基于平稳小波变换的悬臂梁微小缺陷检测方法研究

针对悬臂梁微小缺陷难以直接从模态振型进行有效识别的问题,提出了基于平稳小波变换的悬臂梁微小缺陷检测方法。通过利用有限元方法对悬臂梁进行建模和模态分析,得到了悬臂梁的模态参数。在此基础上,通过利用平稳小波变换对悬臂梁模态振型进行正交分解以得到平稳小波变换的近似系数(含模态振型的低频信号成份)和细节系数(含模态振型的高频信号成份)。最后,从平稳小波变换细节系数中提取了悬臂梁的微弱缺陷信息,实现了悬臂梁微小缺陷的有效定位和检测。从有限元模拟和平稳小波变换的结果可知,悬臂梁不同位置缺陷的前四阶细节系数都可以有效用于微小缺陷的定位。该方法具有较好的检测精度和可靠性,在结构缺陷萌生之初就可以有效识别缺陷的存在,避免结构灾难事故的发生,可推荐用于实际工程结构的检测。     

某车型怠速车身抖动的原因排查及解决方法

某款车型在开发过程中出现怠速车身抖动问题,抖动较为严重,主观感觉明显。通过对悬置系统隔振率、空调压缩机振动、风扇振动、排气振动、转向系统模态、整车车身模态等可能引起车身抖动原因的分析、排查,最后确定怠速车身抖动为悬置隔振性能差、整车车身模态和发动机二阶激励耦合引起。通过对悬置系统的隔振性能进行优化,以及调整空调开工况发动机怠速转速,解决了车身抖动问题。     

LED粘片机运动摆臂的优化设计与分析

LED粘片机在正常工作时,摆臂往往存在运动不平稳、振幅较大及趋稳时间较长等问题,影响粘片效率与精度。通过分析摆臂的整个运动过程,提出新的设计方法。首先,利用5次多项式运动曲线来替代梯形运动曲线,保证摆臂运动过程的平滑性;其次,结合静力学分析、模态分析及瞬态动力学分析,对摆臂进行外形优化设计;然后,为减少摆臂转动惯量对运动的影响,对摆臂进行拓扑优化,得到摆臂的优化模型;最后,通过瞬态动力学分析验证,证实了此方法的可行性。     

周转斜盘发动机模态分析及减振方案设计

针对周转斜盘发动机结构复杂,有限元模型规模大且分析效率较低等问题,引入子结构模态综合法用于发动机振动特性分析和减振设计。基于Ansys软件建立了发动机模态综合法分析模型,计算了发动机模态。分析了发动机振动激励源和振动传递路径,讨论了发动机结构减振措施,提出了发动机关键轴承处采用柔性支撑的减振方案,拟定了柔性支撑减振器可行结构形式。基于模态综合法计算模型,将减振器作为子结构建立采取减振措施的动力学分析模型。谐响分析表明:减振方案在低频段很好的效果。     

Low end‐to‐end delay fuzzy networking protocol for mobile wireless sensing

Because of the practical limitations of the energy and processing capabilities, the deployment of many Wireless Sensor Networks (WSN) is facing two main challenges of increasing network lifetime and reducing End to End Delay (EED) which become critical when the nodes are mobile and use non‐rechargeable energy sources. One way to help to extend network lifetime is using fuzzy logic in a form of artificial intelligence. To this end we propose a new routing protocol for using mobile WSNs, which holds the nodes in an equal level of energy and decreases energy dissipation of the network. An optimum path is selected based on the cost of each node to increase network lifetime. In order to lessen EED, we also attempt to design a novel zoning‐scheme for the network area. In this scheme, zonation is dynamic and works based on the Data Link (DL) position. The simulation result shows a significant improvement in lifetime and EED by proposed protocol compared with existing protocols. Copyright © 2016 John Wiley & Sons, Ltd.     

改进型1030 MW超临界机组高加撤出的保护探讨及优化

某改进型1030 MW机组在国内属首次创新应用,制造厂家认为当高加系统撤出后,由于通流的增加可能导致过负荷从而影响机组安全运行,原机组保护逻辑中规定了当高加撤出后若机组负荷大于1030 MW延时1 min,或大于1106 MW延时10 s后触发机组主保护。上述定值并未经过实际工程考验,为了提高机组运行的可靠性和安全性,在对保护逻辑进行确认和优化的基础上,安排了800 MW工况下的高加跳闸试验。试验后对相关数据进行了分析核算,进一步完善了相关控制逻辑和定值,确定了该机组高加撤出保护的实施方案。同时也对各型机组在高加跳闸工况下的危险点进行了分析总结。     

An Evaluation of Different Controllers Based on the Network Frequency Maintenance Strategy for a Large and Multi-control-area Interconnected Power System

Abstract—Maintaining the network frequency at its nominal value due to the load changes is one of the most important issues in the control and operation schedule of a large and multi-area interconnected power system. For the effective control solution, two types of tie-line bias control strategy-based controllers have been applied, i.e., classical and improved controllers. The classical controllers using conventional regulators, including integral, proportional–integral and proportional-integral-derivative, have achieved initial control results to bring the steady state back to the network. However, due to the very poor control features (e.g., large overshoots and long settling times), they need to be replaced with improved controllers, such as fuzzy logic and artificial neural network. To obtain an entire evaluation of the application of different load-frequency controllers, a five-control-area interconnected power system was built as a typical case study. Three improved controllers using proportional-plus-integral-based fuzzy logic and artificial neural network-based non-linear autoregressive moving average (NARMA-L2) architectures as well as their hybrid combination will also be investigated in this study. Simulation results obtained reveal that the improved controllers have obtained smaller overshoots (from 13.95 to 84.18%) and shorter settling times (from 19.91 to 65.71%) compared with the classical controllers.     

Fuzzy Logic-based Electrothermal Life Model for Inverter-fed Induction Motor Insulation

Pulse width modulated adjustable speed drives used in industries lead to significant advantages in terms of performance, size, and efficiency. But, the output voltage and the current waveforms become non-sinusoidal leading to an increase in voltage and thermal stresses. This results into accelerated insulation aging and premature failure of the motors. With multiple stresses, the life models for insulating materials become complex and ambiguous. This article presents the fuzzy logic application to derive an electrothermal life model to investigate the synergic effects of voltage and thermal stresses on intrinsic aging of inverter-fed induction motor insulation. Three parameters, viz. voltage stress factor, waveform slope stress factor, and spike frequency factor, are proposed to describe the insulation stresses for pulse width modulated voltages. These parameters are computed from the experimental results at different switching frequencies and are used in fuzzy logic-based life estimation algorithms. The results of the fuzzy logic life model are verified by performing the accelerated aging test with the same pulse width modulated voltages on paper insulation. An electrothermal life model is derived from the fuzzy logic results, which can be directly used for the life estimation of any general purpose low-voltage inverter-fed induction motor insulation.     

Hybrid Fuzzy-particle Swarm Optimization-simplex (F-PSO-S) Algorithm for Optimum Design of PM Drive Couplings

This paper aimed at exploring the use of the proposed hybrid Fuzzy-Particle Swarm Optimization-Simplex (F-PSO-S) algorithm to optimize the structural design of PM couplings subject to several key design constraints. The new proposed hybrid optimization algorithm is constructed based on combining three well-known techniques: fuzzy logic (FL), particle swarm optimization (PSO), and simplex method (SM). FL is used to aggregate different scaling and/or conflicting objectives in one objective function using fuzzy combination operators. On the other hand, the PSO has obvious capabilities in global search whereas the SM has exceptional advantages in local search. As a hybrid algorithm, the F-PSO-S has the outstanding feature of combining the ability of global searching and local canvassing for different scales and/or conflicting objective functions. The proposed algorithm has been applied to permanent magnet (PM) drive couplings. A standard coupling design is used as a good initial point for the conventional SM and to define the performance constraints for the proposed optimization technique. New coupling designs are developed and optimized to show the superior capabilities of the F-PSO-S algorithm as a global optimization technique. The sensitivity analysis is also performed to identify the effects of different design parameters on the coupling performance.     

变电站智能电子设备动态重构闭锁逻辑生成多代理系统

为保证变电站二次系统功能的完整和便于设备检修,智能电子设备(IED)动态重构技术逐渐得到关注。IED动态重构需要装载并解析IED配置描述(CID)文件,因管控主机保存的CID文件关联的是变电站设计时的系统结构,不能表征电力系统动态变化,为确保闭锁逻辑的正确性,需重新生成闭锁逻辑并更新相应的CID文件。利用多代理技术,管理动态重构管控主机、数据采集与监控(SCADA)主机、电力系统拓扑校验、变电站五防闭锁规则库生成软件等功能组件,构建多代理系统,完成电力系统拓扑校验和闭锁逻辑生成等任务的交互策略与协调流程,获得闭锁规则库更新CID文件,保证动态重构IED闭锁功能的正确性,能适应变电站的改造和升级,并提供更加灵活的闭锁规则管理。