Study On The Application Of FAI-EFI System In A Small UAV Engine

In recent years,UAV has found wide applications in the civil aerial such as photography,agriculture,express transportation,disaster relief,news reporting,and in military fields as drone airborne detection,electronic warfare and missile interception.Due to its simple structure,high power density and other characteristics,two-stroke reciprocating piston engine is generally used for small UAV propulsion power.The traditional two-stroke carburetor engine has the disadvantage of poor high altitude performance,because the fuel supply can not be modified to fit with the external environment.EFI technology,which can achieve better fuel atomization and controllability to fit environmental changes,can significantly improve UAV performance and reduce the two-stroke engine fuel consumption.This paper explored the EFI fuel system and its control methods on small UAV piston engine.Because most UAV engines are still using carburetor fuel supply in China,an EFI solution for the UAV engine is developed.The FAI-EFI system is applied to a 3W-56 i type UAV two-stroke gasoline engine.The design includes the replacement of the original carburetor system by the FAI_M10 inlet injection system,the use of an electronic throttle which is controlled by FAI EFI system ECU,using cylinder head temperature sensor,atmospheric pressure sensor and ambient temperature sensor which can percept flight altitude and engine operating condition,and use of CAN communication and RS422 communication.RS-422 communication is used for achieving the target speed of closed-loop control,and CAN communication for ECU calibration,diagnosis and ECU software upgrades.Hardware of the ECU was designed,including the circuit of power module,communication module,signal acquisition module,fuel injection module and electronic throttle module.The software program architecture and naming rules of function modules of ECU were deeply analyzed.The MCU layer driver,ECU layer driver,complex driver,service layer driver and application layer control strategy were developed according to the software architecture.Finally,the prototype was processed and the bench test was carried out.The working parameters of the engine were optimized by experiments.The experimental results showed that the FAI EFI system not only greatly improved the fuel consumption rate with respect to the original machine but also the power was greater than the original machine.The throttle opening closed-loop control mode,which based on target speed is verified stable.When the target speed changed,the actual speed can follow the change well.