Averaging level control: An approach based on mass balance

Level control plays a fundamental role in the economic operation of many processes. This paper shows that interconnection and damping assignment passivity-based control, well known for electrical and mechanical applications, can be used to design high performance averaging level controllers for interconnected tank circuits, using physically motivated mass balance principles. The proposed method can deal with multiple tanks described by nonlinear dynamics with state constraints and rigourously establish the stability of the closed loop system. Furthermore, the transient behavior can be easily regulated, selecting the mass storage function assigned to the system, while keeping the control signal positive. As far as we know, none of the existing methods can address all these issues within a unifying framework. The simulation of a single tank and a multi-tank circuit illustrates the main issues raised in this paper.