Parameter optimization and experiment of the disturbance pneumatic plate hole metering device for rapeseed

Pneumatic precision metering device has widely been used for the planting of rapeseed in recent years. However, it is very necessary to improve the performance of hole-sowing and metering for a higher operation speed of the device in modern mechanized agriculture. In this study, a dynamic analysis was conducted on the disturbance filling process of rapeseed, then to establish a disturbance filling mechanical model. Particularly, an attempt was made on the parameter optimization and experiment of disturbance air-suction hole metering device for rapeseed. The result showed that the filling performance depended mainly on the rotation speed and structure of the seed plate, as well as the working negative pressure. The disturbance tooth presented a disturbing and pushing effect on the population, leading to the increase initial speed of seed migration. As such, the population close to the surface of seed plate was obtained the same initial speed as the suction hole, thereby increasing the contact time between the seed and suction hole, finally making the seeds close to the seed plate easily captured by the suction holes. A simulation model with the EDEM software was also constructed for the motion contact between the rapeseed and seed plate. The different structures of seed plate were used to determine the influence of structural parameters on the disturbance intensity of population, particularly the number and thickness of groove teeth. More importantly, the population in the filling room was divided into the forced and the friction disturbance zone. Correspondingly, a better parameters combination of grooved teeth was achieved to clarify the influence of various factors on population disturbance. Among them, the number and thickness of groove teeth, as well as the rotation speed of seed plate were selected to be the test factors, while, the average speed of population in the forced disturbance zone was used as the test index during parameter optimization. A performance test of bench filling was conducted to verify the simulation. A four-factor three-level orthogonal test was also carried out with the number and thickness of groove teeth, the rotation speed of seed plate, and the working negative pressure as the test factors, whereas, the missing rate and the filling qualification rate as the evaluation index. Additionally, a range analysis was utilized to determine the optimal parameter combination of groove tooth. Specifically, the optimal parameter combination was achieved, where the number of groove tooth was 18, and the thickness of groove tooth was 1.0 mm, indicating better consistency with the simulated ones. The optimized seed plate was selected for a better filling performance of disturbed and undisturbed seed plates under a low negative pressure via the performance test of bench filling. A bench comparison test also clarified that the seed plate with directional disturbance to the population effectively improved the seed filling performance. A three-level factorial design experiment was carried out with the seed plate rotation speed and working negative pressure as the test factors, and the cavity rate and the qualified rate of the seed in the hill as the test indicators, where the optimized seed plate was installed on the disturbance air-suction hole metering device for rapeseed. The regression analysis showed that the cavity rate was lower than 3%, and the qualified rate of seed in the hill was higher than 96% when the seed plate rotation speed was 40-80 r/min, and the working negative pressure was 2 392-2 500 Pa. The verification test with the same conditions was basically consistent with the predicted one. Field experiments demonstrated that the rapeseed planting density was (70±4) plants/m2, the average of empty broadcast rate was 4.6%, the average of pass rate was 90.54%, suitable for the agronomic requirements of rapeseed. This finding can provide a sound reference for the design of pneumatic drill hole planting and metering system.