Objective  The small-grain seed has the characteristics of small size, light weight and irregular shape. The problems of blockage of seed suction hole, seed damage and poor seeding uniformity often occur in the operation of traditional seed metering device. Therefore, on the basis of seed pelleting technology, an air-suction precision hole sowing seed metering device for small seeds was designed.

Method  The seeding process was simulated by Rocky discrete element simulation software by measuring relevant parameters such as seed size and friction angle. In order to obtain the best performance factor combination of the seed metering device, the quadratic regression rotation orthogonal experiment was carried out, and a multi-objective optimization method was used to optimize the factors affecting the performance of seed metering device.

Result  Through the test of regression coefficients, the primary and secondary order of the factors affecting single grain rate and leak seeding rate of the seed metering device was air pressure and rotation speed of seed metering device. When the rotation speed was constant, with the increase of the negative pressure, the single grain rate increased, and the leak seeding rate decreased; When the negative pressure was constant, with the increase of the rotation speed, the single grain rate decreased, and the leak seeding rate increased. When the negative pressure was greater than −2 800 Pa, the rotation speed of 5−30 r/min had less obvious influence on single grain rate and leak seeding rate of the seed metering device, and the single grain rate was all above 90%, the leak seeding rate was all below 10%.

Conclusion  Through optimization, the optimal working parameter combination is the rotation speed of 15 r/min, the negative pressure of −2 300 Pa, and the positive pressure of 500 Pa. The performance indicators of the seed metering device under these conditions are as following: The average single grain rate qualified index is 96%, the average leak seeding index is 3.37%, and the average replay seeding index is 0.267%, which conforms to the national standard requirements.