预切种木薯播种器阶梯式振动散种机构设计与试验

针对预切种播种器对成堆木薯种茎进行精密播种时待充木薯种茎乱序、充种可靠性低等难题，在播种器供种环节设计一种阶梯式振动散种机构。建立了木薯种茎在阶梯式振动散种机构上运动过程的数学模型，对木薯种茎相对散种板的下滑运动和其在阶梯式调姿板上的抛掷运动进行理论分析，确定显著影响机构性能的因素分别是作业宽度、振动频率、台阶倾角以及限位挡角。基于离散元法（Discrete Element Method，EDEM）建立了木薯种茎-振动散种机构的仿真模型，单因素仿真试验明确了各因素对横向调姿成功率和散种输送成功率的影响规律。研制了阶梯式振动散种机构试验台，进行四因素五水平正交中心组合试验研究，并基于最优的因素参数组合对4个不同品种的木薯进行适应性测试，确定最佳参数组合。结果表明当阶梯式振动散种机构的供种箱作业宽度为643.41 mm、振动频率为55.58 Hz、限位挡角为145.06°、台阶倾角为80.13°时，横向调姿成功率为85.7%，散种输送成功率为88.2%；当在最优因素参数组合下进行试验，横向调姿成功率为85.6%，散种输送成功率为88.6%。研究为预切种式木薯精密播种器相关装备的研制提供指导参考。

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.