Desired-dynamics-based design of control strategy for multivariable system with time delays

Multiple-input-multiple-output (MIMO) processes with time delays commonly appear in chemical and industrial practice. For MIMO processes, a PID decoupling controller is devised based on unity feedback closed-loop control structure and combined with the characteristics of strong robustness of the Desired Dynamic Equation (DDE) method for two-degree-of-freedom (2-DOF) PID controllers. The design of the PID controller is achieved through setting a static decoupling controller on the input of the controlled process. And for additive and multiplicative uncertainty disturbance usually encountered in practice, the sufficient and necessary condition of guaranteeing robust stability of the control system is analyzed and a determination method is provided based on the spectral radius criterion. This controller can not only achieve a significant decoupling among the nominal responses of system outputs, but also realize the online tuning of adjustable parameter. Comparing with the deficiency of numerical calculation method, this design is simple and widely applicable. Finally, some simulation examples are supplied to demonstrate the superiority of the proposed method.