I began a project with an industrial ro-bot. The goal was more or less the same as with caterpillar, animate the whole thing with as few Ipo(s) as possible. So naturally the position of the arm and the "hand" are driven with an Empty.
But each of the direction (X, Y and Z) of the Empty drives a separate function of the robot.
My problem now, is that I'm far far away from being finished, and I have abso-lutely no time at the moment to work on it. I am not like Andrew Price who is 100% a BlenderGuru,but I will try the following way ;-) Next weeque I will coorganise a Blender-Day in Switzerland (for 10 children), details for which are on Blendernation:
Blender is with me day and night, but I can't do everything at the same time, so If you want to help please reach out to the people and let them know that they can follow the work on the french Blend-erClan.
I have a lot of mechanical tests, but nothing ready to show. So I am providing you a .blend file to play with, which have something like "Advanced PyDrivers Theme".
The principle is to drive constraints with mathematical formula to decompose the only X movement of the Empty "Master" in defined steps.
With this method I can drive a Geneva Drive in real time, and a mechanical differential with a brake system at the same time, by just add-ing a "very simple to rig" a connecting rod with 3 Bones and IK (just bonus).

advanced Py Drivers-1.jpg

Everything is real time, that means no leg in animation while running it at slow, fast, stop, reverse... with every element perfectly synchronised, and playing with only one lonely IPO (LocX).
Blender file is not configured to render a "wow" image or animation, it is just ready to play with Empty Master and observe what happens.
Visuals objects are on layer 11-14, and Armatures and Empties on 1-4.