SNOW VEHICLE OVER A SNOW TERRAIN - MODELI NG THE INTERACTION

A snow vehicle is modelled as a system of rigid bodies interconnected by rotational and translational joints, springs and dampers. A system of differential equations D.A.E. with algebraic constraints, is solved for vertical plane motion using the method of generalized coordinates with partitioning. The system is submitted to gravity, contact forces and moments resulting from the integration of the sinkage pressure di stribution over the vehicle skis and track. A pressure sinkage relatio nship based on the McCullough model is assumed, wherein nonlinear sink age pressure and penetration velocity depending terms are considered. The snow pressure is assumed to be transmitted through the track to th e rail. The skis and the rail are discretized into small segments over the straight and curved portion of their span. Terrain profile of var ious shapes may be considered as the pressure due to variable sinkage is integrated. Results for a cosine shape of terrain profile are prese nted, wherein some of the basic modes in vertical and pitch motion are clearly excited. The skis or track may loose contact with the terrain . The integration of the equations of motion is smooth and permits sim ulations at a much higher velocity than was previously possible under the restrictive assumption of a rigid terrain and permanent contact.