All ETDs from UAB

Advisory Committee Chair

Vladimir V Vantsevich

Advisory Committee Members

David L Littlefield

Lee G Moradi

Thomas R Way

Mostafa A Salama

Document Type

Dissertation

Date of Award

2020

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The conventional turning principle of wheeled skid-steered vehicles provides different velocities to the wheels of the left and right sides, yet the two wheels at each side have the same angular velocity. As the analysis shows, this principle is not sufficient for improving vehicle maneuverability in severe terrain conditions. Because the resistance to motion and the tire-terrain grip can randomly and drastically vary in the tire contact patches of all wheels, it makes solely relying on this principle inadequate.In this PhD study, a virtual driveline concept is presented to formulate and study a new turning concept for a small wheeled skid-steered unmanned ground vehicle (UGV). In the UGV, each driving wheel is propelled individually by an electric motor-based drive. Thus, the wheels are not connected by a mechanical driveline system, which would control the power split between the wheels. Instead, a mechanical driveline with positive/controllable engagement of the wheels is mathematically modelled and computer simulated to coordinate the power distribution to the electrically driven wheels by using the characteristics of such virtual mechanical driveline systems. The Kinematic Discrepancy Factor (KDF), which is a characteristic of the mechanical driveline, is computed for each wheel. This KDF serves as a new steer control input of the UGV, i.e. it also acts as a reference signal for controlling the voltage of each e-motor, and, thus, to coordinate the power split among the wheels. In the dissertation course work, the virtual driveline concept was developed in a control algorithm. The algorithm was designed to individually control the power supplied to the wheels by using the KDFs for improving the maneuverability of the UGV. The control designed in this dissertation maximized the UGV’s stability by minimizing the vehicle’s lateral velocity. The design used in this study also maximized the UGV’s turnability by minimizing the deviation of the vehicle from the reference trajectory path. The model predictive control method was utilized for the above-listed maneuver improvements and was further advanced by improving its computational

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