All ETDs from UAB

Advisory Committee Chair

Vladimir Vantsevich

Advisory Committee Members

David Littlefield

Lee Moradi

Document Type

Thesis

Date of Award

2020

Degree Name by School

Master of Science in Mechanical Engineering (MSME) School of Engineering

Abstract

Longitudinal slippage analysis is a focus in terrain mobility for further development of mobility enhancement, power optimization, and safety design. This paper discusses the results of the collection and analysis of a database for tire traction characteristics and tire data conscripted of various literature experimental tests from books, journals, and technical papers. The database is utilized to support analysis and reviews of several tires and their behaviours under locomotion on different soils and deformable terrains to demonstrate the effects of the characteristics for mobility. Many experimental tests exist in literature across the technical world, but a centralized collection would benefit researchers in having all necessary parameters for their respective analysis procedures. This study is based on Janosi and Hanamoto’s soil shear-stress strain relationship. The tire traction characteristics are utilized to split the force-slippage curve into two components that define the characteristics in terms of terrain contribution to slippage and tire contribution to slippage. Tire traction data collected from various loads, inflation pressures, and various surfaces was fit to a new, non-linear traction model. The identification of a novel traction characteristic, characteristic slippage, reveals the individual tire and soil contributions and its shape in relation to the slippage curve with respect to the current friction value. The characteristic slippage value represents the point of excessive non-linearity to be used in future control developments in optimal wheel torque control and was found to represent the functional critical friction value from earlier studies. Because the characteristic slippage is a mathematically defined point of excessive nonlinearity on the slippage curve that gives insight into the growing slippage as the current friction coefficient increases, the analysis revealed that generally accepted slippage values for maximum traction standards can be too low or too high regarding the terrain surface. These derived characteristics will be used for control thresholds for novel controls development in optimizing wheel power and torque distributions due to the mathematical model definition of the nonlinear evaluation of the force-slippage curves demonstrating a slippage threshold for the current terrain the wheel is operating on.

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