Multimodeling Control via System Balancing

A new approach in multimodeling strategy is proposed. Multimodel strategies in which control agents use different simplified models of the same system are being developed using balancing transformation and the corresponding order reduction concepts. Traditionally, the multimodeling concept was studied using the ideas of multitime scales (singular perturbations) and weak subsystem coupling. For all reduced-order models obtained, a Linear Quadratic Gaussian (LQG) control problem was solved. Different order reduction techniques were compared based on the values of the optimized criteria for the closed-loop case where the full-order balanced model utilizes regulators calculated to be the optimal for various reduced-order models. The results obtained were demonstrated on a real-world example: a multiarea power system consisting of two identical areas, that is, two identical power plants

The system order reduction via balancing in view of the method of singular perturbation

U radu je predstavljeno nekoliko tehnika za redukciju reda sistema, poznatih iz literature, koje su sve zasnovane na uravnoteženju sistema uz primenu metode singularnih perturbacija. Ove tehnike imaju istu robusnost tačnosti izračunatu u skladu sa H∞ normom sistema redukovanog reda kao i dve tehnike poznate pod nazivom direktno odsecanje i metod balansirane rezidualizacije. Modifikacija ovih tehnika zadržava tačnu vrednost pojačanja jednosmernog signala kakva je kod originalnog sistema i daje aproksimaciju od veoma dobre do odlične tačnosti na nižim i srednjim učestanostima. Efikasnost prikazanih tehnika za redukciju reda modela data je na realnom primeru.This paper presents several techniques for system order reduction, known from literature, all of them based on system balancing by employing the method of singular perturbation. These techniques have the same robustness accuracy evaluated with respect to the H∞ norm of the reducedorder system like two techniques known as the direct truncation and the balancing residualization method. A modification of these techniques preserves the exact DC gain as the original system, and produces from very good to excellent accuracy at low and medium frequencies. To illustrate the efficiency of the order-reduction techniques here presented, a real simulation example is given

A MULTIVARIATE ANALYSIS OF CROATIAN COUNTIES ENTREPRENEURSHIP

In the focus of this paper is a multivariate analysis of Croatian Counties entrepreneurship. Complete data base available by official statistic institutions at national and regional level is used. Modern econometric methodology starting from a comparative analysis via multiple regression to multivariate cluster analysis is carried out as well as the analysis of successful or inefficacious entrepreneurship measured by indicators of efficiency, profitability and productivity. Time horizons of the comparative analysis are in 2004 and 2010. Accelerators of socio-economic development - number of entrepreneur investors, investment in fixed assets and current assets ratio in multiple regression model are analytically filtered between twenty-six independent variables as variables of the dominant influence on GDP per capita in 2010 as dependent variable. Results of multivariate cluster analysis of twentyone Croatian Counties are interpreted also in the sense of three Croatian NUTS 2 regions according to European nomenclature of regional territorial division of Croatia

Application of robust order reduction in modeling and control of real systems and objects in mechanical engineering

Дисертација „Примена робусне редукције реда система у моделовању и управљању реалним објектима у машинству“ је посвећена техникама и методама за редукцију реда линеарних модела, представљених у простору стања, као и условима и ограничењима за њихову примену. Приказан је концепт сингуларних пертурбација и његова примена у редукцији сложености модела система. Размотрене су различите карактеризације линеарних модела великог реда, чије репрезентације моделима у простору стања имају различите временске скале или и мали параметар (имају матрице великих димензија са пуно нула-елемената или са елементима, чији се редови величине веома разликују). Представљени су: сингуларно пертурбовани слабо повезани системи, слабо повезани системи, сингуларно пертурбовани системи, квази сингуларно пертурбовани системи и квази слабо повезани системи. Свака од ових класа представљена је одговарајућим моделом у простору стања неког реалног система. Детаљније је изложен прорачун регулатора за линеаран сингуларно пертурбован систем. Описана је метода балансирања, као и технике за редукцију реда линеарних модела, познате из литературе, које захтевају примену трансформације балансирања: балансирано одсецање, балансирана резидуализација, генералисана балансирана резидуализација, кориговано балансирано одсецање, метода заснована на брзом подсистему уз одбацивање спорог, модификована генералисана балансирана резидуализација, као и реверзна техника резидуализације. Свака од ових техника даје по један модел редукованог реда, полазећи од балансираног модела пуног реда. Технике изложене у овој тези, примењене су на редуковање реда четири модела реалних система. Први је модел бинарне дестилационе колоне са прегревачем и девет подова. Други је модел у простору стања борбене летелице L-1011. Трећи је математички модел каталитички контролисане реакције, из процесне технике. Четврти је математички модел дела електроенергетског система Србије, сачињен од две машине. Изложена је и редукција реда модела нестабилних линеарних система, на основу изабране литературе...The dissertation Application of Robust Order Reduction for Modeling and Control of Real Systems in Mechanical Engineering is dealing with techniques and methods of order reduction for linear models in the state space representation, as well as with conditions and limitations of their applicability. Well known concept of singular perturbations is described with its application in reduction of complexity of the system’s model. Different characterizations of large scale linear models are overviewed, having state space representations who exhibit different time scales or small parameter, too. These models have matrices of large dimensions with many zero-elements or elements with different size order, some very large and others very small. The singularly perturbed and weakly coupled systems, the weakly coupled systems, the singularly perturbed systems, the quasy singularly perturbed systems and the quasy weakly coupled systems are listed and represented here. Each class of these is represented with corresponding state space model of one real system. The design of the regulator for the linear singularly perturbed system is described in detail. The balancing method is analyzed, as well as techniques for the order reduction of linear model’s, known from the literature. These require application of the balancing transformation: the balancing truncation, the balancing residualization, the generalized balancing residualization, the corrected balancing truncation, the method based on the fast subsystem with rejection of the slow subsystem, the modified generalized balancing residualization, as well as the reversed residualization technique. Each of these techniques mentioned gives one model of reduced order, starting from the balanced full order model. Techniques represented in this thesis are applied on order reduction of four real system’s models. The first is the state space model of binary distillation column, with condenser, reboiler and nine plates. The second is the state space model of L-1011 fighter aircraft. The third is a mathematical model of the controlled catalytic reaction, from process engineering. The fourth part is a mathematical model of the part of electric power system of Serbia, consisting of two machines. Described here is the order reduction for models of unstable linear systems as well, based on the chosen references..

Digital battery capacity meter with battery charger

U radu je razvijen i prikazan digitalni merač kapaciteta akumulatora, sa integrisanim punjačem. Takođe, razvijen je i upravljačko / kontrolni softver za mikrokontroler ovog uređaja i PC računar, kako bi se podaci dobijeni merenjem, dalje mogli obrađivati i upoređivati, korišćenjem nekog od programa za tabelarna izračunavanja. Zbog široke primene elektro-hemijskih izvora, bilo primarnih, bilo akumulatorskih, izuzetno je važno poznavati i meriti njihov kapacitet. Merenje kapaciteta primarnih ćelija pomaže pri odabiru najpovoljnijeg rešenja (u skladu sa odnosom cene i kapaciteta) za napajanje prenosivih uređaja. Merenjem kapaciteta akumulatora, može se utvrditi njihovo stanje i da li su spremni za dalju eksploataciju, a i proveriti kapacitet novih akumulatora, na primer, radi upoređivanja sa podacima u tehničkoj dokumentaciji proizvođača.In this paper, a digital battery capacity meter with an integrated battery charger is developed and built. Also, the software used to control and monitor the microcontroller of the device from the PC has been developed, so that the data obtained from measurement can be processed and compared further using one of the available spreadsheet software packages. Due to the widespread use of electrochemical energy sources, whether primary ones or of the battery type, it is extremely important to know and measure their actual capacity. Primary cell capacity measurement helps in selecting the most appropriate solution (with respect to the cost/ capacity ratio) for powering portable or mobile devices. By measuring the capacity of the used battery, its condition and capability of further exploitation can be determined. Measuring capacity can provide verification of the data in the manufacturer's specifications, for example, in order to compare measurements and confirm statements in technical documentation

The Baltic Dry Index and performance excellence in a crisis environment

This paper focuses on an approach to analyzing the relationship between the Baltic Dry Index (BDI) as the main indicator of the cyclical nature of the maritime market and the performance excellence of the representative shipping companies. Results have shown that there is a strong positive correlation between average annual BDI values and performance excellence indicators measured by the traditional adjusted Altman Z-score as well as the recent indicator, the Bex Index. BDI as the most comprehensive indicator of global demand for commodities and raw materials is also analyzed as a supply and demand signal on the stock market. The aim was to test the hypothesis that BDI also functions as a signal that promptly responds to crisis effects. The methodological procedure has been carried out using a real database spanning from 1985 to 2013 where the results have confirmed the hypothesis

A cluster analysis of Croatian counties as the base for an active demographic policy

This paper deals with Croatian counties cluster analysis as the base for developing a proactive demographic policy. Unfortunately, Croatia has no national demographic strategy and no national population policy is carried out. Some local governments are taking isolated policy measures but due to an unsystematic and distressed network at the national level it has to date given no significant effects. The Croatian nation is currently experiencing the initial process of demographic extinction. This process began even before the great emigration wave that started about a year and half ago. Since there are no financial resources for the simultaneous and complete implementation of an active demographic policy across the entire Croatian territory, this paper proposes a new approach. Namely, the main demographic indicators have been calculated and analyzed for each Croatian county. After that, using a multivariate methodology, fifteen demographic indicators that significantly differ from county to county were selected as criteria for clustering Croatian counties by k-means method. Clustering output defines several clusters consisting of a smaller number of counties with similar demographic characteristics. These clusters form a spatial county unit in which appropriate measures of an active demographic policy should be urgently implemented. In this way the process of active demographic policy can start with less financial resources and can be limited maybe only to spaces with poorest demographic characteristics. Moreover, the results of this study might very well stimulate "richer” government units to carry out the appropriate active demographic policy measures in their areas without waiting for the adoption of laws and regulations at the national state level

The contact and compacting pressures influences on the quality of the friction welded joint

The theoretical and experimental analyses of the friction welding pressure influence on the plastic deformation level and the quality of the friction welded joint are presented in this paper. The joint of the tempering and the High-Speed steel was realized by the friction welding. The objective was to relate the two basic process parameters - the friction and compacting pressures - to plastic deformation parameters during the friction welding of two the steels. The fact that materials are dissimilar additionally complicates the welding procedure and its analysis. The friction welding is a specific and complex process, since in the joint zone material is heated and plasticized with necessary action of the multi-step pressure to realize the joint. The total deformations in the axial and radial directions are directly dependent on the applied welding pressure. Considering that geometry and shape of the friction welded joint directly depend on the friction pressure, some welded joints' basic shapes obtained with various pressures are presented. The experimental investigation was conducted on cylindrical samples made of the two steels and the analysis of results served for establishing the influences of the friction and compacting pressures on changes of the steel samples dimensions and shapes.

The contact and compacting pressures influences on the quality of the friction welded joint

The theoretical and experimental analyses of the friction welding pressure influence on the plastic deformation level and the quality of the friction welded joint are presented in this paper. The joint of the tempering and the High-Speed steel was realized by the friction welding. The objective was to relate the two basic process parameters - the friction and compacting pressures - to plastic deformation parameters during the friction welding of two the steels. The fact that materials are dissimilar additionally complicates the welding procedure and its analysis. The friction welding is a specific and complex process, since in the joint zone material is heated and plasticized with necessary action of the multi-step pressure to realize the joint. The total deformations in the axial and radial directions are directly dependent on the applied welding pressure. Considering that geometry and shape of the friction welded joint directly depend on the friction pressure, some welded joints' basic shapes obtained with various pressures are presented. The experimental investigation was conducted on cylindrical samples made of the two steels and the analysis of results served for establishing the influences of the friction and compacting pressures on changes of the steel samples dimensions and shapes.

Fizikalne i metalurške promjene tijekom zavarivanja trenjem brzoreznog i kaljenog čelika

This paper outlines the basic principles of welding by friction of high-speed cutting steel and tempered steel from the viewpoint of metallurgic processes that are going on in the material. The bases of welding by friction of different materials are outlined in a theoretical way. The experimental part of the paper also relates to friction welding of samples made of different metals: high-speed cutting steel (HS 6-5-2-5) on one hand and the tempered steel (C60) on the other.Ovaj rad daje osnovne principe zavarivanja trenjem brzoreznog čelika i kaljenog čelika s motrišta metalurškog procesa koji se odvija u materijalu. Osnove zavarivanja trenjem različitih materijala navedene su teorijski. Eksperimentalni dio rada odnosi se na zavarivanje trenjem uzoraka izrađenih od različitih metala: brzoreznog čelika (HS 6-5-2-5) s jedne i kaljenog čelika (C60) s druge strane