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b21 Rflex intermittant start and stops on ATRV jr

asked 2011-12-13 05:29:09 -0500

robpan gravatar image

updated 2014-01-28 17:10:59 -0500

ngrennan gravatar image

I am using Rlfex-B21 driver for ATRV jr and publishing the velocity

rostopic pub -1 /b21/cmd_vel geometry_msgs/Twist '[0.8,0,0]' '[0,0,0]'

I am expect that the robot should should continuously move, but it doing move-stop-move at random intervals.

any help?????

rob

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answered 2011-12-14 20:52:59 -0500

michikarg gravatar image

Hi,

we were recently trying to do the same with our B21-robot and by comparing the code with the Player-Stage code from which it was ported from, we found a fix for some hardware-bug. Applying that patch to the ROS-code solved it for us. (see: http://answers.ros.org/question/1863/rflexb21-cmd_vel-not-working-as-expected )

You can get the patch here:

http://ias.cs.tum.edu/~kargm/rflex_driver.patch

and apply it to rflex_driver.cc in your reflex ROS-package. Let me know it this solved it for you.

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answered 2011-12-13 07:03:18 -0500

updated 2011-12-13 07:04:31 -0500

In general when sending command velocities, you need to publish continually, not just once. Try something like:

rostopic pub -r 10 /b21/cmd_vel geometry_msgs/Twist '[0.8,0,0]' '[0,0,0]'

This protects against losing control of the robot when bad things happen (like network interruptions, or controller node crashes).

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Thanks for the reply, I try setting the constant frequency ( 10,20, 100 etc), but same issue. I am just wondering that since i am using telecom port (ttyR0) instead of USB(ttyUSB0) serial, would that be the issue?
robpan gravatar imagerobpan ( 2011-12-14 07:51:20 -0500 )edit
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answered 2011-12-14 07:52:01 -0500

robpan gravatar image

updated 2011-12-14 07:52:48 -0500

Thanks for the reply, I try setting the constant frequency ( 10,20, 100 etc), but same issue. I am just wondering that since i am using telecom port (ttyR0) instead of USB(ttyUSB0) serial, would that be the issue?

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We actually had a look at the code recently and it seems like you don´t have to publish to cmd_vel constantly, since the driver receives the cmd_vel message from ROS and hands it over to the controller that applies it with a constant frequency, so i don´t think that this is the issue...
michikarg gravatar imagemichikarg ( 2011-12-14 20:59:49 -0500 )edit

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Asked: 2011-12-13 05:29:09 -0500

Seen: 401 times

Last updated: Dec 14 '11