如何编写ros的python程序

Posted 2023-04-26

参考技术A 1 先建立工作空间~/catkin_ws
下的创建工作空间
catkin_create_pkg basic std_msgs rospy

2 在工作空间~/catkin_ws下创建包pkg目录basic
好处是通过创建包自动生成package.xml和CMakeLists.txt

3 在工程目录下建一个src子目录和.py文件
源代码文件：topic_publisher.py
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#!/usr/bin/env python
import roslib; roslib.load_manifest('basic')
import rospy
from std_msgs.msg import Int32
rospy.init_node('topic_publisher')
pub = rospy.Publisher('counter', Int32)
rate = rospy.Rate(2)
count = 0
while not rospy.is_shutdown():
pub.publish(count)
count += 1
rate.sleep()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
操作步骤如下
liao@liao-eagle:~/catkin_ws$ ls
build devel install src
liao@liao-eagle:~/catkin_ws$ cd src
liao@liao-eagle:~/catkin_ws/src$ ls
basic beginner_tutorials CMakeLists.txt first second
liao@liao-eagle:~/catkin_ws/src$ cd basic/
liao@liao-eagle:~/catkin_ws/src/basic$ ls
CMakeLists.txt package.xml src
liao@liao-eagle:~/catkin_ws/src/basic$ cd src
liao@liao-eagle:~/catkin_ws/src/basic/src$ vi topic_publisher.py
liao@liao-eagle:~/catkin_ws/src/basic/src$ chmod +x topic_publisher.py

4 回到~/catkin_ws目录下，编译程序
$ cd ～/catkin_ws
liao@liao-eagle:~/catkin_ws$ catkin_make

5 将当前工程加入到shell环境里去
liao@liao-eagle:~/catkin_ws$ echo "source ~/catkin_ws/devel/setup.bash" >> ~/.bashrc
liao@liao-eagle:~/catkin_ws$ source ~/.bashrc

6 运行程序（需开两个终端）
liao@liao-eagle:~/catkin_ws$ roscore
liao@liao-eagle:~/catkin_ws$ rosrun basic topic_publisher.py

7 通过rostopic查看相关信息
liao@liao-eagle:~/catkin_ws$ rostopic list
/counter
/rosout
/rosout_agg

liao@liao-eagle:~/catkin_ws$ rostopic info /counter
Type: std_msgs/Int32

Publishers:
* /topic_publisher (h33/)

Subscribers: None

liao@liao-eagle:~/catkin_ws$ rostopic echo /counter
data: 185
---
data: 186
---
data: 187
---
data: 188
---
data: 189
---
data: 190
---
data: 191
---
data: 192
---
data: 193
---
data: 194

ROS 编写自定义消息（Python版）

ROS可以自定义消息类型，可以在节点之间传递自定义消息的类型。
下面以自定义的一个Person消息为例子

• 生成功能包

#cd ~/catkin_ws/src
#catkin_create_pkg learncommunication std_msgs rospy roscpp
#cd ~/catkin_ws/src/learncommunication
#mkdir msg

上面这个过程是在src目录下创建一个名为learncommunicaiton的功能包，如果要创建自定义的消息类型，需要在这个功能包下创建一个名为msg的目录，自定义的消息文件就放在这个目录下。
功能包的目录

自定义一个消息类型文件Person.msg

string name
uint8  age
uint8  sex

uint8 unknown = 0
uint8 male    = 1
uint8 female  = 2

将来生成的消息类的类名就是Person。
在功能包的编译过程中，可以使用msg文件生成不同编程语言使用的代码文件。
要编译msg文件，需要修改CMakeList.txt文件和package.xml文件

• 在package.xml文件中添加功能包依赖

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

• 在CMakeLists.txt中添加编译选项

find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  std_msgs
  message_generation
)

 add_message_files(
   FILES
   Person.msg
 )

 generate_messages(
   DEPENDENCIES
   std_msgs

 )

catkin_package(
 
   CATKIN_DEPENDS roscpp rospy std_msgs message_runtime
 
)

这样自定义消息类的编译选项就做好了

• 编写publisher节点

import rospy
from learncommunication.msg import Person

def velocity_publisher():
    # ROS节点初始化
    rospy.init_node('person_publisher', anonymous=True)

    # 创建一个Publisher，发布名为/person_info的topic，消息类型为learning_topic::Person，队列长度10
    person_info_pub = rospy.Publisher('/person_info', Person, queue_size=10)

    #设置循环的频率
    rate = rospy.Rate(10) 

    while not rospy.is_shutdown():
        # 初始化learning_topic::Person类型的消息
        person_msg = Person()
        person_msg.name = "Tom";
        person_msg.age  = 18;
        person_msg.sex  = Person.male;

        # 发布消息
        person_info_pub.publish(person_msg)
        rospy.loginfo("Publsh person message[%s, %d, %d]",
                person_msg.name, person_msg.age, person_msg.sex)

        # 按照循环频率延时
        rate.sleep()

if __name__ == '__main__':
    try:
        velocity_publisher()
    except rospy.ROSInterruptException:
        pass

在这里使用语句 from learncommunication.msg import Person 来导入自定义的消息类型

• 编写subscriber节点

import rospy
from learncommunication.msg import Person

def personInfoCallback(msg):
    rospy.loginfo("Subcribe Person Info: name:%s  age:%d  sex:%d", 
             msg.name, msg.age, msg.sex)

def person_subscriber():
    # ROS节点初始化
    rospy.init_node('person_subscriber', anonymous=True)

    # 创建一个Subscriber，订阅名为/person_info的topic，注册回调函数personInfoCallback
    rospy.Subscriber("/person_info", Person, personInfoCallback)

    # 循环等待回调函数
    rospy.spin()

if __name__ == '__main__':
    person_subscriber()

• 编译代码

# cd ~/catkin_ws
# catkin_make
# source /dev/setup.bash
# roscore

• 运行代码
  由于是python程序，不需要使用rosrun，直接运行python脚本即可。

python person_publiser.py
python person_subscriber.py

注意要在不同的终端运行两个脚本

脚本运行的效果

• 查看自定义的信息类型
  可以使用rosmsg show 命令来查看Person类型的信息

参考文档

https://www.guyuehome.com/