Abstract
My thesis brings together two projects: the design of a planetary gearbox for the University of Virginia’s FSAE electric racecar and an STS analysis of safety-critical design in the high-voltage systems that power EVs. Although these projects focus on different areas, they are both aimed at enabling the safe future development of an FSAE electric racecar, as well as EVs in general. The technical research focuses on a mandatory choke point in the transition to in-wheel electric motors. The STS analysis not only improves overall safety but also allows for more ambitious technical design through a more deliberate understanding of the procedures and compromises necessary for a safe vehicle.
The technical portion of my thesis produced a compact, one-stage compound planetary gearbox directly integrated into the upright of an FSAE electric racecar. This design replaces the traditional single-motor, chain-driven FSAE system in order to enable the use of four in-wheel motors. Individually powered wheels are already a staple of high-performance EVs. This motor configuration allows for maximum tire performance to be extracted, since power can be biased based on the available grip at each tire. Torque vectoring—a process in which the tires on the outside of a turn are powered more than those on the inside—allows a car to effectively surpass traditional vehicle dynamics and forcibly rotate through the turn. The final gearbox design achieves a gear ratio of approximately 11:1, which aligns with the target vehicle top speed of approximately 80 mph. The entire system has been analytically validated and designed around a targeted minimum 750-mile lifespan. A complete assembly was fabricated entirely using equipment within the University of Virginia to verify that it met spatial constraints, exceeded critical load thresholds, and was reasonably manufacturable for future generations of the FSAE EV.
In my STS research, I examined how to design high-voltage, high-current EV systems to mitigate risks such as electrical shock, thermal runaway, and arcing. Engineers, drivers, and anyone else in proximity to an EV are central human actors who must be considered. The battery pack, safety systems, and any other potentially compromised components are critical non-human actors. My research demonstrates how layered, redundant, and deliberately designed systems can improve overall safety. There is an intimidatingly vast range of possible failure modes in a high-voltage system that must safely interact with people in the aggressive environment of an EV. My research also examines scenarios in which consolidation or simplification of risk factors and safety measures is beneficial or harmful. Despite the common intuition that more is better in safety, excessive or overly complex measures often lead to complacency or desensitization.
Working on these projects reinforced that all engineering design is about balance, whether technical performance and manufacturability or system safety and serviceability. The gearbox project allowed me to fully apply the skills I had been cultivating through the mechanical engineering curriculum. The STS research provided a deeper understanding of safety that will enable both the FSAE team and me to develop vehicles more aggressively while maintaining safety. The ethical significance of this work lies in prioritizing safety alongside innovation, ensuring that advancements in EV technology support both high performance and the well-being of the people who design, build, and interact with these systems.
