Sensitive Axis Research Articles

What can be expected from GNSS tracking of satellite constellations for temporal gravity field model determination?

SUMMARYThe goal of this contribution is to investigate the expected improvement of temporal gravity field determination via a couple of high-low satellite-to-satellite tracking (HLSST) missions. The simulation system is firstly validated by determining monthly gravity field models within situ GRACE GPS tracking data. The general consistency between the retrieved solutions and those developed by other official agencies indicates the good performance of our software. A 5-yr full-scale simulation is then performed using the full error sources including all error components. Analysis of each error component indicates that orbit error is the main contributor to the overall HLSST-derived gravity field model error. The noise level of monthly solution is therefore expected to reduce 90 per cent in terms of RMSE over ocean when the orbit accuracy improves for a magnitude of one order. As for the current HLSST mission consisting of a current GNSS receiver and an accelerometer (10−10 and 10−9 m s–2 noise for sensitive and non-sensitive axes), it is expected to observe monthly (or weekly) gravity solution at the spatial resolution of about 1300 km (or 2000 km). As for satellite constellations, a significant improvement is expected by adding the second satellite with the inclination of 70° and the third satellite with the inclination of 50°. The noise reduction in terms of cumulative geoid height error is approximately 51 per cent (or 62 per cent) when the observations of two (or three) HLSST missions are used. Moreover, the accuracy of weekly solution is expected to improve 40–70 per cent (or 27–59 per cent) for three (or two) HLSST missions when compared to one HLSST mission. Due to the low financial costs, it is worthy to build a satellite constellation of HLSST missions to fill the possible gaps between the dedicated temporal gravity field detecting missions.

Eddy Current Probe With Integrated Tunnel Magnetoresistance Array Sensors for Tube Inspection

This article presents an eddy current probe with array tunnel magnetoresistance (TMR) sensors for inspection of the steam generator tube of the nuclear power plant. The TMR sensors are integrated on a circular printed circuit board (PCB) with the sensitive axis along the radius directions. The dimensions of each TMR sensor in the array are length (0.45 mm) $\times $ width (0.45 mm). Fine spatial resolution magnetic field imaging can be generated as the size of the sensor is small. The operating principle of the probe is based on Faraday’s law, where eddy current is induced in the tube wall by an excitation coil carrying ac current, and then, the disturbance of the eddy current is monitored in terms of the magnetic field measured by the TMR sensors. Thanks to the high sensitivity and fine spatial resolution of the TMR sensors, the probe is capable of detecting outer diameter (OD) defect with an effective size 0.127 mm $\times \,\, 0.436$ mm. Moreover, when the probe scans in a defect-free area, the variation of lift-off of the probe to the inner surface of the tube wall does not bring in noises, which is important for maintaining a high signal-to-noise ratio in the practical inspection. The operation principle of the probe was studied based on a finite-element method (FEM) model, and then, a prototype unit was developed and tested. The experimental results demonstrated the feasibility of the concept and validated that the probe has excellent ability to detect various defects.

Effects of intrauterine insulin-like growth factor-1 therapy for fetal growth restriction on adult metabolism and body composition are sex specific.

Fetal growth restriction (FGR) is associated with compromised growth and metabolic function throughout life. Intrauterine therapy of FGR with intra-amniotic insulin-like growth factor-1 (IGF1) enhances fetal growth and alters perinatal metabolism and growth in a sex-specific manner, but the adult effects are unknown. We investigated the effects of intra-amniotic IGF1 treatment of FGR on adult growth and body composition, adrenergic sensitivity, and glucose-insulin axis regulation. Placental embolization-induced FGR was treated with four weekly doses of 360 µg intra-amniotic IGF1 (FGRI) or saline (FGRS). Offspring were raised to adulthood (18 mo: FGRI, n = 12 females, 12 males; FGRS, n = 13 females, 10 males) alongside offspring from unembolized and untreated sheep (CON; n = 12 females, 21 males). FGRI females had increased relative lean mass compared with CON but not FGRS (P < 0.05; 70.6 ± 8.2% vs. 61.4 ± 8.2% vs. 67.6 ± 8.2%), decreased abdominal adipose compared with CON and FGRS (P < 0.05; 43.7 ± 1.2% vs. 49.3 ± 0.9% vs. 48.5 ± 1.0%), increased glucose utilization compared with FGRS but not CON (P < 0.05; 9.6 ± 1.0 vs. 6.0 ± 0.9 vs. 7.6 ± 0.9 mg·kg-1·min-1), and increased β-hydroxybutyric acid:nonesterified fatty acid ratio in response to adrenaline compared with CON and FGRS (P < 0.05; 3.9 ± 1.4 vs. 1.1 ± 1.4 vs. 1.8 ± 1.4). FGRS males were smaller and lighter compared with CON but not FGRI (P < 0.05; 86.8 ± 6.3 vs. 93.5 ± 6.1 vs. 90.7 ± 6.3 kg), with increased peak glucose concentration (10%) in response to a glucose load but few other differences. These effects of intra-amniotic IGF1 therapy on adult body composition, glucose-insulin axis function, and adrenergic sensitivity could indicate improved metabolic regulation during young adulthood in female FGR sheep.

Analysis of Electrostatic Driven Micromachined Gyroscope

Micromechanical gyroscopes are an important inertial instrument used to measure the angular or angular acceleration of an object. China’s research in this field lags behind that of developed countries in the West. The research on the core components of high-performance micromachined gyroscopes is still in its infancy. In this paper, a fully symmetrical multi-ring vibration structure electrostatically driven micromachined gyroscope is proposed, which is studied from the theoretical basis, working principle, structural design, performance simulation, processing technology and device testing, including the following electrostatic drive micro Testing of mechanical resonant devices. The test methods of several main MEMS resonant devices are analyzed. Based on vector network analyzer, vacuum cavity, transimpedance amplifier and other equipment, the frequency sweep test is performed on the device, and the resonant frequency of the drive shaft is 23686.2z. The resonant frequency of the sensitive axis is obtained. For the 23980 Hz based on the principle of electrostatic regulation, a 2.5V electrostatic adjustment voltage is applied to the device, and the frequency cracking of the two modes is reduced from 293.75 Hz to 6.25 Hz, which improves the performance of the device.

Critical measurement issues in the use of wire potentiometers for the structural health monitoring of slender structures: the case of the Duomo di Milano main spire

During the restoration of the Duomo di Milano main spire, a monitoring system has been set up in order to have an early detection of potential risks of the spire. A scaffolding for the restoration activities was mounted around the spire, and it had a section exposed to the wind actions much wider than the spire itself. Any possible contact between the spire and the scaffolding had to be prevented, even under the strongest winds expected in Milan, since the stability of the extremely slender marble spire could be compromised in case of contact. A safety gap between the two substructures was granted during the construction phase; however, the deflection of the spire could not be reliably predicted by numerical models. Therefore, it was decided to continuously monitor the actual gap value, together with other measurements, helping in a thorough understanding of the spire and scaffolding movements. The gap monitoring was measured by three-wire potentiometers, mounted to measure the relative position between the scaffolding and the spire in the section where the gap was the narrowest: the top balcony. This measurement was considered one of the most critical for the safety of the spire; therefore, every choice has been aimed at redundancy and safety. Moreover, any systematic effect has to be compensated for. A main issue related to the use of wire potentiometers is that these sensors estimate the amplitude of the displacement but does not provide any information on its direction. Since the horizontal displacement of slender structures can be in any direction, according to the wind and sun radiation conditions, the output of a wire potentiometer is also affected by displacements in the direction normal to its sensitivity axis, leading to a systematic effect in the measurements (cross-talk effect). This aspect hardly finds literature attention, but it can play a major role if the safety of the structure is monitored with wire potentiometers. This paper focuses on the estimation and compensation of this cross-talk effect, to provide reliable measurements in the monitoring of slender structures. Numerical and experimental validation of the proposed approach demonstrates the need to compensate for the cross-talk effects for a proper uncertainty estimation and then the validity of the proposed method.

Estimation of informative and background signals ratio in the registration of magnetic fields of surface defects by magnetic measuring transducers

Authors propose algorithms for quantitative ratio determining of informative and background components of the output signal of magnetic measuring transducers, used as a means of recording and measuring the parameters of locally distributed magnetic fields that occur over defective surface areas of the tested object in an applied permanent magnetic field. The method of separating the informative and background components based on the summation property and the deterministic nature of the distributions of the magnetic field intensity of the defect and the background magnetic field along the coordinate axis parallel to the controlled surface, and analysis of the topography of the distribution of magnetic field intensity is described. The approach to selection and experimental determination of estimated parameters characterizing the levels of informative and background signals is justified. Authors give the formulas for calculating the signal-to-background ratio based on the measured values of the estimated parameters applied to single magnet-static, differential magnet-static and differentiating magnetic measuring transducers taking into account the orientation direction (normal, tangential) of their sensitivity axis. The signal-to-background ratio calculation results are presented using an example of an analysis of the magnetic measuring transducers output signal when registering the distribution of the magnetic field intensity over the surface of a control sample with artificial defects of a given size. The comparative analysis of considered magnetic measuring transducers according to signal-to-background ratio is carried out. General recommendations to increase the value of the signal-to-background ratio parameter are given.

Calibration of the Thermal Model of an Inertial Measurement Unit with Three Angular Rate Sensors

The paper considers the techniques developed for calibration of an inertial measurement unit (IMU) containing three angular rate sensors (ARS). Calibration is performed on a two-axis calibration turntable with a thermal chamber. For instrumental errors of ARS measurements, a priori parametric model is introduced, which includes biases, scale factor errors, small angles of nonorthogonality of sensitivity axes, and coefficients of temperature dependence for all these measurement errors. The problem of determining parameters of the parametric model is reduced to the problem of optimal estimation of the linear dynamic system state vector. In this context, the measurement vector is the vector of a small rotation between the model orientation of the IMU (calculated from the ARS readings) and the model orientation of the turntable faceplate (calculated from the turntable measurements). The approach proposed for formalization of the calibration problem is a modification of the method for calibration of an IMU as a whole inseparable unit, using a single-axis turntable with the horizontal axis of rotation, previously developed in the Laboratory of Control and Navigation of Lomonosov Moscow State University. The calibration experiment consists in a sequence of horizontal rotations about each of the ARS sensitivity axes. The results of numerical simulation and covariance analysis are considered.

Low-Cost and High-Efficiency Method for Detecting Vertical Bends of Subsea Pipelines

Subsea pipelines often bend upward due to vertical buckling or downward due to spanning and seabed settling. Typically, harsh environments and the difficulty of accessing underwater pipelines make the inspection and monitoring of subsea pipeline bends a challenging task. This paper demonstrates a low-cost, high-efficiency, and quasi-real-time method for detecting the vertical bends of subsea pipelines by using an in-pipe spherical detector (SD) with rolling features and a low blockage risk. When the SD rolls forward inside a bent pipeline, its rolling speed will change as it moves uphill and downhill, which can be indicated by the centripetal acceleration—the DC component of the recorded rolling acceleration signals. To achieve a high bend detection performance, the mass of the SD should be distributed in a centered disc area to make the SD capable of stably rolling around one of the sensitive axes of the accelerometer, and the accelerometer should be kept as far from the rotation axis as possible. It is experimentally demonstrated that a convex/concave DC component indicates that the pipe is bent downward/upward, and the bend detection resolution can reach 1 cm for a 12 m pipeline.

Upgrade of the Argentine Islands INTERMAGNET observatory at Akademik Vernadsky station, Antarctica

The article describes the main features of upgrading the magnetometric complex based on the LEMI-025 variometer in January-April 2019 at the geomagnetic observatory (code AIA) of the Ukrainian Antarctic Akademik Vernadsky station. The observatory’s old magnetometric complex consisted of two LEMI-008 (No. 02 and No. 16) variometers and one POS-1 scalar magnetometer. The measurements of LEMI-008 and POS-1 were not mutually synchronized and this was one of the main problem. Every measuring instrument taken individually as a component of the whole magnetometric complex had good individual properties. However, in general, the complex as an entire system had reduced performance, mainly due to the lack of mutual synchronization of measurements. Some preliminary test results are also presented. Main objective. One of the main task of upgrading the AIA observatory was to install a new variometer that is compatible with the requirements of the 1-second INTERMAGNET data standard. For two decades, old LEMI-008 variometers at Akademik Vernadsky station have shown high baseline stability, which meets INTERMAGNET requirements. Unfortunately, the noise characteristics of old variometers, the accuracy of synchronization with UTC, and the resolution do not longer meet the current INTERMAGNET requirements for devices that produce 1-second data. Measurements of LEMI-008 variometers and POS-1 scalar magnetometer were not mutually&nbsp; synchronized. Due to lack of reliable mutual synchronization, the differences between the field vector modules, calculated indirectly from the variometer measurements and measured directly with the scalar magnetometer, varied and could be unreliable. With strong geomagnetic disturbances, this reduced the overall accuracy of the magnetometric complex as an integral measuring system, although the complex consisted of high-precision instruments. Only one of LEMI-008 variometers was equipped with GPS synchronization. This made data processing difficult. Therefore, one of the crucial upgrading tasks was creation of a system for mutual synchronization of measurements provided by the variometer LEMI-025 and the scalar magnetometer POS-1 with an accuracy of approximately 0.1 s (but not worse than 1 s) using control computer. Methods. The problem of mutual synchronization of the measurements of the LEMI-025 variometer and the POS-1 scalar magnetometer (at the stage of upgrading the magnetometric complex as a whole system) was solved using a control computer by periodical adjusting the POS-1 clock and starting its measurement cycles with a given timing advance. New data arrays were obtained while the LEMI-025 magnetometer was operated in test mode. Using the Bartlett’s method and spectral harmonics averaging, the noise level of the magnetometers during a geomagnetically quiet day was estimated. The results of absolute measurements of the geomagnetic field components, regularly carried out in the observatory by two methods, were analyzed and the baselines values of the LEMI-025 magnetometer were estimated. The comparative analysis of the records of the Earth magnetic field intensity, obtained by direct measurements with a scalar magnetometer POS-1 and calculated from the baseline-adjusted components of the LEMI-025 variometer, was performed. Using the obtained baseline values and the total field difference signals the high calibration accuracy of the new variometer was confirmed and the orientation errors of its sensitivity axes in the geographical coordinate frame were estimated. Conclusions. Our preliminary results confirm that the characteristics of new LEMI-025 variometer meet the INTERMAGNET requirements. The orientation errors of LEMI-025 sensor do not exceed 5 arc minutes. The base line is quite stable. All its components have dispersion within ±2 nT, without pronounced temporal drift. The test results of LEMI-025 variometer showed that the characteristics of all magnetometric instruments in the measuring pavilion of the AIA observatory should be mutually agreed in terms of electromagnetic compatibility.

The results of modelling of a micromechanical accelerometer

This theses the linear acceleration sensor design with three axis of sensitivity is researched. Parameterized geometry and finite element model for modal analysis are developed in the ANSYS program. Behavioral description of the study design is developed with language VHDL-AMS to simulate the sensor operation under the influence of linear acceleration along three axis of sensitivity. On the basis of research results three-axis device sensitivity, cross-sensitivity, duration transients are specified. As part of the work the experimental sensor prototypes are fabricated.

Selected Aging Effects in Triaxial MEMS Accelerometers

Natural aging of commercial triaxial low-g MEMS accelerometers, manufactured by surface micromachining, was evaluated in terms of changes of their offset voltages and scale factors, assigned to each sensitive axis. Two pieces of two models of triaxial accelerometers (ADXL 330 and ADXL 327 by Analog Devices Inc.) with analog outputs were tested within a period of ca. 4.5 years. Two different computer-controlled test rigs were used for performing relevant experimental studies, employing tilt angles as the reference source. Methodology of determining the proposed indicators of aging was based on cyclic repetition of the calibration procedure for each accelerometer. Changes of the output signals of the tested accelerometers were observed, resulting in respective indication errors of ca. 0.8% or even 2.2% while related to determining tilt. Since the accelerometers were operated under mild conditions while tested, much bigger errors are to be expected in the case of harsh conditions. Both pieces of ADXL 330 accelerometers ceased to operate properly within the testing period, approximately at the same time, for no apparent reason; thus, it is recommended to introduce redundancy in relevant reliable measuring circuits by doubling the number of the applied accelerometers.

Omnidirectional low frequency energy harvester for wearable applications

We present an omnidirectional energy harvester with lowest resonance mode at 14.85 Hz. The geometry is designed as a spiral shaped, 500 μm thick PZT lateral bimorph to achieve a low resonance frequency while minimizing the area required. The resonance modes and frequencies of the energy harvester are investigated with COMSOL eigenfrequency study. The resonance modes of translation in x, y, z, and rotation around x, y, and z have resonance frequencies at 23.4, 22.9, 14.9, 34.0, 33.6, and 25.5 Hz, respectively. Multiple resonance modes widen bandwidth and enable harvesting energy from all directions. The energy harvester is mounted inside a 3D printed package that can be worn on a human wrist. The design of the package mimics the approximate size of a typical smartwatch, and the motion from walking is along the most sensitive axes of the harvester. It produces an output of 900 mV peak-to-peak for an optimum load of 1.8 megaohms and provided 0.45 microwatts. The output voltage is high enough to charge a battery through commercial diodes.

Improving the efficiency of the search methods of the refused sensor in an excessive angular speed meters

In control systems of launch vehicles, satellites, it is important to ensure the operability of the system in the presence of failures. In the units of angular velocity or acceleration sensors, redundancy can be used, that is, the installation of sensors in the amount of four to six, the sensitivity axis of any three of them are not coplanar. In addition to reliability improvement the redundant meters improve the accuracy characteristics of systems. To determine the failed sensors, special algorithms which influence the efficiency of the failed sensor search have been developed. The following search methods are considered: the method of the failed sensor determining by the minimum of average values of the residual modules; method for the failed sensor determining by the minimum of mean values of squared residuals method for the failed sensor determining by the minimum of the squares deviations average values of the angular velocity components; method for the failed determining sensor by the maximum modulus of the difference of the calculated and measured data. The probabilities of determining failures, false failures, and undetected failures are given. The methods of finding a failed sensor in the redundant angular velocity meters given in the article take into account the presence of errors in the transmittance of sensors.

Techniques for vibration resistance increase of quartz pendulum accelerometer using digital feedback amplifier

Subject of Research. The paper considers approaches of vibration resistance increasing for quartz pendulum accelerometer with digital feedback amplifier and without further development of measuring element design or application of damping measures. Method. The proposed methods are implemented algorithmically by means of the control program of the digital amplifier controller and are based on the extension of the device bandwidth, the correction of the regulating coefficients during the accelerometer operation, and the introduction of an additional control channel to the feedback loop. Main Results. The proposed methods were studied experimentally on a prototype quartz pendulum accelerometer with a digital feedback amplifier and a measuring range of ±50 g. The studies were carried out under the effects of vibration actions: broadband random vibration in the frequency range from 20 to 2000 Hz, (RMS deviation of the vibration acceleration amplitude of 8 g) and sinusoidal vibration in the frequency range from 20 to 2000 Hz (vibration acceleration amplitude of 10 g) along the sensitivity axis. The efficiency of the methods was estimated by the value of device vibration error — the difference between the averaged value of the device readings before vibration and the averaged value of the readings during the period of vibration. It was experimentally established that the best solution is to combine a wide bandwidth of the device with an additional control channel in the feedback loop, that reduces the accelerometer vibration error by an order of magnitude. Practical Relevance. The proposed methods increase the vibration resistance of a quartz pendulum accelerometer by applying original algorithms in the digital amplifier controller program, that makes it possible to put to use such accelerometers in objects susceptible to vibration while eliminating the need to introduce physical design modifications or additional damping measures.

The sialoglycan-Siglec-E checkpoint axis in dexamethasone-induced immune subversion in glioma-microglia transwell co-culture system.

Dexamethasone (Dex) is considered as the main steroid routinely used in the standard therapy of brain tumor-induced edema. Strong immunosuppressive effects of Dex on effector systems of the immune system affect the patients' antitumor immunity and may thereby worsen the prognosis. Siglecs and their interacting sialoglycans have been described as a novel glyco-immune checkpoint axis that promotes cancer immune evasion. Despite the aberrant glycosylation in cancer is described, mechanisms involved in regulation of immune checkpoints in gliomas are not fully understood. The aim of this study was to investigate the effect of Dex on the Siglec-sialic acid interplay and determine its significance in immune inversion in monocultured and co-cultured microglia and glioma cells. Both monocultured and co-cultured in transwell system embryonic stem cell-derived microglia (ESdM) and glioma GL261 cells were exposed to Dex. Cell viability, immune inversion markers, and interaction between sialic acid and Siglec-E were detected by flow cytometry. Cell invasion was analyzed by scratch-wound migration assay using inverted phase-contrast microscopy. Exposure to Dex led to significant changes in IL-1β, IL-10, Iba-1, and Siglec-E in co-cultured microglia compared to naïve or monocultured cells. These alterations were accompanied by increased α2.8-sialylation and Siglec-E fusion protein binding to co-cultured glioma cell membranes. This study suggests that the interplay between sialic acids and Siglecs is a sensitive immune checkpoint axis and may be crucial for Dex-induced dampening of antitumor immunity. The targeting of sialic acid-Siglec glyco-immune checkpoint can be a novel therapeutic method in glioma therapy.

Design and Development of a Differential Current Probe With High Misalignment Tolerance

A modified, simple, and reliable core-less differential Hall-Effect current probe is presented in this paper. The proposed probe has a high tolerance to typical misalignments of the conductor position that otherwise affects the accuracy. The conventional anti-differential probe has two magnetic sensing elements, with an axis of sensitivity. The current carrying conductor is kept between these elements, and the output is a function of the gap between the conductor and the sensing element. In practice, it is very difficult to ensure the correct positioning of the conductor, during the installation and throughout the operation, such that the gap is maintained the same for both the sensing elements. A recent sensor configuration presented partially corrects for the associated errors. This paper presents a modified probe with sensing elements that are sensitive to two directions that are in quadrature. In the modified probe, the current is computed in a special manner that provides accurate output even if the conductor is moved away from the ideal position in any direction. This ensures high reliability as the output significantly reduces the effect of positional error owing to mechanical movement, deformation, and vibration of the conductor in vertical and horizontal directions. A prototype of the proposed probe has been developed in the laboratory using commercially available Hall-Effect sensors and tested for a wide range of vertical and horizontal misalignments. The maximum error noted from the prototype probe showed more than 20 times improvement compared to the conventional probe when the same misalignment, mentioned above, was introduced to both the probes. The results from the experimental studies conducted using the developed probe proved the practicality.

Model of output characteristics of giant magnetoresistance (GMR) multilayer sensor**Project supported by the National Key Research and Development Program of China (Grant No. 2018YFF01010701), the Natural Science Foundation of Zhejiang Province, China (Grant No. LQ17F010004), and the National Natural Science Foundation of China (Grant No. 61741506).

In this paper, the giant magnetoresistance (GMR) multilayer sensor is fabricated with a Wheatstone bridge, and it exhibits excellent performance with a sensitivity of 2.8349 mV/(V/Oe) () and a saturation field of 26 Oe along the sensitive axis. The GMR sensor is also characterized in a high magnetic field. The sensitivity decreases from 2.8349 mV/(V/Oe) at an angle of 0° to 0.0175 mV/(V/Oe) at an angle of 90°. Then, the sensor is placed in a series of rotating magnetic fields. We propose a model to express the output characteristics of the GMR multilayer sensor. The transfer curves of the sensor can be shown as two exactly symmetrical circles with an increasing radius when the magnetic field increases. The experimental results are consistent with the simulation results of the model. The advantage of this model is that it is simpler and more intuitive.

COMPLEX OF SPECIALIZED STAND EQUIPMENT FOR MONITORING THE CHARACTERISTICS OF LOW FREQUENCY ACCELEROMETERS

При вирішенні задач дослідження вібростійкості будівель, споруд та малих інженерних конструкцій, основним елементом системи контролю, що забезпечує проведення таких досліджень, є віброперетворювачі, від достовірності показів яких суттєво залежить працездатність системи в цілому. Перевірка функціювання та визначення параметрів таких приладів здійснюється за допомогою вібростендів. З урахуванням особливостей низькочастотних акселерометрів, для перевірки їх функціонального стану необхідні випробувальні стенди з діапазоном переміщень до 200 мм і частотним діапазоном у межах 0.1 – 10 Гц, такі стенди, зазвичай, мають великі розміри і вимагають стаціонарного встановлення в лабораторіях. Після транспортування на місце проведення випробувань, необхідно також провести перевірку працездатності віброперетворювачів і їх первинне калібрування. Але при перевірці портативних віброперетворювачів, особливо в польових умовах, виникає низка проблем, пов’язаних і з заданням необхідних параметрів вібрації, і з необхідністю проводити дослідження віброперетворювачів масою 5 -10 кілограмів, що також потребує наявності випробувальних стендів, які частіше відсутні. В роботі представлені два розроблені стенди для перевірки працездатності та контролю характеристик низькочастотних віброперетворювачів. Перший з них – двокомпонентний, переносний, автономний. Може бути використаний в польових умовах за відсутності мережевого електроживлення в місці проведення досліджень. Конструкція стенда дозволяє проводити перевірку акселерометрів як з горизонтальною, так і вертикальною осями чутливості. Особливістю стенду є, з одного боку його портативність, а з іншого – можливість перевірки датчиків масою до 7 кілограмів в частотному діапазоні до 10 Гц. Другий стенд – лабораторний маятниковий великих переміщень. Може бути використаний для визначення параметрів вібродатчиків з динамічним діапазоном переміщень до 200 мм, масою до 20 кілограмів, в частотному діапазоні до 2 Гц. Обидва стенди обладнані універсальним інформаційно-вимірювальним модулем, що забезпечує збір, візуалізацію і первинний аналіз отриманих даних та їх збереження на ПК, для чого було розроблене спеціальне програмне забезпечення у середовищі NI LabVIEW. Для універсального автономного стенду реалізована функція керування частотою вібрації платформи.

Compounded Calibration Based on FNN and Attitude Estimation Method Using Intelligent Filtering for Low Cost MEMS Sensor Application

Micro electro mechanical system (MEMS) inertial sensors have advantages, including small size and low power consumption. The performances of Micro Inertial measurement unit (IMU), which is composed of MEMS inertial sensors, degrade, and error, will become larger in high dynamic environment. In order to solve the problem, a novel combined calibration method for compensating the deterministic error of MEMS sensors is proposed. Considering the rotation of different sensitive axes in high dynamic and low dynamic environment, the compounded calibration based on fuzzy neural network (FNN) is adopted to identify the coupling coefficients to eliminate the adverse coupling effects between different rotation axes. Furthermore, the self-developed Micro IMU and magnetometer are applied in attitude estimation system. Considering the large attitude error occurred in most cases, the approach utilizing the estimation of error quaternion vector could avoid the calculation error due to inaccurate modeling in the skew symmetric matrix that comprises attitude error vector components. The intelligent Kalman filter (IKF) based on complexity state equation of error quaternion is designed to improve the performance by adjusting the parameters of filter on line. The experimental results show that the proposed approach could have a higher level of stability and accuracy in comparison to other attitude estimation algorithms.

A Three-Component Mathematical Model of a Single-Axis Accelerometer for Measuring Pitch and Roll Angles

We consider measurements of pitch and roll angles using compensation pendulum accelerometers with closed feedback. A three-component mathematical model of a single-axis accelerometer has been developed as a means of measuring pitch and roll angles. The model takes into account the effect of acceleration applied perpendicular to the axis of sensitivity of the accelerometer. The error of the mathematical model is investigated. Methods for accelerometer calibration and a method for taking into account the effect of temperature on its readings using a three-component mathematical model are proposed. The mathematical model is verified using accelerometer calibration results.