Performance optimization test on air-suction potato seed metering device with positive pressure airflow and zero-speed seeding

Abstract: The existing zero-speed seeding technology has many disadvantages, such as being not suitable for high speed operation and the seed charge position too high. To make up for these shortcomings, a new technique of zero-speed seeding was proposed. This technology can also improve the precision of potato sowing. The positive pressure air was used as the driving force making the dropping tuber accelerated along the opposite direction of the seeding machine. In the process of falling, the horizontal velocity of tuber was zero relative to the ground. The zero-speed seeding technique was applied to sowing potato with this method. On the basis of the analysis of the throwing process, the main factors that affected the performance of zero-speed seeding were obtained, and the range of the test values of each factor was determined. These main factors were positive pressure, throw angle and rotation speed of the device. With these parameters as the experimental factors, a dual quadratic orthogonal rotational regressive test was designed. The qualified index, multiple index, missing index and coefficient of variation were selected as evaluation indices according to the national standards. The regression mathematical models between the indices and the factors were established after the test. The impacts of the factors on the evaluation indices were analyzed by using these mathematical models. The effects of positive pressure and rotation speed on the 4 indices were significant or highly significant. The throw angle had only a slightly significant effect on the coefficient of variation. When the seed metering device's rotation speed was 25-31 r/min, the main factor affecting the performance of seeding was the rotation speed. Each index value changed slightly with the change of positive pressure. When the seed metering device's rotation speed was 31-40 r/min, zero-speed seeding function of the positive pressure could effectively improve the quality of seeding. The qualified index increased and the coefficient of variation decreased with the increase of the positive pressure. At the same time, these 2 indices, the multiple index and the missing index, both had different degrees of decline. Parameters were optimized based on regression models. With the maximum qualified index, the minimum variation coefficient, the minimum multiple index and the minimum missing index as the optimization objectives, the ranges of the factors were as follows: the positive pressure of 5-15 kPa, the throw angle of 45°-75° and the rotation speed of 25-40 r/min. And taking into account the agronomic requirements of potato cultivation, the missing index was expected to be not greater than 3%. Optimization results showed that, the qualified index was 95.22%, the multiple index was 3.51%, the missing index was 1.27% and the variation coefficient was 9.43% under the condition of the positive pressure of 15 kPa, the throw angle of 57° and the rotation speed of 35 r/min. The seeding performances of developed device met the requirement of precision seeding. Results in the research give the guidance for the optimization of air-suction potato seed metering device, and provide a technical support for improving the seeding accuracy of potato and many other crops.