[ros-users] Inconsistant timing issues with powerbot-sh running P2OS

[David Feil-Seifer]

Matt-

I'll take a look at the p2os driver to see if I can pin down the
problems that you're having. The earliest that I will be able to do
this is tomorrow, however.

-Dave

On Wed, Dec 8, 2010 at 12:37 PM, Matt B <fooloftherandom at gmail.com> wrote:
> Both the robot, and my laptop are running the latest version of Cturtle,
> along with the latest version of the p2os node, and have run a few more
> tests, while watching the output (the failsafe node, reports to ros_out when
> either mode is activated or configuration changes are made)
>
> And what I’m seeing is my code sending the commands as expected, when
> expected based on the sonar data itself (both sonar data and the times of
> activation, agree with the previous performance under ARIA libraries) but
> especially in the case of the disable command being sent since an audible
> response from the brakes on the powerbot engaging can be heard, a lag of up
> to ½ a second or so can be heard, between when the failsafe algorithm sends
> the disable command to /cmd_motor_state and when the motor brakes engage.  I
> do expect a less noticeable lag on occasion of up to 100mS due to the way
> the ARCOS controller itself works, but this is well beyond that.
>
>
>
> As for more specific information on each computer, the powerbot is currently
> running ubuntu 9.10 and my laptop is running ubuntu 10.04x64. Without
> modifying the p2os node itself, theres no way I can think of to be able to
> tell whether the lag is coming from our network, the p2os node, or the ARCOS
> controller communication itself.
>
>
>
> Matt
>
> From: Tully Foote [mailto:tfoote at willowgarage.com]
> Sent: Tuesday, December 07, 2010 9:53 PM
> To: User discussions
> Subject: Re: [ros-users] Inconsistant timing issues with powerbot-sh running
> P2OS
>
>
>
> Hi Matt,
>
> Without a lot more information we can't help you much.  Please see
> http://www.ros.org/wiki/Support#Guidelines_for_mailing_list_messages
>
> I would suggest that you put in some debugging statements to make sure that
> the obstacles is being detected.  If you can track down more specifically
> where you think there is a problem and provide a way for us to reproduce the
> problem that would allow us to help you.
>
> Tully
>
> On 12/07/2010 09:20 PM, Matt Bergsma wrote:
>
> Hello;
>
>
>
> Currently working on a Sonar Based ‘failsafe’ object avoidance code, which
> was originally developed and tested in Aria, and since porting it from Aria
> to ros – p2os I have found its gone from behaving as expected to being very
> inconsistent at best, even after increasing its internal parameters so both
> stop and stop/disable zones are significantly larger. I would expect part of
> this would be lag in the subnet the robot and my laptop are connected into,
> but even moving the code onto the powerbot these same issues are occurring.
> Eg. The robot is hitting our test object.
>
> Note – The first set of tests had only the p2os node on the powerbot, and
> roscore, my failsafe code, and a modified version of the teleop_keyboard
> base code from the p2os package running on an hp tm2-2050 laptop, and when
> the code was moved to the powerbot everything except for the teleop code was
> moved to run on the powerbot but not utilizing the local loopback.
>
>
>
> When this code was developed and tested in aria, it behaved as expected, and
> its very light weight (running a simple profile in aria was giving run times
> of around 28s for 1,000,000 sets of readings and decision on all the sonar
> sensors) which ran on the powerbot itself, and the code hasn’t been
> significantly modified, except to talk using the ROS framework to the
> applicable channels. So I would expect it isn’t the issue.
>
>
>
> Hopefully someone can shed some light on the issues encountered.
>
>
>
> Thanks, Matt Bergsma
>
>
>
>
>
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