The Application of System identification method to characterize the performance of NiMH batteries in hybrid vehicles

Valaya Alongkorn Rajabhat University, Department of Industrial Management, 13180 Prathumthani, Thailand

Abstract

Nickel-metal hydride (Ni-MH) battery is one of the electric sources which is widely used in hybrid electric vehicles. As a result, it is important to understand the characteristics of Ni-MH battery which is connected to direct current machine in the vehicle. However, the crucial problem is the complexity of the vehicle system which deals with the charging and discharging process of battery in order to maintain the designated speed. The system is considered as a black box and the system identification method is utilized in to characterize the dynamic behavior of the system. The system inputs are battery voltage, armature current and state of charge (SOC) while the output is the speed of DC machine. However, the system identification method will not work properly if the available data available has played an importable role on the determination of the model. As a result, the data regarding all parameters were collected and transmitted to the data logger and used to construct different models. The results from the system identification method indicate that the autoregressive model with exogenous input (ARX) is the most appropriate model to explain the relationship between inputs and output. Therefore, the performance of hybrid vehicle related to the characteristics of Ni-MH batteries is elaborately characterized and this study leads to the effective maneuver.