task 2

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The turtlesim package in ROS Noetic is a great tool for learning and experimenting with ROS concepts. It provides a simple simulation environment where you can control a turtle to move around and perform various actions. Here’s a quick guide on how to get started with turtlesim:

Installation

Make sure you have ROS Noetic installed on your system. You can install turtlesim using:

sudo apt-get install ros-noetic-turtlesim

Launching Turtlesim

To start the turtlesim node, use the following command:

roslaunch turtlesim turtlesim_node.launch

This command launches the turtlesim GUI and starts the turtle simulator.

Controlling the Turtle

To control the turtle, you can use the turtle_teleop_key package which provides keyboard control:

rosrun turtle_teleop turtle_teleop_key

Basic Commands

Here are some basic commands you can use to interact with turtlesim:

1. Move Forward:

   rostopic pub /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 0.0]'

2. Turn:

   rostopic pub /turtle1/cmd_vel geometry_msgs/Twist -- '[0.0, 0.0, 0.0]' '[0.0, 0.0, 1.0]'

3. Set Position:

   rosservice call /turtle1/setx 5.0 rosservice call /turtle1/sety 5.0

4. Clear the Screen:

   rosservice call /clear

   Custom Nodes

You can write custom nodes in Python or C++ to interact with turtlesim. Here’s an example in Python:

python

!/usr/bin/env python

import rospy from geometry_msgs.msg import Twist

def move_turtle(): rospy.init_node('turtle_mover', anonymous=True) pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10) rate = rospy.Rate(10)

move_cmd = Twist() move_cmd.linear.x = 2.0 move_cmd.angular.z = 1.0

while not rospy.is_shutdown(): pub.publish(move_cmd) rate.sleep()

if name == 'main': try: move_turtle() except rospy.ROSInterruptException: pass

Make sure to give execute permissions to your script:

chmod +x your_script.py

And then run it:

rosrun your_package your_script.py

Visualization Tools

You can also use tools like rqt_graph to visualize the topics and nodes in your ROS system:

rqt_graph

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Manipulate with turtlesim package in ROS2 foxy.

To manipulate the turtlesim package in ROS 2 Foxy, you'll need to follow several steps. turtlesim is a great way to get started with ROS 2, as it provides a simple 2D simulation environment where you can control a turtle and see its movements. Here’s a basic guide to help you get started:

1. Install ROS 2 Foxy Make sure you have ROS 2 Foxy installed on your system. If you haven’t installed it yet, you can follow the official installation guide.

2. Install turtlesim To install the turtlesim package, you can use the ROS 2 package manager:

sudo apt update sudo apt install ros-foxy-turtlesim

3. Launch turtlesim Start the turtlesim node using the following command:

ros2 run turtlesim turtlesim_node

This will launch the turtlesim simulation, and you should see a window with a turtle on it.

4. Control the Turtle You can control the turtle by publishing to the /cmd_vel topic. To do this, you can use the ros2 topic pub command. For example:

ros2 topic pub /cmd_vel geometry_msgs/msg/Twist '{linear: {x: 1.0}, angular: {z: 1.0}}'

This command will publish a message to the /cmd_vel topic that moves the turtle forward and rotates it.

5. Writing a Python Node If you want to write a Python script to control the turtle, you can create a ROS 2 package and write a node that publishes to /cmd_vel. Here’s a simple example:

1. Create a ROS 2 package:

   ros2 pkg create --build-type ament_python my_turtle_package

2. Navigate to your package directory:

   cd my_turtle_package

3. Create a Python script:

   Inside the my_turtle_package/my_turtle_package directory, create a file named turtle_controller.py:

   import rclpy from rclpy.node import Node from geometry_msgs.msg import Twist

   class TurtleController(Node): def init(self): super().init('turtlecontroller') self.publisher = self.create_publisher(Twist, '/cmd_vel', 10) self.timer = self.create_timer(0.5, self.timer_callback)

   def timercallback(self): msg = Twist() msg.linear.x = 1.0 msg.angular.z = 1.0 self.publisher.publish(msg) self.get_logger().info('Publishing: "%s"' % msg)

   def main(args=None): rclpy.init(args=args) turtle_controller = TurtleController() rclpy.spin(turtle_controller) turtle_controller.destroy_node() rclpy.shutdown()

   if name == 'main': main()

4. Update setup.py** to include your new script:

   from setuptools import setup

   package_name = 'my_turtle_package'

   setup( name=package_name, version='0.0.1', packages=[package_name], data_files=[ ('share/ament_index/resource_index/packages', ['resource/' + package_name]), ('share/' + package_name, ['package.xml']), ], install_requires=['setuptools'], zip_safe=True, maintainer='your_name', maintainer_email='your_email@example.com', description='A package for controlling turtlesim', license='License', tests_require=['pytest'], entry_points={ 'console_scripts': [ 'turtle_controller = my_turtle_package.turtle_controller:main' ], }, )

5. Build and run your package:

   colcon build source install/setup.bash ros2 run my_turtle_package turtle_controller

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