Заседание на УС на СЕЕС, 16 · verka alexieva - lem bulgaria ivan mihaylov -...

XI NATIONAL CONFERENCE

WITH INTERNATIONAL PARTICIPATION

ELECTRONICA 2020

PROGRAMМЕ

23 – 24 July 2020

Sofia

National Science and Technical Centre

108 Rakovski Str.

&

Virtual rooms

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XI NATIONAL CONFERENCE WITH INTERNATIONAL

PARTICIPATION “ELECTRONICA 2020”

Organized by:

The Union of Electronics, Electrical Engineering and

Telecommunications (CEEC),

Technical University of Sofia (TU-Sofia),

IEEE Bulgarian Section,

and Faculty of Electronic Engineering and Technologies (FEET)

In cooperation with:

Federation of the Scientific and Technical Unions in Bulgaria (FNTS),

Bulgarian Academy of Sciences (BAS),

University of Applied Sciences - Offenburg,

Riga Technical University,

VDE – Germany and

Leading Electronics Companies.

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XI NATIONAL CONFERENCE WITH INTERNATIONAL

PARTICIPATION “ELECTRONICA 2020”

Honorary chairmen:

Ivan Kralov – TU - Sofia

Ivan Yatchev – FNTS and CEEC

Conference chairmen:

Ivo Iliev - TU Sofia

Seferin Mirtchev – СЕЕС

Georgi Mihov – BAS and TU - Sofia

Scientific Secretary:

Dimitar Arnaudov – TU - Sofia

Local Organizing Committee:

Nikolay Hinov – TU - Sofia

Emil Manolov – TU - Sofia

Oskars Krievs - RTU

Sanka Gateva - BAS

Georgi Stoyanov - IEEE Bul. Sec.

Anatolii Aleksandrov - TU - Gabrovo

Ilia G. Iliev - TU-Sofia

Dimitar Yudov – BFU - Burgas

Rossitza Goleva - IEEE Bul. Sec.

Radi Romanski – СЕЕС

Ivan Vassilev - CEEC

Rossen Radonov - ТУ - Sofia

Anna Andonova - TU - Sofia

Nikolay Madzharov - TU - Gabrovo

Petar Yakimov - TU - Sofia

George Angelov – TU - Sofia

Vencislav Valchev -TU -Varna

Sotir Sotirov - University "Prof. As. Zlatarov"

Bourgas

Krassimir Paskalev – Kostal SofiaSoft Bulgaria

Georgi Atanasov - Festo production

Sylvain Collot -Melexis Bulgaria

Verka Alexieva - LEM Bulgaria

Ivan Mihaylov - Visteon

Nikola Durchev - Balkantel

Nikolay Iliev – Next Lab

Krasimir Pingelov - Electron Progress

Program Committee:

Alden Dochshanov, Italy

Darius Andriukaitis, Lithuania

Davy Pissoort, Belgium

Dimitar Arnaudov, Bulgaria

George Angelov, Bulgaria

Gennady Zinoviev, Russia

Ivo Iliev, Bulgaria

Juraj Breza, Slovakia

Lykourgos Magafas, Greece

Leonids Ribickis, Latvia

Marin Marinov, Bulgaria

Marin Hristov, Bulgaria

Miglena Dontschewa, Austria

Sia Lozanova - BAS

Namyong Kim, Korea

Nicolae Muntean, Romania

Nikolay Hinov, Bulgaria

Octavian Cornea, Romania

Reinhard Bauer, Germany

Stefan Hensel, Germany

Stoyan Stoyanov, UK

Vladislav Skorpil, Czech Republic

Zenon Gotra, Ukraine

Tzeno Galchev, USA

Vassil Palankovski, Austria

Viera Stopjaková - Slovakia

Ritonja Jozef - Slovenia

Secretariat

Stefan Patchedjiev – СЕЕС

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XI NATIONAL CONFERENCE WITH INTERNATIONAL PARTICIPATION

“ELECTRONICA 2020”

Hour Event Discussion

Wednesday

22 July 15.00-18.00

Registration of participants & test

the system (Virtual room 1)

Webex software

10.00-10.30 Opening Session

Hall 3 & Virtual room 1

10.30-12.00 Scientific Session 1


Virtual room 2

Virtual room 3

12.00-12.30 Lunch break



Virtual room 2

Virtual room 3 Thursday 14.15-14.30 Coffee break

23 July 14.30-15.45 Invited papers


16.00-17.00

“University education in automotive

electronics and business needs".


17.00-18.00 „Alumni meeting”

Informal discussion


Friday

24 July

09.00 -10.15

Scientific Session 3


Virtual room 2

Virtual room 3

10.15 -10.30 Coffee break

10.30 -12.00 Scientific Session 4


Virtual room 2

Virtual room 3

12.00 -12.30 Lunch break



Virtual room 2

Virtual room 3

14.00 -14.30 Invited papers


14.45 -16.00 Scientific Session 6


Virtual room 2

Virtual room 3

16.00 -16.15 Coffee break

16.15 -17.30



Virtual room 2

Virtual room 3

17:30 Closing Session


https://e-university.tu-sofia.bg/e-conf/?konf=28

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Opening Session 10.00 - 10.30.

Hall 3 & Virtual room 1, Thursday 23 July 2020

Scientific Sessions 1, 2 10.30 -14.15


Invited papers 14.30 – 15.45


Design of Virtual Calibrator for Teaching Metrology in Higher Education Zivko KOKOLANSKI and Petar VIDOEVSKI - “Ss Cyrilu and Methodius”

University in Skopje

Е-mobility: looking into the technology "under the cover"

Krasimir PASKALEV and Zlatko Zlatkov- KOSTAL SofiaSoft Bulgaria

Discussion 16.00 -17.00

Hall 3 & Virtual room 1, Thursday 23 July 2020 "University education in automotive electronics and business needs".

Alumni meeting, Career forum

Virtual rooms

Scientific Sessions 3, 4, 5 9.00-14.00

Hall 3 & Virtual room 1, Friday 24 July 2020

Invited papers 14.00 - 14.30


WBG semiconductors, interleaving and integration of magnetics for non-isolated

DC-DC converter performance improvement Kaspars KROICS - Riga Technical University

Scientific Sessions 6, 7 14.45-17.00


Closing Session 17.30

https://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44chttps://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44c

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Information and Communication Technologies

Hall 3 & Virtual room 1, Thursday 23 July, 10.30 - 12.00

Chairpersons: Seferin MIRTCHEV, Stefan PATCHEDJIEV

1.1. MACHINE LEARNING APPROACH FOR MAGNETIC FIELD CALCULATIONS Valentin Mateev, Iliana Marinova

Abstract – Here is presented a machine learning approach for 2D steady-state and harmonic

magnetic field calculations based on Poisson and Helmholtz equations for Dirichlet boundary

problems. The approach is implemented on multilayer convolutional neural network trained over

the Compumag 1b T.E.A.M. benchmark problem variations dataset. Implementation is suitable for

non-homogeneous magnetic properties domains and distributed excitation sources. Results

accuracy is estimated in comparison with Finite Element Method model of the same problem.

1.2. OPTIMIZATION OF TORQUE AND POWER DENSITY FOR COAXIAL MAGNETIC GEARS

Valentin Mateev, Iliana Marinova

Abstract – In the present work, the recent positive trend in torque and power density of the

coaxial magnetic gears is discussed. Timeline of magnetic gears development according to design

topology and magnetic materials improvements is presented. Five generations of magnetic gears

are recognized according to the torque density limitations. Analysis of possible design and material

improvement opportunities is made. Main approach for torque and power density improvement is

the maximization of the air-gap surface in magnetic gear volume. For coaxial magnetic gears this is

possible by implementation of conical and multistage rotor designs. Theoretical limitations in case

of conical and multistage rotors usage are considered.

1.3. AN ORIGINAL AND SIMPLE METHOD FOR STUDYING THE PERFORMANCE OF A VoIP NETWORK

Ivan Nedyalkov

Abstract – In the present work, an easy and simple method for estimating the working capacity

of VoIP networks, using a protocol analyzer and mathematical distributions for the moments of

arrival of the packets, is proposed. The parameter that is monitored through the protocol analyzer

is the jitter. The mathematical distribution and approximations give an additional idea of the time

delay in the observed network. A virtual network is created to verify the proposed method.

Simulation studies are carried out to test the proposed method. The results of using the method are

presented.

1.4. PROGRAMMABILITY OF CHARGING FUNCTIONALITY AT THE NETWORK EDGE

Evelina Pencheva, Ivaylo Atanasov, Aleksandar Nametkov

Abstract – Programmability is a key characteristic of next generation networks. It enables open

access to network functions for external applications. In this paper, an approach to open access to

charging functions at the network edge is proposed. The approach is based on Multi-access Edge

Computing (MEC) technology which distributes cloud capabilities in the vicinity of end users. The

co-location of MEC with distributed core functions makes it possible to open the network interfaces

for advanced applications. The paper presents a new MEC service which enables applications to

charge the end users by amount or volume. The service design follows the Representational State

Transfer architectural style. The service resources and supported methods are described, and the

https://technicaluniversityofsofia.my.webex.com/technicaluniversityofsofia.my/j.php?MTID=m0d1373f89e2b6f20f228d4a1c6bfa44c

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service feasibility is illustrated by modeling the charging status as seen from the network and

application points of view.

1.5. TOWARD NETWORK INTELLECTUALIZATION IN 6G Evelina Pencheva, Ivaylo Atanasov, and Ivaylo Asenov

Abstract – After the first deployments of fifth generation (5G) networks, research on 6G system

has begun. The paper summarizes the characteristics of future 6G services and applications,

presents an overview of enabling technologies and focuses on the role of artificial intelligence

in improving end user quality of experience and in network optimization.

1.6. AN APPROACH FOR SECURING MQTT PROTOCOL IN ESP8266 WIFI MODULE

Iordan Stoev, Snezhinka Zaharieva, Adriana Borodzhieva, Gergana Staevska

Abstract – The paper presents an approach fo communication between ESP8266 modules

based on MQTT protocol using simple non-secure class for implementing the WiFi protocol.

Encryption based on Advanced Encryption Standard – 256-bit symmetric encryption algorithm was

implemented in order to achieve simple secure communication. In addition, a pseudorandom

generator was used to introduce asymmetry of the cypher data transmitted through the protocol.

1.7. COMPARATIVE ANALYSIS OVER DIFFERENT DEGREE OF JPEG COMPRESSION USED IN CBIR SYSTEMS

Miroslav Marinov

Abstract – Content-bases image retrieval systems (CBIR) use computer vision methods for

organizing, analyzing, processing and searching of million graphic files uploaded in the internet

daily. For that reason, the retrieval process is a key element in CBIR applications. The best system

performance is based on accurate and complete search which must be finished in reasonable

amount of time. It is straightly related to extracting, storing, and indexing of all necessary metadata

from the examined image set.

This paper gives information about JPEG compression and how it is used in some of the most

widespread CBIR systems. It reveals how different degree of that compression influences the

generated results from custom developed CBIR application. Furthermore, it shows the various of

similarity between same image set but examined in two different ways – with non-compressed and

compressed data retrieved by the system. At the end, the conclusions are made based on generated

results from developed and tested CBIR application which was made for these purposes.

1.8. DEVELOPMENT OF ULTRA-LOW POWER SENSOR NODE USING FRAM AND NANO TIMER

Dimitar Tokmakov, Stanislav Asenov

Abstract – In this paper we presents a project of ultra-low power sensor node for IoT

applications with LoRaWAN interface, successfully designed and tested. The main features of this

design is its ultra-low power consumption of sensor node in sleep mode, long distance

communication and secure data transmission. By using external nano timer TPL5110 and FRAM

(Ferroelectric Random Access Memory), it is possible to reduce the sensor node sleep mode

consumption current Ic to only 45nA. This increases battery life and sensor node autonomous

operation for several years.

1.9. INFORMATION TECHNOLOGY SUPPORT FOR PORTFOLIO OPTIMIZATION Todor Stoilov, Krasimira Stoilova

Abstract – The paper describes an application of information technology to support decision-

making for portfolio optimal investment. The decision making task is formalized as a portfolio

optimization problem solved in Excel environment, which gives practical tool for implementation

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for the decision-making. The portfolio optimization applies maximization of Net Present Value,

because the riskless return is close to zero. The derived information technology solution is

numerically tested with mutual funds, traded on the Bulgarian Stock Exchange for 2019.

1.10. PROBLEMS WITH ANTENNA RADOME BEHAVIOUR AT LOW ELEVATION DIRECTIONS

Plamen Dankov, Yavor Zhelev, Ivaylo Slavkov

Abstract - The paper discusses some practical problems appearing at very low elevation

directions in electronically steerable antennas for wireless communication, caused by the used

multilayer antenna radome. The experimental and numerical results show how the polarization of

the received/ transmitted signals changes through the radome at big incident angles ~60-80 deg.

The measured anisotropy of different radome materials and layers confirms the origin of the

observed effects. Finally, useful conclusions are presented.

1.11. THE IMPACT OF MACHINE VISION IN ADDITIVE MANUFACTURING Roumiana Ilieva, Mario Nikolov

Abstract - Digital manufacturing (DM) is a key strategy that plays strategies in planning

toward the knowledge-based manufacturing. Combining 3D machine vision (3D-MV) and an

Additive Manufacturing (AM) is one of the innovative approaches in manufacturing. Cutting-edge

systems will enable 3-D printing machine users to accurately test and qualify printed parts for any

number of applications, including aerospace and medical devices.

1.12. IT SERVICE MANAGEMENT FRAMEWORK TO IMPROVE BUSINESS INFORMATION STRUCTURE

Roumiana Ilieva, Yoto Nikolov

Abstract - The objective of our study is to come to an understanding on the benefits provided by

the implementation of IT service management Framework in business IT structure. One of the most

commonly used by hundreds of organizations framework for IT service management is ITIL. ITIL is

not a standard that has to be followed, it is more like a guidance that should be read and

understood and used to create value for the service provider and its customers. Business is advised

to adopt ITIL best practice and to adopt them to work with their specific environments to meet their

needs. Here we will compare challenges and benefits of companies at various levels of

implementing IT service management frameworks, also looks at the number of implemented

processes at the various levels. Where the results indicate that as the maturity of implementation

increases, the perception of challenges decreases.


Circuits and Systems

Hall 3 & Virtual room 1, Thursday 23 July, 12.30 - 14.15

Chairpersons: Ivo ILIEV, Georgi NIKOLOV

2.1. AN ADAPTIVE CONTROL SCHEME FOR HUMAN FOLLOWING BEHAVIOR OF MOBILE ROBOTS

Plamen Petrov, Veska Georgieva, Ivan Kralov, Stilyan Nikolov

Abstract – In this paper, we present an adaptive mobile robot control scheme for autonomous

human following, such that the robot keeps a desired distance from the person. A human-robot


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interaction model in error coordinates suitable for robot following applications is proposed. An

adaptive control low is presented to tackle with the problem of the unknown human velocity.

Simulation and experimental results are presented to illustrate the effectiveness of the proposed

control scheme.

2.2. METHODOLOGY FOR FREQUENCY OF POWER-LINE INTERFERENCES MEASURING

Georgy Mihov, Dimiter Badarov

Abstract – A test procedure for mains interference frequency measuring is represented in the

work. The procedure is based on measurement the transfer coefficient of an averaging digital filter

applied to the interference signal. The procedure is implemented in MatLab environment. It

includes filters for elimination the mains interference extracting, for suppression the third harmonic

and for measuring the power-line interference frequency. Appropriate experiments has been

investigated.

2.3. MODELING THE ELECTRICAL PARAMETERS OF A MULTI-STAGE THERMOELECTRIC MODULE BY NEURAL NETWORK

Todor Petkov, Ivaylo Belovski, Kaloyan Ivanov and Anatoliy Aleksandrov

Abstract – This work presents the results of modeling the electrical parameters - current I and

voltage E of a multi-stage Peltier module working in generator mode using a neural network. A

preliminary experiment was performed to accurately determine the current and voltage generated,

depending on the applied temperature difference ΔT and load resistance R. The values obtained

were used to train the neural network.

2.4. OPTIMIZATION OF SYSTEM DEVELOPMENT PROCESS FOR ELECTRONIC DEVICES IN THE AUTOMOTIVE INDUSTRY

Dimitar Vrachkov and Dimitar Todorov

Abstract – The main object of the current research will be the optimization of the system

development process for electronic devices in the automotive industry. The material is based on the

main mechanisms for electronic development from the international SPICE standard. We will take a

look over three main problems in the automotive industry today and we will try to provide good

solution to all of them. First topic is more or less overview of the current situation with the

documentation in the automotive - what are the specifics of designing electronic devices for the

automotive industry? Also, we will provide solution for monitoring of the results related to specific

system requirements. At the end, we will try to define optimization strategy for the development

process – without losing traceability and without losing project quality.

2.5. ACTIVE RC LPFS WITH SINGLE-ELEMENT POLE FREQUENCY TUNING

Darya Denisenko, Nikolay Prokopenko, Nikolay Butyrlagin

Abstract – New low-pass filter (LPF) architectures based on differential difference

operational amplifiers (DDOA) are considered. The feature of the proposed LPF is that when

tuning the cut-off frequency, the LPF gain remains unchanged at zero frequency. As a tuning

element, it is possible to use digital potentiometers. The basic equations for two LPF modifications

are presented, which provide parametric synthesis of circuits are discussed. In Micro-cap CAD was

given the results of computer simulation of tunable responses.

2.6. DESIGN FEATURES OF THE SECOND-ORDER ACTIVE BAND-PASS FILTERS WITH INDEPENDENT ADJUSTMENT OF CRITICAL PARAMETERS

Darya Denisenko, Nikolay Prokopenko, Evgeniy Butovka

Abstract – Currently, it is urgent to develop a new generation of active RC filters, which

allow independent tuning of the critical parameters. This makes it easier to build new devices. The

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article first time considers the generalized architecture of new population of the active RC band-

pass filters (ARCFs) in which the independent adjustment of the critical parameters in the pass

band is possible. As an example the equations for the transfer functions and their coefficients for

two new ARCF modifications are given, which allow for the parametric synthesis of the definite

design solutions. The results of modeling in the Micro-CAP program are discussed, confirming the

advantages of the ARCF of the considered family.

2.7.

2.8. DEVELOPMENT AND IMPLEMENTATION OF A DEMONSTRATION MODEL OF SMART PARKING WITH LORA-BASED COMMUNICATION

MODULE

Krasen Angelov,

Abstract– The main purpose of this work is to present the development and implementation of

a demonstration model of smart parking system that uses energy efficient LoRa-based transmission

module, autonomous power supply and the ability for integration into a scalable smart platform for

intelligent provision, monitoring, visualization and management of parking services in large cities

with complex urban environment.

2.9. A COMPARATIVE STUDY OF ENERGY STORAGE SYSTEMS FOR ENERGY HARVESTING DEVICES –

Dimitar Nikolov

Abstract – This paper, presents a model to predict the energy output from reverse

electrowetting energy harvesting system with use of cost-effective materials. Reverse electrowetting

on dielectric allows energy to be harvested from spontaneous aperiodic mechanical movements,

where conventional energy harvesting approaches are not suitable for due to low energy

conversion efficiency and frequency .

2.10. INNOVATIVE TEACHING ON PHOTOVOLTAIC GENERATION Alessandro Ciocia, Paolo Di Leo, Gabriele Malgaroli, Angela Russo, Filippo

Spertino, and Slavka Tzanova

Abstract – One of the most important technologies for the renewable energy production is the

Photovoltaic (PV) one. In the last decades, the enormous growth in the world of Photovoltaic

installation capacity, and future trends, makes the knowledge of this topic fundamental for

engineers working in the energy field with this competence, and not only. Thus, for students

enrolled in industrial engineering courses, appropriate and innovative teaching methods are

necessary. This paper aims to describe the structure of the course “Photovoltaic Power

Generation” in which solar resource and the photovoltaic generators, including power electronics,

are explained. The topics of traditional theoretical lectures are presented, with the links to practical

exercises and laboratories.

2.11. A COMPARATIVE ANALYSIS OF VARIOUS FILTERS FOR NOISE REDUCTION IN CARDIAC ULTRASOUND IMAGES

Veska Georgieva and Anna Grozeva

Abstract – The cardiac ultrasound (US) images are used to obtain qualitative information on

the outline of the organ and type of tissue, as well as quantitative information on the thickness and

movement of the internal walls and layers of the heart. Speckle noise generally masks the fine

details of the US image and makes its interpretation difficult for medical diagnosis. This paper

presents various filters for noise reduction in cardiac US images, which have been discussed and

compared.

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2.12. BODY SENSOR NETWORK FOR REMOTE MONITORING OF PATIENTS' CARDIAC STATUS

Evgeniya Gospodinova, Mitko Gospodinov, Galya Georgieva-Tsaneva, Krasimir

Cheshmedzhiev

Abstract – The article presents a wearable medical electronic system - body sensors network

(BSN), intended for real-time monitoring of physiological parameters of the patients. BSN is

compact platform for sensory registration of cardio rhythm, body temperature, etc. The sensors are

miniature devices for detection of physiological parameters. The transmitted information is stored

in real-time in a wearable “hub” communicating wirelessly with computerized equipment. The

information obtained can be used for individual monitoring of health status, disease warnings and

feedback.


Industrial and Power Electronics

Hall 3 & Virtual room 1, Friday 24 July, 9.00 - 10.15

Chairpersons: Nikolay HINOV, Dimitar ARNAUDOV

3.1. COMPARISON OF CONTROL METHODS FOR BIDIRECTIONAL DC/DC CONVERTERS

Vladimir Dimitrov and Nikolay Hinov

Abstract – This paper considers the use of ripple and compensator based control circuits in

bidirectional dc/dc converters. Typical review of ripple based controllers includes their application

in unidirectional controllers. Their advantages in terms of better transient response, simple

realization and in some cases better efficacy at lighter loads are widely considered. Such a

comparison must be made in the specific case when the application requires bidirectional and more

importantly multiphase operation. This paper investigates by comparing three cases of a control

system- standard compensator based, a constant frequency valley ripple based controller and an

enhanced version including better regulation. These are compared for different voltage sources at

their outputs in term of their regulation and dynamics.

3.2. MATHEMATICAL MODELING AND SIMULATIONS OF DC/DC CONVERTER IN PSIM ENVIRONMENT

Gergana Vacheva and Nikolay Hinov

Abstract – In the current paper mathematical modeling and simulation of DC/DC converter

for educational purposes are presented. It is reviewed the main possibilities of modeling in PSIM

environment. The main libraries and tools are described. The mathematical model of buck

converter with variation of the values of the inductor and the capacitor are presented.

3.3. AREA MEASURING WITH PC CAMERA Petar Panaiotov, Goran Goranov and Valentina Rankovska

Abstract – Area measurement and registration in different areas of the industry are done by

different methods. One example is the production of leather. The opposite shape, different thickness,

and color of the leather make this task a challenge. In the leather industry, a measurement method

using photosensors and a video camera method have been successfully implemented. This article

presents the development of software that measures the area of leather with a USB camera. Such a

system is implemented but it is necessary to manually set the measurement mode. It works by the


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method of dark and light spots and so dark (black) or light (white) skins are measured. The

proposed new software is based on automatic color recognition against a green background.

3.4. USING MARKOV’S CHAINS FOR RELIABILITY MODELING OF ENERGY STORAGE DEVICES

Prodan Prodanov and Dobroslav Dankov

Abstract – The reliability of energy storage devices can be defined by using the State Analysis

Method. For any given system, a Markov model consists of a list of the possible states of that

system, the possible transition paths between those states, and the rate parameters of those

transitions. Those states could be reduced to: operability, failure, protection, availability and

redundancy. To do that type of analysis, Markov Analysis is used, which allows the design of

reliability analysis models that could be used for enhancing the reliability of energy storage

devices.

3.5. RELIABILITY ESTIMATION OF MOSFET TRANSISTORS IN DEPENDENCY OF THERMAL RESISTANCE OF COOLING SYSTEM

Prodan Prodanov

Abstract – MOSFET transistors are elements that appear one of the most widely used types in

industrial electronics. Their reliability assessment is linked to a number of analyses related to the

circuits they are used in, the operating electrical and thermal modes, and the operating conditions.

The present paper studies the impact of the cooling sink in water cooling systems used for cooling

MOSFET transistors in industrial energy conversion systems.

3.6. A STUDY OF THE BOUNDARY MODES OF AN LLC DC/DC CONVERTER OPERATING ABOVE RESONANT FREQUENCY

Aleksandar Vuchev , Tsvetana Grigorova

Abstract – The paper presents the results from investigations of the performance of an LLC

resonant DC/DC converter operating above resonant frequency, including boundary modes (no-

load and short circuit) using the state-plane techniques. Comparative data from calculated and

simulated results are presented.

3.7. Analysis and Investigation of an Asymmetric Bridge Converter for a Three-Phase 12/8 SRM in Generating Mode

Dimitar Yankov , Tsvetana Grigorova

Abstract – The paper presents an analytical and simulation study of an asymmetric bridge

converter fed 12/8 three-phase SRM in generating mode. The main purpose of the investigations is

to clarify the conditions for achieving the maximum energy recovery. It is shown that the amount of

energy returned from the SRM to the battery depends mainly on the excitation and generation

intervals, the PWM dutycycle, the matching of the internal battery resistance and the position-

dependent SRM equivalent resistance. The obtained analytical results in MATLAB/Simulink are

verified.

3.8. COMBINED FOOTPRINT WITH JET PRINTING AND SOLDERING IN THE VAPOR PHASE

Valentin Tsenev, Valentin Videkov

Abstract – The paper presents obtaining a combined footprint [1, 2] of two or more solder

pastes [3, 4] using a jet printer [5]. When using the Pin in Paste (PiP) technology [6] with over

printing [7], two problems arise - obtaining solder balls outside the solder pads [8] and not

everywhere melting of the solder paste. To avoid these problems, a combined footprint of two solder

pastes could be used, which can reduce the melting temperature and collect the solder material in

the pad. Combined footprints were realized by means of a Jet printer on different pads with

13

different content of the two solder pastes. Using the reflow process [9] in the vapor phase [10], the

soldering was performed. It was studied and evaluated how the solder material melted in different

sized pads and at different contents of the two solder pastes. The soldering of SMD [11] and TH

[12] elements was also observed and evaluated using a combined fingerprint.

3.9. A Methodology for Analysis of Thermal Transfer by Xray Study Valentin Tsenev

Abstract - The paper presents a methodology for analyzing thermal transfer using Xray

study[1]. The essence of the methodology lies in a detailed analytical survey of the entire thermal

transfer system of a SMD[2] mounted powerful LED by 3D Xray[3] examination of all thermal

transitions. The thermal transfer in the mechanical system of the mounted LED[4] to a printed plate

with a thick aluminum base is described in detail. In the present study, the influence of the quality of

the solder[5] on the thermal transfer at the generated temperature from the LED crystal to the

aluminum substrate was taken into account, and the influence of the voids[6] content was analyzed.

The influence of other thermal transitions is also considered. The results are presented and

conclusions are drawn as to the causes and location of the faulty heat transfer and the

corresponding overheating of the mounted LED. A solution based on the analysis was also

proposed, which after its implementation has proved the accuracy of the analysis.


Industrial and Power Electronics

Hall 3 & Virtual room 1, Friday 24 July, 10. 30 - 12.00

Chairpersons: Nikolay HINOV, Dimitar ARNAUDOV

4.1. MODELLING OF INDUCTIVE POWER TRANSFER SYSTEM Dobroslav Dankov, Prodan Prodanov

Abstract – The simulation of IPT converters is linked to the use of an appropriate model of

the system transmitter and receiver coils. Three different simulation models are proposed

depending on the equivalent circuit used. The models have been verified with respect to an existing

IPT system by using LTSPICE. The models have been compared as regards their accuracy and

response time by contrasting the simulation and experimental data.

4.2. APPLYING AN AGING MODELS FOR RELIABILITY ESTIMATION OF SUPERCAPACITORS

Prodan Prodanov, Dobroslav Dankov

Abstract – Supercapacitors can be viewed as energy storage devices. As every component in

electronic circuitry, they can cause failures in electronic equipment and therefore are subject of

reliability study. The main factors influencing supercapacitor reliability are operating temperature,

operating voltage and equivalent series resistance (ESR). Those three performance parameters of

supercapacitors should be embedded in the model for calculating parameters such as failure rates,

mean time to failure and reliability.

4.3. BIDIRECTIONAL SERIES RESONANT DC-DC CONVERTER PERFORMANCE IMPROVEMENT

Angel Lichev, Aleksandar Vuchev

Abstract – Experimental research has been made on a bidirectional series resonant DC-DC

converter, operating at a frequency higher than the resonant one. The control of the conducted

energy is done via both phase shifting and operating frequency variation, simultaneously. In such a

way, a linearization of the converter control characteristic is achieved. The research data has then


14

been compared to a solely phase shift control method. Better production efficiency of the convertеr

is an additional asset.

4.4. A REVIEW OF SUPERCAPACITORS AS NEW POWER SOURCES IN HYBRID ENERGY STORAGE SYSTEMS FOR ELECTRIC VEHICLES

Miroslav Andreev

Abstract – Supercapacitors are widely spread nowadays. They are known as ultracapacitors

or electrochemical double layer capacitors i.e., EDLC which are energy storage devices which can

provide high energy specified and efficiency. They are based on a nanotube technology. Their

principal characteristics make them suitable for usage in energy storage systems and the possibility

to be charged/discharged rapidly without loss of efficiency for a lot of cycles, much higher than

electrochemical batteries and also release a huge amount of energy power. Compared to Li-ion

batteries, the supercapacitors have lower power density that’s why they cannot compete with

lithium batteries in terms of energy content - cost for Watt per hour, but they can really compete to

cost per kilowatt and cost per unit and their capacity. Nowadays almost all of pure electric vehicles

are equipped with electrochemical batteries which have a lower energy density compared to a

petrol fuel used in vehicles with combustion engines. The supercapacitor pack can be successfully

used in HESS (battery-supercapacitor system) combining different energy storage technologies with

special control strategy using all the advantages of each energy source for improving and reaching

overall performance. This article summarizes the performance of supercapactiros in terms of

energy density, equivalent series resistance and their optimal usage in the automotive sector. This

paper will introduce, concern, review and provide the main types of supercapacitors, their structure

and their usage in applications for electric vehicles and also state of the art of materials. The paper

also presents a brief review of benefits, features, advantages and disadvantages of hybrid energy

systems based on batteries and supercapacitors.

4.5. RESONANT CONVERTERS FOR LOW POWER WIRELESS ENERGY TRANSFER

Vladimir Dimitrov, Nikolay Nehovski, Nikolay Hinov

Abstract – The papers reviews low power wireless power transfer. Typical applications

involve wireless charging of mobile phones and laptops (under 100W). A typical series resonant

circuit is shown along the required formulas to size the power circuit. A simulation showing the

influence of magnetic coupling and control frequency on the output resonant capacitors voltage is

shown.

4.6. ABILITY TO CONTROL THE TEMPERATURE PROFILE OF SOLDERING USING LOCAL HEAT SCREENS

Valentin Videkov, Valentin Tsenev

Abstract – The present paper presents the results of the study of a method of soldering using

heat shields. The essence of the method consists in placing additional metal screens on the soldered

SMD elements, which change the effective heat mass. Changing the effective mass allows for slower

heating of sensitive elements. In the present study, attention is paid to the influence of the thickness

of the printed circuit board on the change of the temperature profile under the screen. The influence

of the additional heat mass in the screen on the moment of the change of the heat profile is also

considered. In addition to the amount of material added to the screen, the temperature of its phase

conversion also has an effect. The results of using a reflow process with infrared heating are

presented.

4.7. THYRISTOR MODULES FOR ELECTRONIC CONVERTERS INTENDED FOR INCREASED VOLTAGE

Kostadin Milanov

15

Abstract – This article describes the design specifics of the control and the voltage

distribution of series connected thyristors and the construction features of integrating into a

medium-voltage power converter. The paper shows the feasibility of the solutions and their

implementation in the designing of a three-phase rectifier working at increased voltage. The results,

construction and implementation of thyristor modules made with series-connected thyristors were

commissioned into a rectifier type BELA HV-6500 / 30A manufactured by R&D center at TU-Sofia,

Scientific Applied Laboratory for Contactless Electrical Appliances "BELA".

4.8. APPROBATION OF A MATHEMATICAL MODEL OF A SPECIALIZED MECHATRONIC SYSTEM

Martin Kambushev, Nayden Chivarov, Assen Marinov, Reneta Dimitrova

Abstract – The article discusses a procedure for studying the adequacy of a nonlinear non-

stationary aerodynamic model. The possibility for balancing and the stability of the balanced model

in the altitude-speed range of operation of the real aircraft has been studied. The purpose of the

report is to determine the range of altitudes and flight speeds in which the behavior of the object

and the model coincide.

4.9. CONTROL OF IMPULSE CONVERTER WITH REVERSE ENERGY TRANSMISSION WITH ACTIVE DRIVER CIRCUIT

Yanka Ivanova, Svetoslav Ivanov, Evgenia Vasileva, Dimitar Nyagolov

Abstract – This article presents the research of an active driver circuit with dv/dt feedback,

included in the control system of a converter with reverse power transmission. A comparative

analysis of the transients in the power circuit when controlling the power transistor with

conventional and active driver is made. The influence of the active driver circuit on the frequency

and attenuation of the resonant processes during the switching of the power transistor has been

researched. Conclusions are made about the power losses, the amplitude values of the voltages and

the electromagnetic radiation of the converter.

4.10. COMPARISON OF AN ACTIVE VOLTAGE BALANCING METODS FOR SUPERCAPACITORS

Krasimir Kishkin,

Abstract – This paper presents a fast charging algorithm for battery bank made of connected in

series supercapacitor cells. This algorithm allows simultaneously charging of all sells up to

preliminary set up maximum voltage. Considering the tolerance in the capacitance of each cell and

that, they are connected in series, we know that when the charging current is equal for all cells, the

voltage across each cells will increase with different rate. In the presented algorithm, the charging

current for each cell is different. The voltages across cells increase simultaneously. This method is

compared to the method that the equalization has higher currents in a short time.

4.11. COMPARISON OF A MULTIPHASE TOPOLOGY FOR CHARGING ENERGY STORAGE ELEMENTS

Dimitar Arnaudov,

16

Abstract – The paper presents a study of a multiphase converter for charging stations for electric

vehicles. The converter consists of parallel operating units based on high-frequency resonant

inverters. Simulation models of multiphase converters have been developed. Simulation studies

have been conducted to demonstrate the advantages and disadvantages of these systems. The

impact of the asymmetry of the individual units on the pulsations of the charging current is

investigated, as well as the possibilities for regulating the value of the charging current by

changing the parameters of one or several units. The advantages of a five-phase converter over six-

phase one at the same power output are shown.


Instrumentation and Measurement


Chairpersons: Marin MARINOV, Zhivko KOKOLANSKI

5.1. DYNAMIC ERROR APPRAISAL OF THE PRIMARY TRANSDUCER IN THE SENSOR STRUCTURE OF THE PHYSICAL QUANTITY –

Leonty Samoilov, Darya Denisenko, Nikolay Prokopenko

Abstract – In many cases, the primary transducer (PT) of a physical quantity sensor converts

(normalizes) a variable physical quantity into an electrical signal. The dynamic error of the PT is

determined by the delay time in the PT and the first derivative of the signal. In this article, the

amplitude-frequency response (AFR), of the PT was approximated by the frequency response of the

Butterworth filter. The use of application programs made it possible to obtain numerical estimates

of the delay time in the PT. For the case of the unlimited spectrum under consideration, the first

derivative of the PT signal does not differ from the value obtained using the Bernstein inequality.

The final calculations showed a significant effect of the dynamic error on the total error of the PT.

5.2. DETECTION OF DIFFERENT BEARING FAULTS IN A PERMANENT MAGNET SYNCHRONOUS MOTOR USING PWT AND LVQNN

Hamed Ahani and Vahid Izadi

Abstract – This paper deals with the detection of bearing-related faults in permanent magnet

synchronous motors. First, the motor current was sampled and analyzed using multi-level packet

waveform transformation and then based on different features from the transformed signals, which

resulting from the primary waveform, the LVQ neural network is trained for doing the

classification. The outer-ring, inner-ring, cage, lubricant loss, and imperfect ball fault classes are

considered in this paper. The proposed approach for fault detection shows high accuracy for

practical cases.

5.3. STUDY OF THE AUDIO CHARACTERISTICS OF MOBILE PHONES IN THE CONTEXT OF TRANSMISSION OF BIOMEDICAL SIGNALS CONVERTED

INTO SOUND

Ivo Iliev, Borislav Ganev, Ivan Kanev

Abstract – The remote patient monitoring system has become a research hotspot in recent

years. Using ICT and some wearable technology, it is possible to monitor the user’s health

condition in real-time. At the same time, the development of communication technologies with

higher density of the communication channels is associated with increasingly occurring collisions.

One simple approach using mobile phone (GSM) for patient’s data transmission of audio


17

transformed biological signals is discussed in this paper. The results of performed experimental

laboratory tests for determining the acoustic characteristics of GSM devices are presented.

5.4.

5.5. PERFORMANCE EVALUATION OF MEMS PRESSURE SENSORS Borislav Ganev, Dimitar Nikolov , Marin Marinov

Abstract – Atmospheric pressure sensors are important for a number of applications,

including indoor positioning, environmental monitoring and more. This article presents a study of

the main characteristics of micromechanical atmospheric sensors. Four different models of

micromechanical pressure sensors were studied. Some of the models measure along with the

pressure additional parameters, such as temperature, relative humidity and air quality. The

research evaluated the accuracy of the sensors, the influence of the change of basic atmospheric

parameters on it and their noise characteristics. The results show that low-budget micromechanical

pressure sensors offer a number of advantages for efficient implementation of a number of

applications. An important prerequisite for this is the use of appropriate algorithms for fusion of

sensor data, which can increase the reliability of their data.

5.6. CHARACTERIZATION OF DIELECTRIC ANISOTROPY OF REINFORCED SUBSTRATES AT DIFFERENT TEMPERATURES

Plamen Dankov, Valda Levcheva and Mario Iliev

Abstract – The paper considers the temperature behavior of dielectric parameters (dielectric

constant and dielectric loss tangent) of reinforced substrates used in the microwave electronics at

different temperatures. A method has been developed for the determination of the temperature

dependencies of substrate uni-axial anisotropy (different dielectric parameters at different

directions – parallel and perpendicular to the substrate surface). Such information for the

temperature changes of the uniaxial anisotropy of several reinforced substrates has been presented

for the first time.

5.7. THE IMPACT OF THE SYNCHRONIZATION BETWEEN INFRARED CAMERA AND EXCITATION SOURCE ON DEFECTS DETECTION QUALITY

IN LOCK-IN THERMOGRAPHY MEASUREMENTS

Borislav Bonev

Abstract – The aim of this article is to consider the influence of the synchronization between

the excitation source and the thermographic camera on the post-processing results (amplitude and

phase contrast) in lock-in thermography. A simulation study of one-dimensional thermographic

signal models was performed. An electronic module has been developed, allowing changing the

phase of the frame capturing signal. The study was performed using a prepared experimental

specimen. The results for a different phase of the frame capturing signal are presented.

5.8. COMPUTATION OF GEOMETRIC CHARACTERISTICS FROM THERMAL IMAGES OF CORRODED SURFACE OBJECT

Borislav Bonev, Anna Stoynova and Antonio Shopov

Abstract – The increase in temperature in the structural elements can be due to various

factors. Due to the physical nonlinearity of the building materials, it is not possible to perform a

separate analysis for the stress or deformation, which are directly dependent on the changes in the

geometric characteristics. A method for automatic calculation of the geometric characteristics of

corroded objects using an infrared thermography is presented. The results obtained using this

method are verified and analyzed.

5.9. SIMULATION MODELS DEVELOPMENT FOR BATTERY PARAMETERS ESTIMATION

18

Evgeni Malev, Toncho Hristov Papanchev

Abstract – The paper presents an overview of systems which analyze the behavior at the

processes charge and discharge of a battery. A physical and two mathematical systems have been

developed to provide information about the basic and secondary battery parameters. The data can

be stored in an array and from there can determined SOC,SOH, trouble-free operation and other

parameters.

5.10. SERVICE PROTOTYPING BASED ON DIGITAL TWINS FOR VIRTUAL COMMISSIONING SCENARIOS

Michael Grethler, Jivka Ovtcharova, Marin B. Marinov

Abstract – For the multidimensional prototyping of services in Product-Service-Systems a

procedure was developed and enriched with typical scenarios like the virtual commissioning of

machines and industrial plants. For the development, design dimensions, main development

aspects, and prototyping attributes were examined and condensed in a service prototyping matrix.

From this matrix, software and service products were prototypically derived for an IT vendor.

5.11. AN INDUSTRIAL IOT PLATFORM AND ITS APPLICATIONS BASED ON THE NEW GENERATION OF INFORMATION TECHNOLOGY

Jieyang Peng, Michael Grethler, Andreas Kimmig, Marin B. Marinov, Jivka Ovtcharova

Abstract – With the application of a new generation of information technology in the field of

manufacturing and the deep integration of computer technology and manufacturing, industrial

production is developing towards intellectualization and networking. Because the current

production system cannot fully mine the value of industrial data and the existence of information

islands in the production process, this paper introduces an industrial Internet of things (IoT)

platform based on 5G, OPC-UA, and other communication technologies. This paper first analyzes

the basic requirements of the industrial IoT, then introduces the architecture and detailed

information flow of this platform, and finally shows the application of this platform in the PHM

field. On the one hand, this paper shows the application of the industrial Internet of things platform,

on the other hand, it provides a reference for industrial data processing.


Micro and optoelectronics


Chairpersons: George ANGELOV, Rossen RADONOV

6.1. MODELING FOR THERMOGRAPHIC DETECTION OF SUBSURFACE DEFECTS ABOVE DIFFERENT THICKNESS –

Anna Stoynova

Abstract – The results of study the effect of object thickness on subsurface defects detection by

active thermofraphy are discussed. The results of an experiment to determine the effect of object

thickness on determination of the depth of the defect with active thermographic testing is presented.

A thermography simulation was conducted and experimental data were processed.

6.2. THERMAL DESIGN: BASIC STAGES, PROBLEMS AND SOLUTIONS Nikolay Vakrilov, Nadezhda Kafadarova

Abstract – This article discusses the stages in the development of a project in the field of

thermal design and how to reduce the possible risks in the initial stage of product development for


19

thermal engineers. An approach for evaluating the thermal efficiency of three test structures of

printed circuit boards through CFD modelling and simulations of heat transfer processes is

proposed. The thermal regime of a COB LED module with a cooling radiator designed for it is

predicted by CFD simulation. Experimental measurements with a prototype of the COB LED

module are performed, which show good compliance with the results in simulations.

6.3. NUMERICAL THERMAL ANALYSIS OF THE PCB CONSTRUCTION IMPACT

Nikolay Vakrilov, Diana Stoyanova and Nadezhda Kafadarova

Abstract – In this research computer modeling and thermal simulations based on CFD for

quantitative estimation of temperature and diagnostic of critical fields with higher risk of

malfunction in DC-DC converters is presented. The influence of structural and technological

factors on the board is evaluated in the thermal analyzes: the percentage of fillers, the thickness of

the inner copper layers. Thermal analyzes were performed at different ambient temperatures and

extreme heat loads.

6.4. COMSOL MODELING OF GEOMETRICAL INFLUENCE OF SONIC CRYSTAL NOISE BARRIER ATTENUATION

Elitsa Gieva and Ivelina Ruskova

Abstract – In the present article the influence of the change of different parameters of the

geometry of the Sonic Crystals noise barriers on the noise attenuation is described. Results with

different peculiarities of the geometry are compared. Sound crystals, arranged in a different

matrices were examined. The modeling is performed with the COMSOL program..

6.5. FABRICATION OF NANOCOMPOSITE BASED OF COPPER NANOWIRES AND SILICONЕ RUBBER

Tobiya Karagyozov, Boriana Tzaneva and Valentin Videkov,

Abstract –In this work the influence of the diluent amount and the method of introduction of

copper nanowires on silicone for preparation of nanocomposite material was investigated. Toluene

(T) added to fresh silicone liquid (S) in S:T proportions from 1:1 to 1:4 was used as a diluent. The

fragmentation of separate nanowires and their distribution in silicone matrix was examined by

optical microscopy. The optimal technological conditions for maximum dispersion and

homogeneous mixing have been established.

6.6. SILICON HALL-EFFECT MULTISENSOR Siya Lozanova and Chavdar Roumenin

Abstract – A novel in-plane sensitive Hall-effect multisensor is presented, in the active

transducer region of which, two Hall voltages are generated independently. This is achieved by the

original design and by the supply formed by two constant currents. The residual offset drift is about

140 times smaller than the drift of a single Hall device. The magnetosensitivity reaches

SRI≈170V/АТ. The signal-to-noise ratio is increased, the measured minimal magnetic induction is

Bmin≈9µT. The characteristics will have impact on quantum communication, and medicine.

6.7. EXTERNAL MAGNETIC FIELD INFLUENCE ON THE ELECTRICAL AND MICROWAVE PROPERTIES ON COMPOSITE MATERIALS,

COMPRISING MAGNETITE AND BARIUM AND STRONTIUM

HEXAFERRITES FILLERS

Kamelia Ruskova

Abstract – The influence of the constant magnetic field on the microwave and electrical

properties of elastomer-based (nitrile butadiene and chloroprene rubber) composites, comprising

magnetite and hard magnetic fillers – strontium and Ba- substituted hexaferrites was investigated.

20

It was established that the magnetic modification increases both the electrical conductivity and

electromagnetic wave absorption. The effect observed is due to presence of polar bonds into the

rubber matrix and is connected to the conductive phase of secondary particles structure formation

and structural homogeneity as a result of the external magnetic field impact.

6.8. STUDY ON THE INFLUENE OF THE EXTERNAL MAGNETIC FIELD ON THE PROPERTIES OF THE ELASTOMERIC COMPOSITES BASED ON

BARIUM AND STRONTIUM HEXAFERRITES

Kamelia ruskova

Abstract – The aim of this study is to investigate the structural changes between absorptive-

active fillers and rubber matrix in composite materials as a result of magnetic field impact. As

absorption-active filler was used isotropic magnetite filler and as anisotropic fillers: barium and

strontium-substituted hexaferrites with high field of intrinsic magnetic anisotropy. As a base for a

matrix were used different elastomeric materials. Exploring of the structural changes and

organization of the filler particles and rubber matrix was done under magnetic field impact. It is

obvious from the obtained optical microscopy data. The magnetic field was used during the film

formation with 1800Oe for 24-48h. The obtained composite materials with different ferromagnetic

fillers can be use for microwave absorbers for specific area of shielding applications..


Education and Learning Technologies


Chairpersons: Ivailo PANDIEV, Katya ASPARUHOVA

7.1. SIMULATION AND EXPERIMENTAL RESEARCH STRATEGY FOR DACS WITH PROTEUS AND OPEN SOURCE PLATFORMS –

Daniela Shehova, Slavi Lubomirov, Katya Asparuhova

Abstract – Modern digital information processing systems represent a challenge when it is

necessary to choose the circuits and devices in the digital channel and it is that which is the subject

of Digital to Analog Converters (DACs) and the devices that work with them. The study described

in the article is aimed at offering software and hardware solutions to study modern DACs and their

applications.

Simulation schemes for testing the parameters and characteristics of DAC through

simulation analysis in the Proteus environment have been designed and tested.

Laboratory modules have been developed using open source platforms to verify the

simulation results that have been obtained.

The proposed strategy for teaching DACs provides new opportunities for knowledge

organization and new ways of teaching and learning aimed at achieving higher quality of the

learning outcomes in engineering education.

7.2. RESEARCH AND TEACHING OF LINE CODING USING ORCAD AND EMONA INSTRUMENTS TRAINER IN ENGINEERING EDUCATION

Angel Chekicev, Daniela Shehova, Slavi Lyubomirov, Stanislav Asenov and Katya

Asparuhova

Abstract – The article discusses the use of the OrCad environment and the Emona Telecoms-

Training Lab ETT-101 for the research and teaching of Line coding in order to help students from

the engineering colleges learn the principles of building digital communication systems. The

simulations developed and presented and the laboratory layout allow examination and comparison


21

of the advantages and disadvantages of NRZ-B coding, RZ and RZ-B coding, and AMI coding. The

results of the simulation and experimental tests are presented too.

7.3. TEACHING METHODOLOGY FOR ALL DIGITAL PHASE LOCKED LOOP

Dimiter Badarov and Georgy Mihov

Abstract – This article discusses the methodology, the tasks, the material base and the

problems in the teaching process of all digital phase locked loop. Different types of phase and

phase-frequency detectors are examined. Their parameters are compared and the advantages and

disadvantages for different applications are discussed. Different types of digital integrators and

digital filters are developed and tested along with the different phase-frequency detectors. Different

circuits for Digitally Controlled Oscillator are developed and tested. Several different phase locked

loops are built and tested. Their parameters are compared and discussed.

7.4.

7.5. INTERACTIVE TEACHING METHODS USED IN THE COURSE DIGITAL ELECTRONICS

Adriana Borodzhieva, Ivanka Tsvetkova, Iordan Stoev, Snezhinka Zaharieva

Abstract – One way students to learn faster and for longer time is to learn by doing and

playing. The paper presents interactive methods used for improving knowledge that students will

get while implementing different circuits of latches and flip-flops and their testing on the laboratory

board developed at the University of Ruse in the course Digital Electronics..

7.6. DESIGN AND IMPLEMENTATION OF A SYSTEM FOR MONITORING AND CONTROL OF THE DRYING PROCESS AS A LEARNING OPPORTUNITY

REMOTELY

Nikolay Valov, Irena Valova

Abstract – There are some courses in engineering that cannot demonstrate the overall

production processes. Mathematical models of their most important parts are used in their teaching

so that students can gain an idea of their management and control. This article describes an idea

for a comprehensive follow-up of the process of drying fruits or vegetables. This is a relatively long

process, it can take more than a day. Students can set a selected automatic control and during the

drying process to monitor various output parameters and change others (input) remotely from their

laptops, computers or mobile devices.

7.7. OPERATIONAL AMPLIFIER OPEN LOOP GAIN SIMULATION IN ELECTRONICS ENGINEERING EDUCATION

Dimitar Tokmakov, Stanislav Asenov

Abstract – Simulating the open loop gain of an amplifier circuit is a highly misunderstood

subject in Electrical and Electronics Engineering. In order to address that, we describe four

methods that we use to successfully simulate operational amplifier open loop gain in engineering

education environment.

7.8. APPLICATION OF DIFFERENTIATED INSTRUCTION APPROACH IN COMPUTER SYSTEMS EDUCATION

Atanas Kostadinov, Krassimir Kolev⸸

Abstract – Sometimes there is a difference in student’s level of knowledge about university

course topics. The lecturer should present material to all participants instead of their background.

We have selected differentiated instruction approach to cope with mentioned problem. This method

22

has been used in Reconfigurable Logic, VLSI Design as well as Computer Modeling subjects.

Obtained results show that all students benefit from this approach.

7.9. TEACHING SIGNALS AND SYSTEMS VIA GENERAL PUBLIC LICENSE SOFTWARE DURING THE COVID-19 LOCKDOWN

Yuliyan Velchev, Kalin Dimitrov, Lubomir Laskov

Abstract – The work is focused on options for using the functionality of a GNU General

Public License free software. This license guarantee end users the freedom to study at home during

the lockdown. We focus our efforts for using GNU Octave. This software is a high-level

programming language, primarily intended for numerical computations. Octave is suitable for

illustrating of basic linear and nonlinear problems that occurs in telecommunications and are

studied in course Signals and systems. It is a good alternative of mostly used commercial software.

Specific features have been considered in designing of exercise. The methodology of exercise for

students is described.

7.10. STUDY THE IMPACT OF THE NEGATIVE FEEDBACKS ON THE CHARACTERISTICS OF THE AMPLIFIERS

Ivo Dochev, Stoycho Manev, Lilyana Docheva

Abstract – Education in the area of the analogue circuits design is based on deep knowledge

from the electrical engineering, circuits and systems and other scientific disciplines. One of the

main features of the education today is to make this process more attractive. By means of advanced

software products the design of certain analogue electronic circuit can be made easy to understand

for the great majority of the students.

7.11. DEVELOPMENT OF SINGLE-TRANSISTOR AMPLIFIERS MODULAR LABORATORY KITS FOR ELECTRONIC ENGINEERING EDUCATION

Ivailo Pandiev, Eltimir Stoimenov

Abstract – Transistor amplifiers laboratory kits have been developed and implemented for

electronic engineering education. Each of the two laboratory kits contains two single-stage

amplifier circuits that are constructed using discrete components. Objects of study are the AC

behavior of the two basic amplifier configurations with single BJT and MOSFET. In particular, for

development of the kits on separate printed circuit board common-emitter (CE) amplifier common-

source (CS) amplifier, common-collector (CC) or grounded collector amplifier and common drain

(CD) or grounded-drain amplifier are implemented. The modularity concept introduced in this

laboratory kits allows the student to perform an additional task by configuring the electronic

systems to change the operating point of the transistors or change the depth of negative feedback

and load type (active or active-capacitive). The proposed laboratory kits are intended for second-

year students on the Bachelor degree program of “Electronics” at the Technical University of

Sofia.

7.12. DISTANCE LEARNING AND REMOTE LABORATORY EXERCISES ON

POWER SUPPLY SYSTEMS

Dimitar Arnaudov, Ekaterina Otsetova-Dudin

Abstract – The article presents the results of training with remote laboratory exercises on power

supply systems. Problems with the assimilation of the study material and the operation of the

devices during remote laboratory exercises are discussed. It gave us specific points from a

methodological point of view that should be taken into account in this type of training.

23

FORUM “ELECTRONICA”

Virtual room 2, 23-24 July 2020.

Presentation of the Project “Optimal design and management of electrical

energy storage systems”, КП-06-H37/25/18.12.2019, Bulgarian National

Scientific Fund.

https://technicaluniversitysofia.my.webex.com/technicaluniversitysofia.my/j.php?MTID=mc471fd11fc32437f39120530da15af0f

24

INFORMATION

ELECTRONICA 2020 is technically Co-Sponsored by IEEE.

(IEEE Conference record # 50406)

The accepted and presented papers will be published in the conference Proceeding on

CD and submitted to IEEE Xplore Digital Library, Scopus database.

ДНТ

Address for correspondence

Address:

CEEC (Union of electronics, electrical engineering and telecommunications),

1000 Sofia, 108 Rakovski Str.

Phones:

+359 2 987 97 67

e-mail:

[email protected]

[email protected]

Web site:

http://ceec.fnts.bg

http://e-university.tu-sofia.bg/e-conf/?konf=28
http://ceec.fnts.bg/http://e-university.tu-sofia.bg/e-conf/?konf=28

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