scholarly journals Study on Optimal Broadcast Ephemeris Parameters for GEO/IGSO Navigation Satellites

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6544
Author(s):  
Jin Haeng Choi ◽  
Gimin Kim ◽  
Deok Won Lim ◽  
Chandeok Park
Keyword(s):  
Optimal Parameter ◽  
Orbital Plane ◽  
Least Square ◽  
Broadcast Ephemeris ◽  
Curve Fit ◽  
Global Positioning ◽  
Geo Satellites ◽  
Broadcast Ephemeris Parameters ◽  
Orbit Types ◽  
Range Error

This paper proposes new sets of suitable broadcast ephemeris parameters for geosynchronous (GEO) and inclined geosynchronous (IGSO) navigation satellites (NSs). Despite the increasing number of GEO and IGSO NSs, global positioning system (GPS)-type ephemeris parameters are still widely used for them. In an effort to provide higher fit accuracy, we analyze a variety of broadcast ephemeris parameters for GEO and IGSO satellites along with their orbital characteristics and propose optimal sets of parameters. Nonsingular elements and orbital plane rotation are adopted for alleviating/avoiding the singularity issues of GEO satellites. On the basis of 16 parameters of GPS LNAV, we add one to four parameters out of 28 correction ones to determine optimal sets of ephemeris parameters providing higher accuracy. All possible parameter sets are tested with the least-square curve fit for four BeiDou GEOs and six BeiDou IGSOs. Their fit accuracies are compared to determine the optimal broadcast ephemeris parameters that provide minimum fit errors. The set of optimal ephemeris parameters depends on the type of orbit. User range error (URE) accuracies of the proposed optimal ephemeris parameters ensure results within 2.4 cm for IGSO and 3.8 cm for GEO NSs. Moreover, the experimental results present common parameter sets for both IGSO and GEO for compatibility and uniformity. Compared with four conventional/well-known sets of ephemeris parameters for BeiDou, our proposed parameters can enhance accuracies of up to 34.5% in terms of URE. We also apply the proposed optimal parameter sets to one GEO and three IGSO satellites of QZSS. The effects of fitting intervals, number of parameters, total bits, and orbit types on the fit accuracy are addressed in detail.

scholarly journals A Method for Reconstruction of Boiler Combustion Temperature Field Based on Acoustic Tomography

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yuhui Wu ◽  
Xinzhi Zhou ◽  
Li Zhao ◽  
Chenlong Dong ◽  
Hailin Wang
Keyword(s):  
Temperature Field ◽  
Temperature Distribution ◽  
Optimal Parameter ◽  
Interpolation Method ◽  
Least Square Method ◽  
Reconstruction Algorithm ◽  
Least Square ◽  
Temperature Fields ◽  
Acoustic Tomography ◽  
Measured Temperature

Acoustic tomography (AT), as a noninvasive temperature measurement method, can achieve temperature field measurement in harsh environments. In order to achieve the measurement of the temperature distribution in the furnace and improve the accuracy of AT reconstruction, a temperature field reconstruction algorithm based on the radial basis function (RBF) interpolation method optimized by the evaluation function (EF-RBFI for short) is proposed. Based on a small amount of temperature data obtained by the least square method (LSM), the RBF is used for interpolation. And, the functional relationship between the parameter of RBF and the root-mean-square (RMS) error of the reconstruction results is established in this paper, which serves as the objective function for the effect evaluation, so as to determine the optimal parameter of RBF. The detailed temperature description of the entire measured temperature field is finally established. Through the reconstruction of three different types of temperature fields provided by Dongfang Boiler Works, the results and error analysis show that the EF-RBFI algorithm can describe the temperature distribution information of the measured combustion area globally and is able to reconstruct the temperature field with high precision.

Examination and Enhancement of solar radiation pressure model for BDS-3 satellites

2021 ◽  
Author(s):  
Jie Li ◽  
Yongqiang Yuan ◽  
Shi Huang ◽  
Chengbo Liu ◽  
Jiaqing Lou ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
Elevation Angle ◽  
Precise Orbit Determination ◽  
Orbital Plane ◽  
Solar Radiation Pressure ◽  
Earth Orbit ◽  
Precise Orbit ◽  
Orbit Perturbation ◽  
Geo Satellites

<p>With the successful launch of the last Geostationary Earth Orbit (GEO) satellite in June 2020, China has completed the construction of the third generation BeiDou navigation satellites system (BDS-3). BDS-3 global services have been initiated in July 2020 with the constellation of 3 GEO, 3 Inclined Geosynchronous Orbit (IGSO) and 24 Medium Earth Orbit (MEO) satellites. In order to further improve the performance of BDS-3 services, the quality of BDS-3 precise orbit product needs further enhancements.</p><p>       The solar radiation pressure (SRP) is the main non-conservative orbit perturbation for GNSS satellites and is the key to improve BDS-3 precise orbit determination. In this study, we focus on the SRP models for BDS-3 satellites. Firstly, the widely used Extended CODE Orbit Model with five parameters (ECOM-5) is assessed. With one-year observations of 2020 from both iGMAS and MGEX networks, the five parameters of ECOM model (D0, Y0, B0, Bc and Bs) are estimated for each BDS-3 satellite. The D0 estimates show an obvious dependency on the elevation angle of the Sun above the satellite orbital plane (denoted as β). In addition, large variations can be noticed in eclipse seasons, which indicate the dramatic changes of SRP. The Y0 estimates vary from -0.6 nm/s<sup>2</sup> to 0.6 nm/s<sup>2</sup> for MEO, -1.0 to 1.0 nm/s<sup>2</sup> for IGSO and -1.0 to 1.5 nm/s<sup>2</sup> for GEO satellites. The B0 estimates of several satellites exhibit a clear dependency on the β angle. The largest variation of B0 appears at C45 and C46, changing from 1.0 nm/s<sup>2</sup> at 15 deg to 8.3 nm/s<sup>2</sup> at 64 deg, which implies that the solar panels of these two satellites may have an obvious rotation lag. To compensate the deficiencies of BDS-3 SRP modeling, we introduce several additional parameters into ECOM-5 model (e.g. introducing higher harmonic terms). The POD performances can be improved by about 10% and 40% for BDS-3 MEO/IGSO and GEO satellites, respectively.</p><p>       Except for the empirical model, we also study the semi-empirical SRP model such as the a priori box-wing model. Since the geometrical and optical properties from BDS-3 metadata are general and rough, we apply more detailed geometrical and optical coefficients for BDS-3 satellites. The POD performance can be improved by about 10% compared to empirical SRP models. Furthermore, considering Earth radiation pressure will have an impact of about 1.3 cm in radial component for MEO satellites.</p>

scholarly journals Analysis of Factors Affecting Asynchronous RTK Positioning with GNSS Signals

2019 ◽  
Vol 11 (10) ◽  
pp. 1256
Author(s):  
Shu ◽  
Liu ◽  
Feng ◽  
Xu ◽  
Qian ◽  
...  
Keyword(s):  
Satellite Orbit ◽  
Latency Time ◽  
Short Baseline ◽  
Factors Affecting ◽  
Broadcast Ephemeris ◽  
Geo Satellites ◽  
Short Baselines ◽  
Broadcast Orbit ◽  
Different Characteristics ◽  
Clock Offset

For short baseline real-time kinematic (RTK) positioning, the atmosphere and broadcast ephemeris errors can be usually eliminated in double-differenced (DD) processing for synchronous observations. However, in the case of possible communication latency time, these errors may not be eliminated in DD treatments due to their variations during latency time. In addition, the time variation of these errors may present different characteristics among GPS, GLONASS, BDS, and GALILEO due to different satellite orbit and clock types. In this contribution, the formulas for studying the broadcast orbit and clock offset errors and atmosphere error in asynchronous RTK (ARTK) model is proposed, and comprehensive experimental analysis is performed to numerically show time variations of these errors and their impacts on RTK results from short-baselines among four systems. Compared with synchronous RTK, the degradation of position precision for ARTK can reach a few centimeters, but the accuracy degradation to a different degree by different systems. BDS and Galileo usually outperform GPS and GLONASS in ARTK due to the smaller variation of broadcast ephemeris error. The variation of broadcast orbit error is generally negligible compared with the variation of broadcast clock offset error for GPS, BDS, and Galileo. Specifically, for a month of data, the root mean square (RMS) values for the variation of broadcast ephemeris error over 15 seconds are 11.2, 16.9, 7.3, and 3.0 mm for GPS, GLONASS, BDS, and Galileo, respectively. The variation of ionosphere error for some satellites over 15 seconds can reach a few centimeters during active sessions under a normal ionosphere day. In addition, compared with other systems, BDS ARTK shows an advantage under high ionosphere activity, and such advantage may be attributed to five GEO satellites in the BDS constellation.

scholarly journals A Novel Shearer Cutting State Recognition Method Based on Improved Variational Mode Decomposition and LSSVM with Acoustic Signals

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Zhongbin Wang ◽  
Bin Liang ◽  
Lei Si ◽  
Kuangwei Tong ◽  
Chao Tan
Keyword(s):  
Search Algorithm ◽  
Optimal Parameter ◽  
Gravitational Search Algorithm ◽  
Principal Component ◽  
Least Square ◽  
Support Vector ◽  
Variational Mode Decomposition ◽  
Intrinsic Mode Functions ◽  
Recognition Method ◽  
Mode Decomposition

The recognition of shearer cutting state is the key technology to realize the intelligent control of the shearer, which has become a highly difficult subject concerned by the world. This paper takes the sound signal as analytic objects and proposes a novel recognition method based on the combination of variational mode decomposition (VMD), principal component analysis method (PCA), and least square support vector machine (LSSVM). VMD can decompose a signal into various modes by using calculus of variation and effectively avoid the false component and mode mixing problems. On this basis, an improved gravitational search algorithm (IGSA) is designed by using the position update mechanism of Levy flight strategy to find the optimal parameter combination of VMD. Then, the feature extraction is achieved by calculating the envelope entropy and kurtosis of the decomposed intrinsic mode functions (IMFs). To avoid dimensional disasters and reinforce the classification performance, PCA is introduced to choose useful features, and the LSSVM-based classifier is reasonably constructed. Finally, the experimental results indicate that the proposed method is more feasible and superior in the recognition of shearer cutting states.

scholarly journals Geometric Interpretation of Errors in Multi-Parametrical Fitting Methods Based on Non-Euclidean Norms

Stats ◽  
2019 ◽  
Vol 2 (4) ◽  
pp. 426-438 ◽  
Author(s):  
Livadiotis
Keyword(s):  
Optimal Parameter ◽  
Least Square Method ◽  
Geometric Interpretation ◽  
Least Square ◽  
Geometric Representation ◽  
Geometric Meaning ◽  
Normal Equations ◽  
Optimal Values ◽  
Parameter Values ◽  
Fitting Parameters

The paper completes the multi-parametrical fitting methods, which are based on metrics induced by the non-Euclidean Lq-norms, by deriving the errors of the optimal parameter values. This was achieved using the geometric representation of the residuals sum expanded near its minimum, and the geometric interpretation of the errors. Typical fitting methods are mostly developed based on Euclidean norms, leading to the traditional least–square method. On the other hand, the theory of general fitting methods based on non-Euclidean norms is still under development; the normal equations provide implicitly the optimal values of the fitting parameters, while this paper completes the puzzle by improving understanding the derivations and geometric meaning of the optimal errors.

A Satellite Ephemeris Correction Calculating Algorithm Based on the Hill Differential Equation

2013 ◽  
Vol 336-338 ◽  
pp. 1682-1687
Author(s):  
Rui Bin Zhao ◽  
Bo Shao ◽  
Rui Li ◽  
Zhi Gang Huang
Keyword(s):  
Differential Equation ◽  
Kalman Filter ◽  
Coordinate System ◽  
Engineering Application ◽  
Velocity Model ◽  
Least Square ◽  
Current Time ◽  
Calculation Algorithms ◽  
Geo Satellites ◽  
The Hill

The Hill differential equation is used to describe the change characteristic of the ephemeris prediction error in order to calculate the satellite broadcast ephemeris error and the error change rate. After the ECEF coordinate system converses the satellite inertial coordinate system, both the satellite ephemeris correction and the correction accuracy can be calculated by the Kalman filter. When the GEO, IGSO and MEO satellites move over the China, the calculation algorithms based on the weighted least square, the velocity model of the Kalman filter and the Hill differential equation are compared in the computing performance of the ephemeris corrections by using the reference date of IGS website. The simulation results show that: the ephemeris correction solver value based on the Hill differential equation can accurately reflect the ephemeris error characteristics at the current time. And it is able to correctly reflect the perturbation impact for the satellite ephemeris error. The Hill differential equation method is more suitable at the master station for engineering application about the MEO, IGSO and GEO satellites.

scholarly journals Optimal GPS Satellite Selection using Stochastic Optimization and Volumes of Tetrahedrons for High Precision Positioning

2020 ◽  
Vol 9 (11) ◽  
pp. 60-65
Keyword(s):  
Error Modeling ◽  
Gps Navigation ◽  
Position Accuracy ◽  
Global Positioning ◽  
Satellite Selection ◽  
Satellite Geometry ◽  
Considerable Impact ◽  
Range Error ◽  
Work Done ◽  
Selection Of

A possibility of utilizing the Global Positioning System (GPS) depends on the positioning accuracy. Two decisive factors of position accuracy are User Range Error (URE) value and dimensionless Dilution of Precision (DOP), related to number of visible satellites. Several error modeling and correction techniques are available to improve the accuracy by optimizing the errors. While finding the GDOP at every instant, satellite selection plays predominant role. Satellite geometry with more satellites gives the good GDOP. However, due to limited receiver tracking channels and smaller size memories and other problems, it may not be possible to use all satellites in view for positioning. In GPS navigation, position of user requires minimum of four visible satellites. The selection of four satellites has a considerable impact on the position accuracy and GDOP shows the order of this impact. By using the concept of relation between GDOP and volume of tetrahedron optimal four satellites are selected to improve the position accuracy. Genetic Algorithm is used to select best ten combinations based on GDOP. For experimental validation the data collected at Andhra University, Visakhapatnam, located at (706970.9093, 6035941.0226, 1930009.5821) (m) is used. It is observed that selected satellites which are arranged in tetrahedron by following the work done by M Kihara on satellite selection method and accuracy for the GPS, using GA gives the best position values.

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