刀具破损实时监控系统

A New Sensing System for Monitoring Tool Fracture in Situ Using Acoustic Emission

刀具监测是自动化加工过程控制与优化的重要组成部分.本文研究了刀具破损过程中声发射信号的时域与频域特征,介绍了利用声发射原理研制开发的刀具破损实时监控仪AEM-2000的硬件组成及工作原理.

Up to now, a few monitoring devices using acoustic emission have been developed. The main disadvantage of these devices is that the threshold should be set by operator. In this paper a new sensing system AEM-2000 designed and made at Northwestern Polytechncial University is presented. By means of self-instructed mode and programmable attenuator, the sensing system AEM-2000 can automatically determine the attenuation degree and calculate the criterion threshold. The self-instructed mode is required only for the first of a hatch of workpieces. For all subseqent workpieces, it is only necessary to recall the same two parameters above mentioned for memory. The best existing monitoring devices just contain computerized discrimination circuit, which executes the discrimination program. The authors have applied a patent for the double discrimination circuit used in AEM-2000, which consists of emergency and computerized discrimination circuit. The emergency discrimination circuit is used to detect the sudden appearance of tool fracture while the computerized circuit is executing some program. The emergency circuit consists of an analog comparator and a digital-analog converter which supplies the reference level for the comparator. Tests which employ AEM-2000 are condusted for turning, boring and drilling operations. The minimum detectable fracture area is 0.01 mm^2 and the successful rate is more than 90%.