Abstract:Precise seeding technology has become an important direction of vegetable seeder development. Considering the characteristics of multi-varieties and large differences in vegetable seeds, the requirements for sowing are also different. According to the above practical problems，a pneumatic-sheave combined precision metering device was designed which owned advantages such as simple structure and suitable for various vegetable seeds. The precision metering device adopted a two-stage seeding mode. The small grooved wheel seeding device adopted for the first part, negative pressure to adsorb seeds and positive pressure to remove seeds were adopted for the second part. Three-dimensional laser scanning and three-dimensional point cloud calculation method were used to measure the three-axis size of pakchoi, radish and eggplant seeds. Based on these data, several shapes of suction nozzles such as through hole, conical hole, cylindrical hole and kidney ellipsoid hole were designed. The single-factor test was used to obtain the best chamber vacuum for seeder. By applying the single factor text for vacuum degree, optimal result showed that most suitable vacuum degrees for pakchoi, radish and eggplant were 4kPa, 5kPa and 3kPa, respectively. The optimal metering tray speed and suction nozzle type hole were obtained by the complete combination test. The result showed that when the rotational speed of the metering tray was 17.5~22.5r/min, the metering device qualified rate was high, especially at 20r/min. The suction nozzle type holes suitable for pakchoi, radish and eggplant were conical holes, kidney ellipsoid hole and through hole, respectively. Under the optimal suction nozzle, vacuum and rotational speed conditions, the qualified rates of pakchoi, radish and eggplant were 97.0%, 95.4% and 93.7%, respectively, which could completely meet the requirement of seeding index.
