Equipment And Key Technologies Of Automatic And Precision Trimming For Postharvest Cabbage

Cabbage(Brassica oleracea L.var.capitata L.)is widely planted in China,because of its rich nutritional value,high yield and storage resistance.Commercial treatment can effectively improve the quality and economic added value of postharvest cabbage,that has turned into the trend of industry development.However,at present,the feeding,sorting directionally,root-cutting and other trimming processes for postharvest cabbage are mainly manual,with low production efficiency,high labor intensity and high production cost.Hence in response of the above situations,this paper carried out the research on the equipment and key technologies of automatic and precision trimming for postharvest cabbage,from the overall scheme,root-cutting characteristics,automatic orientation method,precision root-cutting method and performance test of the prototype.It provides the theoretical basis and foundation for research and development of multi-channel and high-throughput commercial treatment equipment for postharvest cabbage,such as grading,detection and packaging.The principal contents and conclusions are as follows:(1)Aiming at the problems of low efficiency and high labor intensity of postharvest cabbage artificial trimming,a coherently automatic and precision trimming method for postharvest cabbage high-throughput commercial treatment was proposed.Relying on Taibai vegetable experimental demonstration station,the agronomy and market demand of postharvest cabbage were investigated and analyzed,and the necessity and urgency of postharvest cabbage trimming were further determined.The physical parameters of "Zhonggan 15" cabbage were measured and counted.The automatic and precision trimming method of "unloading— buffer— monomer sorting— orientation— root-cutting" was proposed,combined with the manual trimming process of postharvest cabbage.And the main functions and performance indexes of the automatic and precision trimming equipment for postharvest cabbage were determined,so as to provide performance basis for subsequent key technology research.(2)In order to find out the influence law of mechanized trimming for postharvest cabbage on the root-cutting characteristics,and determine the best root-cutting area,a root-cutting test platform for postharvest cabbage based on the universal testing machine was designed,and the comparative test and orthogonal test of root-cutting were carried out.The morphological characteristics of root tissue were obtained by scanning electron microscope,and its cutting characteristics were further explained.The results illustrated that the root-cutting curve showed double peaks,and the peak appeared at the place with the largest circumscribed area of the cambium with small and dense cells.The optimal parameter of cutter thickness,shear position,shear speed and sliding-cutting angle was respectively 0.89 mm,0 mm to 3 mm,388.94 mm/min and 34.84°,and the shear stress under this condition was 28.02 k Pa.Above results provided a theoretical basis for the structural design and parameter optimization of automatic and precision trimming equipment for postharvest cabbage.(3)In view of the orientation difficulty for postharvest cabbage caused by random and disordered initial pose,combined with the characteristics of uniaxial symmetric ellipsoid,an automatic orientation method of postharvest cabbage based on moment of inertia was proposed.According to the physical parameters of postharvest cabbage,the mathematical model was established,and the moment of inertia of its inertia axis and orientation motion stability were analyzed.By ADAMS software,the variation of orientation movement such as the displacement difference of postharvest cabbage and the included angle between the central axis of postharvest cabbage and the axis of roller were simulated and analyzed.And the automatic orientation test platform of postharvest cabbage was built and the verification test was carried out.The results showed that the postharvest cabbage gradually rotated around the only central axis with the smallest moment of inertia,and the movement was dynamic and stable.Under the condition of orientation simulation parameters,the average included angle of postharvest cabbage was 8.94°,the time required for orientation was 2.63 s to 9.27 s,and the success rate of orientation was 92%,which provided a theoretical basis for the subsequent automatic orientation parameter optimization and precision trimming.(4)For further exploring the automatic orientation mechanism of postharvest cabbage and improving orientation effect,the single factor test and orthogonal test for orientation were carried out,based on the automatic orientation test platform for postharvest cabbage,and the key operation parameters affecting the orientation effect were determined and analyzed.The structure optimization of orientation roller was carried out based on the characteristics of conical tread,and the progressiveness of this structure was explored through dynamic analysis and ADAMS motion simulation analysis.And the prototype of conical orientation conveyor for postharvest cabbage was trial produced,and the optimization test of conical orientation was carried out.The test results showed that the optimal parameter of taper angle of conical orientation roller,axial clearance,and linear speed of conveying chain was respectively 20°,60 mm,and 300 mm/s.Under this operation condition,the average orientation success rate of postharvest cabbage was98.67%,and the average included angle was 5.18°,which further improved the orientation performance of postharvest cabbage,and provided favorable conditions and technical support for the precision trimming of postharvest cabbage.(5)According to the operational requirement of postharvest cabbage,sunch as short root trimmed and high trimming accuracy,a method to determine the root-cutting position based on the geometric characteristics of postharvest cabbage was proposed,and an automatic and precision root-cutting device of postharvest cabbage was designed based on the conical orientation device.The impact force for root-cutting of postharvest cabbage was theoretically analyzed,the automatic and precision root-cutting platform of postharvest cabbage was built,and the parameter optimization test of impact force for root-cutting was carried out.The test results showed that the optimal parameter of adjust module speed,cutter speed and cutter height was respectively 250 r/min,200 r/min and 110 mm.Under the operation parameters,the root-cutting plane was relatively flat,and the average value of the maximum impact force for root-cutting was 15.95 N,which provided theoretical basis and data reference for the prototype performance test of automatic and precision trimming equipment for postharvest cabbage.(6)Prototype trial production and performance test of automatic and precision trimming equipment for postharvest cabbage.According to the previous research results of the key technologies of automatic and precision trimming for postharvest cabbage,the automatic and precision trimming equipment for postharvest cabbage was integrated and trial produced,and the trimming performance test was carried out.The test results showed that the optimal parameter of run velocity of unloading cylinder,speed of single layer feeding roller,speed of variable pitch conveying roller,linear velocity of chain,speed of cutter and height of overlying conveyor belt was respectively 10 mm/s,50 r/min,30 r/min,300 mm/s,200 r/min and 142 mm.Under this optimal parameter combination,the monomer sorting success rate was 97.78%,the orientation success rate was 93.33%,the root-cutting pass rate was 87.78%,and the single channel operation efficiency was greater than 1550 cabbages per hour,which basically met the performance indexes of automatic and precision trimming equipment for postharvest cabbage.