| Xinjiang is the main production area of high-quality jujubes in China.During the harvest period,it relies on manpower to hit the trunk of the jujube tree to shake down the red dates,collect the fallen jujubes into strips and then complete the harvest operation by hand.There are problems such as high operation costs,low efficiency and labor shortage in manual picking.The mechanized operation can significantly reduce the harvest cost,improve the operation efficiency and effectively alleviate the labor shortage during the harvest period in southern Xinjiang.However,the existing mechanical jujube harvesting structure is complex,the operation parameters need to be matched,the operation efficiency needs to be higher,and it is easy to be restricted by the soil.Therefore,this research has designed a picking-transporting and cleaning device for the landing of jujube after the artificial strip gathering in the south Xinjiang jujube garden.The main research contents are as follows:（1）Determination of characteristics and contact parameters of jujube orchard soil（sandy soil）and jujube basic materials during harvest.Use EDEM software to model the surface soil（sandy soil）particles of jujube garden,and use Design-Expert software to carry out the Central Composite Design test.Taking the actual angle of repose and sliding friction angle of sandy soil as the optimization objective,the optimal contact parameter combination is obtained as follows:sandy soil-sandy soil recovery coefficient 0.215,static friction coefficient 0.611,rolling friction coefficient 0.217,sand-steel recovery coefficient 0.375,static friction coefficient 0.328,rolling friction coefficient 0.125.Based on the measured contact parameters,the interaction contact law between comb teeth-soil is determined by virtual simulation.（2）Structural design of picking-conveying cleaning device.According to theoretical analysis and pre-experiment,the effective working width of the pickup device is 1100 mm;The comb teeth is a round steel with a diameter of 12 mm,its length is 1050 mm,and the comb teeth clearance is 18 mm;The distance between the installation position of the strip brush roller axis Z and the end of the comb teeth is 262 mm;The strip brush material is PVC material with elastic modulus of 3.14 GPa,and the strip brush plate is 150 mm long and 5 mm thick;Pickup speed ratioλIs 1.2～4.6,and the speed range of brush roller shaft is 45～65r·min-1;Installation angle of the conveying and separating deviceβis 24°,the included angle between the conveying rod group and the horizontal planeβ2 is 8°.（3）Determination of operation parameters of pickup device based on discrete element method.The discrete element simulation model of the floor-standing jujube pickup device-soil-jujube was established by using the EDEM software.Based on the basic law of the comb teeth-soil interaction,the free range of the comb teeth angle into the soil was determined to be 30°～33°according to the dynamic results.Taking the forward speed of comb teeth and the depth of comb teeth into the soil as the test factors,through the single-factor test of jujube picking rate and the amount of soil,the range of forward speed of comb teeth is determined to be 0.2～0.4 m/s,and the range of depth of comb teeth into the soil is 5～45 mm.（4）Performance verification of the floor-stranding jujube picking and conveying cleaning device.Taking the comb teeth forward speed,the speed of the brush roller shaft and the height of the profiling rod hole spacing as the test factors and taking the pickup rate,damage rate and impurity rate as the test indicators,the Box-Behnken method is used to design the three-factor three-level test.The test data are analyzed and processed by using Design-Expert software,and the optimal working parameter combination of the landing jujube picking-conveying cleaning device is determined.Finally,the forward comb teeth speed is 0.3 m/s,the speed of the brush roller shaft is 53 r·min-1,and the height of the profiling rod hole spacing is 60 mm.The verification test is carried out.The test results show that the optimized device has a jujube pickup rate of 92.11%,a damage rate of 2.07%,and an impurity rate of 4.15%.The relative error with the prediction model is not more than 8%.The model is reliable and meets the operational requirements. |
