Founded in 1997, the University of Toronto Blue Sky Solar Racing team is a student-led design team that has designed, built and raced solar powered vehicles for over 25 years. Designed to maximize efficiency, solar racing is a precise balance between many intertwined factors like material weight, solar cell chemistry and telemetry systems. As a result, the process is long and challenging, with each vehicle undergoing two years of rigorous research, drafting, simulations and validations before it is finally ready to race in competitions across the world. The end result is well worth it: a finely-tuned, high-performance machine, weighing less than a little over 200 kilograms and capable of reaching top speeds of over 100 kph- all running entirely on solar energy. 

My journey at Blue Sky Solar Racing started as a Fabrication Engineer. I transitioned into an Electrical role and am currently the Chief Electrical Engineer for the Gen12 Design Cycle where I oversee the whole electrical system of the vehicle.

Bridgestone World Solar Challenge 2023

As part of the race crew for the Bridgestone World Solar Challenge 2023, I took on dual roles as an Electrical Team Member and Solar Car Driver. My primary responsibility was to support the operation of the car’s electrical systems, working closely with the team to troubleshoot and resolve any issues that emerged. I contributed to diagnosing and fixing electrical challenges on-site, ensuring our car remained fully operational throughout the competition. In addition to my technical contributions, I also served as one of the solar car drivers. I drove a six-hour segment of the race, from the Dunmarra Control Point to the Tennant Creek Control Point. Despite thorough preparation and consistent team efforts, we encountered the challenge of limited battery range on the last day of the race, ultimately running out of charge 30 kilometers from the finish line. This placed our team 15th in the Challenger Class. 

Centralized Control Motherboard 

May 2024 - Present

Technical Overview

The BFM is the main Logical Control Unit of the whole Car. It is a centralized System to control all the Low and High Voltage Systems. It eliminates the need for inter board commu nication by combining all the required hardware to control the car into one big motherboard. The BFM also consists of a HV section which measures the power (current and voltage) of the Array, Battery and Motor. 

As compared to the previous iteration of the low voltage system of the car, the BFM achieves a reduction of 6 SMT32 Microcontrollers, 12 custom PCBs and 2kg in wire mass resulting in faster debugging and improved performance.

The BFM consists of 7 pluggable modules listed below: 

1. Toradex Module 

This module is a custom carrier board for the NXP® i.MX 8 CoM. The i.MX 8 runs embedded linux OS and controls all the logical functions of the car. It consolidates all the signals from the car and runs a multithreaded program to monitor and react to any changes in the car. 

2. Power Module 

The Power Module supplies 12V and 3.3V to BFM and Steering Wheel. 

3. Battery Module 

The Battery Module is the interface between the Battery Box and the i.MX 8 CoM.

4. Driver Interface Module 

The Driver Interface Module is the interface between the Steering Wheel and i.MX 8 CoM.

5. Miscellaneous Module 

The Miscellaneous module houses the Telemetry Radio and Light Drivers for the car. 

6. Sensor Module 

The Sensor Module is designed to gather sensor data for the car. The goal is to use this data to characterize the car and improve performance. 

7. Motor Module

The Motor Module converts driver input signals received from the i.MX 8 CoM into analog signals the Nomura ECU can use. 

Management

Designing the BFM was a big undertaking for the electrical team and one of my first tasks as the Gen12 Electrical Lead. To streamline the process, I designed the top level layout of the BFMmotherboard, assigning a fixed footprint for each module depending on the electronics it had to carry. These footprints were then designed as components on Altium Designer. 

From here, I was able to black box the modules, knowing that their size is fixed within the overall framework of the BFM. This allowed me to successfully parallelize the workflow and assign each module as a project to individual members of the electrical team. Through this, I was able to achieve my goals for team development: 

1. Higher member retention because they could take ownership for a project

2. Efficient and faster design of the motherboard through workflow parallelization. 

Integration

Outside the electrical design, I also coordinated the design and integration of the BFM with the rest of the vehicle. This involved two important tasks: 

1. Signal and Power cable routing within the vehicle

2. Mounting the BFM with the chassis of the car. 

The first task was achieved through carefully studying the aero body of the vehicle based on which, the optimal cable length and harness points were decided. 

For the second task, a custom 3D printed enclosure with I/O mounts for the connectors was designed to be mounted at the back of the car. A key point of consideration was to avoid electromagnetic induction within the PCB as it was mounted next to the motor and motor controller. To prevent this, the 3D printed box was lined with copper tape in between the plastic layers to form a Faraday cage and prevent any EM radiation. EM protection is also incorporated in the PCB. The custom PCBs follow a four layer stackup with the outer two layers forming the ground plane to act as an EM shield.

Maximum Power Point Tracker (MPPT)

March 2024 - Present

The Maximum Power Point Trackers was my personal project at Blue Sky Solar Racing. The idea was conceived after the need to improve our solar array performance. 

The design is based on a DC DC Boost converter with GaNFET switches to achieve a theoretical efficiency of 99%. Since the solar array is divided into three strings, the design combines 3 DC DC boost converters on the same board with a combined output capacitor to minimize board size, micro controller count and parasitic losses in inter board wires.

Simulations

Simulation were run on PLECs to match the design requirements based on the battery pack and solar array architecture. The boost convertor is designed for the following specifications:

1. Input Voltage Range: 45V - 50V

2. Maximum Input Current: 8A

3. Output Voltage Range: 85V - 145V

The primary design goal is to reach a target efficiency of >99%.  A screenshot of the simulation setup is shown below along with select simulated efficiency curves.

Hardware Design 

 A major concern with board design was to prevent EM noise coupling from the high voltage switching traces of the converter to the analog current and voltage measurement signals. To achieve this, the current sense signals were made differential. Furthermore, the stackup was carefully designed to ensure reduction in EM coupling. A four layer layer stackup was designed with Layer 1 and 2 carrying the switching traces, layer 3 was set as a continuous ground plane and layer 4 was used to route the analog signals. The ground plane in the third layer was used as an EM shield for the critical analog signals in the bottom layer. 

A STM32 microcontroller was used to control the three converters. More details of the algorithms used is discussed in the next section. 

Software Design 

A boost converter in MPPT applications does not work in the same way as a conventional Boost Converter. In such applications, the output voltage is fixed by the battery pack and the input voltage and current is dependent on the biasing of the solar strings. The goal of the boost converter is to bias the solar strings at their Maximum Power Point (MPP). They achieve this biasing by changing the duty cycle of the converter. Since, the output voltage is fixed by the battery, the input voltage will change based on the converters duty cycle relation. A change in the output voltage of the solar cell will change its bias point along its IV curve. The new input power at the bias point is then calculated from current and voltage measurements at the input. This is compared to the power calculated at the old bias point and based on that, the duty cycle is increased or decreased to find the MPP. The output current charging the battery pack is dependent on the input current at MPP bias point. 

For the MPP algorithm, an Incremental Conductance Algorithm is implemented to find the bias point by measuring the incremental conductance or slope of the PV curve. It works on the principle that at the MPP, the slope of the PV curve will be zero. On top of the MPP algorithm, a PID controller is used to set the duty cycle. 

GEN11 Steering Wheel

May 2023 - October 2023

The steering wheel was designed using carbon fiber wet layups. I designed a custom 3D printed mold for the steering wheel. The mold was then sanded down to remove any surface imperfections before performing the layups. A layer of primer and multiple layers of mold release was applied to ensure a good separation between the mold and finished part. After the carbon fiber layups were completed, the part was allowed to cure for 24 hrs under vacuum. 

Upon inspection, the finished part, was not up to our expected standard and had multiple manufacturing defects. Furthermore, the complex process of rebuilding the mold made it unfeasible on a tight timeline before the race. 

Hence, a simpler method of using carbon fiber sandwich panels with 3D printed parts was adopted. A half inch rohacell core with 2 carbon fiber layups was applied on both sides. The panel was allowed to cure under vacuum for 24 hours before being water jetted to cut out the shape of the steering wheel. 

The finished product used the water jetted carbon fiber piece as the base with 3D prints around it to ensure increase ergonomics. The steering wheel was used throughout the race at the Bridgestone World Solar Challenge 2023.