Predicting tractive forces for ground vehicles on rocks

Some characters in the PDF may not display correctly without the Math1Mono font. The Word document is included because it displays those math symbols, though it isn't as well formatted.This thesis reviews methods for predicting the coefficient of friction between the rubber running gear of ground vehicles and typical rock surfaces. The methodology finally applied relies upon fractal descriptions of rock surfaces and fundamental rubber mechanics advanced in the tire industry. A critical assessment is made of this technique, and modifications are proposed for application of a computational method to aid prediction of small robotic vehicle mobility over different types of rock surfaces with different amounts of wear. Difficulties associated with finding critical input parameter data for both rubber and rock are discussed. It is found that this computational approach can predict relative changes and trends in the coefficient of friction for different surfaces; however, absolute magnitudes of friction coefficients can not be accurately determined. In the end, a framework is proposed for combining the relative predictive capability with minimal laboratory testing to allow determination of coefficient of friction as a function of slip velocity for a given rubber/rock-surface specificationMechanical Engineerin