Autonomous orbit determination via integration of epoch-differenced gravity gradients and starlight refraction is proposed in this paper for low-Earth-orbiting satellites operating in GPSdenied environments. Starlight...Autonomous orbit determination via integration of epoch-differenced gravity gradients and starlight refraction is proposed in this paper for low-Earth-orbiting satellites operating in GPSdenied environments. Starlight refraction compensates for the significant along-track position error that occurs from only using gravity gradients and benefits from integration in terms of improved accuracy in radial and cross-track position estimates. The between-epoch differencing of gravity gradients is employed to eliminate slowly varying measurement biases and noise near the orbit revolution frequency. The refraction angle measurements are directly used and its Jacobian matrix derived from an implicit observation equation. An information fusion filter based on a sequential extended Kalman filter is developed for the orbit determination. Truth-model simulations are used to test the performance of the algorithm, and the effects of differencing intervals and orbital heights are analyzed. A semi-simulation study using actual gravity gradient data from the Gravity field and steady-state Ocean Circulation Explorer（GOCE） combined with simulated starlight refraction measurements is further conducted, and a three-dimensional position accuracy of better than 100 m is achieved.展开更多
Aero-optical effects for starlight transmission in the high-speed flow field will reduce the accuracy of the star sensor on an aircraft.Numerical simulations for aero-optical effects usually require plenty of calculat...Aero-optical effects for starlight transmission in the high-speed flow field will reduce the accuracy of the star sensor on an aircraft.Numerical simulations for aero-optical effects usually require plenty of calculations,which cause difficulties when designing a celestial navigation system for a high-speed aircraft.In this study,an Aero-Optical Simulator For Starlight Transmission(AOSST)in the boundary layer is developed.It effectively reduces the computational burden compared to that of the widely used CFD simulation,and it achieves satisfactory accuracy.In this simulator,gas ellipsoids satisfying certain design rules are used to simulate coherent density structures in boundary layers.Design rules for the gas ellipsoids are found from published experimental and high-fidelity CFD simulation results.The generated wavefront distortion by AOSST is anchored with the scale law for aero-optical distortion in the boundary layer by determining some control parameters,which enables the simulator to output reliable results over a wide range of flight states.Four numerical examples are provided to verify the performance of AOSST.The results demonstrate that AOSST is able to simulate the directional dependence of aero-optical distortions in boundary layers,the variation trend of distorted wavefront shapes with Reynolds number,and the grayscale distribution on the disturbed star map.展开更多
Blast furnace(BF)burden surface contains the most abundant,intuitive and credible smelting information and acquiring high-definition and high-brightness optical images of which is essential to realize precise material...Blast furnace(BF)burden surface contains the most abundant,intuitive and credible smelting information and acquiring high-definition and high-brightness optical images of which is essential to realize precise material charging control,optimize gas flow distribution and improve ironmaking efficiency.It has been challengeable to obtain high-quality optical burden surface images under high-temperature,high-dust,and extremelydim(less than 0.001 Lux)environment.Based on a novel endoscopic sensing detection idea,a reverse telephoto structure starlight imaging system with large field of view and large aperture is designed.Combined with a water-air dual cooling intelligent self-maintenance protection device and the imaging system,a starlight high-temperature industrial endoscope is developed to obtain clear optical burden surface images stably under the harsh environment.Based on an endoscope imaging area model,a material flow trajectory model and a gas-dust coupling distribution model,an optimal installation position and posture configuration method for the endoscope is proposed,which maximizes the effective imaging area and ensures large-area,safe and stable imaging of the device in a confined space.Industrial experiments and applications indicate that the proposed method obtains clear and reliable large-area optical burden surface images and reveals new BF conditions,providing key data support for green iron smelting.展开更多
The Starlight Project, a top real estate tourism project, recently broke ground in Tianjin Municipality. The launch of the project is a piece of groundbreaking news in and out of the real estate industry. Upon complet...The Starlight Project, a top real estate tourism project, recently broke ground in Tianjin Municipality. The launch of the project is a piece of groundbreaking news in and out of the real estate industry. Upon completion, the Starlight Project will become a new highlight in Tianjin and China’展开更多
基金supported by the National Natural Science Foundation of China (No.11002008)funded in part by Ministry of Science and Technology of China (No.2014CB845303)
文摘Autonomous orbit determination via integration of epoch-differenced gravity gradients and starlight refraction is proposed in this paper for low-Earth-orbiting satellites operating in GPSdenied environments. Starlight refraction compensates for the significant along-track position error that occurs from only using gravity gradients and benefits from integration in terms of improved accuracy in radial and cross-track position estimates. The between-epoch differencing of gravity gradients is employed to eliminate slowly varying measurement biases and noise near the orbit revolution frequency. The refraction angle measurements are directly used and its Jacobian matrix derived from an implicit observation equation. An information fusion filter based on a sequential extended Kalman filter is developed for the orbit determination. Truth-model simulations are used to test the performance of the algorithm, and the effects of differencing intervals and orbital heights are analyzed. A semi-simulation study using actual gravity gradient data from the Gravity field and steady-state Ocean Circulation Explorer（GOCE） combined with simulated starlight refraction measurements is further conducted, and a three-dimensional position accuracy of better than 100 m is achieved.
基金supported by the National Defense PreResearch Foundation of China(No.JCKY2016601C005)the Science and Technology on Space Intelligent Control Laboratory of China(No.ZDSYS-2018-03)。
文摘Aero-optical effects for starlight transmission in the high-speed flow field will reduce the accuracy of the star sensor on an aircraft.Numerical simulations for aero-optical effects usually require plenty of calculations,which cause difficulties when designing a celestial navigation system for a high-speed aircraft.In this study,an Aero-Optical Simulator For Starlight Transmission(AOSST)in the boundary layer is developed.It effectively reduces the computational burden compared to that of the widely used CFD simulation,and it achieves satisfactory accuracy.In this simulator,gas ellipsoids satisfying certain design rules are used to simulate coherent density structures in boundary layers.Design rules for the gas ellipsoids are found from published experimental and high-fidelity CFD simulation results.The generated wavefront distortion by AOSST is anchored with the scale law for aero-optical distortion in the boundary layer by determining some control parameters,which enables the simulator to output reliable results over a wide range of flight states.Four numerical examples are provided to verify the performance of AOSST.The results demonstrate that AOSST is able to simulate the directional dependence of aero-optical distortions in boundary layers,the variation trend of distorted wavefront shapes with Reynolds number,and the grayscale distribution on the disturbed star map.
基金the National Natural Science Foundation of China(62273359)the General Project of Hunan Natural Science Foundation of China(2022JJ30748)the National Major Scientific Research Equipment of China(61927803)。
文摘Blast furnace(BF)burden surface contains the most abundant,intuitive and credible smelting information and acquiring high-definition and high-brightness optical images of which is essential to realize precise material charging control,optimize gas flow distribution and improve ironmaking efficiency.It has been challengeable to obtain high-quality optical burden surface images under high-temperature,high-dust,and extremelydim(less than 0.001 Lux)environment.Based on a novel endoscopic sensing detection idea,a reverse telephoto structure starlight imaging system with large field of view and large aperture is designed.Combined with a water-air dual cooling intelligent self-maintenance protection device and the imaging system,a starlight high-temperature industrial endoscope is developed to obtain clear optical burden surface images stably under the harsh environment.Based on an endoscope imaging area model,a material flow trajectory model and a gas-dust coupling distribution model,an optimal installation position and posture configuration method for the endoscope is proposed,which maximizes the effective imaging area and ensures large-area,safe and stable imaging of the device in a confined space.Industrial experiments and applications indicate that the proposed method obtains clear and reliable large-area optical burden surface images and reveals new BF conditions,providing key data support for green iron smelting.
文摘The Starlight Project, a top real estate tourism project, recently broke ground in Tianjin Municipality. The launch of the project is a piece of groundbreaking news in and out of the real estate industry. Upon completion, the Starlight Project will become a new highlight in Tianjin and China’
