Design of LQG/H∞ dynamic compensators for time varying non-linear feedback systems: circle criterion and guaranteed gain and phase margins

The objective of this paper is to present a synthesis method for dynamic compensators for multivariable time varying non-linear feedback systems. The design equations are developed for LQG and/or H_∞ dynamic compensators. The same method can be used for linear time invariant systems to design dynamic compensators with guaranteed gain and phase margins. The conservativeness of the design is reduced by computing an optimal diagonal scaling matrix and represents a new time domain solution to a sub-problem in mu-synthesis.