Research On Virtual Prototype Of Pneumatic Drum Seed Metering Device Based On Seed Characteristics

Precision seeding in plug trays can not only reduce the amount of seeds,but also provide high-quality seedlings for subsequent transplanting,reduce labor costs and improve economic benefits.Precise seed picking and precise seeding of the pneumatic drum seed metering device are the key technologies for precision seeding in plug trays.However,the requirements of working parameters during the seeding process are various due to the different characteristics of seeds,such as the size,weight,shape and so on,which make the design of the seed metering device difficult.To address this problem,a virtual prototype study of the seed metering device was conducted based on the sowing principle of the pneumatic drum seed metering device and the characteristics of specialshaped seeds in this paper.The main research contents are as follows:(1)The principle of the pneumatic drum seed metering device was described,and the key components of the seed metering device such as the seeding drum,suction holes,and positive and negative pressure air intake discs were designed.According to the force analysis of the seed adsorption process,the key factors affecting the adsorption characteristics of the device were the diameter of the suction hole,the negative pressure of the device,and the rotation speed of the device which were used to establish a simplified model of the flow field of the seed meter.(2)Based on the flow field model of the seed metering device,the secondary development technology of the software was used to realize the parametric modeling function of the flow field of the virtual prototype simulation platform with the key factors:the diameter of the suction hole,the diameter of the drum,and the inclination of the seed box,etc.The parametric simulation function of the flow field of the virtual prototype simulation platform was realized by taking the working negative pressure and device speed as the boundary conditions.According to the geometric characteristics of the special-shaped seeds,the long axis,the short axis and the length of the seed characteristic section were selected as the key parameters to realize the boundary output function of the special-shaped seeds on the virtual prototype simulation platform.(3)Two types of typical special-shaped seeds: pepper and radish were taken as the research objects,the physical parameters such as the 1000-grain weight and density of the seeds were measured,and the discrete element model of the seeds was established through the simulation platform.The internal flow field distribution of straight,conical and trumpet-shaped suction holes is analyzed respectively.And the results showed that the flow field distribution of the straight-shaped suction hole was the most uniform,the adsorption performance of the conical suction hole was the best,and the trumpet-shaped suction hole was not suitable for the pneumatic drum seed metering device.The analysis of the adsorption process of seeds was completed in the virtual prototype.The results showed that the adsorption effect of pepper was the best when the diameter of the suction hole is 0.7 mm,the seeding speed is 420 discs/hour,and the working negative pressure was 10 k Pa.And the adsorption effect of radish seeds was the best when the diameter of the suction hole was 0.7 mm,the sowing speed was 500 trays/hour,and the working negative pressure was 14 k Pa.(4)A seeding experiment bench with replaceable seeding drums was developed.The pepper and radish seed were taken as the test objects,and the three-factor and three-level response surface tests of suction hole diameter,working negative pressure and drum rotation speed were carried out respectively.The regression model between the qualified index,reseeding index,miss seeding index and three factors of the pneumatic drum seed metering device were obtained according to the above experiments.Through optimizing the model and validating seeding experiments,the results showed that the qualified index of pepper seeds was 82.81%,and the qualified index of radish seeds was 87.50% under the predicted conditions.