Sensitive Axis Research Articles

A calibration method for rotary optical encoder temperature error in a rotational inertial navigation system

A rotary optical encoder is an important component in a rotational inertial navigation system (RINS). It is used to form a closed-loop motor control system and calculate the system attitude. The system performance will be affected by the encoder’s error. Ín addition to the installation errors, the working temperature variants can lead to encoder error. Therefore, in this paper we propose a method to calibrate and compensate the temperature errors of rotary optical encoders. First, an independent testing mechanism with position limitation and a rotatable platform is designed and produced to verify the temperature influence on encoders. Then, the temperature error of the rotary optical encoder used in RINS is calculated by a gyroscope whose sensitive axis is parallel to the same motor axis. The method is verified by a self-researched single-axis RINS. According to the experimental results, the measurement accuracy is increased by more than 47.9% compared to the traditional method.

Tilt Sensor with Recalibration Feature Based on MEMS Accelerometer.

The main errors of MEMS accelerometers are misalignments of their sensitivity axes, thermal and long-term drifts, imprecise factory calibration, and aging phenomena. In order to reduce these errors, a two-axial tilt sensor comprising a triaxial MEMS accelerometer, an aligning unit, and solid cubic housing was built. By means of the aligning unit it was possible to align the orientation of the accelerometer sensitive axes with respect to the housing with an accuracy of 0.03°. Owing to the housing, the sensor could be easily and quickly recalibrated, and thus errors such as thermal and long-term drifts as well as effects of aging were eliminated. Moreover, errors due to local and temporal variations of the gravitational acceleration can be compensated for. Procedures for calibrating and aligning the accelerometer are described. Values of thermal and long-term drifts of the tested sensor, resulting in tilt errors of even 0.4°, are presented. Application of the sensor for monitoring elevated loads is discussed.

Исследование функционирования чувствительного элемента микромеханического акселерометра сэндвич-конструкции емкостного типа в условиях паразитных воз-действий по нерабочим осям и случайной вибрации

Various types of parasitic influences must be considered at the stage of designing sensitive element of a micromechanical capacitive accelerometer (MMA) and the whole MMA con-struction, and throughout its lifecycle stages, to ensure consistent performance and parameter stability of MMA. Due regard to actual operating conditions is a primary consideration for de-signers. In this work, the influence of random vibration on the functioning of a 2-electrode sensi-tive element of an MMA with a sandwich construction using the principle of operation based on a change in the relative dielectric constant of a capacitor dielectric under acceleration was inves-tigated. In the structure of the investigated sensitive element with one axis of sensitivity, the inertial mass is suspended on folded springs and is located between two fixed electrodes. Using the Ansys program, the deformations of the inertial mass of the sensitive element and the change in the capacity in the sensitive element were calculated, which occur when it is exposed to acceleration up to 5 g along the working axis and up to 50 g along the non-working axes and random vibration along the working axis X and along the non-working axes Y and Z. The random vibration affecting the sensitive element had a profile, the frequency of which was 20 Hz at 0.01 g2 / Hz, the frequency from 80 to 350 Hz at 0.04 g2 / Hz, 2000 Hz at 0.01 g2 / Hz. The changes in the capacity in the sensitive element of MMA under the influence of random vibration on it were calculated. Results have been obtained that confirm the performance of the sensitive element of MMA under conditions of significant impacts along non-working axes. The investigated sensitive element model requires further refinement to be used under conditions of exposure to random vibration.

NOX4 sensitive CYGB-HMGB2 axis regulates DNA damage repair pathways and gene programs in the vasculature

NOX4 sensitive CYGB-HMGB2 axis regulates DNA damage repair pathways and gene programs in the vasculature

A study of the efficiency of the magnetic compass correction system

In sailing conditions under the rolling, dynamic compass errors may appear due to the influence of the redistributed magnetic masses of the ship, as well as of centripetal and tangential accelerations. The influence of these errors can be compensated by introducing a correction system into the measuring circuit of the compass, which uses one gyroscopic angular rate sensor. The correction method is based on the use of a gyroscopic angular rate sensor with a vertical axis of sensitivity in the circuit. The generated signal is the difference between the output reading of the magnetic compass and the integrated signal of the angular rate sensor, which is insensitive to the action of translational acceleration and redistributed magnetic masses during the ship’s heel. The resulting difference will contain the compass error from the rolling effect, further compensated for in the compass output signal. The choice of the parameters of the dynamic links of the circuit for the implementation of the correction system and the study of its operation was carried out by simulation method using the proposed analytical expression for the error of the magnetic compass from the rolling effect. Comparison of the simulation results with the results of experimental studies of the compass was carried out using a specialized stand that simulates the yaw of a ship and allows one to change the value of the vector of the Earth’s magnetic field, when exposed to the magnetic system of the compass. Experimental studies of the compass showed that the pitching error correction coefficient is in the range 0.16-0.48 (average value is 0.35), when the object’s angular oscillation periods change from 6 to 28 s, which characterizes the degree of pitching suppression, and when modeling, the average value of the coefficient is 0.21. The underestimation of the correction factor in modeling is due to the lack of taking into account the dynamic properties of the compass rose and depends on the ratio of the periods of natural oscillations of the compass and the periods of disturbing influences. The results confirmed the high efficiency of the considered compass correction system and the required quality of the developed specialized stand for evaluating its work. The results of the study can be used in the development of modern magnetic compasses to ensure high accuracy of directional guidance through the use of the proposed correction system.

Co-Registration Error Analysis and Array Calibration for OPM-MEG System

Optically pumped magnetometer (OPM-magneto- encephalography (MEG) source localization necessitates precise co-registration of the MRI and MEG sensor array. The co-registration error decreases the spatial resolution of MEG source estimation. To clarify and reduce the co-registration error, the data acquisition and co-registration processes are theoretically modeled and analyzed in this article. The results show that the error caused by the substituting of the designed sensor array model for the manufactured array in data acquisition is widely ignored. The amount of data used for transformation calculation is a decisive factor for the transformation accuracy. The error sources of co-registration in the OPM-MEG system are analyzed. The position error and orientation error of the sensitive axis of the sensor are two main error sources. In the range of 250 mm, the calibration experiment achieves a position accuracy of 2.5 mm and an orientation accuracy of 2° of the sensor sensitive axis. Real-time acquisition and correction of sensor position and orientation in the OPM-MEG array can be realized by optimizing the configuration of calibration scheme, and the accuracy of the OPM-MEG source localization can be improved.

Assessing the quality of a network of vector-field sensors

An experiment consisting of a network of sensors can endow several advantages over an experiment with a single sensor: improved sensitivity, error corrections, spatial resolution, etc. However, there is often a question of how to optimally set up the network to yield the best results. Here, we consider a network of devices that measure a vector field along a given axis; namely for magnetometers in the Global Network of Optical Magnetometers for Exotic physics searches (GNOME). We quantify how well the network is arranged, explore characteristics and examples of ideal networks, and characterize the optimal configuration for GNOME. We find that by re-orienting the sensitive axes of existing magnetometers, the sensitivity of the network can be improved relative to the past science runs.

Evaluation of permissible amplitudes of external impact on free-of-platform inertial navigation systems

In modern aerospace technology, strapdown inertial navigation systems (SINS) are widely used, using fiber-optic (FOG) or ring laser (CLG) gyroscopes. During the operation of such systems, the sensitivity axes are rotated relative to the basic coordinate system. The resulting angles between the axes of the base coordinate system and the axes of sensitivity of the navigation system (non-orthogonality) are one of the factors leading to an increase in the measurement errors of the device, which affects the measurement accuracy. During operation, the system is affected by vibrations of various nature, the impact of which can contribute to the appearance of non-orthogonality. The purpose of this work is to determine the maximum permissible vibration amplitudes affecting the SINS body according to the permissible values ​​of the deviation of the FOG sensitivity axes for two variants of the SINS layout. An approach to determining the permissible amplitudes of an external harmonic impact on the unit of a strapdown inertial navigation system based on fiber-optic or ring laser gyroscopes is considered. A design scheme, mathematical and finite element models for calculating natural frequencies and forced oscillations of a strapdown inertial navigation system unit have been developed. In various frequency ranges, numerical calculations have determined the boundary values ​​of the amplitudes of the external harmonic impact on the base of specific configurations of the SINS assembly. It has been established that dangerous states take place in the region of the 1st natural frequency of the system, as well as near higher frequencies. Comparison of the results for design options 1 and 2 allows us to conclude that in order to weaken the effect of vibrations on the accuracy of the SINS unit, it is advisable that the lowest natural vibration frequencies for the SINS assembly be as high as possible (more than 1000 Hz).
 Key words: vibration; fiber optic gyroscope; strapdown inertial navigation system; finite element method; natural frequencies and modes of vibration.

Verification of the method of finding a faulty sensor in reduced meters

The reliability of the method for determining a failed sensor in a redundant angular velocity meter (AVM) by means of its experimental verification is considered. The mutual non-orthogonal arrangement of six axes of sensor sensitivity has been optimized to reduce the instrumental errors of each sensitive element and ensure the equality of their contribution. Provides approximately the same sensitivity to the level of error in case of failure. One of the six experimentally obtained sensor signals contains an error that exceeds the specified permissible limit. The algorithm for searching for a sensor is checked, the error of which exceeds the specified one, and which, for this reason, is considered faulty.

Vibratory Gyroscope Scale Factor and Bias on-Run Self-calibration

А new method for on-run periodic scale factor and bias self-calibration of vibratory gyroscopes in an inertial measurement unit with a redundant number of sensors is proposed. Self-calibration uses predefined virtual positive and negative angle rates to calibrate the SF, and the bias of the gyroscope that is in calibration mode, while the others, at least three gyroscopes of an inertial measurement unit, whose sensitivity axes do not lie in the same plane, operate in the measurement mode to measure the real angle rate of a vehicle. The projection of the current angle rate onto the sensitivity axis of the gyroscope being calibrated is computed from the results of measuring the full angle rate vector by the other three gyroscopes, creating conditions for the calibration procedure. In contrast to known methods, such as single-axis or multi-axis rotation of an inertial measurement unit and vibration modes reversal, the proposed method does not use mechanical rotation, which requires additional devices, and does not require a reorientation of the vibrating wave, which entails the need to align the parameters of the two measuring channels. The scale factor and bias calibration procedure using this method is the same for any gyroscope of an inertial measurement unit and can be applied to several gyroscopes at the same time. Therefore, the proposed method has great potential for an application not only for small-sized 4-gyro inertial measurement unit based on vibratory gyroscopes but also for multi-gyro inertial measurement unit based on micro-electro-mechanical gyroscopes. Experimentally shown that using the proposed method a gyro requirements mitigation coefficient can be substantially increased and can provide high accuracy for autonomous navigation systems based on low-cost, small-sized, and micro-electro-mechanical gyroscopes.

Design and Simulation of the Two-Axis Micromachined Angular Rate Sensor

Micromechanical inertia sensors - accelerometers, gyroscopes, multisensor modules and systems based on them - are widely used in navigation, for compensation of other instruments (accelerometers, inclinometers) or stabilization (gyroscopes). The paper presents the designed construction of a MEMS angular rate sensor with two sensitivity axes, topology of gyroscope is presented; modal and static analysis is performed using ANSYS CAD; simulation results of micromechanical gyroscope operation under the action of angular velocities using VHDL-AMS are presented.

Non-sensitive axis feedback control of test mass in full-maglev vertical superconducting gravity instruments

Non-sensitive axis feedback control is crucial for cross-coupling noise suppression in the application of full-maglev vertical superconducting gravity instruments. This study proposes the non-sensitive axis feedback control of a test mass in a custom-made full-maglev vertical superconducting accelerometer. In the feedback system, special superconducting circuits are designed to decouple and detect multiple degree-of-freedom motions of the test mass. The decoupled motion signals are then passed through a PID controller and fed back to the side-wall coils to control the test mass. The displacement of the test mass is controlled within ± 2 nm and is reduced by approximately one order of magnitude in a laboratory environment. Accordingly, the noise level of the vertical superconducting accelerometer in the sensitive axis is reduced by a factor of 4–6 @ 0.03–0.1 Hz.

Quantitative analysis of position setting effect on magnetohydrodynamics angular vibration sensor response

Magnetohydrodynamics angular vibration sensor (MHD AVS) has been widely used in stabilization servo subsystem to measure angular motions with extremely low noise in relatively broad range of bandwidth. In practical, MHD AVS is usually affixed to the housing equipment with its angular axis of sensitivity possibly not coincident with the rotation axis. This work presents quantitative analysis of the position setting effect on MHD AVS performance including frequency response, linearity and measurement noise. A theoretical model that correlates physical and positional parameters with the sensor’s output is established on the basis of Navier-Stokes equation in the non-inertial system. Finite element analysis (FEA) is conducted to investigate mechanical resonant characteristics of the current sensor. The interaction between three-dimensional unsteady flow and non-uniform radial magnetic field, as well as error sources varying with frequency and positional parameters within MHD AVS are analyzed through numerical simulations. Experiments are finally carried out to verify the established theoretical model and numerical simulations under a variety of conditions. Conclusions drawn from the theoretical model, numerical simulations and experiments are found to be basically consistent, which indicate that MHD AVS is nearly no sense to the eccentricity and is essentially cosine to the output of pure rotation when its measuring axis is not parallel to the rotation axis.

Optimization of Pig Positioning Method Based on Uniaxial Magnetoresistive Sensor

Abstract Uniaxial magnetoresistive sensors based on the HMC1001 can realize acquisition, processing, and display of magnetic signals, with measurement error controlled to within 1 %, basically satisfying application requirements for positioning of the pig labeled with magnets. Given that the HMC1001 sensor has only one sensitive axis, to ensure real-time detection of the maximum magnetic fluctuation when the pig passes, according to the one-dimensional coordinate classical positioning method for uniaxial magnetic sensors, the horizontal east–west direction pipeline is first modeled, and the magnetic fluctuations in the horizontal and vertical directions are calculated. The results show that fluctuations in the vertical direction were slightly larger than those in the horizontal. For other angles between horizontal and vertical, the angle variable is introduced, and the comparison reveals that the magnetic fluctuation curve smoothly transitions from horizontal to vertical. The optimal detection attitude of the pipeline in any direction is then simulated by using the same method, revealing that the vertical magnetic value is the largest. Finally, related equivalent experiments are conducted, and the experimental curves are basically consistent with the simulations. Therefore, it can be concluded that the HMC1001 sensor should be installed perpendicular to the pipeline for optimal detection when positioning the pig.

The Quadrature Method: A Novel Dipole Localisation Algorithm for Artificial Lateral Lines Compared to State of the Art.

The lateral line organ of fish has inspired engineers to develop flow sensor arrays—dubbed artificial lateral lines (ALLs)—capable of detecting near-field hydrodynamic events for obstacle avoidance and object detection. In this paper, we present a comprehensive review and comparison of ten localisation algorithms for ALLs. Differences in the studied domain, sensor sensitivity axes, and available data prevent a fair comparison between these algorithms from their original works. We compare them with our novel quadrature method (QM), which is based on a geometric property specific to 2D-sensitive ALLs. We show how the area in which each algorithm can accurately determine the position and orientation of a simulated dipole source is affected by (1) the amount of training and optimisation data, and (2) the sensitivity axes of the sensors. Overall, we find that each algorithm benefits from 2D-sensitive sensors, with alternating sensitivity axes as the second-best configuration. From the machine learning approaches, an MLP required an impractically large training set to approach the optimisation-based algorithms’ performance. Regardless of the data set size, QM performs best with both a large area for accurate predictions and a small tail of large errors.

Vibration effect correction method of inclinometer in intermittent transonic wind tunnel

In order to solve the problem that the servo accelerometer-based inclinometer is always affected by vibration of the aerodynamic test model when measuring the angle of attack in the intermittent transonic wind tunnel, a vibration effect correction method based on two tri-axial accelerometers is proposed in this paper. In this method, the tri-axial accelerometers are symmetrically mounted on the front and rear sides of the inclinometer along the sensitive axis, and then the centrifugal accelerations caused by different vibration modes and different directions are calculated by time-frequency analysis, numerical integration and equivalent formula. Finally, the total angle measurement error can be accumulated by the angle measurement error caused by each vibration mode. Experimental results of intermittent transonic wind tunnel show that the difference between the proposed method and the Elastic Angle Correction method is less than 0.05 degree when the vibration peak is less than 5 g.

Comparison of islet cell function, insulin sensitivity, and incretin axis between Asian-Indians with either impaired fasting glucose or impaired glucose tolerance, and normal healthy controls

AimsThe objective of this study was to compare the islet cell function, insulin sensitivity, and incretin axis between Asian-Indian subjects with either impaired fasting glucose (IFG), or impaired glucose tolerance (IGT), and normal glucose tolerance (NGT). Materials and methodsPrediabetes subjects underwent a mixed meal tolerance test(MMTT) after overnight fasting. Samples for glucose, insulin, glucagon, and glucagon-like peptide-1 (GLP-1) were collected at 0, 30, 60, and 120 min. Insulin secretion sensitivity index -2 (ISSI-2) for beta-cell function and Matsuda index for insulin sensitivity were assessed. Alpha cell function was assessed by measuring the area under the curve (AUC) 0-120 glucagon/AUC0-120 glucose. ResultsA total of sixty subjects were recruited with 20 in each group. The beta-cell function represented by ISSI-2 was impaired in prediabetes subjects as compared to NGT group (IFG: 2.09 ± 0.44 vs. NGT: 3.04 ± 0.80, P < 0.0001, and IGT: 2.33 ± 0.59 vs. NGT: 3.04 ± 0.80, P = 0.002). Similarly, AUC0-120 glucagon/AUC0-120 glucose was also lower in prediabetes group as compared to healthy controls (IFG: 0.41(0.54) vs. NGT: 1.07(0.39), P = 0.003 and IGT: 0.57(0.38) vs. NGT: 1.07(0.39), P = 0.001). ConclusionAsian-Indian prediabetes subjects have reduced beta-cell function with lesser glucagon secretion during MMTT as compared to normal healthy controls.

КЛАСИФІКАЦІЯ АВТОМАТИЗОВАНИХ ПРИЛАДОВИХ КОМПЛЕКСІВ СТАБІЛІЗАЦІЇ

The article is devoted to automated instrument stabilization systems. The authors systematized and presented the classification of modern stabilizers. High-precision automated instrument stabilization systems are used in light armoured vehicles, performing the functions of search acceleration, determining the coordinates of moving objects in extreme conditions; observation of ground, air and surface targets. Also promising is the use of automated instrumentation stabilization systems in aviation gravimetry for the exhibition of the axes of sensitivity of navigation sensing elements (gravimeters). A characteristic feature of the development of modern technology is the improvement of technical characteristics of all instrumentation systems that are part of the product management system, including stabilizers. This process is due to the transition to a digital element base, the use of new information sensors, new optoelectronic surveillance devices and the development of new circuit design solutions, which, in turn, increases the speed of equipment and its manoeuvrability due to greater automation. The article reveals the principle of classification of stabilizers: by object of stabilization, by number of stabilization planes, by type of measured coordinate, by gyroscope function, by type of actuator, by type of regulation, by type of circuit design. The functioning of the digital instrumental system for measuring mechanical parameters and stabilization by means of functional and structural diagrams of the channel of the automated instrumental stabilization complex is shown. The above is a new, more detailed classification of automated instrumentation stabilization systems, which systematizes the principles of construction of modern stabilizers.

Ground semi-physical simulation experiment study of one-dimensional drag-free control

Drag-free control is one of the key technologies for the verification of Taiji-1 satellite. In the direction of sensitive axis, the drag-free controller receives the measurement signal from the high-precision gravitational reference sensor on the satellite, and instructs the micro-thruster system to counteract the disturbance force acting on the sensitive axis, so that the microgravity level in the sensing axis direction of the satellite can reach the order of 10[Formula: see text] m/s2 in the measurement band. In order to fully verify the drag-free control system, a ground one-dimensional drag-free semi-physical simulation system is built to simulate the performance of various payloads in the drag-free control loop, and to verify the performance and technical targets that the drag-free control system can achieve in the ground control loop. Through the small angle approximation, the equivalent relationship between the rotation of the experimental model and the translational motion of the experimental satellite in the direction of drag-free is demonstrated. In the condition of neglecting the stiffness and damping of the suspended pendulum, the parameters of the suspended pendulum are designed according to the principle of equal acceleration, and their effectiveness is verified by numerical simulation. According to the operation mode of on orbit drag-free control, the ground drag-free experimental scheme and drag-free controller are designed, and the experimental research and verification are carried out. The results show that the controller can effectively control the displacement and acceleration of the experimental model, and also can effectively suppress the disturbance of certain amplitude and frequency.

A sensitive micromachined resonant accelerometer for moving-base gravimetry

A sensitive micromachined resonant accelerometer that exhibits extremely low noise floor and excellent bias stability is presented for future application of moving-base gravimetry. An overall structure optimization is presented for large scale factor and low noise, which is significant for measuring variations in the gravitational field of the Earth. The experimental results show that the MEMS accelerometer has a scale factor up to 876 Hz/g and a noise floor down to 75ng/Hz by setting a relatively low full-scale range of ±5 g. The experimental results of the resonant accelerometer with ±0.01°C temperature control show that the averaged bias stability for one day duration is 0.197 μg and the bias repeatability within about 3 months is 1.56 μg. Furthermore, a six-day measurement duration of the accelerometer with its sensitive axis perpendicular to the ground shows a sensitive measurement synchronously with the Earth's tidal gravity, which demonstrates that the resonant accelerometer has the capability for high-performance applications such as moving-base gravimeters and shipborne inertial navigation systems.