Modelling Relay Responses for Multivariable Processes

Abstract

Due to interactions between input and output, closed-loop multivariable systems yield undesirable responses. To characterize these responses through modelling, a systematic approach is followed to derive analytical expressions for relay feedback responses on 2×2 Multiple-Input Multiple-Output (MIMO) systems. This is based on the observation that a relay feedback test consists of a series of step inputs and a stable limit cycle implies a convergent infinite series. These analytical expressions in a closed-form solution are useful to identify unknown system parameters, understand interactions and diagnose faults at an early stage, and subsequently for autotuning.

Keywords:

• Relay feedback
• Autotuning
• Multivariable
• Modelling