Chemical processes are multivariable systems with often coupled interactions between input and output variables

which conventional decentralized PID control system is difficult to maintain good control performance. In order to weaken coupling effect in multivariable system

PID dynamic pre-compensation matrix was designed by weighted optimization of many frequency points and diagonal dominance design criterion. A controller of the compensated diagonal dominance system was designed using positive Nyquist array design method. According to Nyquist stability criterion of diagonal dominance system

stable parameter range of feedback matrix was determined by plotting dominance degree curve and Gershgorin band. After that

dynamic compensator was designed by following single input single output system principle

which made the closed-loop system meet performance requirements of dynamic controls. Case studies show that centralized control systems designed by this method are more advantageous

simpler

and easier than decentralized control system.