Analysis and test of linear seeding process of maize high speed precision metering device with air suction

Abstract: In order to solve the problems that the seed and seed tube collision may reduce the qualified seeding rate and increase the coefficient of variation during the seeding process of the air suction precision maize seed metering device at high working speed, a method of seed throwing in a straight line by using linear seeds pushing device and suction hole of seed plate was presented in this paper. The linear seeds throwing process included three stages. Firstly, seeds attached to the seed plate steadily move in a circle with the seed plate during the range of transition area. Secondly, the seeds moved straight down at an absolute velocity with the seeds linear pushing device during the range of linear pushing area. Finally, seeds entered into the range of linear falling area and accelerated straight down, and then entered the seed tube, the seeds in the seed tube evenly and orderly dropped into the seed ditch. The principle of seed falling in a straight line was analyzed, the motion and mechanical relationships between the seeds and the air suction precision maize seed metering device during the seeds linear falling process were explained, the curve equation of suction hole of seed plate was defined, the structural curve equation of the seed pushing device was determined. In order to explore the effects of seed feeding position and working speed on the seed metering performance of seed metering device, the whole factor test was carried out with the seed feeding position and working speed as the influencing factors, and with the qualified rate of seeding spacing, the missing seeding rate and the coefficient of variation of seeding spacing as the test indexes. In addition, the significance of the test results was analyzed, and the regression equations of each factor and test indexes were determined. The maize seeds of Zhengdan 958 were used as objects of indoor bench test. The results showed that the optimal seed feeding position was that the angle of the linear seed pushing area was 15°and the angle of linear seed falling area was 21°. The verification test results showed that the qualified seeding spacing rate was 98.68%, the missing seeding rate was 0.69%, and the coefficient of variation of seeding spacing was 15.03% at the working speed of 12 km/h, which was consistent with the theoretical optimization results. The comparison tests were conducted between the linear seeding and the ordinary choke seeding. The results showed that all the indexes improved at all working speed on the basis of meeting the national standard requirements. With the working speed increased, the improvement effect became better. At the working speed of 14 km/h, compared with the ordinary choke seeding, the qualified rate of seeding spacing was increased by 4.22 percentage points, the missing seeding rate was reduced by 4.20 percentage points, and the coefficient of variation of seeding spacing was reduced by 4.55 percentage points, which indicated that the linear seeding could effectively improve the seeding effects at high working speed The results of adaptability tests showed that the seeding performance of Xianyu 335, Denghai 605 and Jingnongke 728 was lower than that of Zhengdan 958, but the qualified rate of seeding spacing was higher than 96.5%, the missing seeding rate was lower than 1.8%, and the coefficient of variation of seeding spacing was lower than 17.7%, which still met the requirements of the precision sowing.