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Closed-loop Scheduling in a canned food factory

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IFAC-PapersOnLine 2020年第2期53卷 10791-10796页

作者： C.G. Palacín C. Vilas A.A. Alonso José L. Pitarch C. de Prada Systems engineering and Automatic Control Dpt. University of Valladolid Valladolid Spain (Bio)Process engineering Group Instituto de Investigaciones Marinas (CSIC) Vigo Spain

This paper addresses the problem of closed-loop operation of scheduling, together with the interaction of control and scheduling, for a class of processes that appear very often in industry: those that combine continuous production lines with parallel batch units that share some resources. The paper presents a novel approach to this problem, including batching and a new type of precedence in the assignment problem. It also considers the effect of shared resources on the duration of the cycle time of the batch units. The approach is illustrated with a real-life example of a canned tuna factory

关键词： Integration of scheduling control shared resources tuna cans sterilisation process optimisation continuous-batch process scheduling

Encrypted Cooperative control Revisited 58

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Encrypted Cooperative Control Revisited

58th IEEE Conference on Decision and control, CDC 2019

作者： Alexandru, Andreea B. Schulze Darup, Moritz Pappas, George J. University of Pennsylvania Department of Electrical and Systems Engineering United States Universität Paderborn Automatic Control Group Germany

ISBN: (纸本)9781728113982

Distributed systems are ubiquitous in present-day technologies like smart cities. Such applications require decentralized control, which reduces the load on a single central party, but requires communication and data sharing between the participating agents. However, agents might not trust their peers with their private data. We propose secure multi-party computation schemes that ensure the private computation of the control updates of each agent, without leaking any other information about the states and controls of their neighbors. To this end, we make use of homomorphic encryption and private sum aggregation schemes. We analyze the conditions such that a dishonest agent cannot observe the rest of the network. Finally, we present implementations of the proposed schemes and showcase their efficiency. © 2019 IEEE.

关键词： Cryptography

Distributed control of Second-Order Multi-Agent systems:Fractional Integral Action and Consensus

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Distributed Control of Second-Order Multi-Agent Systems:Frac...

第三十九届中国控制会议

作者： Ricardo Cajo Shiquan Zhao Douglas Plaza Robain De Keyser Clara Ionescu Ghent University Research group on Dynamical Systems and Control Harbin Engineering University College of Automation Technical University of Cluj-Napoca Department of Automatic Control

This article addresses the consensus problem in multi-agent systems modeled with double-integrator dynamics under constant disturbances. Therefore, a fractional control protocol to enhance the convergence speed and robustness of the system is proposed. The communication topology of the system is represented by an undirected connected graph. In addition, the convergence of the system is analyzed with the stability boundary locus method, through which analytical expressions are deduced to ensure the stability of the agents group. Finally, an example is provided to illustrate the validity of the theoretical results.

关键词： Multi-agents Consensus problem Fractional calculus Distributed control Double-integrator dynamics

II. The effect of axisymmetric and spatially varying equilibria and flow on mhd wave modes: Cylindrical geometry

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arXiv 2021年

作者： Skirvin, Samuel Fedun, Viktor Silva, Suzana Verth, Gary Plasma Dynamics Group Department of Automatic Control & Systems Engineering University of Sheffield SheffieldS3 7RH United Kingdom Plasma Dynamics Group Department of Mathematics and Statistics University of Sheffield SheffieldS3 7RH United Kingdom

Magnetohydrodynamic (MHD) waves are routinely observed in the solar atmosphere. These waves are important in the context of solar physics as it is widely believed they can contribute to the energy budget of the solar atmosphere and are a prime candidate to contribute towards coronal heating. Realistic models of these waves are required representing observed configurations such that plasma properties can be determined more accurately which can not be measured directly. This work utilises a previously developed numerical technique to find permittable eigenvalues under different non-uniform equilibrium conditions in a Cartesian magnetic slab geometry. Here we investigate the properties of magnetoacoustic waves under nonuniform equilibria in a cylindrical geometry. Previously obtained analytical results are retrieved to emphasise the power and applicability of this numerical technique. Further case studies investigate the effect that a radially non-uniform plasma density and non-uniform plasma flow, modelled as a series of Gaussian profiles, has on the properties of different MHD waves. For all cases the dispersion diagrams are obtained and spatial eigenfunctions calculated which display the effects of the equilibrium inhomogeneity. It is shown that as the equilibrium non-uniformity is increased, the radial spatial eigenfunctions are affected and extra nodes introduced, similar to the previous investigation of a magnetic slab. Furthermore, azimuthal perturbations are increased with increasing inhomogeneity introducing vortical motions inside the waveguide. Finally, 2D and 3D representations of the velocity fields are shown which may be useful for observers for wave mode identification under realistic magnetic waveguides with ever increasing instrument resolution. © 2021, CC BY.

关键词： Magnetohydrodynamics

Modeling the effects of a lightbridge on oscillations in a solar pore

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arXiv 2024年

作者： Schiavo, Luiz A.C.A. Gordovskyy, Mykola Browning, Philippa Silva, Suzana S.A. Verth, Gary Ballai, Istvan Shelyag, Sergiy Ruzheinikov, Sergey N. McLaughlin, James A. Fedun, Viktor Department of Mathematics Physics and Electrical Engineering Northumbria University NewcastleNE1 8ST United Kingdom Centre for Astrophysics Research Department of Physics Astronomy & Mathematics University of Hertfordshire HatfieldAL10 9AB United Kingdom Jodrell Bank Centre for Astrophysics University of Manchester ManchesterM13 9PL United Kingdom Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Hounsfield Road SheffieldS3 7RH United Kingdom College of Science and Engineering Flinders University TonsleySA5042 Australia

Solar pores are ideal magnetic structures for wave propagation and transport of energy radially-outwards across the upper layers of the solar atmosphere. We aim to model the excitation and propagation of magnetohydrodynamic waves in a pore with a lightbridge modelled as two interacting magnetic flux tubes separated by a thin, weaker field, layer. We solve the three-dimensional MHD equations numerically and calculate the circulation as a measure of net torsional motion. We find that the interaction between flux tubes results in the natural excitation of propagating torsional Alfvén waves, but find no torsional waves in the model with a single flux tube. The torsional Alfvén waves propagate with wave speeds matching the local Alfvén speed where wave amplitude peaks. Copyright © 2024, The Authors. All rights reserved.

关键词： Plasma magnetohydrodynamic waves

The effect of linear background rotational flows on magnetoacoustic modes of a photospheric magnetic flux tube

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arXiv 2022年

作者： Skirvin, Samuel J. Fedun, Viktor Silva, Suzana S.A. Van Doorsselaere, Tom Claes, Niels Goossens, Marcel Verth, Gary Centre for mathematical Plasma Astrophysics Mathematics Department KU Leuven Celestijnenlaan 200B bus 2400 LeuvenB-3001 Belgium Plasma Dynamics Group Department of Automatic Control & Systems Engineering The University of Sheffield SheffieldS3 7RH United Kingdom Plasma Dynamics Group Department of Mathematics and Statistics The University of Sheffield SheffieldS3 7RH United Kingdom

Magnetoacoustic waves in solar magnetic flux tubes may be affected by the presence of background rotational flows. Here, we investigate the behaviour of m = 0 and m = ±1 modes of a magnetic flux tube in the presence of linear background rotational flows embedded in a photospheric environment. We show that the inclusion of a background rotational flow is found to have little effect on the obtained eigensolutions for the axisymmetric m = 0 sausage mode. However, solutions for the kink mode are dependent on the location of the flow resonance modified by the slow frequency. A background rotational flow causes the modified flow resonances to possess faster phase speeds in the thin-tube (TT) limit for the case m = 1. This results in solutions for the slow body and slow surface kink modes to follow this trajectory, changing their dispersive behaviour. For a photospheric flux tube in the TT limit, we show that it becomes difficult to distinguish between the slow surface and fast surface kink (m = 1) modes upon comparison of their eigenfunctions. 2D velocity field plots demonstrate how these waves, in the presence of background rotational flows, may appear in observational data. For slow body kink modes, a swirling pattern can be seen in the total pressure perturbation. Furthermore, the tube boundary undergoes a helical motion from the breaking of azimuthal symmetry, where the m = 1 and m = −1 modes become out of phase, suggesting the resulting kink wave is circularly polarised. These results may have implications for seismology of magnetohydrodynamic waves in solar magnetic vortices. © 2022, CC BY.

关键词： Magnetohydrodynamics

Waves in weakly ionised solar plasmas

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arXiv 2022年

作者： Alharbi, Abdulaziz Ballai, I. Fedun, V. Verth, G. Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Hounsfield Road Hicks Building SheffieldS3 7RH United Kingdom Department of Mathematics Jamoum University College Umm Al-Qura University Jamoum Makkah25375 Saudi Arabia Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom

Here we study the nature and characteristics of waves propagating in partially ionised plasmas in the weakly ionised limit, typical for the lower part of the solar atmosphere. The framework in which the properties of waves are discussed depends on the relative magnitude of collisions between particles, but also on the relative magnitude of the collisional frequencies compared to the gyro-frequency of charged particles. Our investigation shows that the weakly ionised solar atmospheric plasma can divided into two regions and this division occurs, roughly, at the base of the chromosphere. In the solar photosphere the plasma is non-magnetised and the dynamics can described within the three-fluid framework where acoustic waves associated to each species can propagate. Due to the very high concentration of neutrals, the neutral sound waves propagates with no damping, while for the other two modes the damping rate is determined by collisions with neutrals. The ion and electron-related acoustic modes propagate with a cut-off determined by the collisional frequency of these species with neutrals. In the weakly ionised chromosphere only electrons are magnetised, however, the strong coupling of charged particles reduces the working framework to a two-fluid model. The disassociation of charged particles creates electric currents that can influence the characteristic of waves. The propagation properties of waves with respect to the angle of propagation are studied with the help of polar diagrams. Copyright © 2022, The Authors. All rights reserved.

关键词： Damping

Comparison of exact and approximate MHD slow body mode solutions in photospheric waveguides

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arXiv 2022年

作者： Aldhafeeri, Anwar A. Verth, Gary Fedun, Viktor Lennard, Matthew Ballai, Istvan Mathematics and Statistic Department Faculty of Science King Faisal University Al-Hassa P.O. Box 400 Hofuf31982 Saudi Arabia Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Plasma Dynamics Group Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom

In this study we explore the possibility of simplifying the modeling of magnetohydrodynamic (MHD) slow body modes observed in photospheric magnetic structure such as the umbrae of sunspots and pores. The simplifying approach assumes that the variation of the eigenvalues of slow body waves can be derived by imposing that the longitudinal component of velocity with respect to the tube axis is zero at the boundary of the magnetic flux tube, which is in a good agreement with observations. To justify our approach we compare the results of our simplified model for slow body modes in cylindrical flux tubes with the model prediction obtained by imposing the continuity of the radial component of the velocity and total pressure at the boundary of the flux tube. Our results show that, to a high accuracy (less than 1% for the considered model), the conditions of continuity of the component of transversal velocity and pressure at the boundary can be neglected when modelling slow body modes under photospheric conditions. © 2022, CC BY.

关键词： Magnetohydrodynamics

New approach for analysing dynamical processes on the surface of photospheric vortex tubes

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arXiv 2022年

作者： Aljohani, Yasir Fedun, Viktor Ballai, Istvan Silva, Suzana S.A. Shelyag, Sergiy Verth, Gary Plasma Dynamics Group School of Mathematics and Statistics University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Department of Mathematics Jamoum University College Umm Al-Qura University Jamoum Makkah25375 Saudi Arabia Plasma Dynamics Group Department of Automatic Control and Systems Engineering University of Sheffield Mappin Street SheffieldS1 3JD United Kingdom School of Information Technology Deakin University Geelong Australia

The majority of studies on multi-scale vortex motions employ a two-dimensional geometry by using a variety of observational and numerical data. This approach limits the understanding the nature of physical processes responsible for vortex dynamics. Here we develop a new methodology to extract essential information from the boundary surface of vortex tubes. 3D high-resolution magnetoconvection MURaM numerical data has been used to analyse photospheric intergranular velocity vortices. The Lagrangian Averaged Vorticity Deviation (LAVD) technique was applied to define the centers of vortex structures and their boundary surfaces based on the advection of fluid elements. These surfaces were mapped onto a constructed envelope grid that allows the study of the key plasma parameters as functions of space and time. Quantities that help in understanding the dynamics of the plasma, e.g. Lorentz force, pressure force, plasma-β were also determined. Our results suggest that, while density and pressure have a rather global behaviour, the other physical quantities undergo local changes, with their magnitude and orientation changing in space and time. At the surface, the mixing in the horizontal direction is not efficient, leading to appearance of localized regions with higher/colder temperatures. In addition, the analysis of the MHD Poynting flux confirms that the majority of the energy is directed in the horizontal direction. Our findings also indicate that the pressure and magnetic forces that drive the dynamics of the plasma on vortex surfaces are unbalanced and therefore the vortices do not rotate as a rigid body. Copyright © 2022, The Authors. All rights reserved.

关键词： Vortex flow