The GumBrix article: http://armyofevilrobots.com/node/378

The gumbrix came about because so many of my robot projects required the kind of rapid prototyping that Lego® really excels at, yet required more in the way of control electronics than Lego® was capable of. With a maximum of 3 motors and 3 sensors, the Mindstorms kit was not really capable of the more complicated control strategies that I was interested in. For example, it is possible to build a balancer, but not one with a touch sensor and proximeter as well, and certainly not one with arms. At the same time, custom machining every single part for a balancer is VERY time consuming, and not flexible once assembled.

In retrospect, the solution should have been more obvious. I have built a controller for lego parts that is capable of offering far more processor power, unlimited sensors, and a large number of motors/pneumatics.
The GumBrix Specs:
* Gumstix Waysmall 400MHz Arm7, with bluetooth, 2x serial, I2C, and Linux
* Delrin case with Lego compatible studs and rails
* Custom interface boards with AtMega8 running as an I2C slave
* Modular Jack for interfacing

Belligerator Update:

I ahve rebuilt the entire robot, from the ground up, with better audrature encoders, multiple PID loops, a better rate sensor (combined with the old accelerometer), ATMega32 and a big fat battery ;)

More details on Army of Evil Robots.

The new quadrature encoders have been integrated into a new S3003 futaba servo. I have changed the organization of the sensors, and now get approximately 360 quadrature ticks per revolution (it is actually a little off from that, but who is counting).

I am freezing the physical design, and designing the pcb that will fit inside of the servo container. Servo form factor will be compatible with a standard servo, offer continuous, absolute, 360 absolute, or standard servo functionality, with either a standard PWM input, or a bi-directional RS232 compatible signal, all over a standard 3 pin servo connector (neat trick huh?) Control uses a PID feedback loop, with motor current detection. I hope to have the whole thing tested for 100 hours so that I feel safe publishing the design on my site, before christmas break. Check back at my site for more info.

I have retired my old blog (although it is still online), and my new one (Army of Evil Robots) has a new theme. The new site is based on Drupal, and has the complete archives of my old site online. I have also added many new features.

In other news, I finished my high resolution servo encoder circuitry, and have working quadrature on the Belligerator software too. The servo hack involves a pair of QRD1114 optical sensors placed inside of a hacked standard servo. The sensors pick up the rotation of the secondary gear inside the servo, returning 64 ticks per revolution (per 3.14 mm travel). I am hoping that this is high enough resolution to handle the balancing code. If not, I can easily increase the resolution to 0.95mm. Past that, I need to grow the robot.

I am in the progress of writing a tutorial, and generating schematics for this design, and will be posting them under a creative commons license.

Much progress occured this weekend. The bot is assembled, and the chest plate is manufactured. Arms are attached, and the servos installed too. I just need to finish the forearms.

I received my new Gumstix board this morning too. I have already started customizing it. I need to build a cross compiler suite still though. I am downloading the gumstix toolchain as I write this, but I doubt that it will work on Windows XP without extensive modification (even under cygwin).

At least I have a working Linux laptop at home. ;)