Electronics – Power up!

Hello! I’m Cheryl Docherty, I study Electrical and Mechanical Engineering and I am Co-Head of Electronics for USEV this year alongside Marius Šiaučiulis. I joined USEV last year, working initially within the Motor Controller development team but was also adopted by Body & Aero to work on manufacturing the body towards the end of the year. I have also been one of the team’s drivers for the past two years!  

The run-up to last year’s competition was a stressful time for Electronics. Up until mid-June last year, all Motor Controller work was focused on a hub-mounted Brushless DC Motor. Then with 3 weeks till the competition and a motor controller that was not quite finished, we made the drastic switch from Brushless to Brushed, requiring a full redesign of the motor controller and the layout of the electronics compartment within the car. Despite this seemingly impossible task, completing in 3 weeks what some teams could spend a year on, the major push from dedicated members ensured that we got the motor running in time for the competition. We may have only achieved a working motor in the sweaty stress of the paddocks in London at quite possibly the last minute we could have passed technical inspection, but we’ll skip over that for now.  

This year there have been major restructures to the way we run Electronics. As our system is made up of a few distinct parts, the sub-team is split into four Development Teams: Battery, Powertrain, Telemetry and Electronics Distribution Systems (EDS).

The Battery team are responsible for the design and manufacture of a 10S5P 36V Lithium-Ion battery pack. The main push this year was to increase the battery’s modularity, as last year we found that replacing misbehaving cells was quite an ordeal which required more hands than the average person possesses. We have designed discrete 3D printed modules which each hold five 18650 cells, allowing a quick changeover if cells are deemed faulty, and with bus bars designed so that all wiring is kept to the top side of the battery. The modular aspect has also given us flexibility in terms of overall battery shape, allowing us to optimise the limited space available in the back of our car.

There have been major additions within the Powertrain team, with the implementation of a speed sensor, body controller as well as a custom CAN bus protocol. We are also very lucky to be working with Motivity, who are designing and building us a bespoke DC motor, which we are very excited to receive in the coming weeks. We are currently at the stage of beginning to populate PCBs and starting to work more on our firmware, and we are all looking forward to seeing everything finally coming together.  

The new kid on the block this year is our Telemetry team. While the only run data recorded in previous years has been “Events” detected and stored locally by the Battery Management System (overcurrent, undervoltage, etc), this year we have gone telemetry-crazy. Our system is designed to take in and decode the messages sent on the CAN bus line (such as speed, driver inputs, GPS location) as well as additional sensors including multiple temperature probes, accelerometer and gyroscope, storing the data both locally and remotely on a server. We are also developing a Heads Up Display (HUD) for the driver, allowing them to keep track of speed and other important information throughout the run.

Our EDS team is also a new addition to this year’s structure, as previously there has been no team dedicated to this task. The team is responsible for the safety systems within the car, as well as the design of the wiring harness and physically placing all electrical components within the car. They also deal with stepping down our battery voltage (36V) to both 12V and 5V, to be used by different systems within the car.  

With over 30 active and engaged members, Electronics is USEV’s largest subteam, and there is definitely a lot going on. Most teams are currently moving towards the manufacturing stage, where we will be able to see a physical representation of the hours of work which have gone into this project. Personally I can’t wait to see it all come together over the next few months, and I have full confidence that we will make it happen. 🙂