jaimerv's profile - activity

Hello everyone,

I am trying to use Navigation stack with the Khepera III robot, using its IR sensors as a "laser" and the Optitrack System as "odometry". My intention is to use several robots in order to create a testbed. In order to do so, I've developed a driver in ROS that communicates with Khepera through the UDP protocol in ROS Groovy.

The problem I am having is that the IR sensors are not much better than going blind. When two robots drive towards each other (more or less the game of chicken XD), the collision is impossible to avoid.

I am currently working in two different ways to solve this. The first one includes the ultrasound sensors that the robots include. This has proven not to work.The problem is that there is an important blind zone between the IR sensors and the US sensors.

The second one is to create a node that subscribes to all robots poses and publishes them as inflated_obstacles. It would subscribe these:

/khepera0/pose

/khepera1/pose

/khepera2/pose

etc

My first doubt is if this is the right approach or not.

For creating the obstacle, I've used as GridCell the perimeter of a 15*15cm square around the robot (which is a cillinder of 7cm of radius). My second doubt is if this is correct.

And, lastly, my third doubt is: where should I publish the obstacle? Currently I am publishing the obstacle here:

/khepera0/move_base/NavfnROS/NavfnROS_costmap/inflated_obstacles

/khepera0/move_base/global_costmap/inflated_obstacles

/khepera0/move_base/local_costmap/inflated_obstacles

It does not seem to work. Any ideas?

Thank you in advance.

Hi Angel, i am dealing with the same problem. Apparently the communication between MATLAB and ROS is unidirectional http://www.mathworks.fr/matlabcentral... so MATLAB can communicate with ROS, but not the other way around. i am looking for some solutions, and so far i have found this https://alliance.seas.upenn.edu/~meam... but not sure if it will work,

Let me know if you find a proper solution, greets, Jaime

UPDATED: okey i found the solution. There is a difference when you lauch the roscore from terminal and when you do it from MATLAB. Following the next steps worked for me:

1) edit your .bashrc and add these lines:

export ROS_HOSTNAME=localhost

export ROS_MASTER_URI=http://localhost:11311

2) from terminal : roscore

3) now try again the communication with the subscriber from MATLAB. It should now work.

Greets, Jaime

There is a dot missing in the second tutorial.

From your workspace, run: ~/catkin_ws$ ./devel/lib/testbot_description/parser ./src/testbot_description/urdf/my_robot.urdf

It worked for me.