Continuation Method for the Modified ZieglerNichols Tuning of Multiloop Control Systems

Multiloop control systems are often used for industrial multivariable processes because of their simplicity. To design multiloop control systems, single-input single-output (SISO) methods that guarantee specified closedloop characteristics can be applied. Because the design equations are nonlinear due to loop interactions and may cause computational difficulties, a continuation method is proposed to obtain the solutions. By choosing the interaction level as a continuation parameter, we can design multiloop control systems without worrying about numerical difficulties such as divergence. To illustrate the approach, the modified Ziegler-Nichols method is applied to design multiloop control systems.