Design of IMC Controller for TITO Process with Dynamic Closed-Loop Time Constant

An IMC controller is designed for two input and two output (TITO) processes with dead time where the closed-loop time constant is varied depending on the process operating condition. For a TITO process, proper decoupling can minimize the loop interaction. Here, we develop an inverted decoupler so that the TITO process can be decoupled into two SISO processes. Each SISO process is considered to be a first-order process with dead time (FOPDT) and IMC controller is designed for each FOPDT process. To make the controller structure proper, we incorporate a first-order filter with closed-loop time constant (lambda) which is the only tunable parameter. Instead of a fixed value, dynamic nature is incorporated in selecting the value of lambda based on a simple mathematical relation. Superiority of the proposed IMC controller is verified through performance comparison with the well-known multiloop tuning relations.