Showing papers in "Automatika: Journal for Control, Measurement, Electronics, Computing and Communications in 2011"
TL;DR: In this paper, a wind farm controller design that utilizes coordinated power control of all wind turbines to achieve the wind farm regulation requirements and to minimize the wind turbine loads is proposed, and the opportunity for wind turbine load reduction that arises from dynamic power controlling of wind turbines is studied.
Abstract: The new grid regulations require that a grid-connected wind farm acts as a single controllable power producer. To meet this requirement a traditional wind farm control structure, which allowed individual wind turbines to internally define their power production, has to be modified. In this paper the opportunity for wind turbine load reduction that arises from dynamic power control of wind turbines is studied. The wind farm controller design is proposed that utilizes coordinated power control of all wind turbines to achieve the wind farm regulation requirements and to minimize the wind turbine loads.
83 citations
TL;DR: Basic concepts and foreseeable future developments in electroporator design are presented in this article.
Abstract: Electroporator is a generator of electric pulses that is used for permeabilization of cells. There are five major concepts of electroporation design. Capacitor discharge, square wave generator, and analog generator are used to generate classical electroporation pulses that are longer than microsecond and pulse forming network, and resonant charging generator that are used to generate nanosecond electroporation pulses. The choice of an electroporator design is always driven by the biotechnological or biomedical application. Electroporators can be used for introduction of small (electrochemotherapy) and large molecules (gene electrotransfer), cell fusion, insertion of proteins into cell membrane, electroporation of organelles, pasteurization, tissue ablation etc. Basic concepts and foreseeable future developments in electroporator design are presented in this article.
70 citations
TL;DR: The most popular methods for plant data-based modeling that appeared in the last two decades are summarized and briefly explained and tips about choosing the appropriate methodology for process model building are provided.
Abstract: There has been an increased use of soft-sensors in process industry in recent years. These soft-sensors are computer programs that are used as a relatively cheap alternative to hardware sensors. Since process variables, which are concerned with final product quality, cannot always be measured by hardware sensors, designing the appropriate soft-sensor can be an interesting solution. Additionally, a soft-sensor can be used as a backup sensor, when the hardware sensor is in fault or removed due to maintenance or replacement. Soft-sensor is based on the mathematical model of the process. Since industrial processes are generally quite complex, a theoretical modeling approach is often impractical, expensive or sometimes even impossible. Therefore, process model building is based on measured data. This approach significantly gets complicated if only plant data, taken from the process database, are available. In this paper the most popular methods for plant data-based modeling that appeared in the last two decades are summarized and briefly explained. Apart from giving a short survey of the most important papers, tips about choosing the appropriate methodology for process model building are also provided.
64 citations
TL;DR: In this paper, the authors proposed a virtual junction temperature estimation method based on the real-time measurement of semiconductor's quasi-threshold voltage using dedicated modified gate driver circuit.
Abstract: Temperature management and control are among the most critical functions in power electronic devices. Knowledge of power semiconductor’s operating temperature is important for circuit design, as well as for converter control. Virtual junction temperature measurement or estimation is not an easy task, therefore designing the appropriate circuitry for virtual junction temperature in the real operating conditions not affecting regular circuit operation is a demanding task for engineers. The proposed method enables virtual junction temperature estimation based on the real-time measurement of semiconductor’s quasi-threshold voltage using dedicated modified gate driver circuit.
35 citations
TL;DR: A novel heuristic for correcting scan pose estimations after loop closing in SLAM using 3D laser scans is presented, proving the high quality, yet achieved faster by an order of magnitude.
Abstract: This paper presents a novel heuristic for correcting scan pose estimations after loop closing in SLAM using 3D laser scans. Contrary to state of the art approaches, the built SLAM graph is sparse, and optimization is done without any iteration between the SLAM front and back end, yielding a highly efficient loop closing method. Several experiments were carried out in an urban environment and evaluated again st ground truth. The results are compared to other state of the art algorithms, proving the high quality, yet achieved faster by an order of magnitude.
26 citations
TL;DR: A formalism to encode spatio-temporal situations whose occurrences must be detected by a context-aware system is introduced, focusing on the system ability to combine in a centralized representation information originating from distributed sources.
Abstract: Ubiquitous Robotics is a novel paradigm aimed at addressing the coordinated behaviour of robots in environments that are intelligent per se. To this aim, suitable methods to enforce cooperative activities must be assessed. In this article, a formalism to encode spatio-temporal situations whose occurrences must be detected by a context-aware system is introduced. The Situation Definition Language is a tool used to specify relationships among classes of sensory data in distributed systems (such as those adhering to the Ubiquitous Robotics paradigm), without posing any assumption on how data themselves are acquired. The capabilities offered by the language are discussed with respect to a real-world scenario, where a team of mobile robots cooperates with an intelligent environment to perform service tasks. Specifically, the article focuses on the system ability to combine in a centralized representation information originating from distributed sources, either mobile (i.e., the robots) or fixed (i.e., the intelligent devices in the network).
11 citations
TL;DR: The exploration and mapping algorithm is proposed that extends Ekman's exploration algorithm by removing rigid constraints on the range sensor and robot localization by including line extraction algorithm developed by Pfister, which incorporates noise models of the range Sensor and robot's pose uncertainty.
Abstract: We consider problem of exploration and mapping of unknown indoor environments using laser range finder. We assume a setup with a resolved localization problem and known uncertainty sensor models. Most exploration algorithms are based on detection of a boundary between explored and unexplored regions. They are, however, not efficient in practice due to uncertainties in measurement, localization and map building. The exploration and mapping algorithm is proposed that extends Ekman's exploration algorithm by removing rigid constraints on the range sensor and robot localization. The proposed algorithm includes line extraction algorithm developed by Pfister, which incorporates noise models of the range sensor and robot's pose uncertainty. A line representation of the range data is used for creating polygon that represents explored region from each measurement pose. The polygon edges that do not correspond to real environmental features are candidates for a new measurement pose. A general polygon clipping algorithm is used to obtain the total explored region as the union of polygons from different measurement poses. The proposed algorithm is tested and compared to the Ekman's algorithm by simulations and experimentally on a Pioneer 3DX mobile robot equipped with SICK LMS-200 laser range finder.
10 citations
TL;DR: The PEISTable, an autonomous robotic table that can be embedded in a smart environment that can collaborate with other devices in the environment toperform more complex tasks, follows the PEIS Ecology model.
Abstract: There are two main trends in the area of home and service robotics The classical one aims at the developmentof a single skilled servant robot, able to perform complex tasks in a passive environment The second, more recenttrend aims at the achievement of complex tasks through the cooperation of a network of simpler robotic devicespervasively embedded in the domestic environment This paper contributes to the latter trend by describing the PEISTable, an autonomous robotic table that can be embedded in a smart environment The robotic table can operatealone, performing simple point-to-point navigation, or it can collaborate with other devices in the environment toperform more complex tasks Collaboration follows the PEIS Ecology model The hardware and software designof the PEIS Table are guided by a set of requirements for robotic domestic furniture that differ, to some extent, fromthe requirements usually considered for service robots
7 citations
TL;DR: In this article, a function-based design approach is proposed to formulate control of constrained system particularly bilateral systems in micromanipulation applications, with the control objective aimed to maintain desired functional relations between human and environment defining convenient tasks and their proper relations on master and slave motion systems.
Abstract: Design of a motion control system, convenient for a wide range of applications in industry, space, biology, medicine, particularly including more than one physics environment is very important. Well known control architectures like trajectory tracking, compliance control, interaction force control are scientific milestones which has common control task: to maintain desired system configuration. In this concept, motion control system can be an unconstrained motion-performed interaction with neither environment nor any other system, or constrained motion-system in contact with environment and/or other systems. This paper provides the function based design approach to formulate control of constrained system particularly bilateral systems in micromanipulation applications. The control objective aimed to maintain desired functional relations between human and environment defining convenient tasks and their proper relations on master and slave motion systems. Preliminary results concerning position tracking, force control and transparency between master and slave systems are clearly demonstrated.
6 citations
TL;DR: In this paper, the authors examined the compatibility of MFCC measure with human perception for different values of parameters in the analysis and found that truncated mel cepstral vector (12 coefficients) is justified for speech recognition, but may be arguable for speaker recognition.
Abstract: Currently, one of the most widely used distance measures in speech and speaker recognition is the Euclidean distance between mel frequency cepstral coefficients (MFCC). MFCCs are based on filter bank algorithm whose filters are equally spaced on a perceptually motivated mel frequency scale. The value of mel cepstral vector, as well as the properties of the corresponding cepstral distance, are determined by several parameters used in mel cepstral analysis. The aim of this work is to examine compatibility of MFCC measure with human perception for different values of parameters in the analysis. By analysing mel filter bank parameters it is found that filter bank with 24 bands, 220 mels bandwidth and band overlap coefficient equal and higher than one gives optimal spectral distortion (SD) distance measures. For this kind of mel filter bank, the difference between vowels can be recognised for full-length mel cepstral SD RMS measure higher than 0.4 - 0.5 dB. Further on, we will show that usage of truncated mel cepstral vector (12 coefficients) is justified for speech recognition, but may be arguable for speaker recognition. We also analysed the impact of aliasing in cepstral domain on cepstral distortion measures. The results showed high correlation of SD distances calculated from aperiodic and periodic mel cepstrum, leading to the conclusion that the impact of aliasing is generally minor. There are rare exceptions where aliasing is present, and these were also analysed.
5 citations
TL;DR: Parameters of an evoked potentials method with a vibratory stimulation technique are defined which would establish reliable and repeatable results applicable in a clinical usage and optimal stimulation parameters are defined as a prelude for a future research.
Abstract: In a clinical application, a method for an examination of a vibratory sense is not very objective and it depends on an active cooperation of a patient, which cannot be achieved in every situation. The aim of this research is to define parameters of an evoked potentials method with a vibratory stimulation technique which would establish reliable and repeatable results applicable in a clinical usage. During the research, different experimental conditions were performed (different methods of stimulation, different stimulation frequencies, different stimulus durations, different areas of stimulation). Presented results confirm the initial assumption that it is possible to detect reliable and repeatable cortical potentials evoked by the vibratory stimulation. Characteristic shapes and spatiotemporal distributions of evoked responses are established. Optimal stimulation parameters are defined as a prelude for a future research.
TL;DR: This paper presents an implementation of specific distance measure used to calculate distances between observations which is described by a mixture of variable types and comparison was made on different well-known datasets.
Abstract: Hierarchical clustering method is used to assign observations into clusters further connected to form a hierarchical structure. Observations in the same cluster are close together according to the predetermined distance measure, while observations belonging to different clusters are afar. This paper presents an implementation of specific distance measure used to calculate distances between observations which are described by a mixture of variable types. Data mining tool ‘Orange’ was used for implementation, testing, data processing and result visualization. Finally, a comparison was made between results obtained by using already available widget and the output of newly programmed widget which employs new variable types and new distance measure. The comparison was made on different well-known datasets.
TL;DR: Four different optimization algorithms that work at joint angle basis and use the joint angle difference as measure of similarity are proposed that generate a gait that is significantly more human-like compared to the robot's initial gate.
Abstract: Achieving a stable, human-like gait for humanoid robots is a challenging task. While a variety of techniques exist to generate stable walking patterns, only little attention has been paid to the resemblance to the human gait. Popular gaits, for example, apply the strategy to bend the knees and to swing the torso in the lateral direction in order to ensure stability by shifting the center of mass. As a result, the walking patterns do not look very human-like. However, human resemblance is an important aspect whenever robots are designed to coexist and interact with humans. In this article, we present techniques to optimize a given, stable gait of a humanoid robot with respect to human resemblance. To acquire human data, we use a full-body motion capture system. We propose four different optimization algorithms that work at joint angle basis and use the joint angle difference as measure of similarity. The experiments carried out with a HOAP-2 robot in simulation demonstrate that all techniques generate a gait that is significantly more human-like compared to the robot's initial gate. As the results show, the optimization methods based on hill climbing and policy gradient estimation yield the best performance.
TL;DR: In this article, the root canal length was measured in vitro on extracted tooth in alginate material using HP 4284A LCR meter and a specially designed stalk with a micrometer for precise file positioning.
Abstract: An accurate determination of the root canal length, which is the most critical procedure in the endodontic treatment of a tooth, is commonly performed nowadays by electronic apex locators which are based on electrical impedance measurements. In this paper tooth impedances were measured in vitro on extracted tooth in alginate material using HP 4284A LCR meter and a specially designed stalk with a micrometer for precise file positioning. In order to develop a more accurate measurement procedure human tooth was modeled by electrical equivalent circuit. Four new equivalent circuits comprising of resistors, capacitors and constant-phase elements were proposed in this paper and compared with four previously suggested circuits. Elements of equivalent circuits were determined by complex nonlinear least squares fitting using LEVM software. Different quality factors were defined to describe the fit quality of a certain equivalent circuit at each file position. The overall fitting efficiency in the region of file positions of interest was calculated as well. A detailed discussion was given on equivalent circuit parameters that can be used to measure the root canal length. Upon these results the most appropriate equivalent circuit was selected and a new measurement procedure was proposed.
TL;DR: This paper deals with analytical and simulation approach for choice of activation functions and instead of a number of nodes for a class of neural network controllers for frequency control of thermal power systems.
Abstract: This paper deals with analytical and simulation approach for choice of activation functions and instead of a number of nodes for a class of neural network controllers for frequency control of thermal power systems. Neural network update laws are derived via Lyapunov like stability analysis. When number of nodes is fixed, then simulation analysis is conducted to find the best performer activation function. B est performance is chosen using integral error criteria and proper statistical tests.
TL;DR: Progress made in combining ontology-based information models is described and the importance of the role of multiscale systems engineering is explained.
Abstract: Multiscale systems engineering provides a way to integrate models of real-world phenomena that allows a holistic understanding of component interactions at different levels of scale simultaneously. The discipline draws upon information engineering to provide ontological representations that are derived from digital libraries of terms, themselves found at distributed locations around the world. Cardiac development is well understood within discrete levels of analysis. The application of the multiscale framework gives added value by unlocking the relationships between genetic-based information at one level of analysis and the phenotype it encodes for at the cell and organ levels of abstraction. The multiscale-based relationships have begun to demonstrate new insights into normal cardiac development and conditions that give rise to congenital heart diseases such as the tetralogy of Fallot. This paper describes progress made in combining ontology-based information models and explains the importance of the role of multiscale systems engineering.
TL;DR: The development of biomedical engineering and its affirmation has mainly appeared in the last 50 years, first as a result of development in electronic industry while later it started developing at its own pace.
Abstract: Medicine and health care have changed dramatically in the past few decades and they depend on high technology for prevention, diagnosis and treatment of diseases, and for patient rehabilitation. Modern biomedical research and health care are provided by multidisciplinary teams in which biomedical engineers contribute to the advancement of knowledge equally as medical professions. Biomedical engineering represents one (out of two) the most rapidly growing branches of industry in the developed world [1] (the other are sustainable and renewable energy sources). The new knowledge gained by basic biomedical engineering research (at gene, molecular, cellular, organ and system level) has high impact on the growth of new medical products and boosts industries, including small and medium size enterprises (SMEs). SMEs are expected to bring to the market new products and services for health care delivery [2]. Health is the major theme of the specific Programme on Cooperation under the European Seventh Framework Programme, with a total budget of \euro 6.1 billion over the duration of FP7. The objective of health research under FP7 is to improve the health of European citizens and stir up the competitiveness of health-related industries and businesses, while addressing global health issues, life improving and develop life saving technologies. Hospitals and other medical institutions have a commitment to take care of all kinds of high technology devices including the hospital information systems, networks and their safety and security. Growing technological participation in health services enforces the support of technologically specialized personnel, trained clinical engineers. Worldwide, the educational system has adopted the curricula of biomedical engineering and of clinical engineering. Professional organizations are building certification system for biomedical and clinical engineers and the continuous education (life long learning) structures. The development of biomedical engineering and its affirmation has mainly appeared in the last 50 years, first as a result of development in electronic industry while later it started developing at its own pace. In the first part of this paper, we address the development of biomedical engineering in that period and present our views on the development of biomedical engineering in the future. The second part is devoted to the International Federation for Medical and Biological Engineering (IFMBE), the largest organization of biomedical engineers in the world which celebrated its 50th anniversary in 2009. In the third part, we recall our memories to the founder of biomedical engineering in Croatia, prof. Ante Santic and his achievements in biomedical engineering, and present the state of art of biomedical engineering research and education in Croatia.
TL;DR: This paper addresses the issue of custom written ETL procedure tests and works towards establishing a generic procedure for integration testing of certain aspects of ETL procedures, and provides a basic testing foundation or augments existing data warehouse system's testing capabilities.
Abstract: In order to attain a certain degree of confidence in the quality of the data in the data warehouse it is necessary to perform a series of tests. There are many components (and aspects) of the data warehouse that can be tested, and in this paper we focus on the ETL procedures. Due to the complexity of ETL process, ETL procedure tests are usually custom written, having a very low level of reusability. In this paper we address this issue and work towards establishing a generic procedure for integration testing of certain aspects of ETL procedures. In this approach, ETL procedures are treated as a black box and are tested by comparing their inputs and outputs - datasets. Datasets from three locations are compared: datasets from the relational source(s), datasets from the staging area and datasets from the data warehouse. Proposed procedure is generic and can be implemented on any data warehouse employing dimensional model and having relational database(s) as a source. Our work pertains only to certain aspects of data quality problems that can be found in DW systems. It provides a basic testing foundation or augments existing data warehouse system's testing capabilities. We comment on proposed mechanisms both in terms of full reload and incremental loading.
TL;DR: In this article, the buck converter size can be reduced by eliminating the filter capacitor and replacing it with an output current ripple compensation circuit, based on inductor current measurement and linear amplifier.
Abstract: Low-power switched-mode power supply converters are used in applications where size and efficiency are critical. The buck converter size can be reduced by elimination of the bulky filter capacitor. The filtering function of this capacitor can be replaced by an output current ripple compensation circuit. The compensating circuit is applied, based on inductor current measurement and linear amplifier. The proposed compensating algorithm is investigated theoretically by simulation, and verified experimentally.
TL;DR: In this article, a nonlinear multivariate prediction model was made deploying a Support Vector Machine (SVM) classifier to identify patients at high risk of post-operative atrial fibrillation.
Abstract: In patients undergoing Coronary Artery Bypass Grafting (CABG) surgery postoperative atrial fibrillation (AF) occurs with prevalence of up to 40%. The highest incidence is between the second and third day after the operation. Following cardiac surgery AF causes various complications, hemodynamic instability, and can cause heart attack, cerebral and other thromboemolisms. AF increases morbidity, duration and expense of medical treatment. This study aims to identify patients at high risk of postoperative AF. An early prediction of AF would provide a timely prophylactic treatment and would reduce incidence of arrhythmia. Patients at low risk of postoperative AF could be excluded from the side effects of anti- arrhythmic drugs. The investigation included 50 patients in whom lead II electrocardiograms were continuously recorded for 48 hours following CABG. Univariate statistical analysis was used in the search of signal features that might predict AF. The most promising identified features were: P wave duration, RR interval duration and PQ segment level. On the basis of these a nonlinear multivariate prediction model was made deploying a Support Vector Machine (SVM) classifier. The prediction accuracy was found uprising over the time. At 48 hours following CABG ; the measured best average sensitivity was 95.9% and specificity 93.4%. The positive and negative predictive accuracy were 88.9% and 98.8%, respectively and the overall accuracy was 94.6%. In regard to the prediction accuracy, the risk assessment and prediction of postoperative AF are optimal to be done in the period between 24 and 48 hours following CABG.
TL;DR: Design and implementation of a nonlinear control algorithm for excitation control system based on the Lyapunov's direct method were implemented and tested on the real time simulator and obtained simulation results show that proposed nonlinearexcitation control algorithm better damps electromechanical oscillations than conventional excite control algorithm.
Abstract: This paper proposes a DSP based simulator for development and implementation of control algorithms. The simulator is used to control a synchronous aggregate model in real time. The simulator consists of a PC (on which a synchronous generator connected to AC network is simulated) connected through a communication channel to a DSP (on which the control algorithm is implemented). The simulator makes implementation of a control algorithm faster and easier. It also enables verification of a control algorithm in real time. Simulation results show that there are no significant differences between non-real time simulations (on a PC) and real time simulations (on a DSP based simulator). This paper also presents design and implementation of a nonlinear control algorithm for excitation control system based on the Lyapunov's direct method. Both conventional excitation control algorithm and proposed nonlinear excitation control algorithm were implemented and tested on the real time simulator. The obtained simulation results show that proposed nonlinear excitation control algorithm better damps electromechanical oscillations than conventional excitation control algorithm.
Journal Article•
TL;DR: In this article, the authors investigated the behavior of Mobile IP protocol in presence of route optimization procedure and showed that using priority scheduling for packets received from the Home Agent and queued at the old Foreign Agent's buffer after handover can reduce the number of disordered packets received at the new Foreign Agent after handoff.
Abstract: The increasing number of portable computers, combined with the growth of wireless services, makes supporting Internet mobility important. Since a mobile node always changes its point of attachment to the Internet, it may cross a cell boundary during data transmission process. Packets sequence disruption during handover procedure may result in decreasing network performance especially in higher layers protocols. In this paper we investigate the behavior of Mobile IP protocol in presence of route optimization procedure. We discuss the impact of handover process on packets routed from old Foreign Agent to new Foreign Agent after handover and show that using priority scheduling for packets received from the Home Agent and queued at the old Foreign Agent's buffer after handover can reduce the number of disordered packets received at the new Foreign Agent after handover.
TL;DR: In this article, a pregled pre-gled sigurnosti usmjeravanja u ad hoc mrežama is presented, i opisani su glavni sigurnosni problemi u usmjerni protokola.
Abstract: Ad hoc mreže specificne su po svojim karakteristikama (necentraliziranost, samoorganiziranje i viseskokovnost). Zbog toga usmjerni protokoli u ad hoc mrežama moraju biti prilagođeni pojedinim primjenama mreže i zadovoljavati glavne zahtjeve - propusnosti, skalabilnost i sigurnost. U radu je prikazan pregled sigurnosti usmjeravanja u ad hoc mrežama. Navedena su svojstva ad hoc mreža i izazovi razvoja protokola usmjeravanja u njima. Opisani su glavni sigurnosni problemi u usmjeravanju i metode ispitivanja sigurnosti usmjernih protokola.
TL;DR: The comprehensive beam tracing method (CBTM) as discussed by the authors is a beam-division algorithm for non-homogeneous environments that is best suited for acoustic and hydro-acoustic simulation of nonhomogenous environments.
Abstract: In order to expand the area of use of beam tracing method, the comprehensive beam tracing method (CBTM) was developed. CBTM is best suited for acoustic and hydro-acoustic simulation of non-homogenous environments. CBTM can trace both refraction as well as reflection of sound wave, using triangular beams. The geometry of scene in CBTM is based on triangles meshes rather than polygons, so complex, irregular shaped objects can be simulated. Furthermore, CBTM traces beams thorough several volumes with different media, allowing for non-convex volumes. This paper presents the algorithms and data structures used for the process of beam division that occurs during the interaction of beam with complex, non-convex environment. Paper also brings measurements of the implemented beam division code and comparison of measured results with results of other methods.