Control of Mobile Robots in the Robotized Wireless Sensor Networks
Professor Andon V. Topalov
Control Systems, Technical University of Sofia at the Plovdiv campus
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Discovering and monitoring of polluted areas using autonomous mobile robots is nowadays a frequently considered solution concerning both environmental and human safety problems. Being part of a distributed control system, such robots can help to improve the efficiency of the existing conventional pollution prevention systems. The environmental monitoring problems have been until recently approached by building fixed networks of sensors, collecting and exchanging measurements in order to estimate the location of the source of pollution and determine the perimeter of the polluted area. They use reference nodes (nodes with known locations) and thus require expensive and time-consuming deployment, calibration, and recovery operations. In addition, the above strategy limits the coverage area.
An alternative concept is to use groups of robots equipped with appropriate sensors that are capable to move towards the location of the source of pollution in a cooperative manner. This approach requires resolving many challenging technical problems such as endurance, planning, coordination, communication, cooperation, and navigation of the vehicles, but has advantages that it is more dynamic, flexible, and suitable for multiple source localization. Autonomous robotized vehicles can be also very appropriate for long-time surveillance of contaminated areas and monitoring the movements of threats with real-time data from multiple mobile sensors. Furthermore, robots are also capable to manipulate the environment and to take some samples from it.
On the other hand, during the last decade, wireless sensor networks (WSN) have provoked the interest of specialists from different areas by imposing large number of theoretical and practical challenges related to their implementation. The interaction of collective robotics and mobile wireless sensor networks (WSNs) has led to the creation of robotized WSNs. In such networks robots can play an important role, and integrating static nodes with mobile robots enhances the capabilities of both types of devices and enables new applications. The inclusion of robotized agents into the WSN structure can provide additional flexibility with respect to the installation of the network sensors and allow reliable information gathering and transfer. Our research attempts to propose a possible way for building robotized WSNs based on MQTT (Message Queue Telemetry Transport protocol) cloud computing that can be suitable for solving different environmental monitoring tasks. The goal is to transform the WSN into an adaptive sensor system with intelligent behavior, capable to discover and track spots or areas where given monitored environmental parameters violate defined thresholds. The proposed algorithmic methods have been tested on a pre-built laboratory prototype of a hybrid robotized WSN.


Prof. Dr. Andon V. Topalov received the MSc degree in Control Engineering from the Faculty of Information Systems, Technologies, and Automation at Moscow State University of Civil Engineering (MGGU) in 1979. He then received his PhD degree in Control Engineering from the Department of Automation and Remote Control at Moscow State Mining University (MGSU), Moscow, in 1984. From 1985 to 1986, he was a Research Fellow in the Research Institute for Electronic Equipment, ZZU AD, Plovdiv, Bulgaria. In 1986, he joined the Department of Control Systems, Technical University of Sofia at the Plovdiv campus, were he is presently a Full Professor. He has held long-term visiting Professor/Scholar positions at various institutions in South Korea, Turkey, Mexico, Greece, Belgium, UK, and Germany. He has co-authored one book, edited one book, and authored or co-authored more than 90 research papers in conference proceedings and journals. His current research interests are in the fields of intelligent control and robotics.

Meshfree Alternative Numerical Methods for Sustainable Engineering
Professor Kamal Mohammedi
Head of MESOnexTeam/ URMPE Research unit,Modelling, Simulation and Optimization of Alternative and Sustainable Systems email | website | Google Scholar Profile

The classical numerical methods, e.g. finite differences, finite volumes, and finite elements are based on meshes built from nodes. Each node has a number of predefined neighbors. Connectivity between neighboring nodes is used to define mathematical operators e.g. derivation, integration, etc. However, numerical methods with meshes have limitations in the following cases: Complex 3D geometries, difficult meshing requiring human assistance, creation or destruction of nodes (crack propagation simulation), problematic geometry misalignment for a fixed mesh in simulations of bending, non-linearities, discontinuities or singularities, etc. . The degeneration of the mesh during the simulation requires a remeshing operation which can introduce errors. In the case of deformable boundaries (multiphase flows …) or large deformations (plastic materials, etc.), it is very difficult to maintain the connectivity of the mesh without introducing any error during the simulation. The set of limitations of Numerical Methods based on Meshes has naturally led many researchers to develop new numerical meshfree or meshless methods using nodes (particles) but no longer a mesh. Implementation of meshless Methods differs from Finite Element Methods only by the shape functions construction and nodes generation. Finally, it is useful to point out that the ideal meshless method has not yet emerged.


Pr Kamal MOHAMMEDI is a Senior Lecturer of Applied Numerical Methods, Multiphase Flows, Solar Thermal Energy and Renewable Energy, since 1993, at M. Bougara University, Boumerdès/ Algeria, Department of Mechanical Engineering.
He received his M Sc. degree in Mechanical Engineering from Boumerdès National Institute of Mechanical Engineering (INGM) Algeria, in 1985 and his Diplôme d’Etudes Approfondies and PhD degrees in Process Engineering from the INSA de Lyon, France, in 1992. Head of the Modelling Simulation and Optimization of Alternative and Sustainable Systems (MESOnexTeam), he has been involved in 2 FP6 European projects and 10 national projects in the fields of hybrid renewable energy systems, Renewable Energy Desalination, CSP, Sustainable Industrial parks, Carbone Dioxide mitigation in cement industry, Energy Efficiency, etc. . He is the author and co-author of more than 40 published papers; book chapters and 100 conference articles in the fields of Concentrated Solar Power, Hybrid Renewable Energy Systems, and multiphase flows interface tracking. He is a member of scientific committees and a reviewer of national and International journals. He is a member of advisory boards of national and international conferences where he chaired sessions. He supervised Master/Engineer/Magister and PhD theses and consults for industry.

Design for reliability in power electronic systems
Professor Frede Blaabjerg
email | website | ResearchGate | Google Scholar Profile

In recent years, the automotive and aerospace industries have brought stringent reliability constraints on power electronic converters because of safety requirements. Today customers of many power electronic products expect up to 20 years of lifetime and they also want to have a “failure free period” and all with focus on the financials. The renewable energy sectors are also following the same trend, and more and more efforts are being devoted to improving power electronic converters to account for reliability with cost-effective and sustainable solutions. Thispresentation will introduce the recent progress in the reliability aspect study of power electronic converters for power electronic applications with special focus on renewables. It will cover the following contents: the motivations for highly reliable electric energy conversion in renewable energy systems; the reliability requirements of typical renewable energy systems and its implication on the power electronic converters; failure mechanisms and lifetime models of key power electronic components (e.g., power semiconductor switches, capacitors, and fans); long-term mission profiles in Photovoltaic (PV) and wind power applications and the component level stress analysis; reliability analysis methods, tools, and improvement strategies of power electronic converters for renewable energy systems. A few case studies on PV and wind power based renewable energy systems will also be discussed.


Frede Blaabjerg (S’86–M’88–SM’97–F’03) was with ABB-Scandia, Randers, Denmark, from 1987 to 1988. From 1988 to 1992, he got the PhD degree in Electrical Engineering at Aalborg University in 1995. He became an Assistant Professor in 1992, an Associate Professor in 1996, and a Full Professor of power electronics and drives in 1998. From 2017 he became a Villum Investigator.

His current research interests include power electronics and its applications such as in wind turbines, PV systems, reliability, harmonics and adjustable speed drives. He has published more than 450 journal papers in the fields of power electronics and its applications. He is the co-author of two monographs and editor of 6 books in power electronics and its applications.

He has received 18 IEEE Prize Paper Awards, the IEEE PELS Distinguished Service Award in 2009, the EPE-PEMC Council Award in 2010, the IEEE William E. Newell Power Electronics Award 2014 and the Villum Kann Rasmussen Research Award 2014. He was the Editor-in-Chief of the IEEE TRANSACTIONS ON POWER ELECTRONICS from 2006 to 2012. He has been Distinguished Lecturer for the IEEE Power Electronics Society from 2005 to 2007 and for the IEEE Industry Applications Society from 2010 to 2011 as well as 2017 to 2018.

He is nominated in 2014, 2015 and 2016 by Thomson Reuters to be between the most 250 cited researchers in Engineering in the world. In 2017 he became Honoris Causa at University Politehnica Timisoara (UPT), Romania.

Professor Sedat Sünter

Wound rotor induction machines (WRIM) are used at high power applications since their rotor windings are easily accessible to control the speed and torque of the machine. One of these applications is slip energy recovery drive systems. The slip power can be extracted and returned back to the supply through the back to back converter system. The topology known as Scherbius drive, employs a doubly-fed wound-rotor induction motor using an ac-dc-ac converter in the rotor circuit. However, the converter requires two-stage power conversion, namely rectification and inversion, which demands a complicated control strategy and large dc link capacitors, making the system bulky and expensive. In addition, the system allows the motor operating only at subsynchronous speed region if uncontrolled rectifier is used. An attractive solution is to use back-to-back PWM converters connected between rotor side and mains. However, complex control strategy of the converter and large dc link capacitors make the system bulky and costly. Another approach to achieve bidirectional power flow in the circuit is to use a line-commutated cycloconverter in which the ac power conversion is performed in single stage. By using the cycloconverter in slip energy recovery drive system it is possible to operate at both subsynchronous and supersynchronous speed regions. However, cycloconverters cause harmonic pollution both at the supply side and the motor side since their output contains several harmonic frequencies, and the input power factor is very low due to natural communication. In addition, in line-commutated cycloconverters the maximum rotor frequency is approximately one-third of supply frequency with near-sinusoidal low-frequency voltage and current. This corresponds to operation at 67% of synchronous speed.As an attractive and efficient solution, matrix converters can be used to control the speed and the rotor-side currents of wound-rotor induction motor. Such a configuration can offer the advantages given by its back-to-back counterpart while converting ac power in a single stage and eliminating the large dc link capacitor. The control scheme required by a direct ac-ac conversion scheme is simpler than that of a two-stage power conversion. The maximum rotor frequency limitation in the cycloconverter is also eliminated by the use of the matrix converter.In addition, operation at both subsynchronous and supersynchronous regions is possible with the proposed drive system.Simulation studies of the proposed doubly-fed induction motor drive system with rotor-side field oriented control verify the good control performance of the system in transient and steady-state conditions.
Another application of the WRIM is a wind energy conversion system which consists of a variable speed wind turbine with doubly-fed induction generator (DFIG) fed by either an ac-dc-ac converter or a direct ac-ac converter. Because of the disadvantages of the ac-dc-ac converter systems and cycloconverters mentioned before, a three-phase matrix converter can also be used in the rotor side of DFIG. In this system, stator of the wind turbine driven generator is directly connected to the grid while the rotor is connected via slip-rings to the output of a matrix converter. Modeling of the energy conversion system considers super-synchronous and sub-synchronous operating conditions which are achieved by means of the matrix converter. In order to decouple the active and reactive power, stator field oriented control is applied. Speed mode control is adopted for maximum wind energy extraction, provided that the wind speed and pitch angle of the turbine are known for each sampling period. Reactive power control is performed so that the stator reactive power is kept to zero. Promising simulation results demonstrating the control performance of the wind energy conversion system are presented.


Professor Sedat Sünter studied at The University of Firat, Turkey and received a B.Sc. (First Class) in Electrical Engineering in 1986 and subsequently MSc in 1989. From 1988 to 1991 he worked as a Research Assistant at The University of Firat involved in teaching and research in power electronic systems. He received a scholarship from Turkish Government for PhD study abroad in 1991. Consequently, He was accepted by The University of Nottingham, UK and received his PhD in Electrical and Electronic Engineering in the area of power electronic systems in 1995.
Since 1995 he has been a Lecturer in Power Electronics at the University of Firat, Turkey. He has been promoted to Associate Professor in 2000 and received full Professor of Power Electronics at Firat University in July 2006. He has been in UK as visiting professor for three months in 2013. In literature, an algorithm on Matrix Converters has been referred to his name as “Sunter-Clare Algorithm”.
He was vice Dean of the Faculty of Engineering in Firat University between 2004 and 2007. Since 2014, Professor Sünter is Head of The International Office in Firat University. He is also Institutional Coordinator of Erasmus+ Program.
His research interests are: Power electronic converters and modulation strategies, matrix converters, resonant converters, variable speed drive systems, renewable and energy.
Professor Sünter has a number of papers published in various journals and conference proceedings.