LiU Formula Student Team – Empowering Innovation

From an Electronics Point of View

LiU Formula Student is a student organisation at Linköping University, Sweden. Every year we design and build a formula style race car, which we race with against other universities all over Europe. We started the journey of building an electric car in 2020/21.

Our 2022/23 season had one major goal  – build an electric car and bring it to an international competition. We went to two competitions, Netherlands and England, but unfortunately we could not participate in the dynamic events due to electrical problems. However we are still proud of our season and our progress despite some major setbacks affecting the timeline in the project.

During 2022/23 we focused on simplifying some of our electrical concepts. We scheduled two larger orders of PCBs where the first one was intended to do extensive testing and verify functionality and the second one was planned to be the final version of the PCB. Partnering up with a PCB manufacturer like Eurocircuits provided us with fast production and high quality PCBs.

The car would feature many different circuit boards. Below follows an explanation of some of them.

Brake System Plausibility Device – BSPD

The Brake System Plausibility Device is a safety system in the car. Its primary job is to disable the tractive system in case of excessive braking and acceleration is detected at the same time (in case something malfunctions with the electronic throttle).

One new feature that was added for this year’s BSPD was the variable resistors which made it easier to tune the current and break pressure sensor signal to make the device rule compliant.

Tractive System Active Light – TSAL

The Tractive System Active Light is a system that indicates the electronic state of the car. It is placed on the main hoop to make it as visible as possible for team members or marshalls in the proximity of the car. If high voltage is present outside the accumulator the light becomes red, otherwise it is green. This system is required to be only hardwired electronics by the rules.

The System consists of multiple PBCs. This is the HV unit that measures if high voltage is present or not. This unit is placed both in the accumulator to measure the vehicle side voltage domain and on the car in a tractive system enclosure to measure the inverter side voltage domain. 

The other PCB is the LV Unit that handles additional output and input signals to control the logic of the LEDs that is placed on the main hoop.

Tractive System Control Unit – TSCU

The Tractive System Control Unit controls various relays around the car and inside the accumulator for the tractive system (High voltage)

driver input and various sensors to put the car into suitable states (on / off / starting up / cooling down / etc.).

During this year’s project this system was redesigned and was changed from using hardwired logics to instead use an STM Nucleo microcontroller to handle the logic. This was done to make debugging and troubleshooting easier and by using software instead it was possible to make necessary changes or add new features faster.