Search Results (5)

This paper deals with the position detection of automated guided vehicles (AGVs) in dynamic resonant-inductive wireless power transfer (WPT) systems. A position detection is necessary to activate the correct transmitting coil. One of the simplest and most effective approaches for a position detection method is to use optical or magnetic position sensors for each coil. However, due to needing a high number of sensors, this technique is relatively expensive. Therefore, an AGV position detection technique based on a reduced number of optical or magnetic sensors (by a factor of two) is proposed. The proposed detection technique was verified experimentally by using a scaled-down prototype of the dynamic WPT system. The proposed approach can be easily implemented by uploading a specific program code to a microcontroller. The microcontroller with the code developed by us was used for processing data from AGV position detection sensors, activating a suitable transmitting coil and controlling an inverter of the dynamic WPT system. As shown by the experiments, due to the proposed approach for the position detection of AGVs and activation of transmitting coils, the number of the position detection sensors is reduced by a factor of two, leading to reductions in the overall cost and level of complexity of the dynamic WPT system without degrading its performance. Full article

The operation of wireless battery chargers at multiple switching frequencies may lead to a noticeable suppression of conducted and radiated electromagnetic interference (EMI) at the cost of decreased efficiency (mainly at lower load resistances) and increased peak and root mean square values of currents of power components of the wireless battery charger. Moreover, the reduction in conducted EMI is only moderate (<8.3 dB). Therefore, a novel approach based on modified resonant circuits and a modified control technique to obtain better reduction in the conducted and radiated EMI without significantly compromising other performance characteristics of the wireless battery charger is proposed and validated by using simulations and experiments. It is shown in this paper that the wireless charger operating at multiple switching frequencies with the proposed approach for the performance improvement has a more effective implementation of the four-switching frequency spread-spectrum technique with better conducted and radiated EMI reduction at all load resistances, lower values of peak and RMS currents at all load resistances, and higher efficiency in constant current mode and in the beginning of constant voltage mode (at lower values of the load resistances) than that of the conventional wireless charger operating at multiple switching frequencies. Full article

The multi-switching-frequency technique is one of the spread-spectrum techniques for suppression of conducted emissions generated by wireless battery chargers. Its advantage is a relatively easy implementation with a microcontroller. In this paper, an original thorough experimental study of the effect of the multi-switching-frequency-based spread spectrum technique parameters (e.g., combinations of number of pulses, frequency order, etc.) on the performance characteristics (conducted emissions levels, efficiency, etc.) of an inductive-resonant wireless battery charger with a closed loop control is presented. It is shown that combinations of a number of pulses and frequency order have a noticeable impact on the performance characteristics of the wireless chargers. The suppression of the conducted emissions can be improved significantly by using optimized parameters of the technique. Moreover, it is proved experimentally that a relatively inexpensive microcontroller with a transceiver can be used to implement both closed-loop control of the wireless charger and the multi-switching-frequency technique. Full article

The application of conventional spread spectrum techniques for conducted electromagnetic emission (EME) reduction in inductive-resonant wireless power transfer (WPT) systems may not reduce conducted EME enough due to specific frequency characteristics of the resonant systems and it can lead to some “adverse effects”, mainly in terms of decreased efficiency. Therefore, in this paper, an improved spread spectrum approach, multi-switching frequency and multi-duty cycle (MFMD) technique, is proposed. The proposed approach can give a considerably better conducted EME reduction along with a better efficiency than the conventional spread spectrum techniques based on a multi-switching frequency scheme. In the proposed approach, the inductive-resonant WPT system can operate at multiple switching frequencies (e.g., three different frequencies) and for a part of a control signal with a specific switching frequency, there is a specific duty cycle. The technique can be implemented in a simple way using an inexpensive 8-bit microcontroller. The effect of the MFMD scheme on the conducted EME and efficiency of the WPT system is studied in detail. The WPT system conducted EME and the efficiency are studied experimentally with a designed laboratory prototype. The performance characteristics of the WPT system with the MFMD scheme are compared to those with the multi-switching frequency scheme and without the spread spectrum. The WPT system with the proposed spread spectrum technique has a better performance than that with the conventional spread spectrum technique. Full article

Background. Mortality of infants and children younger than 5 years is a globally recognized and broad national welfare indicator. Scientific literature has data on the correlation of mortality indicators with macroeconomic indicators. It is important to study the associations between prevalence and mortality indicators and socioeconomic factors, since deaths from congenital anomalies account for approximately 25%–30% of all deaths in infancy. The aim of the study was to analyze the overall trend in mortality of infants and young children aged 0 to 4 years in relation to macroeconomic factors in Latvia and prevalence of congenital anomalies in newborns in relation to socioeconomic factors.
Material and Methods. The Newborns’ Register and Causes of Death Register were used as data sources; data on specific socioeconomic factors were retrieved from the Central Statistics Office.
Results. The results of the study show a strong correlation between mortality in children younger than 5 years and gross domestic product, as well as health budget in LVL per capita and the national unemployment level. The average decrease in infant mortality from congenital anomalies in Latvia was found to be 6.8 cases per 100 000 live births.
Conclusions. There is a strong correlation between child mortality and socioeconomic situation in the country. There is a need to analyze the data on child mortality in a transnational context on a regular basis and studying the correlations between child mortality indicators and socioeconomic indicators and health care management parameters. Full article