小乌龟编队

### ROS中的小乌龟编队编程实现 在ROS环境中，`turtlesim` 是一个用于学习和测试的简单仿真工具。通过 `ros2 pkg executables turtlesim --full-path` 命令可以获取到与 `turtlesim` 节点相关的可执行文件列表[^1]。这些节点提供了基本的功能支持，例如键盘控制、轨迹绘制以及模仿其他海龟的行为。 #### 编程实现小乌龟编队 为了实现多个小乌龟之间的协同运动（即编队），可以通过以下方式完成： 1. **创建自定义Action消息** 需要在功能包目录下创建一个新的 `action` 文件夹并定义动作消息。例如，在 `turtleMove.action` 中定义目标位置、反馈信息以及最终结果的消息结构[^2]。以下是具体代码示例： ```plaintext # Define the goal float64 turtle_target_x # Specify Turtle's target X position float64 turtle_target_y # Specify Turtle's target Y position float64 turtle_target_theta # Specify Turtle's orientation --- # Define the result float64 turtle_final_x # Final X position after movement float64 turtle_final_y # Final Y position after movement float64 turtle_final_theta # Final orientation after movement --- # Define a feedback message float64 present_turtle_x # Current X position during motion float64 present_turtle_y # Current Y position during motion float64 present_turtle_theta # Current orientation during motion ``` 2. **设计控制器逻辑** 控制器负责计算每个小乌龟的目标位置，并发送相应的速度指令给它们。假设我们希望两个小乌龟保持固定距离，则需要实时监控其相对位置并通过比例积分微分 (PID) 控制调整速度。 3. **发布 Twist 消息** 使用 `/cmd_vel` 主题向各个小乌龟发布线性和角速度命令。Python 实现如下所示： ```python import rclpy from geometry_msgs.msg import Twist from turtlesim.srv import Spawn, Kill from std_srvs.srv import Empty def move_turtle(publisher, linear_velocity, angular_velocity): msg = Twist() msg.linear.x = linear_velocity msg.angular.z = angular_velocity publisher.publish(msg) def main(args=None): rclpy.init(args=args) node = rclpy.create_node('controller') pub1 = node.create_publisher(Twist, '/turtle1/cmd_vel', 10) pub2 = node.create_publisher(Twist, '/turtle2/cmd_vel', 10) while True: move_turtle(pub1, 1.0, 0.5) # Move first turtle forward with slight turn move_turtle(pub2, 0.8, -0.3) # Second turtle moves differently if __name__ == '__main__': main() ``` #### 图形绘制算法 对于单个小乌龟来说，常见的绘图操作包括画正方形、圆形或其他几何形状。以画正方形为例，可通过周期性改变方向来完成此任务。下面是 Python 的实现版本： ```python import rclpy from geometry_msgs.msg import Twist import time def draw_square(publisher): twist_msg = Twist() for _ in range(4): # Loop four times to form square edges. twist_msg.linear.x = 2.0 # Set speed along x-axis. twist_msg.angular.z = 0.0 # No rotation initially. start_time = time.time() while time.time() - start_time < 2: # Duration of straight line segment. publisher.publish(twist_msg) twist_msg.linear.x = 0.0 # Stop moving forwards. twist_msg.angular.z = 1.5708 # Turn by pi/2 radians (~90 degrees). start_time = time.time() while time.time() - start_time < 1: # Time taken to rotate fully. publisher.publish(twist_msg) if __name__ == "__main__": rclpy.init() node = rclpy.create_node('square_drawer') cmd_pub = node.create_publisher(Twist, 'turtle1/cmd_vel', qos_profile=10) try: draw_square(cmd_pub) finally: node.destroy_node() rclpy.shutdown() ``` 以上脚本会指挥一只虚拟的小乌龟按照指定的速度前进一段距离后再旋转一定角度重复四次形成闭合矩形轮廓[^1].