Older blog entries for Enki (starting at number 9)

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. ;)

27 Oct 2004 (updated 27 Oct 2004 at 18:07 UTC) »

I have been back into the bots again lately, with a project involving a 2 wheeled balancing robot.

Check my page at http://enki.cthuugle.com/archives/cat_robots.php

I am also going to be using my new gumstix board to control the visual system!

Check for updates soon, because I just finished the entire upper body assembly.

Blech..... Weeks of simple net programming have reduced my brain to mush. Still, the worst of it is over, and it looks like I may have access to the CNC machine some time in the near future. More robot plans to follow.....

28 May 2001 (updated 28 May 2001 at 19:03 UTC) »

Well, I found some interesting code on the internet for a serial driven servo controller, for up to 8 servos, on a single pic 16c54A ucontroller. Kickass. Unfortunately, there was no schematics, circuit board, or anything else for the thing. Not that that is really a problem.

I have built the schematics and pc-board for the controller, and managed to squash the whole thing into a 1.65" x 1.95" space. Just supply 6 volts and you are good to go. I will be posting the entire thing on my site at RantTV later on today. I tested on a breadboard, but I still need to test the actual board, so don't build it just yet eh?

The code itself (written by Mark Sullivan, available at http://www.markwo rld.com/servo1.asm) is capable of running 8 servos, off of a 9600 bps 8n1 serial port. It can run up to 19,200 or down to 300 bps. This should help me get my legs moving.

14 May 2001 (updated 27 Oct 2004 at 18:06 UTC) »

Well, I headed on down to the alleged meeting of the Vancouver Robotics Club on Sunday. 10:00am came, then 10:30, then 11:00.....

No members.

Lot's of other people who were curious about the club came out, and we talked for a bit about what we were all doing, but in the end, no members. So we left. I took down all the non-members emails and I am hoping to form a Vancouver Robotics Club splinter faction ;)

Hmm, what to post... I have some interesting ideas for control systems, especially a feedback motion control system that allows for sub-millimeter positioning and very high speed using a pneumatic cylinder. I have used this system to great effect for an automotive application. I have wanted to play with it for a leg actuator for a while now, but never have enough time. Drop me a line through my homepage if you are interested in learning more...

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