Relative Attitude Determination Research Articles

Localization Method for Underwater Robot Swarms Based on Enhanced Visual Markers

In challenging tasks such as large-scale resource detection, deep-sea exploration, prolonged cruising, extensive topographical mapping, and operations within intricate current regions, AUV swarm technologies play a pivotal role. A core technical challenge within this realm is the precise determination of relative positions among AUVs within the cluster. Given the complexity of underwater environments, this study introduces an integrated and high-precision underwater cluster positioning method, incorporating advanced image restoration algorithms and enhanced underwater visual markers. Utilizing the Hydro-Optical Image Restoration Model (HOIRM) developed in this research, image clarity in underwater settings is significantly improved, thereby expanding the attenuation coefficient range for marker identification and enhancing it by at least 20%. Compared to other markers, the novel underwater visual marker designed in this research elevates positioning accuracy by 1.5 times under optimal water conditions and twice as much under adverse conditions. By synthesizing the aforementioned techniques, this study has successfully developed a comprehensive underwater visual positioning algorithm, amalgamating image restoration, feature detection, geometric code value analysis, and pose resolution. The efficacy of the method has been validated through real-world underwater swarm experiments, providing crucial navigational and operational assurance for AUV clusters.

Range-Based Relative Navigation for a Swarm of Centimeter-Scale Femto-Spacecraft

In-orbit relative navigation between a networked swarm of centimeter-scale femto-spacecraft would add considerable value to a range of space mission concepts and applications, such as for multipoint sensing and distributed sparse aperture interferometry. For a swarm of networked femto-spacecraft, relative position determination would be possible by inferring coarse range estimates from the received signal strength indication associated with the communication link between swarm members. This is particularly advantageous for highly resource-constrained devices. In this paper, algorithms for swarm relative positioning using interspacecraft range estimates are presented that can be applied to centralized, decentralized, and distributed network configurations. Relative navigation filters for initial relative orbit determination and state estimation are presented for femto-spacecraft swarm deployment and dispersal scenarios. The algorithms presented could also find use in terrestrial applications, in static and dynamic wireless sensor networks.

Performance Assessment of BDS-2/BDS-3/GPS/Galileo Attitude Determination Based on the Single-Differenced Model with Common-Clock Receivers

Global navigation satellite system (GNSS)-based attitude determination has been widely applied in a variety of fields due to its high precision, no error accumulation, low power consumption, and low cost. Recently, the emergence of common-clock receivers and construction of GNSS systems have brought new opportunities for high-precision GNSS-based attitude determination. In this contribution, we focus on evaluating the performance of the BeiDou regional navigation satellite system (BDS-2)/BeiDou global navigation satellite system (BDS-3)/Global Positioning System (GPS)/Galileo navigation satellite system (Galileo) attitude determination based on the single-differenced (SD) model with a common-clock receiver. We first investigate the time-varying characteristics of BDS-2/BDS-3/GPS/Galileo line bias (LB) with two different types of common-clock receivers. The results have confirmed that both the phase and code LBs are relatively stable in the time domain once the receivers have started. However, the phase LB is expected to change to an arbitrary value after each restart of the common-clock receivers. For the first time, it is also found that the phase LBs of overlapping frequencies shared by different GNSS systems are identical. Then, we primarily evaluated the performance of BDS-2/BDS-3/GPS/Galileo precise relative positioning and attitude determination based on the SD model with a common-clock receiver, using a static dataset collected at Wuhan. Experimental results demonstrated that, compared with the double-differenced (DD) model, the SD model can deliver a comparable root–mean–square (RMS) error of yaw but a significantly smaller RMS error of pitch, whether for BDS-2, BDS-3, GPS, or Galileo alone or a combination of them. The improvements of pitch accuracy are approximately 20.8–47.5% and 40.7–57.5% with single- and dual-frequency observations, respectively. Additionally, BDS-3 can deliver relatively superior positioning and attitude accuracy with respect to GPS and Galileo, due to its better geometry. The three-dimensional positioning and attitude (including yaw and pitch) accuracy for both the DD and SD models can be remarkably improved by the BDS-2, BDS-3, GPS, and Galileo combination with respect to a single system alone.

Maneuvers During Automatic Formation Flight of Transport Aircraft for Fuel Savings

Formation flying techniques, demonstrated by migratory birds, have the potential to significantly save energy when two or more transport aircraft fly the same route at the same time. In fuel-saving formations, aircraft are flying straight trajectories for most of the time. For proof of concept, however, how vertical and lateral maneuvers can be flown has to be investigated. Those investigations require a flight simulator that is equipped with adequate flight mechanical models. Not much research exists on maneuvers of formation. The paper addresses the components that are needed to perform this research with real-time flight simulations. They are, first, a method to model wake vortices on curved trajectories; second, a formation flight control system, which comprises a method for the relative position determination, the design of control laws, and suitable cockpit displays; and third, techniques that allow vertical and lateral flight maneuvers. Two different strategies to position the following aircraft relative to the wake vortex during turns are described, and simulation results show their differences in terms of fuel savings and passenger comfort. Piloted flight simulator tests confirmed the usability of the proposed flight techniques for formation maneuvers, and the participating airline pilots indicated general consent to the concept.

Determination of relative position of antenna system and RGB-D sensor in combined microwave imaging system

Microwave imaging technique allows obtaining images of hidden objects in structures and media using microwaves. This technique has various applications such as: nondestructive testing, medical imaging, concealed weapon detection, through-the-wall imaging, etc. Obtaining radar images in these applications is based on processing phase and amplitude of the reflected signal recorded over an aperture (a microwave hologram). Recently, systems began to appear in which the radar part is supplemented by an RGB-D sensor, which allows to obtain new capabilities. For example, there is the a microwave screening system architecture in which inverse synthetic aperture is formed by the natural motion of the subject in the vicinity of a stationary linear antenna array. The microwave system is complemented with an synchronous RGB-D video sensor which captures the trajectory of the moving subject in 3D and allows coherent processing of the radar signal. Another system detects objects buried under irregular surface and uses RGB-D sensor for capturing the surface relief for suppressing reflection of the sounding signal from the surface. Calibration between a radar and an RGB-D sensor is an essential process for microwave and optical data fusion. This article presents a novel approach for calibration, using a planar calibration target which is made of radiotransparent material (such a foam plastic sheet) with square marker and six small metal balls embedded in target surface and representing point objects. The proposed method exploits 3D-3D correspondences between coordinates of point objects in two coordinate systems associated to the sensor and to the radar. One points set is extracted from optical data, using marked corners of the target as a base points. Second points set is obtained from microwave data as local maxima of 3D volume of data reconstructed from one-frequency microwave hologram. Computer modeling were performed using Autodesk 3ds Max software by which models of all components of the system were built and the optical image from the sensor was modeled. Test experiments were carried out using a measurement system composed of the following components: a compact vector network analyzer (VNA), two mechanical scanners with stepper motors, one transmitting and one receiving horn antennas, mounted on the VNA, an RGB-D sensor, a microcontroller board, and a computer. The high accuracy of the method is confirmed both by computer modeling and physical experiment. The accuracy of determination of relative position between the radar and the sensor is about one fifth of the signal wavelength used.

On-board Relative Attitude Determination and Propagation Using Earth Sensor

In this paper, we propose methods to determine and propagate relative attitude using an earth sensor. Three-axis attitude determination using the Earth sensor is advantageous in terms of space consumption, but it is a fault that we cannot always use it. By detecting and propagating relative attitude information, we attempt to fill that time gaps. The difficulty is that the spacecraft cannot ignore its own translational movement when it looks at the earth, unlike when it looks at the stars. In this research, the attitude and position estimation method used in computer vision is applied instead of the traditional attitude determination method for spacecrafts used in STT and so on. The algorithms use the movement of a point common to two images taken with a time interval, and the translational movement information of the spacecraft obtained from orbit information. The obtained relative attitude is propagated using a Kalman filter to estimate the absolute attitude. The proposed algorithms are evaluated by numerical simulations. The results are as accurate as small MEMS gyro sensors, suggesting the possibility of being replaceable in the future.

Adaptive Error-State Kalman Filter for Attitude Determination on a Moving Platform

This article presents a loosely coupled visual/inertial hybrid system for relative attitude determination on a moving platform. The inertial measurements are accomplished by two gyroscopes, of which the slave gyroscope removes the redundant motion of the platform from the total motion sensed by the master gyroscope. To correct integration drift error and compensate for the gyroscope biases, we fuse the inertial and visual measurements fused together through the error-state Kalman filter (ESKF). Furthermore, an improved ESKF is proposed by utilizing the variational Bayesian (VB) inference to adaptively estimate the process and measurement noise covariance. To realize direct estimation of the process noise covariance, a latent variable is introduced and inferred together with the noise covariances and error-state. The practical experimental setup is built up and experiments of two different motion trajectories are conducted. The ESKF, the cubature Kalman filter (CKF), the extended Kalman filter (EKF), the proposed filter, and the other two adaptive filters are implemented for comparison to verify the effectiveness of the proposed filter. The results demonstrate the proposed filter show superiority in reducing both the root mean square error (RMSE) and maximum error (ME) and improving the filter consistency.

Borehole transient electromagnetic array based relative attitude determination for relief well drilling

Drilling relief well is one of the most effective way to control blowout well at present. In order to improve the connection rate, the relief well needs to trace a short distance and then gradually approaches the accident well, where the relative space attitude determination of relief well and blowout well is the key to improve the drilling efficiency. In this paper, a symmetry multi-coil array-based borehole transient electromagnetic (TEM) system for relative attitude determination of relief well drilling is presented. On the basis of the borehole TEM theory, the multi-coil array weighting is applied to improve the detection performance in the case that the blowout well is parallel to the relief well. Moreover, in order to determine the relative attitude, a symmetrical borehole TEM array structure is proposed for the short-range detection. Experiments were conducted and the results demonstrate the effectiveness of the proposed method for improving the short-range detection performance, which would offer significant information for the tracing phase of relief well drilling.

Determination of Relative Positions of Points Without Establishing Physical Contact With The Object By Concept Of Photogrammetry

Research work done in Terrestrial photogrammetry to calculate and determine various unknown relative positions and parameters of the object. Photogrammetry is one of the surveying concepts of civil engineering to calculate accurate measurements using photographs. Can also be performed without establishing physical contact with the object. Determination of following unknown parameters. The first phase of procedure is: (1.1) Determination of Camera Focal Length. The second phase of procedure is: (2.1) Determination of horizontal distance between the object "A" and the instrument station "M". Second phase also includes (2.2) Determination of horizontal distance between the object "A" and the instrument station "N". The third phase of procedure is: (3.1) Determination of Reduced Level (elevation) of the object point. Initial declaration of pre conditions: The photographs of the object were take from two camera stations M and N with a known measured distance between ground station points "M" and N being 124 meters called as base line. No physical contact was established with the object.

Multi-CubeSat Relative Position and Attitude Determination Based on Array Signal Detection in Formation Flying

High-precision relative position and attitude measurement is crucial for consensus control and collision avoidance in multi-CubeSat formation flying. However, the traditional relative navigation systems comprise many sensors and are not suitable for CubeSats due to large volume, complexity, and cost. In this paper, we propose a new approach, called Multi-CubeSat relative State determination by Array Signal detection (MUSAS). The approach utilizes the existing communication systems and antenna arrays on CubeSats without the need of extra components. In MUSAS, deputy vehicle (DV) CubeSats in a formation broadcast orthogonal spread spectrum signals simultaneously. Two chief vehicle (CV) CubeSats receive and separate the signals and extract the multiple-input multiple-output channel response of each DV CubeSat. Then, by utilizing the bi-directional spatial spectrum estimation, the angles-of-arrival and angles-of-departure of the propagation paths from each DV CubeSat to the CV CubeSats are estimated. Finally, the attitudes and positions of all DV CubeSats relative to the CV CubeSats are determined using the derived rotation matrices. We have theoretically proved the proposed MUSAS algorithm and performed extensive simulations to compare its performance with existing methods. Furthermore, we also developed the testbed of MUSAS and conducted field experiments. The simulation and experiment results have verified that, by exploiting the spread spectrum gain and antenna array gain, MUSAS can achieve high accuracy in relative state determination, even using small antenna arrays and low transmission power.

Abstract P-49: Determination of Relative Positions of Two Helices in Two-Helical Proteins Basing on X-ray Diffraction Data with the Use of Convolutional Neural Networks

Abstract P-49: Determination of Relative Positions of Two Helices in Two-Helical Proteins Basing on X-ray Diffraction Data with the Use of Convolutional Neural Networks

Research on angles-only/SINS/CNS relative position and attitude determination algorithm for a tumbling spacecraft

In this paper, the relative navigation technique of final approach phase for a tumbling target spacecraft is studied and exploited. It is assumed that the tumbling target is in failure or out of control and there is no good a priori rotation rate information. The Euler’s rotational dynamics is used to propagate the target angular velocity, and the unknown inertia parameter circumstance is also considered. The chaser spacecraft is equipped with three strapdown gyros and accelerometers and a star sensor that determine the absolute motion parameters, and an optical camera that measures relative azimuth and elevation angles to the target spacecraft. On the basis of the rotational and translational motions of both spacecrafts, an angles-only/ strapdown inertial navigation system/celestial navigation system navigation filter is designed. Simulation results indicate that the proposed algorithm can accurately estimate the relative position, velocity, and attitude between two spacecrafts and compensate the biases of the gyros and accelerometers.

Determination of relative positions and localizations of paramagnetic probe molecules in liquid crystal by analysis of concentration broadening of EPR spectra

The angular dependences of concentration broadening of EPR spectra for nitroxide spin probes in liquid crystals were experimentally measured. The obvious angular dependence of the broadening found for oriented smectic liquid crystal HOPDOB proves the paired localization of the probe molecules. The numerical calculation of the angular dependence taking into account the magnetic dipolar and spin exchange interactions have been used for quantitative determination of position of probes in the pairs. The probable localization of the probes in the smectic layer is discussed.

Determination of relative position and orientation of nanosatellites by video image analysis

The article discusses the option of using video images to determine the orientation and the position of the second nanosatellite relative to the first one by a series of snapshots made by the first nanosatellite. Optical cameras installed on the first nanosatellite are used as measuring devices. A new approach has been developed to solve the task set. The approach includes an image processing algorithm, a genetic algorithm of differential evolution and a model of motion relative to the center of mass. The approach takes into account the requirements imposed on the nanosatellite hardware that sets limitations on the computational resource of the airborne digital computer and on the quality of images obtained from the optical camera. The developed approach is more economic than similar algorithms. The approach was verified by the benchmark problem of separating two nanosatellites in a short time interval. The dependence of the coordinates of the center of mass of the second satellite on the current orientation and pixel orientation target coordinates in the shot is revealed. The paper includes graphs of the error of determining orientation and position of the center of mass of the second satellite relative to the first one. The approach demonstrates acceptable accuracy in the range of up to 10 seconds for the problem under consideration. The accuracy decreases dramatically as the distance between the two nanosatellites increases.

Line-of-sight based spacecraft attitude and position tracking control

This paper considers the problem of formation control of three spacecraft consisting of one leader and two followers. The leader spacecraft controls its attitude and position to track a desired attitude and position trajectory in the Earth Centred Inertial (ECI) frame. Each follower spacecraft tracks a desired relative attitude and relative position trajectory with respect to the leader spacecraft. Absolute attitude control law for the leader and relative attitude control laws for the followers are obtained in terms of line-of-sight vectors between the spacecraft. A relative attitude determination scheme using line-of-sight vectors is also proposed. The state feedback laws proposed in this work guarantee almost global asymptotic stability of the desired closed-loop equilibrium.

A new semiautomatic device with horizontal developing chamber for gradient thin-layer chromatography

ABSTRACTA new semiautomatic device with two types of horizontal developing chamber for gradient thin-layer chromatography (TLC) that does not require special procedure of chromatographic plate preparation was developed. The new device was applied for separation of test mixture of 10 dyes showing general elution problem. In addition, a general equation for determination of relative position, , of solutes chromatographed under conditions of stepwise gradient elution with one void volume of mobile phase in TLC has been applied. A satisfactory agreement between calculated (by computer program) and experimental values of has been obtained. In the article, based on obtained results, the advantages and disadvantages of different devices for gradient elution in TLC are discussed.

Determination of relative positions and phase angle of dual piezoelectric fans for maximum heat dissipation of fin surface

A three-dimensional computational model for dual piezoelectric fans on the bounded plane has been built using the commercial code CFD-ACE+, and the Levenberg–Marquardt Method (LMM) was used to estimate the optimal relative positions and phase angle of fans for minimizing the average temperature of the fin surface. The dual piezoelectric fans are originally placed in seven different positions (cases 1–7), and the LMM is then utilized to estimate the optimal relative positions and phase angle for increasing the thermal performance of dual piezoelectric fans. The simulations of numerical computations show that for each of the seven original fan arrangements, the optimal relative positions and phase angle of the dual fan are achieved using a singular arrangement in which both fans are located 0.95mm below the center line of the fin and the in-phase operational condition is used. Finally, the temperature distributions of the fin for the original designs of cases 1 and 2 and for the optimal design of case 1 are measured using a thermal camera and are compared with the numerical solutions. The results indicate that the relative errors between numerical and experimental average fin temperatures at 600s for original case 1, original case 2 and optimal case 1 are 0.68%, 0.52% and 0.68%, respectively, thereby validating the estimation method used herein to determine the optimal relative positions and phase angle of dual piezoelectric fans.

Ionosphere influence on success rate of GPS ambiguity resolution in a satellite formation flying

Satellite formation flying is one of the most promising technologies for future space missions. The distribution of sensors and payloads among different satellites provides more redundancy, flexibility, improved communication coverage, among other advantages. One of the fundamental issues in spacecraft formation flying is precise position and velocity determination between satellites. For missions in low Earth orbits, GPS system can meet the precision requirement in relative positioning, since the satellite dynamics is modeled properly. The key for high accuracy GPS relative positioning is to resolve the ambiguities to their integer values. Ambiguities resolved successfully can improve the positioning accuracy to decimetre or even millimetre-level. So, integer carrier phase ambiguity resolution is often a prerequisite for high precision GPS positioning. The determination of relative position was made using an extended Kalman filter. The filter must take into account imperfections in dynamic modeling of perturbations affecting the orbital flight, and changes in solar activity that affects the GPS signal propagation, for mitigating these effects on relative positioning accuracy. Thus, this work aims to evaluate the impact of ionosphere variation, caused by changes in solar activity, in success rate of ambiguity resolution. Using the Ambiguity Dilution of Precision (ADOP) concept, the ambiguity success rate is analyzed and the expected precision of the ambiguity-fixed solution is calculated. Evaluations were performed using actual data from GRACE mission and analyzed for their performance in real scenarios. Analyses were conducted in different configurations of relative position and during different levels of solar activity. Results bring the impact of various disturbances and modeling of solar activity level on the success rate of ambiguity resolution.

Relative position determination between Chang’E-3 lander and rover using in-beam phase referencing

Chang’E-3 is China’s first lunar surface exploration mission, as a part of the second phase of China’s Lunar Exploration Program (CLEP). It landed successfully in the northwest of Mare Imbrium on December 14, 2013, incorporating two probes, a lander and a rover named Yutu. The execution of the cooperative science tasks required an accurate determination of the relative position between the lander and the rover. In-beam phase referencing experiments have been conducted with the Chinese VLBI Network (CVN) to accurately image the rover in reference to the stationary lander in order to obtain their offsets in Right Ascension and Declination, which were then transformed into the lunar local coordinate system to acquire their relative position on the lunar surface. The observations and the data processing procedures are described in this paper. Images of the rover in six epochs between December 15 and 21, 2013 were made, resulting in accurate positions of the rover that are consistent with the visual localization approach. Through measurement of the locations of the rover’s omnidirectional antenna with respect to the lander’s directional antenna before their separation, and the recognition of the rover’s turning actions during its exploratory moves, we demonstrate that the accuracy of relative position determined in this way could reach the meter level and the resolution is better than 1 meter.

Gyro Observability Research of a Relative Attitude Determination System Based on Stereo Vision

The analysis of the observability of system states is very important in the design of an optimal filter estimation algorithm. A relative attitude estimation algorithm is developed based on a stereo vision system and a gyroscope, and the observability of this algorithm is studied. First, we build the error model of the relative attitude determination system. Second, the observability of every state of the filter is studied. Third, by choosing different variables as the states of the error model, the unobservable subspace of the system is confirmed. Furthermore, the system structural decomposition reveals that this type of relative attitude determination system can only determine the relative attitude between the deputy and the chief and that their gyro drift errors are unobservable. In addition, the structural decomposition also tells us that when the feature points measured by the stereo vision system are greater than two, increasing the number of feature points provides little benefit for improving the observability of the gyro drift errors. Considering the incomplete observability of the original system, the star sensor is added into the system to enable it to be completely observable. The final simulation result indicates that after adding the star sensor, the system, which becomes completely observable, can estimate the body attitude, the relative attitude and the gyro error while providing improved accuracy.