[ros-users] Questions about VSLAM

Anh Nguyen nguyenminhanh at gmail.com
Wed Nov 3 21:29:24 UTC 2010


Thanks Abe,

I am currently looking at a monocular visual odometry algorithm:
http://www.hessmer.org/blog/2010/08/17/monocular-visual-odometry/

I will probably port it to C and integrate with ROS.

Best,

-M.A


On Wed, Nov 3, 2010 at 12:16 AM, Abe Bachrach <abachrach at gmail.com> wrote:

> Since they are not synchronized, it will probably be equivalent to just
> connecting 2 standard webcams. (probably won't work)
>
> For ~$400 you can get 2 pt-grey firefly MV cameras, and synchronizing them
> shouldn't be that hard...
>
> you can either:
> 1) Use a PIC or other digital signal source to trigger both cameras using
> their external trigger capability
> or
> 2) connect the GPIO pin on one of the cameras to the external-trigger pin
> on BOTH. (this only requires a jumper "cable between" the two cameras)
>
> -=Abe
>
> On Mon, Nov 1, 2010 at 12:46 AM, Kurt Konolige <konolige at willowgarage.com>wrote:
>
>> Anh, I'm not sure if it will work, since I haven't tried it.
>>
>> Cheers --Kurt
>>
>> On Thu, Oct 28, 2010 at 1:03 PM, Anh Nguyen <nguyenminhanh at gmail.com>
>> wrote:
>> > Thanks again Kurt,
>> > Do you know if this Minoru setup will work with vslam? I remember
>> reading
>> > somewhere on ROS wiki that the timestamp from the two camera should be
>> > exactly the same, and it is said on the Minoru project website that
>> those
>> > two webcams are not synchronized.
>> > Best,
>> > -M.A
>> >
>> >
>> > On Thu, Oct 28, 2010 at 2:07 PM, Kurt Konolige <
>> konolige at willowgarage.com>
>> > wrote:
>> >>
>> >> M.A., I remember this link for a stereo webcam:
>> >>
>> >> http://code.google.com/p/sentience/wiki/MinoruWebcam
>> >>
>> >> Reasonable baselines for indoors are 6 - 10 cm; wide-angle lenses also
>> >> help.
>> >>
>> >> Cheers --Kurt
>> >>
>> >> On 10/28/2010 11:21 AM, Anh Nguyen wrote:
>> >>>
>> >>> Hi Kurt,
>> >>>
>> >>> Thanks for the helpful answers. Look like cheap stereo vision is not
>> an
>> >>> easy option, especially with my limited hardware skill.
>> >>>
>> >>> Can you extrapolate a bit more on augmenting VSLAM with odometry or
>> >>> IMUs. I have the odometry reading for my robot. How do I configure
>> VSLAM
>> >>> to work with one camera and combine odometry / IMU with VSLAM (what
>> >>> would be a simple algorithm for that)?
>> >>>
>> >>>  From what I read, I also assume that IMU would work indoor, is that
>> >>> correct?
>> >>>
>> >>> Also, if I go with stereo camera,is there any requirement regarding
>> the
>> >>> baseline, resolution, frame rate... for making it work with existing
>> >>> VSLAM stack?
>> >>>
>> >>> Best,
>> >>>
>> >>> -M.A
>> >>>
>> >>>
>> >>> On Thu, Oct 28, 2010 at 1:08 AM, Kurt Konolige
>> >>> <konolige at willowgarage.com <mailto:konolige at willowgarage.com>> wrote:
>> >>>
>> >>>    M.A. -
>> >>>
>> >>>    VSLAM currently works only with stereo cameras.  VSLAM with
>> monocular
>> >>>    cameras is much less robust, unless it is augmented with other
>> sensors
>> >>>    such as odometry or IMUs.
>> >>>
>> >>>    Using two webcams to make a stereo pair is difficult.  You have to:
>> >>>
>> >>>    1. Make sure they're rigidly mounted
>> >>>    2. Synchronize them
>> >>>
>> >>>    Synchronization is difficult for standard webcams.  At the moment I
>> >>>    don't think there are any cheap off-the-shelf stereo cams.  Here's
>> one
>> >>>    reference for a do-it-yourself:
>> >>>
>> >>>    http://sszymczy.rootnode.net/index.php?menu=projects
>> >>>
>> >>>    It would be nice to do some kind of VSLAM on the Create using
>> odometry
>> >>>    to help, but that would take some work.
>> >>>
>> >>>    Cheers --Kurt
>> >>>
>> >>>    On 10/27/2010 9:46 PM, Anh Nguyen wrote:
>> >>>     > Hi everyone,
>> >>>     >
>> >>>     > I have a few questions about VSLAM. I am new to robotics and
>> most
>> >>>    of its
>> >>>     > terminologies so I would appreciate any references that may
>> >>>    explain the
>> >>>     > background needed to understand your answer :)
>> >>>     >
>> >>>     > - Can I use ROS VLSAM stack using only one camera (a webcam on
>> my
>> >>>     > netbook to be more specific).
>> >>>     > - If so how do I configure VSLAM to get this to work?
>> >>>     > - If not, can I add another external webcam and use them as a
>> >>> stereo
>> >>>     > video system or do I have to purchase some commercial stereo
>> >>>    camera? If
>> >>>     > I have to purchase a commercial system, is there any  good one
>> for
>> >>> <
>> >>>     > $400 range?
>> >>>     >
>> >>>     > Has anyone tried to get VSLAM to work with iRobot Create? I
>> spent
>> >>> the
>> >>>     > last few weeks creating a reduced version of the PrairieDog
>> stack
>> >>>    that
>> >>>     > work without the laser range finder and the stargazer, and
>> mapped
>> >>> my
>> >>>     > office using the robot's bumper sensor, only to realize that I
>> >>> cannot
>> >>>     > rely solely on the robot's encoders for accurate localization.
>> >>>     >
>> >>>     > Thanks a lot,
>> >>>     >
>> >>>     > -M.A
>> >>>     >
>> >>>     >
>> >>>     >
>> >>>     > _______________________________________________
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