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.TH augment 5 "April 1993" "Scilab Group" "Scilab Function"
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augment - augmented plant
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[P,r]=augment(G,flag1,flag2)
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: linear system (\fVsyslin\fR list), the nominal plant
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: one of the following (upper case) character string:
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\fV 'S' \fR, \fV 'R' \fR, \fV 'T' \fR
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\fV 'SR' \fR, \fV 'ST' \fR, \fV 'RT' \fR
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: one of the following character string:
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\fV 'o' \fR (stands for 'output', this is the default value) or \fV'i'\fR
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: linear system (\fVsyslin\fR list), the ``augmented'' plant
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: 1x2 row vector, dimension of \fVP22 = G\fR
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If \fVflag1='SRT'\fR (default value), returns the "full" augmented plant
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\fV 'S' \fR, \fV 'R' \fR, \fV 'T' \fR refer to the first three (block) rows
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of \fVP\fR respectively.
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If one of these letters is absent in \fVflag1\fR, the corresponding
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row in \fVP\fR is missing.
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If \fVG\fR is given in state-space form, the returned \fVP\fR is minimal.
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\fVP\fR is calculated by: \fV[I,0,0;0,I,0;-I,0,I;I,0,0]*[I,-G;0,I;I,0]\fR.
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The augmented plant associated with input sensitivity functions, namely
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[ I | -I] -->'S' (input sensitivity)
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[ G | -G] -->'R' (G*input sensitivity)
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P = [ 0 | I] -->'T' (K*G*input sensitivity)
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is obtained by the command \fV[P,r]=augment(G,flag,'i')\fR. For
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state-space \fVG\fR, this \fVP\fR
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is calculated by: \fV[I,-I;0,0;0,I;0,0]+[0;I;0;I]*G*[I,-I]\fR
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and is thus generically minimal.
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Note that weighting functions can be introduced by left-multiplying
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\fVP\fR by a diagonal system of appropriate dimension, e.g.,
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\fV P = sysdiag(W1,W2,W3,eye(G))*P\fR.
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Sensitivity functions can be calculated by \fVlft\fR. One has:
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For output sensitivity functions [P,r]=augment(P,'SRT'):
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lft(P,r,K)=[inv(eye()+G*K);K*inv(eye()+G*K);G*K*inv(eye()+G*K)];
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For input sensitivity functions [P,r]=augment(P,'SRT','i'):
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lft(P,r,K)=[inv(eye()+K*G);G*inv(eye()+K*G);K*G*inv(eye()+G*K)];
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G=ssrand(2,3,2); //Plant
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K=ssrand(3,2,2); //Compensator
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T=lft(P,r,K); //Complementary sensitivity function
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Ktf=ss2tf(K);Gtf=ss2tf(G);
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Ttf=ss2tf(T);T11=Ttf(1,1);
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Tn=Oloop*inv(eye(Oloop)+Oloop);
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[Pi,r]=augment(G,'T','i');
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T1=lft(Pi,r,K);T1tf=ss2tf(T1); //Input Complementary sensitivity function
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T1n=Oloop*inv(eye(Oloop)+Oloop);
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clean(T1tf(1,1)-T1n(1,1))