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Identification and optimal control of fructo-oligosaccharide production

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IFAC-PapersOnLine 2018年第18期51卷 678-683页

作者： Schorsch, J. Kinnaert, M. Fekih-Salem, R. Dewasme, L. Castro, C.C. Wouwer, A. Vande Department of Control Engineering and System Analysis Université libre de Bruxelles Belgium Automatic Control Laboratory University of Mons Belgium LAMSIN University of Tunis El Manar Tunisia Applied Chemistry and Biochemistry Department University of Mons Belgium

This article deals with the development of a reduced model describing the temporal evolution of the fructo-oligosaccharide production by Aureobasidium pullulans and the optimal process control. First, a reduced model is derived from a detailed model reproducing with good accuracy the dynamics of the fructo-oligosaccharide production. The reduced model is obtained using maximum likelihood principal component analysis and parameter identification based on a weighted least squares criterion. Next, the fructo-oligosaccharide concentration at an a priori undetermined time is maximized using Pontryagin maximum principle. The methodology is analyzed based on experimental data from batch and fed-batch cultures, and results are compared with those obtained with another simple model available in the literature. © 2018

关键词： Maximum likelihood estimation Bang bang control systems Batch cell culture Biotechnology Maximum principle Oligosaccharides Parameter estimation Principal component analysis Aureobasidium pullulans Bang Bang control Detailed modeling Fed batch cultures Fructo oligosaccharides Optimal controls Temporal evolution Weighted least squares

The importance of horizontal Poynting flux in the solar photosphere

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arXiv 2022年

作者： Silva, Suzana S.A. Murabito, Mariarita Jafarzadeh, Shahin Stangliani, Marco Verth, Gary Ballai, Istvan Fedun, Viktor Plasma Dynamics Group Department of Automatic Control and Systems Engineering University of Sheffield Sheffield United Kingdom Department of Physics Aeronautics Institute of Technology São José dos Campos Brazil INAF - Osservatorio Astronomico di Roma Via Frascati33 Monte Porzio Catone RM 00078 Italy Max Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 Göttingen37077 Germany Rosseland Centre for Solar Physics University of Oslo P.O. Box 1029 Blindern OsloNO-0315 Norway ASI Italian Space Agency Via del Politecnico snc Rome00133 Italy Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Sheffield United Kingdom

The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching 1010 erg cm−2 s−1. To validate our findings, we extended the analysis to SUNRISE/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Unexpected frequency of horizontal oscillations of magnetic structures in the solar photosphere

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arXiv 2024年

作者： Berretti, M. Stangalini, M. Verth, G. Jafarzadeh, S. Jess, D.B. Berrilli, F. Grant, S.D.T. Duckenfield, T. Fedun, V. University of Trento Via Calepina 14 Trento38122 Italy University of Rome Tor Vergata Department of Physics Via della Ricerca Scientifica 3 Rome00133 Italy ASI Italian Space Agency Via del Politecnico snc Rome00133 Italy Plasma Dynamics Group School of Mathematics and Statistics The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Max Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 Göttingen37077 Germany Niels Bohr International Academy Niels Bohr Institute Blegdamsvej 17 CopenhagenDK-2100 Denmark Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast Northern Ireland BelfastBT7 1NN United Kingdom Department of Physics and Astronomy California State University Northridge NorthridgeCA91330 United States Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom

It is well known that the dominant frequency of oscillations in the solar photosphere is ≈3 mHz, which is the result of global resonant modes pertaining to the whole stellar structure. However, analyses of the horizontal motions of nearly 1 million photospheric magnetic elements spanning the entirety of solar cycle 24 have revealed an unexpected dominant frequency, ≈5 mHz, a frequency typically synonymous with the chromosphere. Given the distinctly different physical properties of the magnetic elements examined in our statistical sample, when compared to largely quiescent solar plasma where ≈3 mHz frequencies are omnipresent, we argue that the dominant ≈5 mHz frequency is not caused by the buffeting of magnetic elements, but instead is due to the nature of the underlying oscillatory driver itself. This novel result was obtained by exploiting the unmatched spatial and temporal coverage of magnetograms acquired by the Helioseismic and Magnetic Imager (HMI) on board NASA’s Solar Dynamics Observatory (SDO). Our findings provide a timely avenue for future exploration of the magnetic connectivity between sub-photospheric, photospheric, and chromospheric layers of the Sun’s dynamic atmosphere. Copyright © 2024, The Authors. All rights reserved.

关键词： Magnetic structure

Estimation and control of oscillators through short-range noisy proximity measurements

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arXiv 2019年

作者： Iudice, Francesco Lo Acosta, José Ángel Garofalo, Franco DeLellis, Pietro Department of Electrical Engineering and Information Technology University of Naples Federico II Naples80125 Italy Department of Automatic Control and System Engineering University of Sevilla Sevilla41004 Spain

In this paper, we present a novel estimation and control strategy to balance a formation of discrete-time oscillators on a circle. We consider the case in which each oscillator only gathers noisy proximity measurements, whose range is lower than the desired spacing along the circle, implying total disconnectedness of the balanced formation. These restrictions pose relevant challenges that are overcome through the symbiotic combination of an estimator that borrows tools from interval analysis and a three-level bang-bang controller. We prove that the formation can be balanced, with an accuracy that can be regulated by tuning a controller parameter. The effectiveness of the proposed strategy is further illustrated through a set of numerical *** Codes 93A14, 94A30 Copyright © 2019, The Authors. All rights reserved.

关键词： controllers

Development of Smartphone Apps for Skin Cancer Risk Assessment: Progress and Promise

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JMIR Dermatology

JMIR Dermatology 2019年第1期2卷

作者： de Carvalho, Tiago M. Noels, Eline Wakkee, Marlies Udrea, Andreea Nijsten, Tamar Department of Dermatology Erasmus Medical Center Rotterdam Netherlands Department of Automatic Control and System Engineering Polytechnic University of Bucharest Bucharest Romania

Skin cancer is a growing public health problem. Early and accurate detection is important, since prognosis and cost of treatment are highly dependent on cancer stage at detection. However, access to specialized health care professionals is not always straightforward, and population screening programs are unlikely to become implemented. Furthermore, there is a wide margin for improving the efficiency of skin cancer diagnostics. Specifically, the diagnostic accuracy of general practitioners and family physicians in differentiating benign and malignant skin tumors is relatively low. Both access to care and diagnostic accuracy fuel interest in developing smartphone apps equipped with algorithms for image analyses of suspicious lesions to detect skin cancer. Based on a recent review, seven smartphone apps claim to perform image analysis for skin cancer detection, but as of October 2018, only three seemed to be active. These apps have been criticized in the past due to their lack of diagnostic accuracy. Here, we review the development of the SkinVision smartphone app, which has more than 900,000 users worldwide. The latest version of the SkinVision app (October 2018) has a 95% sensitivity (78% specificity) for detection of skin cancer. The current accuracy of the algorithm may warrant the use of this app as an aid by lay users or general practitioners. Nonetheless, for mobile health apps to become broadly accepted, further research is needed on their health impact on the health system and the user population. Ultimately, mobile health apps could become a powerful tool to reduce health care costs related to skin cancer management and minimize the morbidity of skin cancer in the population. ©Tiago M de Carvalho, Eline Noels, Marlies Wakkee, Andreea Udrea, Tamar Nijsten.

关键词： early detection mhealth mobile phone skin cancer smartphone app

A Hierarchical Architecture for the Coordination of an Ensemble of Steam Generators

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arXiv 2020年

作者： Spinelli, Stefano Longoni, Elia Farina, Marcello Petzke, Felix Streif, Stefan Ballarino, Andrea Dipartimento di Elettronica Informazione e Bioingegneria Politecnico di Milano Italy Istituto di Sistemi e Tecnologie Industriali Intelligenti per il Manifatturiero Avanzato Consiglio Nazionale delle Ricerche Italy Department of Electrical Engineering and Information Technology Technische Universita't Chemnitz Automatic Control and System Dynamics Lab Germany

This work presents a hierarchical architecture for the optimal management of an ensemble of steam generators, which needs to jointly sustain a common load. The coordination of independent subsystems is provided by a multi—layer control scheme. A high—level optimizer computes the optimal shares of production to be allocated to single generators. At medium level, a robust tube—based model predictive control (MPC) is proposed to track the time—varying demand of the ensemble using a centralized, but aggregated model, whose order does not scale with the number of subsystems. At low level, decentralized controllers are in place to stabilize the internal boiler pressure. The control architecture enables the dynamic modification of the ensemble configuration and plug and play operations. Simulation results are reported to demonstrate the potentialities of the proposed approach. Copyright © 2020, The Authors. All rights reserved.

关键词： Model predictive control

Supplementary material for CDC submission no. 1461

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arXiv 2020年

作者： Ju, Yue Chen, Tianshi Mu, Biqiang Ljung, Lennart Chinese University of Hong Kong Shenzhen518172 Hong Kong School of Science and Engineering Shenzhen Research Institute of Big Data Chinese University of Hong Kong Shenzhen518172 Hong Kong Key Laboratory of Systems and Control Institute of Systems Science Academy of Mathematics and System Science Chinese Academy of Sciences Beijing100190 China Division of Automatic Control Department of Electrical Engineering Linköping University LinköpingSE-58183 Sweden

In this paper, we study the influence of ill-conditioned regression matrix on two hyper-parameter estimation methods for the kernel-based regularization method: the empirical Bayes (EB) and the Stein’s unbiased risk estimator (SURE). First, we consider the convergence rate of the cost functions of EB and SURE, and we find that they have the same convergence rate but the influence of the ill-conditioned regression matrix on the scale factor are different: the scale factor for SURE contains one more factor cond(ΦTΦ) than that of EB, where Φ is the regression matrix and cond(·) denotes the condition number of a matrix. This finding indicates that when Φ is ill-conditioned, i.e., cond(ΦTΦ) is large, the cost function of SURE converges slower than that of EB. Then we consider the convergence rate of the optimal hyper-parameters of EB and SURE, and we find that they are both asymptotically normally distributed and have the same convergence rate, but the influence of the ill-conditioned regression matrix on the scale factor are different. In particular, for the ridge regression case, we show that the optimal hyper-parameter of SURE converges slower than that of EB with a factor of 1/n2, as cond(ΦTΦ) goes to ∞, where n is the FIR model order. Copyright © 2020, The Authors. All rights reserved.

关键词： Cost functions

Simultaneous Search and Monitoring of Evasive Targets by an Unmanned Aerial Vehicle

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Simultaneous Search and Monitoring of Evasive Targets by an ...

UKACC International Conference on control (control)

作者： Haoyu Zhang Sandor M. Veres Department of Automatic Control and System Engineering The University of Sheffield

This paper studies a Simultaneous Search and Monitoring (SSM) problem between an aerial pursuer and multiple evasive ground targets. The adversarial target behaviours and the partial observation by the pursuer make this problem a Partially Observable Stochastic Game (POSG). Because of the intractability of obtaining an exact solution, we applied some assumptions on the information available to the targets. These assumptions simplify the game playing into a dynamic Guaranteed Search problem. A policy planning algorithm was designed for the pursuer, which achieved efficient Simultaneous Search and Monitoring and reduced the total uncertainty level. The comparative study validated the advantages of our policy planning over conventional fixed-pattern Guaranteed Search method.

关键词： Planning Games Linear programming Monitoring Search problems Uncertainty Time measurement

A Formal Sensitivity Analysis for Laguerre Based Predictive Functional control

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A Formal Sensitivity Analysis for Laguerre Based Predictive ...

UKACC International Conference on control (control)

作者： Muhammad Abdullah John Anthony Rossiter Department of Automatic Control and System Engineering University of Sheffield UK

A Laguerre Predictive Functional control (LPFC) is a simple input shaping method, which can improve the prediction consistency and closed-loop performance of the conventional approach (PFC). However, it is well-known that an input shaping method, in general, will affect the loop sensitivity of a system. Hence, this paper presents a formal sensitivity analysis of LPFC by considering the effect of noise, unmeasured disturbance and parameter uncertainty. Sensitivity plots from bode diagrams and closed-loop simulation are used to illustrate the controller robustness and indicate that although LPFC often provides a better closed-loop tracking response and disturbance rejection, this may involve some trade-off with the sensitivity to noise and parameter uncertainty. Finally, to validate the practicality of the results, the sensitivity of the LPFC control law is illustrated on real-time laboratory hardware.

关键词： Predictive models Sensitivity analysis Uncertain systems Trajectory Frequency measurement Robustness