Research Of Car Brake Pad Internal Defects Detection System Based On DSP System

As China's current car brake pad manufacturing industry is lack of automaticquality inspection equipment, in this paper, we introduce a device to detect car brake pads by using computer control technology, digital signal processing and sensor technology. The devise will be put into use in one of a automotive friction material manufacturers in HangZhou. The subject will make the previous method of judging the quality of car brake pads by human ears replaced and this device can greatly enhance the detection efficiency and reduce labor intensity of the work, and to some extent, increase the reliability of identification.In this subject, we study the internal defects (bubbles, cracks) of car brake pads by knocking them. In this paper, we study the differeces between different types of car brake pads and the differeces when knocking at different positions of a same pad. By the use of digital signal processing technology and MATLAB analysis software, we analyze the signal by knocking the pad in time domain and in frequecy domian. After the sound signal spectrum analysis, differeces can be found between good quality brake pads and brake pads with defect quality. By extracting the charateristic variables of the sound signal in frequecy domain, using the software SPSS, a discriminant function can be established.On the hardware side, we design a device to control the quality testing of car brake pads systems. It uses DSP as main processor, and it can sample the sound by knocking the pads. After signal amplifying, low-pass filtering and analog-to-digital conversing, the signal of the sound turns to digital signal. And we use DSP to analyze the digital signal to identifying whether or not the car brake pads can be used in a car. The mainly components of the device hardware are signal amplification circuit, low-pass filter circuit, AD converter circuit, serial communications and display circuit modules. Some solutions are designed to make the system has good interference immunity and stability.On the software side, the DSP driver program which includes initial function, main loop and interrupt service routine is made of C language and assemble language. Main loop completes the testing process in accordance with the detection task. There are some software anti-jamming methods used in software design. This subject is based on experiment, which brings out a scheme to detect internal defects of car brake pads intelligently by knocking the surface of car brake pads. It can be used to judge the quality of car brake pads automatically and exactly, which provides a good platform for quality detection of car brake pads.