Gearing up for the Win
Having previously competed in the Formula Hybrid competition, the team has had some experience building race cars. However, the E-Model 1 was the first vehicle in the team’s history to be completely electric. Ambitious engineering goals resulted in a necessary two year design cycle as the team learned all about electric powertrains and the new competition.
Designing and building a fully electric racecar is a highly intensive process which can be broken down into the parts below
This year, the team developed our first aerodynamics package. The package consists of a front and rear wing with aerodynamic coefficients designed to minimize lap times in a simulator. STAR-CCM+ is the primary CFD tool and was used to design the wings and perform full vehicle simulations. We make all of our own moulds and layup our carbon fiber by hand using infusion. Simulation showed the enormous benefit of an undertray, however due to budget constraints it was not possible to build. This year, we hope to re-use our current wings while designing an undertray and new bodywork.
Our powertrain architecture development was a mix of criteria between future 4WD potential and budget constraints. With the huge support of Allied Motion, we designed and manufactured our own custom in-hub motors. Allied Motion worked with us on developing a custom rotor and stator tuned for our specifications. We also developed a planetary reduction gearbox packaged inside the width of the rotor inside the motor housing resulting in a compact drive solution. We also developed our own ATF cooling loop designed to both cool and lubricate the motor.
Our high voltage battery (a.k.a. the accumulator module) is constructed out of A123, 20Ah LiFePO4 cells. These cells were selected due to both the incredible sponsorship from A123 as well as for their chemistry which is significantly safer than most other high energy density cells. A custom designed battery management system was developed to read the individual cell temperatures and voltages to ensure the safe operation of the battery while in operation. To handle the heat loss due to the high current, a custom water cooling loop was developed to keep the cell temperature below their safe operating temperature.
The design of the chassis followed a similar design to our last hybrid car. Our frame is a space tube frame constructed out of welded SAE 4130 tubing. The design of the suspension was a complex tradeoff of parameters which we modeled and simulated to achieve the best setup given our constraints. Our entire steering system is developed in house and in coordination with the suspension to ensure optimal handling characteristics.
Our embedded system is entirely self-developed in-house with custom PCBs for all aspects of the car. We have iterated on our distributed architecture for many years by continuously increasing functionality, reliability and most importantly, safety. Our distributed architecture minimizes harness complexity and mass, as well as improving the quality and reliability of data transmission around the car. All aspects of our system are constantly monitored and logged to ensure safe operation and easier debugging.
With the transition to an electric car with independently driven rear tires, the potential for control algorithms is introduced. For our first electric car, we developed stabilization algorithms to improve handling characteristics around the track as well as basic launch control systems. We plan on using E-Model 1 as a testing platform to characterize the kinematics of our car better and develop our torque vectoring and traction control algorithms as we iterate on our first year's car.