Investigation of the dynamic characteristics of a dual rotor system and its start-up simulation based on finite element method

Recently,the finite element method(FEM) has been commonly applied in the engineering analysis of rotor dynamics.Gyroscopic moments,rotary inertia,transverse shear deformation and gravity can be included in computational models of rotor-bearing systems.In this paper,a finite element model and its solution method are presented for the calculation of the dynamics of dual rotor systems.A typical structure with two rotor shafts is discussed and the procedure for obtaining the coupling motion equations of the subsystems is illustrated.A computer program is developed to solve critical speeds and to simulate the transient motion.The influence of gyroscopic moments on co-rotation and counter-rotation is analyzed,and the effect of the speed ratio on critical speed is studied.The dynamic characteristics under different conditions of increasing speed during start-up are demonstrated by comparison with transient nodal displacements.The presented model provides a complete foundation for further investigation of the dynamics of dual rotor systems.

A Robust Face Recognition Method Combining LBP with Multi-mirror Symmetry for Images with Various Face Interferences

Face recognition(FR) is a practical application of pattern recognition(PR) and remains a compelling topic in the study of computer vision. However, in real-world FR systems, interferences in images, including illumination condition, occlusion, facial expression and pose variation, make the recognition task challenging. This study explored the impact of those interferences on FR performance and attempted to alleviate it by taking face symmetry into account. A novel and robust FR method was proposed by combining multi-mirror symmetry with local binary pattern(LBP), namely multi-mirror local binary pattern(MMLBP). To enhance FR performance with various interferences, the MMLBP can 1) adaptively compensate lighting under heterogeneous lighting conditions, and 2) generate extracted image features that are much closer to those under well-controlled conditions(i.e., frontal facial images without expression). Therefore, in contrast with the later variations of LBP, the symmetrical singular value decomposition representation(SSVDR) algorithm utilizing the facial symmetry and a state-of-art non-LBP method, the MMLBP method is shown to successfully handle various image interferences that are common in FR applications without preprocessing operation and a large number of training images. The proposed method was validated with four public data sets. According to our analysis, the MMLBP method was demonstrated to achieve robust performance regardless of image interferences.

基于泵阀协控电液系统的工程机械节能技术综述

随着全球经济的飞速发展和工程机械全球保有量的持续上升,工程机械的节能问题变得越来越突出。液压系统是工程机械的关键子系统,因此提高其能源利用率是当前实现工程机械节能的重要手段之一。而在传统的阀控或泵控液压系统中,由于受阀件和液压泵的固有特性制约,系统可控性和节能性通常无法得到兼顾。泵阀协控系统将泵控系统的节能特性与阀控系统的高精度和高频率响应相结合,使其成为当前电液系统的一个研究热点。本文总结了泵阀协控电液系统节能技术的最新研究进展,并重点分析了不同类型工程机械的液压系统结构、电动液压系统的控制方法、新型液压混合能量再生系统以及关键部件。同时,从负载口独立控制技术、共压导轨技术(CPR)和混合动力源系统三个方面探讨了泵阀协控系统的未来发展方向和面临的挑战。

离心泵内部流动结构、性能优化与故障检测综述

目的:对离心泵的内部流动机理和外部特性、振动监测和性能优化进行研究,并对新兴研究趋势进行评述,为提高离心泵系统的能效提供参考建议。创新点:1.探讨了最新的用于离心泵数值模拟的湍流模型和空化模型的研究成果以及利用可视化方法揭示离心泵内部复杂流动现象的最新进展。2.对离心泵的外部特性、空化和振动进行了广泛的讨论,并总结出一种提高离心泵在工程应用中的效率和扬程、降低汽蚀余量的适用性强的离心泵叶轮多目标优化方法。方法:1.对离心泵的内部流动机理进行综述,以充分了解离心泵内部复杂的流场结构和能量损失机理。2.对离心泵外部特性进行研究,解释内部非定常流动与外部特性的耦合关系。3.介绍与离心泵在运行过程中压力脉动的监测和测量相关的最新研究进展。4.详细介绍优化离心泵性能的各种方法和措施。结论:1.尽管对离心泵内部流动现象机理及流场结构的研究已经取得了一定进展,但研究中仍存在一些亟待解决的问题,如初生空化的监测与预防、泵内旋转失速现象发生发展的规律、数值模拟和实验之间不可忽视的数据差异等。2.针对这些问题,开发高精度的计算流体动力学仿真模型,结合关键过流部件的优化设计来减少流动不稳定性和提高性能,以及运用现代流动显示技术的最新设备进行大量的仔细繁杂的试验与测量工作,是非常必要和重要的,也是未来泵内流动研究的趋势。

Development of electric construction machinery in China:a review of key technologies and future directions

The issues of energy shortage and environmental pollution have accelerated the electrification of construction ma-chinery(CM)industry globally.In China,the amount of electric construction machinery(ECM)has been growing across the industry.The sales of ECM are estimated to reach 600000 vehicles by the end of 2025,while the total demand for battery power will reach 60 GWh.However,the development of ECM still faces critical challenges including reliable power supply and energy distribution among various components.In this review,we primarily focus on important technological breakthroughs and the difficulties faced by the CM industry in China.An overview of ECM including classification and characteristics is given at the beginning.Next,the selection of key components such as the electric motor and the energy storage units,and the control strategy in the pure electric drive system are discussed.The characteristics of the hybrid electric drive system such as structure design and power matching are analyzed in detail.The battery management system(BMS)is critical to ensure appropriate battery health for reliable power supply.Here,we extensively review technical developments in various BMSs.In addition,we roughly estimate the national total of CM emissions and the potential environmental benefits of employing ECMs in China.Finally,we set out future research directions and industrial development of ECM.