ABSTRACT
In general, multivariable systems involve multiple inputs (manipulated variables) and multiple outputs (measured variables) to deal with multiple control objectives associated with a process unit or a plant. However, the control engineer may also choose to consider all or a portion of the manipulated variables to satisfy all or a portion of the control objectives simultaneously. Such flexibility is responsible for one of the most important challenges in multivariable control design as it gives rise to a large number of alternative control structures. Multivariable systems have a number of unique characteristics due to interactions among the variables that demand careful consideration. The stability analysis of the closed-loop system was rephrased in the Multiple Inputs and Multiple Outputs (MIMO) case, by exploiting the notion of the newly defined MIMO closed-loop poles across the imaginary axis with the help of the Nyquist theorem. These now set the stage for analysis and design of MIMO controllers.
