基于POT模型的大功率拖拉机传动轴载荷时域外推方法  

Time domain extrapolation method for load of drive shaft of high-power tractor based on POT model

作　　者：杨子涵 宋正河[1] 尹宜勇 赵雪彦[1] 刘江辉 韩建刚 Yang Zihan;Song Zhenghe;Yin Yiyong;Zhao Xueyan;Liu Jianghui;Han Jiangang(Beijing Key Laboratory of Optimized Design for Modern Agricultural Equipment,China Agricultural University,Beijing 100083,China;Luoyang Xiyuan Vehicle and Power Inspection Institute Co.,LTD,Luoyang 471000,China)

机构地区：[1]中国农业大学现代农业装备优化设计北京市重点实验室,北京100083 [2]洛阳西苑车辆与动力检验所有限公司,洛阳471000

出　　处：《农业工程学报》2019年第15期40-47,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点研发计划资助项目(2017YFD0700301);北京市自然科学基金资助项目(3184053)

摘　　要：为得到大功率拖拉机传动轴在田间作业工况下的载荷谱,该文针对传统传动系载荷谱编制过程中雨流计数及雨流域外推方法的局限性,提出基于POT(peak over threshold)模型的大功率拖拉机传动轴载荷时域外推方法。首先搭建了拖拉机传动轴扭矩测试系统,利用无线扭矩传感器采集大功率拖拉机传动轴在田间犁耕作业工况下的载荷数据;基于极值理论建立POT模型,利用灰色关联度分析方法选取最优阈值,确定时域载荷数据中上限、下限阈值分别为497和333 N·m。对超越阈值的极值载荷进行提取并利用广义帕累托分布(generalized pareto distribution,GPD)对极值载荷的分布进行拟合,拟合结果与极值载荷样本之间的相关系数均大于0.99,将生成服从GPD的新极值点取代原样本中的极值点从而实现时域载荷数据的外推。结果表明,GPD能够准确描述大功率拖拉机传动轴载荷超越阈值的分布情况,与雨流域外推方法相比,基于POT模型的载荷时域外推方法不仅可以获得任意里程的载荷时域序列,还能够极大程度保留实测载荷循环的次序,为今后大功率拖拉机传动系的室内载荷谱加载试验提供更加真实可靠的数据支持。Tractor transmission shaft is one of the components that affect the reliability of the tractor.Compiling load spectrum which can reflect the actual working conditions of high-power tractor drive shaft is of great significance to improve the reliability of the tractor.It is time consuming and expensive to obtain the actual measurement for load spectrum of the whole life cycle,so extrapolated methods are always applied by using the load spectrum of the limited measurement duration.However,the traditional method of rain flow counting and rain basin extrapolation in the process of compiling load spectrum of transmission system has limitations,this paper proposed a POT(peak over threshold)model based time domain extrapolation method for driving shaft load of high-power tractor.Firstly,a set of wireless torque measurement system for tractor transmission shaft is built,which mainly includes strain gauges,batteries,wireless strain nodes and wireless acquisition terminals.The strain gauge is pasted on the proper part of the tractor drive shaft and connected with the wireless torque node.The wireless transmitter is encapsulated in the wireless torque node and transmits the measured torque signal to the wireless receiver synchronously.The test data of the drive shaft under field working conditions are stored in a portable computer connected to a wireless receiver.Then,POT model is established based on extremum theory to extract the peak and valley values of the test data and eliminate the small load cycles,and the intervals of the optimal thresholds are determined by using the mean excess function graph,which are[492,501]N·m for the upper limit and[325,334]N·m for the lower limit,respectively.Thirdly,the data in the threshold interval is divided according to a certain gradient,and the fitting effect corresponding to each threshold is preliminarily tested by calculating R-square.The grey relational degree analysis method is used to select the optimal threshold and calculate the grey relational degree of each threshold in t

关 键 词：农业机械 参数估计 模型 POT 载荷 时域外推 广义帕累托分布 传动轴 

分 类 号：S220[农业科学—农业机械化工程] TU413.4[农业科学—农业工程]