摘要
分插机构决定秧爪尖运动轨迹,并影响插秧机作业质量。由于杆件受力和运动副磨损,分插机构参数随时间变化,并导致分插机构轨迹变化。从分插机构参数随时间演化的角度出发,基于连续时间模型和伊藤引理,推导了插秧机分插机构轨迹的时变不确定性分析计算公式,将分插机构轨迹的不确定性由其漂移函数和波动函数表达,漂移函数和波动函数则取决于分插机构服从伊藤过程的随机参数(即杆长)的漂移率和波动率,从而建立了分插机构轨迹的时变不确定性分析方法。这是一种涵盖传统分析的新方法。以插秧穴口的宽度为目标函数,基于分插机构轨迹的时变不确定性分析方法,建立分插机构轨迹可靠度计算模型,求解插秧机随时间变化的漂秧率。通过实例说明了该方法的计算分析方法。实例中的计算结果表明:从零时刻开始到t=300h,漂秧率始终低于2%;到t=400h时,漂秧率接近10%。该方法具有一定普适性,可用于其它各种杆机构的可靠性分析。
The separating-planting mechanism decided the trajectory of seedling claw,which also influenced the working quality of rice transplanting.Due to the internal force of linkage and the wear of revolute joint,parameters of separating-planting mechanism were changed over time.What’s more,the trajectory of separating-planting mechanism changed.Considering the evolution of parameters of separating-planting mechanism,basing on the continuous-time model and the Ito Lemma,established an Evolution-Based Uncertainty Analysis(EBUA)model of separating-planting mechanism trajectory.In this model,the uncertainty of trajectory expressed by drift functions and volatility functions,which decided by the drift rates and volatility rates of separating-planting mechanism parameters(the linkage length).And the parameters were random but followed Ito Process.This method included the traditional analysis method.Taking the pit width of transplanter for example,which decided the percentage of floating seedling.Simulating the changes of the linkages,thus the percentage of floating seedling at different times can be calculate based on the analytical model about the time varying trajectory.From the moment t=0 to t=300h,the percentage of floating seedling always below 2%;at the moment t=400h,the percentage of floating seedling closed to 10%;at the moment t=500h,the percentage of floating seedling reached up to 22%.These data showed that with the evolution the percentage of floating seedling augmented at a speed gradually increased.With the use of evolution-based uncertainty analysis(EBUA),the percentage of floating seedling at any time can be forecasted,and this method is much more realistic.Actually,the separating-planting mechanism is a four-bar linkage,so this method can be applied to the other analysis of the similar mechanisms.
作者
付建华
石博强
余国卿
李国广
FU Jian-hua;SHI Bo-qiang;YU Guo-qing;LI Guo-guang(School of Mechanical Engineering,University of Science and Technology Beijing,Beijing 100083,China)
出处
《机械设计与制造》
北大核心
2019年第12期1-4,共4页
Machinery Design & Manufacture
基金
国家自然科学基金资助项目(51075029)
关键词
插秧机
分插机构轨迹
曲柄摇杆机构
时变不确定性分析
Transplanter
Separating-Planting Mechanism Trajectory
Crank-Rocker Mechanism
Evolution-Based Uncertainty Analysis(EBUA)
