Design And Simulation Of Greenhouse Tomato Old Leaf Removal Device Based On The Effect Of Nutrient Solution Concentration And Number Of Remaining Fruits

China is currently the world’s largest consumer of tomatoes.The statistics in 2019 show that the per capita demand for tomatoes in China is 15kg,and the annual growth rate is 5%.In recent years,the tomato planting area in China has been hovering around 1.1 million hectares.Therefore,to meet the demand for greenhouse tomato in China,we can only rely on increasing per unit yield.In the process of tomato growth,good plant type structure can improve the population photosynthetic rate of greenhouse tomato,which is the premise of ensuring high yield of tomato.At present,the adjustment of tomato plant type structure mainly depends on removing old leaves and thinning fruits.Cultivating a good plant type by reasonably removing old leaves is of great significance to promote the high-quality production of greenhouse tomatoes.However,at present,the removal of old leaves of tomato in china is mostly completed manually,with high labor intensity and low pruning efficiency.Therefore,strengthening the research on the removal equipment of old leaves of greenhouse tomato is of great significance to improve the production efficiency of greenhouse tomato in China.Based on this,the main research contents of this paper are as follows:firstly,the effects of different concentrations of nutrient solution and different number of remaining fruits on the growth parameters and petiole mechanical properties of greenhouse tomato were studied.Taking tomato as the test material,barrel planting was adopted,and the cultivation substrate was perlite.Three nutrient solutions with different concentrations were set to treat N₁（1.5 times the standard concentration nutrient solution）,N₂（1 times the standard concentration nutrient solution）and N₃（0.5 times the standard concentration nutrient solution）.Tomato Seedlings were watered with the corresponding nutrient solution after transplanting and colonization.When the tomato entered the fruiting stage,the tomato plants were treated with different number of remaining fruit,which were T₁（1 fruit per truss）,T₂（3 fruits per truss）and T₃（5 fruits per truss）.The effects of different treatments on plant height,stem diameter,leaf area,photosynthetic parameters and water potential of greenhouse tomato were studied;The dynamic changes of mechanical properties of tomato petiole under different treatment conditions were analyzed by shear and bending tests of tomato petiole with texture analyzer;The effects of different treatments on the components and internal structure of petiole and the corresponding relationship between the internal structure and components of petiole and mechanical properties were analyzed;The working parameters of the old leaf removal device are determined.Based on this,the old leaf pruning device suitable for greenhouse tomato is designed and simulated.The specific research results are as follows:1.Effects of different treatments on the growth and development of greenhouse tomatoIn the flowering and fruiting stage,appropriately increasing the concentration of nutrient solution is conducive to promote the growth of tomato.However,too high nutrient solution concentration can not significantly promote the whole growth cycle of tomato.The number of fruits retained significantly affected the growth of greenhouse tomato.With the increase of the number of fruits retained,the growth rate of stem diameter,plant height and leaf area of greenhouse tomato slowed down;Too much remaining fruit will significantly reduce the weight of single fruit（P<0.05）.The average quality of a single fruit when there were 5 fruits per panicle was reduced by 23.6%and 16.5%,respectively,compared with that when there were 1 fruit per panicle and 3 fruits per panicle,respectively.Comprehensive comparison,N1T3 group,that is,when 1.5 times the concentration of nutrient solution leaves 5 fruits per panicle,the total yield per plant is 3.46kg,which is the optimal combination.2.Effects of different treatments on mechanical parameters of tomato petiole in GreenhouseFrom the whole growth period,the elastic modulus,bending strength and shear strength of tomato petiole under each treatment are small at the seedling stage.From flowering to fruiting,the mechanical properties of petiole do not change significantly（P<0.05）.When entering the harvest stage,the elastic modulus,bending strength and shear strength of petiole will increase significantly.Different treatments significantly affected the mechanical parameters of tomato petiole in greenhouse.At seedling stage,different nutrient solution concentrations had little effect on the elastic modulus,flexural strength and shear strength of petioles.After entering the flowering period,the elastic modulus,flexural strength and shear strength of tomato petioles treated with N₃were significantly greater than those of N₁and N₂.The mechanical properties of petioles will be significantly reduced if the number of fruits is too large.At the same time,the shear tests were carried out at different positions of the petiole.The results showed that the shear strength at 6～10cm from the end was 14.1%lower than that at 2～6cm.3.Effects of different treatments on the anatomical structure of tomato petiole in greenhouseUnder the treatment of low concentration nutrient solution,the cortex stem diameter ratio and vascular bundle stem diameter ratio of petiole were significantly larger（P<0.05）,and the pith stem diameter ratio was significantly lower.The ratio of epidermis to stem diameter of petiole decreased significantly when the number of fruits remained was too much.At the same time,the correlation between the cross-section structure of petiole and its mechanical properties was analyzed.The results showed that the epidermal stem diameter ratio,cortical stem diameter ratio and vascular bundle stem diameter ratio of tomato petiole cross-section had a significant positive correlation with the elastic modulus,bending strength and shear strength of petiole;There was a significant negative correlation between the ratio of pith to stem diameter and the mechanical properties of petiole.4.Design and experimental simulation of old leaf pruning device of greenhouse tomato.Based on the previous research,an old leaf pruning device for greenhouse tomato was designed.The device is composed of lifting system,pruning system and control system.The combination of double lead screw stepping motor is used to realize the movement in both horizontal and vertical directions.The designed annular pruning device can meet the pruning requirements of old tomato leaves;At the same time,the cutting process of tomato petiole was simulated by using discrete element method and EDEM simulation software to test the cutting performance of the pruning device;Fuzzy PID is used to establish the control system.The rationality and feasibility of the control system are verified by simulation,so as to ensure that the device can achieve the predetermined goal of the design,so as to improve the plant type management level of greenhouse tomato,which has important practical value and social significance for further improving the production efficiency of greenhouse tomato and promoting the development process of greenhouse crop mechanization in China.