#include <ros/ros.h> #include <turtlesim/Pose.h> #include <geometry_msgs/Twist.h> #include <std_srvs/Empty.h> #include <cmath> ros::Publisher twist_pub; void poseCallback(const turtlesim::Pose& pose) { static bool is_forward = true; static int count = 0; static float x_start = pose.x; static float y_start = pose.y; static float theta_start = pose.theta; // Calculate distance from starting points float dist = std::sqrt(std::pow(pose.x - x_start, 2) + std::pow(pose.y - y_start, 2)); geometry_msgs::Twist twist_msg; twist_msg.linear.x = 1.0; twist_msg.linear.y = 0.0; twist_msg.linear.z = 0.0; twist_msg.angular.x = 0.0; twist_msg.angular.y = 0.0; twist_msg.angular.z = 0.0; // Check if turtle has reached distance of 2. If so, stop and shutdown the node. if (dist >= 2.0) { twist_msg.linear.x = 0.0; ROS_INFO("Stop and Completed!"); twist_pub.publish(twist_msg); // Publish command ros::shutdown(); return; } twist_pub.publish(twist_msg); // Publish command } int main(int argc, char** argv) { ros::init(argc, argv, "lab1_node"); ros::NodeHandle nh; twist_pub = nh.advertise<geometry_msgs::Twist>("turtle1/cmd_vel", 1); ros::Subscriber pose_sub = nh.subscribe("turtle1/pose", 1, poseCallback); // reset the turtlesim when this node starts ros::ServiceClient reset = nh.serviceClient<std_srvs::Empty>("reset"); std_srvs::Empty empty; reset.call(empty); ros::spin(); // Keep node running until ros::shutdown() return 0; }请问该程序如何修改可使得乌龟按照正方形轨迹运行

要使乌龟按照正方形轨迹运行，你需要对代码进行修改。以下是修改的建议：

1. 在poseCallback函数中，添加一个新的静态变量来跟踪乌龟移动的边数和当前边的长度。例如：

static int side_count = 0;
static float side_length = 0.0;

2. 在计算距离的代码后面，添加以下代码来检查是否达到了一个边的长度：

// Check if turtle has reached the length of a side
if (dist >= side_length) {
  twist_msg.linear.x = 0.0;
  twist_msg.angular.z = 1.57; // Rotate the turtle by 90 degrees
  side_count++; // Increment the side count
  
  if (side_count % 4 == 0) {
    ROS_INFO("Stop and Completed!");
    twist_pub.publish(twist_msg); // Publish command
    ros::shutdown();
    return;
  }
  else {
    // Move the turtle forward again
    is_forward = true;
    x_start = pose.x;
    y_start = pose.y;
    theta_start = pose.theta;
    dist = 0.0;
  }
}

3. 在main函数中，添加以下代码来设置边的长度：

// Set the length of each side
side_length = 2.0;

这样修改后，乌龟将按照正方形轨迹运行，每条边的长度为2.0。当乌龟完成四个边时，程序将停止并关闭节点。请记得在发布命令之前将twist_msg.linear.y和twist_msg.linear.z设置为0.0，以确保乌龟只沿着x轴移动。