Robust multivariable PID control for quadruple-tank process using an ILMI approach

This paper shows a robust multivariable PID controller design for a nonlinear quadruple tank process. The controller synthesis is reduced to an equivalent static output feedback control problem. The closed loop β /2 -stabilizable performance is guarantee for the linearized system with convex polytopic uncertainty. The algorithm is based on an iterative linear matrix inequality approach. The Parameter-dependent Lyapunov matrix functions, together with the Lyapunov matrix and the system dynamic matrix decoupling, are used in robust stabilizability conditions for conservatism reduction in the robust problem formulation. The design technique is illustrated with a numerical example.