Design of a nonlinear dynamic output feedback controller based on a fixed-time RBF disturbance observer for a PEMFC air supply system

The efficiency and service life of proton exchange membrane fuel cells (PEMFCs) are critically related to the control performance of the air supply system. The unmeasured state variables and system disturbances seriously affect the control performance of the air supply system. This research focuses on developing a nonlinear dynamic output feedback controller to address the multivariable, nonlinear and unmeasurable state of the air supply system. First, a simplified control-oriented model of the air supply system dynamic behavior is developed, and the modeling uncertainties are estimated and compensated using two fixed-time radial basis function neural network disturbance observers (FRBFNN-DOBs). Second, a nonlinear reduced-order cathode pressure observer is designed, and the observer error is bounded for the unknown bounded disturbance. Third, an observer-based nonlinear cathode pressure tracking controller and supply manifold pressure tracking controller are designed using backstepping method. Considering the estimation error of the FRBFNN-DOBs, the robustness of the closed-loop system is proven using the input-to-state stability theory; furthermore, the upper bound of the tracking error and the convergence rate of the initial error are obtained, which is useful to design the controller parameters. Finally, simulation results demonstrate that the designed controller is more advantageous and effective than the PID and MPC.