Suppression on Effect of Cutting Forces Towards Tracking Performance in Milling Cutting Process Using State Observers

In milling cutting process, tracking performance of the CNC servo drive system is influenced by the characteristics of the cutting forces generated during the milling operation. The undesired frequency harmonics of the cutting force contributes negatively to the positioning accuracy; thus an effective compensation of these harmonics is desired. This paper presents results related to suppression of cutting forces in milling process for minimal impact on tracking performance using controller design approach. A cascade P/PI position controller was designed and numerically analysed in combination with an Inverse Model Based Disturbance Observer (IMBDO) plus Disturbance Force Observer (DFO). The effectiveness of this control approach was validated on the x-axis of the XY feed table of a ball-screw driven milling machine. Results showed that the combined approach of cascade P/PI controller with IMBDO plus DFO produced the best tracking control performance with reduction of 78.8% in magnitude component of the cutting forces using Fast Fourier Transform (FFT) analysis of the tracking errors; compared to individual dedicated approach using IMBDO (62.7%) and DFO (78.2%) respectively.