Aiming at the problems that the trajectory of fixed cavity formers of rolling spoon-type precision cavity seeders is in the form of a residual pendulum line, and the residual pendulum line is too large, which causes tearing and picking of the film, and in order to reduce the variability of the spacing of the plants, the simulation and analysis of the motion process of the cavity seeders are conducted based on discrete element method and multi-body dynamics coupling method. Taking the traction speed, traction angle and cavity seeder quality as the influencing factors, and the residual pendulum width, plant spacing and sowing depth as the response values, the influence law of each factor on the response values is determined through pre-test and single-factor test. Based on the results of the pre-simulation test, a multi-factor simulation test is carried out to obtain the optimal parameter combinations and to verify the reliability of the optimal results through the field test. The results show that: The optimal parameter combination of rolling spoon-type precision cavity formers is traction speed 523.43 mm/s, traction angle 21.9° and cavity seeder mass 18.2 kg. Under above condition, the plant spacing is 196.84 mm, and the width of the residual pendulum line is 13.98 mm. The optimal parameter combinations for the validation test are the plant spacing 193.86 mm with relative error 1.51%, the residual pendulum line 13.28 mm with relative error 4.39%.
根据石林榕等[15]针对西北旱区农田土壤颗粒模型标定,EDEM接触模型采用Hysteretic spring contact model(HSCM)、Standard rolling friction和Linear Cohesion model(LCM),颗粒间的阻尼系数和刚度系数为0.05和0.95,其他参数参考见表1。
在穴播器与土壤相互作用的耦合仿真中,虚拟样机中与离散元法土壤的相互作用的部分需要以wall的形式输出。Recurdyn通过wall接收来自EDEM的外力,EDEM则通过wall接收Recurdyn的接触几何的运动数据[17],wall文件通过EDEM中“Import Geometry from RecurDyn”功能导入。固定成穴器运动轨迹经Trace功能将建立的Marker点和旋转中心的轨迹显示出来(图5)。
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