| At present,the rapid development of China’s facility agriculture production technology,but also brought many problems,especially the greenhouse internal environment closed,the lack of pollination caused by the lack of natural pollination media,has been restricting the efficiency and yield of agricultural production.In recent years,UAV technology has been widely used in agricultural production,especially in pollination of hybrid rice.Therefore,this paper takes tomato as the research object and explores the models of greenhouse pollination UAV.The main research contents include the following aspects:(1)Aiming at the gas-solid coupling phenomenon between the downwashing flow field of UAV and tomato plants,the wind-induced vibration relationship between horizontal wind field and vertical wind field and tomato was studied through experiments.Through comparative analysis of two different wind fields of tomato flower vibration acceleration vibration frequency,vibration amplitude,finally it is concluded that horizontal wind field main vibration frequency of flowers,vertical wind field is mainly the vibration amplitude of the flower,in a horizontal wind speed is about3.94 m/s,the uav downwash flow field can make tomato pollination flowers.(2)Aiming at the operation environment of UAV in greenhouse,a design scheme of four-rotor culvert micro-pollination UAV was proposed.The overall layout of the UAV is determined,and its overall frame structure is clarified.The overall size of the micro-UAV is 140×140×40mm,and the structure layout is X-shaped.The overall parameters and components of UAV are analyzed,including the selection and determination of power devices such as rotor,culvert and motor.The fuselage,motor seat,control panel and other structures of UAV are designed.The selected rotor airfoil is NACA4309,and the model of hollow cup motor is 8520.Finally,the threedimensional geometry model of the four-rotor culvert micro pollination UAV is completed.(3)Based on the momentum theory,the aerodynamic models of the isolated propeller and the bypass propeller were established,and the numerical simulation analysis was carried out respectively.According to the flow charts of the bypass structure with different outlet angles and the velocity of the outlet plane in different directions,it was concluded that the better shunting effect could be achieved when the outlet Angle of the bypass was 30°.Fluent software is used to simulate and analyze the air flow field of the uav overall structure,and the velocity distribution diagram of different horizontal planes in the vertical direction below the UAV is obtained.The horizontal velocity at 100 mm plane can reach 4.2m/s,which is the best distance suitable for uav pollination.(4)Considering the uav’s own factors and operating conditions,PLA was selected as the processing material,and 3D printing technology was applied to complete the processing of culverted and rack parts.Then,the selected parts were assembled to obtain a preliminary test prototype,and the testability experiment was carried out.When the UAV flies around tomato plants,it can produce wind-induced vibration of tomato branches within the range of downwash flow field.The error between the test value and the simulation value in the lateral region of the uav’s downwash flow field within the range of 100 mm is less than 10%.With the flight of UAV,the horizontal velocity firstly increases and then decreases,and the maximum value is about 4.1m/s.The research results have reference significance for the application of greenhouse UAV pollination technology.In conclusion,the overall design of greenhouse pollination UAV is carried out in this paper.Through experiments and theoretical analysis,it is verified that the disturbance of the downwash flow field of UAV can make tomato carry out vibration pollination.This study provides a new method for greenhouse tomato pollination and lays a foundation for future research on uav pollination. |
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