Robust predictive minmax fault-tolerant control for multi-phase batch processes under partial actuator faults and asynchronous switching

In view of the uncertainties, partial actuator faults, asynchronous switching as well as unknown external interference in multi-phase batch processes, a robust predictive minmax fault-tolerant control approach is presented. First, considering that a controller and a system state cannot switch synchronously during switching, a match-and-mismatch switching model is constructed. Then, an output tracking error is introduced to establish an equivalent extended switching model. In this extended model, the robust control issue is transformed into the minmax optimization issue by establishing the minmax performance index. On this basis, the control laws with control input and interference input are designed. Second, sufficient conditions are given to assure the system separately has asymptotic and exponential stabilities in each phase and batch. By calculating the given sufficient conditions online, the gains of the control laws, and the minimum and maximum operating time under match and mismatch cases are obtained. With the maximum operating time, the controller receives the switching signal beforehand to eliminate the mismatch case of switching. Additionally, a robust criterion is supplied to confirm the system's robustness. Finally, a simulation study of an injection molding process shows that the approach is valid and feasible.