ROS下turtle3环绕移动的turtle2时距离偏差问题求助

我尝试让turtle2以半径2、角速度1环绕静止的turtle1，同时让turtle3以半径0.5、角速度2环绕turtle2，但turtle3会因为turtle2的移动产生距离偏差，无法稳定环绕。附上我的ROS代码及运行效果截图，求技术帮助。

#!/usr/bin/env python  
import roslib
roslib.load_manifest('learning_tf')
import rospy
import math
import tf
import geometry_msgs.msg
import turtlesim.srv

if __name__ == '__main__':
    rospy.init_node('turtle_tf_listener')

    listener = tf.TransformListener()

    rospy.wait_for_service('spawn')
    spawner = rospy.ServiceProxy('spawn', turtlesim.srv.Spawn)

    # wait for the world to spawn
    rospy.sleep(0.3)

    (trans, rot) = listener.lookupTransform('/world', '/turtle1', rospy.Time(0))
    r2 = 2
    w2 = 1
    # spawn second turtle along the orbit of the first still turtle
    spawner(trans[0], trans[1] - r2, 0, 'turtle2')
    turtle_vel2 = rospy.Publisher('turtle2/cmd_vel', geometry_msgs.msg.Twist,queue_size=1)

    # wait for second turtle to spawn
    rospy.sleep(0.3)
    (trans, rot) = listener.lookupTransform('/world', '/turtle2', rospy.Time(0))
    r3 = 0.5
    w3 = 2
    # spawn third turtle along the orbit of the second turtle
    spawner(trans[0], trans[1] - r3, 0, 'turtle3')
    turtle_vel3 = rospy.Publisher('turtle3/cmd_vel', geometry_msgs.msg.Twist,queue_size=1)

    rate = rospy.Rate(10.0)
    while not rospy.is_shutdown():
        flag2 = True
        flag3 = True
        try:
            (trans, rot) = listener.lookupTransform('/world', '/turtle1', rospy.Time(0))
        except (tf.LookupException, tf.ConnectivityException, tf.ExtrapolationException):
            flag2 = False

        if(flag2):
            angular2 = w2
            linear2 = w2 * r2
            cmd2 = geometry_msgs.msg.Twist()
            cmd2.linear.x = linear2
            cmd2.angular.z = angular2
            turtle_vel2.publish(cmd2)
        
        try:
            (trans, rot) = listener.lookupTransform('/turtle3', '/turtle2', rospy.Time(0))
        except (tf.LookupException, tf.ConnectivityException, tf.ExtrapolationException):
            flag3 = False

        if(flag3):
            angular3 = w3
            linear3 = w3 * r3
            cmd3 = geometry_msgs.msg.Twist()
            cmd3.linear.x = linear3
            cmd3.angular.z = angular3
            turtle_vel3.publish(cmd3)

        rate.sleep()

内容的提问来源于stack exchange，提问作者A_Pumpkin