Abstract: —A new mathematical model has been constructed for the motion of a single-crystal resonator of a wave solid-state gyroscope in the form of a thin elastic shell rotating on a moving base, taking into account the influence of an electrostatic system of oscillations excitation. The expression derived for the potential energy of elastic deformation of the resonator takes into account low anisotropy of the cubic crystal type depending on the resonator orientation relative to the crystallographic axes. A discrete model is used to describe the energy of the electrostatic field of control sensors. Using the Lagrange−Maxwell formalism, nonlinear differential equations are obtained that describe, in the single-mode approximation, the oscillations of the elastic shell rotating on a moving base. The forced and free oscillations of the resonator are considered. It is shown that a systematic error caused by anisotropy of the elastic properties of the resonator material can be compensated by the effect of electrostatic forces of the control sensors. Control signals are proposed to compensate these errors. PubDate: 2020-07-01
Abstract: Modern gyroscopy is characterized by a great diversity of gyroscopes that have been and are being developed. Dominant positions belong to wave optic gyroscopes implementing the relativistic Sagnac effect, and micromechanical vibratory gyroscopes the operating principle of which is based on Coriolis effect. At the same time, high-precision rotor mechanical gyroscopes based on the principles of rotating solid body dynamics partially retain their position; also, the research of gyroscopes developed on the principles of nuclear physics and quantum optics is progressing successfully. Current state and the prospects of gyroscopes development are discussed in this paper. PubDate: 2020-07-01
Abstract: The paper studies the problem of reducing the errors of heading and pitch/roll angles for a strapdown inertial navigation system (SINS) based on fiber-optic gyroscopes (FOG) during a vessel maneuvering. The solution of the problem is analyzed mainly for autonomous mode of the system operation using the water speed log data. A specific feature of the studied solution is that the gyro drifts and accelerometer biases are estimated only during the vessel maneuvering. In this case, an attribute is formed for the vessel’s maneuver start. The results of simulation, test-bench and field tests of the SINS on FOGs of navigation accuracy grade during the vessel maneuvering are presented, with the data of the system’s measurement unit, GNSS-receiver and log having been processed in MATLAB (Simulink) software, taking into account the simulation of ocean currents and vessel drift. PubDate: 2020-07-01
Abstract: — A critical functional part of a hemispherical resonator gyroscope (HRG) is the mechanical resonator, and a few million quality factor (Q-factor) is needed for the lowest resolution. This paper focuses on anchor loss of a HRG of a few millimeters in size. A detailed parametric study of dimensions and shell imperfections due to fabrication is carried out. A sensitivity study of the effect of shell mean radius, shell thickness, stem radius, stem height on the Qanchor is carried out. The effect of geometric imperfections such as shell offset, shell tilt, shell thickness variation, and unbalance is studied in detail. From the study, it is inferred that the anchor loss becomes very significant and approaches other loss mechanisms even with minor geometric imperfections in the hardware realisation. Based on the sensitivity study, the dimensional and geometric tolerances are arrived for precision fabrication. Precision resonator is fabricated as per the requirement of minimum anchor loss. The significance of other damping mechanisms such as air damping, excitation-induced damping, thermoelastic dynamic damping and surface dissipation is also discussed. Surface characterisation before and after surface treatment has been carried out using nanoindentation technique with regard to surface loss. Functional parameters of operating frequency and Q-factor are evaluated using laser Doppler vibrometry (LDV). PubDate: 2020-07-01
Abstract: — The article considers a problem of autonomous underwater vehicle (AUV) positioning with acoustic measurements of range and possibly radial velocity relative to a single beacon, velocity components and coordinate increments from an inertial navigation system, and the data from a water-speed log or a ground log. Interruptions in acoustic measurements reception are acceptable. Availability of a priori information on relative position of AUV and the beacon is not assumed. In order to solve the problem, the author proposes a multiple model algorithm based on a bank of extended Kalman filters which independently estimate the initial horizontal range and errors of the used data under different hypotheses about a value of AUV initial azimuth relative to the beacon. Current coordinates of AUV are determined by the outputs of filters, taking into account the a posteriori probabilities of the corresponding hypotheses. The algorithm is rather simple for programming and does not require much computational power. PubDate: 2020-07-01
Abstract: — Reduction of optical quantum sensors in size, including nuclear magnetic resonance (NMR) gyroscopes, implies primarily downsizing of the working gas cell. This paper considers the dependence of isotope shift in the balanced scheme based on NMR in xenon isotopes on the dimensions of the gas cell. With this aim in view, an experimental and theoretical studies of the factors affecting the relaxation rate of xenon isotopes have been carried out. The proposed numerical model allows predicting the magnitude of the isotope shift for cells of various sizes with variations in their basic parameters, namely, temperature and pressure of the gas mixture. Based on the results of the numerical simulation, recommendations are given for optimizing the basic parameters of the gas cell by changing its dimensions. PubDate: 2020-07-01
Abstract: Reconfiguration of a motion control system (MCS) for an autonomous underwater vehicle (AUV) in case of failure of some of the controls or actuators that provide the vehicle propulsion and maneuvering is discussed. The features of actuators operating on different physical principles are analyzed. A nonlinear mathematical model of the vehicle motion is formed taking into account the features of the seawater medium due to higher viscosity. Nonlinearity does not allow traditional approaches to reconfiguration of aircraft motion control system to be used for the purposes described in this paper. The approach proposed for reconfiguration of the AUV MCS consists in the preliminary analysis of the conditions for using different kinds of actuators depending on the vehicle speed and maneuver. The choice of alternative efficient actuators is dictated by the need to compensate for the forces and moments generated by the failed equipment or the actuator to the maximum extent possible. The results of the AUV MCS reconfiguration are obtained for a failure of a bow rudders gear during the diving maneuver on the acceleration section of the path. Vertical thrusters are taken as backups capable of compensating for the forces and moments of the jammed bow rudders gear. The comparative quantitative estimates of the AUV MCS reconfiguration were obtained by mathematical simulation of the AUV diving maneuver. Further research is needed to extend the proposed approach to other AUV systems. PubDate: 2020-07-01
Abstract: The features of a feedback loop in a quantum sensor with a two-frequency spin oscillator are discussed. Engineering solutions that ensure stable two-frequency oscillation and, in particular, the use of automatic gain control units and all-pass filters are considered. The results of experimental studies of oscillation modes conducted on a quantum sensor breadboard are presented for stationary and rotating bases. PubDate: 2020-04-01
Abstract: The paper presents the brief history of development of a precision gyroscope with electrostatic suspension of rotor; the main problems of constructing a gyro with a hollow rotor, as well as their solutions found by the chief designer A.S. Anfinogenov are discussed. PubDate: 2020-04-01
Abstract: — This study analyses the GPS velocity estimation performances of three different estimation models, namely, the time-differenced carrier phase velocity estimation (TDCPVE), Doppler observation velocity estimation (DopplerVE), and precise point positioning velocity estimation (PPPVE). Static and vehicle kinematic experiments are conducted for validation. Under simulated kinematic conditions using static data, the accuracy of the DopplerVE is the worst, and the precision of the velocity by the PPPVE is the same as with the TDCPVE. Under kinematic conditions, the accuracies of the three methods are related to the motion state of the mobile carrier (such as its acceleration and turning). When the sampling interval is 1 s, the TDCPVE can obtain precise velocity using a single-frequency stand-alone GPS receiver; the TDCPVE and DopplerVE can obtain accuracies of the same order of magnitude with broadcast and precise ephemerides, and can be used for real-time velocity measurement; the PPPVE can obtain not only an accurate position, but also an accurate velocity. PubDate: 2020-04-01
Abstract: According to well-described literature concerning the work history of multipath mitigation in the global navigation satellite systems (GNSS), multipath is still the most dominant factor in a challenging environment. There are unperturbed harsh circumstances where GNSS signals cannot reach and smartphone navigation is not possible. The main objective of this research is to find an accurate solution for pedestrian smartphone navigation in a multipath environment. Experiments are done with micro-electro-mechanical system (MEMS) sensors mounted on a smartphone, and no extra hardware is needed. The latest Android smartphone is used to log the data files of GNSS and MEMS sensors. This scheme has been classified in the synopsis, and a rectangular route with three perpendicular turns has been selected for a pedestrian walk. The data is preprocessed using a low pass filter to remove high-frequency noise and smooth the signal. The description of accumulative error produced by the heading and step size estimation has been reduced by implementing the indices of mean cumulative heading error and cumulative step length error, respectively. In the end, the suboptimal extended Kalman filter algorithm is used to fuse the data of GNSS and pedestrian dead reckoning (PDR) for final results. In this paper, we try to give a technique to provide accurate pedestrian smartphone navigation. The fusion results show that the prospective method explores the possibility to use smartphone navigation in any case when GNSS or PDR information is not available. Substantial simulations are implemented and corroborate that the schemed method is sturdier to use in a harsh environments. The aim is to achieve high-level accuracy with an ultra-low-cost solution. PubDate: 2020-04-01
Abstract: The paper presents brief information on the results of research and development activities undertaken in 2015–2019 and aimed at the practical implementation of e-Navigation concept. Current state of practical application of S-mode, the only global product created within the concept, is studied. Most of the new technologies developed under the main regional projects are discussed. Special focus is made on the situation with e-Navigation in Russia. PubDate: 2020-04-01
Abstract: Probabilistic study of angular motion dynamics has been performed for CubeSat nanosatellites with passive stabilization systems, including aerodynamic, aerodynamic-gravitational, gravitational, and gravitational-aerodynamic ones. Analytical functions of the maximum angle values distribution have been obtained for a nanosatellite axes deviation from required directions (orbital velocity vector or a local vertical) for uniform distribution and Rayleigh distribution of component values of the initial angular velocity vector. Formulas have been derived and nomograms have been plotted for selecting the design parameters (geometrical dimensions, static stability margin, moments of inertia) which ensure the required attitude with the specified probability in circular orbits. PubDate: 2020-04-01
Abstract: A new algorithm for geophysical map-aided navigation is proposed. It does not require any preliminary estimation of the field measured along the vehicle trajectory and, as consequence, does not need any stochastic field model. The algorithm uses a whole set of the available geophysical field measurements. The accuracy analysis procedure applied to estimate the effectiveness of the proposed algorithm is described. The features and advantages of this algorithm are illustrated by an example of marine gravity-aided navigation. PubDate: 2020-04-01
Abstract: — The Allan variance was originally meant to be a characteristic of time and frequency standards, but now it is widely used in many fields, including the development of navigation devices. The paper considers different applications of the Allan variance to various tasks, among which is estimation of characteristics of navigation devices. However, sometimes the Allan variance does not seem to be very effective; besides, its physical interpretation may be vague. This is due to its empirical definition as an alternative estimate of variance. The paper considers the definition of the Allan variance based on a model of random processes with stationary increments that include both stationary and Wiener processes. In this model, the main characteristic is the structure function, whereas the Allan variance turns out to be its empirical estimate. This representation makes the statistical meaning of the Allan variance clear and explains its high effectiveness in the analysis of nonstationary signals and noise. It also allows the Allan variance to be used as a general characteristic describing stability of measuring and navigation devices, the one that is different from variance. PubDate: 2020-04-01
Abstract: — The limitations of Kalman filter (KF) have motivated researchers to consider alternative methods of integrating inertial navigation systems (INS) and global navigation satellite systems (GNSS), predominantly based on artificial intelligence (AI). Over the past two decades, a great number of research gained in order to validate the possibility of using AI methods in the field of integrated navigation systems. Different approaches have been proposed for combining AI modules with the other parts of the INS/GNSS system. The article suggests a new classification of the resulting schemes based on the functionality of AI modules in the INS/GNSS system. The paper also provides a brief explanation of each scheme with its advantages and disadvantages. Some aspects that need to be considered in future research in this field are also highlighted. PubDate: 2020-01-01
Abstract: The paper presents the gravimeters for measuring the gravity from moving platforms, and the stages of their development at the Concern “Central Scientific Research Institute “Elektropribor” (hereinafter CSRI Elektropribor). Engineering solutions are described, due to which high accuracy of measurements has been achieved. The authors discuss popular applications of mobile gravimeters. PubDate: 2020-01-01
Abstract: The paper deals with the possibility of direction finding and determining the coordinates of a source of acoustic signal emitted by a surface or underwater vehicle in the subsonic frequency range. For this purpose combined hydroacoustic receivers are used. During the first experiment, the estimates of the systematic component of direction finding error were obtained when the source emitted a tone or polyharmonic signal, and the direction finding results were averaged over a set of frequencies. The obtained results were used in the second experiment for estimating the error in determining the coordinates of the polyharmonic signal emitter consisting of three combined receivers (CR) which form the navigation base distributed in the horizontal plane. PubDate: 2020-01-01
Abstract: The results of a comparative analysis of methods for positioning and timing support of remote users based on GNSS measurements from a GLONASS receiver and observational data on quasar radiation from compact very long base radio interferometric (VLBI) systems are discussed. Using radio telescope measurements increases the stability of positioning-and-timing and navigation support of users owing to observations of radio-frequency radiation emitted by the sources of natural origin. The approach proposed in this paper focuses on using radio interferometry for precision positioning and timing of remote radio telescopes. This method can be helpful for specific applications relevant to positioning and timing support for remote users with an arbitrary positioning topology. PubDate: 2020-01-01
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