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  • 201.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Identification of building damage using armax model: A parametric study2016Ingår i: Diagnostyka, ISSN 1641-6414, Vol. 17, nr 3, s. 3-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Structural Identification approach is used to identify and localize the existence of damage for a steel frame. The black box linear parametric model called Auto-Regressive Moving Average with eXternal input (ARMAX) was utilized for the construction of the Frequency Response Functions, based on simulation results. The Singular Value Decomposition method was adopted to identify how many significant eigenvalues exist and plot the Complex Mode Indicator Function for the complete frame. Three damage indices were adopted to evaluate the state of damage in the frame. The results indicated that the ARMAX is a robust scheme for structural damage detection.

  • 202.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Posicast Control of Structures Using MR Dampers2016Ingår i: Structural Control and Health Monitoring: The Bulletin of ACS, ISSN 1545-2255, E-ISSN 1545-2263, Vol. 23, nr 8, s. 1121-1134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a novel application of a semi active Posicast control scheme for structures with Magneto- Rheological (MR) dampers is presented. MR dampers are considered to be highly promising of semi-active control systems, which are becoming increasingly popular for alleviating the effects of dynamic loads on civil engineering structures because they combine the merits of both passive and active control systems. The main contribution of this article relates to the design, application, tuning and performance evaluation of the novel Posicast control scheme for structural control. The efficiency of the suggested control strategy was evaluated by performing numerical simulations of a benchmark three-story building with an MR damper, rigidly attached between the first floor and the ground. The damper’s behaviour was simulated using the Bouc-Wen model. Seven evaluation criteria were used to assess the performance of the proposed posicast control scheme in reducing the excited structure’s responses to dynamic loading. The simulation’s results indicated that the Posicast control scheme had significant advantages over conventional alternatives in terms of performance and efficiency.

  • 203.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. College of Engineering, Department of Civil Engineering, University of Mosul, Mosul, Iraq.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Dritsas, Leonidas
    University of Patras, Department of Electrical Engineering.
    Semi-active control of flexible structures using closed-loop input shaping techniques2017Ingår i: Structural Control and Health Monitoring: The Bulletin of ACS, ISSN 1545-2255, E-ISSN 1545-2263, Vol. 24, nr 5, artikel-id e1913Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this research effort, a novel approach on the control of structures with magnetorheological (MR) dampers is presented, based on an appropriately adapted closed-loop version of the generic input shaping control theory. The MR damper is a very promising kind of semi-active control system (actuator), mixing the advantages of the active and passive structural control systems, hence their increasing use as attenuators that reject the effects of dynamic loads on civil engineering structures. The main contribution of this article is the application and performance evaluation of the novel ‘Linear Matrix Inequality-based’ feedback version of the input shaping control theory for the first time in the area of structural control. The need for the use of a feedback version of input shaping control stems from the design trade-off between robustness and speed of response requirements. A simulation of a benchmark three-story building with one MR damper is employed to verify the efficiency of the proposed control approach. The nonlinear behaviour of the MR damper, rigidly connected between the first floor of the structure and the ground, is captured by the well-known Bouc–Wen model. The superiority and effectiveness of the proposed scheme in reducing the responses of the structure were proved using seven quantifiable evaluation criteria and by comparing these results with those achieved by classical and well-established alternative control schemes.

  • 204.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jonasson, Jan-Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Investigation of changes in modal characteristics before and after damage of a railway bridge: A case study2015Ingår i: The IES Journal Part A: Civil & Structural Engineering, ISSN 1937-3260, E-ISSN 1937-3279, Vol. 8, nr 2, s. 131-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The linear, time-invariant transfer function Txy has been utilized for the construction of FRF, based on the ambient vibration measurements. The results presented here indicated the possibility to identify and localize damages in steel railway bridges from the variations in the modal characteristics of the structure. The comparison between the modal characteristics for the healthy and collapsed bridge confirmed that damage had been existed. The abnormal percentage of change in modal damping, between the healthy and any other condition for a structure, can be regarded as a serious indicator for early stages of damage, while the high percentage of change in modal damping can clearly indicate the existence of damage in that structure. The average ratio of change in the damping ratio from the healthy to the collapsed bridge was about 206 % and this ration could be regarded as an index for the existence of a serious damage in steel bridges, which needs further evaluation in other test cases.

  • 205.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonasson, Jan-Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    A comparative study on the identification of building natural frequencies based on parametric models2014Ingår i: Proceedings of the 33rd IASTED International Conference on Modelling, Identification and Control: February 17 – 19, 2014, Innsbruck, Austria, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The analysis and design of civil engineering structures is a complex problem, which is based on many assumptions to simplify these operations. This in turn, leads to a difference in the structural behaviour between calculations based models and real structures. Structural identification was proposed by many researchers as a tool to reduce this difference between models and actual structures. Moreover, Parametric models and non-parametric models were used intensively for system identification by many researchers. In this research effort, the system identification concept is utilized to identify the natural frequencies for a steel building’s frames. Different black box linear parametric models such as Transfer Function model (TF), Auto-Regressive model with eXternal input model (ARX), Auto-Regressive Moving Average with eXternal input (ARMAX) model, Output Error model structure (OE), and Box-Jenkins model (BJ) were examined for identifying the first 10th natural frequencies for the building’s frames, based on simulation results. Abaqus 6.12 finite-element software was utilized to perform the time history analysis for the examples and the obtained responses at one point of the roofs (assumed as a sensor) were further processed by the parametric models to obtain the building’s natural frequencies based on the Abaqus time history analysis results (assumed as a measurements). After that, Abaqus 6.12 was utlized again to perform another analysis, which is called frequency analysis to obtain the building’s natural frequencies and mode shapes based on the stiffness and mass (not the measurements) of the buildings. The results showed that the linear parametric models TF, ARX, ARMAX, OE, and BJ are robust to identify the natural frequencies of building and they are recommend for future work.

  • 206.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonasson, Jan-Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Comfort Level Identification for Irregular Multi-storey Building Subjected to Vibrations2015Ingår i: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 50, s. 40-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, the System Identification approach is being used to identify the vertical frequencies of the top storey in a multi-storey building prefabricated from reinforced concrete in Stockholm. Before building construction, detailed investigation indicated that the building will not be affected by train vibrations from the nearby railway yard. After building completion, disturbing vibrations were observed in the building. Three measurement types namely: ambient vibration test, forced vibration test on the rails, and forced vibration test have been performed in order to specify the probable reasons for these vibrations. Five methods of structural identification approach, specifically: ARX, ARMAX, BJ, OEand State Space Models have been implemented for the identification process in this study usingthe tests' results. All the test types and model structures utilized have identified a concentration inthe floor only, which is close to the frequencies of human body parts. Furthermore, the article concludes that the ARMAX model and the Output Error model have indicated an excellent performance to predict the mathematical models of vibration's propagation in the building, when compared with other models used from the three types of tests. In addition, the results of the aforementioned system identification methods, implemented for this study, have indicated that there are no other reasons for the disturbing vibrations still observed in the building. Furthermore, the results confirmed the correctness of the previous theoretical and experimental results obtained by different specialists, who stated that the values of floor acceleration are within the acceptable limits, and the probable reason for any disturbance is the resonance between the generated low frequencies and the human body parts’ frequencies.

  • 207.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonasson, Jan-Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Semi-active structural control strategies2014Ingår i: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, s. 31-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The utilization of structural control systems to alleviate the responses of civil engineering structures, under the effects of dynamics loadings, has become a standard technology, while still there are numerous of current research approaches for advancing the effectiveness of these methodologies. It is important for successful application of smart structure to provide an effective control algorithm to compute the control forces to be applied on the building in order to reduce the external disturbances. The aim of this article is to provide a review of the control strategies to control the performance of semi-active systems utilized in civil engineering structures.

  • 208.
    Edrees, Tarek
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonasson, Jan-Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Hedlund, Hans
    Skanska Sverige AB Technology, Bridge and Civil Engineering.
    A state-of-the-art review of Structural Control Systems2015Ingår i: Journal of Vibration and Control, ISSN 1077-5463, E-ISSN 1741-2986, Vol. 21, nr 5, s. 919-937Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nowadays the utilization of structural control systems for alleviating the responses of civil engineering structures, under the effects of different kinds of dynamics loadings, has become a standard technology, while still there are numerous of current research approaches for advancing the effectiveness of these methodologies. The aim of this article is to review the state of the art technologies in structural control systems by introducing a general literature review for all the types of vibrations control systems that have been appeared till now. These systems can be classified into four main groups: a) passive, b) semi active, c) active, and d) hybrid based on their operational mechanism. A brief description of each of these main groups and their subgroups, with their corresponding advantages and disadvantages will be also extendedly reported in this review. This article will conclude by providing an overview of some innovative practical implementations of devices, which are able to demonstrate their potentials and future directions of structural control systems in civil engineering.

  • 209.
    Elbadawi, Mohammed
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Rheological and Mechanical Investigation into the Effect of Different Molecular Weight Poly(ethylene glycol)s on Polycaprolactone-Ciprofloxacin Filaments2019Ingår i: ACS Omega, E-ISSN 2470-1343, Vol. 4, nr 3, s. 5412-5423Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fused deposition fabrication (FDF) three-dimensional printing is a potentially transformative technology for fabricating pharmaceuticals. The state-of-the-art technology is still in its infancy and requires a concerted effort to realize its potential. One aspect includes the processing parameters of FDF and the effect of formulation thereto, which, to date, have not been thoroughly investigated. To progress understanding, the effect of different molecular weight poly(ethylene glycol)s (PEG) on polycaprolactone (PCL) loaded with ciprofloxacin (CIP) was investigated. A rheometer was used, and adapted accordingly, to analyze three processing aspects pertaining to FDF: viscosity, solidification, and adhesion. The results revealed that both CIP and PEG affected all three processing parameters. The salient findings were that the ternary blend with 10% w/w PEG 8000 exhibited rheological and adhesive properties ideal for FDF, as it provided a desirably shear-thinning filament that solidified rapidly, and improved the adhesion strength, in comparison to both the PCL-CIP binary blend and other ternary blends. In contrast, the ternary blend with 15% w/w PEG 200 was unfavorable; despite having a greater plasticizing effect, whereby the viscosity was markedly reduced, the sample provided no benefit to the solidification behavior of PCL-CIP and, in addition, failed to display adhesive behavior, which is a necessity for a successful print in FDF. The original findings herein set the precedent that the effect of drug and PEG on FDF processing should be considered beyond solely modifying the viscosity.

  • 210.
    Elbadawi, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap. Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andrikopoulos, Georgios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Bio-Inspired Climbing Robots in Wet Environments: Recent Trends in Adhesion Methods and Materials2018Konferensbidrag (Refereegranskat)
  • 211.
    Eleftheroglou, Nick
    et al.
    Faculty of Aerospace Engineering, TU Delft, the Netherlands.
    Mansouri, Sina Sharif
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Loutas, Theodoros
    Department of Mechanical Engineering & Aeronautics, University of Patras, Greece.
    Karvelis, Petros
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Georgoulas, George
    Department of Mechanical Engineering & Aeronautics, University of Patras, Greece.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Zarouchas, Dimitrios
    Faculty of Aerospace Engineering, TU Delft, the Netherlands.
    Intelligent data-driven prognostic methodologies for the real-time remaining useful life until the end-of-discharge estimation of the Lithium-Polymer batteries of unmanned aerial vehicles with uncertainty quantification2019Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 254, artikel-id 113677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the discharge voltage is utilized as a critical indicator towards the probabilistic estimation of the Remaining Useful Life until the End-of-Discharge of the Lithium-Polymer batteries of unmanned aerial vehicles. Several discharge voltage histories obtained during actual flights constitute the in-house developed training dataset. Three data-driven prognostic methodologies are presented based on state-of-the-art as well as innovative mathematical models i.e. Gradient Boosted Trees, Bayesian Neural Networks and Non-Homogeneous Hidden Semi Markov Models. The training and testing process of all models is described in detail. Remaining Useful Life prognostics in unseen data are obtained from all three methodologies. Beyond the mean estimates, the uncertainty associated with the point predictions is quantified and upper/lower confidence bounds are also provided. The Remaining Useful Life prognostics during six random flights starting from fully charged batteries are presented, discussed and the pros and cons of each methodology are highlighted. Several special metrics are utilized to assess the performance of the prognostic algorithms and conclusions are drawn regarding their prognostic capabilities and potential.

  • 212.
    Eliasson, Jens
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Towards road surface monitoring: experiments and technical challenges2009Ingår i: 2009 IEEE control applications (CCA) & intelligent control (ISIC): St. Petersburg, Russia, 8 - 10 July 2009 ; [18th IEEE International Conference on Control Applications (CCA) and 24th IEEE International Symposium on Intelligent Control (ISIC) ; part of the 3rd IEEE Multi-Conference on Systems and Control (MSC 2009)], Piscataway, NJ: IEEE Communications Society, 2009, s. 655-659Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper discusses results from real-life tests with intelligent road marking units (RMU), placed on the surface of a highway in northern Sweden, to monitor passing vehicles and road properties, as well as making the information available through a wireless sensor network. Wireless sensor networks are starting to gain interest in the area of cooperative safety and efficiency in transport as they can contribute to the reduction of accidents and emissions as well as enhanced driver experiences. Intelligent road markings are another key element for the creation of intelligent transport systems, complementing road side units, devices placed near a road equipped with high-performance computational platforms and long range communication capabilities. This paper shows that RMUs are feasible from the perspectives of low-power consumption, durability, and sensing performance.

  • 213.
    Englund, Gunnar
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Att balansera en inverterad pendel1989Rapport (Övrigt vetenskapligt)
  • 214.
    Eriksson, Martin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Monitoring, Modelling and Identification of Data Center Servers2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Energy efficient control of server rooms in modern data centers can help reducing the energy usage of this fast growing industry. Efficient control, however, cannot be achieved without: i) continuously monitoring in real-time the behaviour of the basic thermal nodes within these infras- tructures, i.e., the servers; ii) analyzing the acquired data to model the thermal dynamics within the data center. Accurate data and accurate models are indeed instrumental for implementing efficient data centers cooling strategies. In this thesis we focus on Open Compute Servers, a class of servers designed in an open-source fashion and used by big players like Facebook. We thus propose a set of appropriate methods for collecting real-time data from these platforms and a dedicated thermal model describing the thermal dynamics of the CPUs and RAMs of these servers as a function of both controllable and non-controllable inputs (e.g., the CPU utilization levels and the air mass flow of the server’s fans). We also identify this model from real data and provide the results so to be reusable by other researchers.

  • 215. Eriksson, Martin
    et al.
    Lucchese, Riccardo
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Jonas
    RISE - Swedish Institute of Computer Science.
    Ljung, Anna-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mousavi, Arash
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Varagnolo, Damiano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Monitoring and Modelling Open Compute Servers2017Ingår i: Proceedings IECON 2017: 43rd Annual Conference of the IEEE Industrial Electronics Society, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 7177-7184Konferensbidrag (Refereegranskat)
    Abstract [en]

    Energy efficient control of server rooms in modern data centers can help reducing the energy usage of this fast growing industry. Efficient control, however, cannot be achieved without: i) continuously monitoring in real-time the behavior of the basic thermal nodes within these infrastructures, i.e., the servers; ii) analyzing the acquired data to model the thermal dynamics within the data center. Accurate data and accurate models are indeed instrumental for implementing efficient data centers cooling strategies. In this paper we focus on a class of Open Compute Servers, designed in an open-source fashion and currently deployed by Facebook. We thus propose a set of methods for collecting real-time data from these platforms and a control-oriented model describing the thermal dynamics of the CPUs and RAMs of these servers as a function of both manipulable and exogenous inputs (e.g., the CPU utilization levels and the air mass flow produced by the server's fans). We identify the parameters of this model from real data and make the results available to other researchers.

  • 216.
    Evestedt, Magnus
    et al.
    Division of Systems and Control, Department of Information Technologies, Uppsala University.
    Medvedev, Alexander
    Thorén, Mathias
    SSAB Oxelösund AB.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Slopping warning in the LD converter process: an extended evaluation study2007Ingår i: Proceedings of the 12th IFAC Symposium on Automation in Mining, Mineral and Metal Processing: Quebec, Canada, 21 - 23 August 2007, Red Hook: Curran Associates, Inc., 2007, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    The most common steel-making process in the world is the Lintz-Donawitz converter. During operation, a slag foam is created to improve the converter performance. Problems arise when the foam level exceeds the height of the vessel and overflows, causing metal loss, process disruption and environmental pollution. A warning system, based on advanced signal processing and key process parameter measurements is evaluated on data from 100 charges at SSAB Oxelösund. Slopping was timely detected in 80% of the blows.

  • 217.
    Fairley, Jacqueline A.
    et al.
    aDepartments of Neurology and Neurosurgery, Emory University School of Medicine, Atlanta, GA .
    Georgoulas, Georgios
    bDepartment of Informatics Engineering, Technological Educational Institution of Epirus.
    Smart, Otis L.
    Departments of Neurology and Neurosurgery, Emory University School of Medicine, Atlanta, GA .
    Dimakopoulos, George
    Department of Statistics and Actuarial Financial Mathematics, University of the Aegean, Karlovassi, Samos.
    Karvelis, Petros
    Department of Informatics Engineering, Technological Educational Institution of Epirus.
    Stylios, Chrysostomos D.
    Department of Informatics Engineering, Technological Educational Institution of Epirus.
    Rye, David B.
    Departments of Neurology and Neurosurgery, Emory University School of Medicine, Atlanta, GA .
    Bliwise, Donald L.
    Departments of Neurology and Neurosurgery, Emory University School of Medicine, Atlanta, GA .
    Wavelet analysis for detection of phasic electromyographic activity in sleep: of mother wavelet and dimensionality reduction2014Ingår i: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 48, nr 1, s. 77-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phasic electromyographic (EMG) activity during sleep is characterized by brief muscle twitches (duration 100-500. ms, amplitude four times background activity). High rates of such activity may have clinical relevance. This paper presents wavelet (WT) analyses to detect phasic EMG, examining both Symlet and Daubechies approaches. Feature extraction included 1. s epoch processing with 24 WT-based features and dimensionality reduction involved comparing two techniques: principal component analysis and a feature/variable selection algorithm. Classification was conducted using a linear classifier. Valid automated detection was obtained in comparison to expert human judgment with high (>90%) classification performance for 11/12 datasets

  • 218.
    Fakharian, Ahmad
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Design of switching multiobjective controller: A new approach2011Ingår i: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, Vol. 2011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Design of switching H 2 / H ∞ output-feedback controller for discrete-time LTI systems with state-multiplicative noise is considered. The closed loop system achieves a minimum bound on the stochastic H 2 performance level, while satisfying the H ∞ performance. The proposed controller is based on a fuzzy supervisor which manages the combination of two separate H 2 and H ∞ controllers. A convex formulation of the two controllers leads to a structure which benefits from the advantages of both controllers to ensure a good performance in both the transient phase (H 2 controller) and the steady phase (H ∞ controller). The stability analysis uses the Lyapunov technique, inspired from switching system theory, to prove that the closed loop system with the proposed controller structure remains globally stable despite the configuration changing

  • 219. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    An iterative-LMI based H2 control of singular perturbation systems2011Ingår i: 2011 IEEE International Conference on Control Applications (CCA): 28 - 30 Sept. 2011, Denver, Colorado, USA ; part of 2011 5th IEEE Multi-Conference on Systems and Control (MSC) / [ed] Jagannathan Sarangapani, Piscataway, NJ: IEEE Communications Society, 2011, s. 1505-1509Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper an iterative LMI based approach for solving the H2 control problem using static state feedback for singular perturbation systems is proposed. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new iterative algorithm, these inequalities are solved through iterative LMI formulation. To show the effectiveness of the proposed algorithm comparing to other standard time-scale decomposition methods, an illustrative example is also provided

  • 220. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    H2 static state feedback control or linear singular perturbation systems: a new approach2011Ingår i: 2011 Canadian Conference on Electrical and Computer Engineering, CCECE 2011: May 8-11 2011, Niagara Falls, Ontario, Canada, Piscataway, NJ: IEEE Communications Society, 2011, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper a new approach for solving the H2 control problem using static state-feedback for LTI singular perturbation systems is proposed which achieves a minimum bound on the H2 performance level of closed-loop system. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new algorithm, these inequalities are solved through LMI formulation. To show the effectiveness of the proposed algorithm comparing to other standard time-scale decomposition methods, an illustrative example is also provided.

  • 221.
    Fakharian, Ahmad
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Khanian, M. Yousefi Azar
    Islamic Azad University.
    A new approach on H-infinity control of linear singular pertubation systems2011Ingår i: 2011 9th IEEE International Conference on Control and Automation (ICCA 2011): Santiago, Chile, 19 - 21 December 2011, Piscataway, NJ: IEEE Communications Society, 2011, s. 969-973Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper a new approach for solving the H∞ control problem using static state-feedback for LTI singular perturbation systems is proposed. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new algorithm, these inequalities are solved through LMI formulation. To show the effectiveness of the proposed algorithm comparing to other methods, an illustrative example is also provided.

  • 222. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mehrfam, Mohsen
    Department of Electrical and Computer Engineering, Islamic Azad University.
    Adaptive Kalman filtering based navigation: an IMU/GPS integration approach2011Ingår i: Proceedings of the 8th IEEE International Conference on Networking, Sensing and Control: Delft, The Netherlands, 11-13 April, 2011, Piscataway, NJ: IEEE Communications Society, 2011, s. 181-185Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates on the development and implementation of a high integrity navigation system based on the combined use of the Global Positioning System (GPS) and an inertial measurement unit (IMU) for land vehicle applications. The complementary properties of the GPS and the INS have motivated several works dealing with their fusion by using a Kalman Filter. The conventional kalman filter has a fix error covariance matrix in all times of processing. Multi-sensor based navigation system that is implemented in this paper is called data synchronization. Also, multi-rate operations that are compared with conventional Kalman filtering has fix error covariance matrix. Therefore, when GPS outage occurred we have improper treat by kalman filter. In this paper we present an Adaptive method instead of conventional methods. It is shown that proposed method has a better performance rather than conventional method. Experimental results show the effectiveness of the GPS/INS integrated system.

  • 223.
    Fakharian, Ahmad
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Hosseini, Saman
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Hybrid object detection using improved Gaussian mixture model2011Ingår i: 11 International Conference on Control, Automation and Systems (ICCAS2011): 26-29 October 2011, Kintex, Korea, Piscataway, NJ: IEEE Communications Society, 2011, s. 1475-1479Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose a novel approach to detect moving objects in a complex background. The Gaussian mixture model (GMM) is an effective way to extract moving objects from a video sequence. However, the conventional mixture Gaussian method suffers from false motion detection in complex backgrounds and slow convergence. This work, in order to achieve robust and accurate extraction of the shapes of moving objects, applies a hybrid method to remove noise from images. The proposed model consists of two stages. The first stage consists of a fourth order PDE and the second stage is a relaxed median Experimental results show that the proposed model performs well even in the presence of higher levels of noise.

  • 224. Fakharian, Ahmad
    et al.
    Hosseini, Saman
    Islamic Azad University.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Precise hybrid motion detection and tracking in dynamic background2011Ingår i: The 19th Mediterranean Conference on Control and Automation (MED2011): June 20-23, 2011, Corfu, Greece, Piscataway, NJ: IEEE Communications Society, 2011, s. 1398-1402Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a novel and robust algorithm, for multiple motion detection and tracking in dynamic and complex scenes. The algorithm consists of two steps: at first, we use a robust algorithm for human detection. Then, Gaussian mixture model (GMM), Neighborhood-based difference and Overlapping-based classification are applied to improve human detection performance .The conventional mixture Gaussian method suffers from false motion detection in complex backgrounds and slow convergence. We combine three above mentioned methods to obtain detection. The second step of the proposed algorithm is object tracking framework based on Kalman filtering which works well in dynamic scenes. Experimental results show the high performance of the proposed method for multiple object tracking in complex and noisy backgrounds.

  • 225.
    Fanti, Maria Pia
    et al.
    Polytechnic of Bari.
    Iacobellis, Giorgio
    Polytechnic of Bari.
    Ukovich, Walter
    University of Trieste.
    Boschian, Valentina
    University of Trieste.
    Georgoulas, Georgios
    Technological Educational Institute of Epirus, Arta.
    Stylios, Chrysostomos D.
    Technological Educational Institute of Epirus, Arta.
    A simulation based Decision Support System for logistics management2015Ingår i: Journal of Computational Science, ISSN 1877-7503, E-ISSN 1877-7511, Vol. 10, s. 86-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper deals with designing and developing a Decision Support System (DSS) that will be able to manage the flow of goods and the business transactions between a port and a dry port. An integrated DSS architecture is proposed and specified and the main components are designed on the basis of simulation and optimization modules. In order to show the use and implementation of the DSS, this work tests and analyzes the case of the area of the Trieste port and manages the export flows of freights between a dry port and a seaport. An integrated approach is designed mainly at tactical and operational decision level exploiting simulation and optimization approaches and especially metaheuristic approaches

  • 226.
    Fischer, Britta
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    System identification in alternative shift operators with applications and some other topics1999Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis mainly concentrates on two issues of system identification, namely identification for controller design and identification with orthonormal basis functions. In identification for controller design one seeks to obtain sufficient knowledge about the plant to design a high-performance controller. The frequency domain method proposed in this thesis is applicable to plants that are typical to process industry. While designing a high-performance controller it is desirable to keep the amount of identification experiments small. This has been achieved by choosing the next experimental conditions in an adaptive manner, i.e. the current experimental conditions depend on past data. The remaining parts of the thesis are concerned with identification by means of orthonormal basis functions, especially the Laguerre and Kautz functions. These particular functions have been chosen due to their simple mathematical structure and due to the fact that their dynamics are similar to the nature of a wide range of industrial processes. Linear, time-invariant, multi-input multi-output systems are considered. In system identification one usually uses the entire measurement data in order to find an appropriate plant model. In this thesis, the data is projected onto the Laguerre and Kautz functions, respectively, and only the projection coefficients, also called expansion coefficients or Laguerre/Kautz coefficients, are used for identification. As the considered orthonormal basis functions provide the user with some additional degrees of freedom in the time constants of the functions, noise and unmodelled dynamics can be attenuated through a judicious choice of these time constants. Furthermore, the projection leads to a considerable data reduction. After the projection of the measurement data, classical identification methods as subspace identification or the least squares method can be used to identify a model which, after a certain mapping, can for example be used for controller design. The suggested method has been derived for the identification of continuous and discrete models and has been successfully employed for the estimation of a coal injection process, a vibration process, subprocesses of a sugar mill, a paper machine headbox and time delay estimation. For the case of time delay estimation, error bounds on the estimation error have been derived. Results from applications show that the presented method in many cases outperforms classical linear methods and provides good linear approximations of non-linear processes. Furthermore, the excitation characteristics and numerical properties of the expansion coefficients have been studied and compared to the properties of the measurement data sets.

  • 227.
    Fischer, Britta
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Two topics in system identification1997Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 228. Fischer, Britta
    et al.
    Gotthold, Daniel
    Mäkilä, Pertti
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Control relevant identification in hinf: adaptive information and experiment design1996Ingår i: Proceedings of the 13th World Congress: International Federation of Automatic Control : San Francisco, USA, 30th June - 5th July 1996 ; (in 18 volumes) / [ed] Janos J. Gertler, Oxford: Pergamon Press, 1996, Vol. 1, s. 115-120Konferensbidrag (Refereegranskat)
  • 229. Fischer, Britta
    et al.
    Gotthold, Daniel
    Mäkilä, Pertti
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Control relevant identification in hinf: adaptive information and experiment design1996Ingår i: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 29, nr 1, s. 4046-4051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Joint issues of modelling and control design are studied in a frequency domain setup. Stable systems with monotone Bode plots are chosen as the basis of the study presented in this work. Such dynamics is typical for plants in industrial process control. Adaptive information is considered and both open-loop and closed-loop experimental conditions are included. For systems with monotone Bode plots the information typically required for successful control design consists of a small part of the frequency response only. This can be exploited in experiment design.

  • 230. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    L2 time delay estimation by means of Laguerre functions1999Ingår i: Proceedings of the 1999 American Control Conference :: June 2 - 4, 1999, Hyatt Regency San Diego, San Diego, California, USA, Piscataway, NJ: IEEE Communications Society, 1999, s. 455-459Konferensbidrag (Refereegranskat)
    Abstract [en]

    A straightforward method for the estimation of continuous time delays in narrowband signals is proposed. Delay estimation is especially of interest for those areas in signal processing that deal with the time delay of arrival (TDOA). The new method involves a parameterization of the identification problem in the Laguerre functions. This formalism is chosen due to the nature of the signals. Then the delay is obtained from a finite number of input/output Laguerre coefficients by using l2 norm optimal estimation. Estimation bounds are given and experiments from ultrasonic applications are presented

  • 231. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Laguerre domain estimation of time delays in narrowband ultrasonic echoes1999Ingår i: Proceedings of the 14th World Congress: International Federation of Automatic Control : Beijing, P.R. China, 5 - 9 July 1999 / [ed] Han-Fu Chen, Kildington: Publ. for the International Federation of Automatic Control by Pergamon, , 1999, s. 361-366Konferensbidrag (Refereegranskat)
    Abstract [en]

    The time delay of arrival (TDOA) is required in many areas in signal processing. In this paper we propose a novel and straightforward method to estimate small continuous time delays in narrowband signals out of a sampled sequence of the input and output signals. It is based on the parameterization of the identification problem in the Laguerre functions. An lp norm optimal estimator is then applied to estimate the delay. Furthermore, estimation bounds are studied and experiments from ultrasonic applications are presented to highlight the performance of the method

  • 232. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Laguerre domain estimation of time delays in narrowband ultrasonic echoes1999Ingår i: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 32, nr 2, s. 4129-4134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The time delay of arrival (TDOA) is required in many areas in signal processing. In this paper we propose a novel and straightforward method to estimate small continuous time delays in narrowband signals out of a sampled sequence of the input and output signals. It is based on the parameterization of the identification problem in the Laguerre functions. An lp norm optimal estimator is then applied to estimate the delay. Furthermore, estimation bounds are studied and experiments from ultrasonic applications are presented to highlight the performance of the method

  • 233. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Laguerre shift identification of a pressurized process1998Ingår i: Proceedings of the 1998 American Control Conference, ACC, June 24 - 26, 1998, Philadelphia, Pennsylvania, USA, Piscataway, NJ: IEEE Communications Society, 1998, s. 1933-1937Konferensbidrag (Refereegranskat)
  • 234.
    Fjällström, Eva
    et al.
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Pedagogik språk och Ämnesdidaktik.
    Knorn, Steffi
    Uppsala University.
    Staffas, Kjell
    Uppsala University.
    Varagnolo, Damiano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Developing Concept Inventory Tests for Electrical Engineering: Extractable Information, Early Results, and Learned Lessons2018Ingår i: 2018 UKACC 12th International Conference on Control (CONTROL), 2018, s. 436-441, artikel-id 8516766Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper suggests a method for developing, implementing and assessing a concept inventory test for electrical engineering students (CITE). The aim of this test is to help students better understand and learn core concepts, plus increase their awareness about links between the different courses and other themes of the program. Our and other experiences show that students often struggle to understand and use fundamental concepts, and how these relate to the various courses. This issue is probably due to the fact that traditional exams mainly focus on assessing procedural tasks (e.g., directly solving specific problems following step-by-step approaches). The investigated programs at Uppsala University (UU) and Luleå Uni-versity of Technology (LTU), nonetheless, have no tool for collecting quantitative data on how students develop conceptual knowledge throughout the programs, and thus no means to obtain an holistic view about their learning process. The here proposed methodology thus describes how to develop tests that would not only provide students with valuable feedback on their progression, but also equip teachers and program boards with high-end data for pedagogical and course development purposes. Besides illustrating the developmental methodology, the paper includes reactions and remarks from students on what the tests would provide and what would motivate them to take it.

  • 235.
    Fredriksson, Håkan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Andersson, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Track loader kinematics2010Ingår i: Preprints: The Second IFAC Symposium on Telematics Applications, TA 2010, Timi¸soara, Romania, 5 - 8 October 2010 / [ed] Ioan Dumitrache, Timisoara: Ed. Politehnica , 2010, s. 139-142Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the problem to teleoperate a Caterpillar 973c track loader. The track loader and a system for teleoperation are described. A tested and working kinematic model used for dead reckoning is also presented. Track speed sensors combined with a rate gyro are used as input to the model. The model shows good results when tested and compared to a GPS navigation system.

  • 236.
    Fredriksson, Håkan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Andersson, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gyro feedback of a hydraulic steering system2011Ingår i: International Journal of Vehicle Autonomous Systems, ISSN 1471-0226, E-ISSN 1741-5306, Vol. 9, nr 3/4, s. 189-202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the problem to steer, teleoperated as well as autonomously, a tractor that is to operate on a rough and slippery surface. The main idea is to control the effective steering angle of the vehicle. A benefit with this approach is that the vehicle will strive to move in a predefined way irrespective of the surface conditions. To test if the approach is usable we implemented a straight forward p-controller in combination with an estimator of the effective steering angle of the tractor. Our tests indicates that the approach can be useful. Future work would include studies on more advanced control strategies and estimators to reduce some of the problems that we address.

  • 237.
    Fresk, Emil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    The Core of Aerial Robotic Workers: Generalized Modeling, Estimation, and Control2018Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis we are going to explore what the operational core, both mathematically and algorithmically, of an Aerial Robotic Worker consists of, in order to estimate its egomotion and parameters, and adaptively control the aerial vehicle. Moreover, the aim of this thesis is to be a condensed reference for the corresponding areas of aerial robotics, in order to provide a stable and complete foundation on which one can continue research on. The areas that are covered in this Thesis are: 1) the fundamental modeling of the generalized aerial vehicle, where the kinematics, sensors and motor/thrust models will be presented together with simplified models for the motor characteristics, which will form the basis for all the future derivations, 2) how to model, calibrate and compensate for the errors existing in, and induced into, cheap accelerometers and gyroscopes, as these sensors constitute the aerial platform's core sensor suite as the inertial sensor. Successful methodologies and results are presented and evaluated to show that the cost of calibration can be dramatically reduced without loss of accuracy nor mechanical complexity. 3) How to perform inertial sensor driven egomotion and parameter estimation to lay the foundation for adaptive control strategies, where specific weight will be put on the successful development of a new profound sensory system which has the possibility to replace GPS in robotics applications, while also being able to perform indoors and in GPS denied environments, and which was the core of the localization module done in the AEROWORKS project, enabling the full, high accuracy localization around tall, GPS interfering infrastructure. And finally 4) how to utilize the estimation in low and high-level adaptive controllers, where specific results on how to successfully compensate for the movement of the center of gravity, together with the reduction of thrust over time due to declining battery voltage. Moreover we will explore the use case of Aerial Robotic Workers in real life applications and we will identify and comment on potential future directions of these aerial robotic systems and the impact theses can have in both research and society.

  • 238.
    Fresk, Emil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Towards Aerial Robotic Workers2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this thesis is to advance the control and estimation schemes for multirotors, and more specifically the Aerial Robotic Worker, in order to progress towards the necessary control and estimation performance for robust control, cooperation and collaboration. Towards this envisioned aim, this Licentiate thesis will present the following main research contributions: a) a singularity-free attitude controller for the attitude problem has been established, that does not have the inherent drawbacks of Euler angle or Direction Cosine Matrix based approaches, b) a generalized estimation scheme for attitude, position and parameter estimation will be presented that has the merit of low computational footprint, while it is robust towards magnetic disturbances and able to identify key parameters in the model of an Aerial Robotic Worker, c) an method for estimating the induced vibration frequencies on the multirotor’s frame, and the respective amplitudes, that relies on notch filtering for attenuating the induced vibrations, and d) a theoretical establishment, as well as an experimental development and evaluation of a variable pitch propeller model to add additional degrees of freedom and increase the robustness of an Aerial Robotic Worker. In the first part of this thesis the main contributions of the previous research approaches will be highlighted, while in the second part of the thesis the corresponding and in full detail articles will be presented.

  • 239.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mansouri, Sina Sharif
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Kanellakis, Christoforos
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Halén, Erik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Reduced complexity calibration of MEMS IMUs2017Ingår i: 2017 25th Mediterranean Conference on Control and Automation, MED 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 1316-1320, artikel-id 7984300Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a reduced complexity calibration method for Micro-Electro-Mechanical Systems (MEMS) Inertial Measurement Units (IMUs) will be presented, which does not need the rotating reference tables, commonly used in the gyroscope calibration. As it will be presented, in the proposed novel scheme fixed angle rotations have been utilized to observe the integral of the gyroscope signals to find the corresponding sensitivity, axis misalignment and acceleration sensitivity matrices. This appraoch has the significant merit of high norm accuracy, easiness of use, low cost and simplicity in construction, thus allowing anyone with a basic electronics knowledge to calibrate an IMU.

  • 240.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A generalized Frame Adaptive MPC for the low-level control of UAVs2018Ingår i: 2018 European Control Conference (ECC), Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 1815-1820Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to establish an adaptiveModel Predictive Control (MPC) scheme for the angular rate and thrust control of a multirotor Unmanned Aerial Vehicle (UAV). The proposed model adaptiveness comes from estimating the movement of the Center of Gravity (CoG) combined withthe thrust constant of the motors, making the system robust to disturbances and fast to adapt to changing parameters, while also taking under consideration the control signal bounds in order to guarantee for no motor stalls, while flying. The linear requirements of the MPC are adhered to by transforming the estimation and control problem into a control signal squared domain, making the system linear. The efficacy of the proposed estimation and control scheme is presented in simulations where worst case scenarios have been considered.

  • 241.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Experimental Evaluation of a Full Quaternion Based Attitude Quadrotor Controller2015Ingår i: Proceedings of 2015 IEEE 20th International Conference on Emerging Technologies & Factory Automation (ETFA 2015): )Luxembourg, 8-11 Sept. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7301555Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to present a novel quater- nion based control scheme for the attitude control problem of a quadrotor and experimentally evaluate its performance. A quaternion is a hyper complex number of rank 4 that can be utilized to avoid the inherent geometrical singularity when representing rigid body dynamics with Euler angles or the complexity of having coupled differential equations with the Direction Cosine Matrix (DCM). In the presented approach the novel contributions consist of: a) the quadrotor’s attitude model and b) the proposed non–linear Proportional squared (P^2) control algorithm, which have been proposed and experimentally evaluated fully in the quaternion space, without any transformations nor calculations in the Euler angle nor the DCM spaces. The established control scheme is combined with a quaternion based Madwick Complementary filter for estimating the attitude quadrotor’s responses. Multiple experi- mental results, including the case where external disturbances are acting on the quadrotor, are being presented for proving the efficiency and the robustness of the proposed novel quaternion based controller.

  • 242.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Experimental Model Derivation and Control of a Variable Pitch Propeller Quadrotor2014Ingår i: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 723-729Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to present a novel quaternion based control scheme for the attitude control problem of a quadrotor equipped with variable pitch propellers. A variable pitch propeller is a type of propeller system utilizes a mechanical mechanism to change the pitch of the rotor blades, while when applied to quadrotors it results in an over-actuated control system. The novelty of the article stems from: a) the proposal of an experimental model for variable pitch propellers and b) the novel proposed thrust and power consumption optimisations for the over-actuated quadrotor. Throughout the article, the merits of the proposed novel approach are being analyzed and discussed, while the efficiency of the variable pitch propellers are being evaluated by extended simulation and experimental results.

  • 243.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Frame Induced Vibration Estimation and Attenuation Scheme on a Multirotor helicopter2015Ingår i: Decision and Control (CDC): Los Angeles, CA, 15-17 Dec. 2014, Piscataway, NJ: IEEE Communications Society, 2015, s. 5698-5703, artikel-id 7040281Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to establish an induced frame vibration and attenuation scheme, specifically targeting the area of multi-rotor Unmanned Aerial Vehicles (UAVs), such as quadrotors. These types of unmanned small scale helicopters are characterised by small and light frames, which are vulnerable to vibrations induced by the operation of the motors or external environmental factors. The existence of such vibrations effecting the frame can significantly deteriorate the performance of the overall closed system and even drive it to instabilities. In this article spectral estimation schemes based on: a) Autoregressive (AR) modelling and b) Multiple Signal Classification (MUSIC) are being established and evaluated towards their ability to detect the induced vibration frequencies on the UAV, while an extended discussion is being presented on selecting the correct number of the identified induced vibrating frequencies. In a sequential stage, a vibration attenuation approach based on notch filtering is being presented, being able to correctly attenuate the induced vibrating frequencies in the measurements. The efficiency of the overall suggested scheme is being evaluated by experimental results that indicate the significant improvement in the measurements achieved bythe direct application of the proposed scheme.

  • 244.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Full quaternion based attitude control for a quadrotor2013Ingår i: European Control Conference (ECC), July 17-19, 2013, Zurich, Switzerland, 2013, s. 3864-3869, artikel-id 6669617Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to present a novel quaternion based control scheme for the attitude control problem of a quadrotor. A quaternion is a hyper complex number of rank 4 that can be utilized to avoid the inherent geometrical singularity when representing rigid body dynamics with Euler angles or the complexity of having coupled differential equations with the Direction Cosine Matrix (DCM). In the presented approach both the quadrotor's attitude model and the proposed non-linear Proportional squared (P^2) control algorithm have been implemented in the quaternion space, without any transformations and calculations in the Euler's angle space or DCM. Throughout the article, the merits of the proposed novel approach are being analyzed and discussed, while the efficacy of the suggested novel quaternion based controller are being evaluated by extended simulation results.

  • 245.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A Generalized Reduced-Complexity Inertial Navigation System for Unmanned Aerial Vehicles2017Ingår i: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 25, nr 1, s. 192-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a generic approach to attitude and position estimation, suited for any type of unmanned aerial vehicle, is presented. This will be achieved by establishing a generic framework, which can be extended using adaptive methods to determine the thrust properties of the engines and the mass of the aircraft, while keeping the overall computational complexity of the system low. Furthermore, the effect of magnetic disturbances will be reduced in a novel way by confining the magnetic errors to affect only heading, without compromising the pitch and roll estimation of the system with error-based estimation. The efficacy of the proposed framework will be evaluated through extended simulations and experimental validations on a multirotor. Finally, guidelines will be provided toward: 1) an implementation with a reduced computational complexity and 2) the utilization of the square-root formulations of the extended Kalman filter for extending the dynamic range of the filter.  

  • 246.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Wuthier, David
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Generalized center of gravity compensation for multirotors with application to aerial manipulation2017Ingår i: IEEE International Conference on Intelligent Robots and Systems, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 4424-4429, artikel-id 8206307Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this paper is to establish a generalized parameter estimation scheme to online estimate the Center of Gravity (COG) for multirotors, while using a geometric controller to perform position tracking for applications in aerial manipulation. The proposed scheme is developed so the controller uses the estimated COG to compensate and remove constant offset in the position tracking. The efficiency and validity of the proposed parameter estimation and compensation scheme is proved through two experimental evaluations, one when step changes to the COG are applied and one tracking experiment where a compact aerial manipulator is attached to the multirotor and performs sweeping motions.

  • 247.
    Fresk, Emil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ödmark, Kristoffer
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ultra WideBand enabled Inertial Odometry for Generic Localization2017Ingår i: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, nr 1, s. 11465-11472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we will present a inertial odometry localization system, utilizing Ultra WideBand distance measurements for corrections, as a generic localization solution. The proposed scheme is evaluated in two different measurement schemes, one cyclic and one based on stochastic events, which has the strong merit of minimizing the sampling rate, while adhering to covariance constraints on the state, allowing the system to conform with RF regulations. The efficacy of the proposed scheme is evaluated in extended experimental evaluation on an hexacopter Unmanned Aerial Vehicle

  • 248.
    Garmabaki, Amir
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lindström, John
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Software Fault Detection in Control Systems2017Ingår i: Risk, Reliability and Safety: Innovating Theory and Practice - Proceedings of the 26th European Safety and Reliability Conference, ESREL 2016 / [ed] Walls L.,Revie M.,Bedford T, CRC Press, 2017, s. 2006-2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fault detection in the software of control systems is a difficult task. In largely interconnected systems, not only the individual performance of one channel, but also its interaction with other components, must be considered. In this conceptual paper, we outline a new maintenance concept for the detection of software faults in control systems. The concept includes two approaches, morning gymnastics test and envelope analysis. The morning gymnastics test generates data for a baseline of the current operational abilities in contrast to the specified abilities and should be applied when feasible in continuous production systems. The test integrates historical and new sets of data to track degradation trends. Envelope analysis can be performed to detect operational anomalies and is based on subsequent deep analysis to distinguish software and hardware faults from each other. By using the envelope analysis it is possible to identify failures and disturbances affecting the control system. Thus, the proposed maintenance concept may facilitate detection and identification of potential failures in critical automated system.

  • 249.
    Gavrilis, Dimitris
    et al.
    Department of Electrical Engineering and Computer Technology, University of Patras.
    Georgoulas, Georgios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Vasiloglou, Nikolaos
    Ismion Inc.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    An Intelligent Assistant for Physicians2016Ingår i: IEEE 38th Annual International Conference of the Engineering in Medicine and Biology Society (EMBC): Orlando, FL, USA, 16-20 Aug. 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 2586-2589, artikel-id 7591259Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a software tool developed for assisting physicians during an examination process. The tool consists of a number of modules with the aim to make the examination process not only quicker but also fault proof moving from a simple electronic medical records management system towards an intelligent assistant for the physician. The intelligent component exploits users inputs as well as well established standards to line up possible suggestions for filling in the examination report. As the physician continues using it, the tool keeps extracting new knowledge. The architecture of the tool is presented in brief while the intelligent component which builds upon the notion of multilabel learning is presented in more detail. Our preliminary results from a real test case indicate that the performance of the intelligent module can reach quite high performance without a large amount of data.

  • 250.
    Gavrilis, Dimitris
    et al.
    Digital Curation Unit - IMIS, Athena Research Center, Maroussi.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Georgoulas, George
    Department of Informatics and Communications Technology, Technical Educational Institute of Epirus, 47100 Artas, Kostakioi, Department of Computer Engineering, TEI of Epirus, Arta.
    A One-Class Approach to Cardiotocogram Assessment2015Ingår i: 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society: EMBC 2015, Milan; Italy, 25-29 August 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 518-521, artikel-id 7318413Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cardiotocogram (CTG) is the most widely used means for the assessment of fetal condition. CTG consists of two traces one depicting the Fetal Heart Rate (FHR), and the other the Uterine Contractions (UC) activity. Many automatic methods have been proposed for the interpretation of the CTG. Most of them rely either on a binary classification approach or on a multiclass approach to come up with a decision about the class that the tracing belongs to. This work investigates the use of a one-class approach to the assessment of CTGs building a model only for the healthy data. The preliminary results are promising indicating that normal traces could be used as part of an automatic system that can detect deviations from normality.

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