Active Chatter Suppression in Turning by Simultaneous Adjustment of Amplitude and Frequency of Spindle Speed Variation

In machining processes, chatter suppression is very important for achieving a high material removal rate, good dimensional accuracy, and surface finish. With the merits of effectiveness and easy implementation, spindle speed variation (SSV) is regarded as a promising approach for chatter suppression. However, there is little research on the selection of SSV parameters for adaptive chatter suppression. Although the effectiveness of adaptively adjusting SSV amplitudes has been recently examined, the simultaneous adjustment of the SSV amplitude and frequency is expected to exhibit stronger adaptability since it achieves greater flexibility. In this paper, an active chatter suppression strategy is presented by simultaneously adjusting the amplitude and frequency of spindle speed variation. The effect of SSV parameters on stability improvement in turning processes including the tool wear is first investigated to demonstrate the necessity of simultaneously adjusting the amplitude and frequency for chatter suppression. Then, the proposed chatter suppression system is introduced, where two SSV parameters are simultaneously adjusted with optimal fractional-order proportional integral differential (FOPID) controllers to keep the chatter indicator close to a target value. Moreover, the FOPID controller is optimally tuned with the JADE algorithm. The effectiveness of the proposed method is verified by comparing simulated results of different SSV parameters adjusting strategies. Finally, machining tests are conducted to validate that the proposed chatter suppression method outperforms the existing SSV method in flexibility and effectiveness.