An empirical study of moving horizon closed-loop demand response scheduling

The potential of electricity-intensive chemical plants to engage in demand response (DR) initiatives in support of power grid operations has been the subject of many conceptual studies. In this work, using an industrially-relevant model of an air separation unit, we undertake an extensive simulation study of moving horizon (MH) scheduling approaches, where we “close the scheduling loop” based on updated information regarding disturbances such as changes in electricity prices, ambient conditions and chemical product demand. Our study produces several unexpected findings regarding the non-periodic nature of rescheduling solutions, the impact of the accuracy of disturbance forecasts on the economics of DR scheduling, and the interplay of simultaneously dealing with fluctuations on both the supply side (i.e., electricity prices) and the product demand side of the plant. We posit that the latter fluctuations pose significant limitations to the potential of a chemical plant to engage in DR.     

面向智能管道的PCC闭环系统部署方案研究

近年来,随着移动互联网的高速发展,移动数据流量迅猛增长。为保障和提升数据流量价值,移动通信网络部署了PCC网络,但有效的策略管控机制仍未形成。为推进PCC规模部署,提出了PCC闭环体系的概念,对如何构建数据业务智能管道,实现网络智能管控的具体方案进行研究,同时提供可在现有网络中部署的数据业务管控策略。     

基于可编程多轴控制器的三轴转台控制系统

基于可编程多轴控制器(PMAC)的三轴实验转台闭环控制系统由转台、PMAC、驱动器、执行器和检测装置等组成.倾角传感器测量载体的X、Y轴摇摆角度为位置环,光电编码器作速度环,转台搜索、跟踪由Z轴实现.转台水平稳定、方位轴搜索、跟踪等控制程序用PMAC语言编写.系统PID参数调整按先比例、后积分、再微分的顺序采用凑试法由小到大整定.     

Disassembly system modeling and design with parts selection for cost,recycling and CO2 saving rates using multi criteria optimization

Environmental issues in supply chains have been serious for not only the reduction of CO₂ emissions but also for material starvation. End-of-life assembly products at recycling factories should be disassembled environmentally and economically in consideration of not only low carbonization but also of material circulation. Parts with higher recycling and CO₂ saving rates should be selected and manually disassembled; however, the manual disassembly brings a higher cost, instead of disposing of the parts. Moreover, this parts selection also affects a disassembly line balancing.This study proposes a simple and practical modeling and design of multi criteria optimization for lower disassembly cost, higher recycling, and CO₂ saving rates by an environmental and economic parts selection, and subsequent disassembly line balancing.     

Impact of vapor recompression in batch distillation on energy consumption,cost and CO2 emission: Open-loop versus closed-loop operation

This paper aims at analyzing the thermal integration of direct vapor recompression system with a distillation column operated in batch mode. The unsteady state nature of the batch processing makes the use of vapor recompression a challenging task. For a meaningful comparison, it is attempted to run the vapor recompressed batch distillation (VRBD) column at same dynamics with its conventional counterpart. With this operating objective, the manipulation of a few process variables is proposed in open-loop fashion. Along with the energy savings and total annualized cost, the CO₂ emission level is also used for quantitative performance evaluation of the proposed VRBD column. Aiming to produce a constant and high-purity distillate product, a gain-scheduled proportional integral (GSPI) controller that targets to keep the stability margin constant is devised for the VRBD process. Finally, this heat integration mechanism is illustrated by a binary batch distillation example in both open-loop and closed-loop modes. It is investigated that the VRBD shows a slightly higher energy savings (62%) compared to its closed-loop version (59.13%) but at the expense of distillate purity. The heat integration also achieves a significant savings in cost and CO₂ emission.     

An optimal PID controller via LQR for standard second order plus time delay systems

An improved tuning methodology of PID controller for standard second order plus time delay systems (SOPTD) is developed using the approach of Linear Quadratic Regulator (LQR) and pole placement technique to obtain the desired performance measures. The pole placement method together with LQR is ingeniously used for SOPTD systems where the time delay part is handled in the controller output equation instead of characteristic equation. The effectiveness of the proposed methodology has been demonstrated via simulation of stable open loop oscillatory, over damped, critical damped and unstable open loop systems. Results show improved closed loop time response over the existing LQR based PI/PID tuning methods with less control effort. The effect of non-dominant pole on the stability and robustness of the controller has also been discussed.     

Optimal learning control of oxygen saturation using a policy iteration algorithm and a proof-of-concept in an interconnecting three-tank system

In this work, “policy iteration algorithm” (PIA) is applied for controlling arterial oxygen saturation that does not require mathematical models of the plant. This technique is based on nonlinear optimal control to solve the Hamilton–Jacobi–Bellman equation. The controller is synthesized using a state feedback configuration based on an unidentified model of complex pathophysiology of pulmonary system in order to control gas exchange in ventilated patients, as under some circumstances (like emergency situations), there may not be a proper and individualized model for designing and tuning controllers available in time. The simulation results demonstrate the optimal control of oxygenation based on the proposed PIA by iteratively evaluating the Hamiltonian cost functions and synthesizing the control actions until achieving the converged optimal criteria. Furthermore, as a practical example, we examined the performance of this control strategy using an interconnecting three-tank system as a real nonlinear system.     

The boomerang returns? Accounting for the impact of uncertainties on the dynamics of remanufacturing systems

Recent years have witnessed companies abandon traditional open-loop supply chain structures in favour of closed-loop variants, in a bid to mitigate environmental impacts and exploit economic opportunities. Central to the closed-loop paradigm is remanufacturing: the restoration of used products to useful life. While this operational model has huge potential to extend product life-cycles, the collection and recovery processes diminish the effectiveness of existing control mechanisms for open-loop systems. We systematically review the literature in the field of closed-loop supply chain dynamics, which explores the time-varying interactions of material and information flows in the different elements of remanufacturing supply chains. We supplement this with further reviews of what we call the three ‘pillars’ of such systems, i.e. forecasting, collection, and inventory and production control. This provides us with an interdisciplinary lens to investigate how a ‘boomerang’ effect (i.e. sale, consumption, and return processes) impacts on the behaviour of the closed-loop system and to understand how it can be controlled. To facilitate this, we contrast closed-loop supply chain dynamics research to the well-developed research in each pillar; explore how different disciplines have accommodated the supply, process, demand, and control uncertainties; and provide insights for future research on the dynamics of remanufacturing systems.     

High-bandwidth tracking control of piezo-actuated nanopositioning stages using closed-loop input shaper

An integrated control strategy for piezo-actuated nanopositioning stages is proposed in this paper. The aim is to achieve high-speed and high-precision tracking control of nanopositioning stages. For this purpose, a direct inverse compensation method is firstly applied to eliminate the hysteresis nonlinearity without involving inverse model calculation. Then, an inside-the-loop input shaper is designed to suppress the vibration of the compensated system. A Smith predictor is introduced to prevent the potential closed-loop instability caused by the time delay of the inside-the-loop input shaper. Finally, a high-gain feedback controller is employed to handle the disturbances and modeling errors. To demonstrate the effectiveness of the proposed control method, comparative experiments are carried out on a piezoelectric actuated stage. The results show that the proposed control approach increases the tracking bandwidth of the stage from 22.6 Hz to 510 Hz.     

电源控制芯片中的过流保护设计

本文介绍采用直接检测LDMOS漏端电压来判断其是否过流的设计方法,给出了电路结构.通过电路分析,并利用BCD高压工艺,在cadence环境下进行电路仿真验证.结果证明:该方法能够快速、实时地实现过流保护功能,相比其它方法,在功耗、效率、工艺兼容性、成本等方面均有很大提高,可以直接应用于电源控制芯片中的安全保护设计.