为了准确辨识进给系统摩擦特性,提高数控机床加工精度,论文以Stribeck摩擦模型作为辨识对象,针对传统的摩擦辨识方法存在的问题,提出了在分析加速运动过程反馈信号的基础上再进行匀速测试的辨识方法。基于该方法进行实验,并使用EMD(Empirical Model Decomposition)方法和最小二乘法对实验数据分析后得到了摩擦模型的参数;实验结果表明文中提出的方法与传统的摩擦模型辨识方法对比,具有操作简单、节省实验时间和辨识准确的特点。
The method of acquiring the real-time data has influenced the implementation of the manufacturing execution system (MES). Accompanied with turning the MES into service-oriented manufacturing execution system (so-MES), real-time e-quality tracking (e-QT), in which real-time data are computed, has played more and more important roles in manufacturing. This paper presents an e-QT model through the study of real-time status data tracking and quality data collecting. An implementing architecture of the e-QT model is constructed on the basis of radio frequency identification devices (RFID) data-tracking network. In order to develop the e-QT system, some key enabling technologies, such as configuration, data collection, and data processing, etc, are studied. The relation schema between hardware is built for the RFID data-tracking network based on the configuration technique. Real-time data are sampled by using data collecting technique. Furthermore, real-time status and quality data in a shop-floor can be acquired in terms of using the real-time data computing method. Finally, a prototype system is developed and a running example is given so as to verify the feasibility of methods proposed in this paper. The proposed research provides effective e-quality tracking theoretical foundation through the use of RFID technology for the discrete manufacturing.
Local flexibility of crack plays an important role in crack identification of structures.Analytical methods on local flexibility in a cracked beam with simple geometric crossing sections,such as rectangle,circle,have been made,but there are some difficulties in calculating local flexibility in a cracked beam with complex crossing section,such as pipe and I-beam.In this paper,an analytical method to calculate the local flexibility and rotational spring stiffness due to crack in I-beam is proposed.The local flexibility with respect to various crack depths can be calculated by dividing a cracked I-beam into a series of thin rectangles.The forward and inverse problems in crack detection of I-beam are studied.The forward problem comprises the construction of crack model exclusively for crack section and the construction of a numerically I-beam model to gain crack detection database.The inverse problem consists of the measurement of modal parameters and the detection of crack parameters.Two experiments including measurement of rotational spring stiffness and prediction of cracks in I-beam are conducted.Experimental results based on the current methods indicate that relative error of crack location is less than 3%,while the error of crack depth identification is less than 6%.Crack identification of I-beam is expected to contribute to the development of automated crack detection techniques for railway lines and building skeletons.
LI Bing*,CHEN Xuefeng,and HE Zhengjia State Key Laboratory for Manufacturing System,Xi’an Jiaotong University,Xi’an 710072,China Received April 7,2010
