A Novel High-Order Sliding Mode Observer Based on Tanh-Function for a Fuel Cell UAV Power System with Uncertain Disturbance

Compared with the traditional unmanned aerial vehicle (UAV), the Fuel Cell (FC) UAV has the advantages of long endurance, high power density, low noise, low pollution, and excellent thermal stealth performance. The paper aims to solve the uncertain disturbance problem in a UAV hybrid power system consisting of a fuel cell stack and a battery bank, such as UAV maneuver flight and oxygen starvation at high altitude. A novel high-order sliding mode observer (HOSMO) based on hyperbolic tangent function tanh(x) is proposed to stable the DC bus voltage of the FC-UAV, which combines a dual-loop super-twisting (ST) high-order sliding mode control (HOSMC). In addition, the main control object is a floating interleaved Buck-Boost bidirectional DC/DC converter (FIB-BDC) with high-conversion-ratio, low current ripple, and low stress. Through the proposed control method in the paper, the robustness and dynamic response of the system can be improved, and the chattering problem of HOSMO will be eliminated. What's more, The stability of the proposed observer is proved by Lyapunov theory and the convergence conditions are given. Finally, theoretical analysis and simulation experiments validate the effectiveness of the proposed approach.