Arctan (solar car)

Arctan (solar car) is a solar vehicle designed and built by the University of Michigan Solar Car Team for competition in the World Solar Challenge and the American Solar Challenge. It represents the team's 13th-generation vehicle, succeeding the Novum car, and was unveiled in 2021. The vehicle's name, derived from the inverse trigonometric function, reflects the team's focus on mathematical precision and engineering optimization in its pursuit of victory in premier solar car racing events.

Overview

The Arctan project was initiated to compete in the Cruiser Class of the World Solar Challenge, a category emphasizing practical solar-powered vehicles with multi-passenger capacity. The team's primary goal was to improve upon the performance and reliability of its predecessor, Novum, which competed in the 2019 Bridgestone World Solar Challenge. Development involved extensive collaboration with corporate sponsors like GM and Mitsubishi Electric, as well as research support from the University of Michigan College of Engineering. The car's design philosophy centered on achieving an optimal balance between aerodynamic efficiency, solar array output, and vehicle practicality under the stringent regulations set by the International Solarcar Federation.

Design and specifications

Arctan features a sleek, monocoque carbon fiber chassis designed for minimal drag coefficient and maximum structural integrity. Its solar array utilizes high-efficiency Gallium arsenide photovoltaic cells supplied by Alta Devices, strategically angled to capture maximum solar irradiance during races across Australia and the American Midwest. Propulsion is provided by a custom Brushless DC motor integrated into a single rear wheel, employing a Direct drive system to minimize mechanical losses. Energy storage consists of a bespoke Lithium-ion battery pack, with power management overseen by a sophisticated Maximum power point tracking system co-developed with Mitsubishi Electric. The cockpit is designed to accommodate two occupants, meeting Cruiser Class requirements, and incorporates advanced telemetry systems for real-time performance monitoring.

Competition history

Arctan made its competitive debut at the 2021 American Solar Challenge, traversing a route from Missouri to New Mexico. The following year, the vehicle was shipped to Australia to compete in the 2023 World Solar Challenge on the Stuart Highway from Darwin to Adelaide. During these events, the car faced challenging conditions including extreme heat, crosswinds, and varying cloud cover, testing the resilience of its systems. The team's performance contributed valuable data on solar car endurance and strategy, competing against other top university teams like Stanford University's Solar Car Project and University of California, Berkeley's CalSol.

Technical innovations

Key innovations in Arctan include a novel active suspension system that adjusts ride height for optimal aerodynamics, and a proprietary thermal management system for the battery pack and power electronics. The vehicle's solar array incorporates a unique curved panel design, increasing surface area and efficiency compared to traditional flat arrays. The team also developed advanced machine learning algorithms for race strategy, predicting energy consumption based on weather data from sources like the Bureau of Meteorology. Furthermore, collaboration with GM led to improvements in composite materials manufacturing and computational fluid dynamics simulations, pushing the boundaries of solar vehicle design.

Team and development

The Arctan project was a multi-year endeavor involving over 100 students from the University of Michigan, primarily from the College of Engineering and the Stephen M. Ross School of Business. Development was led by a student project manager and overseen by faculty advisors from the Department of Mechanical Engineering. Major funding and technical support came from sponsors including GM, Mitsubishi Electric, SolidWorks, and MSC Software. The team operated from its dedicated workshop in Ann Arbor, Michigan, following a rigorous engineering process that included wind tunnel testing at the University of Michigan Walter E. Lay Automotive Laboratory and extensive test drives in Michigan and Nevada.