Expected interaction analysis for decentralized control on TITO systems: Application to IMC based PI/PID controller selection

One of the main issues in the control of multivariable processes are the effects generated by interaction terms. It is well known that the off-diagonal terms in the matrix transfer functions introduce interaction effects that are to be taken into account at the controller design stage. Even a full multivariable controller is an option, it is a fact that the most common solution found in industry is still the application of decentralized solutions based on PI/PID controllers. It is therefore of utmost interest to have design frameworks that allow well known approaches for single-loop PI/PID controllers to be applied on a MIMO decentralized setting. When decentralized control is to be used, special attention has to be paid to the potential instability caused by interaction effects generated by the control action on the other loop. It is in this sense that this paper provides a rather simple measure of interaction (defined in terms of the expected interaction to be generated into the control systems) with closed-loop design purposes. The resulting analysis equations will provide a framework where currently existing tuning approaches for single-loop PI/PID controllers can be applied to TITO systems within a decentralized approach. ICIC International © 2009 ISSN.