, all
* callbacks will be called from within this thread (the main one). ros::spin()
* will exit when Ctrl-C is pressed, or the node is shutdown by the master.
*/
ros::spin();
return 0;
}
EOF
- CMakeLists.txtを編集します
$ rosed beginner_tutorials CMakeLists.txt
最終的に以下のようになりました
cmake_minimum_required(VERSION 3.0.2)
project(beginner_tutorials)
## Find catkin macros and libraries
find_package(
catkin REQUIRED COMPONENTS
roscpp
rospy
std_msgs
message_generation
)
## Generate messages in the 'msg' folder
add_message_files(
FILES
Num.msg
)
## Generate services in the 'srv' folder
add_service_files(
FILES
AddTwoInts.srv
)
## Generate added messages and services with any dependencies listed here
generate_messages(
DEPENDENCIES
std_msgs
)
catkin_package(
CATKIN_DEPENDS roscpp rospy std_msgs message_runtime
)
###########
## Build ##
###########
include_directories(
include
${catkin_INCLUDE_DIRS}
)
add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_dependencies(talker beginner_tutorials_generate_messages_cpp)
add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
add_dependencies(listener beginner_tutorials_generate_messages_cpp)
Publisher & Subscriber の実行
roscore
は実行済です
$ cd ~/catkin_ws
# publisherを実行
$ rosrun beginner_tutorials talker
[ INFO] [1603376210.426369525]: hello world 0
[ INFO] [1603376210.526457373]: hello world 1
[ INFO] [1603376210.626455165]: hello world 2
[ INFO] [1603376210.726559493]: hello world 3
[ INFO] [1603376210.826484491]: hello world 4
[ INFO] [1603376210.926445267]: hello world 5
[ INFO] [1603376211.026510950]: hello world 6
[ INFO] [1603376211.126528268]: hello world 7
[ INFO] [1603376211.226548101]: hello world 8
... (中略) ...
[ INFO] [1603376234.826548893]: hello world 244
[ INFO] [1603376234.926554847]: hello world 245
[ INFO] [1603376235.026547130]: hello world 246
[ INFO] [1603376235.126552281]: hello world 247
[ INFO] [1603376235.226548325]: hello world 248
[ INFO] [1603376235.326537521]: hello world 249
[ INFO] [1603376235.426537503]: hello world 250
[ INFO] [1603376235.526550766]: hello world 251
[ INFO] [1603376235.626521874]: hello world 252
[ INFO] [1603376235.726546779]: hello world 253
[ INFO] [1603376235.826522493]: hello world 254
[ INFO] [1603376235.926551702]: hello world 255
[ INFO] [1603376236.026472538]: hello world 256
[ INFO] [1603376236.126421674]: hello world 257
[ INFO] [1603376236.226488493]: hello world 258
[ INFO] [1603376236.326539414]: hello world 259
[ INFO] [1603376236.426564354]: hello world 260
[ INFO] [1603376236.526488794]: hello world 261
[ INFO] [1603376236.626554490]: hello world 262
[ INFO] [1603376236.726487617]: hello world 263
[ INFO] [1603376236.826548155]: hello world 264
[ INFO] [1603376236.926558722]: hello world 265
[ INFO] [1603376237.026475720]: hello world 266
# 別タブでlistenerを実行
$ rosrun beginner_tutorials listener
[ INFO] [1603376234.827445525]: I heard: [hello world 244]
[ INFO] [1603376234.927214425]: I heard: [hello world 245]
[ INFO] [1603376235.027172208]: I heard: [hello world 246]
[ INFO] [1603376235.127233117]: I heard: [hello world 247]
[ INFO] [1603376235.227291853]: I heard: [hello world 248]
[ INFO] [1603376235.327035815]: I heard: [hello world 249]
[ INFO] [1603376235.427000166]: I heard: [hello world 250]
[ INFO] [1603376235.527069419]: I heard: [hello world 251]
[ INFO] [1603376235.627128705]: I heard: [hello world 252]
[ INFO] [1603376235.727142543]: I heard: [hello world 253]
[ INFO] [1603376235.827062589]: I heard: [hello world 254]
[ INFO] [1603376235.927131465]: I heard: [hello world 255]
[ INFO] [1603376236.026852485]: I heard: [hello world 256]
[ INFO] [1603376236.126615307]: I heard: [hello world 257]
[ INFO] [1603376236.226727480]: I heard: [hello world 258]
[ INFO] [1603376236.327026875]: I heard: [hello world 259]
[ INFO] [1603376236.427189047]: I heard: [hello world 260]
[ INFO] [1603376236.527177079]: I heard: [hello world 261]
[ INFO] [1603376236.627105702]: I heard: [hello world 262]
[ INFO] [1603376236.727174769]: I heard: [hello world 263]
[ INFO] [1603376236.827274873]: I heard: [hello world 264]
[ INFO] [1603376236.927204708]: I heard: [hello world 265]
[ INFO] [1603376237.026893929]: I heard: [hello world 266]
- 別タブで実行状況をwatch
$ rosnode list
/listener # これが追加されている
/talker # これが追加されている
$ rostopic list
/chatter # これが追加されている
$ rosrun rqt_graph rqt_graph
# /talker - /chatter -> /listener を確認
$ rostopic type /chatter | rosmsg show
string data
要点
- C++のコードで、トピック(
/chatter
)を作成し、stringのメッセージを配信するコード = talker.cpp を作成して起動できました - C++のコードで、トピック(
/chatter
)を購読し、stringのメッセージを受け取るコード = listener.cpp を作成して起動できました - rosのライブラリ群(catkin_LIBRARIES)を使って処理する部分が多く、半分以上おまじないなので、結構ROSのライブラリを知らないと応用できなそうな予感がします
いったん本記事ではここで終了して、
次回「C++でシンプルなサービスとクライアントを書く」から続きをやってみようと思います。
以上です。
関連する記事
ROS2とPX4の連携環境準備
PX4とROS2の連携を試せる環境をUbuntu20.04で整えました
Ubuntu20.04のサーバーにkubeadmを使って開発用のk8sクラスターを作る
シングルサーバー(Ubuntu20.04)構成でオフィスLAN内に開発用のk8sクラスターを立ててみました
機械学習もできるデスクトップパソコンを自作しました
30万円するGPU(RTX3090)で自作PCを組立て、tensorflowのベンチマークを測ってみました。
[Ubuntu20.04]Gazebo simulator上のDroneをMAVROSを使って動かす
MAVROSを使ったTutorialを実際に動かしてみました