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第十三届中国卫星导航年会

作者： Fujian Ma Jinjun Zheng Chengbin Kang Qiuli Chen Ping Li Xin Nie Xiaohong Zhang Institute of Telecommunication and Navigation Satellites China Academy of Space Technology Chinese Antarctic Center of Surveying and Mapping Wuhan University

Compared with BeiDou satellites, low earth orbit（LEO） satellites travel faster and show greater changes in spatial geometry within the same duration. When they are served as navigation satellites and assist BDS precise point positioning（PPP）, fast initialization can be realized. Usually, the geometry of a constellation is represented by the geometric dilution of precision（GDOP）. However, traditional GDOP metric can only reflect the instantaneous positioning accuracy of standard navigation and positioning service rather than the convergence performance of PPP, and cannot be calculated when the number of instantaneous visible satellites is less than 4. Considering that the coverage fold of future LEO navigation-augmentation constellation may be below 4 and meanwhile it is meaningful to comprehensively describe the continuous impacts of satellite numbers, moving velocity, moving direction and geometric change level on the convergence process of PPP, the concept of equivalent GDOP（EGDOP） based on accumulated time is proposed. Then, thousands of LEO constellations and their observation data are simulated and used for the analysis of the relationship between the EGDOP of LEO constellation and the convergence time of LEO-augmented BDS PPP. The results show that for 1-min sessions the smaller the EGDOP, the shorter the convergence time and the higher the probability that PPP converge within 1 min. Under ideal ephemeris conditions, the probabilities of realizing fast PPP with the horizontal positioning accuracy better than 10 cm and convergence time below 1 min are 100%, 95% and 65% when the corresponding EGDOP are below 0.29, 0.30 and 0.51, respectively. The relevant results can be used as an important basis for the optimization design of future LEO navigation-augmentation constellations.

关键词： Equivalent GDOP LEO constellation LEO-augmented BDS PPP convergence time

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LEO Enhanced Global Navigation Satellite System(LeGNSS):progress,opportunities,and challenges

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Geo-Spatial Information Science 2022年第1期25卷 1-13页

作者： Haibo Ge Bofeng Li Song Jia Liangwei Nie Tianhao Wu Zhe Yang Jingzhe Shang Yanning Zheng Maorong Ge College of Surveying and Geo-Informatics Tongji UniversityShanghaiChina Department of Geodesy GeoForschungsZentrum(GFZ)TelegrafenbergPotsdamGermany

With the completion of Chinese BeiDou Navigation Satellite System(BDS),the world has begun to enjoy the Positioning,Navigation,and Timing(PNT)services of four Global Navigation Satellite Systems(GNSS).In order to improve the GNSS performance and expand its applications,Low Earth Orbit(LEO)Enhanced Global Navigation Satellite System(LeGNSS)is being vigorously *** with high-,medium-,and low-earth orbit satellites,it can improve GNSS performance in terms of orbit determination,Precise Point Positioning(PPP)convergence time,*** paper comprehensively reviews the current status of LeGNSS,focusing on analyzing its advantages and challenges for precise orbit and clock determination,PPP convergence,earth rotation parameter estimation,and global ionosphere *** to the fast geometric change brought by LEO satellites,LeGNSS is expected to fundamentally solve the problem of the long convergence time of PPP without any *** convergence time can be shortened within 1 minute if appropriate LEO constellations are ***,there are still some issues to overcome,such as the optimization of LEO constellation as well as the real time LEO precise orbit and clock determination.

关键词： LEO Enhanced Global Navigation Satellite System(LeGNSS) orbit determination Precise Point Positioning(PPP) convergence time global ionosphere modeling

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Comprehensive assessment of real-time precise products from IGS analysis centers

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Satellite Navigation 2022年第1期3卷 97-113,I0004页

作者： Bofeng Li Haibo Ge Yuhang Bu Yanning Zheng Leitong Yuan College of Surveying and GeoInformatics Tongji UniversityShanghai 200092China

Real-time Precise Point Positioning(RT-PPP)has been one of the research hotspots in GNSS(Global Navigation Satellite System)community for ***-time precise products of satellite orbits and clocks are the prerequisite for ***,it is of great importance to investigate the current multi-GNSS real-time precise products in State Space Representation(SSR)from diferent analysis *** this article,SSR products from 10 analysis centers are comprehensively evaluated by comparing them with the fnal products and performing the kinematic *** results show that analysis centers CNES(Centre National D’Etudes Spatiales)and WHU(GNSS Research Center of Wuhan University)provide the most complete products with the best *** the accuracy of real-time products for the GNSSs,the accuracies of orbit and clock products are better than 5 cm and 0.15 ns,respectively,for Global Positioning System(GPS),followed by Galileo navigation satellite system(Galileo),BeiDou-3 Navigation Satellite System(BDS-3),GLObal NAvigation Satellite System(GLONASS),and BeiDou-2 Navigation Satellite System(BDS-2).Meanwhile,the results of the RT-PPP with quad-system show that the positioning accuracies are 1.76,1.12 and 2.68 cm in east,north,and up directions,respectively,and the convergence time to 0.1,0.1,0.2 m for corresponding directions is 15.35 min.

关键词： Real-time precise point positioning(RT-PPP) State space representation(SSR) Multi-GNSS convergence time

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A modified code tracking loop based on dual structure

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Science China(Information Sciences) 2015年第8期58卷 77-86页

作者： WANG Pai WANG YongQing WU SiLiang Department of Information and Electronics Beijing Institute of Technology

A modified code tracking loop for tracking the pseudo-random noise code in direct sequence spread spectrum signal is proposed. The modified loop differs from the typical through imposing a dual structure which incorporates a coarse loop with large loop parameters and an accurate loop with small loop parameters. The expression of the convergence time for the second-order delay-locked loop(DLL) is derived to measure the time of the convergence process. Two concepts, accuracy improvement and time improvement are defined to exhibit the performance enhancement of the modified loop. Simulation results show that the proposed method can realize a better trade-off between tracking accuracy and convergence time in the whole simulated carrier-to-noise ratio range. Also, the robustness of the modified loop is verified through eliminating the second convergence process which is regarded as the worst issue in the parameter-switching DLL.

关键词： direct sequence spread spectrum code tracking loop delay locked loop convergence time tracking accuracy

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Evaluation of BDS-2/BDS-3 Precise Point Positioning Performance in Polar Region

Evaluation of BDS-2/BDS-3 Precise Point Positioning Performa...

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第十三届中国卫星导航年会

作者： Quanrun Cheng Yize Zhang Junping Chen Shanghai Astronomical Observatory University of Chinese Academy of Sciences

In order to increase the understanding of the positioning performance of BDS in the polar regions, this paper analyzes PPP（precise point positioning） performance under five different combinations which include BDS-3（B1 IB3 I）,BDS（B1 CB2 a）,BDS（B1 IB3 I）,BDS（B1 CB2 a+B1 CB3 I） and GPS（L1 L2） using the observation data of 15 IGS（International GNSS Service） stations around the world for 30 days. The results show that the accuracy of the static PPP in polar regions in the three directions of NEU is 1.1 cm, 0.7 cm, and 1.7 cm, and the kinematic PPP accuracy is 10 cm, 9 cm, and 20 cm. The time for static PPP in the polar region to converge to within 10 cm in the three directions of NEU is less than 15 min, 11 min, and 19 min, while the time for kinematic PPP to converge within 20 cm is less than 17 min, 16 min, and 23 min.

关键词： polar region BeiDou Navigation Satellite System Precise Point Positioning convergence time

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Performance of precise point positioning for BDS-3 PPP-B2b service

Performance of precise point positioning for BDS-3 PPP-B2b s...

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第十三届中国卫星导航年会

作者： Hairong Guo Yangyin Xu Haowei Xiao Jinlong Li Haibo He Wenjun Zhao Beijing Satellite Navigation Center Xi'an Research Institute of Surveying and Mapping Guangzhou South Surveying & Mapping Technology Co. Ltd.

A new precise point positioning（PPP） service has been provided by BeiDou global navigation satellite system（BDS-3）. The correction parameters are broadcasted by PPP-B2 b signal of GEO satellites in real time, including precision orbit correction, clock difference correction and et al for BDS-3 and other GNSS. The PPP service can be realized with dynamic decimeter level and static centimeter level at China and surrounding areas. Firstly, the area of PPP-B2 b service is analyzed based on the threshold of DOP value, and the concerned problems are also pointed out in use, such as the matching problem between correction parameters. Then the evaluation is conducted for three types of correction parameters broadcasted by PPP-B2 b. Lastly, the performance of static PPP and kinematic PPP is also evaluated comprehensive, and suggestions is also gave for the PPP-B2 b applications.

关键词： BDS-3 PPP-B2b service Precise Point Positioning(PPP) convergence time

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convergence Curve for Non-Blind Adaptive Equalizers

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Journal of Signal and Information Processing 2016年第1期7卷 7-17页

作者： Monika Pinchas Department of Electrical and Electronic Engineering Ariel University Ariel Israel

In this paper a closed-form approximated expression is proposed for the Intersymbol Interference (ISI) as a function of time valid during the entire stages of the non-blind adaptive deconvolution process and is suitable for the noisy, real and two independent quadrature carrier input case. The obtained expression is applicable for type of channels where the resulting ISI as a function of time can be described with an exponential model having a single time constant. Based on this new expression for the ISI as a function of time, the convergence time (or number of iteration number required for convergence) of the non-blind adaptive equalizer can be calculated. Up to now, the equalizer’s performance (convergence time and ISI as a function of time) could be obtained only via simulation when the channel coefficients were known. The new proposed expression for the ISI as a function of time is based on the knowledge of the initial ISI and channel power (which is measurable) and eliminates the need to carry out any more the above mentioned simulation. Simulation results indicate a high correlation between the simulated and calculated ISI (based on our proposed expression for the ISI as a function of time) during the whole deconvolution process for the high as well as for the low signal to noise ratio (SNR) condition.

关键词： Non-Blind Adaptive Equalizers Non-Blind Adaptive Deconvolution Acquisition time convergence time

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Comparison of Performances of Three Multi-constellation Precise Point Positioning Models Based on iGMAS Products

Comparison of Performances of Three Multi-constellation Prec...

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第九届中国卫星导航学术年会

作者： Yangyang Liu Ke Su Baoqi Sun Yulong Ge Guoqiang Jiao Shengli Wang National time Service Center Chinese Academy of Sciences Key Laboratory of Precise Positioning and Timing Technology Chinese Academy of Sciences University of Chinese Academy of Sciences Shanghai Astronomical Observatory Chinese Academy of Sciences School of Astronomy and Space Science University of Chinese Academy of Sciences Institute of Ocean Engineering Shandong University of Science and Technology

The paper focuses on the performance of multi-GNSS(GPS, BDS, GLONASS, and Galileo) precise point positioning(PPP) of three commonly used models including Un-differenced(UD) model, Uof C model and Un-combination(UC) model with the products from international GNSS Monitoring and Assessment System(i GMAS). The convergence time and positioning accuracy are investigated. As a comparison, the same processing strategy is employed by using the GBM products provided by Helmholtz-Centre Potsdam-German Research Centre for Geosciences(GFZ). Daily GNSS measurements from 10 stations observed during 30 days in 2015 are used. The result shows that:(1) the convergence time of three multi-constellation PPP models are 22.25 min, 18.92 min and 20.21 min, respectively. The Uof C model has the shortest convergence time and the convergence speed of the UD model is slightly slower than the UC model. The RMS values of the UD model in N, E and U components are 6.1 mm, 7.8 mm and 21.1 mm, respectively. The ones in Uof C model are 5.4 mm, 6.4 mm and 19.5 mm while the ones in UC model are 5.6 mm, 6.7 mm and 19.9 mm. The positioning accuracy of three multi-constellation PPP models is consistent in three components.(2) Using the same observation data, the final positioning accuracy of multi-constellation PPP based on both iG MAS products and GBM products in three models could reach millimeter in the horizontal and millimeter-centimeter in the up component. Although the convergence time of three models using i GMAS products are slightly slower, the results could prove the stability and reliability of i GMAS products.

关键词： iGMAS products Multi-constellation PPP PPP models Positioning accuracy convergence time

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Global fast terminal sliding mode control system for permanent magnet synchronous motor drive under disturbances

Global fast terminal sliding mode control system for permane...

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第37届中国控制会议

作者： Liu Xiang Wang Yan Ji Zhicheng School of Internet of Things Engineering Jiangnan University

This paper introduces a variable structure to regulate speed of PMSM system by a global fast terminal sliding mode control(GFTSMC) technique optimizing speed tracking performance of permanent magnet synchronous motor(PMSM) servo system. Firstly, a global fast terminal sliding mode control strategy is introduced. Compared with common sliding mode control strategy, this strategy eliminates the chattering phenomenon in that it does not contain switching terms. Also, it can make the output speed reach the reference value in finite time, along with a shorter convergence time and a better tracking *** to the complexity of control equations, S-function in MATLAB is adopted to design the GFTSMC. The effectiveness and robustness of the proposed scheme are verified by MATLAB simulations.

关键词： Global fast terminal sliding mode control Chattering free convergence time Tracking precision

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Enhancing convergence efficiency of self-propelled agents by diffusion concept

Enhancing convergence efficiency of self-propelled agents by...

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第40届中国控制会议

作者： Yurong Chen Xianxia Zhang Yinsheng Yu The Shanghai Key Laboratory of Power Station Automation Technology School of Mechatronics and Automation Shanghai University

In recent years, the well-known Vicsek model（VM） has attracted the interest of many researchers. In this paper,we investigate a revised Vicsek model based on diffusion concept, named as diffusion Vicsek model. The proposed diffusion Vicsek model can use weights to make the agents in the cluster more dispersed without introducing additional repulsive forces. In diffusion Vicsek model, the λ is introduced to adjust the degree of dispersion. When the value of λ is larger, it is more conducive to increase the dispersion of the cluster. Especially when λ = 0, the diffusion model will become the original Vicsek *** the simulation experiments, the original Vicsek model and the diffusion Vicsek model are compared. The results show that there is an optimal λ under different number of agents N, communication radius R and absolute velocity v0, which effectively improves the convergence speed of the cluster.

关键词： Multi-agent system Vicsek model Synchronization convergence time

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