imranz30's profile - activity

If there is an implementation or such a script available or some tips as to how to do it will be great for my experiments

I need to run a simulation for 24000 steps in Gazebo and at the end of it I want a new world to load automatically and run the simulation for another 24000 steps. This I want to do for 100 worlds at least. During the simulations I will gather data for analysis.

Hi, Is there a way to load world files from a ros node or script one after the other. I want to create 100 worlds and load them one after the other in the simulation. The task is to move a robot in the world and collect data, then load another world and move the robot in it and collect data and so on for 100 worlds. If there is a way to do it please let me know.

Thanks,

http://answers.gazebosim.org/question...

Solution found and posted on answers.gazebosim.org . So I am closing the question here.

Hello,

I need to reset the world in Gazebo. I know it can be done manually using the Gazebo GUI and doing Ctrl-R but I need to do it programmatically. I have genetic algorithms running in Visual Studio in Windows and I am communicating with ROS mater using rosserial_windows. Now after every generation I need to reset the world since I am evolving controllers for the robot. How and where should I do this?

Thanks,

Hi,

How do we close the connection in rosserial_windows. I do something like this to connect:

ros::NodeHandle nh; char *ros_master = "192.168.0.118:11411"; nh.initNode(ros_master);

Now I need to close the connection, how to do that?

Hi,

Some background I am involved in a project that requires connection between a Visual Studio Application in Windows and ROS/Gazebo in Linux. I have successfully integrated the two applications together. In ROS/Gazebo I have a robot with a Laser Scanner attached which is publishing distance readings which I process and convert to two readings and send over to the Visual Studio Application where those distance readings will be processed further and give out velocity readings which will be sent to the ROS/Gazebo system at cmd_vel topic allowing the robot to move.

My Problem Now my problem is how to make the communication between the two applications run smoothly. I cannot have the following going on in the Visual Studio application to get the data:

ros::NodeHandle nh;
ros::Subscriber<std_msgs::Float64MultiArray> sensor_sub("msg", &sensor_callback);
nh.subscribe(sensor_sub);
while(1)
{
    nh.spinOnce();
    Sleep(100);
}

The problem with the above code is that there is a while(1) loop which always blocks, so I cannot process the data once I get it because while(1) won't let me get out of it. That is problem number 1. My second problem is related with sending twist message to the robot in Gazebo from Visual Studio application which again runs into the same problem of while(1) keeps blocking. Something like the below code:

geometry_msgs::Twist twist_msg;
ros::Publisher cmd_vel_pub("cmd_vel", & twsit_msg);
while(1)
{
   twist_msg.linear.x = x;
   twist.msg.linear.y = y;
   twist.msg.linear.z = z;
   twist.msg.angular.x = ax;
   twist.msg.angular.y = ay;
   twist.msg.angular.z = az;
   cmd_vel_pub.publish(&twist_msg);
   nh.spinOnce();
   Sleep(100);
}

The values x,y,z,ax,ay,az are computed inside the Visual Studio application. This is even a bigger problem since I am using rosserial_windows and it requires sometime to sync with the device in order to receive data packets, at least this is how its working with me.

Now this is a continuous process, I should keep getting new distances and process them and keep sending new velocities to see how the robot moves. The velocity values are computed through a genetic algorithm. So is there an effective way to solve this communication problem.

I will appreciate any pointers or referral links.

Thanks!

Well, I solved the problem. It seemed that the laser scanner had a sampling rate of 720, I changed it to 100 and now I receive the data :)

I created my own laser_scan_publisher node in ros and ran it to publish data on /scan topic. And now when I connect through rosserial_windows I am able to get that data in the terminal. I think then the problem is not with rosserial_windows. What could be the problem then?

I have tried a lot of things with this but I am still unsuccessful. There are errors like "unknown error returned due to write operation: system 104", sometimes the server give errors like "cannot read unknown error". I am using ros jade should I switch to ros hydro, will that change anything.

Hi,

I am rosserial_windows to connect to the ros under windows using ros_lib. I have written the following code to subscribe to the laser scan data but I don't receive anything in the terminal in windows. It connects with the server and just keeps waiting. Here is the code that I wrote:

void laser_scan_callback(const sensor_msgs::LaserScan & msg)
{
    printf("%d",msg.header.seq);
}

int _tmain(int argc, _TCHAR* argv[])
{
    ros::NodeHandle nh;
    char *ros_master = "192.168.0.110:11411";

    printf("Connecting to server at %s\n", ros_master);
    nh.initNode(ros_master);

    ros::Subscriber<sensor_msgs::LaserScan> laser_scan_sub("scan", &laser_scan_callback);
    nh.subscribe(laser_scan_sub);
    printf("Waiting to receive messages\n");

    while(1)
    {
        nh.spinOnce();
        Sleep(1000);
    }

    printf("All done\n");
    return 0;
}

Some more information is below: On the Ubuntu machine I installed the rosserial for jade as "sudo apt-get install ros-jade-rosserial-windows" and "sudo apt-get install ros-jade-rosserial-server". On the ROS computer I am running rosserial_server socket_node command which is listening to port 11411 and I am connecting to that port through non-ROS computer. I don't understand why it doesn't receive scan data. It seems like that the callback function laser_scan_callback is never invoked. I also tried to publish data on a topic and that worked. I published on the topic /cmd_vel and the robot in gazebo moved. But I don't know why I don't receive the data from /scan topic.

Hi,

I have successfully connected ros to a non-ros system using rosbridge-server and roslibjs. I am getting the laser san data in the web client used to connect with the ros system. Now I have to somehow give that data to a Visual Studio Application running in the non-ros system. How can I do it? Do I have to write that laser scan data to a file using Javascript and the web client and then read that file or is there another way to directly get that data inside the Visual Studio Project.

Thanks, Imran