Objective  In order to expand the applicability of transplanter and realize the automatic feeding of plug seedlings of various specifications of vegetables, this paper designs a universal automatic seedling-feeding device for vegetable transplanting machine.

Method  The seedling-feeding arm with an adjustable feeding claw was designed, the key parameters were optimized and kinematic analysis was performed. Plug trays with different number of holes could be used by adjusting the number and distance of feeding claws on the seedling-feeding arm and choosing different PLC control programs. The key factors affecting the success rate of seedling feeding were comprehensively considered by analyzing the working process of seedling feeding. Taking the water content of the plug, the height of plug seedling, and the depth of seedling needle into soil as the test parameters, the plug seedlings of lettuce in 72-, 105- and 128-hole plug as the test objects, single factor experiment and multi-factor orthogonal experiment were carried out to explore the effect of different factor on the success rate of seedling feeding.

Result  The test results showed that when the water content of plug seedling substrate was 40%, seedling height was 50 mm, and the depth of seedling needle into soil was 38 mm, the success rates of seedling feeding for adjustable seedling feeding device were the highest, and the seedling-feeding success rates of lettuce in 72-, 105- and 128-hole plug trays were 95.83%, 96.19% and 96.48%, respectively.

Conclusion  The design of adjustable seedling-feeding device meets the technical requirements of vegetable transplanting machine for feeding seedlings, and the transplanting effect is good, which can provide a reference for research and development of the universal automatic vegetable transplanting machine.