Disturbance Observer-Based-Model-Free Adaptive Fuzzy Fractional-Order Prescribed Performance Control for Nonlinear PEMFC System with Uncertainties and Performance Constraints

This paper focuses on developing a novel disturbance observer-based-model-free adaptive fuzzy fractional-order prescribed performance control (MF-AFFOPPC) to address several control problems of the polymer electrolyte membrane fuel cell (PEMFC) such as unmeasurable variables, time-varying disturbance, uncertainties, and performance constraints. First, a dynamic model of the fifth-order nonlinear PEMFC air supply system is developed, and then an internal state estimation is designed using sliding mode disturbance observer 1 (SMDO1) to estimate the cathode pressure (CP) and reconstruct the oxygen excess ratio (OER). Second, an ultra-local model (ULM) is used to reformulate the complex nonlinear PEMFC air supply system, and another SMDO2 based on an intelligent proportional integral controller (SMDO-iPI) is developed to approximate the unknown, uncertain system dynamics simultaneously. Furthermore, an adaptive fuzzy compensator is constructed to approximate and compensate for SMDO2 error. Third, based on SMDO-iPI, adaptive fuzzy compensator, and fractional-order prescribed performance control algorithm, the MF-AFFOPPC strategy is designed. Moreover, the Lyapunov theorem is used to verify the stability of MF-AFFOPPC via a closed-loop system. Finally, the nonlinear PEMFC air supply system model with the proposed controller is realized in MATLAB/Simulink environment, and the simulation results are obtained to show the superiority and effectiveness of the proposed technique.