| Currently, China is not only the world’s largest vegetable producer and consumer, but also the world’s largest exporter of vegetable. At present, Chinese cabbage vegetable planting pattern can be roughly divided into two types: seeding transplantation and direct seeding. It requires breeding in advance with complex planting processes, requires large amount of labor in the production process, and has low production efficiency, which seriously restrict the development of vegetable industry.Considering the three facts that the size of Chinese cabbage seeds is small, that the seeding rate is difficult to control, and that sowing mechanization in practical agricultural production is low in China, a precision planter for quasi-spherical vegetable seed adopting inside-filling pneumatic centralized precision metering device is developed. Precision vegetable planter for vegetable is aimed at solving such problems as uneven seeding spacing, poor seeding machine adaptability, excessive consumption of labor in seeding process and high cost in seeds purchasing. The main research content is as follows:1) Measurement and analysis of the physical property of quasi-spherical vegetable seeds. The seeds of pakchoi, Chinese cabbage, and rape were regarded as research object. This paper measured triaxial size of seed and 1000-grain weight, analyzed sphericity and triaxial size of seeds. The experiment results showed that 1000-grain weight of different kinds of seeds was different at the range of particle size. The sphericity of all seeds was above 94%. The size of length, width, and height of all seeds was normal distribution. All of these supported theoretical foundation for design of seeding cylinder of inside-filling pneumatic precision centralized metering device.2) Design of a precision planter for quasi-spherical vegetable seeds. Considering the three facts that the size of seeds is small, that the seeding rate is difficult to control, and that sowing mechanization in practical agricultural production is low in China, a precision vegetable planter with the function of remote control was developed to achieve the effect “six rows of sowing for one time†according to inside-filling pneumatic centralized seeding principle. This paper analyzes and determines the main structure and technical parameters of vegetable planter. Based on the agronomic requirement of different kinds of vegetable planting, this paper determined the parameter matching of main parts including metering device system, dynamic system, suspension system, remote control system, and land wheel driving device.3) Design and analysis of inside-filling pneumatic precision centralized metering device. A prototype of an inside-filling pneumatic precision centralized metering device with the ability to sow six rows at a time was developed. This paper analyzed and determined the main structure and technical parameters of the prototype. Dynamic analysis of negative pressure and rotating speed of the seeding cylinder was carried out in this paper. Based on the physical property of measured vegetable seeds, this paper determined the structure of air chamber, quantity of radical and axial holes in the seeding cylinder, and the diameter of type holes. This paper experimented on different varieties of seeds, diameter of type hole, positive pressure, and rotating speed on the influence of dropping seeds trajectory for analyzing the migration rule in dropping seeds link. The high-speed photography was adopted to shoot the falling trajectory in dropping seeds link. The coordinate points of seed were collected by use of relevant software tools and the equation of the dropping seeds trajectory was established. The structure of the dropping seeds opening and guiding seed tube was improved by 3D print technology.4) Performance experiment and testing research of the precision planter for quasi-spherical vegetable seeds. Considering the seeding performance as main evaluation index, an experiment on the influence of positive pressure on single row performance was conducted to determine the seeding performance indexes. In addition, an experiment on the influence of negative pressure and rotating speed on single row performance was conducted. An experiment was also conducted to determine the stability and consistency of each row.This paper experimented on vibration displacement test of the power machine, slip ratio of the land wheel and steadiness of the total sum of seeds weight, and the seeding emergence condition of field for comprehensive analysis and evaluation working performance of the planter. The bench experiment results indicated that there was no discernable change in the performance of the prototype when the positive pressure ranged from 200 to 1200 Pa. The quality of feed index(Iqf) was 92.48%, and the miss index(Imiss) was below 2.6% when the rotating speed was 16r/min, the positive pressure was 200 Pa, and the negative pressure was-1600 Pa. The Iqf of each row was above 86.5%, the stability coefficient of variation(CV) of each row was below 4.6%, and the consistency CV of each row was below 0.9%. The damage rate was 0 when the rotating speed was 16r/min, the positive pressure was 200 Pa, and the negative pressure was-1400 or-1600 Pa. The test results concluded that the peak value of the vibration displacement was high. The slip ratio of the land wheel ranged from 6% to 8%. The turning radius of the prototype was 1.8m. Each row consistency variability coefficient of seeding quality was less than 9.5% and the stability variability coefficient of the overall seeding quality was less than 5%. It can be concluded from the experiment results that the pakchoi had better emergence effect, and that no significant differences in plant distribution and no deficiency seeding phenomenon between the manual driving and the remote driving. Therefore the two different kinds of planting ways were both satisfactory for the requirements of precision seeding in actual production。... |
