Volumen 12 (2017): Heft 1 (July 2017)

This paper presents a novel converter which can reduce the harmonics like the conventional multipulse converters with input three phase transformer. To reduce total harmonic distortion of input current and improve the weight and size of converters, it is suggested to use multi-pulse rectifiers with an electronic phase shift. The basic module is a 6-pulse rectifier on fully controlled switches with the reverse blocking ability. Switching frequency either coincides or is twice the power frequency. The proposed solutions allow refusing from the electromagnetic phase-shifting devices (power transformers or auto-transformers) and thereby significantly reduce the weight of the device. Unlike power factor correction systems with high-frequency modulation, the proposed converters are significantly different, as they have better electromagnetic compatibility and the virtual absence of dynamic switching losses of power switches.

An expanding mobile cellular network data transfer service offers cheaper wireless solutions for various data transfer needs. This paper presents an experimental testing of data transfer performance in 3G and 4G modes. The purpose of testing was to check the possibility of real-time and critical data transfer over the mobile cellular networks. The testing was performed in Riga in July and August 2016 using the most popular mobile service operators in Latvia: Tele2-LV, BITE-LV and LMT. The testing confirmed that the overload of Riga’s 4G networks causes serious service deterioration or even interruption. Riga’s 3G networks are more stable. However, 3G network service quality depends on a cell load. Lightly loaded 3G network meets real-time data transfer requirements of 100 ms one-way delay of the small packet traffic.

The study is devoted to the important issue of enhancing the circuitry and characteristics of power supplies for micro resistance welding machines. The aim of the research is to provide high quality input current and to increase the energy efficiency of the output pulse generator by means of improving the circuit topologies of the power supply main blocks. In study, the principle of constructing the power supply for micro resistance welding, which provides high values of output welding current and high accuracy of welding pulse formation, makes it possible to reduce energy losses, and provides high quality of consumed input current, is represented. The multiphase topology of the charger with power factor correction based on SEPIC converters is suggested as the most efficient for charging the supercapacitor storage module. The multicell topology of the supercapacitor energy storage with voltage equalizing is presented. The parameters of the converter cells are evaluated. The calculations of energy efficiency of the power supply’s input and output converters based on suggested topologies are carried out and verified in MATLAB Simulink. The power factor value greater than 99 % is derived.

Microgrids in island mode with high penetration of renewable energy sources in combination with gensets and battery storage systems need a control system for voltage and frequency. In this study the main goal is maximization of the energy feed-in by renewable sources. Therefore it is necessary to keep the State of Energy for the Battery Storage System in a range that the excess energy can be absorbed and used in a later period of the day. In this paper an approach for State of Charge scheduling based on load and generation prediction is described.

In this paper, an object recognition method and a pose estimation approach using stereo vision is presented. The proposed approach was used for position based visual servoing of a 6 DoF manipulator. The object detection and recognition method was designed with the purpose of increasing robustness. A RGB color-based object descriptor and an online correction method is proposed for object detection and recognition. Pose was estimated by using the depth information derived from stereo vision camera and an SVD based method. Transformation between the desired pose and object pose was calculated and later used for position based visual servoing. Experiments were carried out to verify the proposed approach for object recognition. The stereo camera was also tested to see whether the depth accuracy is adequate. The proposed object recognition method is invariant to scale, orientation and lighting condition which increases the level of robustness. The accuracy of stereo vision camera can reach 1 mm. The accuracy is adequate for tasks such as grasping and manipulation.

Medical information system (MIS) is at the heart of information technology (IT) implementation policies in healthcare systems around the world. Different architecture and application models of MIS are developed. Despite of obvious advantages and benefits, application of MIS in everyday practice is slow. On the background of analysis of the existing models of MIS in Georgia has been created a multi-user web-based approach. This article will present the architecture of the system and its application for cytology quality assurance programs. Five hundred Georgian language electronic medical records from the cervical screening activity illustrated by images were selected for quality assurance program. The primary goal of the MIS is patient management. However, the system can be used for quality assurance programs. The ideal of healthcare in the information age must be to create a situation where healthcare professionals spend more time creating knowledge from medical information and less time managing medical information. The application of easily available and adaptable technology and improvement of the infrastructure conditions is the basis for eHealth applications. The MIS is perspective and actual technology solution. It can be used for cytology quality assurance programs.