ros代码每次运行效果不一致，不报错，但是没有按照要求去执行

xiaosifeipangi

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

int main(int argc, char *argv[])
{
    ros::init(argc, argv, "vel_ctrl");  
    ros::NodeHandle n;         
    ros::Publisher vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
    ROS_INFO("draw_circle start...");

    static double rotationDuration = 1.75;
    static ros::Time startTime;
    static double during=3.5;
    startTime=ros::Time::now();

    ros::Rate loop_rate(10); // Control the loop frequency to 10Hz

    while((ros::Time::now()-startTime).toSec()<=during)
    {
    	geometry_msgs::Twist vel1_cmd;
    	vel1_cmd.linear.x=0;
    	vel1_cmd.angular.z=-0.5;
    	vel_pub.publish(vel1_cmd);
        loop_rate.sleep(); // Sleep for the rest of the cycle to maintain the loop frequency
    }
    
    for(int i=1;i<=2;i++)
    {
      startTime = ros::Time::now();  
      if(i==2)
      rotationDuration = 1.8;
      else
      rotationDuration = 1.75;

      while((ros::Time::now() - startTime).toSec() <= rotationDuration)
      {
         geometry_msgs::Twist vel_cmd; 

         vel_cmd.linear.x = 1.5/i;
         vel_cmd.linear.y = 0.0;  
         vel_cmd.linear.z = 0.0;

         vel_cmd.angular.x = 0;
         vel_cmd.angular.y = 0;
         vel_cmd.angular.z = 1.8; 
         vel_pub.publish(vel_cmd); 
         loop_rate.sleep(); // Sleep for the rest of the cycle to maintain the loop frequency
      }
     }
     
     for(int i=1;i<=2;i++)
    {
      startTime = ros::Time::now();  
       if(i==2)
       rotationDuration = 1.8;
       else
       rotationDuration = 1.75;

      while((ros::Time::now() - startTime).toSec() <= rotationDuration)
      {
         geometry_msgs::Twist vel_cmd; 

         vel_cmd.linear.x = 0.75*i;
         vel_cmd.linear.y = 0.0;  
         vel_cmd.linear.z = 0.0;

         vel_cmd.angular.x = 0;
         vel_cmd.angular.y = 0;
         vel_cmd.angular.z = -1.8; 
         vel_pub.publish(vel_cmd); 
         loop_rate.sleep(); // Sleep for the rest of the cycle to maintain the loop frequency
      }
     }
     ros::Duration(5.0).sleep(); 
     
     startTime=ros::Time::now();
     
     rotationDuration=1.75;
     
     while((ros::Time::now() - startTime).toSec() <= rotationDuration)
      {
         geometry_msgs::Twist vel_cmd; 
         vel_cmd.linear.x = 1.5;
         vel_cmd.linear.y = 0.0;
         vel_cmd.linear.z = 0.0;

         vel_cmd.angular.x = 0;
         vel_cmd.angular.y = 0;
         vel_cmd.angular.z = -1.8; 
         vel_pub.publish(vel_cmd); 
         loop_rate.sleep(); // Sleep for the rest of the cycle to maintain the loop frequency
      }
      
    return 0;
}

正常是画一个太极图，多次运行代码可能可以画多个正常的，也可能像图中这样乱画，而且感觉有时候运行代码突然特别卡。ubuntu20.04，ros：noetic

机器人小伊

你的ROS代码中存在一些问题和潜在的改进点，这些问题可能导致行为不一致和性能问题。以下是一些关键的问题和建议：

1. 错误的HTML实体编码

在你的代码中，你使用了HTML实体编码（如<代替<）来编写C++代码，这在C++编译器中是不被识别的。你需要将这些替换为标准的C++语法。

2. 线程和同步问题

虽然ROS通常使用单线程模型，但你的代码在逻辑上可能存在同步问题，特别是如果你在不同的节点或不同部分中共享或修改全局变量（如startTime和rotationDuration）。在你的例子中，这些变量被静态声明，并且每次循环都重新赋值，这可能导致一些意外的行为，特别是如果ROS节点被重新启动或异常终止。

3. 性能问题

如果ROS网络或节点之间存在高延迟或负载，ros::Rate的sleep()调用可能会导致节点无法及时响应。此外，如果你的计算机资源不足（如CPU或内存），也可能导致性能问题。

4. 逻辑问题

你的代码中有多个循环，每个循环都设置不同的速度和旋转时间。如果这些参数设置不当，或者与其他ROS节点（如turtle simulator）的交互存在延迟，可能会导致不稳定的行为。

5. 改进后的代码

下面是一个修改后的代码示例，修正了HTML实体编码问题，并做了一些小的逻辑调整：

#include "ros/ros.h"
#include "geometry_msgs/Twist.h"

int main(int argc, char *argv[])
{
    ros::init(argc, argv, "vel_ctrl");
    ros::NodeHandle n;
    ros::Publisher vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
    ROS_INFO("draw_circle start...");

    static double rotationDuration = 1.75;
    ros::Time startTime;
    static double during = 3.5;

    ros::Rate loop_rate(10);

    // 初始旋转
    startTime = ros::Time::now();
    while ((ros::Time::now() - startTime).toSec() <= during)
    {
        geometry_msgs::Twist vel_cmd;
        vel_cmd.linear.x = 0;
        vel_cmd.angular.z = -0.5;
        vel_pub.publish(vel_cmd);
        loop_rate.sleep();
    }

    // 两次不同的直线和旋转
    for (int i = 1; i <= 2; i++)
    {
        startTime = ros::Time::now();
        rotationDuration = (i == 2) ? 1.8 : 1.75;

        while ((ros::Time::now() - startTime).toSec() <= rotationDuration)
        {
            geometry_msgs::Twist vel_cmd;
            vel_cmd.linear.x = (i == 1) ? 1.5 : 0.75;
            vel_cmd.angular.z = 1.8;
            vel_pub.publish(vel_cmd);
            loop_rate.sleep();
        }

        startTime = ros::Time::now();
        rotationDuration = 1.75;

        while ((ros::Time::now() - startTime).toSec() <= rotationDuration)
        {
            geometry_msgs::Twist vel_cmd;
            vel_cmd.linear.x = (i == 1) ? 1.5 : 0.75;
            vel_cmd.angular.z = -1.8;
            vel_pub.publish(vel_cmd);
            loop_rate.sleep();
        }
    }

    ros::Duration(5.0).sleep();

    // 最后的旋转
    startTime = ros::Time::now();
    rotationDuration = 1.75;

    while ((ros::Time::now() - startTime).toSec() <= rotationDuration)
    {
        geometry_msgs::Twist vel_cmd;
        vel_cmd.linear.x = 1.5;
        vel_cmd.angular.z = -1.8;
        vel_pub.publish(vel_cmd);
        loop_rate.sleep();
    }

    return 0;
}

6. 调试建议

确保ROS网络正常运行，没有其他节点干扰。
使用`rostopic echo /turtle

以上为生成回答，仅供参考～