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<!DOCTYPE MAN SYSTEM "../../manrev.dtd">
<MAN>
  <LANGUAGE>eng</LANGUAGE>
  <TITLE>ss2des</TITLE>
  <TYPE>Scilab Function</TYPE>
  <DATE>April 1993</DATE>
  <SHORT_DESCRIPTION name="ss2des"> (polynomial) state-space to descriptor form</SHORT_DESCRIPTION>
  <CALLING_SEQUENCE>
    <CALLING_SEQUENCE_ITEM>S=ss2des(Sl)  </CALLING_SEQUENCE_ITEM>
    <CALLING_SEQUENCE_ITEM>S=ss2des(Sl,flag)  </CALLING_SEQUENCE_ITEM>
  </CALLING_SEQUENCE>
  <PARAM>
    <PARAM_INDENT>
      <PARAM_ITEM>
        <PARAM_NAME>Sl</PARAM_NAME>
        <PARAM_DESCRIPTION>
          <SP>: <VERB>syslin</VERB> list: proper or improper linear system.</SP>
        </PARAM_DESCRIPTION>
      </PARAM_ITEM>
      <PARAM_ITEM>
        <PARAM_NAME>flag</PARAM_NAME>
        <PARAM_DESCRIPTION>
          <SP>: character string <VERB>&quot;withD&quot;</VERB></SP>
        </PARAM_DESCRIPTION>
      </PARAM_ITEM>
      <PARAM_ITEM>
        <PARAM_NAME>S</PARAM_NAME>
        <PARAM_DESCRIPTION>
          <SP>: list</SP>
        </PARAM_DESCRIPTION>
      </PARAM_ITEM>
    </PARAM_INDENT>
  </PARAM>
  <DESCRIPTION>
    <P>
    Given the linear system in state-space representation 
    <VERB>Sl</VERB> (<VERB>syslin</VERB> list), with a <VERB>D</VERB> matrix which is either
    polynomial or constant, but not zero <VERB>ss2des</VERB>
    returns a descriptor system as <VERB>list('des',A,B,C,0,E)</VERB>
    such that:</P>
    <VERBATIM>
<![CDATA[
Sl=C*(s*E-A)^(-1)*B
   ]]>
    </VERBATIM>
    <P>
    If the flag <VERB>&quot;withD&quot;</VERB> is given, <VERB> S=list('des',A,B,C,D,E) </VERB>
    with a <VERB>D</VERB> matrix of maximal rank.</P>
  </DESCRIPTION>
  <EXAMPLE>
<![CDATA[
s=poly(0,'s');
G=[1/(s+1),s;1+s^2,3*s^3];Sl=tf2ss(G);
S=ss2des(Sl)
S1=ss2des(Sl,"withD")
Des=des2ss(S);Des(5)=clean(Des(5))
Des1=des2ss(S1)
 ]]>
  </EXAMPLE>
  <SEE_ALSO>
    <SEE_ALSO_ITEM>
      <LINK>pol2des</LINK>
    </SEE_ALSO_ITEM>
    <SEE_ALSO_ITEM>
      <LINK>tf2des</LINK>
    </SEE_ALSO_ITEM>
    <SEE_ALSO_ITEM>
      <LINK>des2ss</LINK>
    </SEE_ALSO_ITEM>
  </SEE_ALSO>
  <AUTHOR>F. D.; ;   </AUTHOR>
</MAN>
