Adaptive and robust control strategies for systems with actuator failure

In the present study, it is aimed to design a novel controller that is tolerant to actuator faults. The designed controller that uses robust adaptive control scheme maintains the system stability and desired closed-loop performance in the case of actuator faults. In the view of the control goal, a quadruple-tank system which comprises of two liquid pumps and level sensors is used as testbed. The system gives opportunity to obtain various plant structures being widely used in the literature by simply changing valve position of tank interconnections. A modified output-feedback multivariable model reference adaptive control (MRAC) scheme is proposed for the system that is prone to actuator faults. A unified comprehensive actuator fault model is presented. Then, some existing proper modifications that allow MRAC to gain the ability of actuator fault compensation controller is constructed by utilizing existing results and a new adaptation law that is based on a method first used for optimization purposes. The stability of proposed controller is proved and process simulation results are given to exhibit the effectiveness of the proposed scheme. The final control scheme, with some robustness modification by considering practical issues, is applied to the real process and it is shown that the control system leads to a faster smooth postfault transient response compared with similar methods. In addition it generates a smooth control signal without high frequency oscillations making the system less vulnerable to actuator damages