[ODE] Self Righting Boxes (on castors)

[Ed Jones]

Hi Folks,

I'm building a "simulation" which consists of a load of boxes on castors 
which I can push around (don't ask!).

The boxes are (fairly obviously) boxes and the castors are 4 spheres 
attached to each box with ball joints. I can click on the boxes to give 
them forces and hence push them around the floor. Which is just a ground 
plane, with other boxes and spheres on it. So far so good.

The "castorbox people" fall over quite regularly, which is fine and all 
part of the "fun". But what I'd like to do is, after a couple of seconds 
of lying down, get them to spring back up to their feet of their own 
accord. Obviously I can just reset the little fella to be the right way 
up but I'd like it to look more like they're jumping back up themselves.

Anyone got any ideas of what would be a good (and preferably simple!) 
way to achieve this?

Cheers,
Ed.