Robust Multivariable PI Control: Applications to Process Control

We consider the application of a recently developed “conditional integrator” technique for the output regulation of a class of nonlinear systems to process control systems. For a special choice of the controller parameters, our controller reduces to a finely tuned saturated PI/PID type controller with an anti-windup structure. This is of particular significance because while the application of nonlinear control strategies such as feedback linearization, adaptive/neural control and nonlinear model predictive control has reached considerable maturity for process systems, industrial practice has traditionally relied on PI/PID controllers. With our design, we provide both global regulation results (under state-feedback and when the control is not required to be constrained), and regional/semi-global results with saturated control and under output feedback. When applied to different process control problems, our simulation results show that good tracking performance is achieved, in spite of partial knowledge of the plant parameters.