[ODE] applying forces

[Rüdiger Koch]

Hi all,

I am trying to simulate a 6-legged robot. The legs are driven by
hydraulic cylinders which I model with 2 capped cylinders connected by
a slider joint and 2 ball joints at the end.

When I try to apply a force using 
dJointAddSliderForce(dJointID joint, dReal force)
the whole system is getting instable (it's a really spectacular
explosion ;) Now the docs say I am not supposed to apply forces and
that instability is to be expected. Instead I am supposed to use a
motor which, as I understand, is setting a velocity. Now a real
hydraulic cylinder is applying a force, not a velocity. The velocity of
the piston is a function of the oil pressure and whatever is getting
pushed by the piston.

How to get out of this?

Thanks a lot in advance
-Rudiger