Patent ID: 6249712
Filing Date: 2001-06-19
Classification: G05B

Abstract:
A method for adaptively controlling a process operating on a sequence of samples according to a recipe having recipe values, said method comprising the steps of:(a) initializing an adaptive controller by setting initial parameter values and setting nominal recipe values, said adaptive controller being described by a first parameter T.sub.r, a standard deviation of said first parameter s.sub.r, an extrapolated value T.sub.e3 of said first parameter, an extrapolated value of standard deviation s.sub.e3 of said first parameter, a model value T.sub.m2 (a) of said first parameter, a model value of standard deviation s.sub.m2 (b) of said first parameter, a mean value T(x).sub.p3 of said first parameter, a mean value of standard deviation s(x).sub.p3 of said first parameter, a desired mean value T.sub.d of said first parameter, and a desired mean value of standard deviation s.sub.d of said first parameter;(b) computing a model-predicted parameter value using first equation ##EQU3##(c) processing a first sample of said sequence, measuring a first parameter of said first sample multiple times to obtain a mean value and sample standard deviation for said first sample;(d) computing the resulting error of said first parameter and updating the parameters of said first sample by using equationsmin[T.sub.r -T.sub.m (a, x)].sup.2 Equation (6)subject to aandmin[s.sub.r -s.sub.m (a, x)].sup.2 Equation (7)subject to bwhereT.sub.m (a,x)=a.sub.0 +a.sub.1 x.sub.1 +a.sub.2 x.sub.2 +a.sub.11 x.sub.1.sup.2 +a.sub.12 x.sub.12s.sub.m (b,x)=b.sub.0 +b.sub.1 x.sub.1 +b.sub.2 x.sub.2 +b.sub.11 x.sub.1.sup.2 +b.sub.12 x.sub.12(e) processing at least a second sample and extrapolating to find the value of the next sample point and using it, as if it is the true sample, to update adaptive controller parameters by using equationsmin[T.sub.e3 -T.sub.m2 (a)].sup.2 Equation (10)subject to a;andmin[s.sub.e3 -s.sub.m2 (b)].sup.2 Equation (11)subject to b,(f) computing the optimum recipe to use on the next run by using the simultaneous nonlinear equationsT(x).sub.p3 =T.sub.d.fwdarw.T(x).sub.p3 -T.sub.d =0 Equation (12)ands(x).sub.p3 =s.sub.d.fwdarw.s(x).sub.p3 -s.sub.d =0 Equation (13)(g) repeating the above steps (b) through (f) until a stopping condition is met.