The Return of Lego Avenger

The return of a champion. Okay, let's be more honest. The return of the occasionally competative Lego Avenger is what we're talking about. I'd given up on the old 'bot after its dismal last showing in 2002. The bot to replace it, originally called N-Gen, now called Ginzokubikotchi, didn't happen in 2003, and despite a large amount of effort in the last weeks before the convention, also failed to appear in 2004 due to smoking the onboard computer. So, assuming I can make the old beast go again, and assuming I can get the GNU tool chain to build on OS X - which it should - I'm anticipating bringing Lego Avenger back to the ring at Mile High Con 2005. I'm also bringing it back as a practice bot for Ginzochan 2005 to spar with. Below is Lego Avenger as it sits right now, early in the 2005 development cycle. Yes the sensors are going to be relocated.

Older Lego Avenger Stuff

There are no pictures of the first iteration of Lego Avenger. Below are two pictures of the 2001 model, although the front end was redone before the machine was actually used. At the front of the machine you can see the IR Proximity Detector, provided by Dennis as the prize in the 2000 competition

In 2000, Lego Avenger dominated the field. Admittedly there was only one other competitor, but it was still fun. In 2001, I fielded practically the same machine, except that I added a second motor to each side, and the forward facing proximity sensor that was 2000's prize. As a result of my messing up my gear ratios, I was completely out-torqued by another Lego machine.

So when I set out to build the 2002 (and final) iteration of Lego Avenger, I went to Lynxmotion, a hobby robotics company, to get more powerful motors. These motors can clearly be seen in the pictures below, they're the large brass colored tubes just aft and inboard of the wheels. Integrating them involved a lot of soldering and some light machining to make the couplers to connect the lego gears to the non-lego motors. Without a lathe, this was extremely tedious and difficult work, and they did not come out as well as I'd hoped, although the end product was apparently good enough. I also replaced the proximity sensor with one from Techno-stuff. It not only works the same way (although interfacing it is a little different software wise) but the builder freely admits to basing the design on Dennis's. It is just smaller and better armored - the sensor got fairly badly beaten up in the 2001 competition.

As you can see from the leftmost picture (Lego Avenger is the machine at the bottom right corner of the picture) the chassis was a complete revision from the previous year. This was necessary, because the added weight of the motors put the original chassis considerably overweight. The new chassis was a lightweight assembly of plates, tensile components, and epoxy putty to hold the motors down. The new motors also drew a huge amount of current. This, combined with the need to loose a couple ounces, meant that Lego Avenger was now fueled with lithium photo batteries. A brand new regular set of alkaline batteries lasted about 10 minutes of testing during software development this year. Lithium photo batteries were good for about an hour, at 15 dollars a set.

Between the 2000 and 2001 model years, I also switched from the stock Lego Mindstorms RIS software to LegOS/BrickOS, which allowed me to program the machine in multithreaded C.

2002 was Lego Avenger's final development cycle. It took only second place in 2002 (out of 4 competitors), and this might be reason enough, but I was planning on this change since I began the 2002 development cycle. Adding the non-lego motors made me all the more keenly aware of the limitations of the Lego computer - it's too heavy, it only has 3 sensor inputs, it doesn't sling enough power around for real high powered motors, and so on, and of the limitations of LegOS/BrickOS (The documentation is horrific) as well. So for next year I will be going back to Lynxmotion for parts, as well as materials to build a robot from scratch, controlled by a PIC chip (or several PIC chips) Lego Avenger will undoubtedly be the sparring partner for the new machine, however, and I might just enter it in the competition anyway, just for fun.