— Function File: [xinf, x_ha_err] = hinfsyn_ric (a, bb, c1, d1dot, r, ptol)

Forms

          xx = ([bb; -c1'*d1dot]/r) * [d1dot'*c1 bb'];
          Ha = [a 0*a; -c1'*c1 - a'] - xx;

and solves associated Riccati equation. The error code x_ha_err indicates one of the following conditions:

0

successful

1

xinf has imaginary eigenvalues

2

hx not Hamiltonian

3

xinf has infinite eigenvalues (numerical overflow)

4

xinf not symmetric

5

xinf not positive definite

6

r is singular