ROS2使用Python开发动作通信

1.创建接口节点

cd chapt4_ws/

ros2 pkg create robot_control_interfaces --build-type ament_cmake --destination-directory src --maintainer-name "joe" --maintainer-email "[e-mail]"

mkdir -p src/robot_control_interfaces/action
touch src/robot_control_interfaces/action/MoveRobot.action

# Goal: 要移动的距离
float32 distance
---
# Result: 最终的位置
float32 pose
---
# Feedback: 中间反馈的位置和状态
float32 pose
uint32 status
uint32 STATUS_MOVEING = 3
uint32 STATUS_STOP = 4

修改package.xml

  <depend>rosidl_default_generators</depend>
  <member_of_group>rosidl_interface_packages</member_of_group>

修改CMakeLists.txt
find_package(rosidl_default_generators REQUIRED)

rosidl_generate_interfaces(${PROJECT_NAME}
  "action/MoveRobot.action"
)

编译节点

colcon build --packages-select robot_control_interfaces
 

2.创建Python Action节点

cd chapt4_ws/

ros2 pkg create example_action_rclpy --build-type ament_python --dependencies rclpy robot_control_interfaces --destination-directory src --node-name action_robot_02   --maintainer-name "joe" --maintainer-email "[e-mail]"

# 手动再创建action_control_02节点文件
touch src/example_action_rclpy/example_action_rclpy/action_control_02.py

import rclpy
from rclpy.action import ActionClient
from rclpy.node import Node
# 导入Action接口
from robot_control_interfaces.action import MoveRobot

class ActionControl02(Node):
    """Action客户端"""

    def __init__(self, name):
        super().__init__(name)
        self.get_logger().info(f"节点已启动：{name}!")
        self.action_client_ = ActionClient(self, MoveRobot, 'move_robot')
        self.send_goal_timer_ = self.create_timer(1, self.send_goal)

    def send_goal(self):
        """发送目标"""
        self.send_goal_timer_.cancel()
        goal_msg = MoveRobot.Goal()
        goal_msg.distance = 5.0
        self.action_client_.wait_for_server()
        self._send_goal_future = self.action_client_.send_goal_async(goal_msg,
                                                                     feedback_callback=self.feedback_callback)
        self._send_goal_future.add_done_callback(self.goal_response_callback)

    def goal_response_callback(self, future):
        """收到目标处理结果"""
        goal_handle = future.result()
        if not goal_handle.accepted:
            self.get_logger().info('Goal rejected :(')
            return
        self.get_logger().info('Goal accepted :)')
        self._get_result_future = goal_handle.get_result_async()
        self._get_result_future.add_done_callback(self.get_result_callback)

    def get_result_callback(self, future):
        """获取结果反馈"""
        result = future.result().result
        self.get_logger().info(f'Result: {result.pose}')

    def feedback_callback(self, feedback_msg):
        """获取回调反馈"""
        feedback = feedback_msg.feedback
        self.get_logger().info(f'Received feedback: {feedback.pose}')

def main(args=None):
    """主函数"""
    rclpy.init(args=args)
    action_robot_02 = ActionControl02("action_control_02")
    rclpy.spin(action_robot_02)
    rclpy.shutdown()
 

#手动创建机器人类robot.py
touch src/example_action_rclpy/example_action_rclpy/robot.py

 

#!/usr/bin/env python3

import time
# 导入rclpy相关库
import rclpy
from rclpy.node import Node
from rclpy.action import ActionServer
from rclpy.action.server import ServerGoalHandle
# 导入接口
from robot_control_interfaces.action import MoveRobot
# 导入机器人类
from example_action_rclpy.robot import Robot
#from rclpy.executors import MultiThreadedExecutor
#from rclpy.callback_groups import MutuallyExclusiveCallbackGroup

class ActionRobot02(Node):
    """机器人端Action服务"""

    def __init__(self,name):
        super().__init__(name)
        self.get_logger().info(f"节点已启动：{name}!")

        self.robot_ = Robot()

        self.action_server_ = ActionServer(
            self, MoveRobot, 'move_robot', self.execute_callback
            # ,callback_group=MutuallyExclusiveCallbackGroup()
        )

    def execute_callback(self, goal_handle: ServerGoalHandle):
        """执行回调函数,若采用默认handle_goal函数则会自动调用"""
        self.get_logger().info('执行移动机器人')
        feedback_msg = MoveRobot.Feedback()
        self.robot_.set_goal(goal_handle.request.distance)

        # rate = self.create_rate(2)
        while rclpy.ok() and not self.robot_.close_goal():
            # move
            self.robot_.move_step()
            # feedback
            feedback_msg.pose = self.robot_.get_current_pose()
            feedback_msg.status = self.robot_.get_status()
            goal_handle.publish_feedback(feedback_msg)
            # cancel check
            if goal_handle.is_cancel_requested:
                result = MoveRobot.Result()
                result.pose = self.robot_.get_current_pose()
                return result
            # rate.sleep() # Rate会造成死锁，单线程执行器时不能使用
            time.sleep(0.5)

        goal_handle.succeed()
        result = MoveRobot.Result()
        result.pose = self.robot_.get_current_pose()
        return result

        
def main(args=None):
    """主函数"""
    rclpy.init(args=args)
    action_robot_02 = ActionRobot02("action_robot_02")
    # 采用多线程执行器解决rate死锁问题
    # executor = MultiThreadedExecutor()
    # executor.add_node(action_robot_02)
    # executor.spin()
    rclpy.spin(action_robot_02)
    rclpy.shutdown()
 

touch src/example_action_rclpy/example_action_rclpy/robot.py

from robot_control_interfaces.action import MoveRobot
import math

class Robot():
    """机器人类，模拟一个机器人"""

    def __init__(self) -> None:
        self.current_pose_ = 0.0
        self.target_pose_ = 0.0
        self.move_distance_ = 0.0
        self.status_ = MoveRobot.Feedback

    def get_status(self):
        """获取状态"""
        return self.status_

    def get_current_pose(self):
        """获取当前位置"""
        return self.current_pose_

    def close_goal(self):
        """接近目标"""
        return math.fabs(self.target_pose_ - self.current_pose_) < 0.01

    def stop_move(self):
        """停止移动"""
        self.status_ = MoveRobot.Feedback.STATUS_STOP

    def move_step(self):
        """移动一小步"""
        direct = self.move_distance_ / math.fabs(self.move_distance_)
        step = direct * math.fabs(self.target_pose_ - self.current_pose_) * 0.1
        self.current_pose_ += step  # 移动一步
        print(f"移动了：{step}当前位置：{self.current_pose_}")
        return self.current_pose_

    def set_goal(self, distance):
        """设置目标"""
        self.move_distance_ = distance
        self.target_pose_ += distance  # 更新目标位置

        if self.close_goal():
            self.stop_move()
            return False

        self.status_ = MoveRobot.Feedback.STATUS_MOVEING  # 更新状态为移动
        return True

编辑package.xml

  <depend>robot_control_interfaces</depend>

编辑setup.py

    'action_robot_02 = example_action_rclpy.action_robot_02:main',
    'action_control_02 = example_action_rclpy.action_control_02:main'

3.编译、运行节点
colcon build --packages-up-to example_action_rclpy

# 运行机器人节点
source install/setup.bash 
ros2 run example_action_rclpy  action_robot_02

# 新终端
source install/setup.bash 
ros2 run example_action_rclpy  action_control_02