High-fidelity Modelling of an Electric Sport Utility Vehicle

Abstract

The development and validation of a high-fidelity dynamic model of an electric sport utility vehicle (SUV) is presented. The developed model of the electric vehicle system consists of two main subsystems: the high-fidelity vehicle dynamics model, and the high-fidelity electrical powertrain subsystem that is comprised of an alternating-current (AC) electric motor, a 3-phase inverter, and motor controllers. The high-fidelity models are developed in MapleSim and Simulink. Specifically, the high-fidelity vehicle dynamics model is developed using the MapleSim multibody and tire dynamics libraries. A simple longitudinal model is developed in Simulink to cross-validate the high-fidelity MapleSim model by comparing the vehicle dynamics responses of the two models.

The electrical powertrain components are developed and implemented in the following order: the AC electric motor is developed first followed by the 3-phase voltage source inverter. Motor controllers are developed next, and lastly the electrical powertrain subsystem is assembled by combining the AC electric motor, the 3-phase inverter, and the motor controllers. Previous research results and literature on AC electric motors are studied thoroughly to develop an AC electric motor model suitable for electric vehicle applications. The 3-phase voltage source inverter is developed to convert a constant voltage signal into 3-phase AC voltage signals that are used by the AC electric motor. Lastly, the motor controllers are designed to control the electric motor responses, such as developed motor torque or speed. At each stage of the powertrain component model developments, the developed models are verified by studying their simulation results. Experimental motor data from vehicle testing is available, so the experimental torque-speed curves are used to tune the AC electric motor parameters.

Once all the individual components are developed and validated, the high-fidelity electric vehicle system is created in Simulink by assembling the MapleSim vehicle dynamics model and the electrical powertrain subsystem which is developed in Simulink. For the models developed in MapleSim, they are exported as Simulink blocks so that they could be run alongside with the Simulink models. A driver controller is included to calculate required reference motor torque to track a reference speed input. A brake module is designed to simulate a brake system found in an electric vehicle where regenerative and mechanical brake systems cooperate to deliver braking torque. The electric vehicle system model is simulated using the driving cycles that represent city, highway, and aggressive driving scenarios. The simulation results, such as the vehicle's longitudinal speed and developed motor torque and currents, are presented and studied to verify that the electric vehicle system can operate under different driving scenarios.