Research On Aerial Spray Testing System And Spraying Flow Field For Small Unmanned Aerial Vehicle

In the field of agricultural and forestry plant protection,chemical control is still the most effective and economical method.Compared with the ground spraying machinery,with the characteristics of flexible take off and land,no subject to ground conditions,rapid response,high operating efficiency and the rotor wind field benefit,the small unmanned aerial vehicle(UAV)is suitable for outbreak plant protection in complex terrain(such as mountain and hill),dense orchard and other location difficult for ground vehicles.For the existing small plant protecting UAV,even with the rapid development in recent years,the lack of comprehensive three-dimensional quantitative research on rotor wind field,sprayingdropletflow field,interaction between rotor wind field and sprayingdroplet field,still affect the UAV plant protection effect.Therefore,based on the analysis of plant protecting UAV research status and the technical requirements of China's plant protection with UAV,in this paper,an indoor aerial spray testing system for small unmanned vehicle is designed and constructed to study the rotor wind field,sprayingdroplet flow field and the interaction between each other.First of all,the structure and function modules of the typical UAV aerial spraying system are analyzed.The electric helicopter and 6-rotor aircraft are chosen as the unmanned aerial vehicles.The tilt bed and hotizontal bed driven by 5 phase stepper motor are chosen tocontrol posture.The electric cylinder is chosen to control the height.The fan nozzle is chosen as the spraying nozzle and control by regulated power supply.The wind field is tested by anemometer.The spraying droplet field is tested by particle image velocimetry.After design and customize manufacture,the complete spray testingsystem composed of function modules is constructed,including: UAV,UAV remote control module,UAV posture control module,UAV operating height control module,stepper motor control module,aerial spraying system module and spraying effect testing module.The UAV aerial spray testing system is assemblied and ready for test.Then the numerical simulation of the UAV wind field and spraying flow field are carried out,includingthe flow field grid modelestablishment and numerical simulation scheme design.The influence of rotor speed,blade angle of attack,wind field area,fuselage and the rotor height on the flow field,the influence of nozzle position on the droplet distribution of the spraying field are stimulated and analyzed.All the study provide the basis for the further study of the UAV aerial spraying test.The wind field of unmanned helicopter and six-rotor UAV are tested respectively.First,the versatility and reliability of the testing system are verified.The maximum speed value of the wind field are tested and analyzed.The optimal fan nozzle installation positions of the unmanned helicopter and the six rotor UAV are preliminarydetermined by analyzing the distribution of the wind speed extreme value.According to the nozzle positions,orthogonal test with 3-factor and 4-level is designed.2 industry camera are used to capture and mosaic picture of whole spraying field based on the binocular vision principle.The laser diffraction images of the unmanned helicopter spraying field are captured and analyzed.All the images are analyzed with Tecplot and Image-J software.From the view of droplet velocity field and spraying area change,the influence of nozzle positions to spraying field are analyzed.Combined with the wind field analysis,under the influence of the unmanned helicopter wind field,the influence of nozzle installation positions on the spraying flow field are finally determined.Based on the analysis of the optimal nozzle position parameters,the field spraying test on citrus trees and bayberry trees are carried out with unmanned helicopter,six rotor UAV.Based on the spraying deposition and coverage of UAVs,it is found the spraying effect with optimal nozzle position parameters is better than that of normal nozzle position parameters.It is also found the spraying effect of unmanned helicopter is better than the six rotor UAV.Combined with wind field and spraying flow field characteristics of unmanned aerial vehicle,the reasons of differences are analyzed to provide basis for the UAV aerial spraying application.