| China has the most cultivated area and yield of welsh onion in the world.In addition,China is the world’s largest vegetable exporter and the exports of welsh onion,ginger and garlic account for 25% of the whole vegetable exports.In process of welsh onion harvest consumes the most labor and the quality of harvest affects the final quality of welsh onion directly.This makes harvest critical to operation and industrial development of welsh onion,however the level of harvest is considerably low.At present,the harvest of welsh onion in China is done mostly by hand and backward equipment restricts the popularization of mechanization and the development of industry.In this paper,current status of welsh onion harvester in domestic and foreign was introduced firstly.Then according to the procedure of equipment design double-row self-propelled welsh onion combine harvester was developed on the basis of planting technology and operation requirement in China.Furthermore,filed test,theoretical analysis and optimization design aiming at key parameters,key process and key components were carried out,which make the machine practical and reliable.The main contents and results in the research are explained as follows.1.Physical properties of welsh onion and soil were obtained by flied investigation and data analysis.Parameters of geometrical properties of ridge are row spacing,height of ridge,width of bottom ridge,angle of ridge,plant spacing and deviation stem relative to ridge center axis.Parameters of physical properties of soil are soil strength,soil water content and soil bulk density.Parameters of physical properties of welsh onion are height of plant,length of stem,depth of fibril,diameter of stem in air,diameter of stem in ridge,range of leaf in nature and mass of plant.The key parameters above provide reliable data support for machine design.2.To explore a new means which uprooting plays a major role in harvest,mechanical model of welsh onion during uprooting was built on the basis of mechanism of plant ecological slope protection for considerable resistance of long stem harvest and results of model demonstrated that resistance form fibrils accounts for a large part of that force.Then feasibility of model was verified and results demonstrated that the deviation theoretical value relative to trial value of uprooting force fluctuates between 1.37% and 31.54% but most of them is less than 20%.Furthermore,factors of uprooting force were analyzed and regression model of uprooting force was created with application of SPSS software.According to importance,factors are arranged as follows: the number of fibrils,depth of fibril,diameter of stem in ridge and mass of plant.The mechanical model of uprooting can be held up as example for uprooting theory and the analysis of reason for uprooting resistance can be applied to design for reducing resistance.3.With analysis of technical requirements and process of harvest functional modules of harvester were designed,which include chassis,engine,hydraulic system,control system,digging device,pulling device,conveying device,soil removing device,tilting device and collection device.Then on the basis of the mechanical model of two-sided wedge,the digging resistance and the model of engine were determined.The transmission route was divided into two parts according to actuators and the transmission ratios of the steering system including belt wheel,transfer box,transmission box,main reducer and differential were determined.Finally,the structural design of harvester was completed by using modern design methods based on work above.4.The research on digging device,conveying device and hydraulic system were done in terms of influence on machine performance.The structure of digging shovel was designed and then statics analysis of digging device was conducted by finite element software and optimization design was carried out on basis of the results of analysis.The device after optimization not only meets requirements of mechanical property but also reduces slightly in mass.To meet requirement of vertical uprooting,the velocity of the clamping strip was obtained with kinematics analysis of the clamping strip.On the basis of relationship between initial grabbing angle and parameters of the clamping belt wheel,the diameter and the clearance of the clamping belt wheel were determined for grabbing welsh onion effectively.The ideal model of digging and pulling process was built for effective cooperation of digging and pulling and the spatial position of the grabbing device was determined.According to the motion of actuators,the hydraulic system and control circuit of machine were designed.A new floating hydraulic system to meet requirement of digging shovel was developed,which not only cures the defects of the traditional distributor but also can be used to floating process of agricultural implements in changing conditions. |
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