Design of Multivariable Controllers by Direct Synthesis: Theory and Experimental Implementation

A technique for designing truly multivariable controllers by direct synthesis is presented for multivariable processes with and without time delays. The technique generalizes the SISO direct synthesis method in which feedback controllers are designed to achieve a pre-specified desired closed loop behavior. As with the SISO counterpart, the multivariable and time delay extensions are shown to take on the form of truly multivariable versions of the popular conventional PID feedback controllers for certain choices of the desired closed loop behavior. The procedure is illustrated via simulation and on an experimental laboratory scale mixing tank, where the performance is shown, as expected, to be far superior to that obtained with multiloop controllers.