Encoder Front Page
SRS Home | Front Page | Monthly Issue | Index
Search WWW Search seattlerobotics.org

First WORKSHOP 3D RCX LEGO Challenge
held on April 1, 2000
at the
Pacific Science Center
Seattle, Washington
Steven D. Kaehler (c) 2000

LEGO Bricks are a plastic, toy building-block product that has been around for about fifty years.  Invented by Ole Kirk Christiansen in 1932 and first manufactured in Billund, Denmark in 1949, these colorful little plastic blocks have been in most kids' toy boxes ever since.  They enable children of all ages to express their creativity in two- and three-dimensional form in an infinite variety of ways.  The number of different types of pieces has grown tremendously in recent years making it possible to easily build things I can remember only dreaming about.  Having recently visited LEGOLAND California in Carlsbad (a half hour north of San Diego), I am truly impressed with what can be built with these little bits of interlocking colored plastic.

About two and a half years ago, the LEGO Group introduced the computerized "bricks" called LEGO Mindstorms to the LEGO product line. This development enabled this wonderful building system to delve into the rapidly expanding world of robotics.  This seems to have been a logical direction for the company since their products lend themselves to building robot-like creations.  One of the great things about these products is that one can buy one of these kits in the afternoon, and by evening have a functional robot running around the house.  The LEGO construction of the robot permits things to be changed very quickly and easily and requires no electrical or mechanical expertise.  Changes can be made to add or remove components in minutes without tools.

The programming environment chosen for these products was designed to be as intuitive and easy as the blocks themselves, enabling even young children to quickly pick up on the fundamental concepts of programming and start flying.  These kits, which are now readily available and getting somewhat cheaper as time goes on, have inspired a number of robotic contests that challenge users to accomplish seemingly simple tasks using the stock components.  The Workshop 3D RCX LEGO Challenge is just such a contest.  I attended most of the first one last spring (April 1) at the Pacific Science Center in Seattle, Washington.  What follows is a summary of my experience.

The Long Lost Pictures

The pictures used for this article were taken from the "public observation area" about ten feet from the contest platform with large, bright windows over-illuminating the contest platform from behind.  This made for less than ideal photographic conditions.  Also, they were taken with one of those disposable fixed-focus cameras, developed to film, and scanned to JPEGs so the media quality wasn't the greatest.

The forgotten pictures shown below have been in my disposable camera for about five months waiting for that final one to be taken so they all could finally be developed.  I actually forgot about this camera until we received a bunch of pictures back from the developer.  One nice thing about digital cameras is you don't have to "shoot the entire roll" to view the pictures.  The event was staged at the Pacific Science Center (PSC) in downtown Seattle, right next to their insect exhibit (NE corner of facility) and just outside their new Boeing 3-D IMAX theater.  This map shows the location within the PSC.  Workshop 3D's Ray C. Freeman III hosted the contest and he and six volunteers he recruited set up and ran it. The PSC staff provide tables, ropes, the network connection for the webcast, and other logistical support.

Three contests were staged: Line tracking at 2:00 PM (Figures 1-4), Cube grabbing at 3:00 PM (Figures 5-6), and Puck gathering at 4:00 PM.  I watched the line tracking contest completely and a portion of the cube grabbing contest later in the afternoon, but missed the puck gathering contest because I had to leave.  Each contest lasted a half hour to forty-five minutes after which things broke up until the next contest began.

The pictures below captured some of the events from my viewpoint.  Unfortunately I was not able to get close enough to get any better shots of the robots, however, there is a link to more pictures taken at the contest at the end of this article so read on.

On two sides of the table, two PC video cameras were set up to webcast the events.  Depending on which camera saw the best action, it was selected for the webcast.  If anyone reading this article caught the webcast of this event, let Ray Freeman know how it came across and how he might improve it.

A total of eight robots competed in all the contests and some competed in multiple contests with minor modifications made between them..

Figure 1A & B - This robot (Sweet Streeper) did surprisingly well though he kept spinning around and around when he lost the line. He did eventually finish however.  Note the sharp turns in the line.
Figure 2 - This robot was rather unstable in its following pattern which caused it to literally "dance" down the line.  Even though it used two light sensors to better track the line, it was too touchy to stay on track, wandering off and losing the line above.
Figure 3 - Given the primitive optical sensors of the Mindstorms and RCX modules, this proved to be a very challenging course, especially with the sharp turns.  This proved extremely difficult for all the robots including this one (Seeing Eye).  This robot had its line sensors on a sweeping arm. 
Figure 4 - This robot, "Skeletor", tracked the line down to the checkerboard area around the edges where it became confused.  Ray purposely demonstrated this to show that the robots had limitations.  The robot had two huge eyes (cosmetic only) that you can see looking to the right.
Figure 5 - The object of this contest was be the first to grab or push the green cube off to the side of the arena.  This contest reminded me of our mini sumo qualification runs except that multiple robots competed for the same block.  The SRS could have the mini and larger sumos do this same contest without any mechanical or programming modifications to the robots or the basic contest parameters.
Figure 6 - This robot couldn't find the cube.  It, like most of the robots, simply had to wander around blindly until time ran out or it was lucky enough to bump into the block..  One, however, employed an ingenious use of the built-in IR communication system for long range sensing.  See below.

Among serious robot builders, LEGO Mindstorms controllers are usually considered somewhat limited, and the contest disallowed custom hardware, so creative ingenuity had to make up for the apparent functional deficiency.  Ray Freeman employed a unique approach to the lack of stock "long range sensors" for the cube grabbing contest shown in Figures 5 & 6.  His robot, "Skeletor", shown in Figure 4, used the infrared port on the RCX itself to send a pulsating beacon signal, then used the stock light sensor to detect any up or down spikes (edge of a pulse) in the light reading which would indicate a reflection from the cube. Of course, it could easily have mistaken the other robot for the cube, so the method wasn't foolproof, but it proved good enough to win the event.  Way to go Ray!

This overall event was well attended by many people, some who came to see it and others who just happened to be in the area at the time and saw a crowd.  In fact I bumped into fellow SRS member Jim Wright who had stopped by to check things out.  The people watching seemed to enjoy the antics of the robots and cheered when they succeeded in accomplishing something.  It's funny how the robots can almost seem alive when they do something unexpected, particularly interesting, or just plain funny.  I'm sure this type of event doesn't hurt sales in the PSC Stores either.  A number of vendors donated prizes for the events, and trophies were awarded to the contest winners as well.

The only negative issue I saw was that unless you were near the front of the crowd, seeing the events was difficult.  This is typical for most crowd-oriented events in places where views are blocked by people standing.  Ray says that the next event will probably have video monitors set up so folks toward the back of the crowd and around the area can get a better view of the action without having to be right there.

More pictures from the previous challenge are available in the First RCX LEGO Challenge photo gallery.  I even ended up in a couple pictures.  Wow!  My fifteen minutes (seconds) of glory.

The Second WORKSHOP 3D RCX LEGO Challenge is coming on Saturday, November 4th in the same part of the PSC starting at 1:00 PM.  If you can make it, it's sure to be a crowd pleaser.  In fact, even if you can't make it, you can send Ray your program to run on the Standard Line Tracking Robot on contest day.  Besides, there ought to be some SRS folks in it just to make things interesting.  Hmmm.  Maybe I'll give it a try.

stdrobot.jpg (20611 bytes)

The Standard Line Tracking Robot

Ray C. Freeman III of WORKSHOP 3D Design Studio has challenged his colleagues to build autonomous robots using the LEGO RCX 1.0 microcomputer-in-a-brick, as supplied with both the LEGO Mindstorms product line and the LEGO dacta ROBOLAB product line, and to compete against the clock, in head-to-head events, in group activities, and in exhibition-only events.  For additional information on these events, visit his website at (http://www.workshop3d.com/rcx) or contact Ray Freeman.at rayiii@workshop3d.com.

LEGO, LEGO MINDSTORMS, RCX, and ROBOLAB are trademarks of The LEGO Group. WORKSHOP 3D is a registered trademark of WORKSHOP 3D, Inc.  Their use in this article is non-commercial and for reference only.  The author is not in any way affiliated with the LEGO Group, the Pacific Science Center, or WORKSHOP 3D, Inc.