Model reference control of a two tank system

This paper deals with a new approach to the control design for a second-order nonlinear plant with time-delays. There are several methods that can solve this problem: the gain scheduling, exact lienarization, generalized transfer functions for nonlinear sysyems, etc., to name just few. The advantage of the solution proposed in this paper consists in its simplicity, modularity that can be used for a broad class of nonlinear systems and relatedness to several well established approaches that can be considered as its limit cases. Starting from a pole-assignment PD controller for the double-integrator plant generalized for a constrained control and equiped by a gain scheduling to respect the nonlinear plant dynamics, its structure is gradually extended by a model reference control and finally, by a nonlinear disturbance observer taking into account filtration of noisy signals and the non-modelled time-delays always present in control circuits. By using an example of a two-tank liquid level control in a hydraulic plant, performance of the resulting two-degree-of-freedom model reference control of nonlinear time-delayed systems with an integral (I) action will be evaluated by standard criterions.