P-hex

p-hex is a hexapod robot, built most from bits of a bioloid kit, scrap metal and assorted pieces of tech, designed to be controlled from an openpandora handheld.


Hardware

The hardware for p-hex consists of 2 scrap plates salvaged from old monitors, and 6 legs, constructed from the parts of a bioloid kit, each with 3 servos.
The servos are all connected to a USB->dynamixel bus adapter, which is in turn connected to a usb hub. The USB hub is required for 2 reasons, 1.The usb port on the openpandora is USB 2.0 only, so needs to be converted to USB 1.1 through the hub to make the adapter work and 2.incase further USB devices require more power than the pandora can provide.

Also attached to the USB hub is a wireless xbox 360 adapter, which will be used for direct control of the robot.

P-hex is powered by an RC car type battery, with a voltage range of about 7-12v for the servos (the pandora has a separate battery).


Software

The software for the robot is at a very early stage, infact P-hex can just about crawl across the floor with a very awkward gait. The main stumbling block with the software is programming some common sense into the inverse kinematics, which at the moment are based on simple trigonometry. Most of the time the computed angles for the servos will cause the legs to move to unexpected locations, luckily the dynamixels are clever enough to include overload protection, so that when something does go wrong and the legs tie themselves in knots it doesn't cause any damage.