Development Of On-road Test System For Automotive Brake Noise

On-road testing has always been an essential method for researching automotive NVH(Noise,Vibration,and Harshness).Unlike other types of NVH,brake squeal does not occur under all braking conditions and is highly dependent on specific factors such as brake pressure and speed.Currently,there are few professional brake noise test systems available for real vehicles in China.In this study,a user-friendly on-road brake noise test system was developed based on the virtual instrument software platform using Lab VIEW graphical programming language.This system consists of lower computer hardware and upper computer software.The hardware of the lower computer mainly consists of data acquisition cards,various sensors,and auxiliary equipment.For this study,the VK701 H data acquisition card is used,and Lab VIEW software is used for secondary development,which enables real-time acquisition of measurement data.The sensors used include sound pressure sensors,Hoswell pressure transmitters,and custom developed BDS/GPS velocity sensors.The main controller selected for the software is the STM32F072C8 chip,with hardware circuits designed for BDS/GPS signal reception,power conversion,reset,and program download.Finally,a hardware speed sensor is developed to produce the analog signal of the instantaneous speed of the moving vehicle.The upper computer software is the core of the on-road brake noise test system,which is divided into two main parts.In the first part,the STM32 Cube IDE development tool is used to create the system software for the speed sensor.The main program is written in C and includes subroutines for serial port data reception,data analysis,and D/A conversion.These subroutines analyze the ephemeris data.In the second part of the software development process,Lab VIEW is used to call library function nodes for data acquisition,data analysis,and function module design.Because the VK701 H data acquisition card doesn’t support the DAQ Acquisition Assistant,a bottom program must be written to call and configure its functions.The data analysis module examines brake noise characteristics in time and frequency.A wavelet threshold denoising algorithm module for the vehicle speed signal is created and designed based on Lab VIEW and MATLAB,using MATLAB’s signal feature analysis.The function module handles the data storage and path design for the brake squeal noise road test system of an automobile.In addition,the software interface is user-friendly,making it easy to operate.Once the overall brake noise road test system design is complete,it undergoes extensive debugging and is compared with the NI test system.Finally,an on-road brake squeal test is performed on an actual vehicle to verify the accuracy of the program design and the overall stability of the system.This test generates several data sets that are analyzed to determine the relationship between brake squeal noise and vehicle speed and brake pressure.The results are critical in optimizing the disc brake structure and reducing brake squeal noise,providing valuable insight for future improvements in this area.