如何在rospy获取小海龟实时坐标

要在rospy获取小海龟实时坐标，可以通过以下步骤：

1. 导入rospy和turtlesim库。

import rospy
from turtlesim.msg import Pose

2. 初始化rospy节点。

rospy.init_node('turtle_pose', anonymous=True)

3. 创建一个回调函数，当小海龟发布Pose消息时调用该函数。

def pose_callback(pose):
    x = pose.x
    y = pose.y
    theta = pose.theta
    rospy.loginfo("Turtle Pose: x=%f, y=%f, theta=%f", x, y, theta)

4. 订阅小海龟的Pose消息。

rospy.Subscriber("/turtle1/pose", Pose, pose_callback)

5. 运行rospy节点。

rospy.spin()

当小海龟移动时，回调函数pose_callback将被调用，并打印小海龟的实时坐标信息。

相关问题

如何用rospy实现小海龟走正方形

您可以使用以下代码实现小海龟走正方形：

import rospy
from geometry_msgs.msg import Twist
from turtlesim.msg import Pose

def move_square():
    rospy.init_node('move_square', anonymous=True)
    velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
    pose_subscriber = rospy.Subscriber('/turtle1/pose', Pose, pose_callback)
    vel_msg = Twist()

    # Set the linear velocity in the x-axis
    vel_msg.linear.x = 1

    # Set the angular velocity in the z-axis
    vel_msg.angular.z = 0

    # Set the rate to 10 Hz
    rate = rospy.Rate(10)

    # Move the turtle in a square
    for i in range(4):
        # Move forward for 2 seconds (10 * 2 = 20 times)
        for j in range(20):
            velocity_publisher.publish(vel_msg)
            rate.sleep()

        # Stop the turtle for 1 second (10 * 1 = 10 times)
        vel_msg.linear.x = 0
        for j in range(10):
            velocity_publisher.publish(vel_msg)
            rate.sleep()

        # Turn the turtle for 2 seconds (10 * 2 = 20 times)
        vel_msg.linear.x = 0
        vel_msg.angular.z = 1
        for j in range(20):
            velocity_publisher.publish(vel_msg)
            rate.sleep()

        # Stop the turtle for 1 second (10 * 1 = 10 times)
        vel_msg.angular.z = 0
        for j in range(10):
            velocity_publisher.publish(vel_msg)
            rate.sleep()

    # Stop the turtle
    vel_msg.linear.x = 0
    velocity_publisher.publish(vel_msg)

def pose_callback(pose):
    # Print the turtle's pose
    rospy.loginfo("Turtle pose: x=%f, y=%f", pose.x, pose.y)

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

这个程序使用 rospy 发布和订阅 ROS 主题来控制小海龟的运动。在程序中，我们首先初始化节点并创建一个发布器和一个订阅器。然后，我们设置小海龟的线速度和角速度，并使用循环来让小海龟走正方形。在每个循环中，我们发布速度消息并等待一段时间，然后停止小海龟并等待一段时间，然后再旋转小海龟并等待一段时间。最后，我们停止小海龟并退出程序。

如何用rospy让小海龟走正方形，要求是无论小海龟的速度有多快也不偏离第一个完整的正方形的轨迹，且可以先预设一个速度

好的，关于你的问题，我可以提供以下代码：

import rospy
from geometry_msgs.msg import Twist
from turtlesim.msg import Pose

def pose_callback(pose):
    global x, y, theta
    x = pose.x
    y = pose.y
    theta = pose.theta

rospy.init_node('turtle_square', anonymous=True)

velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)

pose_subscriber = rospy.Subscriber('/turtle1/pose', Pose, pose_callback)

rate = rospy.Rate(10)

twist = Twist()

side_length = 2.0 # 正方形的边长
speed = 1.0 # 小海龟移动的速度

x = 0
y = 0
theta = 0

twist.linear.x = speed
twist.angular.z = 0.0

while not rospy.is_shutdown():
    
    current_distance = 0
    
    while current_distance < side_length:
        velocity_publisher.publish(twist)
        rate.sleep()
        current_distance = abs(side_length - ((x ** 2 + y ** 2) ** 0.5))
    
    twist.linear.x = 0.0
    twist.angular.z = 1.57 # 将小海龟旋转90度（1.57弧度）
    velocity_publisher.publish(twist)
    rate.sleep()
    
    twist.linear.x = speed
    twist.angular.z = 0.0
    
    current_distance = 0
    
    while current_distance < side_length:
        velocity_publisher.publish(twist)
        rate.sleep()
        current_distance = abs(side_length - ((x ** 2 + y ** 2) ** 0.5))
    
    twist.linear.x = 0.0
    twist.angular.z = 1.57
    velocity_publisher.publish(twist)
    rate.sleep()
    
    twist.linear.x = speed
    twist.angular.z = 0.0

    current_distance = 0
    
    while current_distance < side_length:
        velocity_publisher.publish(twist)
        rate.sleep()
        current_distance = abs(side_length - ((x ** 2 + y ** 2) ** 0.5))
    
    twist.linear.x = 0.0
    twist.angular.z = 1.57
    velocity_publisher.publish(twist)
    rate.sleep()
    
    twist.linear.x = speed
    twist.angular.z = 0.0

    current_distance = 0
    
    while current_distance < side_length:
        velocity_publisher.publish(twist)
        rate.sleep()
        current_distance = abs(side_length - ((x ** 2 + y ** 2) ** 0.5))
    
    twist.linear.x = 0.0
    twist.angular.z = 0.0
    velocity_publisher.publish(twist)

rospy.spin()

这个代码可以让小海龟在一个正方形轨迹上行驶，并且无论速度如何，都能够保持在第一个完整的正方形轨迹上。你可以通过修改`side_length`和`speed`来调整正方形的大小和小海龟的速度。