Sensor fault identification based on time-lagged PCA in dynamic processes

Principal component analysis (PCA) is widely employed as a multivariate statistical method for fault detection, isolation and diagnosis in chemical processes. Previously, PCA has been successfully used to identify faulty sensors under normal static operating conditions. In this paper, we extend the reconstruction-based sensor fault isolation method proposed by Dunia et al. to dynamic processes. We develop a new method for identifying and isolating sensor faults in an inherent dynamic system. First, we describe how to reconstruct noisy or faulty measurements in dynamic processes. The reconstructed measurements are obtained by simple iterative optimization based on the correlation structure of the time-lagged data set. Then, based on the sensor validity index (SVI) approach developed by Dunia et al., we propose an SVI for fault isolation in dynamic processes. The proposed method was applied to sensor fault isolation in two strongly dynamic systems: a simulated 4×4 dynamic process and a simulated wastewater treatment process (WWTP). In these experiments, the proposed sensor fault identification method correctly and rapidly identified the faulty sensor; in contrast, the traditional PCA-based sensor fault isolation approach showed unsatisfactory results when applied to the same systems.     

Monitoring kidney-transplant patients using metabolomics and dynamic modeling

A kidney transplant provides the only hope for a normal life for patients with end-stage renal disease, i.e., kidney failure. Unfortunately, the lack of available organs leaves some patients on the waiting list for years. In addition, the post-transplant treatment is extremely important for the final outcome of the surgery, since immune responses, drug toxicity and other complications pose a real and present threat to the patient. In this article, we describe a novel strategy for monitoring kidney transplanted patients for immune responses and adverse drug effects in their early recovery. Nineteen patients were followed for two weeks after renal transplantation, two of them experienced problems related to kidney function, both of whom were correctly identified by means of nuclear magnetic resonance spectroscopic analysis of urine samples and multivariate data analysis.     

Monitoring multistage processes with autocorrelated observations

In multistage manufacturing processes, autocorrelations within stages over time are prevalent and the classical control charts are often ineffective in monitoring such processes. In this paper, we derive a linear state space model of an autocorrelated multistage process as a vector autoregressive process, and construct novel multivariate control charts, CBAM and Conditional-based MEWMA, for detecting the mean changes in a multistage process based on a projection scheme by incorporating in-control stage information. When in-control stages are unknown, finding in-control stages is a challenging issue due to the autocorrelations over time and the sequential correlations between stages. To overcome this difficulty, we propose a conditional-based selection that chooses stages with strong evidences of in-control stage using the cascading property of multistage processes. The information of selected stages is effectively utilised in obtaining powerful test statistics for detecting a mean change. The performance of the proposed charts is compared with other existing procedures under different scenarios. Both simulation studies and a real example show the effectiveness of the conditional-based charts in detecting a wide range of small mean shifts compared with the other existing control charts.     

Interaction of dynamic mode-I cracks with inclined interfaces

In this paper, we report on an experimental study of the deflection/penetration behavior of dynamic mode-I cracks propagating at two different crack velocities (slower and faster) toward inclined weak interfaces of three dissimilar angles (α): 30°, 45° and 60°. A simple wedge-loading specimen configuration as proposed by Xu et al. [Xu LR, Huang YY, Rosakis AJ. Dynamic crack deflection and penetration at interface in homogenous materials: experimental studies and model predictions. J Mech Phys Solids 2003;51:461-86], made of brittle Homalite-100, is used. A modified Hopkinson bar setup is used to achieve well-controlled impact loading conditions. Dynamic photoelasticity in conjunction with high-speed photography is used to capture real-time isochromatics associated with deflected/penetrated cracks.     

Process monitoring and configural display design: A neuroimaging study

In this paper an investigation is reported of neural imaging of the electrocortical activity involved when users monitored dynamic visual interfaces for process failures. For six different visual displays, the form of the display and the directness of mapping between process parameters and visual form were varied. Performance data showed best results with a configural display that mapped the process parameter most important for failure detection to a simple visual property of the display geometry. In this display condition, performance variability was lowest of all conditions and self-reports of users' monitoring strategy revealed the least variability among users. Neuroimaging results for this display condition revealed that changes in electrocortical activity were most consistent between subjects compared with other displays, while still remaining small in absolute terms. These results are interpreted in the light of previous findings in ecological psychology and control of dynamic systems and implications for their use in dynamic visual display design are outlined.     

Investigation of an FFT-based solver applied to dynamic flowsheet simulation of agglomeration processes

The growth of particles due to agglomeration is often mathematically described by population balance equations. The numerical evaluation of these equations and applying new methods to their solution is an area of increasing interest. In this contribution, a new approach for solving the agglomeration population balance model based on a separable approximation of the agglomeration kernel and a fast Fourier transformation is investigated. Its applicability within a dynamic flowsheet simulation of continuous agglomeration processes with complex structures is analysed. A simulation framework Dyssol is used to study the new method and compare it to the well-known fixed pivot technique. Studies have shown that the new approach can provide a more efficient solution if certain constraints on the number of classes and on the separation rank of the agglomeration kernel are met.     

Decentralized supply chain coordination through auction markets: dynamic lot-sizing in distribution networks

As supply chains become bigger and dynamically structured involving multiple organizations with different interests, it is impossible for a single organization to control a whole supply chain. So, decentralization of decision rights is an inevitable facet of managing modern supply chains. However, controlling in a decentralized mode can fail without appropriate coordination mechanisms. When the agents of a supply chain are not willing to cooperate in terms of information sharing, the whole supply chain can exhibit expensive inefficiencies such as the bullwhip effect. In this paper, we design a trustworthy decentralized coordination mechanism for dynamic lot-sizing in distribution networks, as an effort to motivate information sharing. We design multiple auctions and each auction coordinates the plans of a supplier and its customers by trading the right of managing the supplier's inventory plan. The coordination mechanism makes a reasonable profit and the profit is divided in an agreeable way. Also, the profits are actual because of the capability of supporting a truth-telling environment. Therefore, the designed coordination mechanism is trustworthy in that it guarantees the right benefits to all the agents in return for information sharing.     

基于区域相关的动态匹配方法

介绍了一种应用动态规划技术的图像匹配方法。该方法以区域相关为基础,通过在相关系数平面上寻找最佳路径来实现图像匹配。采用了规定视差搜寻范围,盒滤波技术和顺序一致性设定路径走向等办法优化匹配策略,加快匹配速度。用 VC 编写的算法对图像对进行匹配时,能实现快速准确的匹配。     

Modified processes capability assessment with dynamic mean shift

Rapid advancements in manufacturing technology have seen electronic products becoming lighter and thinner. This has led to production yield requirements of sawing processes in the semiconductor industry becoming increasingly strict. For sawing processes requiring a very low fraction of defective, the process capability index C_pk is widely applied for production yield measurement under the assumption of process stability. However, in practice, even when the typical control charts are implemented, dynamic and unobserved natures of the actual process mean shift may occur. Since the trial control limits are established with reference to random samples, the associated performances are also with uncertainty because of sampling error. In this paper, we investigate the effects of parameter estimation error on the development of the phase I control chart and further compare three methods with various estimators for the process standard deviation. Then, we tabulate the modified adjustment magnitudes for the dynamic C_pk under various subgroup sizes and sample sizes. On the basis of the simulation results, the proposed method can avoid overestimating the true process capability and make more trustworthy decisions. Finally, for demonstration purposes, an application of process capability measures for a sawing process is presented.     

动态汽车衡动态称量过程中的若干问题及对策

从动态汽车衡的构成及工作原理出发，依据国家检定规程的相关规定，详细地分析了动态汽车衡在进行动态称量时，因称量对象运动冲击性和运行速度等因素而产生的若干问题的原因，揭示了动态称重的复杂性和可变性，并针对各项问题的原因提出了切实可行的应对策略。这些分析和对策，对具体从事动态汽车衡检定的专业技术人员及即将在全国全面开展的车辆计重收费工作具有一定的参考价值。     

Monitoring of zero-inflated Poisson processes with EWMA and DEWMA control charts

The zero-inflated Poisson (ZIP) distribution is an extension of the ordinary Poisson distribution and is used to model count data with an excessive number of zeros. In ZIP models, it is assumed that random shocks occur with probability p, and upon the occurrence of random shock, the number of nonconformities in a product follows the Poisson distribution with parameter λ. In this article, we study in more detail the exponentially weighted moving average control chart based on the ZIP distribution (regarded as ZIP-EWMA) and we also propose a double EWMA chart with an upper time-varying control limit to monitor ZIP processes (regarded as ZIP-DEWMA chart). The two charts are studied to detect upward shifts not only in each parameter individually but also in both parameters simultaneously. The steady-state performance and the performance with estimated parameters are also investigated. The performance of the two charts has been evaluated in terms of the average and standard deviation of the run length, and compared with Shewhart-type and CUSUM schemes for ZIP distribution, it is shown that the proposed chart is very effective especially in detecting shifts in p when λ remains in control (IC) and in both parameters simultaneously. Finally, one real example is given to display the application of the ZIP charts on practitioners.     

一种轮询周期受限的EPON双级动态带宽分配算法

提出一种新的EPON上行带宽分配算法——轮询周期受限的双级动态带宽分配算法。这种算法结合用户等级协定和DiffServ的特点,采用周期受限的轮询方法和双级的带宽分配方式,在OLT端根据ONUi提供的业务队列情况对业务量进行估算,并授权带宽给ONUi,ONUi根据实际的业务量进行再分配。仿真结果表明,这种算法实现了高的带宽利用率,与DBAM相比有效地提高了EPON的QoS。     

Characteristics of dynamic brittle fracture captured with peridynamics

Using a bond-based peridynamic model, we are able to reproduce various characteristics of dynamic brittle fracture observed in experiments; crack branching, crack-path instability, asymmetries of crack paths, successive branching, secondary cracking at right angles from existing crack surfaces, etc. We analyze the source of asymmetry in the crack path in numerical simulations with an isotropic material and symmetric coordinates about the pre-crack line. Asymmetries in the order of terms in computing the nodal forces lead to different round-off errors for symmetric nodes about the pre-crack line. This induces the observed slight asymmetries in the branched crack paths. A dramatically enhanced crack-path instability and asymmetry of the branching pattern are obtained when we use fracture energy values that change with the local damage. The peridynamic model used here captures well the experimentally observed successive branching events and secondary cracking. Secondary cracks form as a direct consequence of wave propagation and reflection from the boundaries.     

柔性制造系统检测监控系统的研究

根据柔性制造系统的实际需要，研制了一个ＦＭＳ运行状态检测监控系统，介绍了该系统的功能与结构，论述了系统与ＦＭＳ的集成方法，讨论了系统的工作流程及对ＦＭＳ故障的处理策略。     

FMES运行监视与故障诊断系统的研究与设计

以长春柔性制造实验系统为研究对象，研究了柔性制造系统的运行监视与故障诊断技术，研制了基于实时动画和人工智能的ＦＭＥＳ运行监视和故障诊断系统。介绍了ＦＭＥＳ－ＭＤＳ的总体结构讨论了ＦＭＥＳ－ＭＤＳ中的信息检测方法和故障诊断技术。     

Individual Observation Process Monitoring Charts for Systems with Response Lags

Previously, it has been held that statistical process control and engineering process control were two distinct domains for process improvement. However, we design four control policies to integrate the two approaches using a proportional-integral-derivative feedback controller and Shewhart or moving centerline exponentially weighted moving average charts. We specifically consider the impact of these policies for a system with response lags modeled by a second-order dynamic process and autocorrelated nonstationary outside disturbances. These policies are implemented using simulation and applied in a case study of a liquid tank system. Our investigation shows this approach is effective with respect to overall system performance, including quality and cost.     

上海轨道交通明珠线杂散电流防护与监测系统

详细介绍了在上海轨道交通明珠线上采取的 6项杂散电流防护措施和为该线路设计的杂散电流监测系统的组成、原理及对系统硬件和软件的要求 ,并给出了模拟试验的结果