tailieunhanh - Metal Machining - Theory and Applications Episode 2 Part 7

Tham khảo tài liệu 'metal machining - theory and applications episode 2 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Monitoring and improvement of cutting states 313 Fig. Wear development estimated online for continuous change of both cutting speed and feed Ghasempoor et al. 1998 Fig. Integration of monitoring prediction and operation planning of cutting processes Obikawa et al. 1996 As in the first example wear was monitored indirectly by force measurements using neural nets but it was found that the axial and radial cutting position of the tool on the workpiece influenced the nets predictions dynamic force signals were influenced by the workpieces compliance. One net was used to monitor wear while a second wear rate both were trained by direct measurement rather than as in the first example by model predictions . 314 Process selection improvement and control Table Operation planning conditions and initial turning conditions Tool life Number of workpieces Longitudinal cutting length of workpiece Diameter of workpiece Work material Tool material Tool geometry Cutting speed Feed rate Depth of cut Lubrication VB mm 30 150 mm 100 mm C plain carbon steel carbide P20 -5 -6 5 6 15 15 150 m min mm rev mm dry Because of this a large amount of redundancy robustness was built into the nets with 34 inputs to each net as shown in Figure . Thirty of these were auto-regression AR coefficients of the feed force power spectrum as much information as could be extracted from it two were the total power of the spectrum of feed force and cutting force and two were the axial and radial positions of the cutting tool as already mentioned. Under the assumptions of the AR model the power spectrum was defined as pPn jw Ps j w --- ---- p 1 2 ----- ------- p 1 E akz-k k 1 where p is its order and also the number of peaks in the spectrum Pn jw is the white noise power spectrum ak is the kth AR coefficient and z eJ w. In this case p was chosen to be 30 by the Akaike Information Criterion AIC - Akaike 1974 . The outputs from the two nets the flank wear VB t .