A DGPS positioning model is described, and the elements that influence DGPS positioning precision are analyzed in detail. On this basis, the methods of improving DGPS positioning precision are proposed which include i...A DGPS positioning model is described, and the elements that influence DGPS positioning precision are analyzed in detail. On this basis, the methods of improving DGPS positioning precision are proposed which include increasing updating rate of DGPS correction, building extended DGPS system and improving quality of DGPS correction signal. In the intelligent monitor and control system of the public transport in Beijing, these methods improve the vehicle positioning precision to 2～5m.展开更多
Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has ove...Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has over 6000 satellites in orbit,and its signals contain synchronous sequences usable for pseudo-range positioning.Thus,it has a potential serve as an alternative to Global Navigation Satellite System(GNSS)for providing Positioning,Navigation,and Timing(PNT)services.Compared to parabolic antennas and electronically scanned phased array antennas for receiving Starlink signals,wide-beam antennas(such as Low-Noise Block(LNB)downconverters)can be used to achieve low-cost multi-satellite tracking.However,it also encounters the issues of distinguishing between multiple satellite signals and low received signal power,which requires high-sensitivity detection.Moreover,there are some other issues such as unknown signal transmission time and real-time satellite orbits,thereby causing failure to navigation.Accordingly,this study focuses on LEO constellations represented by Starlink,proposes a joint pseudo-range and Doppler positioning method for Starlink satellite Signals of Opportunity(SOP)based on the comprehensive utilization of signals and information from LEO satellites.Moreover,this study analyzes the signal detection capability and satellite isolation method,examines the algorithm’s orbital error suppression performance,and establishes the concept of Equivalent Position Dilution of Precision(EPDOP)S_(EPDOP)for joint pseudo-range and Doppler positioning.In the experiment because Starlink satellite signals are not available in China,we take the advantage of Iridium NEXT satellites’global seamless coverage,utilize an algorithm to get pseudo-range observations with the Iridium NEXT signals,and then combine them with Starlink Doppler observations to achieve the joint pseudo-range and Doppler positioning of LEO satellites’SOPs.The experiment results demonstrate that when relying on Starlink Doppler observations for positioning,the proposed method achieves Two-Dimensional(2D)positioning accuracy of 3.6 m and Three-Dimensional(3D)positioning accuracy of 6.2 m.Compared to existing Starlink positioning algorithms based on parabolic antennas and electronically scanned phased array antennas,this method improves the accuracy by at least 35.7%.Additionally,Iridium NEXT signals are used to validate the performance of the proposed algorithm for joint pseudo-range and Doppler positioning.In a 40 km long-baseline scenario,the algorithm achieved a 2D positioning accuracy of 24 m and a 3D positioning accuracy of 41 m with Iridium NEXT satellite pseudo-range and Doppler measurements.展开更多
This study presents a conceptual design for a cost-effective submersible gravity-type fish cage with a single-point mooring design.The performance of the new design in reducing environmental loads under extreme sea co...This study presents a conceptual design for a cost-effective submersible gravity-type fish cage with a single-point mooring design.The performance of the new design in reducing environmental loads under extreme sea con-ditions is demonstrated using an in-house numerical code package.The effectiveness of the submerging and surfacing operations of the fish cages is validated through numerical simulations.In the present code package,irregular wave modelling is employed to generate the wave elevations,velocities and accelerations,and the hydrodynamic forces acting on the fish cages and mooring system are calculated using the Morison model.A submersible model for the floating collar is developed to simulate the submerging and surfacing operations of the fish cages.The deformations of the fish cage system are calculated using a modified extended position based dynamics(XPBD)method combined with a mode superposition method.Results show that tension in the mooring system is significantly reduced when fish cages are submerged in the water layer with lower current speeds,and extending the buoy line to lower the conjunction point helps maintain fish cages in the desired water layer under extreme sea conditions.Flooding the outer tubes of the floating collar allows the fish cages to smoothly submerge to the desired water depth.The surfacing designs based on the compressed air and the lifting operation of the bottom sinker can enable the cages to ascend to the water surface.The submerging and surface operations are proved to be completed within six minutes.The new design based on the lifting operation of the bottom sinker,is safer and more cost-effective than the design based on compressed air for the surfacing operation.The design of the submersible single-point mooring gravity-type fish cage is thereby validated through the present numerical methods,offering valuable insights for future aquaculture design and implementation.展开更多
In this paper,we numerically analyze the factors determining localization precision and resolution in single emitter localization-based imaging systems.While previous studies have considered a limited set of parameter...In this paper,we numerically analyze the factors determining localization precision and resolution in single emitter localization-based imaging systems.While previous studies have considered a limited set of parameters,our numerical approach incorporates additional parameters with significant reference values,yielding a more comprehensive analysis of the results.We differentiate between the effects of additive and multiplicative noise on localization precision using numerical modeling and take the influence of the sampling frequency into account,computing the optimal sampling frequency for varying resolution requirements.Leveraging a suite of derived equations,we systematically simulate and quantify how variations in these parameters influence system performance.Furthermore,we provide guidelines for optimizing signal-to-noise ratio(SNR)requirements and pixel size selection based on point spread function(PSF)width in single emitter localization-based imaging systems.This numerically driven research offers critical insights for the analysis of more complex imaging systems.展开更多
文摘A DGPS positioning model is described, and the elements that influence DGPS positioning precision are analyzed in detail. On this basis, the methods of improving DGPS positioning precision are proposed which include increasing updating rate of DGPS correction, building extended DGPS system and improving quality of DGPS correction signal. In the intelligent monitor and control system of the public transport in Beijing, these methods improve the vehicle positioning precision to 2～5m.
基金support is received from the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0350101)the Project(E2M4140306).
文摘Low Earth Orbit(LEO)satellites,with their wide coverage and large number,have gradually become a crucial platform and means for navigation and positioning services.Compared to other LEO constellations,Starlink has over 6000 satellites in orbit,and its signals contain synchronous sequences usable for pseudo-range positioning.Thus,it has a potential serve as an alternative to Global Navigation Satellite System(GNSS)for providing Positioning,Navigation,and Timing(PNT)services.Compared to parabolic antennas and electronically scanned phased array antennas for receiving Starlink signals,wide-beam antennas(such as Low-Noise Block(LNB)downconverters)can be used to achieve low-cost multi-satellite tracking.However,it also encounters the issues of distinguishing between multiple satellite signals and low received signal power,which requires high-sensitivity detection.Moreover,there are some other issues such as unknown signal transmission time and real-time satellite orbits,thereby causing failure to navigation.Accordingly,this study focuses on LEO constellations represented by Starlink,proposes a joint pseudo-range and Doppler positioning method for Starlink satellite Signals of Opportunity(SOP)based on the comprehensive utilization of signals and information from LEO satellites.Moreover,this study analyzes the signal detection capability and satellite isolation method,examines the algorithm’s orbital error suppression performance,and establishes the concept of Equivalent Position Dilution of Precision(EPDOP)S_(EPDOP)for joint pseudo-range and Doppler positioning.In the experiment because Starlink satellite signals are not available in China,we take the advantage of Iridium NEXT satellites’global seamless coverage,utilize an algorithm to get pseudo-range observations with the Iridium NEXT signals,and then combine them with Starlink Doppler observations to achieve the joint pseudo-range and Doppler positioning of LEO satellites’SOPs.The experiment results demonstrate that when relying on Starlink Doppler observations for positioning,the proposed method achieves Two-Dimensional(2D)positioning accuracy of 3.6 m and Three-Dimensional(3D)positioning accuracy of 6.2 m.Compared to existing Starlink positioning algorithms based on parabolic antennas and electronically scanned phased array antennas,this method improves the accuracy by at least 35.7%.Additionally,Iridium NEXT signals are used to validate the performance of the proposed algorithm for joint pseudo-range and Doppler positioning.In a 40 km long-baseline scenario,the algorithm achieved a 2D positioning accuracy of 24 m and a 3D positioning accuracy of 41 m with Iridium NEXT satellite pseudo-range and Doppler measurements.
基金supported by the Research Council of Norway through the project“Unleashing the sustainable value creation potential of offshore ocean aquaculture”(Project number:328724).
文摘This study presents a conceptual design for a cost-effective submersible gravity-type fish cage with a single-point mooring design.The performance of the new design in reducing environmental loads under extreme sea con-ditions is demonstrated using an in-house numerical code package.The effectiveness of the submerging and surfacing operations of the fish cages is validated through numerical simulations.In the present code package,irregular wave modelling is employed to generate the wave elevations,velocities and accelerations,and the hydrodynamic forces acting on the fish cages and mooring system are calculated using the Morison model.A submersible model for the floating collar is developed to simulate the submerging and surfacing operations of the fish cages.The deformations of the fish cage system are calculated using a modified extended position based dynamics(XPBD)method combined with a mode superposition method.Results show that tension in the mooring system is significantly reduced when fish cages are submerged in the water layer with lower current speeds,and extending the buoy line to lower the conjunction point helps maintain fish cages in the desired water layer under extreme sea conditions.Flooding the outer tubes of the floating collar allows the fish cages to smoothly submerge to the desired water depth.The surfacing designs based on the compressed air and the lifting operation of the bottom sinker can enable the cages to ascend to the water surface.The submerging and surface operations are proved to be completed within six minutes.The new design based on the lifting operation of the bottom sinker,is safer and more cost-effective than the design based on compressed air for the surfacing operation.The design of the submersible single-point mooring gravity-type fish cage is thereby validated through the present numerical methods,offering valuable insights for future aquaculture design and implementation.
基金Project supported by the National Key Research and Development Program of China(No.2022YFB3206000)the Scientific and Technological Innovation Project of China Academy of Chinese Medical Sciences(No.CI2023C009YG)the Research and Development Program of Jiaxing(No.2022AD10028)。
文摘In this paper,we numerically analyze the factors determining localization precision and resolution in single emitter localization-based imaging systems.While previous studies have considered a limited set of parameters,our numerical approach incorporates additional parameters with significant reference values,yielding a more comprehensive analysis of the results.We differentiate between the effects of additive and multiplicative noise on localization precision using numerical modeling and take the influence of the sampling frequency into account,computing the optimal sampling frequency for varying resolution requirements.Leveraging a suite of derived equations,we systematically simulate and quantify how variations in these parameters influence system performance.Furthermore,we provide guidelines for optimizing signal-to-noise ratio(SNR)requirements and pixel size selection based on point spread function(PSF)width in single emitter localization-based imaging systems.This numerically driven research offers critical insights for the analysis of more complex imaging systems.
