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 new output feedback control scheme is developed. In the proposed approach, a robust controller based on backstepping strategy is designed in order to ensure globally asymptotically stabilisation for a particular class of second-order nonlinear systems. Moreover, a model-based backstepping 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 observer converges in a finite time and leads to good estimate of the liquid level in the top tank as well as a good track of the liquid level in the bottom tank with the reference trajectory. To highlight the efficiency and applicability of the proposed control scheme, a comparison with proportional plus integral plus derivative controller as well as a simulation and experimental results are provided.