Design and experiment of a device for rapeseed strip aerial seeding

UAV can realize track planning and automatic navigation flight due to its small size and flexible operation performance. It has been widely used in the agricultural field for its advantages of high obstacle crossing performance, stability and operation efficiency comparing to ground machines. At present, most UAV based aerial seeding devices use core parts like horizontal centrifugal disc or outer groove wheel to scatter seeds, fertilizers and other materials in the air. Due to the high seeding height and the disturbance of UAV rotor air flow, the randomness of material particles after landing is very large, and they are generally scattered on the whole plane. Although it has high seeding efficiency, it belongs to a relatively extensive seeding mode for that it is not easy to control the seed uniformity affected by many factors. In view of the above problems, a kind of rapeseed aerial seeding device based on an electrically driven centrifugal seeding meter was designed and tested for XAG P20 which is a commercial crop protection UAV. The aerial seeding device can seed in lines instead of wide area, and is more conducive to improve the uniformity of seedlings and the convenience of field management during crop growth.In this study, we first improved the design of the concave cone centrifugal seed metering device and determined the structural parameters of the key components such as seed metering tray and seed metering port. Then, based on ANSYS Fluent simulation software, the distribution of downwash air flow field of the XAG P20 drone was analyzed. An auxiliary seed guiding device used in combination with the centrifugal seed metering device was proposed and built. Three experiments including the seed metering performance test, the prototype test and the field test were carried out to analyze and study the functions of the aerial seeding device. The results showed that the total seeding quantity per unit time increased when the seeding rotation speed increased from 40 to 190 r/min, and the maximum total seeding quantity reached 179.65 g/min at 190 r/min, which can meet the requirements of 0-5m/s operation speed of the drone; the variation coefficient of consistency and stability of apiecerow seeding quantity decreased first and then increased, which were distributed in the range of 4.5%-12.6% and 0.7%-6.2% respectively. The damage rate of seeds increased gradually, but all of which were within 2%. The prototype test showed that when the height of the seed guiding device wasin the range from 1.5 to 2.5 m, the width of the seed strips was less than 1/4 of the row spacing, and the striping index of the seed had no significant correlation with it. However, considering the operational risk and convenience of the personnel in the actual operation process, the height of 2m was selected as the appropriate height of the seed guiding device. Under that condition, the field experiment results showed that the strip index was 35.0%, the variation coefficient of sowing uniformity was 19.26%. The device designed in this study can meet the technical requirements of rape drilling.