Adaptive LQR control to attenuate chatters in milling processes

Abstract

Chatters are induced by rigidity-flexibility coupling between tools and workpieces, which cause cutting disturbances, over cut and quick tool wear and hence greatly limits the workpiece machining efficiency and quality. To attenuate the chatter dynamics, traditional passive control methods usually decrease the spin speed or cutting depth at the cost of reducing machining efficiency. In this work, we investigate deeply on the structure of the cutting force variation matrix and then design an online system identification method based on the Fourier series. In this way, a Linear Quadratic Regulator adaptive control method is developed to greatly enlarge the chatter stability region in the Lobe Diagram. Moreover, the receding horizon and output rectification mechanisms are applied to overcome the external disturbances as well. The feasibility and superiority of the method are verified by the benchmark examples, where closed-loop stable operation points are remarkably increased and a higher productivity rate is thus achieved. © 2013 Springer-Verlag Berlin Heidelberg.