| China is a big country for fruit production and consumption,and the planting area of fruit trees and fruit output rank first in the world.Apple is one of the dominant fruits in my country.In recent years,the planting area has gradually expanded and the output has increased steadily.Fertilization of apple trees is a key link in orchard management.The quality of fertilization directly impacts the nutrient absorption of fruit trees.Rational fertilization is an important measurement to ensure a high,stable,and increased yield of fruit trees.Orchard ditching-fertilizer machine could complete ditching,fertilizing,covering soil,and other processes at one time.Comparing with traditional manual ditching and fertilizing,it gets high efficiency,low cost,and good fertilizing effect.The performance of the ditching device,which is the main working part,directly impacts the quality of the ditching operation.The complex structure of orchard ditching fertilizer,the harsh working environment,and the diversified movement characteristics lead to many problems,such as the poor stability of ditching depth,poor consistency of ditch bottom width,and low soil coverage rate,which directly affect the quality of orchard ditching operation and the yield of fruit trees.At present,the researches on apple orchard ditching majorly focus on bionic ditcher,soil disturbance analysis,ditching power consumption,soil cutting speed,ditching device design,soil movement analysis,and so on.In this thesis,through the dynamic analysis of ditching device,combining with the agronomic requirements of orchard ditching and fertilization,a double-disc opener was designed;the structure of the rack was optimized by using a multi-objective genetic algorithm and response surface methodology;the soil ditching device separation has established the parameters of ditching depth,trench bottom width,soil particle number before and after ditching are measured by the discrete element model;the influence of ditching device parameters on the stability of trench depth,the consistency of trench bottom width and the coverage rate under the working condition of the whole machine was explored,and the experimental factors were comprehensively optimized.The improved and optimized device was verified by field experiment.The main research work and innovations are as follows:(1)A double plates ditching device is designed.Through the force analysis,motion analysis,and simulation analysis of the ditching parts,the motion parameter equation of the endpoint of the ditching blade is established,the factors affecting the ditching operation are analyzed,and the type of the ditching cutter and the rotary ditching method are determined.Combining with the agronomic requirements of orchard ditching fertilization,it is calculated that the transmission ratio of the ditching transmission box is 2.15,the number of the ditching cutter is 8 for each cutter head,and the number of the ditching cutters is evenly aligned along with the cutter head.The diameter of the cutter head is 320mm,and the rotating speed of the cutter is 230r/min.(2)By using the discrete element simulation method,the influence law and mechanism of various factors on orchard ditching performance are explored.The operation parameters optimization experiment of orchard ditching fertilizer is carried out to study the influence of operation parameters of ditching device on the stability of ditching depth,consistency of ditch bottom width,and the soil coverage rate.By using the Box Behnken experimental design method,the parameters of orchard ditching fertilizer operation are studied by taking forward speed,ditching knife rotation speed,and ditching knife deflection angle as experimental factors,ditching depth stability,ditch bottom width consistency,and soil coverage rate as experimental indexes.The regression model between experimental indexes and experimental factors is established,and the influence of various factors on experimental indexes is analyzed.The results show that the optimal operation parameters are as follows: the forward speed is 0.8 m/s,the rotating speed of the ditching cutter is 348 r / min,and the deflection angle of the ditching cutter is 32 degrees.At this time,the stability of the ditching depth is98.33%,the consistency of the ditch bottom width is 96.32%,and the soil coverage rate is81.53%.(3)Multi-objective genetic algorithm and response surface methodology are used to optimize the frame of orchard ditching fertilizer.The parametric model and finite element model of orchard ditching and fertilizing machine frames are established.The natural frequency and vibration mode of the frame are obtained through modal analysis,and the influence of the frame on the dynamic performance of the whole machine is studied.The firstorder modal frequency is set as the objective function.The sensitivity of the bar thickness to the first-order modal frequency is obtained through the sensitivity analysis of the frame,and the thickness of the high-sensitivity bar is set as the objective function The variation range of thickness is set as the constraint condition.According to the requirements of the lightweight design of modern agricultural machinery structure,the quality of the frame is also taken as the objective function.Based on the objective function,design variables,and constraint conditions,the mathematical model of multi-objective optimization of the frame is constructed.Based on the Hammersley sampling method,the experiment is designed and the corresponding response surface is fitted.Finally,the multi-objective genetic algorithm is used to optimize the frame structure.The optimization results show that the first-order modal frequency of the optimized orchard ditching and fertilizing machine frame is increased from35.39 Hz to 38.31 Hz,with an increase of 8.25%,and the input frequency is 35Hz,which is far away from the tractor;the mass is 389kg,which meets the requirement of minimum mass when the first-order modal frequency is increased.After optimization,the ditching consistency coefficient and fertilization stability coefficient of orchard ditching fertilizer operation is significantly improved,which meets the production requirements of the orchard ditching fertilization.(4)The results of the field experiment showed that the stability coefficient of ditching depth,the consistency coefficient of ditch bottom width,and the soil coverage rate were not less than 95.36%,96.27%,and 80.64% respectively.After the ditching operation,the ditching depth,ditch bottom width,and soil coverage rate of apple orchard ditching fertilizer meet the requirements of national standards. |
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