USING COARSE-GRAINED ENTROPY RATE TO DETECT CHATTER IN CUTTING

A new method for chatter detection in turning on a lathe is introduced . It exploits a significant change of cutting dynamics caused by the o nset of chatter. The changes are reflected in both dynamical and stati stical characteristics. Experimentally, the transition from chatter-fr ee cutting to chatter was achieved by a change of either cutting depth or turning frequency. For the characterization of cutting dynamics th e coarse-grained entropy rate is applied. A high value of the entropy rate is typical for chatter-free cutting, while for chatter a low valu e is typical. For the purpose of chatter detection the normalized valu e of the entropy rate is used and a characteristic threshold is define d. The value of the threshold is independent of cutting conditions. In addition to chatter detection, the entropy rate is applicable for qua litative physical interpretation of cutting process properties. (C) 19 98 Academic Press.