Fast Charge Formula SAE Team at Sapienza University of Rome: PCBs that make our car race

Introduction

Sapienza Fast Charge is the Formula Student Electric team of Sapienza University of Rome. The team is made of more than 100 students and, for the 2023 season, is focusing its design activity on the optimization of powertrain, and a monocoque chassis to obtain higher continuous performance in racing. A careful design of the storage system has been performed, combining a sizing strategy tailored on endurance real data with an optimized cooling system. The main specs for this competition season are made up of: new monocoque chassis, single Emrax 228MV electric motor with Emsiso Emdrive H300 inverter, Murata/Sony VTC6 lithium-ion cells with FR4-ABS case, air cooling system with electronic management, ergal wheel groups, limited slip differential, data logging system with thermistors on all cells, a complete set of sensors for car vehicle dynamics and last but not least carbon-kevlar bodywork for an overall car weight of 236 kg, 80 kW power and 950 Nm at wheels.

Here a photo of the car on one of the our software that we use:

Here also you can find links to our social network pages https://linktr.ee/sapienzafastcharge :)

Sapienza Fast Charge

Sapienza Fast Charge is the electric Formula Student team of Sapienza University of Rome and is a true motorsport company demo, where everything is done by students: from marketing, design of the car, communication to driving the vehicle in the race. In Sapienza Fast Charge an electric single-seater race car is designed and built, and the team competes in international competitions. Throughout the year, the team's activities span a wide range of fields: events to showcase the vehicle at major trade shows and conferences set the Press and Communications offices in motion, which work throughout the year (while continuing to take exams).

The next season's car is designed in parallel, and the Business and Project Management departments put their energies into contacting sponsors, planning the work, and building a business plan for virtual marketing of the vehicle (including participation in static events). The team was established in 2013 and, for the 2024 season, consists of 141 students from various Faculties and Graduate Courses at Sapienza University of Rome.

The goal for 2024 is to launch, after 2 years of development, our fully self-driving electric car. The single-seater car is already available in almost all major components, and a large group of computer science students are engaged in the implementation of track recognition and control of the car's dynamics. Such a traveling laboratory is the ideal platform for comprehensive all-around training of future engineers in autonomous driving and artificial intelligence techniques for the realization of full self-driving vehicles.

Here is a YouTube link (with English subs) that gives you a glimpse of our reality, led by our Faculty Advisor and Professor Leone Martellucci:

Design Philosophy 

The concept behind the Fast Charge project is to design and realize a reliable, light, powerful, easy-to-drive car with a low active cost and maintenance. The team’s name is inspired by the fast recharge technologies of the future: one of the ways to make electric cars a solid answer to mobility’s questions. Our main goals are to contain weight, optimize handling, prevent power loss due to overheating of the storage system, have good performance, control the maximum delivered torque to avoid wheel slip in acceleration.

The World Championship: Formula SAE and Formula Student

Formula SAE is an international university engineering design competition initially proposed by the Society of Automotive Engineers (SAE) that involves the design and manufacturing of a race car, evaluated during a series of tests on its design qualities and engineering efficiency. Established in 1981, with the aim of giving university students the opportunity to compete in a competition that allows them to put into practice what they have learned during their studies, the competition is spread all over the world, with several annual events, organized directly by SAE or by the various national associations of automotive engineers and technicians. There are currently 3 categories in each competition: Class 1C (for gasoline vehicles), Class 1E (for electric vehicles) and Class 1D (for Driverless vehicles). They are joined by a fourth one, called Class 3, in which teams that only submit the design of the car participate, thus not participating in the static and dynamic events. Starting in 2017, Formula Student Germany, which has been active as an official German SAE formula event since 2005, has proposed its version of the competition, renaming it “Formula Student”, based on the same concept conceived by SAE, but with some minor changes in the regulations.

Here a video that shows one of the event in which we will partecipate this year:

Some new features

In terms of innovations, for example, last year we switched from a tubular chassis to a carbon fiber monocoque chassis, also there have been changes regarding suspension, aerodynamics, and the battery pack. To achieve these milestones and to run the car at the 2023 season events, the work of the whole team was crucial.

Divisions

The team is organized into four departments, which in turn deal with different projects: Mechanics and Aerodynamics; Battery, Electronics and Powertrain; Business and Management; Driverless.

The Mechanics & Aerodynamics department is in charge of the entire design and assembly of the car: from chassis to powertrain, from suspension to aerodynamics. It also takes care of creating its 3D model and carrying out structural, fluid dynamic simulations in parallel; finally, it actively participates in the development of the ECU software for applications that affect it (mainly vehicle dynamics), kinematics, or dynamics.

First and foremost, the Battery, Electronics, and Powertrain department (BEP) takes care of the battery pack, the heart of the car, from design to construction to testing. The department is in charge of the entire low- and high-voltage electrical compartment, including the sensors and auxiliary components, but also the motor and inverter. It takes care of the electronics on board and the charging phase. Finally, it develops the software that controls the entire vehicle, from torque control to digital communication.

The Driverless department focuses on software development for autonomous driving of the (second) car. Artificial intelligence (ML, RL), computer vision, virtualization of physical models, digital twins, and algorithmic optimization are just some of the areas in which it is possible to specialize and apply.

The Business & Management department is responsible for establishing sponsorship relationships with companies, organizing events, taking care of external relations, logistics, social media, and team image management. For Formula SAE races, the department is responsible for the creation of a Business Plan and, assisted by the technical departments, the writing of reports on the Cost & Manufacturing material of the car. The department also provides managerial assistance and deadline supervision to other departments’ projects.

As you can already see at first glance, the units tend to be rather technical, but the most multifaceted is Business and Management — which deals with projects that are very important to the success of the team and is even more open to students coming from all fields of study. In fact, the department (B&M) in addition to the aforementioned, follows so many aspects being evaluated by the Formula SAE competition judges in the so-called Static Events, such as the Business Plan Presentation, the Cost Event and the Design Event.

A Summary of the Static Events

Business Plan Presentation: its objective is to assess the team’s ability to develop and present a comprehensive business model. This business model must relate to the team’s specific prototype vehicle or a specific component of it. In doing so, the business must offer the vehicle or component as a product, or sell a service based on it, providing a rewarding business opportunity that creates a monetary profit. The judges act as if they were potential investors or partners for the presented business model.

Cost and Manufacturing Event: The objective of the cost and manufacturing event is to evaluate the team’s understanding of the manufacturing processes and costs associated with the construction of a prototype vehicle. This includes trade-off decisions between content and cost, make or buy decisions, and understanding the differences between prototype and mass production.

Engineering Design Event: its concept is to evaluate the student’s engineering process and effort that went into the design of a vehicle, meeting the intent of the competition.

Students on the team accompany their studies with hands-on experiences, coming into contact in a variety of ways with sponsors and large entities such as Tesla, Siemens, Dallara, and Lamborghini.

To name a few of the opportunities that have been created in Fast Charge, we think of a start-up company that now produces battery packs for very well-known automotive customers and was born from students on the team or many examples of former team members now working in automotive companies in a wide variety of positions. Another member of ours who is studying design, for example, is using the design of the single-seater steering wheel as the topic of his dissertation.

The team requires a lot of commitment, presence, and perseverance, beyond university study. The team is open to anyone willing to go the extra mile.

To join the team, you must pass a written test based on applications, depending on the department you want to be a part of, and most importantly the Formula SAE regulations. Passing the test, you enter an oral interview with the Heads of Department and Team Leader.

For further technical details about our car, you can see our 2023 Design Report which contains a brief descript_ion of the overall vehicle including the Autonomous Systems with a review and derivation of the team’s design objectives.

Here are the PCBs in our project

BSPD (×3)

Brake System Plausibility Device: is also a safety board because it handles the signals from the brake and accelerator by acting on the shutdown circuit, which is the machine's safety circuit and according to the specifications given in the regulations.

Fuse box

Board that is responsible for directing power to the various electrical and electronic compartments of the machine, and possibly protecting them in case of malfunctions or short circuits. At the same time, we have added functions necessary to control organs required by the regulations, for example, the buzzer (an instrument that acoustically signals that the machine is ready to move) and the inverter.

Insulator (×3)

This board's role is to latch the errors that come from IMD and BMS, which are the main components that ensure the safety of the driver and the components of the car. These errors have to be latched until they are physically restored by a person.

Power Supply Board Cockpit (×3) and Power Supply Board Discharge (×3)

We have here two very similar boards: one smaller, the other larger. Both boards have the function of ensuring the most stable and correct power supply possible with the special functions soft start (allows to give power gradually each time ensuring less spikes), maximum current limitation, reverse polarity protection.

Dash (×3)

Made to control the machine dashboard that gives us information regarding the machine's movement speed and all other parameters, such as the temperature of the battery pack or errors such as a temperature higher than the machine's normal operating temperatures.

Safe board (×6)

It is a board specially made to turn signals from other boards into compliance with the regulation so that the safety of the machine can be more strictly controlled.

TSAL (×3)

Board that deals with the management of the machine's lights according to the operation dictated by the regulations. It visually ensures that the machine can be operated or not (for safety reasons).

LED control (×3)

LEDs give a quick check of machine functionality. Board that handles the indicator lights on the cockpit of the machine under control of the insulator and BSPD, TSAL, thus going to indicate malfunctions of the IMD (Insulation Monitoring Device), BMS (Battery Monitoring System) or brake or throttle faults. 

This following boards are used in our driverless car.

ESP32 Write + assi (×2)

This ESP32-based board manages the data coming from the Autonomous System Central Unit, forwards them on the CANBUS, outputs the active state of the vehicle such as “DRIVING” or “EMERGENCY” and controls various actuators and motors, such as the stepper motor for the steering. 

ESP32 Read (×2)

This ESP32-based board manages the data coming from the CANBUS and LIDAR, forwards them to the Autonomous System Control UNIT, thus creating two separate and reliable single-way communication between vehicle’s different sectors and Autonomous System Control Unit. 

ESP32 Watchdog (×2)

This ESP32-based board ensures a constant control on the main Vehicle Control Unit and alerts the ASCU whether the communication between those two units is still active.