ros_msg.pub_key = n.advertise<ri_om::key_info>

这段代码中的 "ros_msg.pub_key" 是一个 ROS 发布者对象，它会发布类型为 "ri_om::key_info" 的消息到 ROS 系统中。这个消息类型是在 ROS 的消息系统中定义的，用来传递关于密钥信息的数据。 "n.advertise" 是一个 ROS 节点对象的方法，用来创建一个发布者对象。

相关问题

#include <ros/ros.h> #include <geometry_msgs/Twist.h> #include <math.h> int main(int argc, char** argv) { ros::init(argc, argv, "turtle_triangle"); ros::NodeHandle node; // 创建一个发布器，用于发布速度消息 ros::Publisher pub = node.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 1000); // 设置循环频率，每秒10次 ros::Rate rate(10); // 初始化速度消息 geometry_msgs::Twist vel_msg; vel_msg.linear.x = 0; vel_msg.linear.y = 0; vel_msg.linear.z = 0; vel_msg.angular.x = 0; vel_msg.angular.y = 0; vel_msg.angular.z = 0; // 设定三角形边长和角度 double side_length = 1.0; double angle = M_PI / 3.0; // 循环绘制三角形 for (int i = 0; i < 3; i++) { // 线速度为正，角速度为0，直行一段距离 vel_msg.linear.x = side_length; pub.publish(vel_msg); double t0 = ros::Time::now().toSec(); double current_distance = 0.0; while (current_distance < side_length) { pub.publish(vel_msg); double t1 = ros::Time::now().toSec(); current_distance = vel_msg.linear.x * (t1 - t0); } // 线速度为0，角速度为正，原地旋转一定角度 vel_msg.linear.x = 0; vel_msg.angular.z = angle; pub.publish(vel_msg); double t2 = ros::Time::now().toSec(); double current_angle = 0.0; while (current_angle < angle) { pub.publish(vel_msg); double t3 = ros::Time::now().toSec(); current_angle = vel_msg.angular.z * (t3 - t2); } // 重置角速度 vel_msg.angular.z = 0; } return 0; }改成循环运行三次

可以将代码修改为：

#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <math.h>

int main(int argc, char** argv) {
    ros::init(argc, argv, "turtle_triangle");
    ros::NodeHandle node;

    // 创建一个发布器，用于发布速度消息
    ros::Publisher pub = node.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 1000);

    // 设置循环频率，每秒10次
    ros::Rate rate(10);

    // 初始化速度消息
    geometry_msgs::Twist vel_msg;
    vel_msg.linear.x = 0;
    vel_msg.linear.y = 0;
    vel_msg.linear.z = 0;
    vel_msg.angular.x = 0;
    vel_msg.angular.y = 0;
    vel_msg.angular.z = 0;

    // 设定三角形边长和角度
    double side_length = 1.0;
    double angle = M_PI / 3.0;

    // 循环绘制三角形，运行三次
    for (int j = 0; j < 3; j++) {
        for (int i = 0; i < 3; i++) {
            // 线速度为正，角速度为0，直行一段距离
            vel_msg.linear.x = side_length;
            pub.publish(vel_msg);
            double t0 = ros::Time::now().toSec();
            double current_distance = 0.0;
            while (current_distance < side_length) {
                pub.publish(vel_msg);
                double t1 = ros::Time::now().toSec();
                current_distance = vel_msg.linear.x * (t1 - t0);
            }

            // 线速度为0，角速度为正，原地旋转一定角度
            vel_msg.linear.x = 0;
            vel_msg.angular.z = angle;
            pub.publish(vel_msg);
            double t2 = ros::Time::now().toSec();
            double current_angle = 0.0;
            while (current_angle < angle) {
                pub.publish(vel_msg);
                double t3 = ros::Time::now().toSec();
                current_angle = vel_msg.angular.z * (t3 - t2);
            }

            // 重置角速度
            vel_msg.angular.z = 0;
        }
    }

    return 0;
}

这样就可以让代码循环运行三次，绘制出三个等边三角形了。

#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 (pose.x - x_start1) { twist_msg.linear.x = 0.0; twist_msg.linear.y = 1.0; twist_pub.publish(twist_msg); // Publish command if(pose.y - y_start>=2.0){ twist_msg.linear.x = -1.0; twist_msg.linear.y = 0.0; twist_pub.publish(twist_msg); // Publish command if(dist<=2.0){ twist_msg.linear.x = 0.0; twist_msg.linear.y = -1.0; twist_pub.publish(twist_msg); // Publish command ROS_INFO("Stop and Completed!"); twist_pub.publish(twist_msg); // Publish command ros::shutdown(); } } } 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; } 这段代码为什么不能实现乌龟沿完整矩形轨迹运动？并给出修改后的代码

这段代码不能实现乌龟沿完整矩形轨迹运动的原因是在判断乌龟是否到达目标点时的条件判断有误。具体来说，代码中的`if (pose.x - x_start1)`应该改为`if (dist >= 2.0)`，来判断乌龟是否到达了目标距离2.0。此外，代码中也缺少了对乌龟角度的控制，需要在适当的时候设置`twist_msg.angular.z`来控制乌龟的旋转。

下面是修改后的代码：

#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;
    twist_msg.linear.y = 0.0;
    twist_pub.publish(twist_msg); // Publish command
    ROS_INFO("Stop and Completed!");
    ros::shutdown();
  }
  
  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;
}

这样修改后的代码会使乌龟沿着矩形轨迹移动，当乌龟到达目标距离2.0时，会停止运动并关闭节点。