Controller design using second order sliding mode algorithm with an application to a coupled-tank liquid-level system

A method for the design of second-order sliding mode controllers is developed for a coupled two tank system. The standard sliding mode (SSM) controller produces oscillations in the closed-loop system. The newly invented second order sliding mode controller (SOSMC) not only retains the robustness properties of the classical sliding mode controller (SMC) but also eliminates the drawback of the SMC that is high frequency chattering due to high frequency switching. The high frequency switching can excite the unmodelled dynamics and makes the system unstable. The work presented in this paper is the super twisting controller design for a coupled two tank system. Robustness of the controllers is analyzed and dynamic bounds for the uncertainty are found for a class of this system. The application of this technique to the two-tank system to solve a robust tracking problem is presented.