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  • 51.
    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 Inelligent Assistant for Physicians2016Ingår i: 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Orlando, FL, 17-20 August 2016,, 2016Konferensbidrag (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.

  • 52.
    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.

  • 53.
    Georgoulas, George
    et al.
    Department of Informatics and Communications Technology, Technical Educational Institute of Epirus, 47100 Artas, Kostakioi, Department of Computer Engineering, TEI of Epirus, Arta.
    Karvelis, Petros
    Department of Computer Engineering, TEI of Epirus, Arta.
    Stylios, Chrysostomos
    Department of Informatics and Communications Technology, Technical Educational Institute of Epirus, 47100 Artas, Kostakioi, Department of Computer Engineering, TEI of Epirus, Arta.
    Tsoumas, Ioannis
    Siemens Industry Sector, Automation and Drives, Large Drives, Nuremberg, Germany, Large Drives, Products R&D Department, Siemes Inustry.
    Antonino-Daviu, Jose Alfonso
    Institute of Energy Engineering, University of Valencia, Spain.
    Hernandez, Jesus Corral
    Institute of Energy Engineering, University of Valencia, Spain.
    Alarcon, Vicente Climente
    Department of Electrical Engineering and Automation, Aalto University, Espoo.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Automatizing the detection of rotor failures in induction motors operated via soft-starters2016Ingår i: Annual Conference of the IEEE Industrial Electronics Society, IECON 2015: Yokohama, Japan, 9-12 Nov. 2015, Piscataway, NJ: IEEE Communications Society, 2016, s. 3743-3748, artikel-id 7392684Konferensbidrag (Refereegranskat)
    Abstract [en]

    Implementation of unsupervised induction motor condition monitoring systems has drawn an increasing attention recently among motor drives manufacturers. In the case of soft- starters the possibility of incorporating fault detection features to their conventional functions provides an added value to those elements. Design and development of advanced algorithms that are able to automatically detect and alert about possible failures without requiring continuous human inspection is an especially challenging research goal. In this paper, an algorithm for the automatic detection of rotor damages in induction motors in the case of soft starting is proposed. The twofold approach relies, first, on the application of a time-frequency transform to the starting current signal and, second, on a pattern recognition stage based on the treatment of the time-frequency representation as a symbolic sequence. The innovation of this work is the implementation of the proposed approach for the automatic detection of rotor cage faults in soft-started motors. The experimental results prove the usefulness of the approach for the automatic detection of such faults and its potential for possible future implementation in soft-started machines.

  • 54.
    Georgoulas, Georgios
    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.
    Bearing fault detection and diagnosis by fusing vibration data2016Ingår i: IECON Proceedings (Industrial Electronics Conference), Piscataway, NJ: IEEE Computer Society, 2016, s. 6955-6960, artikel-id 7794118Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article presents a simple method for the detection and diagnosis of bearing faults, by fusing the information coming from two accelerometers. The method relies on three simple and intuitive features, extracted from the data coming from accelerometers placed at two different sites of the system under investigation. Our preliminary results indicate that by using simple statistical measures, such as the elements of the covariance matrix of the two sensors, faults at an early stage can be detected. In our the proposed scheme, the extracted features are fed to a k-nearest neighbour classifier for diagnosis purposes or to an ensemble of one-class detectors, if only the information from normal situation is available. As it is proved, based on experimental results, in both scenarios a remarkably high detection/diagnostic performance is achieved.

  • 55.
    Carholt, Cristoffer
    et al.
    Luleå University of Technology.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fresk, Emil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andrikopoulos, Georgios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Design, Modelling and Control of a Single Rotor UAV2016Ingår i: 24th Mediterranean Conference on Control and Automation,: June 21-24, Athens, Greece, 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 840-845, artikel-id 7536015Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, a novel Vertical Take-Off and Landing (VTOL) Single Rotor Unmanned Aerial Vehicle (SR- UAV) will be presented. The SRUAV’s design properties will be analysed in detail, with respect to technical novelties outlining the merits of such a conceptual approach. The system’s model will be mathematically formulated, while a cascaded P-PI and PID-based control structure will be utilized in extensive simulation trials for the preliminary evaluation of the SR-UAV’s attitude and translational performance.

  • 56.
    Mustafa, Mohammed Obaid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Varagnolo, Damiano
    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.
    Detecting broken rotor bars in induction motors with model-based support vector classifiers2016Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 52, s. 15-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a methodology for testing the sanity of motors when both healthy and faulty data are unavailable. More precisely, we consider a model-based Support Vector Classification (SVC) method for the detection of broken bars in three phase asynchronous motors at full load conditions, using features based on the spectral analysis of the stator's steady state current (more specifically, the amplitude of the lift sideband harmonic and the amplitude at fundamental frequency). We diverge from the mainstream focus on using SVCs trained from measured data, and instead derive a classifier that is constructed entirely using theoretical considerations. The advantage of this approach is that it does not need training steps (an expensive, time consuming and often practically infeasible task), i.e., operators are not required to have both healthy and faulty data from a system for checking it. We describe what are the theoretical properties and fundamental limitations of using model based SVC methodologies, provide conditions under which using SVC tests is statistically optimal, and present some experimental results to prove the effectiveness of the suggested scheme.

  • 57.
    Mamikoglu, Umut
    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.
    Pauelsen, Mascha
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Varagnolo, Damiano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Röijezon, Ulrik
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Elbow Joint Angle Estimation by Using Integrated Surface Electromyography2016Ingår i: 24th Mediterranean Conference on Control and Automation (MED): June 21-24, Athens, Greece, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 785-790, artikel-id 7535891Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electromyography (EMG) signals represent the electrical activation of skeletal muscles and contain valuable information about muscular activity. Estimation of the joint movements by using surface EMG signals has great importance as a bio-inspired approach for the control of robotic limbs and prosthetics. However interpreting surface EMG measurements is challenging due to the nonlinearity and user dependency of the muscle dynamics. Hence it requires complex computational methods to map the EMG signals and corresponding limb motions. To solve this challenge we here propose to use an integrated EMG signal to identify the EMG-joint angle relation instead of using common EMG processing techniques. Then we estimate the joint angles for elbow flexion-extension movement by using an auto-regressive integrated moving average with exogenous input (ARIMAX) model, which takes integrated EMG measurements as input. The experiments showed that the suggested approach results in a 21.85% average increase in the estimation performance of the elbow joint angle compared to the standard EMG processing and identification.

  • 58.
    Mamikoglu, Umut
    et al.
    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.
    Röijezon, Ulrik
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Pauelsen, Mascha
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Electromyography Based Joint Angle Estimation and Control of a Robotic Leg2016Ingår i: 6th IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob 2016): June 26-29, Singapore, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 182-187, artikel-id 7523619Konferensbidrag (Refereegranskat)
    Abstract [en]

    Musculoskeletal modeling based on Electromyography (EMG) has many applications in physiotherapy and biologically-inspired robotics. In this article, a novel methodology for the modeling of the dynamics of an antagonistic muscle pair that actuates the human ankle joint movements will be established. As it will be presented, the musculoskeletal model is based on a multi input single output (MISO) auto-regressive integrated moving average with exogenous input (ARIMAX) model, which takes the integrated EMG measurements as input and estimates the corresponding joint angles. Based on this methodology, a Pneumatic Artificial Muscle (PAM) robotic leg setup that mimics the flexion/extension movement of human ankle joint is controlled to replicate the human movement. The experimental results demonstrate the performance of EMG based joint angle estimation and control of the robotic leg with the proposed model.

  • 59.
    Kanellakis, Christoforos
    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.
    Evaluation of Visual Localization Systems in Underground Mining2016Ingår i: 24th Mediterranean Conference on Control and Automation (MED): June 21-24, Athens, Greece, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 539-544, artikel-id 7535853Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article an evaluation of the current technology on visual localization systems for underground mining is presented. The proposed study is considered to be the first step among others towards enabling the vision of underground localization for Unmanned Micro Aerial Vehicles. Furthermore, the aim of this article, is to verify applicable and reliable low cost existing methods and technologies for the problem of UAV localization in underground, harsh mining environments and more specifically in one of the biggest mines in Europe, the iron ore mine of LKAB in Kiruna, Sweden. In the experimental trials, the sensors employed were a RGB-D camera, a Kinect 2 and a Playstation 3 Eye web camera used in two configurations, as a stereo rig and as a monocular visual sensor. The processing of the stored data from the experiments will provide an insight for the applicability of these sensors, while it will identify what further technological and research developments are required in order to develop affordable autonomous UAV solutions for improving the underground mining production processes.

  • 60.
    Vachtsevanos, George
    et al.
    School of Electrical and Computer, Engineering, Georgia Institute of Technology, Atlanta.
    Georgoulas, 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.
    Fault Diagnosis, Failure Prognosis and Fault Tolerant Control of Aerospace/Unmanned Aerial Systems2016Ingår i: 24th Mediterranean Conference on Control and Automation (MED): June 21-24, Athens, Greece, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 366-371, artikel-id 7536041Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fault-tolerant control and operation of complex unmanned and aircraft systems is an emerging technology intended to provide the designer and operator with flexibility, interoperability, sustainment and reliability under changing operational requirements or mission profiles. Moreover, it is intended to reconfigure online hardware and software to maintain the operational integrity of the system in the event of contingencies (fault/failure modes). This paper presents an hierarchical architecture that uses available sensor information, fault isolation, failure prognosis, system restructuring and controller reconfiguration. The fault tolerant control framework relies on prognostic information to reconfigure system components and preserve the operational integrity of the aircraft. The hierarchical structure starts at the lowest component level and migrates to the middle system/subsystem level ending with the final mission level. We illustrate the methodology using an electro-mechanical actuator (EMA).

  • 61.
    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.

  • 62.
    Small, Elias
    et al.
    Luleå University of Technology.
    Fresk, Emil
    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.
    Modelling and Control of a Tilt-Wing Unmanned Aerial Vehicle2016Ingår i: 24th Mediterranean Conference on Control and Automation: June 21-24, Athens, Greece, 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 1254-1259, artikel-id 7536050Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a Tilt-Wing Unmanned Aerial Ve- hicle (TW-UAV) and the preliminary evaluation of its hovering characteristics in extended simulation studies are presented. In the beginning, an overview of the TW-UAV’s design properties are established, highlighting the novelties of the proposed structure and the overall merits. The TW-UAV’s design and structural properties are mathematically modeled and utilized for the synthesis of a cascaded P-PI and PID based control structure for the regulation of its hovering performance. In addition, extensive simulation trials are performed in order to evaluate the structure’s efficiency in controlling the TW-UAV’s attitude and position under various noise and disturbance scenarios.

  • 63.
    Andrikopoulos, Georgios
    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.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras , Electrical and Computer Engineering Department, University of Patras.
    Novel Considerations on Static Force Modeling of Pneumatic Muscle Actuators2016Ingår i: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 21, nr 6, s. 2647-2659, artikel-id 7501612Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, an overview of the most significant static force modeling approaches of Pneumatic Muscle Actuators (PMAs) is presented, while a modified static force modeling approach, which is based on fundamental PMA modeling techniques, is proposed. In addition, the thermal expansion effect is considered as the main cause of the gradual shift in the PMA’s force-displacement relationship and the geometric properties, which are being affected by the thermal build-up occurring during PMA’s continuous operation, are incorporated into the static force models. The effects of thermal expansion are documented via experimental studies and the acquired force-displacement data are utilized for the validation of the proposed modeling method in PMAs of different nominal dimensions and at constant test pressures. Finally, an additional evaluation is performed via the comparison of the accuracy between the proposed model and the existing geometric static modeling approaches.

  • 64.
    Wuthier, David
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Kominiak, Dariusz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Kanellakis, Christoforos
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andrikopoulos, Georgios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fumagalli, Matteo
    Aalborg University.
    Schipper, G.
    University of Twente.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    On the Design, Modeling and Control of a Novel Compact Aerial Manipulator2016Ingår i: 24th Mediterranean Conference on Control and Automation, MED 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 665-670, artikel-id 7536029Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to present a novel fourdegree-of-freedom aerial manipulator allowing a multirotorUnmanned Aerial Vehicle (UAV) to physically interact with theenvironment. The proposed design, named CARMA (CompactAeRial MAnipulator), is characterized by low disturbances onthe UAV flight dynamics, extended workspace (with regard toits retracted configuration) and fast dynamics (compared to theUAV dynamics). The dynamic model is formulated and a controlstructure consisting of an inverse kinematics algorithm and independentjoint position controllers is presented. Furthermore,the design specifications of the prototype are analyzed in detail,while experimental evaluations are conducted for the extractionof the manipulator’s workspace and the evaluation of system’stracking capabilities over pick-and-place trajectories. Finally,it is shown that the selected joint position sensors, combinedwith the derived inverse dynamic algorithm allow to determinethe wrenches exerted at the base, due to swift motions of thearm.

  • 65.
    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.

  • 66.
    Georgoulas, Georgios
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Alarcon, Vicente Climente
    Department of Electrical Engineering and Automation, Aalto University, Espoo.
    Dritsas, Leonidas
    University of Patras, Department of Electrical Engineering.
    Antonino-Daviu, Jose Alfonso
    Institute of Energy Engineering, University of Valencia, Spain.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Start-up analysis methods for the diagnosis of rotor asymmetries in induction motors-seeing is believing2016Ingår i: 24th Mediterranean Conference on Control and Automation (MED): June 21-24, Athens, Greece, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 372-377, artikel-id 7536045Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article presents a qualitative analysis of different methods proposed for the diagnosis of broken rotor bars using the stator current during start-up operation. The slip dependent components, caused by the asymmetry, which is created by the breakage of rotor bar(s) and especially the left sideband harmonic (LSH) component, can create a distinctive pattern in a time- frequency plane. Short Time Fourier Transform, Wavelet analysis, and Winger-Ville Distribution are evaluated by using signals coming from motors operating in real industrial settings. The corresponding analysis presents the pros and the cons of these approaches for their potential application under realistic industrial conditions using the larger number of real life cases encountered in the literature.

  • 67.
    Andrikopoulos, Georgios
    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.
    Kominiak, Dariusz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Unander-Scharin, Åsa
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Musik och dans.
    Towards the Development of a Novel Upper-Body Pneumatic Humanoid: Design and Implementation2016Ingår i: 2016 European Control Conference, ECC 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 395-400, artikel-id 7810317Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the conceptual design of a 14 Degree-of-Freedom (DOF) upper-body pneumatic humanoid is presented. The movement capabilities of this novel robotic setup are achieved via Pneumatic Artificial Muscles (PAMs), a form of actuation possessing crucial attributes for the development of biologically-inspired robots. To evaluate the feasibility of the humanoid’s design properties, a 5-DOF robotic arm is developed and experimentally tested, while being studied from the scope of implementing a robotic structure capable of producing smooth and human-like motion responses, while maintaining the inherent compliance provided by the PAM technology.

  • 68.
    Georgoulas, George
    et al.
    Department of Informatics and Communications Technology, Technical Educational Institute of Epirus, 47100 Artas, Kostakioi, Department of Computer Engineering, TEI of Epirus, Arta.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mustafa, Mohammed Obaid
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A Data Fusion Approach to Bearing Fault Detection and Diagnosis2015Ingår i: IEEE International Conference on Power Engineering, Energy and Electrical Drives, POWERENG 2015, May 11-13, Riga, Latvia, 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 109-113Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a data fusion approach for the diagnosis of bearing faults under different seeded fault scenarios. The approach is based on the extraction of three simple and intuitive features that fuse the information that comes from two accelerometers placed at two different sites of the test bed. The analysis shows that in the case of the occurrence of a fault even in an early stage the “footprint” left at the scatter plot of the measurements coming from the two accelerometers can effectively turned into features/descriptors by simple statistical measures such as the elements of the covariance matrix. Those features when fed to a k-nearest neighbor classifier or an ensemble of one class detectors can lead to a remarkably high detection/diagnostic performance.

  • 69.
    Nayl, Thaker
    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 Full Error Dynamics Switching Modeling and Control Scheme for an Articulated Vehicle2015Ingår i: International Journal of Control, Automation and Systems, ISSN 1598-6446, E-ISSN 2005-4092, Vol. 13, nr 5, s. 1221-1232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a complete analysis towards the development of a switching modeling and control framework for an articulated vehicle, under the effect of varying slip angles will be presented. The established nonlinear kinematic model, of the nonholonomic articulated vehicle, will be transformed into an error dynamics model, which in the sequel will be linearized around multiple nominal slip angle cases. The proposed control architecture will consist of a switching control scheme, based on multiple model predictive controllers, for the articulated vehicle under varying slip angles. The controllers will be developed in order to improve the performance of the articulated vehicle's path tracking, while compensating the varying slippage effect. The current measured slip angle is being considered as the switching rule and a corresponding switching control scheme is being defined, being able to apply constraints on the states, the control signal and the output variables. Both the non-slip and slip models will be derived to highlight the significance of accounting for slips in path following control and their significant effect on deteriorating the performance of the overall control scheme when not considered. Multiple simulation results will be presented to prove the efficacy of the overall suggested scheme.

  • 70.
    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.

  • 71.
    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.

  • 72.
    Nikolakopoulos, George
    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.
    Martinsson, Pär-Erik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. ProcessIT Innovations.
    Andersson, Ulf
    Mine Tek HB, Kiruna.
    A Vision of Zero Entry Production Areas in Mines2015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This industrial article aims in presenting a short roadmap on the identified activities and technologies needed towards the vision of zero entry production areas in Mines. This work has been performed in close cooperation with large mining companies in Europe as part of the Smart Mine of the Future Research, Development and Innovation Program and will present the most important areas that it is expected the robotic technology to have an impact on.

  • 73.
    Mustafa, Mohammed Obaid
    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.
    Broken Bars Fault Diagnosis Based on Uncertainty Bounds Violation for Three Phase Induction Motors2015Ingår i: International Studies in Religion and Society, ISSN 1530-1311, E-ISSN 2050-7038, s. 304-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a novel fault diagnosis scheme, based on uncertainty bounds violation, is being presented for the case of broken bars in squirrel–cage Three Phase Induction Motors. The fault diagnosis is done in two steps. Firstly the parameters of the healthy induction motor are identified using a set member- ship identification (SMI) approach, where corresponding uncertainty bounds are also being provided. Secondly the proposed uncertainty bounds violation conditions for the fault diagnosis are evaluated on–line, on the converged identified model, during a sliding time window. Multiple simulation results are presented that demonstrate the efficacy of the proposed scheme towards fault detection and diagnosis among different number of broken bars.

  • 74.
    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.

  • 75.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Design and Development of an Exoskeletal Wrist Prototype via Pneumatic Artificial Muscles2015Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, nr 11, s. 2709-2730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Full or partial loss of function in the shoulder, elbow or wrist is an increasingly common ailment caused by various medical conditions like stroke, occupational and sport injuries, as well as a number of neurological conditions, which increases the need for the development and improvement of upper limb rehabilitation devices. In this article, the design and implementation of the EXOskeletal WRIST (EXOWRIST) prototype is presented. This novel robotic appliance’s motion is achieved via pneumatic artificial muscles, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. Furthermore, the EXOWRIST’s properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees-of-freedom movement capabilities (extension-flexion, ulnar-radial deviation) are experimentally evaluated via a PID- based control algorithm. Experimental results involving initial testing of the proposed exoskeleton on a healthy human volunteer for the preliminary evaluation of the EXOWRIST’s attributes are also presented.

  • 76.
    Mansouri, Sina Sharif
    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.
    Distributed Model Predictive Control for Unmanned Aerial Vehicles2015Ingår i: 2015 Workshop on Research, Education and Development of Unmanned Aerial Systems: RED-UAS 2015, Cancun, Mexico, 23 - 25 November 2015, Picataway, NJ: IEEE Communications Society, 2015, s. 152-161, artikel-id 7441002Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a distributed model pre- dictive control scheme, for the cooperative motion control of Unmanned Aerial Vehicles (UAVs) is be- ing presented. The UAVs are modeled by a 6-DOF nonlinear kinematic model. Two different control ar- chitectures: a centralized and a distributed MPC, are studied and evaluated in simulation experiments. In the centralized approach, one central MPC controller is responsible for the movement coordination of all the UAVs, while in the distributed approach each aerial vehicle plans only for its own actions, while the objective function is coupled with the behavior of the rest of the team members and the constraints are decoupled. In this approach, each agent only shares the future position of itself with the other agents to avoid collisions. For reducing the computation time and complexity, only one step ahead prediction in the corresponding MPC schemes have been considered without a loss of generality. Finally, the efficiency of the overall suggested decentralized MPC scheme, as well as it comparison with the centralized approach, is being evaluated through the utilization of multiple simulation scenarios.

  • 77.
    Nayl, Thaker
    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.
    Effect of Kinematic Parameters on MPC based On-line Motion Planning for an Articulated Vehicle2015Ingår i: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 70, s. 16-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this article is to analyze the effect of kinematic parameters on a novel proposed on-line motion planning algorithm for an articulated vehicle based on Model Predictive Control. The kinematic parameters that are going to be investigated are the vehicle's velocity, the maximum allowable change in the articulated steering angle, the safety distance from the obstacles and the total number of obstacles in the operating arena. The proposed modified path planning algorithm for the articulated vehicle belongs to the family of Bug-Like algorithms and is able to take under consideration, the mechanical and physical constraints of the articulated vehicle, as well as its full kinematic model. During the on-line motion planning algorithm, the MPC controller controls the lateral motion of the vehicle, through the rate of the articulation angle, while driving it accurately and safely over the on-line formulated desired path. The efficiency of the proposed combined path planning and control scheme is being evaluated under numerous simulated test cases, while exhaustive simulations have been made for analyzing the dependency of the proposed framework on the kinematic parameters.

  • 78.
    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.

  • 79.
    Mustafa, Mohammed Obaid
    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.
    Georgoulas, George
    Department of Informatics and Communications Technology, Technical Educational Institute of Epirus, 47100 Artas, Kostakioi, Department of Computer Engineering, TEI of Epirus, Arta.
    Fault classification of Broken Rotor Bars in Induction Motors Based on Envelope Current Analysis2015Ingår i: IEEE 13th International Conference on Industrial Informatics (INDIN), 2015: Cambridge, United Kingdom, 22-24 July 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 795-800, artikel-id 7281838Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a method for the fault classification of one, two, and three broken bars in induction motors under full load condition is presented. The proposed methodology is based on the current envelope analysis, which in the past has been also widely utilized in analyzing the rotor faults at low slips. As it will be presented, the information obtained from the envelope current is valuable in manifesting and validating the presence of fault, since the current envelope and its characteristics often contains important information about the existence of a fault and the corresponding fault type. The proposed method mainly focuses on the case of steady-state operation under full load. In the established fault detection scheme, from the stator’s current six statistical features are extracted and utilized for the fault detection and classification. In more detail, three classifiers, a linear, a quadratic and a Nearest Neighbor have been investigated for the diagnosis of broken rotor bar faults of an induction motor. The presented approach have manifested promising results using experimental data.

  • 80.
    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.

  • 81.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Incorporation of Thermal Expansion in Static Force Modeling of Pneumatic Artificial2015Ingår i: IEEE Mediterranean Conference on Control and Automation, Torremolinos, Spain, June, 16-19, 2015 / [ed] V. Munoz, Piscataway, NJ: IEEE Communications Society, 2015, s. 414-420, artikel-id 7158784Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the thermal expansion effect is considered as the main cause of the gradual shift in the force- displacement relationship, which describes the operation of Pneumatic Artificial Muscles (PAMs). A modified static force modeling approach is proposed, based on fundamental PAM modeling techniques, while incorporating the geometrical properties that are being affected by the thermal build-up occurring during PAM’s continuous operation. The effects of thermal expansion are documented via experimental studies and the acquired data are utilized for the validation of the proposed modeling method. Further evaluation is performed via comparison of modeling accuracy between the proposed modeling approach and the fundamental static force modeling techniques.

  • 82.
    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.

  • 83.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Motion control of a novel robotic wrist exoskeleton via pneumatic muscle actuators2015Ingår 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 7301464Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the motion control problem of a robotic EXOskeletal WRIST (EXOWRIST) prototype is considered. This novel robotic appliance’s motion is achieved via pneumatic muscle actuators, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. The EXOWRIST’s properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees- of-freedom movement capabilities (extension-flexion, ulnar- radial deviation) are experimentally evaluated on a healthy human volunteer via an advanced nonlinear PID-based control algorithm.

  • 84.
    Giannakas, Theodoros
    et al.
    University of Patras.
    Andrikopoulos, Georgios
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    On Energy Optimization of a Pulp and Paper Refiner based on Model Predictive Control2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to investigate and examine the modeling and control problem of the papermaking’s sub-process also known as pulp refining. The existing modeling approaches developed for the pulp and paper refining process are being investigated, while the most important model approximations, extracted from the existing related literature, are being simulated and examined in detail. The main goal of the article is to determine whether the modeling approaches of the pulp and paper refining process can be successfully controlled via a Model Predictive Control (MPC) based structure and at which extend this could lead in a better control scheme and in an overall energy optimization. Extensive simulation trials are being carried out, where the MPC parameters are being fine-tuned through trial-and-error sequences in order for examining the overall performance in controlling the various modeling approaches of the process. In order to further evaluate the efficacy of the proposed control scheme, the MPC related results are being compared to experimental data extracted from a real refining system that utilized a generic industrial controller.

  • 85.
    Lindqvist, Adrian
    et al.
    Luleå University of Technology.
    Fresk, Emil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Optimal Design and Modeling of a Tilt Wing Aircraft2015Ingår i: IEEE Mediterranean Conference on Control and Automation, Torremolinos, Spain, June 16-19, 2015 / [ed] V. Munoz, Piscataway, NJ: IEEE Communications Society, 2015, s. 701-708, artikel-id 7158828Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this article is to present an optimal model for the behavior of a tilt wing aircraft during its transition state. A tilt wing aircraft is a hybrid between a helicopter and a plane, which has the capabilities of both parts, meaning that it can stand still and hover and by tilting its wing 90 degrees to act like a regular plane. Overall, a tilt rotor aircraft has the extended merits of vertical take offs and landings, to stand still and hover in mid air, while being able to travel in long distances efficiently. The novelty of this article stems from: a) the analysis of the aircraft during the transition between helicopter mode and plane for the angles between 0-90 degrees, b) the comparison between the model extracted from the simulations and tests from a wind tunnel, and c) the proposal for an optimal design for a tilt wing UAV. The efficiency of the proposed modeling approach has been evaluated in multiple simulated and experimental verification.

  • 86.
    Mustafa, Mohammed Obaid
    et al.
    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.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Principal Component Analysis Anomaly Detector for Rotor Broken Bars2015Ingår i: IECON 2014: 40th Annual Conference of the IEEE Industrial Electronics Society, Dallas, TX, USA , Oct. 29 2014 - Nov. 1 2014, Piscataway, NJ: IEEE Communications Society, 2015, s. 3462-3467Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a method for the detection of broken rotor bars in asynchronous machines operating under full load is presented. Unlike most Motor Current Signature Analysis (MCSA) approaches, which operate in the frequency domain, our method operates in the time domain. The scheme is based on the use of a Principal Component Analysis (PCA) fault/anomaly detector applied on the three stator currents to calculate the Q statistic which is employed for detecting a fault. The efficiency of the proposed scheme was experimentally evaluated using different fault severity levels, ranging from 1/4 of a broken bar to three broken bars. The obtained results indicate that the method can detect the caused asymmetry with a very restricted amount of data.

  • 87.
    Karvelis, Petros
    et al.
    Department of Computer Engineering, TEI of Epirus, Arta.
    Georgoulas, George
    Department of Computer Engineering, TEI of Epirus, Arta.
    Stylios, Chrysostomos
    Department of Computer Engineering, TEI of Epirus, Arta.
    Tsoumas, Ioannis
    Large Drives, Products R&D Department, Siemes Inustry.
    Antonino-Daviu, Jose Alfonso
    Institute of Energy Engineering, University of Valencia, Spain.
    Hernandez, Jesus Corral
    Institute of Energy Engineering, University of Valencia, Spain.
    Alarcon, Vicente Climente
    Department of Electrical Engineering and Automation, Aalto University, Espoo.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Symbolic time series analysis of the soft starting transient in induction machines2015Ingår i: 2015 IEEE International Conference on Industrial Technology (ICIT 2015) to be held in Seville, Spain, March 17-19, 2015.: Seville, Spain, March 17-19, 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 3243-3248Konferensbidrag (Refereegranskat)
    Abstract [en]

    Induction motors are in the heart of almost every production line especially due to their robustness under harsh environments. Nevertheless, even induction machines are prone to faults. Among them, the faults related to the breakage of rotor bars have received special attention by the research community with a number of methods proposed both for the case of steady state as well as for transient operation. For the latter, methods relying on the analysis of the start-up transient have proven to be able to effectively isolate the faulty component that is created by the asymmetry caused by the bar breakage. However, very little work has been done concerning the soft starting of induction machines. In this work, preliminary results of the application of a symbolic time series technique for the analysis of the transient, when the motor is controlled by a soft starter, will be presented and experimentally evaluated.

  • 88.
    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.

  • 89.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Advanced nonlinear PID-based antagonistic control for pneumatic muscle actuators2014Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 12, s. 6926-6937, artikel-id 6786031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the positioning control problem of pneumatic muscle actuators (PMAs) is being considered. A two-degree-of-freedom nonlinear proportional-integral-derivative structure is being synthesized, providing ameliorated compensation of the PMAs' nonlinear hysteretic phenomena and advanced robustness through disturbance cancellation. Experimental studies are being utilized to prove the overall efficiency of the proposed control scheme with regard to set-point tracking performance for the position control of a single PMA, torsion angle control of a nonsymmetrical antagonistic PMA setup, and disturbance rejection in both single and antagonistic control scenarios.

  • 90.
    Alhashimi, Anas
    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.
    An improvement in the observarion model for Monte Carlo localization2014Konferensbidrag (Refereegranskat)
  • 91.
    Nikolakopoulos, George
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Dritsas, Leonidas
    University of Patras, Department of Electrical Engineering.
    Sayyaddelshad, Saleh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Combined networked switching output feedback control with D-region stability for performance improvement2014Ingår i: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 87, nr 6, s. 1172-1180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a combined networked switching output feedback control scheme, with a (Formula presented.)-region stability performance improvement module is presented. The network induced time delays, that are considered to be time varying and integer multiples of the sampling period, are being embedded in the system model, by state augmentation. The resulting model of the overall networked closed-loop system is switching, with the current measured round-trip time delay acting as the switching rule. Based on this modelling approach, a Linear Matrix Inequality (LMI) tuned switching output feedback controller is designed. The proposed approach establishes robustness against time delays and is able to guarantee the overall stability of the switching closed-loop system. Integrated in the controlled synthesis phase, an LMI tuned performance improvement module is being introduced, based on (Formula presented.)-region stability. Multiple simulation results are being presented that prove the efficacy of the proposed scheme.

  • 92.
    Alexis, Kostas
    et al.
    Swiss Federal Institute of Technology.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Tzes, Anthony
    University of Patras.
    Experimental Constrained Optimal Attitude Control of a Quadrotor subject to Wind Disturbances2014Ingår i: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 12, nr 6, s. 1289-1302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The design and experimental verification of a Constrained Finite Time Optimal Controller (CFTOC) for attitude maneuvers of an Unmanned Quadrotor operating under severe wind conditions is the subject of this article. The quadrotor’s nonlinear dynamics are linearized in various operating points resulting in a set of piecewise affine models. The CFTO–controller is designed for set-point maneuvers taking into account the switching between the linear models and the state and actuation constraints. The control scheme is applied on experimental studies on a prototype quadrotor operating both in absence and under presence of forcible atmospheric disturbances. Extended experimental results indicate that the proposed control approach attenuates the effects of induced wind–gusts while performing accurate attitude set–point maneuvers.

  • 93.
    Nyberg, Rickard
    et al.
    Luleå tekniska universitet.
    Kominiak, Dariusz
    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 modied obstacle based potential field algorithm for an off-road mobile robot2014Konferensbidrag (Övrigt vetenskapligt)
  • 94.
    Nyberg, Rickard
    et al.
    Luleå tekniska universitet.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Kominiak, Dariusz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Experimental Evaluation of a Modified Obstacle Based Potential Field Algorithm for an Off-Road Mobile Robot2014Ingår i: Proceedings of the 11th International Conference on Informatics in Control, Automation and Robotics: ICINCO 2014, Vienna, Austria 1 - 3 September 2014 / [ed] J. Felipe, SciTePress, 2014, Vol. 1, s. 626-633Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article presents an experimental evaluation of a modified obstacle based artificial potential field algorithm for an off-road mobile robot. The first contribution of the presented approach concerns the transformation of the artificial potential field method for the guidance of the vehicle and obstacle avoidance, in order to make it suitable for utilising a visual feedback. The visual feedback is relying on a depth image, provided by the low cost kinect sensor. The second contribution concerns the proposal of a novel scheme for the identification and perception of obstacles. Based on the proposed methodology, the vehicle is capable of categorising the obstacles based on their height in order to alter the calculated forces, for enabling a cognitive decision regarding their avoidance or the driving over them, by utilising the robot’s off road capabilities. The proposed scheme is highly suggested for off road robots, since in the normal cases, the existence of small rocks, branches, etc. can be accidentally identified as obstacles that could make the robot to avoid them or block its further movement. The performance of the proposed modified potential field algorithm has been experimentally applied and evaluated in multiple robotic exploration scenarios, where from the obtained results the efficiency and the advantages of such a modified scheme have been depicted.

  • 95.
    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.

  • 96.
    Mustafa, Mohammed Obaid
    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.
    Fault classification scheme for three phase induction motor2014Ingår i: International Journal of System Dynamics Applications, ISSN 2160-9772, E-ISSN 2160-9799, Vol. 3, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article a fault classification algorithm based on a robust linear discrimination scheme, for the case of a squirrel–cage three phase induction motor, will be presented. The suggested scheme is based on a novel feature extraction mechanism from the measured magnitude and phase of current park’s vector pattern. The proposed methodology has the merit to diagnose different types of faults such as: a) broken rotor bar, and b) short circuit in stator winding. The novel feature generation technique is able to transform the problem of fault detection and diagnosis into a simpler space, where direct robust linear discrimination can be applied for solving the classification problem. Robust linear discrimination has been one of the most widely used fault detection method in real life applications, as this methodology seeks for directions that are efficient for discrimination and at the same time applies a straight forward implementation. The efficacy of the proposed scheme will be evaluated based on multiple simulation results for different fault types.

  • 97.
    Alhashimi, Anas
    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.
    Observation model for Monte Carlo Localization2014Konferensbidrag (Övrigt vetenskapligt)
  • 98.
    Alexis, Kostas
    et al.
    Department of Electrical and Computer Engineering, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Tzes, Anthony
    Department of Electrical and Computer Engineering, University of Patras.
    On trajectory tracking model predictive control of an unmanned quadrotor helicopter subject to aerodynamic disturbances2014Ingår i: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625, Vol. 16, nr 1, s. 209-224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article a Model Predictive Control (MPC) strategy for the trajectory tracking of an unmanned quadrotor helicopter is presented. The quadrotor’s dynamics are modeled by a set of Piecewise Affine (PWA) systems around different operating points of the translational and rotational motions. The proposed control scheme is dual and is consisted by an integral MPC for the translational motions, followed by a MPC–scheme for the quadrotor’sattitude motions’ tracking. By the utilization of PWA representations, the controller is computed for a larger part of the quadrotor’s flight envelope. Theproposed dual control scheme is able to calculate optimal control actions with robustness against atmospheric disturbances (e.g. wind gusts) and physical constraints of the quadrotor (e.g. maximum lifting forces or fixed thrust limitations in order to extend flight endurance). Extended simulation studies prove the efficiency of the MPC–scheme, both in trajectory tracking and aerodynamic disturbances attenuation.

  • 99.
    Nayl, Thaker
    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.
    Path Planning With Obstacle Avoidance and Sliding Mode Control for An Articulated Vehicle.2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    A dynamic obstacle avoidance technique and control strategy to derive an articulated vehicle has been proposed. The strategy consists of two elements: a path planning and controller scheme to make the vehicle track a reference path. Potential field algorithm is exploited to generate a free collision on-line reference path in dynamic environments. The potential field is modified, by considering the nonlinear kinematic model, of the articulated vehicle. The proposed sliding mode controller is capable of making the vehicle move in minimum error displacement.

  • 100.
    Nayl, Thaker
    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.
    Real-Time Bug-LIke Dynamic Path Planning for an Articulated Vehicle2014Ingår i: Informatics in Control, Automation and Robotics, Switzerland: Springer International Publishing , 2014, s. 201-215Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    This article proposes a novel real time bug like algorithm for performing a dynamic smooth path planning scheme for an articulated vehicle under limited and sensory reconstructed surrounding static environment. In the general case, collision avoidance techniques can be performed by altering the articulated steering angle to drive the front and rear parts of the articulated vehicle away from the obstacles. In the presented approach factors such as the real dynamics of the articulated vehicle, the initial and the goal configuration (displacement and orientation), minimum and total travel distance between the current and the goal points, and the geometry of the operational space are taken under consideration to calculate the update on the future way points for the articulated vehicle. In the sequel the produced path planning is iteratively smoothed online by the utilization of Bezier lines before producing the necessary rate of change for the vehicle’s articulated angle. The efficiency of the proposed scheme is being evaluated by multiple simulation studies that simulate the movement of the articulated vehicle in open and constrained spaces with the existence of multiple obstacles.

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