Fuzzy logic based passive fault tolerant control strategy for a single-tank system with system fault and process disturbances

Aiming at the decreasing performance of single-tank level control system under the constraints of system fault and process disturbances. In this paper, the mechanism of fault- tolerant control (FTC) is set up for a class of single-input - single-output (SISO) single-tank level control system with system (leak) fault, and based on the established passive fault tolerant control (PFTC) strategy, a fuzzy logic plus PI controller based passive fault-tolerant control (PFTC) strategy is proposed and compared this PFTC strategy using fuzzy logic plus PI control and PFTC strategy using conventional PI feedback control. The considered system fault is leak fault. The fault warning is constructed according to the identification error came from the controlled system and system model. When the system fault occurs, fuzzy logic systems are used to identify and detected the faults, and the passive fault tolerant control (PFTC) method is employed to compensate the leak fault. The control performance and stability of the closed-loop system are rigorously investigated. Finally, simulation and real-time results performance comparison of a single-tank level control system for two control strategies are presented and demonstrate the efficiency of the PFTC using two different controller modes in terms of mean square error (MSE) and root mean square error (RMSE). And hence the proposed PFTCS scheme using fuzzyplus PI controller gives superior performance in terms of error indices.