Study Of Stability Monitoring In Milling Operations Using Spindle Motor Current

Milling is an advanced way of metal cutting, which is widely used in the rough andfinish machining of mold manufacturing，aviation industry and automobile industry.Instability in milling process leads to workpieces’ poor surface quality，shorter toollife,and even endangers the lives of operators and loses the property of plants. Therefore,study of stability monitoring in milling has a very important engineering significance. Thisthesis develops a method of stability monitoring based on spindle motor current in milling.The main research contents are as follows:(1) According to the comparisons of some common time-frequency analysis, this thesisidentifies the spindle motor current signal during machining by Hilbert-HuangTransform. The corresponding processing status information is accurately obtained.(2) According to functional requirements of acquisition system for spindle motor currentsignal, the platform used for acquiring multi-channel signals is developed, includingthe selection of hardware parts, the design of sensor interface circuit and the programsfor signal acquisition, processing and analysis, and so on.(3) According to the practicality of spindle motor current for stability monitoring, theoverall plan of stability monitoring are designed. and the corresponding experimentsare performed under different processing conditions.(4) Through the data collected by the experiments, the current signals of the stability andinstability in milling are analyzed by Hilbert-Huang Transform, the related featurevectors are extracted. And then the feature vectors are trained by Support VectorMachine, and the training mode is established. At last the training mode forrecognizing the test suite gets a classification accuracy rate about93.33%from theexperimental results, so the approach can meet the demand of stability monitoringapplication.