Tool Condition Monitoring Based on Nonlinear Output Frequency Response Functions and Multivariate Control Chart

Tool condition monitoring(TCM)is a key technology for intelligent manufacturing.The objective is to monitor the tool operation status and detect tool breakage so that the tool can be changed in time to avoid significant damage to workpieces and reduce manufacturing costs.Recently,an innovative TCM approach based on sensor data modelling and model frequency analysis has been proposed.Different from traditional signal feature-based monitoring,the data from sensors are utilized to build a dynamic process model.Then,the nonlinear output frequency response functions,a concept which extends the linear system frequency response function to the nonlinear case,over the frequency range of the tooth passing frequency of the machining process are extracted to reveal tool health conditions.In order to extend the novel sensor data modelling and model frequency analysis to unsupervised condition monitoring of cutting tools,in the present study,a multivariate control chart is proposed for TCM based on the frequency domain properties of machining processes derived from the innovative sensor data modelling and model frequency analysis.The feature dimension is reduced by principal component analysis first.Then the moving average strategy is exploited to generate monitoring variables and overcome the effects of noises.The milling experiments of titanium alloys are conducted to verify the effectiveness of the proposed approach in detecting excessive flank wear of solid carbide end mills.The results demonstrate the advantages of the new approach over conventional TCM techniques and its potential in industrial applications.

An Ultra-Low Quiescent Current CMOS Low-Dropout Regulator with Small Output Voltage Variations

An ultra-low quiescent current low-dropout regulator with small output voltage variations and improved load regulation is presented in this paper. It makes use of dynamically-biased shunt feedback as the buffer stage and the LDO regulator can be stable for all load conditions. The proposed structure also employs a momentarily current-boosting circuit to reduce the output voltage to the normal value when output is switched from full load to no load. The whole circuit is designed in a 0.18 μm CMOS technology with a quiescent current of 550 nA. The maximum output voltage variation is less than 20 mV when used with 1 μF external capacitor.

Storability of “Jonagold” Apple Fruit under Extreme Controlled Atmosphere Conditions

In two consecutive seasons, the storage capacity of “Jonagold” apple fruit was investigated under regular air (RA) and various controlled atmosphere (CA) conditions during six months at 0 ± 0.3 °C. The different CA treatment combinations were: (1) 0.5 kPa O2 + 0.5 kPa CO2, (2) 2.0 kPa O2 + 1.0 kPa CO2, (3) 1.0 kPa O2 + 3.0 kPa CO2 and (4) 0.5 kPa O2 + 6.0 kPa CO2. Ethylene production and respiration rate were evaluated at each two months storage intervals during 7 d shelf life at 20 °C. Fruit quality traits were analyzed immediately at the end of storage period and after 7 d shelf life at 20 °C. Under CA treatment, the lower the O2 and/or the higher the CO2 partial pressure, the stronger was the inhibition of the ethylene production and respiration rate of apple fruit. The 0.5 kPa O2 + 6.0 kPa CO2 CA condition induced the strongest suppression in ethylene production and consequently lower CO2 release by apple fruit. At the end of storage period, “Jonagold” apple fruit was very tolerant to all CA conditions, and any kind of internal storage disorders was observed. The storage of “Jonagold” apple at 1.0 kPa O2 + 3.0 kPa CO2 and 0.5 kPa O2 + 6.0 kPa CO2 proportionated higher flesh firmness (FF), greener skin color (SC) and higher titratable acidity (TA) either immediately after storage or after 7 d shelf life at 20 °C. Total soluble solids were not significantly affected by CA storage conditions.

Exact Time Domain Solutions of 1-D Transient Dynamic Piezoelectric Problems with Nonlinear Damper Boundary Conditions

Novel exact solutions of one-dimensional transient dynamic piezoelectric problems for thickness polarized layers and disks, or length polarized rods, are obtained. The solutions are derived using a time-domain Green’s function method that leads to an exact analytical recursive procedure which is applicable for a wide variety of boundary conditions including nonlinear cases. A nonlinear damper boundary condition is considered in more detail. The corresponding nonlinear relationship between stresses and velocities at a current time moment is used in the recursive procedure. In addition to the exact recursive procedure that is effective for calculations, some new practically important explicit exact solutions are presented. Several examples of the time behavior of the output electric potential difference are given to illustrate the effectiveness of the proposed exact approach.

基于多目标回归的空调负荷预测方法

针对空调为二次泵变流量系统时,考虑分区域供冷工况下,采用多目标回归方式解决负荷预测问题将有利于提高负荷预测准确性的情况,提出了两种多目标回归的中央空调负荷预测模型,即多目标支持向量回归(support vector regression,SVR)负荷预测模型和多目标长短期记忆(long short term memory,LSTM)神经网络负荷预测模型,利用上海市某医院的二次泵变流量系统数据对两个模型进行训练和预测,并与单目标回归预测模型进行比较.研究结果表明:相较单目标回归预测模型,两种多目标预测模型的预测精度更高;多目标SVR负荷预测模型较多目标LSTM负荷预测模型的预测准确性更高.

空间高温区自由活塞斯特林发电机工作特性试验研究

测试了不同冷端温度下,外负载、运行压力和加热功率对高温区自由活塞斯特林发电机的热端温度、电电效率、输出功率、频率的影响。研究结果表明,在同一冷端温度时,加热功率的增加使发电机的电电效率、输出功率、热端温度上升,而外负载、运行压力的增加则起相反作用;发电机的频率与外负载呈负相关变化,与运行压力、加热功率呈正相关变化。提升冷端温度使发电机的输出功率、电电效率和频率下降,热端温度上升。在三种不同冷端温度下,外负载、加热功率和运行压力对发电机输出特性的影响规律不变。经过测试,发电机在运行温区为495~1058 K时,最大输出功率103.681 W,电电效率20.5%。

柔性直流输电用干式直流电容器工况验证试验回路研制

干式直流电容器作为柔性直流输电换流阀的核心组件,尚未开展阀组级工况试验验证。通过对目前实验室条件下换流阀组件运行情况的调研,确定采用被试阀段与陪试阀段对拖运行的拓扑,以满足验证试验回路构建的要求。通过仿真分析和系统试验,证明在满足经济性和实用性要求下,正常工作时回路各阀段至少需要5个子模块串联。考虑到该试验回路需要针对不同型号规格的电容器开展运行试验,叠层母排采用了特殊的设计,方便参数测量和电容器更换。

带有非线性边界和扰动输入的波动方程的输出反馈控制

无穷维系统的输出反馈控制是控制理论中重要的研究课题,相对于线性边界输入而言,非线性边界条件更多应用于实际的数学模型中,容易引起各种不同的动力学行为,如混沌声振动、倍周期分岔、方波等.本文研究了左端具有非线性位移边界条件,右端带有总扰动输入的一维波动方程的输出反馈镇定问题.首先,利用算子半群理论证明了开环系统的适定性;其次,由于内部非线性项和外部扰动的存在,通过构造无穷维扰动估计器,证明了该估计器能够实时在线估计总扰动;紧接着,借助于原系统的量测输出信号设计状态观测器,构造输出反馈控制器并得到了闭环系统;最后,证明了该闭环系统的适定性和渐近稳定性.

京唐3号高炉原燃料质量劣化下的提产创效措施

对京唐3号高炉原燃料质量劣化下的提产创效措施进行了总结。2021年7月,由于焦煤和秘鲁球团矿粉资源紧缺,原燃料质量劣化,3号高炉炉况稳定性减弱,炉墙水温差波动增大,铁水[Si]含量呈下降趋势。通过采取改善原燃料质量、优化装料制度、改善送风制度、稳定铁水[Si]、强化出铁管理等措施,尤其是装料制度坚持“打开中心、稳定边沿,稳定中心、照顾边沿”原则,炉况稳定性明显增强,日产量逐步提高。2022年4月,3号高炉焦比283.9kg/t,燃料比494.8kg/t,日产量12963Vd;5月,焦炭负荷达到6.01,利用系数达到2.40V(m^(3)·d)以上。

TOE框架下我国省域农业碳排放影响因素组态分析——NCA与fsQCA方法相结合

发展低碳农业是实现农业可持续发展的必然要求,而探索农业碳排放影响因素的联动效应是发展低碳农业的必经之路。为厘清我国省域农业碳排放影响因素的复杂因果关系,本研究基于“技术—组织—环境”(TOE)框架构建了我国省域农业碳排放影响因素的理论框架,采用投入产出模型核算2017年我国30个省(自治区、直辖市,不包括中国香港、中国澳门、中国台湾和西藏)农业碳排放总量,并将必要条件分析(NCA)与模糊集定性比较分析(fsQCA)相结合对2017年我国各省农业碳排放的影响因素展开组态分析。结果表明:1)单个因素并不是实现农业低碳排放的必要条件,只有技术、组织和环境三方因素相互促进才能实现农业低碳排放;2)驱动农业低碳排放的影响路径可总结为3条:机械主导型、机械-结构协同型与结构-环境协同型,由此可见,各省农业低碳发展呈多元化驱动路径;3)导致农业非低碳排放的影响路径可总结为两条:机械-结构缺失型和机械-环境缺失型。综合农业低碳排放和非低碳排放的影响路径来看,农业机械化、农业产业结构合理化和环境规制是影响农业碳排放的关键因素,若对其充分利用或持续优化,一定会对发展低碳农业起到至关重要的作用。本研究扩充了TOE框架的使用领域,研究结论为我国各省发展低碳农业提供了多元化的驱动路径。

考虑碳捕集-热电联产灵活运行和绿证-碳融合机制的综合能源系统低碳调度

针对传统能源系统灵活性差、新能源消纳困难的问题,提出一种计及碳捕集-热电联产灵活运行和绿证-碳融合的综合能源系统(integrated energy system,IES)低碳调度模型.首先,引入储液罐对传统碳捕集电厂(carbon capture power plant,CCPP)的灵活性不足进行改造,并构建出CCPP综合灵活运行模型;同时,考虑到传统热电联产(combined heat and power,CHP)机组存在“以热定电”、“以电定热”限制,在CHP机组中引入卡琳娜循环和电锅炉,解耦CHP固定热电比,以改进CHP灵活输出模型.然后,将改进后的CHP与CCPP灵活模型相结合,构建CCPP-CHP联合灵活运行模型.最后,在IES中引入绿证和碳交易机制,通过研究这两种机制的关联性,并顾及系统的不确定性影响,提出了计及绿证-碳融合交易及条件风险价值理论(CVaR)的IES低碳优化模型.在算例仿真中,设置不同的场景进行对比分析,验证了所提模型在提升系统经济性和低碳性方面的有效性.

产能产量双控背景下方大特钢财务分析启示

基于产能产量双控、绿色低碳转型和产业集中度提升的大背景下,针对方大特钢资本结构与偿债能力、营运能力、盈利能力等方面对其近10年的财务状况、生产经营状况、发展历程进行了分析,最后基于方大特钢的财务分析,对钢铁行业未来如何更好实现高质量发展,提出了可供其他钢铁企业参考的启示和建议。

车载定位设备状态修模式在杭州地铁1号线的实践

基于车载定位设备在列车运行控制中的重要地位,杭州地铁1号线在业内率先对其制定状态修策略,具体为在日常检修时测试若干项关键指标,对设备状态进行评价和分级,对应不同结果采取更有效的针对性解决措施。经实际应用证明,此举可有效提升设备运行表现,提高设备的整体寿命,兼顾维修效果和维修成本,可为其他采用类似车载定位设备的地铁线路运维带来启发和参考。

极端天气下基于时间卷积神经网络的新能源出力评估策略

新能源高渗透率背景下,极端天气造成的出力骤降对电力系统安全运行构成严重挑战,准确评估极端天气下的新能源出力深度是制定电力系统运行方式的重要依据。本文提出一种基于改进的深度时间卷积神经网络(deep temporal convolutional network,DeepTCN)的新能源出力评估方法。通过设计具有动态输入权重的时间卷积神经网络架构,准确量化估计了极端天气对新能源出力的影响,从而为制定极端天气下的电力系统运行方式提供风险程度信息。基于实际电力系统新能源出力数据集的算例结果表明,与常规的时序预测方法相比,所提方法的标准化均方根误差、对称平均绝对百分比误差和平均绝对标度误差3个指标分别最高可提升1.2,0.1和0.22。所提方法能够实现对极端天气下新能源出力的更精准评估。

Robust decentralized adaptive output feedback fuzzy controller design and application to AHS

A novel decentralized indirect adaptive output feedback fuzzy controller is developed for a class of large-scale uncertain nonlinear systems using error filtering.By the properly filtering of the observation error dynamics,the strictly positive-real condition is guaranteed to hold such that the proposed output feedback and adaptation mechanisms are practicable in practice owing to the fact that its implementation does not require the observation error vector itself any more,which corrects the impracticable schemes in the previous literature involved.The presented control algorithm can ensure that all the signals of the closed-loop large-scale system keep uniformly ultimately bounded and that the tracking error converges to zero asymptotically.The decentralized output feedback fuzzy controller can be applied to address the longitudinal control problem of a string of vehicles within an automated highway system（AHS） and the effectiveness of the design procedure is supported by simulation results.

Output neighboring-extremal and NCO tracking control in the optimal operation of CSTR

A new optimizing framework of process operation is proposed to deal with optimizing op- eration of continuous stirred tank reactor （CSTR）. The optimization framework includes two layers： the first layer, necessary condition of optimally （NCO） tracking controller, calculates the optimal set-point of the process; and the second layer, output neighboring-extremal controller, calculates the input values of the controlled plant. The algorithm design and convergent analysis of output neighboring-extremal controller are discussed emphatically, and in the case of existing parametric uncertainty, the approach is shown to converge to the optimum atmost in two iterations. At last the approach is illustrated by simulation results for a dynamic CSTR.

计及风电出力相关性和条件价值风险的电力系统概率可用输电能力评估

针对风电出力预测误差对区域间可用输电能力(ATC)评估的影响,提出一种计及风电出力相关性和条件风险价值(CVaR)的电力系统区域间ATC概率评估方法。首先,通过基于历史风电出力数据的相关系数矩阵和Copula函数,构建计及风电场出力空间相关性的风电出力预测误差概率模型;接着,基于获得的计及风电出力空间相关性的风电出力预测误差修正风电场出力预测值;然后,提出一种计及风电出力相关性和CVaR的ATC概率评估双层优化模型,下层模型以基态下发电成本和风险费用最小为目标,上层模型以极大化区域间ATC为目标,通过基态下和极限状态下机组的出力作为上下层模型间的交互信息;在此基础上,利用Karush-Kuhn-Tucker(KKT)最优条件,对下层模型进行转换,将双层优化模型转换为均衡约束的数学规划(MPEC)模型;进一步,将MPEC模型转换为混合整数二阶锥规划问题,进而实现概率ATC的求解;最后,通过PJM-5节点测试系统和吉林西部电网进行算例分析,结果验证了所提方法的可行性和有效性。

低压缸零出力条件下电锅炉和高低旁路抽汽供热的经济性与灵活性分析

供热机组灵活性改造是打破“热电耦合”、实现煤电机组为可再生能源发电提供容量支撑的有效措施,最常见的技术方案是汽轮机低压缸零出力运行加高低旁路抽汽供热或电锅炉供热。针对一350 MW超临界供热机组,采用变工况迭代计算方法,对两种方案的最小电出力、最大供热和保热调电典型工况点的热经济性,以及深调峰负荷段的电出力的可调范围进行对比分析。结果表明,由于冷端损失很小,在相同热电负荷工况下电锅炉方案耗煤量仅略大于高低旁路抽汽方案;而因电锅炉具有优良的逆向电负荷调节能力,深调峰负荷段下的电负荷可调区间要显著大于高低旁路抽汽方案。

计及预测误差时空-条件相依特性的日内光伏出力区间预测方法

由于光伏出力预测误差无法避免,区间预测可以更准确地描述光伏的不确定性,从而对电力系统的决策提供指导,而现有研究方法不能够充分地挖掘光伏功率的物理变化过程,因此提出了一种考虑预测误差时空-条件相依特性的日内光伏出力区间预测框架。首先通过外观相似性更新(appearance similarity update,ASU)模型得到考虑时间相依性的预测误差,再通过长短期记忆(long short-term memory,LSTM)网络模型以及空间相关性的分析得到考虑空间相依性的预测误差,并对预测的出力进行修正,最后依据其误差的条件相依性得到不同置信度下的区间预测。整体框架的效果在新疆光伏电场被验证,其均方根误差能够降低3%以上,同时考虑更新后的预测误差时空-条件相依性的区间预测效果有所提升,验证了所提方法的有效性和可行性。

供热机组低压缸零出力工况下热经济性分析

低压缸零出力运行是当前供热机组灵活性改造的主要方式。依据电网现行深调峰补偿政策,核算机组不同工况下的收益是现场面临的实际问题。研究一种基于热平衡规律的变工况快速算法,能够在保证基本计算准确度的情况下快速计算出机组变工况后运行状态。以某350 MW超临界供热机组为例,分别计算100%TMHCR(最大供热)和40%THA工况下低压缸零出力运行前后的发电功率、供热功率及热耗等参数,进而计算出发电供热收益。结果显示,100%TMHCR工况低压缸零出力运行能够降低发电负荷约8%,提升供热负荷27%,40%THA工况可将发电负荷降低至25%Pe,经济效益显著。