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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) INRIA -
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
*
-->
<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xmlns:scilab="http://www.scilab.org" xml:lang="en" xml:id="augment">
<refnamediv>
<refname>augment</refname>
<refpurpose>augmented plant</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>[P,r]=augment(G)
[P,r]=augment(G,flag1)
[P,r]=augment(G,flag1,flag2)
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term>G</term>
<listitem>
<para>
linear system (<literal>syslin</literal> list), the nominal plant
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>flag1</term>
<listitem>
<para>
one of the following (upper case) character string: <literal> 'S' </literal>, <literal> 'R' </literal>, <literal> 'T' </literal> <literal> 'SR' </literal>, <literal> 'ST' </literal>, <literal> 'RT' </literal> <literal> 'SRT' </literal>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>flag2</term>
<listitem>
<para>
one of the following character string: <literal> 'o' </literal> (stands for 'output', this is the default value) or <literal>'i'</literal> (stands for 'input').
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>P</term>
<listitem>
<para>
linear system (<literal>syslin</literal> list), the ``augmented'' plant
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>r</term>
<listitem>
<para>
1x2 row vector, dimension of <literal>P22 = G</literal>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
If <literal>flag1='SRT'</literal> (default value), returns the "full" augmented plant
</para>
<programlisting role=""><![CDATA[
[ I | -G] -->'S'
[ 0 | I] -->'R'
P = [ 0 | G] -->'T'
[-------]
[ I | -G]
]]></programlisting>
<para>
<literal> 'S' </literal>, <literal> 'R' </literal>, <literal> 'T' </literal> refer to the first three (block) rows
of <literal>P</literal> respectively.
</para>
<para>
If one of these letters is absent in <literal>flag1</literal>, the corresponding
row in <literal>P</literal> is missing.
</para>
<para>
If <literal>G</literal> is given in state-space form, the returned <literal>P</literal> is minimal.
<literal>P</literal> is calculated by: <literal>[I,0,0;0,I,0;-I,0,I;I,0,0]*[I,-G;0,I;I,0]</literal>.
</para>
<para>
The augmented plant associated with input sensitivity functions, namely
</para>
<programlisting role=""><![CDATA[
[ I | -I] -->'S' (input sensitivity)
[ G | -G] -->'R' (G*input sensitivity)
P = [ 0 | I] -->'T' (K*G*input sensitivity)
[-------]
[ G | -G]
]]></programlisting>
<para>
is obtained by the command <literal>[P,r]=augment(G,flag,'i')</literal>. For
state-space <literal>G</literal>, this <literal>P</literal>
is calculated by: <literal>[I,-I;0,0;0,I;0,0]+[0;I;0;I]*G*[I,-I]</literal>
and is thus generically minimal.
</para>
<para>
Note that weighting functions can be introduced by left-multiplying
<literal>P</literal> by a diagonal system of appropriate dimension, e.g.,
<literal> P = sysdiag(W1,W2,W3,eye(G))*P</literal>.
</para>
<para>
Sensitivity functions can be calculated by <literal>lft</literal>. One has:
</para>
<para>
For output sensitivity functions [P,r]=augment(P,'SRT'):
lft(P,r,K)=[inv(eye()+G*K);K*inv(eye()+G*K);G*K*inv(eye()+G*K)];
</para>
<para>
For input sensitivity functions [P,r]=augment(P,'SRT','i'):
lft(P,r,K)=[inv(eye()+K*G);G*inv(eye()+K*G);K*G*inv(eye()+G*K)];
</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
G=ssrand(2,3,2); //Plant
K=ssrand(3,2,2); //Compensator
[P,r]=augment(G,'T');
T=lft(P,r,K); //Complementary sensitivity function
Ktf=ss2tf(K);Gtf=ss2tf(G);
Ttf=ss2tf(T);T11=Ttf(1,1);
Oloop=Gtf*Ktf;
Tn=Oloop*inv(eye(Oloop)+Oloop);
clean(T11-Tn(1,1));
//
[Pi,r]=augment(G,'T','i');
T1=lft(Pi,r,K);T1tf=ss2tf(T1); //Input Complementary sensitivity function
Oloop=Ktf*Gtf;
T1n=Oloop*inv(eye(Oloop)+Oloop);
clean(T1tf(1,1)-T1n(1,1))
]]></programlisting>
</refsection>
<refsection role="see also">
<title>See Also</title>
<simplelist type="inline">
<member>
<link linkend="lft">lft</link>
</member>
<member>
<link linkend="sensi">sensi</link>
</member>
</simplelist>
</refsection>
</refentry>
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