Development Of A Set Of On-line System For Monitoring Audio Signals Produced From Machine Based On Virtual Instrument

Machine's audio signal with characteristic of convenient of acquisition and better real-time is mainly used in monitoring the mechanical equipment state and fault diagnosis. The up-to-date research has shown that machine type, machine state, running- speed of the basic shaft and tool wear can be all recognized by analyzing the audio signal. So, it is very practical to develop a set of on-line system for monitoring audio signals produced from the machine.Virtual instrument is the combination of computer technique, measuring technique and communication technique, which can realize the function of traditional instruments by computer programming. And the typical representative of virtual instrument is LabVIEW which is a kind of graphic programming software. So, LabVIEW with powerful function of processing signals is widely used in data processing technique, measuring technique, and instrument technique.A set of on-line system based on LabVIEW and traditional DAQ card for monitoring audio signals produced from the machine is introduced in the paper, which includes the hardware and the software. And the research of hardware involves selection of the noise level meter, connecting terminal and Data Acquisition card, and realization of the interface among them. The research of software includes many useful functions as following. The data sampling module transfers the signal into the computer through the system's hardware. The data saving module saves the waveform in computer's hard disk in the form of xls file in order to take further disposal later. The data processing module provide many kinds of processing methods including time-domain analysis (Mean, Variance, Mean Square Deviation, Peak Value and Auto Correlation), frequency-domain analysis (Auto Power Spectrum, Power Spectrum, Amplitude Spectrum and Phase Spectrum) and time- frequency domain analysis (Wavelet). The database module which can realize data management, adding and deleting records is completed by LabSQL. Long-distance monitoring enables the user monitoring the system by internet. The printing and report modules can realize characters, figures and tables of printing.The experiment applied in single lathe proves the system has characteristics of full function, convenient usage, good real-time, expandability and commonality.