Study On Mechanism And Method Of Wind-induced Vibration Pollination Of Greenhouse Tomato Based On UAV Downwash Flow Field

At present,tomato pollination technology in facility production still has major shortcomings,and it is difficult to adapt to the needs of green,efficient,and convenient modern agricultural production,which restricts the upgrading of the facility tomato industry.It is generally believed that wind-induced vibrations caused by wind can pollinate tomatoes.In recent years,with the rapid development of science and technology,UAV pollination has been widely used in rice,pear trees,pecans and other crops,and has achieved good results.The downwash flow field of UAV has the characteristics of high turbulence,strong spatiotemporal fluctuation and concentrated wind energy,which can cause complex wind-induced vibration of tomato flowers.In addition,UAV has a high degree of automation and low labor intensity,which can provide a new solution for facility tomato pollination.Therefore,the main work of this study includes:(1)In this study,common tomato and cherry tomato were used as research objects.The macro and Micro structures of tomato flowers were studied by in vivo observation,picking anatomy,paraffin section and Micro CT imaging.The results showed that there were high similarities between common tomato and cherry tomato in inflorescence morphology,flower macromorphology,anther microstructure,pollen morphology,pollen cysts dehiscence and flower vibratory pollination.On this basis,a three-dimensional model of tomato anthers was constructed,which provided a data basis for the research on the pollination kinetics of tomato flowers.(2)The contact process of tomato pollen particles was analyzed by using Hertz contact theory and JKR viscoelastic contact model.The modification method of tomato pollen grains by AFM probe was studied.The adhesion force and displacement of tomato pollen particles during contact were measured by AFM indentation test.JKR model and experimental results showed that the young's moduli of tomato pollen grains,pollen sacs,stigma and style was 4.82×10~4Pa,5.51×10~4Pa,2.31×10~5Pa and 1.01×10~5Pa,respectively.When the pollen particle probe approached the pollen particle,anther sac,style and stigma,the short-range attraction was-0.68n N,-2.11 n N,-1.38 n N and-27.18 n N,respectively.The AFM test was verified by centrifugal method.The results show that centrifugal method has the advantages of high precision,low cost and fast speed.It has a broad application prospect in the adhesion force analysis of micron scale particles.(3)The optimal levels of wind-induced vibration pollination are 30Hz,30mm and Z axis.The order of vibration parameters is vibration frequency>vibration direction>vibration amplitude.The optimal level of Buzz pollination pollination are300Hz,0.5mm and Z axis direction vibration.The order of the three factors is vibration amplitude>vibration frequency>vibration direction.When the vibration acceleration is lower than 59 m/s~2,tomato flowers had no pollination ability.When the vibration acceleration is greater than 59 m/s~2,the pollination rate was higher.When the vibration acceleration is between 353.5-2455.0 m/s~2,the pollination probability is very high.However,when the vibration acceleration exceeds 2455 m/s~2,the pollination possibility of flowers decreases sharply.Increasing vibration acceleration did not increase pollination rate,and even resulted in vibration damage of flowers.Whether it is wind-induced vibration pollination or buzzing vibration pollination,the vibration along the Z axis is the most conducive to pollination.Pollen adhesion and escape will reach a saturated and stable state in a short period of time(less than 0.4 s),and then the adhesion number and escape number will not change with the increase of time.(4)The downwash flow field of UAV has strong space-time pulsation characteristics,and the average wind speed can reach 10 m/s.The intensity of downwash flow field decreases with the increase of UAV flying altitude.Under the action of downwash flow field of UAV,tomato flower movement is superimposed by two parts:one is the swing of tomato flower's side branch,the other is the vibration of tomato flower itself,and the vibration of tomato flower itself is the main reason of tomato flower vibration pollination.When the hovering height of E360 UAV and TELLO UAV is 1.3 m and 1.0 m respectively,the average wind speed of downwash flow field is greater than 4.5 m/s.At this time,the wind-induced vibration generated by the downwash flow field of the UAV can make the pollination of tomato flowers stable and reliable.However,high wind speeds can cause wind damage to tomato plants.For weaker tomato,it needs to be lined.(5)The developed pollination UAV has better hover,pitch,roll and yaw flight capabilities.When the UAV flies between the rows of cultivation tanks in the greenhouse,the tomato on both sides of the UAV flight direction can be pollinated by wind induced vibration.UAV deflector plays an important role in pollination in greenhouse.The downwash flow field of the UAV was not enough for effective wind-induced vibration pollination of tomato flowers when the UAV flew between greenhouse rows without deflector.In addition,the hovering height of the UAV was at the same level with the tomato plants,and the tomato plants from the top to the middle region were obviously affected by wind.The wind speed on the side close to the UAV could reach 5-6 m/s,which could effectively pollinate two tomato plants on both sides by wind-induced vibration.UAV pollination can significantly improve the fruit setting rate and reduce the malformed fruit rate of greenhouse tomato plants.Tomato plants that were pollinated by drones produced about 30%more fruit than those that were pollinated naturally.UAV pollination has the characteristics of low cost,good benefit,high efficiency and low labor intensity.