Design and experiment on spiral-tube reseeding device for loss sowing of rapeseed

Abstract: Loss sowing phenomenon is inevitable for rapeseed pneumatic precision metering device. For the small size and light quality, it is not easy to observe the metering process; when rapeseed emerges, carrying out artificial reseeding or transplanting is both labor-intensive and adversely affecting the farming season. It will increase the complexity of structures, increase costs, and slow down reseeding response by using pneumatic precise metering device to reseed. In order to solve this problem, a new kind of structure of spiral-tube reseeding device for rapeseed was presented. The working principle, main structure and performance parameters of spiral-tube reseeding device were analyzed. This spiral-tube reseeding device was able to complete these operations such as seed filling, protecting, taking and releasing automatically with the help of the liquidity of rapeseed and gravity. It took a short trip and less time. By using the discrete element method software EDEM（discrete element method）, experiments were taken to analyze the relationships between seeding quantity and rotation speed of spiral-tube reseeding device. Meanwhile, tests were also carried out for spiral-tube reseeding device which was manufactured by using three-dimensional (3D) printer. The test indicated that when the rotation speed of seven-spiral-tube reseeding device was 25-180 r/min, the linear correlation coefficient between seeding quantity and rotation speed was 0.99. The equivalent seeding quantity of each hole was 1.7-1.9 grains. Its stability variation coefficient was no more than 6% and the seeding damage rate was less than 0.5%. There was no hole blocked. It was quick and easy to reseed by taking this spiral-tube metering device for reseeding. Combined the characteristic of seeding quantity for spiral-tube reseeding device with loss sowing detection in real time by time-varying window, the relationship model between reseeding rotation speed of spiral-tube reseeding device and loss sowing coefficient was established. This achieved a variable reseeding in the current time window. Tests were carried out on the JPS-12 testbed of the pneumatic rapeseed precision metering device. During the test, 10 holes were detected as one time window by using forty-hole rapeseed precision metering device. Spiral-tube reseeding device lagged behind rapeseed precision metering device by 500 mm. The theoretical loss sowing coefficient of rapeseed precision metering device was set as 0, 0.3, 0.5, 0.7 and 1.0, and the tested were taken out respectively at the different rotating speed of 15, 18, 21, 24, 27 and 30 r/min. According to the rotation speed of metering device, conveyor belt speed was set differently in order to ensure a fixed seeding spacing in the course of test. Loss sowing coefficient within a time window was got by the method based on time-varying window of loss sowing real-time detection. If the loss sowing coefficient was bigger than or equal to the loss sowing coefficient threshold, a stepper motor drove spiral-tube reseeding device to reseed variably in the current time window. The test on testbed showed that when the speed of pneumatic precision metering device was within 15-30 r/min at different loss sowing states, spiral-tube reseeding device could adjust its working speed to realize the required amount of loss sowing in the current time window automatically. Tests showed that reseeding times was equal to metering device's equivalent loss sowing quantity within the current time window. The rate of successful reseeding was 100%. And the filling seeds by spiral-tube reseeding device were uniformly distributed within the reseeding distance. The largest seeding spacing was less than 1.5 times theoretical metering seeding spacing after reseeding. The loss sowing index of seed spacing after reseeding was zero, namely no loss sowing phenomenon after reseeding. The device proposed in this study can reseed effectively for small seed precision metering such as rapeseed to remove loss sowing and improve the quality of sowing.