scholarly journals The Benefits of Receiver Clock Modelling in Satellite Timing

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 466
Author(s):  
Weijin Qin ◽  
Xiao Wang ◽  
Hang Su ◽  
Zhe Zhang ◽  
Xiao Li ◽  
...  
Keyword(s):  
White Noise ◽  
Noise Model ◽  
Kinematic Scheme ◽  
Clock Model ◽  
Average Improvement ◽  
Receiver Clock ◽  
Averaging Time ◽  
Stochastic Clock ◽  
Clock Offset ◽  
Sampling Times

Satellite timing is an effective and convenient method that has been widely accepted in the time community. The key to satellite timing is obtaining a clean receiver clock offset. In this paper, instead of regarding the receiver clock offset as white noise, a two-state stochastic clock model involving three kinds of noise was conceived and used in PPP filter estimation. The influence of clock type and sampling time on satellite timing performance was first analysed. In addition, the kinematic scheme and static scheme were both investigated for meeting the demands of multi-occasional users. The values show that the model works well for both the kinematic scheme and static scheme; in contrast to that of the white noise model, the timing stability is enhanced at all the sampling times. For the six stations, especially when the averaging time is less than 1000 s, the average stability improvement values of the kinematic scheme are 75.53, 43.24, 75.00, 69.05, 40.57, and 25.45%, and the average improvement values of the static scheme are 65.49, 77.94, 56.71, 60.78, 64.41, and 39.41%. Furthermore, the enhancement magnitude is related to clock type. For a high-stability clock, the improvement of the kinematic scheme is greater than that of the static scheme, whereas for a low-stability clock, the improvement of the kinematic scheme is less than that of the static scheme.

scholarly journals Performance of Multi-GNSS Precise Point Positioning Time and Frequency Transfer with Clock Modeling

2019 ◽  
Vol 11 (3) ◽  
pp. 347 ◽  
Author(s):  
Yulong Ge ◽  
Peipei Dai ◽  
Weijin Qin ◽  
Xuhai Yang ◽  
Feng Zhou ◽  
...  
Keyword(s):  
White Noise ◽  
Precise Point Positioning ◽  
Noise Model ◽  
Single System ◽  
Time Transfer ◽  
Receiver Clock ◽  
Maximum Improvement ◽  
Frequency Transfer ◽  
White Noise Model ◽  
Point Positioning

Thanks to the international GNSS service (IGS), which has provided multi-GNSS precise products, multi-GNSS precise point positioning (PPP) time and frequency transfer has of great interest in the timing community. Currently, multi-GNSS PPP time transfer is not investigated with different precise products. In addition, the correlation of the receiver clock offsets between adjacent epochs has not been studied in multi-GNSS PPP. In this work, multi-GNSS PPP time and frequency with different precise products is first compared in detail. A receiver clock offset model, considering the correlation of the receiver clock offsets between adjacent epochs using an a priori value, is then employed to improve multi-GNSS PPP time and frequency (scheme2). Our numerical analysis clarify how the approach performs for multi-GNSS PPP time and frequency transfer. Based on two commonly used multi-GNSS products and six GNSS stations, three conclusions are obtained straightforwardly. First, the GPS-only, Galileo-only, and multi-GNSS PPP solutions show similar performances using GBM and COD products, while BDS-only PPP using GBM products is better than that using COD products. Second, multi-GNSS time transfer outperforms single GNSS by increasing the number of available satellites and improving the time dilution of precision. For single-system and multi-GNSS PPP with GBM products, the maximum improvement in root mean square (RMS) values for multi-GNSS solutions are up to 7.4%, 94.0%, and 57.3% compared to GPS-only, BDS-only, and Galileo-only solutions, respectively. For stability, the maximum improvement of multi-GNSS is 20.3%, 84%, and 45.4% compared to GPS-only, BDS-only and Galileo-only solutions. Third, our approach contains less noise compared to the solutions with the white noise model, both for the single-system model and the multi-GNSS model. The RMS values of our approach are improved by 37.8–91.9%, 10.5–65.8%, 2.7–43.1%, and 26.6–86.0% for GPS-only, BDS-only, Galileo-only, and multi-GNSS solutions. For frequency stability, the improvement of scheme2 ranges from 0.2 to 51.6%, from 3 to 80.0%, from 0.2 to 70.8%, and from 0.1 to 51.5% for GPS-only, BDS-only, Galileo-only, and multi-GNSS PPP solutions compared to the solutions with the white noise model in the Eurasia links.

scholarly journals Empirical Bayes scaling of Gaussian priors in the white noise model

2013 ◽  
Vol 7 (0) ◽  
pp. 991-1018 ◽  
Author(s):  
B. T. Szabó ◽  
A. W. van der Vaart ◽  
J. H. van Zanten
Keyword(s):  
White Noise ◽  
Empirical Bayes ◽  
Noise Model ◽  
White Noise Model

A new physical parameter identification method for shear frame structures under limited inputs and outputs

2020 ◽  
pp. 136943322096373
Author(s):  
Jing-Liang Liu ◽  
An-Hua Yu ◽  
Chia-Ming Chang ◽  
Wei-Xin Ren ◽  
Jing Zhang
Keyword(s):  
Parameter Identification ◽  
White Noise ◽  
Particle Filter ◽  
Physical Parameter ◽  
Experimental Test ◽  
Gaussian White Noise ◽  
Noise Model ◽  
Frame Structures ◽  
Structural System ◽  
Shear Frame

A new physical parameter identification method with a name of EKPF-LS is proposed for shear frame structures under limited inputs and outputs by a combination of extended Kalman particle filter (EKPF) and least square (LS) algorithm. The basic principle of EKPF-LS is to establish the proposed distribution function of the particle filter through EKF-LS. In this method, EKPF is introduced to get rid of the restriction of Gaussian white noise model and reduce the linearization error caused by EKF. Meanwhile, LS is utilized to address the problem of unmeasured excitation estimations. The effectiveness and accuracy of the proposed EKPF-LS method is verified by a numerical example of a four-story hysteretic shear frame under an earthquake excitation and an experimental test of a four-story shear type frame using Gaussian white noise and sine sweep signal as excitations, respectively. Gaussian colored noises are then added to the solved and measured response signals in the numerical example and experimental test, respectively. The results demonstrate that the proposed method can identify the stiffness of shear frame structures effectively and is superior to the existed EKF-LS approach when the structural system is nonlinear structural system or Colored noise model.

Experimental study on effect of side-mooring lines on dynamics of a catenary moored semi-submersible system

2019 ◽  
Vol 234 (1) ◽  
pp. 127-142
Author(s):  
Sheng Xu ◽  
Chun-yan Ji ◽  
C Guedes Soares
Keyword(s):  
White Noise ◽  
Model Tests ◽  
Noise Model ◽  
Floating Platform ◽  
Mooring Lines ◽  
Motion Response ◽  
Free Decay ◽  
Wave Basin ◽  
White Noise Model ◽  
Response Amplitude Operators

In this article, a novel mooring system with side-mooring lines is proposed for a traditional shape semi-submersible platform with four columns. To obtain the dynamics of moored system, model tests were carried out at a wave basin, including free-decay model tests, white noise model tests and irregular model tests. The natural periods in heave, roll and pitch models were measured and compared with numerical results. The motion response amplitude operators under 90° and 135° waves were obtained from white noise model tests and then compared with numerical simulations. A 100-year sea state in South China Sea was simulated in the wave basin by the JONSWAP spectrum, and the 6-degree-of-freedom motion responses of semi-submersible and mooring tensions were recorded in beam and quartering seas. The effects of the side-mooring lines on the floating platform motion response, mooring tensions and mooring fatigue damage are evaluated by comparing the results with and without side-mooring lines installed.

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