Simulation Study On Multi-station And Low-damage Harvesting System Used For Apples

The orchard multi-station harvesting system is mainly used in modern dwarf rootstock and dense planting apple orchards to assist pickers to complete the automatic collecting-conveying and packing works of apples.Aiming at the key problems of high collision risk and large damage of apples during the transportation of apples in the harvesting system,it is necessary to study the mechanism of multi-station picking,multi-stage conveying and automatic boxing of apples,and to solve the dynamic parameters of low-damage harvesting of apples.By analyzing the research status of orchard harvesting machinery at home and abroad and investigating the cultivation characteristics of modern dwarf rootstock and dense planting apple orchards,based on the principles of ergonomics and the fruit collision damage mechanism,The digital prototype of the "two sides,three heights,six stations"harvesting system is established by using software Inventor.Finite element analysis on the supporting channel steel of the main conveying device and the bearing tray and the U-shaped support frames of the fruit box bearing-rotating device is carried out to ensure that its strength meets the requirements of the work.The test bench of prototype system is built to provide a basis for benchmarking and verification of simulation tests.By the bench test of subordinate-main conveying system,it is known that there is no discoloration on the surface of apples when the belt speed of the sub-conveying belt is less than or equal to 0.060 m/s.The dynamic simulation model of the sub-main conveying system is built by using software ADAMS.The results of simulation test show that the collision force between apples is the largest when the apple is placed sideways on the conveying belt,and the apple is in a non-damaged conveying state when the belt speed of the conveying belts at low,medium and high stations are 0.018～0.040 m/s,0.018～0.040 m/s and 0.018～0.035 m/s,respectively.The bench test of the sub-main conveying system is conducted under this condition,and the result shows that there is no collision damage to the apple,and the maximum delivery volume of apple is 19200 per hour.The key structural parameters to transfer apples from the main conveying belt to the vertical conveying belt smoothly are determined.The dynamic simulation model of the main-vertical conveying system is built by using software EDEM.Results of orthogonal test of three factors and five levels show that the average packing damage rate of apples increases with the increase of the factors lifting speed of vertical conveying device,rotating speed of fruit box rotating device,and angle of guide plate.The results of the range analysis of the simulation results that the primary and secondary order of the significance of the three factors on the damage rate of apples is angle of guide plate>rotating speed of fruit box rotating device>lifting speed of vertical conveying device,and the proportions are 44.74%,34.79%,20.47%,respectively.The results of variance analysis of packing damage rate show that the lifting speed of the vertical conveying device and the rotating speed of the fruit box rotating device have a extremly significant effect on the packing damage rate of apples,and the angle of the guide plate has a significant effect on the packing damage rate of apples.The better values of the three factors are 0.0015 m/s,6 r/min.and 12°,respectively.Under this condition,the layered stacking effect of apple packing is better,and the collision damage rate during packing is 4.34%.With this parameter combination,the bench test of the rotating packing system is carried out.The results showed that the damage rate of apples under this condition is 3.66%,and the layer-by-layer stacking effect of apple packing is basically consistent with the simulation test.