NONITERATIVE COMPUTATION OF INFIMUM IN H-INFINITY OPTIMIZATION FOR PLANTS WITH INVARIANT-ZEROS ON THE J-OMEGA-AXIS

A simple and noniterative procedure for the computation of the exact v alue of the infimum in the singular H(infinity)-optimisation problem i s presented, as a continuation of our earlier work. Our problem formul ation is general and we do not place any restrictions in the finite an d infinite zero structures of the system, and the direct feed-through terms between the control input and the controlled output variables, a nd between the disturbance input and the measurement output variables. Our method is applicable to a class of singular H(infinity)-optimisat ion problems for which the transfer functions from the control input t o the controlled output and from the disturbance input to the measurem ent output satisfy certain geometric conditions. In particular, the pa per extends the result of earlier work by allowing these two transfer functions to have invariant zeros on the jomega-axis.