static gait biped with autonomous, gimbal-like spine

[assadollahi]

here's trashbot version three, i added an articulated spine that is intended to counter-balance the lower body's movements of the static gait.
the robot is mostly made from old recycled parts like bike parts, hd-drive holders, and a typewriter, hope you like it!

https://www.youtube.com/watch?v=oIX9gqIgpVE

here's how i made it: http://assadollahi.de/trashbot-3-a-gimbal-like-autonomous-2dof-spine/

if you have any tips how to improve the PID for between the gyro and the servos: i'd love to learn more! that's the current state here:
https://www.youtube.com/watch?v=Nu_97zBNF0A

thanks!