Design, Modeling, and Testing of Hybrid-Electric Fixed-Wing VTOL Aircraft Propulsion System

The fixed-wing vertical takeoff and landing (VTOL) UAV has the advantages of both multi-rotor UAV and fixed-wing UAV, which can take off and land vertically in complex terrain while maintaining high speeds during the cruise. However, it puts forward higher requirements for the performance of the propulsion system. The full-electric power system can adapt to the complex propulsion device of fixed-wing VTOL UAV, but due to the low energy density of the battery, the aircraft has inadequate endurance capacity. The series hybrid-electric propulsion system has a flexible layout and wide operating range, which is well matched with the structure and power requirement of the fixed-wing VTOL UAV. Based on the principles of power matching and energy matching, a sizing and evaluation method for the hybrid-electric propulsion system was proposed. The full-electric propulsion system of a VTOL aircraft was transformed into a hybrid-electric propulsion system. The ground tests and flight tests were carried out. To comprehensively evaluate the performance of the propulsion system, a simulation model and performance evaluation system corresponding to the propulsion system was established, which can use the results of flight tests to predict flight time and energy consumption. The result shows that the endurance of the aircraft is increased from 2 h to 2.5 h after modification, which is consistent with the design requirement. The long endurance capacity of the series hybrid-electric propulsion system has also been confirmed. The design method can also be extended to other platforms for quick preliminary design of the hybrid-electric propulsion system.