Model-free finite frequency Hø control for active chatter suppression in turning

Regenerative chatter is an extremely harmful phenomenon in machining, which generally results in overcut and rapid tool wear. This paper presents the design, analysis, and verification of a novel model-free finite frequency band (MFFFB) Ho control algorithm, which is dedicated to chatter suppression of turning process. The proposed MFFFB Ho controller is established by utilizing the reinforcement Q-learning along with the generalized Kalman-Yakubovich-Popov (GKYP) lemma. Unlike available entire frequency domain (EFD) Ho controllers, the proposed approach facilitates a less conservative implementation since the Ho performance index is only designed for the concerned frequency band which implies the limited energies of the actuator are mainly focused on this band, and users can specify optimized frequency band according to the actual turning conditions. Furthermore, it permits the construction of Ho controller without any knowledge of the dynamic model of turning process, only the data measured from the system state and input are required. Besides, an iterative solution algorithm for Ho control on the basis of policy iteration is presented, which decreases the burden on manual parameter adjustment and capable of achieving the optimal solution. Simulation and experiment results demonstrate that the proposed MFFFB Ho controller generates significant improvement in chatter-free region compared with EFD Ho controller and conventional FFB Ho controller.