College - Author 1
College of Engineering
Department - Author 1
Mechanical Engineering Department
Degree Name - Author 1
BS in Mechanical Engineering
John Fabijanic, College of Engineering, Mechanical Engineering Department
Project G.H.O.S.T aimed to produce a model transmission with a control system for high performance/racing electric vehicles to utilize the full capability of the electric motor at higher speed applications. Current electric vehicles have a large amount of torque and use a fixed gear ratio that compromises between both high and low speeds with performance peaking around 65 miles per hour. A typical electric motor used in this application has approximately 1800 ft-lbs of torque up to 5,000 rpm. Past approximately 5,000 rpm, the torque rapidly drops off and so does the overall vehicle performance. Though transmissions exist that could have sufficient gear ratios, typical transmissions are not built to withstand torque figures of an electric motor. Even once implemented, transmissions have a second problem of high RPM gaps between gears due to the large gear ratios which results in a difficulty shifting quickly. The current model design used the form factor of the Liberty’s Gears 5-speed Equalizer Transmission (dual counter shaft) but with smaller, 125cc Honda dirt bike gears. The housing was designed to contain the three shafts, bearings, shifter forks and recombining gear for the model. The model motor was a DIY electric skateboard motor with over 4,000 RPM max and 1.9 N-m of torque which brought the entire model transmission and output flywheel up to max speed before shifting in under the desired 6 seconds. The transmission was controlled using the STM Nucleo L467RG microcontroller, programmed using C++ to better utilize the microcontroller’s high processor speed of 80 MHz. Finally, the system was tested based upon the ability to hit the engineering requirements and tuned for shifting speed using model gains.