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.TH abcd 1 "April 1993" "Scilab Group" "Scilab Function"
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feedback - feedback operation
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: linear systems (\fVsyslin\fR list) in state-space or transfer form,
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or ordinary gain matrices.
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: linear system (\fVsyslin\fR list) in state-space or transfer form
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The feedback operation is denoted by \fV /. \fR (slashdot).
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This command returns \fVSl=Sl1*(I+Sl2*Sl1)^-1\fR, i.e the (negative)
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feedback of \fVSl1\fR and \fVSl2\fR. \fVSl\fR is the transfer
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\fV v -> y \fR for \fV y = Sl1 u \fR, \fVu = v - Sl2 y\fR.
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The result is the same as \fVSl=LFT([0,I;I,-Sl2],Sl1)\fR.
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Caution: do not use with decimal point (e.g. \fV1/.1\fR is ambiguous!)
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S1=ssrand(2,2,3);S2=ssrand(2,2,2);
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//Same operation by LFT:
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ss2tf(lft([zeros(2,2),eye(2,2);eye(2,2),-S2],S1))
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//Other approach: with constant feedback
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BigS=sysdiag(S1,S2); F=[zeros(2,2),eye(2,2);-eye(2,2),zeros(2,2)];
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W1=Bigclosed(1:2,1:2); //W1=W (in state-space).
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ss2tf(S1*inv(eye()+S2*S1))
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lft, sysdiag, augment, obscont