Groundhog Day

Posted 28 May 2003 at 14:00 UTC by steve Share This

In August of last year, after the Quecreek mine accident, US Senators called for robots that could map mines. Mining engineers claimed the idea was "impossible" and "ridiculous". By November, CMU had completed the first test of Groundhog, an autonomous mine mapping robot. Groundhog can take photos, make 2D maps, 3D maps and 3D animations. Examples can be found on CMU's website. This Friday, Groundhog will take on its hardest test yet: mapping a 3,500-foot corridor in an abandoned coal mine near West Elizabeth, PA. More details about the development of Groundhog can be found in this Carnegie Mellon Magazine article.

mapping software, posted 28 May 2003 at 16:37 UTC by josborn » (Journeyer)

Does anybody know how their mapping software works? I wish they'd explain that better, there are hardly any technical details on the site. There are two ways to make a map (that I can think of) from a robot. First is to use wheel encoders to give you your absolute position and then overlay your laser data (they're using a SICK laser/ladar) on that. The problem is that wheel encoders won't be completely accurate, and that inaccuracy adds up the farther you go. The way to get around that is to find some feature, like a corner, that is easy to locate and you relate your data back to that point. This is the harder way, but more accurate if you do it right.

Does anyone know how CMU is doing it? If not, what other sorts of mapping software have people written using similar sensors?

Accuracy, posted 28 May 2003 at 17:59 UTC by guad13 » (Observer)

They probably don't have complete accuracy, just more accuracy than previous maps. My guess is that they did use wheel encoders. A lot of the inaccuracy in wheel encoders can be eliminated with some redundancy in the sensory. It would be far to hard to make reference to a common point like a corner in this situation. You would have to have multiple points all along the mine and know the distances between those points which may not be hard in an ideal situation. I don't know what your experience of being in a mine is but from my experiences there are times where there isn't a place that you could make reference to a point time after time.

Another idea would be to place some kind of beacon every so often on the wall or ceiling of the mine and use these as reference points. But this method would add far to much complexity to the system in my opinion.

Body similar to University of Alberta's Polar Bear, posted 28 May 2003 at 20:38 UTC by onnimikki » (Master)


Neat application. We built a similar-looking robot at the University of Alberta back in 1998/99 for use in the IGVC and for a geophysical company. It was called Polar Bear, was powered by a gas engine and instead of the relatively complicated transmission used on Groundhog, used hydraulic motors. We used it to track and follow people outdoors (eventually with video in addition to SONAR)

Videos (1), (2) and (3) of Polar Bear in action are available. Also, there are a bunch of photos here.

You can read up on Polar Bear by reading my thesis (available on my McGill webpage). A technical report is available at the IGVC website.

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