Design and experiments of the stepped vibration seed dispersal mechanism for pre-cut cassava planters

Abstract: Efficient and uniform seed metering has been one of the most important operations during crop planting, particularly when a large number of cassava seed stems are stacked arbitrarily in the seed box. It is necessary to innovate the structure and mode of seed supply, posture adjustment, seed control, and seed metering mechanism in recent years. The disorderly stacked seed stems are normally separated to adjust the posture of the seed outward in the process of movement for an accurate number in a sequence. There is the main challenge to controlling the posture of moving cassava seed stems during sowing. In this study, a seed dispersion mechanism with the multi-level stepped vibration was developed in the seed supply link of the pre-cutting seed metering device. A precision sowing was then realized by means of the pile seed stem seed supply, vibration dispersion, and attitude adjustment of the population. The pre-cutting seed metering device was selected to accurately sow the piles of cassava seeds, particularly for the better adaptability of cassava seeds, the order sequence of seeds to be filled, and the high reliability of seed filling. As such, the "vibration dispersion + attitude adjustment" strategy was selected to achieve the purpose of the reliable seed supply. The operation parameters of the mechanism were also optimized by the combination of mathematical modeling, simulation, and experiment. A mathematical model was then established for the movement process of cassava seeds on the multi-stage stepped vibration scattering mechanism. A theoretical analysis was made to determine the sliding movement of cassava seeds relative to the scattering plate, and the throwing movement of cassava seeds on the stepped attitude adjusting plate. The influencing factors were optimized for the performance of the mechanism, including the operation width, vibration frequency, step inclination, and the limit angle. A cassava transverse posture adjustment test was carried out to verify the feasibility of the cassava conveying mechanism, in terms of the discrete factors and the success rate of posture adjustment. Trial production was performed on the test-bed of the seed dispersal mechanism, in order to further determine the parameter combination of the optimal factors. The 4-factor 5-level orthogonal center combination optimization test was conducted to establish the relationship between the influencing factors of mechanism performance and the test indexes. Multi-objective optimization of parameters was conducted to clarify the influence of each factor and the interaction on each index. A combination of optimal parameters was achieved for the better adaptability of four cassava varieties. The results showed that the primary and secondary orders of the test factors on the success rate of lateral attitude adjustment of seed stems were ranked: the vibration frequency, step inclination, limit stop angle, operation width. The primary and secondary order of the test factors on the success rate of scattered seed transportation was ranked: the operation width, vibration frequency, limit stop angle, step inclination. The success rate of a lateral attitude adjustment and scattered seed transportation reached 85.7%, and 88.2%, respectively, when the operation width was 643.41 mm, the vibration frequency was 55.58 Hz, the limit angle was 145.06°, and the step inclination was 80.13°. The adaptability test showed that the cassava seed stems of the other four varieties were reliably adjusted the posture, and then fell into the sliding seed parts in an orderly for subsequent sowing, indicating better adaptability of the improved mechanism.