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

Abstract

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) H∞ control algorithm, which is dedicated to chatter suppression of turning process. The proposed MFFFB H∞ controller is established by utilizing the reinforcement Q-learning along with the generalized Kalman-Yakubovich-Popov (GKYP) lemma. Unlike available entire frequency domain (EFD) H∞ controllers, the proposed approach facilitates a less conservative implementation since the H∞ 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 H∞ 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 H∞ 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 H∞ controller generates significant improvement in chatter-free region compared with EFD H∞ controller and conventional FFB H∞ controller.