Would SISO IMC and SIMC tuning work for MIMO processes?

Most industrial processes being MIMO have multivariable interactions, which makes controller design a challenging task. As one input can potentially affect all outputs, a controller action in one loop could destabilize other loops. In this paper we explore the possibility of designing a decentralized PI controller for a multivariable process using SISO tuning rules. The objective is to identify if SISO IMC tuning rules would work for MIMO processes or not. It was found that under certain conditions, the SISO design is also applicable for multivariable systems. The tuning methods considered here are the internal model control (IMC) and Skogestad/ Simple IMC (SIMC). The tuning rules are simple, model based, they easily relate model parameters to controller parameters and work reasonably well for a wide range of processes. Simulations are carried out and various performance indices have been evaluated and compared against other methods to demonstrate the effectiveness of the proposed (IMC and SIMC) tuning methods for multivariable systems.