Abstract

From the very beginning, metal cutting has had one troublesome obstacle in increasing productivity and accuracy, namely chatter. In machining, chatter is perceived as unwanted excessive vibration between the tool and workpiece, resulting in a poor surface finish and accelerated tool wear. It also has a deteriorating effect on the machine tool life, and the reliability and safety of the machining operation. The frictional and impact chatter are mainly due to the nonlinearity of the dry friction and the intermittent contact between the cutting tool and the workpiece. This thesis addresses the controller design for suppressing frictional and impact chatter in metal cutting systems. Piezoelectric actuators have become a standard option in positioning applications where the displacements must be small and highly accurate. In particular, ultra-precision manufacturing requires exceptionally fine and repeatable motions, making piezoelectric actuators a common choice. In this thesis, with the application of piezoelectric actuators in two directions x and y , an adaptive controller is developed to deal with unknown hysteresis combined with time delay. And an approach for adaptive control of frictional and impact chatter for metal cutting by piezoelectric actuator is presented. The developed control approach is based on an accepted model of the metal cutting process dynamics in the context of an approximate analysis of the resulting non-linear differential equations of motion. The stability analysis of the system is also given. The results of the numerical study of the adaptive control system shows the effectiveness of control of frictional and impact chatter with piezoelectric actuators.