ROS机器人turtlesim画圆轨迹的简单Python代码？

以下是画圆轨迹的简单Python代码：

import rospy
from geometry_msgs.msg import Twist
from math import pi

rospy.init_node('turtle_circle', anonymous=True)
velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
vel_msg = Twist()

# 设置线速度和角速度
speed = 2
angle_speed = 2

# 计算圆的半径和周长
radius = 1
circumference = 2 * pi * radius

# 计算需要运行的时间
time = circumference / speed

# 设置角速度
vel_msg.angular.z = angle_speed

# 计算需要旋转的角度
angle = speed * time / radius

# 设置线速度
vel_msg.linear.x = speed

# 计算需要运行的距离
distance = speed * time

# 发布速度消息
current_distance = 
current_angle = 
t = rospy.Time.now().to_sec()
while current_distance < distance:
    velocity_publisher.publish(vel_msg)
    t1 = rospy.Time.now().to_sec()
    current_distance = speed * (t1 - t)
while current_angle < angle:
    velocity_publisher.publish(vel_msg)
    t2 = rospy.Time.now().to_sec()
    current_angle = angle_speed * (t2 - t1)

# 停止机器人
vel_msg.linear.x = 
vel_msg.angular.z = 
velocity_publisher.publish(vel_msg)