| This thesis presents advances in the field of terramechanics, the study of vehicle mobility performance, for small, rigid-wheeled vehicles operating on deformable terrain. Specifically, the thesis proposes new models for vehicle performance modeling through the development of novel pressure-sinkage equations. The semi-empirical equations of terramechanics, first developed by Bekker in the 1950s, couple vehicle mobility systems and terrain geotechnical properties to yield an understanding of the manner in which traction is developed off-road. This is important because on deformable terrain mobility is often limited not by the vehicle's torque or power, but by the strength of the terrain and its ability to support locomotion.;Classical terramechanics models have proven to be instrumental in the design, modeling, and operation of large, man-driven vehicles for applications such as agricultural, military, and commercial transport. However, these models are not appropriate for vehicles with wheels less than approximately 50 cm in diameter [Meirion-Griffith11], [Scott08], [Richter02]. This is a critical problem because of the increasing proliferation of small, robotic vehicles. In particular, space agencies such as the National Aeronautics and Space Administration (NASA), the Japanese Aerospace Exploration Agency (JAXA), and the European Space Agency (ESA) have shown great interest in the application of terramechanics to planetary exploration rover mobility.;At the inception of the author's research, several independent sources had noted the limited accuracy of classical terramechanics models for small-wheeled vehicles. However, an understanding of the cause of these inaccuracies was absent. This thesis provides an understanding of these inaccuracies, their cause, and a solution. Using laboratory experiments, field test data, theoretical development, and vehicle simulation, this thesis proposes a modified terramechanics framework for predicting small, rigid-wheel traction. |
