A new approach of EV modeling and its control applications to reduce energy consumption

Abstract

Efficient energy usage of electric vehicles (EVs) is an important concern, especially in relation to the use of battery energy. This paper presents a strategy to make the use of battery energy more economical by employing a new modeling approach. One of the existing EV models, called the motor-vehicle model, considers the motor and the longitudinal vehicle dynamics. In this study, the motor-vehicle model is further simplified by ignoring the drag force, which will be referred to as the simple model. In addition, we propose a new approach of EV modeling by including the battery dynamics into a motor-vehicle model and taking into account the drag force. This model is named the Integrated Battery-Electric Vehicle (IBEV) model. In order to demonstrate the usefulness of the proposed model, controllers are designed using linear quadratic integral (LQI) control. Each controller is designed for several test cases based on a linearized integrated model, after which specific test cases are carried out on a nonlinear IBEV model. From these models, the energy consumption is analyzed based on several performance indices under a number of combinations of settings, i.e. battery type (lithium-ion or lead-acid battery) and shaft model (rigid or flexible shaft). Further, an LQI controller with a Kalman filter is designed and its performance is compared to LQI controllers with 4th and 5th order Luenberger observers. The simulation results shows that the use of IBEV model reduces energy consumption compared to the use of simple model in controller design, and that the LQI controller with Kalman filter can reduce the noise effect and is more economical than the controllers with other observers.