A brief guide to using the Minoru stereo webcam.

http://code.google.com/p/sentience/wiki/MinoruWebcam

It seems to me that this device might be quite useful for robot projects. It wasn't very long ago that such as device would cost a couple of thousand dollars or more.

In addition to the feature based stereo I may also try implementing a dense stereo algorithm. My thoughts on using this as a replacement for the cameras on GROK2 are that the baseline is probably a little on the short side, but that it probably would work.

This weekend I've been experimenting with the Minoru stereo webcam, which I think could turn out to be very useful for robotics purposes.

You can find my review here:

http://streebgreebling.blogspot.com/2009/05/minoru-stereo-webcam-review.html

At the moment I'm still undecided as to whether I'll use the Minoru to replace the existing cameras on GROK2. I've ordered some wide angle lenses which I'll try using. If the new lenses fit then this device might be ideal.

Have done more testing this weekend and fixed some important bugs. It transpired that there was still a "glitch" issue with the direction of one of the encoders reversing seemingly at random, but I've managed to work around that. Also the motion control and joystick servers are now talking together as they should.

I need to write a new utility program which will allow me to visualise the occupancy grids after doing an initial joystick guided training run. This should allow me to check that things look as I expect them to.

I've also ordered one of the Minoru 3D webcams. Apparently these are UVC compliant and will work on Linux. If I can get a pair of images out of the device this would make an excellent replacement for the existing stereo cameras, whilst also solving my V4L1 issues. However, even if the Minoru does look like a usable stereo camera I'll need to assess image quality and field of view compared to the existing cameras which I'm using.

Wheel odometry is now calibrated, and repeatability looks good over short distances, such that the rate of increase in pose uncertainty should be unmanageably small.

I'm getting closer to having a working robot, although there has been a recent setback in that the new version of Ubuntu (9.04) doesn't seem to support the webcams which I'm using. This is odd, because they worked without a hitch in previous versions. A simple solution would be to downgrade the OS, although I'm reluctant to do that. I suspect that there has been some change in the kernel, perhaps related to gspca and V4L1 devices.

As a workaround I've continued development on Windows. This is ok, because the Windows version has not received too much attention and so was lagging behind in some features. My current strategy is to ensure that the robot's software works both on Windows and on Linux in order to maximise the possible range of use cases.

There's some extra work to be done on path integration, and no doubt there will be additional bugs to fix once I start testing on the robot in earnest (as opposed to simulation/unit testing). Both stereo cameras are working and calibrated, and are returning reasonable stereo features. The camera images seem to suffer from occasional glitches, and this might be something to do with their age (most of them were bought 4 years ago) or more likely it could be electrical interference with the USB cables from nearby pan and tilt servos. Either way, the glitches are not sufficiently serious to cause major concern at this point.

I now have both of the stereo cameras calibrated, and am fairly confident that I'm getting good quality disparities, which should at least suffice for navigation purposes. I wrote an extra program which allows me to visualise the stereo disparity and manually alter calibration parameters to observe the effects. Hence, if there are problems I can check the camera calibration more thoroughly than was possible previously.

The next step is to do integration testing with all of the systems running - stereo vision server, motion control server, servo control server, steersman and ultrasonics server. With luck I should be able to create some real maps soon.