Application of time-domain analysis in process control using approximate models

The study of approximate models in multivariable process control is extended to the time domain design method. This method has advantages over frequency domain methods, particularly in the multivariable case, facilitating predictions about the details of the closed loop transient performance if the real plant model is not available. Examples show that less conservative designs are obtained and simpler calculations than that in the frequency domain are required. The use in parallel of the two domain methods to check the stability criterion and robustness is suggested.