Design And Implementation Of Sound Measurement System For Motor Vehicle Engine Speed

In view of the fact that the vehicle exhaust remote sensing equipment cannot detect the real time working condition of the vehicle(in the course of driving),this thesis proposes a design scheme to judge the speed of the motor vehicle engine by sound,and then infer the real time working condition of the motor vehicle.The main content of the thesis is as follows:1.This paper introduces the general situation of remote sensing equipment,and designs the whole system scheme,including microphone array design and whole algorithm flow design.2.A blind signal separation techniques is proposed to separate the received aliasing signals.In the actual detection environment,there is not only the target lane signal,but also the aliasing effect of other adjacent lane signals.At the same time,because of the outdoor open environment,the external environment noise is not controllable,which will cause aliasing to the target signal and greatly affect the subsequent analysis.But the blind signal separation technology can solve the problem of the signal aliasing very well.3.The current lane signal identification and engine speed calculation design are carried out for the separated signal.Due to the interference of adjacent lane signals inthe current lane signal location process,it is difficult to use conventional method to distinguish our target signal from at least three signals.Therefore,it is proposed to solve this problem according to the difference of Doppler effect between different range signals.In the calculation of rotational speed,the signal needs to be calculated according to the frequency,but because the signal is not a single frequency signal and has the same frequency noise interference,in order to improving the accuracy of calculation,the method of detecting the main frequency of the target signal is presented,and needs to be filtered.4.The experiment verification test is carried out on the whole system.The reliability and accuracy of the system are verified through comparative analysis of actual data and test data.At the same time,it is proved that the design scheme is suitable for idle speed detection.