H_inf(1)

NAME
h_inf - H-infinity (central) controller

CALLING SEQUENCE
[Sk,ro]=h_inf(P,r,romin,romax,nmax)
[Sk,rk,ro]=h_inf(P,r,romin,romax,nmax)

PARAMETERS

P   : syslin list : continuous-time linear system (``augmented'' plant given in state-space form or in transfer form)

r   : size of the P22 plant i.e. 2-vector [#outputs,#inputs]

romin,romax
    : a priori bounds on ro with ro=1/gama^2; (romin=0 usually)

nmax
    : integer, maximum number of iterations in the gama-iteration.

DESCRIPTION
h_inf computes H-infinity optimal controller for the continuous-time plant P.

The partition of P into four sub-plants is given through the 2-vector r which is the size of the 22 part of P.

P is given in state-space e.g. P=syslin('c',A,B,C,D) with A,B,C,D = constant matrices or P=syslin('c',H) with H a transfer matrix.

returns ro in [romin,romax] and the central controller
Sk in the same representation as P.

(All calculations are made in state-space, i.e conversion to state-space
is done by the function, if necessary).

Invoked with three LHS parameters,
returns ro and the parameterization of all stabilizing
controllers:

a stabilizing controller K is obtained by
K=lft(Sk,r,PHI) where PHI is a linear system with
dimensions r' and satisfy:

H_norm(PHI) < gamma.
rk (=r) is the size of the Sk22 block and ro = 1/gama^2
after nmax iterations.

Algorithm is adapted from Safonov-Limebeer. Note that P is assumed to be
a continuous-time plant.

SEE ALSO
gamitg, ccontrg, leqr

AUTHOR
F.D. (1990)