Conditional integral sliding mode variable structure control for two-tank system

For a system with uncertainties, slide mode variable structure control method is a candidate control method. The well-known control variable chattering is the main obstacle to apply this method to practical system. Integral sliding mode variable structure control (ISMC) algorithm was proposed to solve this problem, however, the integration started at the beginning of the control process led to the degradation of the transient response. In this paper, a ”conditional” integral sliding mode variable structure control (CISMC) is proposed to control two-tank level control system to solve the transient performance degradation caused by the traditional ISMC. In the proposed algorithm, the integrator operates conditionally within the boundary layer. This ”conditional integrator” (CI) design not only guarantees the tracking accuracy with the decreasing chattering, but also improves the transient performance. The tank liquid level control system is usually treated as a paradigm to test the control algorithms. In this paper, four kinds of sliding-mode variable structure control methods is used to control the system to validate the performance. The simulation and experimental results show that the proposed CISMC has the superior performance as compared to the other three methods.