Observer-based predictive liquid level controller for a double tank process

Abstract

This paper addresses the nonlinear control design problem for a state coupled two-tank liquid level system. For this system's dynamics, motivated by a desire to provide precise and economic liquid level control, a novel output feedback control scheme is developed. In the proposed approach, a model-based nonlinear generalized predictive controller combined with a high gain observer is designed for the two-tank liquid level system. Only one sensor is available to measure the liquid level in the bottom tank and the other process's state is assumed unavailable. The synthesized predictive control law is an explicit continuous solution of optimization problem and it arises from receding horizon index minimization. The observer converges in a finite time and leads to good estimation of the liquid level in the top tank. A good track of the liquid level in the bottom tank with the reference trajectory is achieved by the proposed controller. To highlight the efficiency and applicability of the proposed control scheme, simulation results are provided and discussed.