Controller Tuning Algorithm For Mimo Processes

A MIMO (multi input-multi output process) system is one in which one input not only affects its own outputs but also one or more other outputs in the plant. Thus such processes are difficult to control due to the presence of the interactions. The interactions between input/output variables are a common phenomenon and the main obstacle encountered in the design of multi-loop controllers for interacting multivariable processes. Increase in complexity and interactions between inputs and outputs yield degraded process behavior. Such processes are found in process industries as they arise from the design of plants that are subject to rigid product quality specifications, are more energy efficient, have more material integration, and have better environmental performance. Applying the tuning methods for a SISO (Single input- Single output) system to multi-loop systems often leads to poor performance and stability. Much research has been focused on how to efficiently take loop interactions into account in the multi-loop controller design. Thus, unless proper precautions are taken in terms of control system design, loop interactions can cause performance degradation and instability. This leads to the development of different controller tuning methods. Many methods have been proposed, including the Detuning method, Sequential Loop closing (SLC) method, Relay auto-tuning method, and independent loop method. This paper presents different controller tuning methods for MIMO-multi input-multi output process.