ros2编程控制turtlesim中的小海龟走一个圆、正方形和椭圆形。

### 使用ROS2编程控制`turtlesim`绘制圆形、正方形和椭圆形 在ROS2环境中，可以通过发布速度命令到`turtle1/cmd_vel`主题来控制`turtlesim`中的小海龟移动。以下是实现绘制圆形、正方形和椭圆形的具体方法。 #### 1. 绘制圆形 为了使小海龟画出一个完美的圆，线速度和角速度需要保持恒定的比例关系。以下是一个Python脚本示例： ```python import rclpy from geometry_msgs.msg import Twist def move_in_circle(): rclpy.init() node = rclpy.create_node('move_in_circle') publisher = node.create_publisher(Twist, '/turtle1/cmd_vel', 10) msg = Twist() # 设置线速度 (m/s) 和角速度 (rad/s)，比例决定半径大小 linear_speed = 1.0 angular_speed = 1.0 msg.linear.x = linear_speed msg.angular.z = angular_speed rate = node.create_rate(10) # 发布频率为10Hz try: while True: publisher.publish(msg) rate.sleep() except KeyboardInterrupt: pass msg.linear.x = 0.0 msg.angular.z = 0.0 publisher.publish(msg) if __name__ == '__main__': move_in_circle() ``` 此代码通过设置相同的线速度和角速度实现了匀速圆周运动[^1]。 --- #### 2. 绘制正方形 要让小海龟沿着正方形路径移动，可以交替发送直线前进的速度指令和旋转90度的角度指令。以下是一个示例代码： ```python import rclpy from geometry_msgs.msg import Twist import math def move_in_square(): rclpy.init() node = rclpy.create_node('move_in_square') publisher = node.create_publisher(Twist, '/turtle1/cmd_vel', 10) msg = Twist() side_length = 2.0 # 边长 (米) turn_angle = math.pi / 2 # 转弯角度 (弧度) forward_duration = int(side_length * 10) # 前进时间步数 turn_duration = int(turn_angle * 10) # 转弯时间步数 rate = node.create_rate(10) # 发布频率为10Hz for _ in range(4): # 正方形有四条边 # 向前走 msg.linear.x = 1.0 msg.angular.z = 0.0 for _ in range(forward_duration): publisher.publish(msg) rate.sleep() # 转弯 msg.linear.x = 0.0 msg.angular.z = 1.0 for _ in range(turn_duration): publisher.publish(msg) rate.sleep() msg.linear.x = 0.0 msg.angular.z = 0.0 publisher.publish(msg) if __name__ == '__main__': move_in_square() ``` 该代码利用循环结构完成了四个直角转弯并沿每一边行走固定距离的操作[^2]。 --- #### 3. 绘制椭圆形 对于椭圆形轨迹，可以通过调整线性和角速度的变化率来实现不同的轴长度。下面是一段用于创建椭圆轨迹的代码： ```python import rclpy from geometry_msgs.msg import Twist import numpy as np def move_in_ellipse(): rclpy.init() node = rclpy.create_node('move_in_ellipse') publisher = node.create_publisher(Twist, '/turtle1/cmd_vel', 10) a = 2.0 # 长半轴 b = 1.0 # 短半轴 omega = 0.5 # 角速度因子 t = 0.0 dt = 0.1 rate = node.create_rate(10) # 发布频率为10Hz while rclpy.ok(): x_dot = -a * omega * np.sin(t * omega) theta_dot = b * omega * np.cos(t * omega) / a msg = Twist() msg.linear.x = abs(x_dot) msg.angular.z = theta_dot publisher.publish(msg) t += dt rate.sleep() msg.linear.x = 0.0 msg.angular.z = 0.0 publisher.publish(msg) if __name__ == '__main__': move_in_ellipse() ``` 这段程序基于参数方程定义了椭圆形状，并动态计算每一时刻的小海龟位置变化量。 --- ### 总结 上述三种方式分别展示了如何使用ROS2 API编写节点以完成特定几何图形的绘制任务。这些例子不仅适用于学习基础概念，还能够帮助理解机器人学中常见的运动规划算法原理。