[ODE] Rover gets stuck in singular position

[Thomas Thüer]

Hi

I have a problem with my simulation of a 6-wheeled rocker bogie type 
rover. When the rover is moving on a flat terrain towards a step (higher 
than its wheel radius), the rover is stuck as soon as it touches the 
step with its front wheel - which is a singular position. As long as the 
torque applied on the front wheel (with hinge2 addTorques()) is big 
enough, I would expect the rover to climb the step. In order to get out 
of this situation my controller increases the torques on all wheels. 
Even though the slippage value of the contact joints is very low and mu 
set to infinity, the front wheel cannot generate enough traction on the 
vertical wall go get out of the singular situation.
This is a behaviour that I don't understand! For what reason can this 
happen? What settings can I try to change to make the front wheel climb 
the stair?

Thanks for any help,
Thomas