Design and experiment of potato metering device with double-deck seed tank

Abstract: Potato is the fourth staple food product in China, and Chinese potato planting area of 6.7 million hm2 ranks first worldwide in 2013. However, the mechanized potato seeding percentage in China is only 23%, which is limited by poor performance of potato planter. Cup-chain metering device is the most commonly used for potato planting, whereas it is troubled with high miss-seeding and re-seeding problems. To solve these problems, the simulation model of potato planter is firstly built, and this model is used to analyze potato seed movement during metering process; then a new type of metering device with double-deck seed tank is designed, and finally the parameters of seeding speed, seed cup diameter and seed filling height are optimized. 1) Potato planter simulation: Potato cup-chain metering planter is simulated based on the software of EDEM (enhanced discrete element method). On the one hand, Hertz-Mindlin non-sliding contact model between 2 seeds is built with the recovery coefficient of 0.3, static friction coefficient of 0.56 and dynamic friction coefficient of 0.15; on the other hand, the model between seed and seeder is built with the recovery coefficient of 0.52, static friction coefficient of 0.5 and dynamic friction coefficient of 0.1. 2) Potato seed movement analysis: During the metering process, movement is originated from only a small part of seeds instead of most of them that are immobile. The small part of moving seeds determine the seed charging performance. The major movement area of potato seed is around the chain presenting the shape of inverted cone, which contains 3 areas of high-efficiency charging area, low-efficiency charging area and no seed area. The seed charging performance is directly affected by the volume of high-efficiency charging area and the seed mobility. 3) Seed planter design: Aiming to enlarge high-efficiency charging area and enhance seed mobility, planter with double-deck seed tank is designed, which doubles the volume of high-efficiency charging area and enhance seed mobility. A planter test platform with double-deck seed tank is modified from a 1 220 type potato planter provided by Zhongji Meno Polytron Technology. 4) Performance evaluation and parameter optimization: 2 indicators are employed to evaluate the planter performance, including miss-seeding percentage and re-seeding percentage. The influence of seeding speed, seed cup diameter and seed filling height in the seed tank on seed charging performance is studied. Regression equation and multi-objective optimization method are employed for parameter optimization. In the Chinese national standard for potato planter, miss-seeding percentage is no more than 10% and re-seeding percentage is no more than 20%, the designed planter can operate at the seeding speed of 0.96 m/s to satisfy this national standard. To balance the planting performance, including miss-seeding percentage and re-seeding percentage, and planting efficiency of seeding speed, the parameters of seeding speed, seed cup diameter and seed filling height in the seed tank are optimized as 0.67 m/s, 48.6 mm and 0.28 m, respectively, showing the miss-seeding percentage of 3.8% and re-seeding percentage of 8.8%. This paper demonstrates the potential for a high-performance cup-chain metering device with double-deck seed tank for potato planting.