Identification of Heffron-Phillips model parameters for synchronous generators operating in closed loop

Heffron-Phillips model of a synchronous machine is commonly used in small signal stability analysis and for off-line design of power system stabilisers. The data used to determine the parameters of this model are either hard to measure or require the machine to be taken off-line to take the measurements which, in general, is inconvenient. identifying these parameters from online data measurements is important since it does not require any a priori knowledge of the machine data. the problem of closed-loop identification of the Heffron-Phillips model parameters is of practical importance since the data used for identification can be gathered when the machine is normally connected to the power system. the use of open-loop identification techniques using data gathered during closed-loop operation of synchronous generators leads to bias errors in the estimated parameters. motivated by the fact that the synchronous machine model is multivariable and is well defined in a state space structure, a closed-loop subspace parameter identification technique is proposed. consistency of the proposed approach is illustrated using Monte Carlo analysis. comparison of the proposed method with open-loop identification technique shows the superiority of this approach.     

Dynamic models of closed-loop supply chain and robust H∞ control strategies

To meet the current environmental challenges and sustainable development, closed-loop supply chain (CLSC) management has become increasingly important and urgent. In this paper, we mainly consider three uncertainties: (1) uncertainty of time-delay in re-manufacturing and returns, (2) uncertainty of system cost parameters, (3) uncertainty of customers’ demand disturbances. Using control theories we dynamically analyse and establish a class of dynamic closed-loop supply chain models of linear discrete time system, including the product return model, the re-manufacturing model and the third party reverse logistic providers (3PRLP) collecting model. Furthermore, we analyse the robust operations in the closed-loop supply chains and bring forward relative strategies with robust H_∞ control methods. Finally, according to the practical operations of scrap supply chain in the Chinese steel industry, we carry out some simulation calculations to prove how our proposed robust H_∞ control strategies can restrain all uncertainties of our closed-loop supply chain system. Our analyses and results may be helpful for further insight into closed-loop supply chain uncertain operations and production control, for both theoretical researchers and practitioners, especially for those in the Chinese steel manufacturing industry.     

基于第三方的一类闭环供应链协调问题研究

在零售商负责产品销售、第三方负责废旧品回收情况下,研究了闭环供应链系统的利润模型.利用Stackelberg博弈理论,分析了分散决策情况下节点企业如何确定产品的批发价格、零售价格、废旧品回收价格和废旧品回收率.在传统的双方收入分享契约的基础上,将契约形式扩展到三方,提出了基于三方协调问题的收入-费用分享契约的协调机制,使包含三方的供应链系统得到了协调,并用具体算例验证了结论的正确性.     

考虑渠道权力结构和产品双重差异的再制造闭环供应链最优定价决策

针对具有不同渠道权力结构和回收拆解产品质量差异、新产品与再制造产品价格差异的再制造闭环供应链,主要研究其成员企业最优定价决策问题。构建了包含制造/再制造商、零售商、消费者和回收拆解商的三级再制造闭环供应链决策模型;采用Stackelberg主从博弈确定不同渠道权力结构下各成员企业的最优定价策略及其利润,并重点探讨废旧产品回收率τ、产品替代系数δ两个关键参数对它们的影响;将该决策模型应用到汽车发电机再制造闭环供应链案例。研究结果表明：1） 对于3种渠道权力结构,当制造/再制造商和零售商为主导者时,其自身利润和再制造闭环供应链总利润均最大;而当回收拆解商为主导者时,其自身利润和总利润却最小;2） 随着τ和δ的提高,单位新产品与再制造产品的最优批发价、最优零售价均增加,单位废旧产品的最优回收价则降低;制造/再制造商和零售商的利润下降,回收拆解商的利润上升,导致再制造闭环供应链的总利润呈U形。研究能够为各成员企业的最优定价决策提供有效支持与参考。     

Supplier selection and order allocation in closed-loop supply chain systems using hybrid Monte Carlo simulation and goal programming

Supplier selection is an important strategic design decision in closed-loop supply chain systems. In addition, and after identifying the candidate suppliers, optimal order allocations are also considered as crucial tactical decisions. This research presents a multi-objective optimisation model to select the best suppliers and configure manufacturing and refurbishing facilities with the optimal number of parts and products in a closed-loop supply chain network. The objective functions in this research are formulated as total profit, total defective parts, total late delivered parts and economic risk factors of the candidate suppliers. The proposed multi-objective model is solved by hybrid Monte Carlo simulation integrated with three different variants of goal programming method. The effectiveness of the mathematical model and the proposed solution algorithms in obtaining Pareto-optimal solutions is demonstrated in a numerical example adopted from a real case study.     

基于CVaR准则与ORP-RRP契约的闭环供应链决策模型

研究了基于预期订货量与实际回收量的回馈与惩罚ORP-RRP契约下的闭环供应链的协调问题。在CVaR准则下,提出了随机需求下单一风险厌恶型的零售商和单一风险中性的制造商组成的闭环供应链模型,探讨了供应链成员的决策行为、风险因子和废旧品回收敏感性系数;对废旧品回收价格和最优订货量的影响;研究结果表明：所建立的模型与ORP-RRP契约有效可行,可为供应链管理提供决策参考.     

An enhanced possibilistic programming approach for reliable closed-loop supply chain network design

Most of current logistics network design models in the literature typically assume that facilities are always available and absolutely reliable while in practice, they are always subject to several operational and disruption risks. This paper proposes a reliable closed-loop supply chain network design model, which accounts for both partial and complete facility disruptions as well as the uncertainty in the critical input data. The proposed model is of mixed integer possibilistic linear programming type that aims to minimise simultaneously the total cost of opening new facilities and the expected cost of disruption scenarios. An enhanced possibilistic programming approach is proposed to deal with the epistemic uncertainty in input data. Furthermore, the p-robustness criterion is used to limit the cost of disruption scenarios and protect the designed network against random facility disruptions. Several numerical experiments along with sensitivity analyses on uncertain parameters are conducted to illustrate the significance and applicability of the developed model as well as the effectiveness of the proposed solution approach. Our results demonstrate that operational and disruption risks considerably affect the whole structure of the designed network and they must be taken into account when designing a reliable closed-loop logistics network.     

变结构PID在微机械陀螺仪闭环驱动电路中的应用

为满足微机械陀螺仪(MMG)闭环驱动电路起振快速、无超调且稳态精度高等要求,提出了一种基于FPGA的数字化变结构PID控制器,并以其为核心构建了微机械陀螺仪的数字化闭环驱动电路.通过构造以控制误差为自变量的比例增益、积分增益和微分增益函数,使变结构PID的结构和参数能够根据瞬时误差的变化而变化,以提高闭环驱动电路的性能.针对某型微机械陀螺仪敏感结构参数,进行了SIMULINK仿真,仿真结果表明以变结构PID为核心的闭环驱动电路是可行的.起振实验结果表明,经典PID构成的闭环驱动电路,其检测电压的幅值超调量达到了75%,稳定时间为2 s;采用变结构PID控制器后闭环驱动检测电压的幅值无超调且稳定时间为0.7 s;1 h的稳定性实验表明,采用经典PID时检测电压幅值的长期稳定性为2.73×10-5V,采用变结构PID时其稳定性为2.68×10-5V,证明变结构PID可以兼顾系统在快速性、超调量和稳态精度等方面的要求.     

Robust closed-loop supply chain network design for perishable goods in agile manufacturing under uncertainty

In this study, a general comprehensive model is proposed for strategic closed-loop supply chain network design under interval data uncertainty. The proposed model considers various assumptions such as multiple periods, multiple products, and multiple supply chain echelons as well as uncertain demand and purchasing cost. In addition, bill of materials for each product is considered via a new approach in management of forward and reverse flows of products for producing new products and reusing or disassembling returned products. Uncertainty of parameters in the proposed model is handled via an interval robust optimisation technique. The model assumptions are well matched with decision making environments of food and high-tech electronics manufacturing industries. The factors that make these two industries similar are time-dependent properties of products such as prices and warehousing lifetime period. The computational results of solving the proposed model via LINGO 8 demonstrate efficiency of the proposed model in dealing with uncertainty in an agile manufacturing context.     

A three-stage model for closed-loop supply chain configuration under uncertainty

In this paper, a general closed-loop supply chain (CLSC) network is configured which consists of multiple customers, parts, products, suppliers, remanufacturing subcontractors, and refurbishing sites. We propose a three-stage model including evaluation, network configuration, and selection and order allocation. In the first stage, suppliers, remanufacturing subcontractors, and refurbishing sites are evaluated based on a new quality function deployment (QFD) model. The proposed QFD model determines the relationship between customer requirements, part requirements, and process requirements. In addition, the fuzzy sets theory is utilised to overcome the uncertainty in the decision-making process. In the second stage, the closed-loop supply chain network is configured by a stochastic mixed-integer nonlinear programming model. It is supposed that demand is an uncertain parameter. Finally in the third stage, suppliers, remanufacturing subcontractors, and refurbishing sites are selected and order allocation is determined. To this end, a multi-objective mixed-integer linear programming model is presented. An illustrative example is conducted to show the process. The main novel innovation of the proposed model is to consider the CLSC network configuration and selection process simultaneously, under uncertain demand and in an uncertain decision-making environment.     

基于有限元和系统辨识的智能结构主动控制

探讨了一种压电智能结构的设计方法,包括动力学建模、控制器设计和闭环系统有限元仿真。首先采用有限元方法计算滤过白噪声激励下压电智能结构的响应,以此响应作为系统辨识方法的输入,采用基于观测器/K a lm an滤波器的系统辨识方法(O bserver/K a lm an filter iden tification,OK ID)得到系统的M arkov参数,亦即单位脉冲响应的采样值,然后采用特征系统实现算法(E igensystem R ea lization A lgorithm,ERA)得到系统的最小实现,基于此模型采用LQG优化算法设计鲁棒控制器,并将反馈控制引入有限元模型进行闭环系统仿真,根据仿真结果评价设计方案。此方法克服了有限元模型无法直接用于控制器设计的缺点,通过将反馈控制引入有限元模型,可用有限元方法研究控制器的性能,也适用于设计其它复杂智能结构。     

A performance analytical model of automated material handling system for semiconductor wafer fabrication system

To effectively analyse and evaluate the performances of closed-loop automated material handling system (AMHS) with shortcut and blocking in semiconductor wafer fabrication system, a modified Markov chain model (MMCM) has been proposed. The system characteristics, such as vehicle blockage and system’s shortcut configuration, are well considered in the MMCM. The state space explosion problem and computational challenge due to the increase of AMHS scale can be effectively eliminated. With production data from Interbay material handling system of a 300-mm semiconductor wafer fabrication line, the proposed MMCM is compared with simulation analysis model. The results demonstrate that the proposed MMCM is an effective modelling methodology for AMHS’s performance analysis at system design stage.     

Zernike polynomial based Rayleigh-Ritz model of a piezoelectric unimorph deformable mirror

Piezoelectric bimorph- or unimorph-type deformable mirrors are commonly used in adaptive optics to correct for time-dependent phase aberrations. In the optics community, the surface deformations that deformable mirrors are required to achieve, are routinely and conveniently described using Zernike polynomials. A Rayleigh-Ritz structural model, which uses Zernike polynomials directly to describe the displacements, is proposed in this paper. The proposed formulation produces a numerically inexpensive model that predicts deformations with remarkable accuracy. Since design variables, such as electrode layout, material properties, and mirror dimensions, are represented analytically, the model is well suited to optimization or sensitivity analysis applications. Furthermore, since the numerical implementation is very efficient, it could be employed in closed-loop control applications. Results achieved with the proposed model compare well with results from a traditional finite element analysis as well as experimental results of a representative design.     

Lognormal switching times for titanium dioxide bipolar memristors: origin and resolution

We measured the switching time statistics for a TiO(2) memristor and found that they followed a lognormal distribution, which is a potentially serious problem for computer memory and data storage applications. We examined the underlying physical phenomena that determine the switching statistics and proposed a simple analytical model for the distribution based on the drift/diffusion equation and previously measured nonlinear drift behavior. We designed a closed-loop switching protocol that dramatically narrows the time distribution, which can significantly improve memory circuit performance and reliability.     

An integrated approach to evaluating the production system in closed-loop supply chains

The increasing demands for environmental resource protection and sustainable development have been forcing enterprises to put sustainable supply chain management on their agendas in recent years. At the same time, intense global competition requires organisations to adopt practices that enable them to provide high-quality products and services. In this paper, we consider the problem of comprehensively evaluating the production system in closed-loop supply chains. We first propose an evaluation framework that consists of economic evaluation, product quality evaluation and ecological evaluation modules. Based on mathematical probability theory and the dynamic characteristics of reverse supply chain logistics, we then focus on the evolution dynamics in the quality evaluation dimension, where the concept of product quality, which builds on the reliability and the time-utility value of a product, is proposed. The basic production evaluation model is then extended to incorporate different sustainable procurement strategies, which take into consideration the trade-offs among cost, environment and quality. An outline and corresponding flow chart of corporate procurement strategy optimisation are provided which allow the proposed evaluation model to be implemented in computer-aided decision-making, further providing decision support for production system and supply chain management. Simulation and case studies are presented to promote a better understanding of the model approach and its managerial implications. Results also suggest that quality characteristics of components and sustainable procurement strategies are two important factors that determine the final production performance and should be paid special attention in closed-loop supply chain practice.     

Facility location and scale optimisation in closed-loop supply chain

This paper solves a strategic-level decision problem on determining the optimal location of (re)manufacturers and logistics centres with the consideration of facility scales in an integrated closed-loop supply chain network. A two-stage stochastic mixed-integer non-linear programming model is established to minimise the fixed cost and the expected operation costs under uncertain demand and return. We develop an improved tabu search heuristic algorithm to solve the model. We also design a distance-based decision rule to validate the effectiveness of the proposed model. Numerical experiments are conducted to test the performance of the proposed model and the solution method. In addition, sensitivity analysis is provided to investigate the influences of varying inspection locations and recovery rates on the final performance.     

不确定电液位置伺服系统的动态面跟踪控制

针对一类含有动态不确定性的双作用液压缸电液伺服系统跟踪控制问题,采用动态面控制方法设计了一个鲁棒自适应跟踪控制器.由于在逆推设计过程中加入了低通滤波器使得该方法不用对模型非线性进行多次微分,因而设计方法简化.所设计的自适应鲁棒控制器不仅能保证闭环系统的半全局渐近稳定,使得输出渐近跟踪期望轨迹;而且,跟踪误差可以通过控制器的设计参数加以调整.数字仿真结果表明,控制系统对给定位置的跟踪具有良好的动态特性,对系统的不确定性,具有较强的鲁棒性.     

Long run and transient analysis of a double EWMA feedback controller

The “predictor-corrector” feedback controller is a popular adjustment scheme proposed for the quality control of certain semiconductor manufacturing process steps. This controller is based on a double Exponentially-Weighted Moving Average (EWMA) scheme; thus the performance of the closed-loop system depends on the two weight parameters of the EWM A equations. In this paper, the conditions the weights must satisfy to ensure closed-loop stability are discussed. The optimal determination of the controller weights depends on a trade-off between long-run process variance and transient bias performance. It is shown that small weights, although they can guarantee stability, may result in severe, long transients, an important concern if fabrication is in small batches. An optimization model for finding the controller weights is given and numerically solved. An extension of this type of controllers to the multiple controllable factor case is described. The performance of the controller is illustrated with an application to Chemical Mechanical Polishing, a critical semiconductor manufacturing step.     

基于EPR的废旧电器闭环供应链博弈分析

以生产者责任延伸制度为依据,针对电器电子产品闭环供应链中的正向物流和逆向物流阶段,运用博弈论方法分别构建政府、生产者和消费者的动态和静态博弈模型,分析各参与主体的博弈关系和博弈均衡解,得到不同利益相关者的决策影响因素。分析结果表明,电器电子产品闭环供应链的良好运行需要各博弈方达到利益均衡,政府决策会影响生产者和消费者参与电器电子产品闭环供应链的积极性,据此提出促进电器电子产品闭环供应链实施和发展的有效建议。     

Closed loop supply chain network design and optimisation using fuzzy mixed integer linear programming model

Owing to the revolution in sustainable and green manufacturing the production planning and network design of closed loop supply chain concept has got the attention of researchers and managers. In this paper, a multi-product, multi-facility capacitated closed-loop supply chain framework is proposed in an uncertain environment including reuse, refurbish, recycle and disposal of parts. The uncertainty related to demand, fraction of parts recovered for different product recovery processes, product acquisition cost, purchasing cost, transportation cost, processing, and set-up cost is handled with fuzzy numbers. A fuzzy mixed integer linear programming model is proposed to decide optimally the location and allocation of parts at each facility and number of parts to be purchased from external suppliers in order to maximise the profit of organisation. The proposed solution methodology is able to generate a balanced solution between the feasibility degree and degree of satisfaction of the decision maker. The proposed model has been tested with an illustrative example.