Development of Early-stage Performance Verification Method for Low-frequency Noise in Electric-powered Vehicle Batteries

Abstract

"This paper describes a method for configuring the starting sound of high-voltage electrical components installed on the batteries of hybrid electric vehicles (HEV) and electric vehicles (EV) for each particular unit, and introduces cases of application of this method in vehicle development. With regard to the stand-alone unit target performance of high-voltage electrical components for the purpose of satisfying vehicle demand, it used to be that the optimal battery capacity for the driving performance and target fuel consumption of each particular vehicle were determined and marketability of the vehicle was verified after deciding the battery installation location in light of conformance with laws and regulations as well as the perspective of battery safety in collisions. Consequently, vehicle body sensitivity to vibration according to different battery installation locations and complex battery structure transfer characteristics could not readily be accounted for in advance, making performance design of low-frequency battery noise originating in the structure challenging. Here, therefore, a stand-alone unit method of verification was created for the purpose of setting the targets for high-voltage electrical components. Specifically, synthesized sounds of the vehicle were calculated for various battery installation locations as the product of the vehicle vibration sensitivity at various points from the battery installation location to the driver’s ear location and the loads on the fastening points for each unit. When measuring loads on the fastening points of a unit, verification was performed using a fixed jig that took the target frequency into account. The results of verification at different battery installation locations (arranged under the first and second seats, and at the spare tire pan) and comparison of vehicle results with synthesized sounds confirmed that the synthesized sounds can reproduce the vehicle sound. This makes it possible to calculate the target values for a unit by reverse calculation from the synthesized sound. Application of this method makes it possible to verify the target values for a unit in advance from the combination of the envisioned battery installation location and the envisioned high-voltage electrical components, thus making early-stage verification possible."