Estimating performance enhancement with alternate control strategies for multiloop control systems

A filter based methodology, studied earlier for SISO systems, is extended to MIMO systems. The presented approach facilitates the calculation of best achievable performance for proportional-integral (PI) controller and the optimal multiloop (ML) PI settings for stochastic disturbance rejection in ML control systems. The filter based approach is further extended to answer some of the key questions for ML control systems such as: (a) performance enhancement possible with the alternate pairing scheme, (b) benefits that will accrue through the employment of decouplers and (c) the performance achievable with the use of multivariable controller (as opposed to an ML controller). Further, the trade-off curve between output variance and control effort is generated for the various control configurations within PI controller domain.     

基于PSO-控制变量参数化混合策略的间歇化工过程优化控制

控制变量参数化方法作为一种化工过程动态优化的梯度搜索算法，其求解效率过于依赖初始给定轨迹。目前初始轨迹一般都是设定在边界值或中间值，缺乏科学依据，从而大大影响了算法的收敛速度。针对这一问题，提出了一种粒子群优化(PSO)与控制变量参数化方法混合的策略，首先利用粒子群优化对间歇化工过程最优控制量进行求解，结果作为控制变量参数化方法初始给定轨迹，进行二次优化。双层优化的混合策略提高了控制变量参数化方法的收敛速度和粒子群优化算法的求解精度。将混合策略应用于两个间歇化工过程优化控制实例，仿真结果表明了该算法对求解化工过程动态优化问题具有可行性和有效性。     

Particle-wave duality and coherent instability control in dense gas-solid flows

The collective effect of transport behaviors in a multibody system can either drastically enhance or deteriorate system performance depending on the nature of the internal interactions (i.e., constructive or deconstructive) and the structure established. For most powder processes, flow instability leads to poor performance. Control strategies have been attempted previously, but with limited success. The ability to drive such a system that is far from equilibrium into its “ordered” state by tuning the interactions can effectively reduce internal energy dissipation, which may lead to a technological breakthrough.By using a hybrid dynamics simulation and multiphase flow experiments, we will first elucidate two fundamental mechanisms underlying flow instabilities in a dense gas-solid flow: nonlinear drag and collisional dissipation. Then we clarify how gas-fluidized particles exhibit “particle-wave” duality (e.g., exhibit standing waves in a thin layer of granular bed that are driven by superimposed oscillating air, when the exciting frequencies of the oscillating air match the system's natural frequency). On this basis, we show experimentally that dense gas-fluidized granules can be synchronized into “ordered” structures by developing an adaptively exciting fluid wave. The introduction of an additional fluid wave enables the flow structures to be fine-tuned. Our method results in remarkably improved fluidization: highly expanded particulate beds with significantly suppressed gas bubble formation (for coarse particles) and channel formation (for ultra-fine powders), as has always prevailed in conventional dense gas-particle systems. By applying our methodology to several systems that are normally difficult to fluidize, we achieve unprecedented, well-controlled suspension of solids in gas flow.A scientific understanding of complex, dense gas-solid flows should enable the dispersion of solids in the gas flow to be controlled effectively. This work contributes to the basic science of dense gas-solid flows and would have impacts on powder technology, pharmaceutical manufacturing, and the optimum design of the third generation of fluidized bed reactors, such as the use of fast pyrolysis, to produce fuels from biomass and coal feedstock.     

Model-based control strategies for a chemical batch reactor with exothermic reactions

Batch reactor control provides a very challenging problem for the process control engineer. This is because a characteristic of its dynamic behavior shows a high nonlinearity. Since applicability of the batch reactor is quite limited to the effectiveness of an applied control strategy, the use of advanced control techniques is often beneficial. This work presents the implementation and comparison of two advanced nonlinear control strategies, model predictive control (MPC) and generic model control (GMC), for controlling the temperature of a batch reactor involving a complex exothermic reaction scheme. An extended Kalman filter is incorporated in both controllers as an on-line estimator. Simulation studies demonstrate that the performance of the MPC is slightly better than that of the GMC control in nominal case. For model mismatch cases, the MPC still gives better control performance than the GMC does in the presence of plant/model mismatch in reaction rate and heat transfer coefficient.     

多机制冷系统在线优化控制策略

阐述了可应用于大型商业建筑中多台制冷机系统的在线优化控制策略。策略的应用可增强控制鲁棒性并节约运营成本。优化控制策略包括冷冻水供水温度优化、制冷机时序控制、启动优化控制和建筑峰值负荷控制。冷冻水供水温度的优化使得系统在满足负荷的前提下制冷机和冷冻水泵的能耗最小。在时序控制中,3种方法的采用增强了控制的鲁棒性:第一,数据融合以获得可靠楼宇冷负荷的测量;第二,制冷机最大制冷能力简化模型的应用;第三,在线传感器故障诊断(FDD)的应用。在制冷机启动优化控制中,一个基于模型的策略用于最小化早晨启动时期内的系统能耗。这一基于模型的最优启动优化控制策略同时考虑了预冷能力和预冷时间的相互关系。建筑峰值负荷控制以优化月节电费为目标,通过预测合适的每月负荷阈值并依此限制每天的峰值负荷来实现这一目的。通过对香港一幢大型商业建筑内中央制冷系统的动态模拟,以上控制策略得到验证。     

Composition control of tin-zinc deposits using experimental strategies

The robust electroplating settings of a direct-current (dc) plating mode for the co-deposition of Sn-Zn deposits with their composition close to the eutectic point (i.e., Sn-9Zn) from the chloride solutions were achieved and investigated by using experimental strategies, including the fractional factorial design (FFD) and central composite design (CCD) coupled with the response surface methodology (RSM). The temperature of the plating bath, pH, and the metallic ion ratio (i.e., Sn⁴⁺/Zn²⁺ ratio) were found to be the key factors affecting the composition of Sn-Zn deposits in the FFD study. The effects of pH and temperature of the plating solution on the composition of Sn-Zn deposits were examined using a regression model in the CCD study. This model, represented as contour plots, showed that pH 5.0 and temperature = 78 °C were the robust electroplating settings for the co-deposition of the eutectic Sn-Zn alloys, which was independent of the substrates. In addition, based on the robust plating settings, the composition of Sn-Zn alloys could be precisely controlled and predicted by adjusting the composition of the plating baths. From the morphologies and crystalline information, the binary Sn-Zn deposits prepared in this work should belong to heterogeneous alloys.     

化工污染的危害及其防治策略

化学工业在改变我们生活的同时，也带来了严重的污染问题。本文综述了化工污染的种类及来源，以及有害化学品的危害。并提出了健全环境立法，推行清洁生产，强化废物管理，鼓励公众监督等一系列防治措施。     

Development of computer control strategies for plastic extruders

The basic idea of automatic control of extrusion machinery is considered. Dynamic interaction among process variables is discussed and it is suggested that a practical form of control might involve steady-state control of screw and barrel temperature coupled with dynamic control of screw speed. Several alternative forms of control strategy are examined and it is suggested that for higher forms of control, a computer is required together with an accurate process model relating control and controlled variables. With such a strategy, polymer temperature and pressure at the die would be controlled by continuous variations in screw speed coupled with infrequent control of die resistance to counter long term drift and to facilitate pressure and temperature change matching. Methods for developing process models are considered including those for adaptive/predictive control strategies using time-series techniques and some experimental results are given. The basic form of a computer control system is outlined and the areas where further research is required are indicated.     

Helical polyaniline induced by specific interaction with biomolecules in neutral solution

Some kinds of sugar and amino acid are used to interact with polyaniline emeraldine base in neutral aqueous solution. PANI complexed with these molecules shows interesting induced circular dichirom (ICD) spectra, which indicates that excess one-handed helical structure is induced on PANI. Furthermore, opposite ICD spectra are observed for PANI while it is interacted with l- and d-amino acid, respectively. It is presumed that H-bonding interaction plays a central role in such a helical induction. This is the first example to prepare optically active PANI in neutral solution by one step without protonating EB into polycation in advance.     

Discriminating between Phytoplankton Taxa by Photoacoustics

We present here an application of the photoacoustic method for studying and discriminating between important phytoplankton taxa in suspension. The photosynthetic activity was studied by measuring the photoacoustic signal with and without background illumination. A linear dependence of the photoacoustic signal on the biomass of different algae was observed along with wavelength-dependent differences between the various phytoplankton taxa. The photoacoustic signals from mixtures of pairs of taxa were measured at different ratios of the mixture components and at selected wavelengths at which the differences in absorption among the species were maximal. A linear dependence of the photoacoustic signal on the composition of each pair at the wavelengths studied was found. The results indicate the potential of the procedure for determining the composition of phytoplankton communities and following the effects of environmental parameters such as irradiance and nutrient status on the photosynthetic activity of phytoplankton.     

Integrated cyberattack detection and resilient control strategies using Lyapunov-based economic model predictive control

The use of an integrated system framework, characterized by numerous cyber/physical components (sensor measurements, signals to actuators) connected through wired/wireless networks, has not only increased the ability to control industrial systems but also the vulnerabilities to cyberattacks. State measurement cyberattacks could pose threats to process control systems since feedback control may be lost if the attack policy is not thwarted. Motivated by this, we propose three detection concepts based on Lyapunov-based economic model predictive control (LEMPC) for nonlinear systems. The first approach utilizes randomized modifications to an LEMPC formulation online to potentially detect cyberattacks. The second method detects attacks when a threshold on the difference between state measurements and state predictions is exceeded. Finally, the third strategy utilizes redundant state estimators to flag deviations from “normal” process behavior as cyberattacks.     

聚丙烯管材料鉴别方法的研究

通过红外光谱、差热分析(DSC)以及宏观物理机械性能等分析方法,分析了吉林石化公司乙烯厂生产的三种不同类型的聚丙烯产品;同时介绍了不同类型管材料的特点及应用范围.     

水体中的持久性有机污染物及其控制技术

概括了持久性有机污染物(Persistent organic pollutants,POPs)的定义和种类,介绍了国内外水体中POPs的污染现状,对水体中POPs的特性和危害做了简要分析,并全面综述了POPs的控制技术.     

SBR工艺智能控制策略的研究进展

现今SBR工艺已经广泛应用于处理各种中小水量的工业废水。总结归纳了SBR智能控制策略的类型,重点对模糊控制、专家系统和神经网络等高级控制策略进行较为详细的论述,并介绍了混合智能控制策略研究现状。最后针对SBR智能控制策略存在的问题和不足,为其进一步发展提出具体的建议。     

精细化工废水的污染特性分析及其控制策略

针对精细化工废水处理难以稳定达标的现状,采用国家标准方法、离子色谱、ICP/MS、GC/MS等分析手段研究了浙江省某工业园区精细化工废水的COD、BOD、氨氮、色度等常规指标及主要阴阳离子和有机物组成,从化学与生物水平揭示了精细化工废水的污染特性,并提出了针对精细化工废水污染过程的控制策略。研究结果表明,精细化工废水是一种典型的有毒/难降解工业有机废水,呈现高COD、高氨氮及高色度等特征;精细化工废水中对微生物构成危害的主要成分有COD、氨氮、部分重金属离子、染料及其分解物等,重点是有机污染物;精细化工废水中的有机成分大多属于有毒/难降解有机污染物,对生物系统存在严重的抑制作用,是造成出水不达标的主要原因。因此,对精细化工废水的处理,应着重对有毒/难降解有机物进行优先控制,并综合考虑高效的处理工艺、合理的水质结构及有效的政策性策略。     

Diameter control of multiwalled carbon nanotubes using experimental strategies

Multiwalled carbon nanotubes (MWNTs) were synthesized using a chemical vapor deposition floating feed method in a vertical reactor. Effects of the preparation variables on the average diameter of carbon nanotubes were systematically examined using the fractional factorial design (FFD), path of the steepest ascent, and central composite design (CCD) coupled with the response surface methodology. From the FFD study, the main and interactive effects of reaction temperature, methane flow rate, and chamber pressure were concluded to be the key factors influencing the diameter of MWNTs. Two empirical models, representing the dependence of the diameter of carbon nanotubes at the vicinities around maximum (420 nm) and minimum (15 nm) on the reaction temperature and methane flow rate, were constructed in two independent CCD studies. These models, shown as contour diagrams, indicated that the diameter of carbon nanotubes generally increased with increasing reaction temperature and methane flow rate. Based on both models, the diameter of MWNTs from 15 to 420 nm can be controlled precisely by using a continuous CVD fabrication method.     

Nanostructures with coherent boundaries and the local approach

Nanostructures with coherent boundaries are considered in the framework of the local approach. It is demonstrated that the use of the fiber space formalism makes it possible to derive a set of geometrical structural complexes that are building blocks of nanostructures. These complexes are determined by the specific sub-configurations of finite projective planes. It is shown that, in the case of fourfold-coordinated structures, crystalline and quasicrystalline fragments can intergrow coherently (without dangling bonds).Original Russian Text Copyright © 2004 by Fizika i Khimiya Stekla, Shevchenko, Samoilovich, Talis, Madison.