I've been working on a new bot for the past couple of months. I finally conquered a software bug last night, and with no anticipated barriers to completion in the way now... I present this new bot, which I dub 'Twitch'! Before I blab on, here is the current level of progress:
My inspiration is the TicTac6 robot by Amino-San. It uses 3 servos, moves quickly, and was an instant must-build when I saw the video back in January.
What I'm using:
-3 AX-12A servos
-2 Pololu Wixel MCUs with built-in wireless capabilities
-TriState Buffer board with a Sparkfun Level Converter to interface/power the Wixel and servos
-1050 mAh 3-S LiPo battery
-3-S LiPo battery monitor
-3D printed parts, bioloid brackets, 3/16" Delrin plate, .03" Polycarbonate sheet, etc.
-Arbotix Commander (modified to interface with a Wixel; documenting thread...)
This is a prototype. I have no idea if the AX-12A is going to be strong enough, and I will likely end up building an MX-28T version of Twitch eventually. It will be interesting to see how much payload capacity it has. Were it to qualify for Mech Warfare (which it shouldn't), it'd probably need at least MX-64's to handle all of the guns/camera/scoring stuff.
So that initial picture... shows the three servos and the 4-bar linkage, actuated in the middle of one of the links that makes this configuration work. I still need to (finalize the) design and print the brackets (one of them is done and visible above) that will mount the "feet," as well as actually design the feet. My plan is to get software going, create a stand so the bot is off the ground, attach flimsy cardboard feet cutouts, and then figure out an optimal design from there. Test feet might be done from Delrin initially, and then get some polycarbonate (1/4" thick?) waterjetted/laser cut.
In addition to the inherent neatness of a capable 3 servo walker, I grant myself awesome points for the custom electronics setup. The Wixel is a cheap TI chip-based board (~45 MHz) with built in wireless communication (not compatible with xBees/zigbee/bluetooth/wifi). The Wixel plus interface board is nice and small. I've not seen a smaller setup that does both wireless and (hardware-based) Dynamixel communication... though I suspect Upgrayd has something like this in the pipeline.
The Wixel uses the SDCC toolchain for software. I modified Upgrayd's AVR Dynamixel libraries (with a bit of code from WebbotLib thrown in) in order to interface the Wixel with AX-12s. Took me a while to get it right. Work in progress code is on Github.
With just three servos, I reckon the battery should be good for at least half an hour.
Other pictures: (click to embiggen)