Today I finished the new design for the body. I began to use iDraw for this project, and until now it has been a very positive aquaintance. I used to be a competent Illustrator user, but jumped of the Adobe wagon some years ago. iDraw fells very familiar and stay out off my way.
You can download the pattern here: FelixBodyPattern.svg
To test the dimensions and the range of movements, I cut the pieces from 4mm plywood using the pattern as a template, then put it all together using bolts and washers.The servos are fastened with 3mm. bolts and the knee with 2mm. Below you can se af video of the assembly process.
I run a bit out of steam while tinkering with the gaits. The write/compile/upload/test cycle on the Arduino took some of the fun out of it. For the new leg I have to rewrite the IK and control to accommodate the new servo’s setup. So instead of doing this as Arduino sketches, I decided to give NodeBots (http://nodebots.io) and Johnny-Five (https://github.com/rwaldron/johnny-five) a try.
Furthermore Johnny-Five have an Animation module (https://github.com/rwaldron/johnny-five/wiki/Animation) that looks like a perfect fit for managing Felix’s walking cycles.
Lately I have had some time to revisit Felix’s leg design. I wanted to experiment with a simplified version without linkages to increase movement precision. A positive side effect of this, is that by moving half the servos closer to ground I can rely on less powerful servos (HiTEC HS-422).
Another step to increase precision (and repeatability) is to move from an aluminium (hand made) based hardware to laser-cut acrylic. I’ll be posting SVG files of the design as I move along.
I don’t have a Laser Cutter at home, the leg on the picture was made with my scroll-saw to test the geometri and basic movement. Once I’m happy with it, I’ll borrow one at my local Fablab (http://valby.copenhagenfablab.dk).