Theoretical and experimental analyses of high-speed seed filling in limited gear-shaped side space of cotton precision dibbler

Abstract

A novel state-of-motion adjustment method of seeds for high-speed seed filling in a cotton precision dibbler is proposed to solve the problems of arch lifting (multiple particles squeezing each other and causing congestion) and leakage (caused by exceedingly high relative linear velocity between the seed and seed tray during the seed-filling process). This method is based on the stress of the seed group and the limited gear-shaped side space (seed holding space). Kinematic and dynamic analyses of the main states of motion of the seed in the holding space were conducted, and the effects of the stress and movement states on seed-filling performance and automatic seed-cleaning performance were investigated. Through simulation, the velocity fluctuation timings of transverse and longitudinal rotation fillings in the holding space were compared. It was found that sufficient arrangement and a full state-of-motion adjustment on the seed-arranging surface was the key condition to ensuring that seeds fill the type hole by transverse rotation of the seed-filling surface. When seeds were not fully arranged and their state of motion not fully adjusted on the seed-arranging surface, the structural design of the type hole, seed-cleaning surface, and seed-filling surface affected the filling result of longitudinal rotation. The Box–Behnken centre combination method was implemented by setting the friction coefficient μ1 (X1), seed height z (X2), and rotation speed n (X3) as the factors with the qualified index A, leakage index M, and velocity fluctuation ΔH as the evaluation indexes. Multiple regression models and response surface optimisation analyses were performed to obtain the optimal combination of parameters affecting the dibbler seed-filling performance. The results indicated that the most significant factors affecting the A, M, and ΔH, were: z >n > μ1, z >n > μ1, and n >z > μ1. The optimal combination of these parameters was μ1 = 0.463, z = 0.4 kg, and n = 1.88 rps (approximately 9.78 km/h), providing a maximum A = 98.837 %, minimum M = 0.199 %, and ΔH = 0.111 m/s. When ΔH was in the interval of 0.09–0.18 m/s, A was high and stable, whereas M was small, indicating that the seed-filling performance was effective. When μ1 = 0.48, n = 1.5 rps (approximately 7.8 km/h), and z = 0.3 kg, the average values of the bench test were 91.07 % and 6.07 %, consistent with the simulation results. This study contributes significantly toward the research and development of the type hole of precise dibblers, high-speed seed selection method, orderly arrangement, migration, and quantitative separation method of irregular rotary material groups.