Abstract:Under the narrow-row-dense planting mode of beans, it is difficult to achieve high-speed precision seeding. However, a pneumatic precision seed-metering device with single seed-metering plate for double-row was developed, which used single-channel and single-row seeding tray to realize double-row seeding operation. The basic structure and working principle were expounded. The working area of the seeding device was divided, the structural form of the seeding tray was determined, the key parameters of the main structure were analyzed and the mathematical model was determined. The experiment was employed through the method of Box-Behnken orthogonal rotating center combination of three factors and three levels according to the GB 6973—2005 national standard. In test, soybean seed Zhonghuang 37 was selected as experimental material. Combining with extensive pre-experiment and theoretical analysis, hole diameter, vacuum degree, forward speed were taken as main influencing factors, the seed qualified index and missing index were taken as response index. The results showed that the order of contribution rates on the effect of inner qualified index was the vacuum degree, hole diameter and forward speed, the order of contribution rates on the effect of inner missing rate was vacuum degree, forward speed and hole diameter, the order of contribution rates on the effect of outer eligible rate was vacuum degree，forward speed and hole diameter, the order of contribution rates on the effect of outer qualified index was hole diameter，vacuum degree and forward speed. The optimal combination of parameters was as follows: the hole diameter was 4.5mm, the vacuum degree was 4.5kPa, the working speed was 10km/h, and under the optimal combinations, the inner eligible rate was 97.83%, the inner missing index was 0.62%, the outer eligible rate was 98.24%, the outer missing rate was 0.47%. The verification test was repeated 10 times, the results indicated that the actual test results were in agreement with the optimization results. Then, a speed single factor test was carried out. The results showed that the inner and outer eligible rate were more than 93%, the inner and outer missing rate were not more than 5%, and the inner and outer multiple rate were not more than 2%. At last, the adaptation tests of peas, mung beans and adzuki beans were carried out. The results showed that the inner and outer circle eligible rate were more than 97%, the inner and outer missing rate were not more than 1%, and the inner and outer multiple rate were not more than 3%. The results of the research laid a foundation for the development of pneumatic precision seed-metering device for bean, and provided a reference for the research of bean narrow-row and flat-dense planter.
