PROJECT TITLE :

Stability and Control Performance Analysis of Double EWMA Controller With Metrology Delay

ABSTRACT:

This paper mainly focuses on establishing the steadiness conditions of the double exponentially weighted moving average (d-EWMA) controller with metrology delay when the process experiences a general disturbance and analyzing its management performance underneath some typical sorts of method disturbance. The necessary and sufficient conditions for stability are established by Routh-Hurwitz criteria. It has been shown that if the process gain mismatch is bigger than four/three, metrology delay will build the feasible region of 2 weighting factors within the d-EWMA controller decrease, and also the larger metrology delay is, the smaller the feasible region is. Moreover, given two weighting factors, it is found that metrology delay will weaken the robustness of the d-EWMA controller. The influence of metrology delay on the asymptotical management performance is evaluated based mostly on asymptotical mean sq. error (AMSE). Optimal weighting factors and AMSE will be solved primarily based on analytical expression of the AMSE, that springs by using the Yule-Walker equations to avoid function summing limit operation. Through numerical simulations, it demonstrates that metrology delay may increase the variability of the method output below bound conditions. Finally, the chemical mechanical polishing process in semiconductor producing is employed to illustrate the validity of theoretical results.