Complicated Robot Leg Rig Help!
 

Hi! This is a model I made and the articulations on it limit me to have a simple rig. I have been trying for days to rig this properly, but I never get there. I've tried a couple of things, I got good results but only for certain poses, I had lots of limits. Please help me figure it out this rig!!!

I just need the foot to stay still when I move the root, just like a human rig.

http://farm8.staticflickr.com/7234/7...48802e3d_b.jpg