Improved centralised control system for rejection of loop interaction in coupled tank system

ABSTRACT

In practice, majority of the processes are multivariable in nature and control of these processes is very intricate, due to the presence of non-zero diagonal elements in the system. This problem is addressed in the paper with the proposal of a centralised PI controller for controlling the interactive Two Input and Two Output processes. The proposed controller includes a diagonal PI controller and a decoupler element in off diagonal. To design PI controller, a well-known SISO tuning technique SIMC is considered and decoupler elements of off diagonal are designed using coefficient matching principle. The main diagonal controller improves the system performance, while the decoupler rejects the interaction; this improves the overall system. The designed controller performance is evaluated practically on a coupled tank system. The designed control system performance for both servo and regulatory operation is studied. The robustness analysis of the proposed method was analysed using inverse maximum singular value versus frequency plot by incorporating the multiplicative uncertainty in both input and output of the system.

KEYWORDS:

• Centralised controller
• coefficient matching
• decoupler element
• interactive processes
• robustness

Disclosure statement

No potential conflict of interest was reported by the authors.