Design and experiment of a track-mounted high-speed precision air-suction dibbler for cotton

Mechanical dibblers widely applied in Xinjiang, China, suffer from structural limitations that restrict their operating speed to merely 3–4 km/h; an increase in working speed will lead to insufficient seed filling, seed blockage and seed damage. Meanwhile, the opening duration of the duckbill opener shortens sharply, preventing timely seed drop and severely reducing seeding quality. To overcome these problems, this study develops a track-mounted air-suction high-speed cotton precision dibbler. It consists of an air-suction seed metering unit, a track-driven duckbill hole opener and an indirect seed delivery mechanism. A V-shaped groove and seed chamber stabilize seed trajectory for accurate delivery into the duckbill, while a track based delayed release mechanism extends the opening duration to enable reliable high-speed operation. A two-stage mechanical model for seed adhesion and transfer was established, determining a critical negative pressure of 7 kPa for stable adhesion. Critical conditions for seed adhesion and tangential acceleration were derived, and seed motion was analyzed. CFD–DEM and MBD–DEM coupled simulations were carried out to analyze seed flow patterns, drag forces and seed kinematic trajectories. The simulation results validated the delayed seeding performance, with a seed falling duration of 0.23 s and a duckbill opening duration of 0.47 s. Bench tests were performed with travel speed, suction hole diameter and negative pressure as experimental variables. The optimal parameter combination was determined as 6 km/h travel speed, 3.2 mm hole diameter and −6.9 kPa negative pressure. Soil trench tests yielded a qualification index of 91.86%, a missed sowing index of 3.18%, a reseeding index of 4.96%, a plant spacing qualification index of 94.6%, a sowing depth qualification index of 90.3%, and a hole dislocation index of 0.9%., meeting the requirements for high-speed precision cotton seeding in Xinjiang.