Phase shift monitoring based on mode-decoupled disturbance observer for chatter detection

Abstract

Strong excitation at the chatter frequency results in the change of the phase shift between the dynamic cutting force and the displacement depending on the phase characteristic of machine tool. In this paper, the chatter was detected by monitoring this phase shift with the mechanical energy factor (MEF). To construct the sensor-less MEF monitoring system on the ball-screw-driven system, mode-decoupled cutting force estimation was applied to two inertia model, and the phase shift was monitored in the vibration mode. Through a milling test, the chatter vibration was detected in the vibration mode with low computation cost and simple threshold.