Maxwell Lives!
Or more precisely, Maxwell communicates and walks!
It took about an hour of cable switching and software diddling, but I finally managed to get my desktop computer talking to Maxwell via the serial cable. I could see the serial port at the operating system level, but the Parallax software didn't seem to see it. I decided to brute force it by manually entering port numbers until it saw the Basic Stamp. I entered port 1 as my first input, and like magic everything started working.
From that point on every thing went very smoothly. I built a couple of simple circuits on the BOE breadboard, just to make sure that things were working, then tried to hook up the Parallax servo. At first the servo plug wouldn't fit into the socket. On close inspection I found that there was still a small plastic stub on the servo connector, probably left from the manufacturing process. A little plastic trimming, and the plug went into the socket like a breeze.
I started with the servotest program exactly as it is described in the manual, and it worked fine - which was very encouraging. Then I switched over to the Rogue Robot supplied servos that will be used to drive the wheels. Of course I proceeded very carefully - testing each servo by itself before I developed a confidence level that it was all going to work out okay.
A few minutes later I had both of the wheels going - first just spinning in the air, then later walking on the ground and/or dining table. From that point it was a piece of cake to get Maxwell moving around the desktop. First just one wheel, then both moving together - forward, backward, clockwise, counter clockwise.
Download Maxwell001.wmv (200k)
Scaling the Micromouse to the real world
I spent some time in a toy store yesterday looking at some of the model vehicles and thinking about how they scale to their real counterparts. Of course I started to wonder about how some of the top micromouse competitors would scale to the real world, so I did some back of the envelope calculations comparing Itani-san's MM3 mouse and the new Citroen C4.
MM3 | C4 | Ratio | |
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|
| |
Length (mm) | 130 | 4,260 | 32.77 |
Height (mm) | 52 | 1,458 | 28.04 |
Width (mm) | 60 | 1,773 | 29.55 |
A rough scale factor would seem to be 30:1. When MM3 won the 2002 All Japan Micromouse competition it raced across 75 cells with 37 turns at an average speed of 1,508 mm/sec. Scaling that up it corresponds to a real world speed of 162 kph (101 mph). Imagine driving a race car at 160 kph over a course that's only 400 meters long but includes 37 right angle turns with very little clearance. Really breath-taking performance.
One Step Forward, Two Steps Back…
Some days you get the bear, and some days the bear gets you. Earlier this week I made great progress with Maxwell and it looked like everything was coming together. The initial unpacking, inventorying, and assembly had very few problems.Then I hit the wall.
My initial thought was to do all of Maxwell's software development on my desktop system upstairs. It has about 180 gigabytes of networked storage that I can access from my laptop downstairs, and is relatively fast. Like all of my current PCs, it runs the Japanese versions of Windows, and, since it's a little over three years old, it's running Windows 2000 instead of XP. It's a Sony Vaio and includes a lot of Vaio specific bells and whistles, so I'm very hesitant to upgrade the operating system, as much as I would like to do it.
Everything should have worked fine, but...
In order to talk to the Parallax BOE (Maxwell's brain), I tried using an old USB to serial adapter cable that I had used years ago to interface to a serial printer I used to own. My PC recognized the new hardware/cable, but for some reason didn't have the driver installed. It turns out that the original manufacturer of my adapter cable had been taken over by Xircom, and then Xircom was bought out by Intel... After a lot of searching I managed to locate what appeared to be the right Windows 2000 driver, but when I tried to install it my system kept giving me the same old error message.
Then I tried a brand new adapter cable that I purchased from a PC parts shop near the office. Same problem even with the new adapter and a new driver down-loaded from their website. So, I decided to move Maxwell and the rest of the stuff downstairs and try again using my laptop.
This was deja vu all over again. My laptop runs Windows XP, but didn't like the adapter cable any more than it's desktop cousin upstairs did. I tried various permutations and combinations, and only managed to raise my blood pressure and frustration. Finally, about 1:00 am in the morning, I shut everything down and decided not to work on it again until I got some sleep and could tackle the problem with a clear head.
Last night I didn't have any free time to dig into the connection problem, but I did manage to quickly pull my desktop system away from the wall and confirm that it has a built-in RS-232 port. Tonight or tomorrow I'll try connecting Maxwell up that way. It's not the optimum approach since it means that only my desktop system will be able to talk to Maxwell, but if it works at least it will get Maxwell up and running. Sooner or later I'll have to fix the core problem though if I want to communicate with Maxwell and his children (yet to be conceived) outside of my home office.
Robot Soccer
A number of different groups, including some folks at the Silicon Valley Homebrew Robotics Club, are working on robots that can play soccer. The problem presents numerous challenges, and it will probably be a long time before we see robots capable of competing totally under their own power and control. But, for those of us that aren't willing to wait, and don't mind a few compromises, a company in Japan is marketing a "Capsule Robot Soccer Game - Mr. Soccer."
The robot players are controlled by humans (like you and I) via 27 MHz units - so, basically it's a re-engineered RC car approach. The robots have drive wheels, but are also equipped with legs and feet that stick out in front to kick the ball. They do a pretty good imitation of running down the field with their little legs pumping like crazy. The remote controls have left, right, forward, backward, and a neat kick mode I played with a set in the store, and had a lot of fun with it. The manufacturer's list price in Japan is 5,985 yen - (just under USD$60). They have a promotional video at http://www.b-brave.co.jp/sub2/MR.SOCCER-PV.WMV.
The robot soccer set is already in distribution in Japan, and can be purchased at the Takara "Garage" store in the Coredo building in Nihonbashi.
My initial idea for hacking it would be to leave the robots alone and hack the controls. One thought would be to have a camera mounted directly over the playing field with an interface into the computer to track the robots and the ball. The field and ball colors would probably have to be changed so that the computer can easily identify and follow them....
MicroMouse Speed
I was blown away extremely impressed by the speed of the top competitors during the recent MicroMouse competition in Tokyo. They weren't just fast, they were lightening fast, "faster than a speeding bullet" fast. I took a number of videos during the competition, and it was really hard to keep up with them. I had to use fixed focus because when I let my camera use it's auto focus function the video was blurred because the the focus couldn't keep up with the mouse.
There were, of course, slower competitors. Some of them just trundled along at their own pace. I'm not putting them down, not at all. The fact that they were able to navigate the maze is a major accomplishment by itself no matter how fast they were going.
When I first got interested in the MicroMouse competition I assumed that the major challenge would be exploring the maze and optimizing the best path. Naively I thought that the speed attempts would be interesting, but not necessarily the key to winning. After spending two days watching the actual competition and thinking about what I observed, I'm coming to the conclusion that the top competitors have very good exploration and analysis algorithms, and, more importantly, have spent an extreme amount of effort to shave hundreds of a second off their speed attempts. They are really what the Japanese refer to as 'takumi' - skilled craftsmen.
So, how did this evolve over time? That's going to take considerable research and analysis to figure out. The rules and the maze structure haven't undergone any major change during the 25 years that the competition has been taking place. The available technology has certainly improved very dramatically. And since the contest format has remained constant there was the opportunity for the accumulated knowledge to increase year after year. This may have been the most significant factor.
As time permits, I want to go back and look at the mouse design evolution over the years. For example, many of the mouse photo's I've found on the internet worldwide show designs with sensor arrays that extend over the walls and read the maze that way. Yet there were only a few of that type taking the field in Tokyo. All of the top competitors used design approaches that were down inside the maze.
I did manage to locate some of the performance statistics for the competition from its beginning in 1980 through last years (2003) event. At the initial event in 1980 no competitor was able to successfully complete the maze. In 1981 the winner navigated the course at an average speed of 189 mm/sec. Last year's winner managed an average speed of 1,609 mm/sec, getting very close to 10X the 1981 velocity.
I put together the chart below showing the way the winning speed (red) has increased over the years. I also included the path length in # of cells (green) and the number of turns (blue). Of course, the relative maze complexity is difficult to compare from year to year - at least I'm not sure how to tackle it yet. I'm also very curious about the drop off in speed from 1993 till 1997.
How much faster can they go? What new, innovative design approaches will be required? What is the asymptotic limit? Who will be the first to build a Mighty Mouse that can literally fly through the maze like Luke Skywalker flying in the canyons of the Death Star?
It's going to be fun to find out.... 
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