In this article, the adaptive control of chatter vibrations in internal turning operations is addressed. The single-input and singleoutput (SISO) control system is composed of an electrodynamic shaker as the controllable actuator, an integrated electronics piezoelectric (IEPE) accelerometer as the feedback sensor, and a newly proposed control algorithm. A novel adaptive direct velocity feedback (DVF) controller is developed on the basis of the energy balance concept. The suggested gain adaptation algorithm dynamically adjusts the value of controller gain by considering the mutual interaction between the control system and the cutting process. The aim of the adaptive DVF controller is to maintain a reasonable balance between the rate of positive energy generated by the actuator and the rate of destructive energy absorbed by the boring bar due to chatter phenomenon, such that the stability of cutting process is remarkably improved with minimized actuation cost. The performance of the proposed adaptive chatter control system is experimentally verified during the internal turning of Aluminum alloy 6063-T6. The value of critical limiting depth of cut is anticipated to be nearly 0.2 mm for the slender boring bar. During the impact experiments, it has been observed that the adaptive DVF controller enhances the dynamic stiffness of boring bar by 11.4-fold. In addition, with the help of the presented adaptive controller, the stable cutting process is successfully performed with the maximum cutting depth of 2 mm. It has been observed that the amplitude of chatter vibrations is efficiently attenuated by at least 60 dB, adjacent to the dominant bending mode of the boring bar. The periodic chatter waviness is eliminated from surface texture and the roughness of cut surface is remarkably improved. Finally, it is proved that the presented control system can be effectively utilized in order to enhance the stability of active boring bar in deep internal turning operations.

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