sensi sensitivity functions

## Syntax

                [Se, Re, Te] = sensi(G, K)
                [Si, Ri, Ti] = sensi(G, K, flag)

## Arguments

G

  standard plant (`syslin` list)

K

  compensator (`syslin` list)

flag

  character string `'o'` (default value) or `'i'`

Se

  output sensitivity function `(I+G*K)^-1`

Re

  `K*Se`

Te

  `G*K*Se` (output complementary sensitivity function)

## Description

`sensi` computes sensitivity functions. If `G` and `K` are given in state-space form, the systems returned are generically minimal. Calculation is made by `lft`, e.g., `Se` can be given by the commands `P = augment(G,'S')`, `Se=lft(P,K)`. If `flag` = `'i'`, `[Si,Ri,Ti]=sensi(G,K,'i')` returns the input sensitivity functions.

    [Se;Re;Te]= [inv(eye()+G*K);K*inv(eye()+G*K);G*K*inv(eye()+G*K)];
    [Si;Ri;Ti]= [inv(eye()+K*G);G*inv(eye()+K*G);K*G*inv(eye()+K*G)];

## Examples

    G=ssrand(1,1,3);
    K=ssrand(1,1,3);
    [Se,Re,Te]=sensi(G,K);
    Se1=inv(eye()+G*K);  //Other way to compute
    ss2tf(Se)    //Se seen in transfer form
    ss2tf(Se1)
    ss2tf(Te)
    ss2tf(G*K*Se1)
    [Si,Ri,Ti]=sensi(G,K,'i');
    w1=[ss2tf(Si);ss2tf(Ri);ss2tf(Ti)]
    w2=[ss2tf(inv(eye()+K*G));ss2tf(G*inv(eye()+K*G));ss2tf(K*G*inv(eye()+K*G))];
    clean(w1-w2)

## See also

- augment
- lft
- h_cl