Design and validation of a centrifugal variable-diameter pneumatic high-speed precision seed-metering device for maize

A high-speed seed-metering device was designed utilising centrifugal force for seed filling and clearing and air movement to achieve efficient and stable single seed filling. To avoid irregular movement of seeds in the seed-metering device after their removal from the dispenser, a shell external refilling system was added to provide for the orderly and uniform filling and removal of seeds. The seeding plate, its dispenser, the seed protection board, and the front shell were designed based on the triaxial dimensions of maize seeds. Theoretical analyses were performed for seed filling, transport, and clearance. Single-factor and Box-Behnken central composite experiments were performed investigating operating speed, air pressure, and number of duplicate fillings (NDF) with qualified, multiple, and leakage indices used as indicators. Response surface method clarified the effects of various factors on the indicators and the experimental results were analysed by the objective optimisation method. The optimal seeding performance parameters were an operating speed of 15.4 km h−1, air pressure of 3.6 kPa, and NDF of 23 grains. Under these conditions, the qualified, multiple, and leakage indices were 95.73%, 2.53%, and 1.73%, respectively. A high-speed adaptability test was performed at 3.6 kPa air pressure and 23 grains NDF. The results demonstrated that with an operating speed in the range 10–18 km h−1, the qualified index is >92%, and the multiple and leakage indices are <5%, indicating that the operating speed has no significant effect on the seed-metering performance, meeting the requirements of high-speed precision seeding.