The paper presents methodologies of airborne gravimetry surveying and data postprocessing when a strapdown airborne gravimeter is used. Both methodologies were developed based on our experience in processing raw data from state-of-the-art strapdown gravimeters flown in several aerogravimetry campaigns carried out in 2020-2022 using various carriers (including unmanned aerial vehicles). We also present the numerical results from some of the campaigns and provide the achieved accuracy and spatial resolution of airborne gravity data, from which it can be concluded that the data can be used in geophysical applications. For a survey based on an unmanned aerial vehicle, we show the possibility of reaching 1-km spatial resolution of gravity data. For one of the aircraft-based surveys, we also show the possibility of vector gravimetry with an accuracy of 2-3 mGal for the estimated gravity horizontal components.
The paper presents a comparison of Wiener stationary filters, which solves a on-line estimation problem, and Wiener smoothers built using the method of local power spectral densities approximation for estimated signal and interference, with Kalman nonstationary filters and smoothers used in processing the results of a marine gravimetric survey. The results of comparison of gravity anomaly estimates obtained with different filters using simulation and real data are presented. The advantages and disadvantages of the compared filters and smoothers are discussed.
Choosing four kinds of adhesives (A, B, C and D) with different parameters, we mainly analyze the influence of the thermal expansion coefficient and elastic modulus of adhesives on the variation in the fiber coil size based on ANSYS software. By measuring fiber coil loss, fiber coil polarization crosstalk and scale factor temperature sensitivity of FOGs, it has been found that A adhesive is the best for FOGs that use the fiber coil with skeleton. And the scale factor temperature sensitivity is only 23.52 ppm/℃ in the temperature range from −40 °C to 60 °C, which shows that correlation between scale factor and temperature is better than that of others. Moreover, the compensated scale factor variation of the FOG with A adhesive will reach to 200 ppm in the temperature range from −40 °C to 60 °C, which improves the performance by 60%.
Two types of locked angular motion of control object based on strapdown inertial navigation system are under consideration. The mentioned motions are given as a certain sequence of spatial turns relative to body (instrument) axes. Structural changes of angular position error of control object relative to instrument axes based on the results of typical motion are examined. Besides, it is supposed that angle-measuring channels are dominated by errors proportional to measuring signal. Possibility of instrument axes error redistribution by typical locked angular motion parameter setting is shown. Directions of improvement of the control object main characteristics based on strapdown inertial navigation system using such typical motion are described.
The paper describes a technique for designing and optimizing the bearing structure of a strapdown inertial navigation system aiming to reduce the instrumental errors of sensors caused by the deformation of the bearing structure under the complex action of an external and internal loads considering the mass minimization of an inertial measurement unit at the same time. In order to solve current tasks an algorithm that combines multi-objective parametric optimization and structural topological optimization was developed. As an illustration of the described technique application, the process of optimizing the bearing structure of a particular device of a strapdown inertial navigation system was considered. Two-stage multi-objective parametric optimization was performed in order to maximize the stiffness of the structure, and then, using topological optimization, the mass of parts was minimized. It was shown that the proposed combination of parametric and topological design optimization techniques allows us to switch from multi-objective optimization to single-objective optimization with the assumption of insignificant change of stiffness.
The accumulation of stars images, distorted by a motion blur, is performed in two stages. First, each frame intended for accumulation goes through the motion blur-matched digital filter. Matched filtering localizes an arbitrary blurred image of a star in one known pixel. Synthesis of the impulse response of the matched filter is performed using the measurements of a gyroscope attached to the camera. The filtered frames are then added pixel by pixel in the accumulator, without any additional rotation transformation. The results of the simulation, performed for accumulation with "pixel" resolution, show the possibility of detecting blurry images of relatively dim stars against the background of the daytime sky.
The paper studies the current state of fiber-optic gyroscopes (FOG) development. An overview of the modern market of gyroscopes for inertial navigation is presented with a special focus on the FOG niche. The principle of operation is briefly described; classification of existing FOGs is presented; their advantages and disadvantages are discussed; and some examples of existing devices are given. Key Russian and international manufacturers are mentioned in the paper. Finally, trends of FOG development are observed, and the future development of the gyroscope market is assessed.
The paper describes the development, testing, and implementation of navigation algorithms for unmanned wheeled agricultural vehicles when the navigation equipment consists of a low-precision inertial navigation system (INS) with microelectromechanical sensors (MEMS), a receiver of Global Navigation Satellite Systems (GNSS), and odometry data — odometer-derived velocity and a steering sensor.In the operation of unmanned agricultural machinery, the navigation problem is one of the most important. For the treatment of most agricultural crops, the positioning accuracy of the corresponding equipment needs to be a few centimetres. High accuracy is also important to reduce fuel costs and ensure safe operation of agricultural machinery for humans. The reliability of the navigation solution depends on its stability to outliers and short-term losses of GNSS data.The work considers two types of equipment configuration which are structurally different: non-articulated (classic) and articulated. The classic configuration implies a four-wheeled vehicle, which is steered by the front or the rear axle. The articulated configuration implies two frames connected by a joint, each of which has two wheels fixed to the corresponding frame. In this configuration, one can make a turn by changing the angle between the frames.
Affected by the ship deformation, the navigation accuracy of multi inertial navigation system fusion will suffer degradation. In order to solve the problem, a fusion method considering ship deformation based on inertial vector matching and rotation incentives is proposed. The inertial vector matching method takes the difference of angular velocities and specific forces between two INSs as the measurement to estimate the ship flexure. However, the traditional method can only estimate the difference of the two INSs biases, but cannot estimate the respective biases themselves. By designing different rotation schemes, the two INSs gyroscope and accelerometer sensitive axes orientation are different in each rotation modulation period. In this way, the respective biases can be incentivized and estimated through the Kalman filter. The simulation results demonstrate that the proposed fusion method can effectively estimate the respective horizontal biases and reduce the ship flexure estimation error.
Lissajous frequency modulated (LFM) gyroscope based on Micro-Electro-Mechanical System (MEMS) craft have been mainly used for military and civil applications. The performance of LFM MEMS gyroscope is restricted by the phase noise of the demodulation algorithm and frequency readout circuits. However, the accuracy of conventional demodulators such as multiplication and original least mean square demodulation (LMSD) which are commonly used, is limited by the noise suppression performance. In order to break through the bottleneck, a novel improved LMSD based on adaptive moment estimation (Adam) algorithm for LFM MEMS gyroscope has been proposed in this paper. The proposed demodulator is appropriate for the demodulation of weak signal from noise, and can achieve the lower noise level and high precision output of sense mode of LFM MEMS gyroscope. The simulation verification of three different demodulation algorithms is carried out, and the results show that the Adam-LMSD algorithm has the lowest noise level, and the frequency demodulation accuracy can reach 1.7 × 10 −7 Hz.
A universal methodology for the monitoring of inertial measurement units (IMU) for strapdown inertial navigation systems (SINS) by introducing a complex parameter in conditions of active production at the manufacturer side and at the stage of pre-installation inspection at the consumer side is considered. A methodology for verification of the complex parameter, as well as justification of the tolerance value for said parameter is proposed. The methodology is confirmed by many years of flight tests of Soyuz and Progress spacecraft.
The article describes development of a local radionavigation system based on a ranging code. Principles of coordinate determination by correlation of ranging codes demodulated from radio signals emitted by local beacons are discussed. The design of the local navigation system is outlined and first results of coordinate determination are reported.
We present the results of developing algorithms for a MEMS- based attitude and heading reference system, being a part of a backup avionics system. We describe the features specific to the attitude determination algorithm and demonstrate its accuracy assessment results based on flight tests.
A new shear mathematical model is proposed for a lamellar accelerometer made of a porous functionally graded material (PFGM) with an attached mass in a temperature field. The accelerometer consists of lamellar structures, which are lamellas and shallow shells of small curvature. The problem of eigenvalues is solved using the Bubnov-Galerkin method in higher approximations, and numerical examples are provided to support the model.
An algorithm for determining the coordinates of a moving object based on from several optical sensors is considered. The change in the angular position is determined based on a comparison of optical sensor data at the current and previous time points. A feature of the algorithm is the use of three or more spaced cameras to determine the position of a moving object.
A method for observing an object in a radar with quasi-continuous chirp radiation is presented for a wide range of relative speeds, including zero and supersonic velocities when an object approaches/recedes. The results confirming the effectiveness of the proposed method are presented.
A method and device are proposed for landing an aerospace aircraft by docking with a heavy ekranoplan, allowing them to land together on a water or other flat surface. A useful result is an increase in the payload of the orbital aircraft due to the absence of a wheeled chassis and the elimination of the need to build a special expensive runway for its landing.
The article is devoted to the development of an algorithm for the satellite formation control system based on the system passivation by feedback. A variant of the control law using additional outputs of the system is considered. It is shown that the addition of integral components allows for increasing the accuracy of the system. Simulations were performed for a group of 8 satellites in two PCO orbits.
This paper presents the calibration of magnetometers of the attitude dynamics and control system of the SamSat-ION nanosatellite. A method of temperature calibration of magnetometers in twelve static positions is proposed. The operability of on-board systems in conditions of temperature difference has been tested. The accuracy of determining the parameters of the temperature dependence of the bias, scale factor and non-orthogonality coefficients of magnetometer sensors is estimated. The main results of ground tests of flight models of on-board systems of the SamSat-ION nanosatellite are presented. The proposed approach ensures reliable operation of the orientation and stabilization system of nanosatellites based on the use of magnetometers when exposed to various temperature gradients.
