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arXiv 2020年

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

The plasma dynamics at frequencies comparable with collisional frequency between various species has to be described in multi-fluid framework, where collisional interaction between particles is an important ingredient. In our study we will assume that charged particles are strongly coupled, meaning that they form a single fluid that interacts with neutrals, therefore we will employ a two-fluid model. Here we aim to investigate the evolutionary equation of slow sausage waves propagating in a gravitationally stratified flux tube in the two-fluid solar atmosphere in a strongly ionised limit using an initial value analysis. Due to the collisional interaction between massive particles (ions and neutrals) the governing equations are coupled. Solutions are sought in the strongly ionised limit and the density ratio between neutrals and charged particles is a small parameter. This limit is relevant to the upper part of the chromosphere. Our results show that slow sausage waves associated with charged particles propagate such that their possible frequency is affected by a cut-off due to the gravitational stratification. In contrast, for neutral acoustic waves the cut-off value applies on their wavelength and only small wavelength waves are able to propagate. Slow modes associated to neutrals are driven by the collisional coupling with ions. © 2020, CC0.

关键词： Magnetohydrodynamics

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Chattering-free fixed-time sliding mode control for bilateral teleoperation under unknown time-varying delay via disturbance and state observers

Advanced Control for Applications: Engineering and Industria...

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Advanced control for Applications: engineering and Industrial systems 2020年第4期2卷

作者： Abadi, Ali Soltani Sharif Hosseinabadi, Pooyan Alinaghi Mekhilef, Saad Ordys, Andrzej Department of Electrical Engineering Faculty of Engineering Yazd University Yazd Iran Faculty of Engineering University of Malaya Kuala Lumpur Malaysia School of Software and Electrical Engineering Faculty of Science Engineering and Technology Swinburne University of Technology Melbourne Australia Center of Research Excellence in Renewable Energy and Power Systems King Abdulaziz University Jeddah Saudi Arabia The Institute of Automatic Control and Robotics Faculty of Mechatronics Warsaw University of Technology Warsaw Poland

This paper proposes a new chattering-free Fixed-time Observer-Based Sliding Mode control (FOBSMC) scheme for synchronization of two bilateral teleoperations under unknown time-varying delay. The system is subjected to unknown disturbances which are estimated in a fixed time by utilizing the Disturbance Observer-based SMC scheme. The fixed-time State Observer-based SMC is designed to estimate the unmeasured velocity state, while the position state is assumed to be available. Fixed-time stability method is used to provide the system convergence time independently of initial states. A FOBSMC scheme is first designed for master system of bilateral teleoperation under unknown time-varying delay to track the environmental torque by the human operating torque in the presence of time delay in the communication channel, as well as estimating the unknown disturbances and unmeasured states. A FOBSMC scheme is designed to synchronize slave system to master system in the presence of time delay in the communication channel, as well as estimating disturbances and states. The stability analysis is performed for closed-loop system of combined controller-observer by using Lyapunov theory. The efficacy of the proposed method to fulfill a good transparency and stability under time-varying communication delays is tested by performing numerical simulation in Simulink/MATLAB. © 2020 John Wiley & Sons Ltd.

关键词： Time delay

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Infinitesimal Weak Rigidity and Stability Analysis on Three-Agent Formations 57

Infinitesimal Weak Rigidity and Stability Analysis on Three-...

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57th Annual Conference of the Society of Instrument and control Engineers of Japan, SICE 2018

作者： Kwon, Seong-Ho Trinh, Minh Hoang Oh, Koog-Hwan Zhao, Shiyu Ahn, Hyo-Sung School of Mechanical Engineering Gwangju Korea Republic of Department of Automatic Control and Systems Engineering University of Sheffield United Kingdom

ISBN: (纸本)9784907764609

In this paper, new concepts of weak rigidity matrix and infinitesimal weak rigidity for planar frameworks are introduced. The weak rigidity matrix is used to directly check if a framework is infinitesimally weakly rigid while previous work can check a weak rigidity of a framework indirectly. An infinitesimal weak rigidity framework can be uniquely determined up to a translation and a rotation (and a scaling also when the framework does not include any edge) by its inter-neighbor distances and angles. We propose applying the new concepts to a three-agent formation control problem with a gradient control law, and further we finally propose a modified Henneberg construction which is a technique to generate minimally rigid (or weakly rigid) graphs. © 2018 The Society of Instrument and control Enginners - SICE.

关键词： Rigidity

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Facial temperature markers for mental stress assessment in human-machine interface (HMI) control system 15

Facial temperature markers for mental stress assessment in h...

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15th International Conference on Informatics in control, Automation and robotics, ICINCO 2018

作者： He, Changjiang Mahfouf, M. Torres-Salomao, L.A. Automatic Control and Systems Engineering Department University of Sheffield Sheffield United Kingdom Digital Systems and Solutions General Electric Infraestructure Queretaro Queretaro Mexico

ISBN: (纸本)9789897583216

Mental state prediction is of great importance to human-machine interface (HMI) as far as both safety and reliability are concerned. In this paper, the use of facial temperature changes for predicting mental stress has been investigated. A carefully designed experiment of HMI has been performed on seven (7) healthy subjects, and the statistical analysis of the results has been provided, and the effectiveness of using facial temperature with the thermal camera to estimate the human mental stress has been established. The biomarkers developed from the data of facial temperature have exhibited a similar or even better ability to differentiate between the mental stress levels in comparison with the traditional biomarkers (e.g. heart rate variability (HRV), task load index (TLI) and pupil size). The mean nasal temperature has been shown to be sensitive to changes in the mental state, and the maximum facial temperature and the mean forehead temperature have also shown clear correlations with mental stress and task performance. Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

关键词： Biomarkers

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Neuro-Adaptive Learning Approach for Predicting Production Performance and Pressure Dynamics of Gas Condensation Reservoir

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IFAC-PapersOnLine 2019年第29期52卷 122-127页

作者： Aliyuda Ali Lingzhong Guo Department of Automatic Control and Systems Engineering University of Sheffield Sheffield. S10 2TN UK Department of Mathematics and Computer Science Gombe State University P.M.B. 127 Gombe Nigeria

In Reservoir engineering, state-of-the-art data analysis enables engineers to characterize reservoirs and plan for developing fields. This allows production companies to save huge amounts that would otherwise be allocated to reservoir modelling and simulation and well testing. Numerical reservoir modelling and simulation is the standard use in industries today for comprehensive study of fields. However, the inflexible behaviour, development time and cost of numerical simulators are major challenges to production engineers, managers as well as modellers. On the other hand, Artificial Intelligence (AI) based reservoir models are characterised with low cost of development, short development time and fast tract analysis and flexibility to estimate the uncertainties normally found in numerical simulators. In this study, a strategy for controlling gas production and pressure drop in gas condensate reservoir is described. Numerical simulations of production rate and pressure drop were carried out first and their results were saved. An Adaptive Neuro-Fuzzy system was then developed and trained with some parts of the numerical simulation results. This AI-based system is checked and tested with part of the numerical simulation results that had not been used during the training. The developed system regenerates the numerical simulation results for both production rates and pressure drop at different Bottom Hole Pressures (BHPs) with very high accuracy (>98%). Results of this study showed that AI-based reservoir simulation can be considered a vital tool of help to production engineers, managers and modellers for a quick and more informed decision as regards field development plans that can meet operational targets.

关键词： Gas condensate reservoirs Neuro-Adaptive Learning System Bottom-Hole Pressure

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Assessment strategy of human upper forearm inter-relation and muscle fatigue 20th

Assessment strategy of human upper forearm inter-relation an...

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20th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2017

作者： Wan Daud, W.M.B. Abas, N. Tokhi, M.O. Department of Automatic Control and Systems Engineering The University of Sheffield United Kingdom School of Engineering London South Bank University United Kingdom

ISBN: (纸本)9789813231047

Surface electromyography (EMG) signals classification is currently applied in various prostheses and arm controls using various classification methods. The limited robustness in practical EMG control applications has become an important matter of research consideration. The precision of EMG signal features and parameters proportionally vary with muscle fatigue (MF). The major challenge for the study is to identify the MF manifestation in the EMG signal, so that the control performance is improved. This can be done by the improvement of data collection practicality, features extraction and classification. Hence, fundamental study is performed by investigating the signals acquired from the human upper forearm (UFA) to determine muscle characteristics and to establish the inter-relationship between both muscles of the forearm and upper arm. The aim of the present study is to investigate the applicability of human UFA muscles and MF indices at various force levels of maximum voluntary contraction (MVC). EMG signals are recorded from nine (9) normally limbed subjects. The frequency domain power spectrum density (PSD) is computed in order to derive the useful characteristics of the signal. The results show that only few muscles contributes for the movement. Further analysis show that flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), extensor carpi radialis longus (ECRL), extensor digitorum communis (EDC) and biceps/triceps brachii show interesting results. © 2018 by World Scientific Publishing Co. Pte. Ltd.

关键词： Muscle

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Small-scale solar jet formation and their associated waves and instabilities

arXiv

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arXiv 2022年

作者： Skirvin, Samuel Verth, Gary González-Avilés, José Juan Shelyag, Sergiy Sharma, Rahul Guzmán, Francisco S. Ballai, Istvan Scullion, Eamon Silva, Suzana S.A. Fedun, Viktor Center for Mathematical Plasma Astrophysics Mathematics Department KU Leuven Celestijnenlaan 200B bus 2400 LeuvenB-3001 Belgium 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 The University of Sheffield Hicks Building Hounsfield Road SheffieldS3 7RH United Kingdom Investigadores por México CONACYT Servicio de Clima Espacial Méxio Laboratorio Nacional de Clima Espacial Instituto de Geofísica Unidad Michoacán Universidad Nacional Autónoma de México Antigua Carretera a Pátzcuaro 8701 Ex-Hacienda de San José de la Huerta Michoacán Morelia58190 Mexico School of Information Technology Deakin University Melbourne3125 Australia Department of Mathematics Physics and Electrical Engineering Northumbria University Newcastle upon TyneNE1 8ST United Kingdom Instituto de Física y Matemáticas Universidad Michoacana de San Nicolás de Hidalgo Edificio C3 Cd. Universitaria Morelia Michoacán 5840 Mexico

Studies on small-scale jets’ formation, propagation, evolution, and role, such as type I and II spicules, mottles, and fibrils in the lower solar atmosphere’s energetic balance, have progressed tremendously thanks to the combination of detailed observations and sophisticated mathematical modelling. This review provides a survey of the current understanding of jets, their formation in the solar lower atmosphere, and their evolution from observational, numerical, and theoretical perspectives. First, we review some results to describe the jet properties, acquired numerically, analytically and through high-spatial and temporal resolution observations. Further on, we discuss the role of hydrodynamic and magnetohydrodynamic instabilities, namely Rayleigh-Taylor and Kelvin-Helmholtz instabilities, in jet evolution and their role in the energy transport through the solar atmosphere in fully and partially ionised plasmas. Finally, we discuss several mechanisms of magnetohydrodynamic wave generation, propagation, and energy transport in the context of small-scale solar jets in detail. This review identifies several gaps in the understanding of small-scale solar jets and some misalignments between the observational studies and knowledge acquired through theoretical studies and numerical modelling. It is to be expected that these gaps will be closed with the advent of high-resolution observational instruments, such as Daniel K. Inouye Solar Telescope, Solar Orbiter, Parker Solar Probe, and Solar CubeSats for Linked Imaging Spectropolarimetry, combined with further theoretical and computational developments. © 2022, CC BY.

关键词： Magnetohydrodynamics

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Optimal control of systems with multichannel packet loss

arXiv

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arXiv 2019年

作者： Casbolt, William Jones, Bryn Esnaola, Iñaki The Department of Automatic Control and Systems Engineering University of Sheffield SheffieldS1 3JD United Kingdom The Department of Electrical Engineering Princeton University PrincetonNJ08544 United States

The performance of control systems with input packet losses on the controller to plant communication channel is analysed. The main contribution of this work is a proof that linear optimal control systems operating with UDP-like communication protocols have a larger quadratic cost than the same systems operating with TCP-like protocols. The proof is derived for the general case of multidimensional and independent actuation communication channels. In doing so, our results extend previous work to systems with multiple distributed actuators. The difference in cost between two communication protocols is analysed, enabling the maximal difference between the two protocols to be quantified. Numerical examples are presented to highlight the difference in costs induced by the choice of communication protocol. Copyright © 2019, The Authors. All rights reserved.

关键词： Packet loss

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Real-time embedded sliding mode observer for quadcopter UAVs 20th

Real-time embedded sliding mode observer for quadcopter UAVs

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20th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2017

作者： Firdaus, A.R. Tokhi, M.O. Department of Automatic Control and Systems Engineering The University of Sheffield United Kingdom School of Engineering London South Bank University United Kingdom

ISBN: (纸本)9789813231047

Sliding mode observer (SMO) as a nonlinear and robust observer, is believed to be able to provide all required states information for control process of quadcopter UAVs. In this paper, a comparative assessment through numerical simulation is conducted between SMO and Extended Kalman Filter (EKF) to demonstrate the performance of both estimators. The results obtained demonstrate good performance of SMO in dealing with noise and uncertainty. Furthermore, experiments are carried out to validate the performance of SMO in real-time. The results show that estimated states can track true states fast with small estimation steady state errors and the observer estimates the unmeasured states smoothly. © 2018 by World Scientific Publishing Co. Pte. Ltd.

关键词： Extended Kalman filters

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Denial of service attacks on control systems with packet loss

arXiv

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arXiv 2019年

作者： Casbolt, William Esnaola, Iñaki Jones, Bryn Department of Automatic Control and Systems Engineering University of Sheffield SheffieldS1 3JD United Kingdom Department of Electrical Engineering Princeton University PrincetonNJ08544 United States

The performance of control systems with packet loss as a result of an attack over the actuation communication channel is analysed. The operator is assumed to monitor the state of the channel by measuring the average number of packet losses and an attack detection criteria is established based on the statistic. The performance of the attacker is measured in terms of the increase of the linear quadratic cost function of the operator subject to a given detection constraint. Within that setting, the optimal denial of service (DoS) attack strategy is formulated for UDP-like and TCP-like communication protocols. For both communication protocols, DoS attack constructions that are independent and identically distributed (IID) are compared to those that are non-stationary. The main contributions of this paper are (i) explicit characterisation of the expected cost increase of the optimal attack constructions and the associated packet loss parameter for the IID case, (ii) proof, by example, that non-stationary random attacks outperform IID attacks in the presence of detection constraints. Copyright © 2019, The Authors. All rights reserved.

关键词： Networked control systems

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