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Wei-Lung Mao,Ding-Yu Shiu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.5
Precision contour tracking is one of the most important factors used to determine product quality in a machining tool. Aninterval type-2 fuzzy proportional–integral (PI) sliding mode control (IT2FPISMC) system is proposed herein to control themover position of the two-axis motion stage with optical encoder sensors for trajectory feedback. A type-2 fuzzy method thatcan handle rule uncertainties is developed to approach the unknown nonlinear systems. The PI term is used to approximatethe discontinuous control signal and mitigate the chattering phenomenon in the presence of unmodeled system dynamicsand external disturbances. The adaptive control laws are derived based on the Lyapunov theorem, such that the closed-loopstability is guaranteed, and the output tracking errors of the system asymptotically converge to zero. A non-uniform rationalB-spline interpolator with high accuracy is adopted in the biaxial linear stage. Moreover, typical circular, bowknot, heart,and star reference contours are tested. The results on the average tracking error and the tracking error standard deviationare experimented and compared to illustrate the performance of our proposed method. The tracking performance obtainedfrom the IT2FPISMC method is better than that of the conventional method. Furthermore, the proposed method can achieverobustness for tracking diff erent reference contours in industrial applications.