Design And Experiment On Loss Sowing Detection And Reseeding System Of Precision Metering Device For Rapeseed

Seeding is one important process of agricultural production. Precision seeding technology is the key technology to achieve precision seeding. Precision seeder is a core component of precision planter work, including mechanical and pneumatic seeding. As rapeseed has characteristic of the small size, light quality, high oil content, high frequency seeding, easily broken and so on, sowing quality can’t be guaranteed easily. And loss sowing is one of the important indicators to measure performance of precision metering device. Seeding faults such as the lack of seeds in the seeding box, clogged seeding holes, transmission fault, and faster rotation speed of seeding plates will lead to loss sowing during the seeding operation. Numbers of continuous clogged seeding holes will cause periodic blank misses in a row or several rows, which will affect crop yield seriously. So it is necessary to study on loss sowing detection for rapeseed precision metering device and reseeding automatically and accurately so as to improve the planting operation quality and efficiency.Based on the analysis of current situation on loss sowing detection and reseeding for precision metering device at home and abroad, a system of real-time loss sowing detection and reseeding automatically for rapeseed precision metering device of combined seeder was designed. In this study, on the grounds of concepts of sparse miss and blank miss, a method of real-time loss sowing detection for rapeseed precision metering device based on time changed window was put forward. Experimental study on real-time and accuracy of this method detection were carried out. A new kind of structure of spiral-tube reseeding device for rapeseed was presented. Experiments were also taken to analyze the relationships between seeding quantity and rotation speed of spiral-tube reseeding device. And the relationship model between reseeding rotation speed of spiral-tube reseeding device and loss sowing coefficient was established. A system was integrated designed by both method of real-time loss sowing detection for rapeseed precision metering device based on time changed window and reseeding device. When the detection system detected precision metering device occurring loss sowing, the reseeding device reseeded automatically and variably within the current time window to eliminate loss sowing. Tests were carried out for this system. The main research contents were conducted as follows:(1) A method of real-time loss sowing detection for rapeseed precision metering device based on time changed window was presented and tests for this system were carried out. Based on the concepts of sparse miss coefficient and blank miss coefficient, and analysis of relations between two coefficients of two-dimensional plane and loss sowing, one double-threshold(including seeding frequency and seeding time interval) decision method was put forward, in which a standard seeding pulse sequence was developed to sense the seeding speed. It was effective and necessary to establish two coefficients to detect sparse miss and blank miss especially under both situations of multiple seeding and inadequate seeding. It covered all the possible type of loss sowing for rapeseed precision metering device. Therefore, a real-time loss sowing detection system was designed. Tests of real-time loss sowing detection for the pneumatic rapeseed precision metering device were carried out. Test results showed that the detection system could adapt the time window for the variation of seeding speed and calculate the sparse miss coefficient and blank miss coefficient accurately. Sparse miss and blank miss were detected accurately with one setting coefficient and loss sowing decision rule.(2) A new kind of structure of spiral-tube reseeding device for rapeseed was designed and experimental study on seeding characteristic was carried out. It was designed to solve the problem of reseeding for rapeseed precision metering device. 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. 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. So the number of spiral tube for reseeding device was seven. And the range of working rotation speed for spiral-tube reseeding device was 25.7-171 r/min.(3) Loss sowing detection and reseeding system of precision metering device for rapeseed was integrated designed and tests were carried out. Both method of real-time loss sowing detection for rapeseed precision metering device based on time changed window and reseeding device were integrated designed. The component and working principle of the system were determined. The important working parts of reseeding module such as step motor and step motor driver were selected. Experiments of real-time loss sowing detection and reseeding system for rapeseed precision metering device were carried out. Tests results showed that the integrated system could adjust its working speed to reseed automatically according with different loss sowing coefficient during one time window. Reseeding times was equal to metering device’s equivalent loss sowing quantity within the current time window. 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. There was 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 sowing quality of rapeseed precision seeder. It will provide an important reference for precision metering device to sowing intelligently.