| Astragalus membranaceus picking operation is one of the important links in the process of Astragalus membranaceus harvesting.Traditional Astragalus membranaceus picking operation mainly uses manual picking,which has low work efficiency and high cost,and greatly wastes human,material,and financial resources.The implementation of mechanization of Huangqi picking operation can significantly improve the efficiency of Huangqi picking operation,increase the benefits of Huangqi planting industry,and is of great significance for the development of Huangqi planting industry.In order to improve the efficiency of astragalus membranaceus picking operation and solve the outstanding problems in the mechanized harvesting process of astragalus membranaceus industry,based on the research of rhizome crops picking and harvesting machinery,this thesis designed a kind of picking machine for astragalus membranaceus and other rhizome Chinese medicinal materials,and carried out statics analysis on the key structure of the astragalus membranaceus picking machine,and carried out theoretical analysis and discrete element simulation test on the movement process of the astragalus membranaceus picking machine,Completed the optimization of working parameters for the Huangqi picking machine.The research results can provide a theoretical basis and technical basis for the development of Huangqi picking machines.The main research conclusions are as follows:（1）On the basis of investigating and studying the requirements for the Huangqi picking operation,the overall structural design of the Huangqi picking machine was completed.Solidworks 3D modeling software was used to model the transmission device,excavation device,lifting rod chain device,Huangqi picking drum device,and horizontal conveying device of the Huangqi picking machine,forming the assembly of the entire Huangqi picking machine.（2）Using ANSYS finite element analysis software to conduct modal analysis on the Astragalus membranaceus pickup machine,the results show that the vibration types of the Astragalus membranaceus pickup machine frame structure are mainly divided into local vibration on the frame and overall vibration of the frame,and their deformation forms are mainly bending deformation and torsional deformation.The vibration frequencies of the first 7 steps of the frame are 12.79Hz,22.27Hz,22.37Hz,28.61Hz,29.36Hz,39.29Hz,and43.94Hz,respectively.The excitation frequency of the matching tractor under normal operating conditions is much higher than the natural frequency of the first 7 steps of the frame.The operation process of the Astragalus membranaceus pickup machine can effectively avoid resonance damage between the matching tractor.The results of statics analysis on the digging shovel and frame of the Astragalus pickup show that the maximum deformation of the digging shovel is located at the blade end of the middle shovel under normal working conditions,the maximum deformation is 1.37mm,and the maximum equivalent stress is located at the welding point between the digging shovel and the side plate,the size is 7.7851×10-4Pa.The maximum deformation position of the rack under normal working conditions is located at the top of the three-point suspension device,with a maximum deformation of 1.00mm.The maximum equivalent stress is located at the welding point between the three-point suspension device and the crossbeam,with a size of2.0423×10-4Pa.The maximum equivalent stress between the excavation shovel and the frame is much smaller than the allowable stress of the structural steel,and the design of key components of the Huangqi pickup machine meets the structural strength requirements.（3）The basic physical parameters（overall dimension,density,Poisson’s ratio,elastic modulus and shear modulus）and contact parameters（static friction coefficient,rolling friction coefficient and collision coefficient of restitution）of Astragalus were measured by physical test methods;The simulation test parameters were selected by referring to the physical test measurement results,and Plackett Burman simulation test was carried out by using the EDEM software.The simulation parameters affecting the angle of repose were significantly screened.The test results showed that the significant parameters were the coefficient of restitution of astragalus–stragalus collision,the coefficient of restitution of astragalus–steel collision,and the static friction coefficient of astragalus–steel collision.The steepest climbing test was used to determine the optimal value range of the significant parameters.Finally,the Box Behnken simulation test was used to obtain the optimal combination of simulation parameters of Astragalus membranaceus:the coefficient of restitution of Astragalus membranaceus–Astragalus membranaceus collision was 0.32,the coefficient of restitution of Astragalus membranaceus–steel collision was 0.36,and the static friction coefficient of Astragalus membranaceus–steel was 0.22.The values of other non significant parameters were the average values of physical test results.The validation test results show that the relative error between the average value of the Huangqi angle of rest in the simulation test of 35.65°and the Huangqi angle of rest measured in the physical test of 35.79°is 0.392%.There is no significant difference between the simulation test results and the physical test results.The optimal combination of simulation parameters can be used for discrete element simulation analysis of the factors affecting the performance of the Huangqi pickup machine.（4）In order to obtain the optimal working parameter combination of the Astragalus membranaceus pickup machine,discrete element simulation experiments were conducted on the working process of the Astragalus membranaceus pickup machine.A single factor and orthogonal experimental study was conducted using the linear speed of the lifting rod chain,the drum picking device,and the spacing between the spring teeth as experimental factors,and the picking rate of the Astragalus membranaceus pickup machine and the collision force suffered by the Astragalus membranaceus during the picking process as evaluation indicators.The influence of the working parameters of the pickup machine on the picking rate of Astragalus membranaceus and the collision force suffered during the picking process were clarified.Multi objective optimization was conducted based on the picking rate of Astragalus membranaceus and the collision force during the picking process.The optimal working parameters of the Astragalus membranaceus picking machine were obtained as follows:the linear speed of the lifting rod chain was 1.4m/s,the speed of the Astragalus membranaceus picking drum was 110r/min,and the spacing between the spring teeth was 40mm.（5）Based on the optimal working parameter combination obtained from the performance simulation test of the Astragalus membranaceus pickup machine,a physical verification test was conducted using the Astragalus membranaceus pickup machine test platform and the Tekscan pressure distribution measurement system.The test results showed that when the linear speed of the lifting chain was 1.4m/s,the speed of the pickup drum was 110r/min,and the spacing between the spring teeth was 40mm,the average Astragalus membranaceus pickup rate was 94.4%,and the collision force on Astragalus membranaceus was 1.75N,Under the same working parameters in the simulation experiment,the picking rate of Astragalus membranaceus was 95%,and the collision force on Astragalus membranaceus was 1.64N.The relative errors between the picking rate and collision force in the simulation and physical experiments were 0.6%and 6.2%,respectively.The results of the simulation and physical experiments were consistent,fully demonstrating the reliability of the experimental data.Furthermore,it was observed that there was no obvious damage to the skin of the picked Astragalus membranaceus,meeting the agronomic requirements of Astragalus membranaceus picking operation. |
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