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2011 American control Conference (ACC)

作者： Jun Liu Linbo Xie Min Zhang Zhihai Wu Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education) Institute of Systems Engineering University of Jiangnan Wuxi China Jiangsu Province Pharmaceutical Industry Design Institute China

Recently, Networked control Systems (NCSs) and quantized feedback control have received a lot of attention. We consider analysis of quantized estimation and investigation of stability connection between estimation error system (EES) and quantized estimation feedback control system (QEFCS) in this paper. We assume that there are two-quantized signals being passed to the estimator and the controller through network channels in the closed-loop NCS. Using adjustable zoom quantizer parameters, Lyapunov-based quadratically stabilizable conditions of NCSs are presented. We also propose a method to disclose the stability connection of EES and QEFCS by the use of the connected invariant region sequences. Numerical example and simulation results demonstrate the effectiveness of the method.

关键词： Quantization Feedback control Stability analysis Numerical stability Noise Estimation error

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Optimal control over unreliable networks with uncertain loss rates

Optimal control over unreliable networks with uncertain loss...

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作者： Kögel, Markus J. Blind, Rainer Allgöwer, Frank Institute for Systems Theory and Automatic Control University of Stuttgart Stuttgart Germany Laboratory for Systems Theory and Automatic Control Institute for Automation Engineering Otto-von-Guericke University Magdeburg Magdeburg Germany Design and Optimization in Chemical and Biochemical Process Engineering International Max Planck Research School for Analysis Magdeburg Germany

ISBN: (纸本)9781424474264

In this work, we consider an optimal control problem for Networked control Systems (NCS), where the loop is closed via an unreliable network. In order to inform the controller about the fates of the control packets, the actuator sends acknowledgements to the controller. In this work, different types of acknowledgements are considered. Since all packets are send over a network, we consequently assume, that all packets can get lost, i.e. the measurement packets, the control packets as well as the acknowledgement packets. The loss of these packets is modeled by independent and identically distributed (iid) Bernoulli processes. Finally, we assume that the parameters of these loss processes are not known exactly. Using this setup, we derive bounds for the uncertainty in the loss rates. Moreover, we present an algorithm to design a sub-optimal controller which can tolerate a given amount of network uncertainties. © 2010 AACC.

关键词： Networked control systems

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Modeling growth of microalgae Dunaliella salina under different nutritional conditions

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American Journal of Biochemistry and Biotechnology 2010年第4期6卷 279-283页

作者： Jesus, Sergio Santos Filho, Rubens Maciel Department of Chemical Process Laboratory of Optimization Design and Advanced Control School of Chemical Engineering University of Campinas Unicamp Cidade Universitária Zeferino Vaz CP 6066 Campinas SP Brazil

Problem statement: The aim of this study was to find the empirical model that describes the growth kinetics of Dunaliella salina, with low production cost and to estimate parameters of this model. Approach: In this study the strain of D. salina UTEX 200 was cultivated in seawater (0.5 M NaCl) at room temperature with agitation of 150 rpm and luminous intensity of 60 mmols.m-2.s-1. The synthetic medium AS100 (0.2 M NaCl) was used in this study for comparison purposes and in order to determine the optimal growth of the microalgae. Kinetics of growth and β-carotene production was determined in a period of 15 days. Results: After the analysis of the behavior graphic, an unstructured model was used for describing the cell growth (logistic model). It was observed that the model was well adjusted to experimental data for the two conditions of analysis. It was observed that alga produces carotenoids under conditions of stress, in which the cell division are retarded. In the case of cells grown in seawater (higher salt concentration), the cell growth was lower but the concentration of β-carotene was higher. Conclusion: In general, these results suggest that D. salina presents higher potential for β-carotene accumulation and that high salinity decreases cellular concentration (measured by the parameter Xm of the kinetic model proposed);however there is an increase in β-carotene production. © 2010 Science Publications.

关键词： Microalgae

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Detection of signal drifts by different control charts

Detection of signal drifts by different control charts

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作者： Friebel, T. Haber, R. University of Applied Science Institute of Process Engineering and Plant Design Laboratory of Process Control Cologne D-50679 Köln Germany

ISBN: (纸本)9783902661661

Quality control charts like Shewhart CUSUM, MA and EWMA control charts are widely used in the industry. control charts are often implemented in statistical process control software packages and are used in conditioning monitoring for fault detection. The functional principle of the control charts is shown and explained through a simple example. The sensitivity of the different control charts to mean value and standard deviation shifts and different parameters are compared. And it is shown that the CUSUM control chart is the best. With some different applications it is shown how easy is it to detect a shift or drift in industrial data. The applications presented are gas concentration measurement and milk production. Also the problem to calculate the correct standard deviation for a sensor system is dealt with.

关键词： control charts

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Heat exchanger fouling detection and lifetime estimation by regression

Heat exchanger fouling detection and lifetime estimation by ...

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作者： Friebel, T. Stockmann, M. Haber, R. Department of Process Engineering and Plant Design Laboratory of Process Control Cologne University of Applied Science Betzdorfer Str. 2 D-50679 Köln Germany

ISBN: (纸本)9783902661661

Fault detection begins with the detection of a drift at an observed attribute from a sensor, machine or process. Several methods exist to detect such faults before they appear. In this paper it is shown how to predict the lifetime until a detected disturbance reaches a tolerance level and becomes a fault. The remaining lifetime is estimated by linear trend regression. The quality of regression is validated by two hypothesis tests, the F-and the t-test. The uncertainty of the lifetime is calculated considering the confidence interval of the parameter estimation. The power of this method is shown by a simulated case study of heat exchanger fouling detection. An explicit differentiation and identification between normal fluid temperature changes and fouling can be made. In addition, under the knowledge of remaining lifetime the maintenance can be planed in periods of normal production breaks.

关键词： Fouling

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Pattern recognition for valve stiction detection with principal component analysis

Pattern recognition for valve stiction detection with princi...

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7th IFAC International Symposium on Fault Detection, Supervision and Safety of Technical Systems, SAFEprocess'09

作者： Stockmann, M. Haber, R. Schmitz, U. Department of Process Engineering and Plant Design Laboratory of Process Control Cologne University of Applied Science Betzdorfer Str. 2 D-50679 Köln Germany Shell Germany Oil GmbH Rheinland Raffinerie Germany

ISBN: (纸本)9783902661463

Static friction (stiction) in control valves is an often unrecognized problem which can lead to oscillating process variables. Therefore it is important to detect stiction at an early stage as the reason for oscillation. This work presents a new and robust method which uses the pattern recognition with principal component analysis for stiction detection. © 2009 IFAC.

关键词： Principal component analysis

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Comparison of data and model based sensor data pre-treatment in a hydrocracker

Comparison of data and model based sensor data pre-treatment...

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ISBN: (纸本)9783902661661

Defect or non-available measurements due to damaged sensors or transmitters in chemical processes may lead to disastrous effects on quality and safety. In this work, a hydro-cracker is dealt with where faulty measurements may cause the cooling of the entire reactor and producing of low quality rejections. First, some state of the art data based methods are presented for outlier detection and data imputation. These methods assume some conditions (e.g. Gaussian distribution) which were not fulfilled in the presented plant. Therefore, two new model based methods were developed which allow to detect and to give an option to substitute outliers or non-available measurements in the quench of a hydro-cracker.

关键词： Fault detection

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Detection of signal drifts by different control charts

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IFAC Proceedings Volumes 2009年第19期42卷 432-437页

作者： T. Friebel R. Haber University of Applied Science Institute of Process Engineering and Plant Design Laboratory of Process Control Cologne D-50679 Köln (fax: +49/221/8275-2836)

Abstract Quality control charts like Shewhart CUSUM, MA and EWMA control charts are widely used in the industry. control charts are often implemented in statistical process control software packages and are used in conditioning monitoring for fault detection. The functional principle of the control charts is shown and explained through a simple example. The sensitivity of the different control charts to mean value and standard deviation shifts and different parameters are compared. And it is shown that the CUSUM control chart is the best. With some different applications it is shown how easy is it to detect a shift or drift in industrial data. The applications presented are gas concentration measurement and milk production. Also the problem to calculate the correct standard deviation for a sensor system is dealt with.

关键词： quality control charts statistical process control fault detection CUSUM Shewhart

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Heat exchanger fouling detection and lifetime estimation by regression

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IFAC Proceedings Volumes 2009年第19期42卷 471-476页

作者： T. Friebel M. Stockmann R. Haber Department of Process Engineering and Plant Design Laboratory of Process Control Cologne University of Applied Science D-50679 Köln Betzdorfer Str. 2 Germany fax: +49/221/8275-2836

Abstract Fault detection begins with the detection of a drift at an observed attribute from a sensor, machine or process. Several methods exist to detect such faults before they appear. In this paper it is shown how to predict the lifetime until a detected disturbance reaches a tolerance level and becomes a fault. The remaining lifetime is estimated by linear trend regression. The quality of regression is validated by two hypothesis tests, the F- and the t-test. The uncertainty of the lifetime is calculated considering the confidence interval of the parameter estimation. The power of this method is shown by a simulated case study of heat exchanger fouling detection. An explicit differentiation and identification between normal fluid temperature changes and fouling can be made. In addition, under the knowledge of remaining lifetime the maintenance can be planed in periods of normal production breaks.

关键词： fault detection heat exchanger fouling linear regression F-test t-test remaining lifetime

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Comparison of data and model based sensor data pre-treatment in a hydro-cracker

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IFAC Proceedings Volumes 2009年第19期42卷 379-384页

作者： M. Stockmann R. Haber U. Schmitz Department of Process Engineering and Plant Design Laboratory of Process Control Cologne University of Applied Science D-50679 Köln Betzdorfer Str. 2 Germany fax: +49-221-8275-2836 Shell Germany Oil GmbH Rheinland Raffinerie

Abstract Defect or non-available measurements due to damaged sensors or transmitters in chemical processes may lead to disastrous effects on quality and safety. In this work, a hydro-cracker is dealt with where faulty measurements may cause the cooling of the entire reactor and producing of low quality rejections. First, some state of the art data based methods are presented for outlier detection and data imputation. These methods assume some conditions (e.g. Gaussian distribution) which were not fulfilled in the presented plant. Therefore, two new model based methods were developed which allow to detect and to give an option to substitute outliers or non-available measurements in the quench of a hydro-cracker.

关键词： Fault detection Outlier Physical models Missing value imputation Hydro-cracking

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