| Pneumatic precision planter for rapeseed has been used extensively due to its perfect performance on metering recently. Pneumatic seed-metering system is the key components of this planter, and its working parameters and seeding performances directly affect the planter’s operating performances which contain the apiece row consistency of seeding quantity, the stability of the total seeding quantity of the planter, et al. On the basis of JPS-12, testing system of pneumatic seed-metering device for rapeseed, and field experiment of the pneumatic seed-metering system, experimental study on the system have been performed in this paper using the methods of probability statistics, multivariate statistical, and integer programming. Main research contents of this paper were conducted as follows:(1) A testing system of pneumatic seed-metering device for rapeseed which contained the frame, dynamic system, transmission system, pneumatic system, seed metering device, detection system, and control system, was designed in this paper. It could be used to investigate the performance of the pneumatic seed-metering system working with different rotational speed of fan, rotational speed of sowing disc, and the outlet size of positive pressure tube, and to provide solutions of the pneumatic seed-metering system for optimization of the parameters and improvement of the structure.(2) In order to study the distribution of rapeseeds sowed by pneumatic seed-metering system, fifty-eight samples which totally contained about7,041seedlings were collected using the Grid method, and statistical analysis had been carried out by the methods of Curve fitting, ANOVA and Duncan multiple range test. Results indicated that the spacing of rapeseeds for each row obeyed exponential distribution whose parameters were0.0245,0.0296,0.0264,0.0294,0.0283and0.0308, respectively. The range of correction coefficient for theoretical spacing was from1.172to1.250. The stability of the total seeding quantity of the system was reliable. The error between the real row spacing and the theoretical row spacing was less than5%, and the triangle expression of Fourier series could be used to analysis the stability of real row spacing. The distribution obtained from this experiment can provides the optimization of structure and the improvement of seeding process for the planter and its pneumatic seed-metering system, and it is also of great value to the operation of the planter.(3) On the basis of the testing system, the effect of three fators which were rotational speed of fan, rotational speed of sowing disc, and the outlet size of positive pressure tube on the seeding performance of pneumatic metering system of the seeder for rapeseed was conducted. Full Factorial experiment which includes320-times factors combination was used in the course of the study. The Datum obtained from the experiment was processed by means of Multivariate Nonlinear Regression. The results showed that the factors could be ranged in the order of rotational speed of fan> rotational speed of sowing disc> the outlet size of positive pressure tube, the factors which mostly influence the seed rate of the system and its uniformity respectively were rotational speed of fan and its interaction with rotational speed of sowing disc. With the increase of fan speed and the decrease of rotational speed of sowing disc at a certain range, the performance of system was stable. When the outlet size of positive pressure tube was20mm or30mm, the apiece row consistency of seeding quantity of the system was the best. The equations of seed rate and its uniformity were founded, and all of the factors combination which could make sure that seed rate of the system was90%were drawed. The conclusion is valuable for choosing the optimal parameters matching and esstimating the perfomance of the planter and the pneumatic seed-metering system.(4) To research relationships among the parameters of pneumatic seed-metering system which were about flow rate and pressure of each negative pressure branch tube, flow rate of the total negative pressure tube, rotational speed of fan and sowing disc, the outlet size of positive pressure tube, and to study these parameter’s action laws to seeding performances of the system, the models of these relationships and action laws were constructed in this paper. A two-layer Artificial Neural Networks model had been constructed which was about the relationship between flow rate of the total negative pressure tube and flow rate of each branch negative pressure tube. A binary quadratic polynomial model was established to describe the relationship between the flow rate of total negative pressure tube and fan rate, outlet size of positive pressure tube, the results showed that the contours of fan flow showed a parabola type, and when the outlet size of positive pressure tube changed from35to40mm, the flow rate of total negative pressure tube could came up to maximum value on different rotational speed, and when rotational speed of planter plate was less than40r/min and fan flow was less than140Nm3/h, sowing-consistency of the system was less than5percent, and in a certain range of fan flow and rotational speed of planter plate, the system had good performances on sowing-consintency and seed rate. According to the regression equation, pressure with flow rate of each negative pressure branch tube was well fitted by testing flow rate and pressure of the seed-metering device. Flow rate of the total negative pressure tube, flow rate and pressure of each negative pressure branch tube could be calculated through these models with the fan rate and outlet size of positive pressure tube certained. This fan rate and outlet size can also be modified by some equations established in this paper. The models constructed in this paper had expounded the mutual laws among the parameters of the system and also had described the action laws of these parameters to the operating performances of the system.(5) An integer programming model containing3variables which were rotational speed of fan, rotational speed of sowing disc, the outlet size of positive pressure tube, and2constraint equations which were the equations of seed rate of the system and its uniformity, was investigated in this paper. And more than80,000integer solutions, all of which could make sure that the average seeding quantity of the system was more than36and the variation coefficient which was about the consistency of seeding quantity of the system was less than5%, were solved by using the software of MATLAB. The results showed that these models were valuable for optimization of operating performance of the system. |
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