Optimal cutting process stability in milling using active dynamic absorber

Abstract

The paper proposes a design concept for an active dynamic absorber in the milling process. A two-degree-of-freedom structural model for the milling is considered. Dynamic absorber masses are connected to the main system through active force generating systems which are piezoelectric pushers working as actuators. The suboptimal feedback gain is derived by the use of the optimal control theory, along with a numerical optimization package. The theoretical prediction of machine tool stability is carried out and verified by the transient responses in time domain under varying cutting conditions. The borderline of stability or the onset of machine chatter is obtained in terms of the critical axial depth of cut versus spindle speed. The corresponding chatter frequency for the threshold of stability is obtained also. Compared with the limit of stability under no control and under passive control, the stable range under optimal active control is increased appreciably. The transient responses in time domain and the harmonic responses in frequency domain are also substantially reduced by using such an active control system. Those comparisons show the effectiveness and superiority of the active control technique to suppress machine chatter in milling process.