Stability of a multi tracked robot traveling over steep slopes

Tracked vehicles can offer the best solution for operation over complex terrains, including difficult surfaces. Tracked configuration is often required to guarantee the best mobility for unrestricted, all-weather tactical operations. A safe and reliable motion requires the vehicle to maintain stable contact with the terrain while avoiding slippage. This becomes critical when traveling over complex surfaces, especially steep and slippery slopes. This paper deals with the problem of how to maintain a stable motion of a multi tracked vehicle traveling over steep slopes. Changes in the vehicle's internal configuration adjust the center of gravity to guarantee a stable motion. The paper analyzes the acceptable positions for the center of gravity given the slope's inclination, and the friction between the vehicle and the surface. Geometric solution for a two dimensional model is first presented, followed by the linear programming solution of a 3D model. Experimental results, as well as a field test conducted on our multi-tracked autonomous vehicle verify the theoretical analysis and provide constraints for stable motion given the vehicle and terrain geometry and friction between the vehicle's tracks and the surface.