Solar Car Team at University of Virginia

Who We Are

The Solar Car Team at the University of Virginia is a student organization that provides engineering and business students a hands-on learning challenge to design and build a competition-ready solar-powered vehicle! Currently, our goal is to design and build the team’s first car to compete in the 2022 Formula Sun Grand Prix, a closed-track solar car race held annually.

PCBs

The embedded system for the car has been redesigned since our first iteration to use a modular structure instead of a centralized one, offloading much of the design work to 4 specialized PCBs rather than 1 general board. These 4 PCBs will communicate with each other over a Controller Area Network (CAN) bus, and thus only have to focus on one specific component of the car. We decided to use this structure because it simplified our design from a single complex 4-layer PCB to multiple smaller 2-layer PCBs. Advantages to this system include ease of debugging and reducing dependency weaknesses, as one subsystem’s failure doesn’t affect another subsystem.

Each of these boards will run on a 12V input power supply which is stepped down to 5V and 3.3V power lines that will be directly used by all devices on the board. The same cable that supplies power to each board will also be used to hold the CAN bus which all boards use to communicate with each other. All boards use the same microcontroller, the STM32G474CET6, to configure and run logic on. Each board is specialized to handle one subsystem of our car, which may include tasks such as gathering data from temperature, voltage, and current sensors, controlling critical protection systems and the operation of our motors, and sending all of this data throughout our system via CAN and telemetry. All of these boards shown and described below were designed by our team members over the course of the last year.

ECU Board

The ECU board handles all core logic for the car, acting as the central node for all communication between subsystems. Although the CAN network used to communicate between boards is peer-to-peer and communications between two subsystems do not need to go through the ECU board, the ECU board will still listen to all network traffic and control the various subsystems appropriately. The ECU board also handles all driver inputs, such as steering, throttle, headlights, and so on. It uses all these driver inputs, as well as messages received from the CAN bus, to control and monitor all subsystems of the car such that the vehicle continues to operate successfully.

Motor Board

The Motor board interfaces directly with our motor controller. Given commands for speed control from the ECU board, the Motor board will perform any necessary instruction conversions for the motor controller to execute actions. In this sense, the Motor board acts as a translator between the ECU and the motor controller. An important safety feature included in the design of this board is galvanic isolation between the motor controller and the rest of the car’s electrical system.

Solar Board

The Solar board collects crucial data on the performance of our solar cells, which form the power source for the entire car. This data will be sent to the ECU over the CAN network, where it will be used to optimize the car’s energy usage. It is important to accurately determine both the consumption and production rates of energy in order to best optimize our energy usage and prolong our race time, and the Solar board will play a big role in monitoring our energy production capabilities.

Power/Aux Board

The Power/Aux board implements the battery protection system (BPS) for our 5kW battery pack and communicates with our battery management system (Orion BMS) over CAN to monitor the health and safety of our pack. Should any dangerous levels of the battery pack’s current, temperature, or state of charge be reached, the Power/Aux board is responsible for informing the other boards through CAN to shut down the vehicle. It is also responsible for monitoring and controlling all auxiliary driver controls, including the vehicle’s lighting subsystem and the steering wheel horn.

Words to PCBWay

Solar Car at UVA is a non-profit student organization which works towards a future of solar power and clean energy by designing and building solar-powered racing vehicles. We rely on sponsorships and donations for funding, and this project would not be possible without the support of all of our sponsors! We would greatly appreciate any support PCBWay can offer us.