Guaranteed Cost Consensus for High-dimensional Multi-agent Systems With Time-varying Delays

Guaranteed cost consensus analysis and design problems for high-dimensional multi-agent systems with time varying delays are investigated. The idea of guaranteed cost con trol is introduced into consensus problems for high-dimensiona multi-agent systems with time-varying delays, where a cos function is defined based on state errors among neighboring agents and control inputs of all the agents. By the state space decomposition approach and the linear matrix inequality(LMI)sufficient conditions for guaranteed cost consensus and consensu alization are given. Moreover, a guaranteed cost upper bound o the cost function is determined. It should be mentioned that these LMI criteria are dependent on the change rate of time delays and the maximum time delay, the guaranteed cost upper bound is only dependent on the maximum time delay but independen of the Laplacian matrix. Finally, numerical simulations are given to demonstrate theoretical results.

Distributed Periodic Event-Triggered Optimal Control of DC Microgrids Based on Virtual Incremental Cost

This article presents a distributed periodic eventtriggered(PET)optimal control scheme to achieve generation cost minimization and average bus voltage regulation in DC microgrids.In order to accommodate the generation constraints of the distributed generators(DGs),a virtual incremental cost is firstly designed,based on which an optimality condition is derived to facilitate the control design.To meet the discrete-time(DT)nature of modern control systems,the optimal controller is directly developed in the DT domain.Afterward,to reduce the communication requirement among the controllers,a distributed event-triggered mechanism is introduced for the DT optimal controller.The event-triggered condition is detected periodically and therefore naturally avoids the Zeno phenomenon.The closed-loop system stability is proved by the Lyapunov synthesis for switched systems.The generation cost minimization and average bus voltage regulation are obtained at the equilibrium point.Finally,switch-level microgrid simulations validate the performance of the proposed optimal controller.

Guaranteed Cost Active Fault-tolerant Control of Networked Control System with Packet Dropout and Transmission Delay

The problem of guaranteed cost active fault-tolerant controller （AFTC） design for networked control systems （NCSs） with both packet dropout and transmission delay is studied in this paper. Considering the packet dropout and transmission delay, a piecewise constant controller is adopted. With a guaranteed cost function, optimal controllers whose number is equal to the number of actuators are designed, and the design process is formulated as a convex optimal problem that can be solved by existing software. The control strategy is proposed as follows： when actuator failures appear, the fault detection and isolation unit sends out the information to the controller choosing strategy, and then the optimal stabilizing controller with the smallest guaranteed cost value is chosen. Two illustrative examples are given to demonstrate the effectiveness of the proposed approach. By comparing with the existing methods, it can be seen that our method has a better performance.

Optimal guaranteed cost control for fuzzy descriptor systems with time-varying delay

Based on the delay-independent rule, the problem of optimal guaranteed cost control for a class of Takagi-Sugeno （T-S） fuzzy descriptor systems with time-varying delay is studied. A linear quadratic cost function is considered as the performance index of the closed-loop system. Sufficient conditions for the existence of guaranteed cost controllers via state feedback are given in terms of linear matrix inequalities （LMIs）, and the design of an optimal guaranteed cost controller can be reduced to a convex optimization problem. It is shown that the designed controller not only guarantees the asymptotic stability of the closed-loop fuzzy descriptor delay system, but also provides an optimized upper bound of the guaranteed cost. At last, a numerical example is given to illustrate the effectiveness of the proposed method and the perfect performance of the optimal guaranteed cost controller.

Guaranteed cost sampled-data control for uncertain nonlinear time-varying delay system

The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].

Guaranteed cost control for T-S fuzzy systems with time-varying delays

This paper deals with the problem of guaranteed cost control for nonlinear systems with time-varying delays which is represented by Takagi-Sugeno （T-S） fuzzy models with time-varying delays.The derivatives of time-varying delay are not necessary to be bounded.Based on the free weighting matrix method,sufficient conditions for the existence of fuzzy guaranteed cost controller via state feedback are given in terms of linear matrix inequalities （LMIs）.A minimizing method is also proposed to search the suboptimal upper bound of the guaranteed cost function.The results are delay-dependent but contain delay-independent criteria as a special case.A numerical example is presented to demonstrate the effectiveness and less conservativeness of our work.

An Algorithm Based on Mobile Agent for Delay Constrained Least Cost Unicast Routing

The delay constrained least cost path problem with imprecise delay information is discussed, and a distributed heuristic algorithm without any assumption of imprecise state information is presented. The algorithm employs mobile agents to search feasible paths in parallel and requires limited network state information kept at each node. The simulations indicate that the presented solution provides better call acceptance probability and better fairness between short paths and long paths. And the algorithm can tolerate high degree of delay imprecision.

Optimal guaranteed cost control for an uncertain discrete T-S fuzzy system with time-delay

This paper considers the guaranteed cost control problem for a class of uncertain discrete T-S fuzzy systems with time delay and a given quadratic cost function. Sufficient conditions for the existence of such controllers are derived based on the linear matrix inequalities （LMI） approach by constructing a specific nonquadratic Lyapunov-Krasovskii functional and a nonlinear PDC-like control law. A convex optimization problem is also formulated to select the optimal guaranteed cost controller that minimizes the upper bound of the closed-loop cost function. Finally, numerical examples are presented to demonstrate the effectiveness of the proposed approaches.

Early versus delayed necrosectomy in pancreatic necrosis:A population-based cohort study on readmission,healthcare utilization,and in-hospital mortality

BACKGROUND Acute necrotizing pancreatitis is a severe and life-threatening condition.It poses a considerable challenge for clinicians due to its complex nature and the high risk of complications.Several minimally invasive and open necrosectomy procedures have been developed.Despite advancements in treatment modalities,the optimal timing to perform necrosectomy lacks consensus.AIM To evaluate the impact of necrosectomy timing on patients with pancreatic necrosis in the United States.METHODS A national retrospective cohort study was conducted using the 2016-2019 Nationwide Readmissions Database.Patients with non-elective admissions for pancreatic necrosis were identified.The participants were divided into two groups based on the necrosectomy timing:The early group received intervention within 48 hours,whereas the delayed group underwent the procedure after 48 hours.The various intervention techniques included endoscopic,percutaneous,or surgical necrosectomy.The major outcomes of interest were 30-day readmission rates,healthcare utilization,and inpatient mortality.RESULTS A total of 1309 patients with pancreatic necrosis were included.After propensity score matching,349 cases treated with early necrosectomy were matched to 375 controls who received delayed intervention.The early cohort had a 30-day readmission rate of 8.6% compared to 4.8%in the delayed cohort(P=0.040).Early necrosectomy had lower rates of mechanical ventilation(2.9%vs 10.9%,P<0.001),septic shock(8%vs 19.5%,P<0.001),and in-hospital mortality(1.1%vs 4.3%,P=0.01).Patients in the early intervention group incurred lower healthcare costs,with median total charges of $52202 compared to$147418 in the delayed group.Participants in the early cohort also had a relatively shorter median length of stay(6 vs 16 days,P<0.001).The timing of necrosectomy did not significantly influence the risk of 30-day readmission,with a hazard ratio of 0.56(95%confidence interval:0.31-1.02,P=0.06).CONCLUSION Our findings show that early necrosectomy is associated with better clinical outcomes and lower healthcare costs.Delayed intervention does not significantly alter the risk of 30-day readmission.

级联式双向DC-DC变换器的模型预测控制

级联式双向DC-DC变换器具有结构简单、功率密度高且适用于大变比变换场合等优点,但其传统的双闭环控制方法中,控制结构复杂,PI参数设置困难。据此引入模型预测控制(MPC)思想对级联式双向DC-DC变换器进行控制。模型预测控制具有控制思想简单、易于包含系统的约束条件及控制器易于实现等优点,该控制策略包括建立变换器模型和其可能的开关状态、定义代价函数两个步骤。本文对级联式双向DC-DC变换器的模型预测控制进行仿真分析和实验验证。同时,将其与传统双闭环控制方法进行实验对比,实验结果显示,模型预测控制方法能够使母线电压准确追踪给定值,与传统双闭环控制相比,动态过程中母线电压的超调减小6.25%左右,变换器的动态响应时间减少0.3s。由此证明所提出模型预测控制方法的可行性及有效性。

基于DCS技术的联合收割机作业路径控制研究

以联合收割机协同作业过程为研究对象,对多台联合收割机协同作业过程中的行进速度、作业幅宽及单台收割机作业成本等因素进行分析,提出了一种以收割成本控制为目标的联合收割机作业路径控制优化算法,并采用DCS技术搭建联合收割机系统作业调度控制系统。仿真实验结果表明:在协同收割作业时,收割机调度控制系统能够根据收割需求、按照最小收割成本进行联合收割机数量及收割机型的调度控制;收割机作业时,能够根据最优化路径进行作业,最大幅度地提高收割作业效率,同时确保收割作业成本最低。

一种适用于DC/DC控制器的测试及修调电路设计

采用0.25μm BCD商用工艺,设计了一种适用于DC/DC控制器的测试及修调电路.该电路基于引脚功能复用的思胳,通过对特定引脚施加特定信号,在不影响控制器正常工作时的引脚信号状态的情况下,既能够在圆片级或封装后实现内部信号的读取以及参数指标的修调,又能够克服封装寄生效应对高电压精度以及大电流测试的影响,具有测试操作简单、测试成本低廉、测试范围广泛等优点.该电路缓解了传统PAD扎针加压方案在熔丝数量较多时突出的面积问题;解决了传统激光切割方案需要昂贵激光修调设备及编写ATE程序的成本问题;改善了两种传统修调方案均只能在圆片级测试,不适合高精度、大电流测试的应用问题.该电路内部结构包括寄存器时钟及数据输入电路、测试及修调使能电路、测试及修调阵列电路、测试数据输出电路.仿真结果表明,在DC/DC控制器开环状态下,通过配置特定端口的数据位,能够通过测试电路实现振荡器输出振荡信号等内部典型信号的输出,实现关键指标导通电阻的测试,通过修调电路实现关键参数基准电压精度的修调.

Guaranteed cost control of networked control systems under limited communication capacity and variable sampling

The problem of guaranteed cost control for the networked control systems(NCSs) with time-varying delays, time-varying sampling intervals and signals quantization was investigated, wherein the physical plant was continuous-time one, and the control input was discrete-time one. By using an input delay approach and a sector bound method, the network induced delays, quantization parameter and sampling intervals were presented in one framework in the case of the state and the control input by quantized in a logarithmic form. A novel Lyapunov function with discontinuity, which took full advantages of the NCS characteristic information, was exploited. In addition, it was shown that Lyapunov function decreased at the jump instants. Furthermore, the Leibniz-Newton formula and free-weighting matrix methods were used to obtain the guaranteed cost controller design conditions which were dependent on the NCS characteristic information. A numerical example was used to illustrate the effectiveness of the proposed methods.

Influence of dc Component during Inadvertent Operation of the High Voltage Generator Circuit Breaker during Mis-Synchronization

This paper analyses the synchronization problem of a generator onto power system without satisfying synchronization condition. The main focus of the paper is on the impact of the dc component of the current in the high voltage circuit breaker during its close-open operating cycle. Using real time measurements of currents/voltages and angles during the close-opening cycle of high voltage generator circuit breaker and the impact of the dc component of current in context of interrupting large magnitude of current from the circuit breaker. In addition, the paper describes a study case model and the results of simulations performed using the software EMTP-ATP of an actual incident that occurred during the inadvertent synchronization of a large 339 MW, 24 kV generator to the grid.

Non-fragile guaranteed cost control for uncertain neutral large-scale interconnected systems

This paper focuses on the problem of non-fragile decentralized guaranteed cost control for uncertain neutral large-scale interconnected systems with time-varying delays in state,control input and interconnections.A novel scheme,viewing the interconnections with time-varying delays as effective information but not disturbances,is developed.Based on Lyapunov stability theory,using various techniques of decomposing and magnifying matrices,a design method of the non-fragile decentralized guaranteed cost controller for unperturbed neutral large-scale interconnected systems is proposed and the guaranteed cost is presented.The further results are derived for the uncertain case from the criterion of unperturbed neutral large-scale interconnected systems.Finally,an illustrative example shows that the results are significantly better than the existing results in the literatures.

基于DCS系统平台磨矿自动加球控制系统设计

传统矿山磨矿钢球添加主要分为全人工手动加球和以PLC为核心新增配置一套单体控制系统进行加球,存在安全系数不高、成本高、设备利用率低等问题。充分运用现有DCS系统平台进行钢球添加控制系统设计,从而实现磨矿钢球添加全自动循环控制。生产实践证明,该系统使用操作简单、准确及时、稳定可靠、维护量小,可大幅度减轻工人的劳动强度,提高安全生产系数,提高工艺生产指标,增加企业经济效益和社会效益。

基于DCS开发的300MW机组运行成本在线管理系统

针对 30 0 MW机组在变负荷工况下缺少运行成本分析过程的情况 ,利用电厂现有 DCS的实时数据 ,对机组运行性能指标进行动态管理 ,实时核算运行发电成本 ,并给出降低成本的调整方法 。

Study of Factors Causing Time and Cost Overrun in Pre-Construction Project (A Case Study of Malaysia)

Cost and time overrun are the key troubles of any improvement ventures. These troubles are inflicting the terrible end result in the development of kingdom monetary improvement and thriving. To overcome these problems, the?paper examines predominant impact on elements causing the mission postponement and cost. A poll review was led for the situation study embracing various information-gathering procedures. The discoveries from the contextual investigation uncovered that the most persuasive factors in Malaysia:?1) contractor’s inappropriate arranging, 2) poor site the board, 3) deficient contractual worker experience,?are the most powerful factors. This paper has likewise broken down the normal and least effective of the postpone variables causing task deferral and cost overrun in Malaysia. It likewise infers that there are various measures as per the idea of deferring components to decrease the effect on task postponement and cost overruns in the development industry.?There are significant factors in the control of time overrun that would be actual thought related to know and tackle in great impact to improvement rate which may additionally no capacity that be recovered. Thirty (30) massive development extensions in Malaysia were exceptional coping with time overrun at some stage in development. Out of 30 undertakings, 17 (56.67%) ventures had been introduced by using 1100 days’ time overrun, 5 (16.67%) extensions in the middle of a hundred and one to 200 days, 5 (16.67%) ventures?201 to 300 days while three (10%) ventures have been deferred for timeframe over 300 days.

DC 1500V光伏发电系统研究与应用分析

太阳能光伏发电在近年来得到了高速发展,已成为解决化石能源短缺和应对气候变化的重要途径。文章在介绍了光伏发电系统基本结构的基础上,分析了现行DC 1 000V光伏发电系统设计方案在降低系统成本和提高系统效率方面极其有限的现状,具体介绍了DC 1 500V光伏发电系统的设计基础,以及在降低系统成本和提高系统效率方面的优势,并给出了具体设计方案和分析了应用前景。

Delays to Large Construction Projects in Ghana： A Risk Overview

Delay to large scale projects, which is as a result of actions or inactions of some project stakeholders, is becoming a global phenomena and Ghana is no exception. The objective of the research is to identify, rate and rank the most significant risk factors that causes delay on projects and examine the social impact of these delays to recommend modalities to help mitigate these risk factors. The study adopted quantitative methods with the distribution of 144 questionnaires to built environment professionals receiving a response rate of 75.7%. The instrument listed 58 common factors under eight categories that contribute to the causes of delay for respondents to rate. Analysis of data non-parametric test revealed that client, contractor, material and finance category factors significantly resulted in the schedule delay of large infrastructural projects. The survey analysis revealed that micro-factors that result in delays to large construction projects are time constraint, cost overrun, payment problems, dispute and litigation. The research recommended the following modalities to minimize such delays： availability of resources, improved communication and coordination, proper scope definition and feasibilities, utilization of modern technology, appropriate application of technologically based systems and competent project management＇s structures.