Pavol Lipovský

Measurement of small temporal and space variations of the magnetic field is required for many applications such as geophysics, space research, defense, industry, or security systems. In this paper, the focus is mainly paid on the vectorial sensors used in the unshielded environment. We proved that not only low noise, but also other parameters such as linearity and temperature stability are critical. High-temperature SQUID gradiometers are finding applications in the airborne scanning system as the magnetic field variations to be detected are small and the instruments cost is not prohibitive. Despite advances in the atomic magnetometers and small tunneling magnetoresistors, fluxgate sensors are usually the best solution for many applications. That is the reason why our research is focused on the development of fluxgate magnetometer. In the article many different applications of these sensors, involving for example mapping of the magnetic field using unmanned aerial vehicle (UAV), visualization of the magnetic field around the small UAV, spectrogram images created for the diagnostics of a ventilation system are presented. And based on the knowledge obtained during the research and application of magnetic sensors, the magnetometer application as a part of the developed security system is presented.

The aim of the ongoing research at our department in the field of magnetometers is the development of a compact modular magnetometric system operating with amorphous strips and microwires, used as a core. The motivation is in the long-term research, development, and testing of magnetometers with different types of control and processing electronics. The research has led over the years to the development of two types of fluxgate magnetometers. First of them is the VEMA magnetometer developed and realized by the researchers at the Faculty of Aeronautics in cooperation with the EDIS vvd. Company. The second one, considering the current trend of reducing dimensions and power consumption to increase the performance of sensor systems, considers the use of the microwires as the core of the magnetometer due to their small size, low power consumption, and good sensing properties. Both types of magnetometric systems work with the conversion of the magnetic field measurement to the time measurement. For the accurate time measurement in our experiments, the TDC7200 (time to digital converter) circuit designed for the LiDAR with the resolution of 55 ps has been used to measure the relaxation time and the time difference of our magnetometric systems. This article presents the results that were achieved during the experiments aimed at the testing of the accuracy and noise of the created devices.

The MM Science Journal, published since 2008, is a world respected scientific journal. The journal, published in English, is double peer reviewed and competitive in distributing knowledge among domestic and international academics and professionals. Full texts are available on-line on the journal...

In the design and development of measurement systems, such as magnetometric security systems or sophisticated devices such as satellites, it is necessary to consider the magnetic properties of all its parts and components, especially if it contains any magnetometric subsystem. The magnetic parameters of the materials are generally well described by the manufacturers in relation to their unprocessed raw state. However, their magnetic properties change as the subsequent machining or heat treatment is performed. These behavioral reactions of the material may lead to changes in its hysteresis during the magnetization cycles. This effect is necessary to consider, especially in the case of metallic ribbons, the magnetic characteristics of which are usually estimated by measurements performed on toroidal cores. Since the magnetic properties of a toroidal core differ from the magnetic properties of the preferably used open-ended samples, the corresponding measurement method needs to be used to determine its magnetic characteristics. Therefore, in the proposed article, the authors present a stray magnetic field-based method and measuring workstation intended to measure the magnetic hysteresis curves of the ferromagnetic open-ended samples used in the applications concerning the magnetometric systems and stabilization subsystems of small satellites. The physical background of the measurement method is described in detail, as well as the hardware and software used. The magnetic hysteresis curves of a small satellite electromagnetic actuator were measured as an example of an open-ended ferromagnetic component produced from amorphous ribbons, the permeability of which differs in comparison to manufacturer-stated permeability of raw amorphous material. The results are supplemented by measurements of the core characteristics of the used magnetometer probe, as well as by the characteristics of the semi-produced materials used for the production of both investigated cores. The primary advantage of the presented measurement method lies in the ability of design validation prior to the production of the final component and its assembly.

The specific professions of aviation personnel include the professions of the pilot and air traffic controller. These occupations are specific in that while performing their work, they must be able to simultaneously operate the devices in the handling area and in the pedipulation area, supplemented by acoustic sensations in the form of correspondence between flying and ground stations. The performance requirements of pilots and air traffic controllers place high demands on their health, psychological condition, attention, and concentration, due to being in constant pursuit of minimization of erroneous decisions, otherwise defined as the human factor in aviation. This article is focused on the development and testing of a technical device for measuring the relative error rate of students in multitasking tasks in preparation for employment. The main result is a designed technical device with hardware (HW) and software (SW) parts. An experimental method was used to measure the qualitative and quantitative performance indicators of the test subjects. The results of the experiment were observed and evaluated based on the analytical-synthetic method based on critical thinking. By comparing and abstracting the measured data, the reference values of the performance indicators of the tested subjects were determined. The selection of the final sample of subjects consisted of two phases. In the first phase, questionnaires were evaluated, and in the second phase, reaction time measurements during multitasking tasks using technical equipment were evaluated. Based on the measurements, an error ratio was defined, which could be graphically represented. The testing proved the full functionality of the designed technical equipment for these purposes in aviation education.

Charging stations (CHS) for electric vehicles (EV) are considered as sources of local magnetic fields (MF). The MF created by the CHS depends mainly on the actual charging power and topology of the electrical components inside the CHS. MF are in technical practice represented by the effective value of the magnetic flux density BRMS. However, the complex view has to consider the resulting MF vector, its components and the corresponding frequency values of the components at the measurement point and also their corresponding time development. The paper presents measurements of MF near the CHS that were performed with the VEMA-04 series magnetometer and 38 kW power drawn from the CHS. The parameters of the magnetic fields were evaluated in both the time and the frequency domains. The aim of this analysis is to point out that evaluating only simple effective value BRMS of MF is not sufficient.

This article deals with the design and creation of a tensometric measuring system to measure the parameters of an unmanned aerial vehicle (UAV) of the quadcopter type. The system was designed to measure the total UAV thrust and the thrust of its individual motors. The distribution of forces from the UAV motors and their transmission to the sensors was ensured by a specially designed construction, for which the mechanical stresses were simulated and analysed for different modes of the UAV flight. The thrust measurement was performed by four pairs of strain gauges. A measurement system designed in this way and the measured parameters of the UAV can be used for tuning the flight control algorithms applied in the autopilot.

The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, or generators. Identification of causalities of device failure processes with near magnetic field is one of the suitable NDT methods improving sustainability of systems. The measurements presented in the article were performed with the VEMA 04 fluxgate vector magnetometer with the DC-250 Hz bandwidth and 2 nT sensitivity. Postprocessing of the results was performed in the means of standard methods of discrete Fourier Transform, spectrogram creation and Wavelet Transform. The article presents data gathered during the measurement of a pair of extraction fans with power of 140 kW each and maximum revolutions up to 740 rev/min controlled by frequency converters and a single semi-Kaplan water power plant with 400 kW peak power at 1005 rev/min maximum generator speed. The measurements were performed before and after repairs of one of the ventilators in the ventilation system at 60% and 100% of maximal output power. The rotating magnetic fields of the fan electromotor stator, fan rotor revolutions, rotor slip frequency and ball-bearing frequencies were identified in frequency spectrums in the distance of 700 mm from fan electromotor axis in both cases. During the measurements on the semi-Kaplan turbine, the changes in states of mechanical and electrical components of the machine were monitored in the magnetic fields with increase of the power in the range of 0–95%, before and after phasing to the electrical grid. Standard processing methods, Discrete Fourier Transform, spectrograms and Discrete Wavelet Transform were used. In the spectrograms of the measured magnetic fields, the 1st–4th harmonics of the turbine shaft, generator shaft and also their side frequencies were identified. Significant changes of magnetic fields in time were identified in the area of 60–95% power. With the help of the Wavelet, transform intervals were identified where it is desirable to operate the turbine. The analyses of magnetic fields measurements performed on the power plant were compared with vibro-diagnostic principles.

Unmanned aerial vehicles (UAVs) are used nowadays in a wide range of applications, including monitoring, mapping, or surveying tasks, involving magnetic field mapping, mainly for geological and geophysical purposes. However, thanks to the integration of ultrasound-aided navigation used for indoor UAV flight planning and development in sensorics, the acquired magnetic field images can be further used, for example, to enhance indoor UAV navigation based on the physical quantities of the image or for the identification of risk areas in manufacturing or industrial halls, where workers can be exposed to high values of electromagnetic fields. The knowledge of the spatial distribution of magnetic fields can also provide valuable information from the perspective of the technical cleanliness. This paper presents results achieved with the original fluxgate magnetometer developed and specially modified for integration on the UAV. Since the magnetometer had a wider frequency range of measurement, up to 250 Hz, the DC (Direct Current) magnetic field and low frequency industrial components could be evaluated. From the obtained data, 3D magnetic field images using spline interpolation algorithms written in the Python programming language were created. The visualization of the measured magnetic field in the 3D plots offer an innovative view of the spatial distribution of the magnetic field in the area of interest.

The development of non-destructive methods for material testing and diagnostics has been, in the last few decades, focused mainly on optical, infrared, thermography, ultrasonic, acoustic or X-ray principles. This article deals with the possibility of adaptation of magnetic sensors for the diagnostics of aircraft structures. The developed sensors are based on the enhanced induction method, allowing contactless diagnostics of the material structure. In the role of the sensing element, amorphous magnetic microwires were used. Thanks to their dimensions, microwires can either be placed on the material surface or be embedded directly into the composite material without structural violations. In the article, the measurement principles of the developed microwire-based tensile stress sensors, together with the experimental measurements with the sensors originally tested in the aircraft wing, are presented.