Hello!

I need to make a sketchup like the GroundBot:
http://www.rotundus.se/
http://www.youtube.com/watch?v=KXXNM2A-h34
http://www.youtube.com/watch?v=kB_esizySdI

It has two servo motors, one moves the pendulum-wheight forward and backward, and the other moves right and left.
"A controlled pendulum keeps the center of gravity very close to the inside surface of the sphere. At rest, the center of gravity is close to the ground. To create momentum, a built-in motor raises the pendulum. This changes the center of gravity and GroundBot begins to roll in the direction that the pendulum has been moved."

can I build such model with SU Physics and control it?
I tried but I couldn't do it.

thank you for your help!