LYRA is an awakening speed monster eager to attack the race track. She has a strong body fit to tackle any turn, a steady circulatory system effectively transmitting signals and distributing energy, and a refined nervous system turning impulses from the surroundings into agile movement. With these features, she will blaze through the race track as fast as a shooting star. In other words, the mechanical and electrical systems, tied together by software, forms our eleventh racecar in a line of top-performing predecessors.
After eight months of innovation, ambition and dedication, we unveiled this year’s racecar at Samfundet in Trondheim. The result of teamwork extending the experience, knowledge and skill of previous teams stood proudly before the eyes of this year’s team, our sponsors, alumni, friends and family. The screen pixels had become tangible, and the beauty of innovation and teamwork tugged on our heartstrings. Throughout the evening, we got to know each other and the car. In this blog post, you will get to know LYRA’s mechanical, electrical and software features.
One of the main factors contributing directly to the racecar’s performance is its weight. Since the formation of our team in 2010, we have spent countless hours shaving off as many grams as possible. This year’s car weighs only 164 kg, and after millions of processing hours, we have designed and produced an aerodynamic package providing 867 N of downforce. With a center of mass as low as 267 mm above ground, we have found the perfect balance between having a lightweight car, optimal track grip, ease of control and predictable behavior.
The carbon fiber monocoque brings strength and structure, and by using new geometries in our core material, we are able to save grams. Progressing into our second year of making an EV-DV (manual and autonomous driving modes) merged car, we have found new ways of making the pedals, seat and steering system accessible in both driving modes. For the first time, we have designed our own steering rack, increasing the precision in driverless mode.
The use of multibody simulations has allowed us to accurately identify the ideal balance between mass and stiffness, damper system stiffness and damping and much more. This thorough groundwork has resulted in a suspension system weighing mere 47 kg. A brand new strain gauge system aids us in validating the forces produced by the tyres and aerodynamic elements, where the data will be valuable for years to come.
This year’s aerodynamic package is designed to maximize the performance both in turns and straights. From more than 1000 simulations, a set of new aerodynamic elements have emerged, which will supply the car with almost the same amount of downforce in a straight as in a turn. At a top speed of 115 km/h, the downforce will equal twice the weight of the car – 320 kg.
Trying out new concepts is only half the job. To validate the new concepts, we have implemented a new sensor system that will utilize a pitot probe that will measure the wind velocity and a set of strain gauges that will reveal the downforce at all times.
Such sensors are principally simple, but don’t be fooled. Advanced electronics are hidden underneath. Both the pitot probe and the strain gauges belong to a new low voltage system. This new system consists of 4 controllers communicating with 20 workers. The controllers are placed in each corner of the car, whilst the workers are placed in the braces of the suspension.
The heart powering our beast of a car is the 600 V, 6.3 kWh accumulator (battery pack), consisting of 288 battery cells and weighing 45 kg. More than 300 sensors monitor the voltage and temperature of each battery cell. This monitoring system ensures safety as well as the ability to precisely decide when to push the car to the limit during a race. Additionally, having our accumulator management system based on microcontrollers eases the debugging and development process.
The accumulator administers the low and high voltage, and the power distribution is controlled by a PCB (printed circuit board), called PCU (Power Control Unit). Enhanced with a microcontroller, this board lets us measure the current running through our low voltage system, such that we may become more energy efficient and design systems based on the actual power needed in the future.
The PCU is located inside a large casing which also houses other larger components of the low voltage system. The new setup has resulted in a simpler wire harness inside the car, as well as made it easier to test several systems outside the car.
Our in-house developed inverter is one of the most innovative and complex systems in the car. Last year, we used our 2019-version inverter, but the development of a descendant has been in the works since the COVID-19 pandemic hit. This year, we are implementing the next generation of our inverter, called I21. It’s smaller and lighter and can be assembled and disassembled quicker than its predecessor, saving us valuable time during the testing and competition season.
In order to keep the car going, a stable cooling system is a must. This year, we utilize phase changing materials. At high temperatures, the material turns to liquid. The greatest advantage of this is the ability to provide a tighter accumulator casing, preventing rubble and dust from entering. This cooling method also acts as a firewall surrounding each individual cell, equipping the car with another layer of protection. Additionally, we use parallel water-cooling-circuits on either side of the car to prevent our motors, the inverter and the processing unit for the autonomous systems from overheating.
Contributing to the overall focus on development and validation of designs, the Software department has developed a new data storage solution: SKN. Our previous solution was beautifully engineered, but over time, it had turned into a tangled and unadaptable system. The new system will change the way we work with the car’s data across departments. Now, all data is collected in a single place, and the various exporting methods accommodate all our needs.
One of the data type inputs of SKN is data from our in-house developed lap time simulator. This simulator allows us to see the effect of our designs before even producing the car. In order to increase the accessibility of the simulator within the team, we have developed an improved user interface.
In addition to validating our designs with the help of a simulator, we validate the simulator itself. By comparing data collected from a simulation with actual data from drives, we have been able to make our simulator correlate 90% with reality. The secret lies in the level of detail in the simulator, but those exact details will remain a team secret for now.
To make LYRA drive autonomously, we switch out a human driver’s eyes with a LiDAR, the legs become actuators, and the brain turns into a processing unit capable of evaluating over 300 trajectory decisions per second. In manual driving, we take advantage of torque vectoring. This algorithm calculates and applies the optimal force distribution for each tyre, resulting in the best possible grip. This year, the application of torque vectoring will be able to advance our autonomous driving, opening the door to a sea of possibilities.
The test and competition season is right around the corner, and we are excited to take LYRA to the finish line. Join our journey by keeping an eye out for updates on our blog and social media accounts.
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