The electric vehicle experiment : developing the theoretical model for 2.672

Abstract

The purpose of this project was to develop a computer simulation of the proposed 2.672 electric vehicle experiment (EVE) to estimate the magnitudes of the powers required in different components of the drive train, piecewise component and system efficiencies, and the information that would need to be collected to construct different component power models. The EVE model had to incorporate both acceleration and deceleration of the vehicle, using regenerative braking as needed. The resulting model can be used to evaluate the safety and feasibility of the EVE and determine sizes of relevant testing equipment required to implement the EVE. The model showed that the EVE could work safely and be modeled with a reasonable amount of effort by students in 2.672. The relatively low power flows (under 4kW) allow safe operation while the students are learning about the efficiencies of the individual components. The most inefficient component for the low speeds expected in the EVE was the motor/generator unit, though the efficiency increased as the torque increased. The gearbox and controller efficiencies were modeled as constants in the simplified model since the manufacturer's literature only quoted one value for the gearbox and since there was a lack of detailed information about the controller. The overall system energy recovery efficiency using regenerative braking was low, reaching a maximum of about 40% and falling as low as 10% when higher than expected power flows were used. The theoretical model was simplified by removing the effects of temperature and heat rise. Only with a built EVE can the actual performance of the system be characterized.