U-parameter design of robust single-input single-output systems

A design approach is presented for feedback systems which are robustly stable and nominally optimal. This approach is referred to as U-parameter design and is represented as a direct extension of Q-parameter design, which is used to design feedback systems that are only nominally stable. The free design function U(s) in the U-parameter theory is a bounded real or a strongly bounded real function. The theory is applied to various nominal optimization problems including H² and H ^∞ optimization and classical design specification optimization