des2tf

Scilab Function
Last update : April 1993

des2tf - descriptor to transfer function conversion

### Calling Sequence

  `[S]=des2tf(sl)`
  `[Bfs,Bis,chis]=des2tf(sl)`

### Parameters

- `sl`: list (linear system in descriptor form)
- `Bfs, Bis`: two polynomial matrices
- `chis`: polynomial
- `S`: rational matrix

### Description

Given the linear system in descriptor form i.e. `Sl=list('des',A,B,C,D,E)`, `des2tf` converts `sl` into its transfer function representation:

    S=C*(s*E-A)^(-1)*B+D

Called with 3 outputs arguments `des2tf` returns `Bfs` and `Bis` two polynomial matrices, and `chis` polynomial such that:

    S=Bfs/chis - Bis

`chis` is the determinant of `(s*E-A)` (up to a xcative constant);

### Examples

    s=poly(0,'s');
    G=[1/(s+1),s;1+s^2,3*s^3];
    Descrip=tf2des(G);Tf1=des2tf(Descrip)
    Descrip2=tf2des(G,"withD");Tf2=des2tf(Descrip2)
    [A,B,C,D,E]=Descrip2(2:6);Tf3=C*inv(s*E-A)*B+D

### See Also

`glever`, `pol2des`, `tf2des`, `ss2tf`, `des2ss`, `rowshuff`,

### Author

F. D.