OpenHexapod

This is a hexapod robot based on OpenSCB, an open source servo controller. All code and schematics will be provided under an open source license. It's still a work in progress but a lot of internal code has been done already.

The hardware is based on a MSR-µBug, which is a tiny hexapod structure from Micromagic Systems + 18x Mystery SD90 servos which are the cheapest servo I have seen so far. When the first prototype works correctly, I may move to something more robust, probably custom-built. Fitting the SD90 servos in the MSR-µBug wasn't an easy task. The frame is not designed for these cheap servos, so I had to shorten some plastic pieces with my dremel. The SD90 are wearing out pretty quickly, already 4 of them had their gears broken, so they are probably a bit too cheap for an hexapod.

The board is running realtime translation and rotation matrix for body orientation, and a 3 DoF inverse kinematic algorithm on each leg, all of them implemented with efficient fixed point arithmetic. The board receives commands from a RC receiver, which had been hacked to get the PPM signal. Four channels are mixed together to drive the hexapod, I can alternate between several modes with a switch on the radio.

When it moves around, it uses a dynamic "tripod gait" algorithm, each tripod is translated and rotated for every step corresponding to channels mixing. In the end, the IK does the magic and place each leg at the correct position.