ON DESIGN OF SELF-TUNING ACTIVE FILTERS

In this paper, we present one approach in design of self-tuning all-pass, band-pass, low-pass and notch filters based on phase control loops with voltage-controlled active components and analyze their stability as well. The main idea is to vary signal delay of the filter and in this way to achieve phase correction. The filter phase characteristics are tuned by varying the transconductance of the operational transconductance amplifier or capacitance of an MOS varicap element, which are the constituents of filters. This approach allows us to implement active filters with capacitance values of order of pF, making the complete filter circuit to be amenable for realization in CMOS technology. The phase control loops are characterized by good controllable delay over the full range of phase and frequency regulation, high stability, and short settling (locking) time. The proposed circuits are suitable for implementation as a basic building RF function block, used in phase and frequency regulation, frequency synthesis, clock generation recovery, filtering, selective amplifying etc

REVIEWING THE PHOTOVOLTAIC POTENTIAL OF BIJELJINA IN THE REPUBLIC OF SRPSKA

To estimate PV potential of Bijeljina, PVGIS and SOLARGIS databases were used. The results showed that Bijeljina municipality has an average daily PV power potential of 3.50 kWh/kWp, thus belonging to areas with the favorable mid-range PV power potential values. Average levelized cost of electricity is $0.12/kWh, consequently making PV technologies in Bijeljina also economically competitive with conventional power-generating sources. In the light of the rapid development of photovoltaic technology, this paper gives a critical review of previous studies and suggests that the application of PV technologies has become even more attractive. High-efficiency PV modules and grid inverters were tested on examples of roof-mounted PV systems and ground-mounted PV system using specialized PVSYST software. Comparison of the obtained results with previous studies gave a clear picture with advantages of these new solutions, and further support for PV technologies utilization

Determination of internal pressure value causing pipe branch model to plastically deform

Složenost geometrije posuda pod pritiskom obično predstavlja uzrok pojave koncentracije napona i deformacija. Savremeni pristup analize stanja napona i deformacija uključuje numerička i eksperimentalna ispitivanja. Svako eksperimentalno testiranje na realnoj konstrukciji može ugroziti samu konstrukciju. Stoga, pravljenje modela neke konstrukcije ima velike prednosti. Umanjeni model račve A6 trećeg cevovoda na HE Perućica, Nikšić je izrađen kako bi bio podvrgnut detaljnom eksperimentalnom testiranju. Cilj je bio da se odredi vrednost unutrašnjeg pritiska koji dovodi do plastične deformacije na modelu račve i da se ovi rezultati koriste za određivanje pritiska koji će stvarnu konstrukciju dovesti do plastičnog deformisanja bez ikakvih merenja na samoj konstrukciji. Eksperimentalna merenja su sprovedena metodom mernih traka. Merne trake su pozicionirane na kritične zone. Numerički model i rezultati dobijeni metodom konačnih elemenata (FEM) potvrđeni su eksperimentalnim rezultatima (u oblasti elastičnosti). Nakon verifikacije u elastičnoj oblasti, povećanjem pritiska, eksperimentalno određena je kritična vrednost unutrašnjeg pritiska koji je izazvao plastičnu deformaciju modela račve. Na osnovu ponašanja modela račve i nakon određivanja odnosa između modela i stvarne konstrukcije, procenjuje se maksimalna izračunata vrednost unutrašnjeg pritiska na koju se realna konstrukcija može izložiti. Pored toga, slabe tačke na konstrukciji su potvrđene dobijanjem istih rezultata kroz eksperiment i proračun, što daje dobre smernice za praćenje ove konstrukcije tokom eksploatacije, s obzirom na to da je ovakvom analizom moguće smanjiti broj mernih mesta za praćenje (u smislu da se kontrolišu tačno ona merna mesta koja su se pokazala kao najkritičnija).Complexity of pressure vessels geometry usually causes stress and strain concentrations. Modern approach of stress and strain analysis involves numerical and experimental testing. Every experimental testing on the construction could endanger construction itself. Therefore, making a model of the construction has great benefits. Sub-sized model of the pipe branch of A6 third pipeline at Hydropower Plant Perućica, Nikšić was made in order to be subjected to a detailed experimental testing. The aim was to determine internal pressure value causing pipe branch model to plastically deform, and, to use these results for determining pressure causing real structure to plastically deform, without any measurements on the structure itself. Experimental measurements were carried out using strain gauge method. Strain gauges are positioned in critical zones. Numerical pipe branch model and results obtained by using finite element method (FEM) was verified with experimental results (in elasticity area). After verification in elastic area, experimentally by increasing pressure value, critical internal pressure causing plastic deformation of pipe branch model was determined. Based on the pipe branch model behaviour, and after determination of relation between the model and the real structure, maximum calculated internal pressure value to which the structure may be subjected in exploitation is assessed. Besides, weak spots on the structure were verified by obtaining the same results through experiment and calculation, which gives good guidelines for monitoring of this structure during usage, since it is possible, by using this analysis, to decrease the number of measurement locations for monitoring (in order to control exactly those measurement locations, which proved to be the most endangered)

DATA COLLECTION TOOL FOR PROCESS IDENTIFICATION USING PLC AND KEPWARE TOOLS

In this paper, we are using the Kepware tools as a data collection tool to collecting data for identifying the process and making the mathematical models is described in this paper. The connection to the process was made using a programmable logic controller like a real time DAQ (Data Acquisition Board and System) device, database and a client application developed for these purposes. Special attention is paid to the possibility of collecting a large amount of process data as the same moment time of data sampling

SELF-TUNING LOW-NOISE AMPLIFIER

A low-noise amplifier with a phase control loop is described in this paper. In the proposed circuit, the resonant frequency is auto-tuned to the input signal frequency. In that way, high gain (20 dB), a phase shift of -180o between input and output signals, and good selective characteristics are obtained. The amplifier is robust to parameter variations, ensuring maximal amplification of the input signal regardless of its frequency as long as it is within a specified frequency range (880-950 MHz). Hence, the proposed circuit possesses self-tuning properties. The stability of the phase loop is analyzed by using Lyapunov's control theory

IMPLEMENTATION OF MODERN INTELLIGENT CONTROL METHODS WITHIN THE CONTROL SYSTEMS STUDY MODULE

This paper presents an innovative project “Implementation of Modern Intelligent Control Methods within the Study Module Control Systems” which is selected to be financed by Serbian Ministry of Education, Science and Technological Development. The project is part of a public call for projects “Development of Higher Education” and it will be realized during a school year 2018/2019. In this paper, the main goals of the project are presented and project activities and expected results are defined. Finally, three courses which are selected to be innovated through the project activities are presented in the terms of lecture topics and teaching methods

THE WINDER DANCER POSITION CONTROL MODEL USING DIFFERENT PID CONTROL STRUCTURES AND MICROLOGIX PLC

In the cable industry, improper regulation of the winding speed of the conductor cable, i.e. the position of the tensioner (dancer) leads to improper stretching of the conductor, which significantly affects the characteristics of the final product. Winding speed control is directly related to tensioning which is an additional problem. This paper presents a system for control a cable winding device using a linear PID controller with and without control signal limitation. The system parameters were determined using integral time-weighted absolute error (ITAE) criteria and realized using a conventional PLC controller

ANALASYS OF TWO LOW-COST AND ROBUST METHODS FOR INDOOR LOCALISATION OF MOBILE ROBOTS

This paper presents two simple and cost effective indoor localisation methods. The first method uses ceiling-mounted wide-view angle webcam, computer vision and coloured circular markers, placed on the top of a robot. Main drawbacks of this method are lens distortion and sensitivity to lighting conditions. After solving these problems, a high localisation accuracy of ±1cm is achieved at about 5 Hz sampling rate. The second method is a version of trilateration, based on ultrasound time of flight distance measurement. An ultrasonic beacon is placed on a robot while wall detectors are strategically placed to avoid an excessive occlusion. The ZigBee network is used for inter-device synchronisation and for broadcasting measured data. Robot location is determined as a solution to the minimisation of measurement errors. Using Nelder-Mead algorithm and low-cost distance measuring devices, a solid sub 5 cm localisation accuracy is achieved at 10Hz

Functionality and Palatability of Yogurt Produced Using Beetroot Pomace Flour Granulated with Lactic Acid Bacteria

Following the idea of sustainability in food production, a yogurt premix based on beetroot (Beta vulgaris) pomace flour (BPF) was developed. BPF was granulated with lactose solution containing lactic acid bacteria (LAB) by a fluidized bed. Particle size increased ~30%. A decrease in Carr Index from 21.5 to 14.98 and Hausner ratio from 1.27 to 1.18 confirmed improved flowability of granulated BPF, whereas a decrease in water activity implied better storability. Yogurts were produced weekly from neat starters and granulated BPF (3% w/w) that were stored for up to one month (4 °C). High viability of Streptococcus thermophilus was observed. Less pronounced syneresis, higher inhibition of colon cancer cell viability (13.0–24.5%), and anti-Escherichia activity were ascribed to BPF yogurts or their supernatants (i.e., extracted whey). Acceptable palatability for humans and dogs was demonstrated. A survey revealed positive consumers’ attitudes toward the granulated BPF as a premix for yogurts amended to humans and dogs. For the first time, BPF granulated with LAB was used as a premix for a fermented beverage. An initial step in the conceptualization of a novel DIY (do it yourself) formula for obtaining a fresh yogurt fortified with natural dietary fiber and antioxidants has been accomplished

LABORATORY CNC MACHINE FOR EDUCATION OF STUDENTS IN CONTROL SYSTEMS ENGINEERING

Modern states seek to build a society based on knowledge, and in this sense, the IPA project ADRIA HUB aims to connect students, universities and companies into a single entity in which each party realizes many benefits. Practical part of this project consists of the pilot projects related to the improvements in the woodworking industry. For the purpose of the project realization, a specific laboratory CNC machine was designed and implemented by the Laboratory for Modeling, Simulation and Control Systems at the Faculty of Electronic Engineering in Niš. CNC machine, presented in this paper, is now actively used in laboratory work. Students have the opportunity to gain practical knowledge and master the techniques of controlling this machine as part of their studies in Control Systems Engineering