Small UAV Hybrid Propulsion System

ABSTRACT: Small unmanned aerial vehicles are a useful military asset and new systems must provide greater endurance and stealthier operation. A problem is that current propulsion options provide either long endurance (internal combustion) or quiet operation (electric) but not both. Hybridization of the powertrain, incorporating both internal combustion and electric motor technology, has the potential to meet these demands; however, the complexity of its design and operation favors evaluation in the context of the aircraft and mission requirements. For this reason, in Phase I, hybrid propulsion models were developed and integrated into an aircraft model to predict performance under a standardized flight profile. Results indicated that the hybrid architecture was feasible, but that further component technology development would be required before endurance capabilities matched current capabilities. A Phase II program is proposed to mature the hybrid propulsion system concept through performance simulation using detailed component data, system controller development, hardware-in-the-loop simulation of the system and controller, and a benchtop demonstration of system operation under a simulated mission profile using representative hardware. The goal will be to demonstrate the operability of a hybrid propulsion system in a flight-like configuration to provide a solid foundation for further development of a flight-rated system. BENEFIT: The key contribution of a hybrid propulsion system is the capability to operate in a mode with the internal combustion engine off, reducing the operating noise of the aircraft until the energy storage system needs recharged using the internal combustion engine. This period of reduced operating noise will improve the survivability of small aircraft in a battle zone by making these aircraft less detectable. Since these aircraft operate at low altitudes, they are subjected to small arms fire, and do not have the weight capacity to carry armor to survive attacks, so reducing the detectability is the only option to improve their survivability. The hybrid architecture and controller development and demonstration that will be performed during Phase II may be applied to a variety of small aircraft currently operated by the Army, Navy, and Marine Corps, as well as to small organically designed aircraft that will be used by these services in the future.