Terramechanics for Small, Lightweight, Robots

Understanding the traction mechanics of vehicles running on deformable terrain is a crucial aspect of vehicle design, analysis, and simulation. A vehicle's ability to negotiate soft soil has strong implications for both its power efficiency and mobility. A highly publicized example of the importance of mobility over soft terrain is the NASA Spirit rover (part of the Mars Exploration Rover mission), which became embedded in loose regolith on the Mars surface in 2009, causing the untimely end of a several hundred million dollar mission. This is one of many examples illustrating the importance of traction mechanics on vehicle performance.

Terramechanics is the engineering science that studies the interaction between vehicles and deformable terrain. The foundations of this discipline were laid in the 1960's by M.G. Bekker. Bekker's classical work, together with later work by J.Y. Wong, constitutes the landmark studies in the field, and have been exploited with positive results by many researchers over the last 50 years. However, classical terramechanics methods were primarily developed for large, heavy (>2000lb) vehicles, and were not originally intended for application to small, lightweight robots. Recently, the Army, NASA, and other agencies have devoted substantial resources toward the development of small, lightweight ground vehicles. These vehicles are typically less than 36 inches in length and weigh less than 100 lbs, and have both wheeled and tracked configurations. These vehicles have been developed primarily based on empirical testing, and by application of classical Bekker theory.

However, for vehicles in this class, discrepancies have been noted between predictions based on Bekker theory and experimental tests. This is likely due to violation of some of the fundamental assumptions governing the development of Bekker theory. The proposed work aims to develop improved terramechanics models for small, lightweight ground vehicles. This work will have important implications for small robot design, simulation, and autonomous navigation, and will lead to the development of systems that are more mobile, robust, and cost effective.