Graphical methods for computation of stabilizing gain ranges for TITO systems

Effective graphical methods are presented to exactly compute stabilizer gain ranges for a two-input two-output (TITO) plant. Our approach determines those critical gains which result in pure imaginary roots of the characteristic equation and establish the stabilizing boundaries. For a fixed plant, the gain ranges of a decentralized stabilizer are obtained, whereas, for a parameterized plant, the gain range of central stabilizer is given in terms of the common time delay of the plant. Examples are provided for illustration and comparison with other methods.