Fault diagnosis for wind turbine based on improved extreme learning machine

A fault diagnosis method based on improved extreme learning machine (IELM) is proposed to solve the weakness (weak generalization ability, low diagnostic rate) of traditional fault diagnosis with feedforward neural network algorithm. This method fuses signal feature vectors, extracts six parameters as the principal component analysis (PCA) variables, and calculates correlation coefficient matrix among the variables. The weight values of control parameters in the extreme learning model are dynamically adjusted according to the test samples’ constantly changing. Consequently, the weight fixed drawback in the original model can be remedied. A fault simulation experiment platform for wind turbine drive system is built, eight kinds of fault modes are diagnosed by the improved extreme learning model, and the result is compared with that of other machine learning methods. The experiment indicates that the method can enhance the accuracy and generalization ability of diagnosis, and increase the computing speed. It is convenient for engineering application.     

层次分析法在物流企业仓库选址中的运用

物流市场竞争的加剧要求企业经营者不断提高物流服务质量以加强企业竞争力。仓库选址作为物流企业提高物流服务质量的战略决策，需要企业决策者综合考虑地理条件、顾客、管理等因素后迅速作出判断。这是一项复杂的任务。层次分析法（AHP）是一种利用专家经验将定性的综合判断转化为具体的定量判定的方法。运用AHP，可以对物流企业的仓库选点和战略决策提供比建立数学模型更方便可行的分析方法。     

Opportunistic preventive maintenance optimization for multi-unit series systems with combing multi-preventive maintenance techniques

This paper proposes a dynamic opportunistic preventive maintenance (PM) optimization policy for multi-unit series systems by integrating multi PM techniques. Two PM techniques, periodic PM and sequential PM, are considered. Whenever one of the units reaches its reliability threshold, a PM action has to be performed on that unit. At that time the whole system has to be stopped and PM opportunities arise for the other units of the system. An optimal PM practice is determined by maximizing the short-term cumulative opportunistic maintenance (OM) cost savings for the whole system. Numerical examples are given to show how this approach works. Finally, a comparison between the proposed PM policy and the other policies is given.     

DFMA在汽车工业中的应用

本文介绍了制造，装配的设计（ＤＦＭＡ，ＤｅｓｉｇｎｆｏｒＭａｎｕｆａｃｔｕｒｉｎｇａｎｄＡｓｓｅｍｂｌｙ）的基本原理，讨论了基于并行工程的ＤＦＭＡ在汽车工业中的重要意义和实施方法。