A closed-loop evaluation for regulatory control structure of multivariable system

In multivariable processes, control structure selection represented as the pairing of manipulated variables and controlled variables is a major concern during the design of multi-loop regulatory PID control system. Each pairing method has its application scope, and it is necessary to analyze and evaluate the closed-loop application effect of the system pairing. Based on the dynamic transmission ratio between manipulated variables and controlled variables under the closed-loop state, the degree of coupling for each loop is calculated for the system pairing, and the closed-loop evaluation which is achieved by the determination of whether the degree of coupling is within the threshold is proposed to determine whether the result is satisfied. This method can not only be used to compare several different pairing results during the design of control system, but also to evaluate the pairing which is currently applied and analyze whether another variables pairing is needed.