Research Of Spark Plug Defect Detection Technology Based On Discharge Detection And Machine Vision

The spark plug is one of the important parts for the safe operation of the car,has the function of introducing tens of thousands of volts generated by the ignition coil into the engine cylinder to burn the mixed gas.At present,the detection of spark plugs on the market still stays on the outer surface of the spark plug observed by the human eye,and the internal insulating end faces are often overlooked.In addition,this method not only lacks accurate detection standards but is also prone to false negatives or misjudgments.This dissertation conducts a comprehensive study of the existing detection mechanism and analyzes the working principle of spark plug discharge.In order to break through the limitations of traditional spark plug detection efficiency,high false detection rate,and limited detection accuracy,a novel spark plug detection combining discharge detection and machine vision technology is proposed.Based on the pulse current method in discharge detection and the working mode of the ignition coil,a discharge control module is designed.At the same time,aiming at the problem of the pressure of relying on human eye detection,a novel spark plug defect detection algorithm combined with machine vision technology is designed to provide new perspectives and methods for the future detection of spark plugs and related industrial products.The main research contents as follows(1)The working principle of the spark plug is explored and analyzed,and the theoretical model of the internal dielectric discharge of the spark plug is established The difference in the insulation coefficient of different dielectrics within the spark plug determines the difference in the position of the spark plug.A new method of detecting the spark position of the spark plug instead of directly detecting the defect extraction is proposed,which overcomes the difficulty of internal detection of the spark plug and lays the foundation for the subsequent automatic determination of spark plug defects(2)Aiming at the problems that the common discharge mode voltage is difficult to regulate and the critical voltage points of various types of spark plugs are different,based on the theoretical study of discharge detection,the working mode of the ignition coil is combined with the local pulse current method,and the pulse width modulation signal is designed Discharge control module.Signal output and acquisition are carried out through NI DAQ,IGBT driver board,IGBT module,and ignition coil are used to realize the output of pulse voltage,which can reach 50kV(3)According to the characteristics of the spark plug detection site,combined with digital image processing methods,the spark plug image has been enhanced,segmented,and morphologically analyzed.Through experimental simulation,an improved center positioning method based on the Hough transform is proposed,and the defect is marked by Moore’s neighborhood tracking method.A set of algorithms for spark plug defect detection is successfully designed to achieve the spark plug discharge spark position mark and judge(4)According to the comprehensive experimental analysis of the designed spark plug defect detection scheme,and the use of electromagnetic theory,as well as control theory the construction of the voltage control module circuit is completed.It is proved through experiments that the magnitude of the duty cycle determines the amplitude of the output pulse voltage.At the same time,a software experiment platform was built to test the spark plug samples.The experimental results show that the high-pressure safe and measurable design of this scheme has a detection accuracy of up to 95%,which meets the actual needs of automation,industrialization,and standardization of spark plug defect detection.