基于DEM-MBD耦合的精密播种机数字化设计新方法研究

When a precision planting machine works, the contact problem between mechanical parts, such as seed-metering device, fertilizer spreader, furrow opener, covering device, etc. and seeds, fertilizer, soil has always existed, which cannot be analyzed well by the traditional method. This project takes two types of precision planter as the research object, proposes to analyze working process of a precision planter using the discrete element method（DEM）and multibody dynamics（MBD）coupled, and researches the method of establishing the DEM analyzing models of a planter using the multibody dynamics, researches the modeling method of seed particles, fertilizer particles, soil particles, and broken straw particles, researches the contact mechanical models among seed particles, fertilizer particles, soil particles, broken straw particles and planter mechanical parts and the parameter selection method of these mechanical models. On the basis of the theories and methods described above, the analysis method and the software based on DEM-MBD coupling have been developed. The working process of the planter is analyzed using this analysis method, and the analysis results and experimental results are compared, so as to verify the feasibility and effectiveness of the method. On the basis of the work mentioned above, the performances of the planter, such as the sowing depth and the seed spacing variation, etc. in various granular materials and planters in different shapes and sizes was analyzed through changing particle models of the granular materials, the DEM contact mechanical models and the parameters, CAD model of the planter. Thus the optimal dimensional and structural parameters of the planter can be obtained, and a new method for optimal and digital designing of precision planters is put forward.

精密播种机工作时，始终存在着工作部件（排种器、排肥器、开沟器、覆土器等）与种子、肥料、土壤的接触作用，传统方法不能很好地分析该过程。本项目以2种精密播种机为研究对象，提出采用离散元法（DEM）与多刚体动力学（MBD）方法耦合，分析播种机的工作过程，研究由多刚体动力学建立播种机的离散元法分析模型的方法，研究种子颗粒、肥料颗粒、土壤颗粒和碎秸秆颗粒的建模方法，研究种子颗粒、肥料颗粒、土壤颗粒、碎秸秆颗粒和播种机工作部件之间接触作用的力学模型及参数选取方法等，在此基础上研制出基于DEM-MBD耦合的数字化设计方法及其软件。采用该方法及软件分析播种机的工作过程，并将分析结果与试验结果进行比较，以检验该方法和软件的可行性和有效性。在上述工作基础上，通过改变播种机的CAD模型，来分析和评价不同结构及尺寸播种机的性能，由此实现播种机结构和尺寸参数的优化，为精密播种机的优化设计和数字化设计建立一种新方法。

播种机工作时，始终存在着工作部件（排种器、排肥器、开沟器、覆土器等）与种子颗粒、肥料颗粒、土壤颗粒的接触作用，传统方法不能很好地分析该过程。本项目以2种播种机为研究对象，提出采用离散元法（DEM）与多刚体动力学（MBD）方法的耦合，分析播种机的工作过程，研究了由多刚体动力学建立播种机的离散元法分析模型的方法，研究了种子颗粒、肥料颗粒、土壤颗粒和碎秸秆颗粒的建模方法，研究了种子颗粒、肥料颗粒、土壤颗粒、碎秸秆颗粒和播种机工作部件之间接触作用的力学模型及其参数的选取方法等，在此基础上，研制出基于DEM-MBD耦合的数字化设计新方法及其软件AgriDEM。采用该新方法及其软件分析播种机及其部件的工作过程，并将分析结果与试验结果进行了比较，证明了本项目提出的新方法和研制软件的可行性和有效性，为播种机的优化设计和数字化设计建立了一种新方法。