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 *
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<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="ui_observer">
    <refnamediv>
        <refname>ui_observer</refname>
        <refpurpose>unknown input observer</refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>Syntax</title>
        <synopsis>
            [UIobs, J, N] = ui_observer(Sys, reject, C1, D1)
            [UIobs, J, N] = ui_observer(Sys, reject, C1, D1, flag, alfa, beta)
        </synopsis>
    </refsynopsisdiv>
    <refsection>
        <title>Arguments</title>
        <variablelist>
            <varlistentry>
                <term>Sys</term>
                <listitem>
                    <para>
                        <literal>syslin</literal> list containing the matrices <literal>(A,B,C2,D2)</literal>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>reject</term>
                <listitem>
                    <para>
                        integer vector, indices of inputs of <literal>Sys</literal> which are unknown.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>C1</term>
                <listitem>
                    <para>real matrix</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>D1</term>
                <listitem>
                    <para>
                        real matrix. <literal>C1</literal> and <literal>D1</literal> have the same number of rows.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>flag</term>
                <listitem>
                    <para>
                        string <literal>'ge'</literal> or <literal>'st'</literal> (default) or <literal>'pp'</literal>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>alfa</term>
                <listitem>
                    <para>real or complex vector (loc. of closed loop poles)</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>beta</term>
                <listitem>
                    <para>real or complex vector (loc. of closed loop poles)</para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsection>
    <refsection>
        <title>Description</title>
        <para>
            Unknown input observer.
        </para>
        <para>
            <literal>Sys: (w,u) --&gt; y</literal> is a <literal>(A,B,C2,D2)</literal> syslin linear system with
            two inputs w and u, w being the unknown input.
            The  matrices B and D2 of Sys are (implicitly) partitioned as:
            <literal>B=[B1,B2]</literal> and <literal>D2=[D21,D22]</literal>  with <literal>B1=B(:,reject)</literal>  and
            <literal>D21=D2(:,reject)</literal> where reject = indices of unknown inputs.
            The matrices <literal>C1</literal> and <literal>D1</literal> define <literal>z = C1 x + D1 (w,u)</literal>,
            the to-be-estimated output.
        </para>
        <para>
            The matrix <literal>D1</literal> is (implicitly) partitioned as <literal>D1=[D11,D12]</literal>
            with <literal>D11=D(:,reject)</literal>
        </para>
        <para>
            The data (Sys, reject,C1, D1)   define a 2-input 2-output system:
        </para>
        <programlisting role=""><![CDATA[
xdot =  A x + B1  w + B2  u
   z = C1 x + D11 w + D12 u
   y = C2 x + D21 w + D22 u
 ]]></programlisting>
        <para>
            An observer <literal>(u,y) --&gt; zhat</literal> is looked for the output z.
        </para>
        <para>
            <literal>flag='ge'</literal> no stability constraints
            <literal>flag='st'</literal> stable observer    (default)
            <literal>flag='pp'</literal> observer with pole placement
            alfa,beta = desired location of closed loop poles  (default -1, -2)
            J=y-output to x-state injection.
            N=y-output to z-estimated output injection.
        </para>
        <para>
            UIobs = linear system (u,y) --&gt; zhat such that:
            The transfer function: (w,u) --&gt; z  equals the composed transfer function:
            [0,I;        UIobs
            Sys]
            (w,u) -----&gt; (u,y) -----&gt; zhat
            i.e. transfer function of system {A,B,C1,D1} equals transfer function
            <literal>UIobs*[0,I; Sys]</literal>
        </para>
        <para>
            Stability (resp. pole placement) requires detectability
            (resp. observability) of (A,C2).
        </para>
    </refsection>
    <refsection>
        <title>Examples</title>
        <programlisting role="example"><![CDATA[
A=diag([3,-3,7,4,-4,8]);
B=[eye(3,3);zeros(3,3)];
C=[0,0,1,2,3,4;0,0,0,0,0,1];
D=[1,2,3;0,0,0];
rand('seed',0);w=ss2ss(syslin('c',A,B,C,D),rand(6,6));
[A,B,C,D]=abcd(w);
B=[B,matrix(1:18,6,3)];D=[D,matrix(-(1:6),2,3)];
reject=1:3;
Sys=syslin('c',A,B,C,D);
N1=[-2,-3];C1=-N1*C;D1=-N1*D;
nw=length(reject);nu=size(Sys('B'),2)-nw;
ny=size(Sys('C'),1);nz=size(C1,1);
[UIobs,J,N]=ui_observer(Sys,reject,C1,D1);

W=[zeros(nu,nw),eye(nu,nu);Sys];UIobsW=UIobs*W;
//(w,u) --> z=UIobs*[0,I;Sys](w,u)
clean(ss2tf(UIobsW));
wu_to_z=syslin('c',A,B,C1,D1);clean(ss2tf(wu_to_z));
clean(ss2tf(wu_to_z)-ss2tf(UIobsW),1.d-7)
/////2nd example//////
nx=2;ny=3;nwu=2;Sys=ssrand(ny,nwu,nx);
C1=rand(1,nx);D1=[0,1];
UIobs=ui_observer(Sys,1,C1,D1);
 ]]></programlisting>
    </refsection>
    <refsection role="see also">
        <title>See also</title>
        <simplelist type="inline">
            <member>
                <link linkend="cainv">cainv</link>
            </member>
            <member>
                <link linkend="ddp">ddp</link>
            </member>
            <member>
                <link linkend="abinv">abinv</link>
            </member>
        </simplelist>
    </refsection>
</refentry>
