Volume 70 (2019): Issue 1 (February 2019)

Small quadrotors, or so-called nanoquads, are widely available, typically have small take-off mass (between 12–50 g), and a flight time of about 5–10 minutes. The aim of this article is the proposal of control and development of the basic infrastructure for controlling a swarm nanoquads from an external computer and obtaining measurements from an onboard sensor. Control of nanoquad attitude and position is proposed and control allocation problem is addressed. Additionally, landing and collision detection is implemented using external disturbance force estimation. Results of the proposed control methods are verified in 4 scenarios: hover flight, manual control, step response, and collision and landing detection.

This paper studies an improved fractional order parallel control structure (FOPCS) for enhancing the robustness in an industrial control loop having a first order process with dead time along with its tuning aspects. Since inclusion of fractional order calculus also increase the number of parameters to be determined for a particular control loops, tuning becomes an essential task. Four different tuning methods are considered to optimize the gains of parallel control structure (PCS) and FOPCS. Integral of time weighted absolute error for servo and regulatory problems along with overshoot value have been considered for performance evaluation. Extensive simulation studies including change in setpoint and mismatch in processmodel parameters have been carried out. On the basis of these studies, it was observed that FOPCS tuned by backtracking search algorithm, outperformed all other controllers in terms of considered performance measures.

For the expansion of in-home PLC networks, it is necessary to have a detailed knowledge of the PLC transmission channel properties. This contribution shortly discusses theoretical characteristics of the RC4 reference channel. A main part is focused on the network throughput and on the interphase PLC signal liaising presented in the RC4 reference channel for higher frequencies than 10 MHz. For evaluation of considered transmission parameters, experimental measurements related to various noise sources and to interactions between different phase conductors are realized in the real in-home PLC network.

A lumped-LC equivalent circuit to model a novel rectangular bracket shaped defected ground structure (DGS) is presented in this paper. The presented equivalent circuit can accurately predicate the frequency responses, in terms of the magnitude and phase responses of S parameters, of the studied DGS. The lumped LC parameters of the presented model are extracted based on a unit cell of the DGS. Further, the model is found to be applicable in microwave engineering, including microwave filter designs. Some design examples are presented and examined. The studied DGS based microwave filters characterize maximum passband flatness, sharp skirt between the passband and stopband and wide stopband. The studied equivalent circuit model can accurately predicate the frequency responses including the magnitude and phase of S parameters.

This paper addresses the issue concerning the design of battery-powered devices. In particular, it examines aspects affecting both short-term and long-term consumption. The primary focus of the paper is a low-power device powered by miniature batteries. From a broader perspective, it can also prove useful in designing devices powered by high-performance autonomous sources. The paper first identifies the basic design requirements with an emphasis placed on the key parameters of this specific category. The following chapters describe processing and circuit measures aimed at eliminating device consumption. The concluding part sums up the findings and presents some recommendations. The described methodology for the calculation of battery life has been experimentally validated and can be used to determine the battery lifespan in virtually any system.

The contribution presents the use of Genetic Algorithm for searching of the optimal parameters of a set of speed controllers of an isolated power-electricity island. Nine PI-controllers are designed. The cost function which is minimised using the Genetic Algorithm represents the integral of the control error area. Robustness aspects of the control design are considered as well.

The paper gives brief information about the status of the ANDREA code implementation at the Nuclear Regulatory Authority of Slovak republic and Slovak University of Technology in Bratislava. The first results of real fuel loading are compared to KASKAD results and a brief discussion on achieved progress and further plans is provided.

The paper presents the design of the class E current-driven rectifier, which is intended for operation in the wireless power transmission system, as well as the concept of selection of the rectifier parameters which allows the operation with high efficiency. The selection of the rectifier parameters was performed with a view to the use of the existing wireless power transmission (WPT) system. The procedure for selection of the rectifier parameters has been proposed to enable its optimal use in reference to the system parameters given already at the design stage, ie; load resistance and the coil magnetic coupling factor (distance between coils). In order to verify the correctness of the procedure for selection of the parameters, the numerical model of the system which consists of the class E resonance inverter, the air-core transformer and the designed E class rectifier system was developed in the LTspice environment. Simulation tests and analysis of the obtained calculation results were performed. Based on the simulation results, a prototype of the class E rectifier system which cooperates with the existing wireless power transmission system supplied from the class E inverter was developed. The obtained results of laboratory measurements demonstrated a high compliance with the simulation results, thus, confirming the correctness of the proposed design procedure and the high operating efficiency of the rectifier system.

The paper present a study of frequency shift of the reflection coefficient minimal absolute value dependence on antenna spacing in linear and circular arrays. The spacing of CB-band monopole antenna was in the range of 0.015 to 0.12 multiples of the antenna working wavelength. Number of elements in the antenna arrays ranged from two to four. Frequency dependence of minimal absolute value of the reflection coefficient was obtained by simulations and also experimentally confirmed in anechoic chamber. The research showed two facts. First, mutual impedance has the higher impact when antenna spacing is comparable with the reactive near field region. Second, circular antenna arrays are a better choice in applications for a small number of antennas with that spacing.

The article is devoted to the physical nature of geomagnetism, magnetic storms and methods of predicting their origin and deals with geomagnetic induced currents called GIC (Geomagnetically Induced Currents) and their effect on power transformers. A simplified, single-phase transmission system is described mathematically and its analysis was performed. Also the phenomenon of periodic semi-saturation of the magnetic circuit of the transformers resulting in current overload of the transformer windings, which can lead to thermal damage of the windings is explained. In addition, there is a significant deformation of the currents in the electrical system. The numerical solution of the system was verified by measurement on an electrical model.

Although the orthogonal systems are predominantly employed within modern technologies, some general systems can be found principally in nature. Progress in the field of nanotechnologies based on a condensed matter will reach its limit at a certain moment, which may be caused by material limits or limits of manufacturing technologies. This limitation will affect both approaches, the top-down as well as the bottom-up. Another way to obtain a nanostructure will be based purely on nature and its ability to grow, which requires a deep understanding of the world of biology. This natural approach is closely connected with a precise mathematical description which is necessary for employment of both the analytical and synthetic tools which are presently available within the frame of current technological methods. In this paper, we present an analysis of a model based on a spiral arrangement on a series of elements.

The metamagnetic properties of the manganese magnesium ferrites having the general formula Mn_0.7Mg_0.3Fe₂O₄ prepared by the standard ceramic technique have been studied. It is proposed that when a change of temperature at adequate magnetic field is applied in a Mn_0.7Mg_0.3Fe₂O₄ a magnetic phase transition will be generated, giving rise to an antiferromagnetic (AFM) state from ferrimagnetic (FM) phase. The critical transition field H_ac = 300 A/m was estimated for critical magnetization curve of transition from the metamagnetic behavior to FM behavior of sample. The FM to AFM transition in these ferrites is accompanied by a Néel type to Yafet-Kittel type transition and gradual spin ordering changes of the unit cell volume. The application of an external magnetic field to the low-temperatures AFM state causes the sample to reset to the original FM state.