Tool-Wear Monitoring Based on Continuous Hidden Markov Models
In this work we propose to monitor the cutting tool-wear condition in a CNC-machining center by using continuous Hidden Markov Models (HMM). A database was built with the vibration signals obtained during the machining process. The workpiece used in the milling process was aluminum 6061. Cutting tests were performed on a Huron milling machine equipped with a Sinumerik 840D open CNC. We trained/tested the HMM under 18 different operating conditions. We identified three key transitions in the signals. First, the cutting tool touches the workpiece. Second, a stable waveform is observed when the tool is in contact with the workpiece. Third, the tool finishes the milling process. Considering these transitions, we use a five-state HMM for modeling the process. The HMMs are created by preprocessing the waveforms, followed by training step using Baum-Welch algorithm. In the recognition process, the signal waveform is also preprocessed, then the trained HMM are used for decoding. Early experimental results validate our proposal in exploiting speech recognition frameworks in monitoring machining centers. The classifier was capable of detecting the cutting tool condition within large variations of spindle speed and feed rate, and accuracy of 84.19%.
KeywordsSignal Processing and Analysis Remote Sensing Applications of Pattern Recognition Hidden Markov Models Tool-wear monitoring
- 2.Atlas, L., Ostendorf, M., Bernard, G.D.: Hidden markov models for monitoring machining tool-wear. IEEE, 3887–3890 (2000)Google Scholar
- 3.Bilmes, J.: What hmms can do. Technical reportGoogle Scholar
- 9.Liang, S.Y., Hecker, R.L., Landers, R.G.: Machining process monitoring and control: The state-of-the-art. ASME International Mechanical Engenieering Congress and Exposition, 1–12 (2002)Google Scholar
- 12.Rabiner, L.R., Juang, B.H.: Fundamentals of speech recognition. Prentice-Hall, New-Jersey (1993)Google Scholar
- 15.Zhang, G.M., Lin, C.: A hidden markov model approach to the study of random tool motion during machining. Technical reportGoogle Scholar