All ETDs from UAB

Advisory Committee Chair

Vladimir V Vantsevich

Advisory Committee Members

Hassan A El-Gamal

Elsayed S Elsayed

Gregory R Hudas

David L Littlefield

Sohair F Rezeka

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Nowadays, energy saving is a prominent concern for scientists and researchers in the automobile industry and academic research institutions. The technological development of more efficient vehicles is a relentless quest. Moreover, maximizing such energy efficiency is essential for vehicle design. Although, existing In-Wheel Motor (IWM) vehicles have successfully improved energy efficiency compared to conventional vehicles, those IWM vehicles are lacking the usage of wheel power distribution strategies to maximize slip energy efficiency. There is a need for researching power distribution among driving wheels that would lead to a breakthrough in off-road IWM Unmanned Ground Vehicle (UGV) energy efficiency. UGV energy slip efficiency strongly depends on the distribution of power among the driving wheels. Non-efficient wheel power distribution can deteriorate UGV slip energy efficiency because some wheels exhibit higher slippages than others. The goal of this dissertation is to minimize IWM UGV slip power losses in order to maximize slip energy efficiency of a UGV moving in straight-line motion in stochastic off-road conditions by optimally distribute power and control the power split among the driving wheels. This can be achieved by developing a comprehensive UGV mathematical modeling in off-road conditions utilizing individual wheel angular velocity control algorithm based on inverse dynamics approach. A control algorithm based on inverse dynamics approach is integrated with dc motor dynamics to control the wheel angular velocity in order to overcome stochastic terrain load torque and satisfy the required program of motion. The developed control algorithm controls each wheel angular velocity by varying the wheel torque based on the control-by-acceleration principle and provides each wheel with the required angular velocity and tire rolling radius. Mechatronics implementation is developed in order to deploy the control algorithm in real-time to control each wheel individually. Unlike the common approach, in which two wheels at each side are treated as one wheel (i.e., having the same rotational speeds); all four wheels are independently driven. Thus the stochastic tire-terrain interaction based on terramechanics approach is developed and integrated with modeling of stochastic behavior of soil parameters in order to accurately model the terrain. Experimental research work, laboratory and field tests of a small UGV with individual in-wheel motor and four pneumatic tires were conducted in the course of the dissertation work. Experimental results are compared with analytical results to validate the proposed UGV mathematical models and control algorithm. It was found that maximum UGV slip energy efficiency of small IWM UGV can be achieved by controlling the electric motors in a way which provides the same tire slippage ratios for all driving wheels. Moreover, the designed, developed and tested inverse dynamics-based control algorithm to control wheel angular velocity has given and excellent response with reducing settling time to 1.21 sec when the controller gains k_w and ρ_w are tuned to be 0.01 and 100 respectively.

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