基于DEM-MBD耦合算法的自激振动深松机仿真分析

自激振动深松机的设计主要采用田间试验及理论分析方法,但田间试验成本高、周期长,同时理论分析尚不具备完整准确的解析解。为提高该类机具的设计效率,保证设计结果的准确性和可靠性,本文在课题组研制的Agri-DEM软件平台上,添加了离散元法（DEM）与多体动力学（MBD）耦合算法,然后利用该算法对自激振动深松单体作业过程进行仿真分析。耦合算法中,采用MBD方法建立了台车-深松机-悬挂架-土壤的系统动力学模型,包括7个活动刚体、1个滑移铰、7个转动铰、1个滑移驱动、1个弹簧力约束和1个阻尼约束,同时利用广义坐标分块算法将系统微分代数方程组转化为微分方程组,并通过亚当斯-莫尔顿校正算法进行积分,求解获得各刚体的运动学参数和动力学参数;采用DEM方法建立了耕作土壤的离散元模型,考虑土壤颗粒的黏附力,提出一种适合于土壤等湿颗粒间的接触力学模型——湿颗粒模型,模型参数通过试凑法确定。对模型进行深松铲的动力学响应分析、弹簧及牵引力动力学响应分析和土壤扰动过程分析,仿真结果表明：土槽台车前进速度为0.5m/s时,机具牵引力周期性变化的区间为-331.06~1492.75N,最大牵引力为1492.75N;深松铲的入土角周期性变化的区间为0~-0.11rad,在高度方向上铲柄质心的变化区间为-400.33~-581.37mm;激振弹簧受载也呈周期性变化,变化区间为2623~-2231N;深松铲铲尖部位抬升土壤,土壤颗粒扰动量在铲尖区域最大,并沿深松铲前进方向和侧向依次递减。仿真结果直观的呈现了自激振动深松机的作业过程及土壤颗粒的运动情况,定性的解释了自激振动深松机的减阻机理。本文添加的DEM-MBD耦合算法,为自激振动深松机工作过程分析和优化设计提供了一种新方法。

Analysis on Operational Process of Self-excited Vibrating Subsoiler Based on DEM-MBD Coupling Algorithm

In order to increase the design efficiency of self-excited vibrating subsoiler, ensure the accuracy and reliability of design results, DEM-MBD coupling algorithm developed by Agri-DEM was employed, and the operational process of type 1S-300 self-excited vibrating subsoiler was simulated. Through MBD modules, a system dynamics model was established, including trolley-subsoiler-suspension-soil. Based on DEM modules, a discrete element model of soil with consideration on the adhesion of soil particles was established. The wet particle model was used, which was invented by the research team, as the contact mechanics model of soil particles, and the model parameter was identified by repeated tests. After disturbance analysis of soil, traction analysis of trolley and dynamic response analysis of subsoiling shovel, the outcome indicated that when the subsoiling shovel entered the soil, the soil above the shovel top was lifted, and the soil on both sides of the shovel edge was divided by cutting, the resistance range was from 363N to 1000N,the change interval in the height direction of the subsoiler was from 0mm to 181mm,the spring load change interval was from 2623N to -2231N. If the torque of subsoiling shovel caused by soil particles was higher than that caused by a spring, the shovel would rotate anticlockwise by centering the hinge point. Simulation results directly reflected the cyclical change of tillage resistance, as well as the movement of soil particles. Furthermore, it explained the resistance reduction mechanism of self-excited vibrating subsoiler. To sum up, DEM-MBD coupling algorithm provided a new approach for the development of this model.