Date of Award

6-9-2017

Document Type

Thesis

Publisher

Santa Clara : Santa Clara University, 2017.

Department

Mechanical Engineering

First Advisor

Michael Taylor

Abstract

The versatility of current rovers and exploratory vehicles is limited by a single drive system. The Variable Drive Vehicle (VDV) employs a actuated systemcapable of switching between wheeled and tracked drive modes. This allows the vehicle to travel quickly and efficiently over smooth terrain and to traverse more arduous terrain by switching between these two systems. The small scale prototype built over the course of this project is equipped with two modular wheel driven track units to demonstrate the viability of the system. Electric linear actuators and servo motors allow for simple control and a smooth transition between each drive system. These devices allow the modular tracks to be rotated out from under the wheels, and stowed on the vehicle when not in use. Finite element analysis ensured that the VDV’s switchingmechanism maintains safe loading at its most critical points during a drive system transition. The VDV was tested on smooth concrete to determine its maximum wheel speed, track speed, and how fast the drive system could be switched. Experiments yielded a top speed of 11.5 mph in the wheel mode, 0.8mph in the track mode, and a switching time of 6.4 seconds. The vehicle’smaximumobstacle clearance, 1 inch in track mode and 2 inches in wheel mode, and slope, 5 degrees in track mode and 22 degrees in wheel mode, fell short of expected values. These shortcomings resulted from a poor frictional power transfer when attempting to power the tracks using the wheels. However, this prototype provides a proof of concept for a variable drive system successfully incorporating two drive systems, and future improvements may yield a promising platformfor future robotics research.

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