Multivariate Constrained GNSS Real-time Full Attitude Determination Based on Attitude Domain Search

2018 ◽  
Vol 72 (2) ◽  
pp. 483-502
Author(s):  
Hongtao Wu ◽  
Xiubin Zhao ◽  
Chunlei Pang ◽  
Liang Zhang ◽  
Bo Feng
Keyword(s):  
Objective Function ◽  
Success Rate ◽  
High Efficiency ◽  
Attitude Determination ◽  
A Priori ◽  
Three Dimensional ◽  
Satellite System ◽  
New Method ◽  
Lambda Method ◽  
Attitude Angle

A priori attitude information can improve the success rate and reliability of Global Navigation Satellite System (GNSS) multi-antennae attitude determination. However, a priori attitude information is nonlinear, and integrating a priori information into the objective function rigorously will increase the complexity of an ambiguity domain search, such as the Multivariate Constrained-Least-squares Ambiguity Decorrelation Adjustment (MC-LAMBDA) method. In this paper, a new method based on attitude domain search is presented to make use of the a priori attitude angle information with high efficiency. First, the a priori information of pitch and roll is integrated into the search process to derive the analytic search step for attitude angle, and the integer candidates are determined by traversal search in the three-dimensional attitude domain. Then, the objective function is parameterised with Euler angles, and a non-iterative approximate method is utilised to simplify the iterative computation in calculating objective function values. Experimental results reveal that compared to the MC-LAMBDA method, our new method has the same success rate and reliability, but higher efficiency in making use of a priori attitude information.

An Enhanced Multi-GNSS Navigation Algorithm by Utilising a Priori Inter-System Biases

2017 ◽  
Vol 71 (2) ◽  
pp. 339-351 ◽  
Author(s):  
Zhounan Dong ◽  
Changsheng Cai ◽  
Rock Santerre ◽  
Cuilin Kuang
Keyword(s):  
Moving Average ◽  
A Priori ◽  
Three Dimensional ◽  
Main Idea ◽  
Experimental Tests ◽  
Satellite Observation ◽  
Satellite System ◽  
Estimation Algorithms ◽  
Navigation Algorithm ◽  
Sky Conditions

The integration of multi-constellation Global Navigation Satellite System (GNSS) measurements can effectively improve the accuracy and reliability of navigation and positioning solutions, while the Inter-System Bias (ISB) is a key issue for compatibility. The ISB is traditionally estimated as an unknown parameter along with three-dimensional position coordinates and a receiver clock offset with respect to Global Positioning System (GPS) time. ISB estimation of this sort will sacrifice a satellite observation for each integrated GNSS system. These sacrificed observations could be vital in situations of limited satellite visibility. In this study, an enhanced multi-GNSS navigation algorithm is developed to avoid sacrificing observations under poor visibility conditions. The main idea of this algorithm is to employ a moving average filter to smooth the ISBs estimated at previous epochs. The filtered value is utilised as a priori information at the current epoch. Experimental tests were conducted to evaluate the enhanced algorithm under open and blocked sky conditions. The results show that the enhanced algorithm effectively improves the accuracy and availability of navigation solutions under the blocked sky condition, with performance being comparable to traditional ISB estimation algorithms in open sky conditions. The improvement rates of the three-dimensional position accuracy and availability reach up to 63% and 21% in the blocked sky environment. Even in the case of only four different GNSS satellites, a position solution can still be obtained using the enhanced algorithm.

Influencing Factors of GNSS Differential Inter-System Bias and Performance Assessment of Tightly Combined GPS, Galileo, and QZSS Relative Positioning for Short Baseline

2018 ◽  
Vol 72 (04) ◽  
pp. 965-986 ◽  
Author(s):  
Mingkui Wu ◽  
Xiaohong Zhang ◽  
Wanke Liu ◽  
Renpan Wu ◽  
Renlan Zhang ◽  
...  
Keyword(s):  
Success Rate ◽  
Influencing Factors ◽  
A Priori ◽  
Satellite System ◽  
Single Frequency ◽  
Relative Positioning ◽  
Combined Model ◽  
Short Baseline ◽  
System Bias ◽  
The Impact

This paper first investigates the influencing factors of between-receiver Differential Inter-System Bias (DISB) between overlapping frequencies of the Global Positioning System (GPS), Galileo and the Quasi-Zenith Satellite System (QZSS). It was found that the receiver reboot and the type of observations may have an impact on DISBs. The impact of receiver firmware upgrades and the activation of anti-multipath filters are also investigated and some new results are presented. Then a performance evaluation is presented of tightly combined relative positioning for a short baseline with GPS/Galileo/QZSS L1-E1-L1/L5-E5a-L5 observations with the current constellations, in which the recently launched Galileo and QZSS satellites will also be included. It is demonstrated that when DISBs are a priori calibrated and corrected, the tightly combined model can deliver a much higher empirical ambiguity resolution success rate and positioning accuracy with respect to the classical loosely combined model, especially under environments where the observed satellites for each system are limited and only single-frequency observations are available. The ambiguity dilution of precision, bootstrapping success rate, and ratio values are analysed to illustrate the benefits of the tightly combined model as well.

Attitude Angle Measurement Method Based on the Three-Dimensional Accelerometer

2013 ◽  
Vol 333-335 ◽  
pp. 152-156
Author(s):  
Yu Fa Tang ◽  
He Zhang ◽  
Li Hong
Keyword(s):  
Circuit Design ◽  
Inclination Angle ◽  
Attitude Determination ◽  
Three Dimensional ◽  
Angle Measurement ◽  
Two Dimensional ◽  
Theoretical Support ◽  
Attitude Angle ◽  
Hardware Circuit

On the basis of a study of measuring inclination angle with a two-dimensional accelerometer, a principle method using a three-dimensional accelerometer to measure attitude angle is analysed on the condition of micro-rotating. The method can reduce random systematic errors caused by uniaxial or biaxial output of the two-dimensional accelerometer. It can simultaneously measure both inclination angle and roll angle. So hardware selection, hardware circuit design and experiments are done: simulate the roll and tilt movement of the special objects and compare the solver results with the actual results. The principle method achieves preferable results, and provides a theoretical support for attitude determination of a particular industry as well.

Objective Function Effect Based Pattern Search—Theoretical Framework Inspired by 3D Component Layout

2006 ◽  
Vol 129 (3) ◽  
pp. 243-254 ◽  
Author(s):  
Chandankumar Aladahalli ◽  
Jonathan Cagan ◽  
Kenji Shimada
Keyword(s):  
Objective Function ◽  
A Priori ◽  
Three Dimensional ◽  
Parameter Tuning ◽  
Search Algorithms ◽  
Pattern Search ◽  
Function Change ◽  
Component Layout ◽  
Novel Method ◽  
Treat All

Though pattern search algorithms have been successfully applied to three-dimensional (3D) component layout problems, a number of unanswered questions remain regarding their parameter tuning. One such question is the scheduling of patterns in the search. Current pattern search methods treat all patterns similarly and all of them are active from the beginning to the end of the search. Observations from 3D component layout motivate the question whether patterns should be introduced in some different order during the search. This paper presents a novel method for scheduling patterns that is inspired by observations from 3D component layout problems. The new method introduces patterns into the search in the decreasing order of a priori expectation of the objective function change due to the patterns. Pattern search algorithms based on the new pattern schedule run 30% faster on average than conventional pattern search based algorithms on 3D component layout problems and general 2D multimodal surface minimization problems. However since determining the expected change in objective function value due to the patterns is expensive, we explore approximations using domain information.

scholarly journals A Triple Checked Partial Ambiguity Resolution for GPS/BDS RTK Positioning

Sensors ◽  
2019 ◽  
Vol 19 (22) ◽  
pp. 5034
Author(s):  
Lu ◽  
Ma ◽  
Liu ◽  
Wu ◽  
Chen
Keyword(s):  
Success Rate ◽  
Ambiguity Resolution ◽  
Satellite System ◽  
Ratio Test ◽  
Fixed Rate ◽  
Partial Ambiguity Resolution ◽  
Lambda Method ◽  
Fast Development ◽  
Global Navigation Satellite ◽  
Carrier Phase Ambiguity

Reliable and accurate carrier phase ambiguity resolution is the key to high-precision Global Navigation Satellite System (GNSS) positioning and application. With the fast development of modern GNSS, the increased number of satellites and ambiguities makes it hard to fix all ambiguities completely and correctly. The partial ambiguity fixing technique, which selects a suitable subset of high-dimensional ambiguities to fix, is beneficial for improving the fixed success rate and reliability of ambiguity resolution. In this contribution, the bootstrapping success rate, bounded fixed-failure ratio test, and the new defined baseline precision defect are used for the selection of the ambiguity subset. Then a model and data dual-driven partial ambiguity resolution method is proposed with the above three checks imposed on it, which is named the Triple Checked Partial Ambiguity Resolution (TC-PAR). The comprehensive performance of TC-PAR compared to the full-fixed LAMBDA method is also analyzed based on several criteria including the fixed rate, the fixed success rate and correct fixed rate of ambiguity as well as the precision defect and RMS of the baseline solution. The results show that TC-PAR could significantly improve the fixed success rate of ambiguity, and it has a comparable baseline precision to the LAMBDA method, both of which are at centimeter level after ambiguities are fixed.

Finite Element Modeling for Steel Cord Analysis in Radial Tires

2013 ◽  
Vol 41 (1) ◽  
pp. 60-79 ◽  
Author(s):  
Wei Yintao ◽  
Luo Yiwen ◽  
Miao Yiming ◽  
Chai Delong ◽  
Feng Xijin
Keyword(s):  
Finite Element ◽  
High Efficiency ◽  
Force Measurement ◽  
Three Dimensional ◽  
Local Stress ◽  
Tension Force ◽  
Center Line ◽  
Element Analysis ◽  
Design Variables ◽  
Steel Cord

ABSTRACT: This article focuses on steel cord deformation and force investigation within heavy-duty radial tires. Typical bending deformation and tension force distributions of steel reinforcement within a truck bus radial (TBR) tire have been obtained, and they provide useful input for the local scale modeling of the steel cord. The three-dimensional carpet plots of the cord force distribution within a TBR tire are presented. The carcass-bending curvature is derived from the deformation of the carcass center line. A high-efficiency modeling approach for layered multistrand cord structures has been developed that uses cord design variables such as lay angle, lay length, and radius of the strand center line as input. Several types of steel cord have been modeled using the developed method as an example. The pure tension for two cords and the combined tension bending under various loading conditions relevant to tire deformation have been simulated by a finite element analysis (FEA). Good agreement has been found between experimental and FEA-determined tension force-displacement curves, and the characteristic structural and plastic deformation phases have been revealed by the FE simulation. Furthermore, some interesting local stress and deformation patterns under combined tension and bending are found that have not been previously reported. In addition, an experimental cord force measurement approach is included in this article.

Shape Optimization of Hydraulic Structures: an Example of an Optimum Design of a Fish Passage

10.29007/2k64 ◽  
2018 ◽  
Author(s):  
Pat Prodanovic ◽  
Cedric Goeury ◽  
Fabrice Zaoui ◽  
Riadh Ata ◽  
Jacques Fontaine ◽  
...  
Keyword(s):  
Numerical Model ◽  
Shape Optimization ◽  
Objective Function ◽  
Optimum Design ◽  
Optimization Problem ◽  
A Priori ◽  
Coupled System ◽  
Fish Passage ◽  
Hydraulic Structures ◽  
Design Variables

This paper presents a practical methodology developed for shape optimization studies of hydraulic structures using environmental numerical modelling codes. The methodology starts by defining the optimization problem and identifying relevant problem constraints. Design variables in shape optimization studies are configuration of structures (such as length or spacing of groins, orientation and layout of breakwaters, etc.) whose optimal orientation is not known a priori. The optimization problem is solved numerically by coupling an optimization algorithm to a numerical model. The coupled system is able to define, test and evaluate a multitude of new shapes, which are internally generated and then simulated using a numerical model. The developed methodology is tested using an example of an optimum design of a fish passage, where the design variables are the length and the position of slots. In this paper an objective function is defined where a target is specified and the numerical optimizer is asked to retrieve the target solution. Such a definition of the objective function is used to validate the developed tool chain. This work uses the numerical model TELEMAC- 2Dfrom the TELEMAC-MASCARET suite of numerical solvers for the solution of shallow water equations, coupled with various numerical optimization algorithms available in the literature.

scholarly journals Construction of the Cellulose Nanofibers (CNFs) Aerogel Loading TiO2 NPs and Its Application in Disposal of Organic Pollutants

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1841
Author(s):  
Kang Li ◽  
Xuejie Zhang ◽  
Yan Qin ◽  
Ying Li
Keyword(s):  
High Efficiency ◽  
Sol Gel ◽  
Cellulose Nanofibers ◽  
Three Dimensional ◽  
Good Mechanical Property ◽  
Polar Groups ◽  
Dimensional Network ◽  
Natural Polysaccharide ◽  
Valuable Method ◽  
Adsorption Capability

Aerogels have been widely used in the adsorption of pollutants because of their large specific surface area. As an environmentally friendly natural polysaccharide, cellulose is a good candidate for the preparation of aerogels due to its wide sources and abundant polar groups. In this paper, an approach to construct cellulose nanofibers aerogels with both the good mechanical property and the high pollutants adsorption capability through chemical crosslinking was explored. On this basis, TiO2 nanoparticles were loaded on the aerogel through the sol-gel method followed by the hydrothermal method, thereby the enriched pollutants in the aerogel could be degraded synchronously. The chemical cross-linker not only helps build the three-dimensional network structure of aerogels, but also provides loading sites for TiO2. The degradation efficiency of pollutants by the TiO2@CNF Aerogel can reach more than 90% after 4 h, and the efficiency is still more than 70% after five cycles. The prepared TiO2@CNF Aerogels have high potential in the field of environmental management, because of the high efficiency of treating organic pollutes and the sustainability of the materials. The work also provides a choice for the functional utilization of cellulose, offering a valuable method to utilize the large amount of cellulose in nature.

Sign in / Sign up

Export Citation Format

Share Document