Research On State Monitoring Of Machine Tools Based On Load Current Signal

By the monitoring of machine state, we can not only understand whether the operation is running correctly, but also help enterprise to make a reasonable amount of the allocation of tasks, and then optimize the entire production process. Through monitoring machine states and the time it spends, we can provide more detailed production information for enterprise managers. So they can not only get production efficiency of the machine by comparing idle time with processing time, but also get the production efficiency of one machine through comparing the time of some identical machines spent on a particular processing. We can get this machine utilization, in order to improve the utilization of machine tools in time, to avoid unnecessary low-load or high load operation, and the waste of productive forces.The study object of this paper is horizontal lathes. Put forward to make the current signal which is convenient measurement as characteristic signal. By analyzing the current signal to monitor machine state, such as end face cutting, external cutting, etc. we collected motor current signal in the state of idling, cylindrical cutting, end cutting etc. processing state in the experiment, then using various time-frequency analysis methods to processing signal, through the analysis of the results obtained the following results:(1) Monitoring the spindle speed of the lathe by the corresponding feature that extracted by time-frequency analysis.(2) Put forward the condition monitoring method based on wavelet packet transform. In the lathe processing, different transmission chain and processing methods will have different effects on the specific band of current signal, wavelet packet transform can decompose the signal frequency band in detail, and so, we can monitor the different states by wavelet packet coefficients of different frequency bands.(3) Put forward the condition monitoring method based on the load condition changes. Because load change trend is different in the different state of the lathe, and then extracted characteristics from the current signal, which is corresponding with the load change, so we can monitor the working status of lathe according to this.