This paper presents a methodology used to configure an electric drive system for a Formula Student car and the detailed design of a transmission for in-hub motor placement. Various options for the size, number and placement of electric motors were considered and a systematic process was undertaken to determine the optimum configuration and type of motor required. The final configuration selected had four 38 kW in-hub motors connected through a 14.8:1 reduction transmission to 10" wheels. Preliminary design of the transmission indicated that the overall gear ratio would be best achieved with a two-stage reduction, and in this work an offset primary spur stage coupled to a planetary second stage was chosen. Detailed design and validation of the transmission was conducted in Ricardo SABR and GEAR, using a duty cycle derived from an existing internal combustion Formula Student car. The analysis was conducted in line with ISO 6336 and permitted the examination of the stresses in gear teeth and the prediction of gear and bearing life. A detailed design was proposed with due regard to ease of manufacture and assembly, and a full-scale prototype was manufactured to facilitate physical validation of the design. The design analysis showed all gears and bearings had a suitable predicted lifetime with a minimum factor of safety of 1.8 on gear wear.

This work details the development of a lap time simulation (LTS) tool for use by Queen's University Belfast in the Formula Student UK competition. The tool provides an adaptable, user-friendly virtual test environment for the development of the team's first electric vehicle. A vehicle model was created within Simulink, and a series of events simulated to generate the performance envelope of the car in the form of maximum combined lateral/longitudinal accelerations against velocity (ggv diagram). A four-wheeled vehicle including load transfer was modelled, capturing shifts in traction between each tire, which can influence performance in vehicles where the total tractive power is split between individual wheel motors. The acceleration limits in the ggv diagram were used to simulate the acceleration and endurance events at Formula Student. These events were simulated using a MATLAB code considering a point mass, quasi-steady state model with a perfect driver. This method considering all four wheels captures performance characteristics that point mass models normally cannot, without the complexity and time required for more detailed LTS solutions including yaw movements and driver models. It also separates the vehicle model from the MATLAB code required to run the LTS, reducing the complexity of implementing future changes. The LTS was benchmarked against the freeware tool OptimumLap and validated where possible against competition results. A Latin Hypercube sampling technique was employed to generate numerous input scenarios for the simulation, and a response surface fitted to the results to perform a sensitivity analysis. Results from this analysis indicate several areas to efficiently focus future resource allocation as well as attempting to quantify trade-offs. Optimum powertrain gear ratio and battery capacity for a proposed vehicle were specified using the tool.