[ros-users] Wifi communication getting slow

[Steven Bellens]

Hey,

2011/1/4 Dan Lazewatsky <dlaz at cse.wustl.edu>:
> Hi Steven -
> I've noticed similar problems on a few of our robots, mainly when using
> image_transport to send video over wifi. To figure out if wifi is the
> problem, there are two things I've found helpful: before starting any of the
> code running, from your workstation, ping the robot and see if the ping time
> increases. The other thing you can try is watching iwconfig on the robot to
> see if the link quality deteriorates over time.
> Unfortunately, I never really figured out what was going on. Replacing the
> wifi cards in the affected computers seemed to solve the problem.
> -Dan

I've figured out the problem occurs the moment I start running the
navigation stack. I've been able to build a map using gmapping
(running the gmapping mode on the groundstation), and the ping
responses were constantly okay. When I start up navigation without a
pre-build map (amcl - move base - gmapping), the ping responses
suddenly increase (from 2 - 8 ms to 1000+ ms). When I try the same
with a static map, everything goes well. Am I doing something wrong in
this setup, e.g. can I run amcl and gmapping at the same time? If not,
how should I run the navigation stack without a prebuild map?

Another problem I face is about the navigation: the holonomic robot
localizes itself OK, but the goals I send with rviz only manage to let
it rotate (there is never a translational velocity command), so the
robot starts rotating, but never gets anywhere close where I want him
to go :). Any ideas on that?

regards,

Steven

regards,

Steven

>
> On Tue, Jan 4, 2011 at 9:15 AM, Steven Bellens
> <steven.bellens at mech.kuleuven.be> wrote:
>>
>> Hi,
>>
>> when using ROS to command a mobile base, I'm running a hokuyo_node and
>> an orocos component node on the mobile base. On my workstation I have
>> the navigation stack running, which gets laserscan data from the
>> hokuyo node and sends velocity commands to the orocos component. I
>> only switched to use the wireless network recently and noticed that,
>> after running the app for some minutes, it looks like some delay
>> starts to build up: when I drive the robot with the teleop_keyboard,
>> after 2 minutes, it starts reacting very slow on my input commands.
>> What's the best way to determine if the Wifi is indeed the problem
>> and, if so, can I run this more optimally with ROS considering this
>> restriction?
>>
>> regards,
>>
>> Steven
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>
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