DQIT: /spl mu/-synthesis without D-scale fitting

A new approach called D-Q iteration (DQIT) for synthesizing robust H/sub /spl infin// controllers is proposed to avoid D-scale fitting in D-K iteration (DKIT). Each iteration includes a D-step and a Q-step. In the D-step, the D-scale at each frequency is optimized as in DKIT, but D-scale fitting is not required. In the Q-step, the scaled H/sub /spl infin// problem is approximated by a finite-dimensional Q-parameter optimization problem in the frequency domain, using D-scales directly. Numerical examples show significant improvement in some cases.