Boring bar chatter control using a novel adaptive direct velocity feedback controller

In this paper, a new adaptive control system is presented for suppression of boring bar chatter in internal turning process. The vibration control system is consisted of electromagnetic actuator, boring bar, accelerometer and a novel adaptive control algorithm. The controller gain is adaptively adjusted according to the operating condition of actuator and the level of boring bar vibrations. Such that the consumed actuator power always remain proportional to the intensity of chatter vibrations due to cutting process. As a result, the gain adaptation algorithm is indirectly developed by using the dynamic characteristics of actuator-boring bar assembly. Firstly, the tunable parameters of adaptive controller are optimally identified by conducting impact tests. Secondly, the performance of adaptive controller is investigated during the internal turning of Aluminum alloy 6063-T6. The presented adaptive control system can improve the dynamic stiffness of boring bar as well as the critical limiting depth of cut on stability chart by at least 10 folds. Due to optimal performance of the adaptive controller, the dominant magnitude of boring bar’s power spectral density is successfully attenuated up to 78 dBs. Also, the roughness of cut surface is reduced from above 40 micrometers in control-off cutting test to below 5 micrometers in control-on test. Moreover, the actuator cost is considerably reduced for adaptive controller, in comparison to the optimal constant-gain integral controller. As a result, by using the proposed adaptive control algorithm, a smaller electromagnetic actuator with lower power capacity can be used for chatter suppression at the same cutting conditions.