This paper presents a Novel Adaptive Fuzzy Extended Kalman Filter namely (NAFEKF) which has been developed and applied for attitude estimation using only the outputs of strap-down IMU (Gyroscopes and Accelerometers) and strapdown magnetometer.

The NAFEKF, which is based on EKF (Extended Kalman Filter) aided by FIS (Fuzzy Inference System), is validated in Matlab environment on simulated trip data and real data acquired during an UAV’s trip. Accuracy of estimated attitude is increased using NAFEKF compared to typical EKF and in addition the measurement noise covariance matrix is tuned, the proposed filter uses multiplicative error for quaternion.

Simulation results show that estimated measurement noise covariance matrix is closed to its true value in cruise phase of flight (stationary phase), while in nonstationary phase it refers to the validity of accelerometer measurement model in the filter in NAFEKF; it neglects measurements from accelerometers in this case.

We propose a method to estimate the distance to objects based on the complementary nature of monocular image sequences and camera kinematic parameters. The fusion of camera measurements with the kinematics parameters that are measured by an IMU and an odometer is performed using an extended Kalman filter. Results of field experiments with a wheeled robot corroborated the results of the simulation study in terms of accuracy of depth estimation. The performance of the approach in depth estimation is strongly affected by the mutual observer and feature point geometry, measurement accuracy of the observer’s motion parameters and distance covered by the observer. It was found that under favorable conditions the error in distance estimation can be as small as 1% of the distance to a feature point. This approach can be used to estimate distance to objects located hundreds of meters away from the camera.

The results of study of a prototype fiber-optic gyroscope with accuracy grade 0.01–0.001 deg/h are presented. The gyroscope comprises three feedback loops: one for Sagnac phase shift compensation, the second one for the scale factor stabilization, nd the third (fast-response) one for the compensation of constant component of optical signal on the photocell, affecting the measurement channel. To increase the accuracy of the prototype gyroscope up to the level of 0.001 deg/h, it is proposed to use the fourth and the fifth feedback loops which will suppress the parasitic effects in the integrated optic phase-shift modulators.

Software- and hardware-based methods of compensation for dynamic errors of the marine gravimeters caused by inertial accelerations are considered. The error due to the fluid damping of the gravimeter sensing element is analyzed and taken into account for the first time. Some results of gravity measurements that confirm the increase in gravimeter accuracy are presented.

The paper discusses the structure, algorithms and testing results for a hybrid precision strapdown inertial navigation system (SINS) which is resistant to fast extreme impacts. Impact resistance of the precision SINS is provided by incorporating an auxiliary strapdown inertial attitude control system (SIACS) based on rough sensors that can endure fast extreme shocks without losing the attitude accuracy; and by post-processing of inertial sensors data performed in the onboard computer simultaneously with the main navigation task. The post-processing procedure is designed to identify the moment of shock occurrence and to repeat the attitude problem solving in the onboard computer based on the auxiliary SIACS data within the time interval of exposure to the extreme shock. In the absence of shocks, the auxiliary SIACS is calibrated in accordance with the data of the main precision SINS. The main precision SINS is based on precision fiber-optic gyros (FOG) and the auxiliary SIACS – on micromechanical gyros (MMG). Thus, a hybrid-type precision SINS has been constructed, which has demonstrated required accuracy level during onground vehicle tests, including shock tests.

The paper presents the results of development of an angle measurement system for measuring the angles between the normals to the mirrors setting the directions in space. The system operates in a dynamical mode with a continuously rotating platform on which an autocollimating null indicator is installed. The angles are measured by means of a holographic angle encoder installed on the rotor of the system. The results of the system testing and calibration are presented. The system is calibrated by comparing it to a reference optical polygon.

The paper addresses the main problems related to the development of underwater communication network which differs from the traditional underwater acoustic communication in simultaneous information interoperability of a large number of spatially separated nodes, including data exchange between them, as well as their highprecision positioning. While the problems of traditional acoustic communication are generally associated with the complexity and variability of acoustic channel for signal propagation, the underwater communication network faces a numer of additional significant problems such as collisions in the network, occurring during simultaneous transmission of messages from several nodes and requiring special managerial and engineering measures for their elimination (mitigation); another problem is complex configuration of the zones of binary mutual “audibility” of nodes, caused by specific features of underwater acoustic environment and requiring the nontrivial routing of data flows from source to recipient. It is demonstrated in the paper that these problems can be solved by developing the techniques of communication signals generation and emission, which then form the protocols of nodes’ interaction during transmission and receipt of messages, and are implemented in digital acoustic modems that have ultimately developed into complex radio-electronic devices.

Refinement of the electrostatic gyroscope (ESG) drift model aboard an orbital maneuverable satellite for remote sensing of the Earth’s surface is considered. Some changes of the drift model also hold for the ESG ground-based applications. The paper also analyzes the quasi-continuous correction mode of the ESG-based strapdown inertial attitude reference system (SIARS) using raw (unsmoothed) data from the star tracker and the extended Kalman filter (EKF) algorithm. A special feature of solving the problem of SIARS output data correction and the calibration problem in this mode is rejection of incorrect measurements. The algorithm for this problem solution is described. The ESG drift model is given both for the SIARS calibration mode in order to ensure an adequate prediction of ESG drifts over a long time interval and for the quasi-continuous correction mode under spacecraft maneuvering conditions. The results of data processing of the flight tests of the SIARS and the star tracker aboard one of the spacecraft are discussed.

The paper discusses a design solution for a single-gyro meter of three angles of a moving object's rotations. In terms of physics, this solution is based on the forces of rotation and one- and two-component translational motions of a spherical rotor in electrostatic suspension, generated by a gyro torque motor and sensors. Theoretical substantiation, algorithms and results of comparative mathematical modeling are presented. It is shown that one-component oscillations of the rotor in the equator plane provide the azimuth angle error that is three times smaller than that of two-component oscillations.

A method for sensors calibration in a strapdown inertial measurement unit on a relatively rough (1-2) turntable is proposed, which integrates direct and indirect techniques. The calibration errors are estimated analytically and by mathematical modeling. For direct techniques, the choice of programmed attitudes is explained, and the vector and scalar methods are compared. The results of the method application for calibrating a measurement unit based on fiber-optic gyroscopes are presented.