In order to obtain the reasonable undrained shear strength Su for geotechnical analyses of bridge foundations in Yangtze River floodplain clayey soils, a site-specific study is conducted using the imported piezocone p...In order to obtain the reasonable undrained shear strength Su for geotechnical analyses of bridge foundations in Yangtze River floodplain clayey soils, a site-specific study is conducted using the imported piezocone penetration test (CPTu) with dissipation phases at the Fourth Nanjing Yangtze River Bridge construction sites. Taking the values of Su from laboratory tests as references, several existing Su-predicted methods based on CPTu are compared and evaluated. To verify the presented cone factor Nk, additional test sites are selected and examined. The results show that the values of cone factors such as Nkt, Nke, and Nau, depend on the shear test mode and disturbance. Generally, the values of Nke show more scattering than those of Nkt and N△u. For the stratified and layered sediments of the Yangtze River floodplain, it is recommended using the net cone resistance qT to estimate Su and the preliminary cone factor values Nkt are from 7 to 16, with an average of 11. It is also confirmed that the CPTu test, as a new technique in site characterization, can present reasonable parameters for bridge foundations.展开更多
The structure of 3 D range sensor system for unmanned vehicle is introduced.Several key technologies are described in detail.The ultrasonic signal is processed from different angles.Image edges are extracted by the m...The structure of 3 D range sensor system for unmanned vehicle is introduced.Several key technologies are described in detail.The ultrasonic signal is processed from different angles.Image edges are extracted by the multiple scale method.Image noises are recognized and cleared by using multilayer forward neural network with fuzzy logic.The method of information fusion for multiple sensors is discussed.This paper also gives some ultrasonic signal curves and image results.展开更多
Aim To describe a news system for measuring the and pitch angles of rocket during the launch phase Methods Optical system was to reflect the spot that represents the angular movement of rocket to the position sensitiv...Aim To describe a news system for measuring the and pitch angles of rocket during the launch phase Methods Optical system was to reflect the spot that represents the angular movement of rocket to the position sensitive detector that can convert analogue signal into digital one.Results Compared with conventional optical lever test system which had been applied to measure rocket attitude angle,the new system used the position sensitive detector to replace the screen and high-speed photographic instrumentation as grapher,which can avert photointerpretive data reduction and apply to field experiment more easily and pre- cisely .Conclusion Experimental results show that the test system can be used in measuring the yaw and pitch angles of rocket effectively.展开更多
A new three-dimensional laterolog array sonde(3D-LS) is presented. The 3DLS is based on existing high-resolution laterolog array and azimuthal resistivity imaging sondes with radial, longitudinal, and circumferentia...A new three-dimensional laterolog array sonde(3D-LS) is presented. The 3DLS is based on existing high-resolution laterolog array and azimuthal resistivity imaging sondes with radial, longitudinal, and circumferential detection abilities. Six investigation modes are designed using the 3D finite-element method and different investigation depths are simulated based on the pseudo-geometrical factor of the six modes. The invasion profile is described using multi-array radial logs. From the analysis of the pseudo-geometrical factor, the investigation depth of the 3D-LS is about 1.5 m for conductive invasion, which is close to that of the dual laterolog tool but greater than that of the highly integrated azimuthal laterolog sonde. The vertical and azimuthal resolution is also analyzed with the same method. The 3DLS can detect low-resistivity anomalies of 0.5 m thickness and 15? around the borehole for infinitely thick formations. This study lays the foundation for more work on 3D laterolog array sonde for evaluating low-resistivity anomalies.展开更多
To aim at the multimode character of the data from the airplane detecting system, the paper combines Dempster- Shafer evidence theory and subjective Bayesian algorithm and makes to propose a mixed structure multimode ...To aim at the multimode character of the data from the airplane detecting system, the paper combines Dempster- Shafer evidence theory and subjective Bayesian algorithm and makes to propose a mixed structure multimode data fusion algorithm. The algorithm adopts a prorated algorithm relate to the incertitude evaluation to convert the probability evaluation into the precognition probability in an identity frame, and ensures the adaptability of different data from different source to the mixed system. To guarantee real time fusion, a combination of time domain fusion and space domain fusion is established, this not only assure the fusion of data chain in different time of the same sensor, but also the data fusion from different sensors distributed in different platforms and the data fusion among different modes. The feasibility and practicability are approved through computer simulation.展开更多
In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, dril...In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high. In order to drill large-diameter rocksocketed pile holes faster at relatively low cost, the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-clasa award by Ministry of Geology and Mineral Resources in 1991. Since it was innovated the drilling system has been used in more than twenty important and tough pro- jects on land, and wonderful results were acquired. At the same time the large-diameter DTH air hammer drilling system was improved continuously. The FGC15D is the latest version of the technique.展开更多
Quantitative thickness estimation below tuning thickness is a great challenge in seismic exploration. Most studies focus on the thin-beds whose top and bottom reflection coefficients are of equal magnitude and opposit...Quantitative thickness estimation below tuning thickness is a great challenge in seismic exploration. Most studies focus on the thin-beds whose top and bottom reflection coefficients are of equal magnitude and opposite polarity. There is no systematic research on the other thin-bed types. In this article, all of the thin-beds are classified into four types: thin-beds with equal magnitude and opposite polarity, thin-beds with unequal magnitude and opposite polarity, thin-beds with equal magnitude and identical polarity, and thin-beds with unequal magnitude and identical polarity. By analytical study, an equation describing the general relationship between seismic peak frequency and thin-bed thickness was derived which shows there is a Complex implicit non-linear relationship between them and which is difficult to use in practice. In order to solve this problem, we simplify the relationship by Taylor expansion and discuss the precision of the approximation formulae with different orders for the four types of thin-beds. Compared with the traditional amplitude method for thin-bed thickness calculation, the method we present has a higher precision and isn't influenced by the absolute value of top or bottom reflection coefficient, so it is convenient for use in practice.展开更多
The principle and accuracy of 3-D coordinates acquisition using one single camera and the Aided Measuring Probe(AMP) are discussed in this paper. Using one single camera and one AMP which has several embedded targets ...The principle and accuracy of 3-D coordinates acquisition using one single camera and the Aided Measuring Probe(AMP) are discussed in this paper. Using one single camera and one AMP which has several embedded targets and one tip with known coordinates, the single camera′s orientation and location can be calculated. After orientation, the global coordinate system is obtained. During measurement, the camera is fixed firstly, then the AMP is held and the feature point is touched.The camera is triggered lastly. The position and orientation of the AMP are therefore calculated from the size and position of its image on the sensor. Since the tip point of AMP has known relation with the embedded targets, the feature point can be measured. Tests show that the accuracy of length measurement is 0.2 mm and accuracy for flatness measurement in XSY-plane is 0.1 mm.展开更多
Mitochondrial cytochrome b (Cytb), one of the few proteins encoded by the mitochondrial DNA, plays an important role in transferring electrons. As a mitochondrial gene, it has been widely used for phylogenetic analy...Mitochondrial cytochrome b (Cytb), one of the few proteins encoded by the mitochondrial DNA, plays an important role in transferring electrons. As a mitochondrial gene, it has been widely used for phylogenetic analysis. Previously, a 949-bp fragment of the coding gene and mRNA editing were characterized from Prorocentrum donghaiense, which might prove useful for resolving P. donghaiense from closely related species. However, the full-length coding region has not been characterized. Ih this study, we used rapid amplification of cDNA ends (RACE) to obtain full-length, 1 124 bp cDNA. Cytb transcript contained a standard initiation codon ATG, but did not have a recognizable stop codon. Homology comparison showed that the P. donghaiense Cytb had a high sequence identity to Cytb sequences from other dinoflagellate species. Phylogenetic analysis placed Cytb from P. donghaiense in the clade of dinoflagellates and it clustered together strongly with that from P. minimum. Based on the full-length sequence, we inferred 32 editing events at different positions, accounting for 2.93% of the Cytb gene. 34.4% (11) of the changes were A to G, 25% (8) were T to C, and 25% (8) were C to U, with smaller proportions of G to C and G to A edits (9.4% (3) and 6.2% (2), respectively). The expression level of the Cytb transcript was quantified by real-time PCR with a TaqMan probe at different times during the whole growth phase. The average Cytb transcript was present at 39.277.46 copies of cDNA per cell during the whole growth cycle, and the expression of Cytb was relatively stable over the different phases. These results deepen our understanding of the structure and characteristics of Cytb in P. donghaiense, and confirmed that Cytb in P. donghaiense is a candidate reference gene for studying the expression of other genes.展开更多
Based on a new special co-inner-outer factorization, a factorization approach for design fault detection observer for LSFDJ was proposed. It is a simple state-space method and can deal with time-varying LSFDJ with sen...Based on a new special co-inner-outer factorization, a factorization approach for design fault detection observer for LSFDJ was proposed. It is a simple state-space method and can deal with time-varying LSFDJ with sensor noise and sensor faults. The performance of the fault detection observer is optimized in an H ∞ setting, where the ratio between the gains from disturbance and fault to residual respectively is minimized. The design parameters of the detection observer were given in terms of the solution to the Riccati differential equation with jumps.展开更多
Valuable mineral resources are widely distributed throughout the seabed. autonomous underwater vehicles (AUVs) are preferable to remotely-operated vehicles (ROVs) when probing for such mineral resources as the extensi...Valuable mineral resources are widely distributed throughout the seabed. autonomous underwater vehicles (AUVs) are preferable to remotely-operated vehicles (ROVs) when probing for such mineral resources as the extensive exploration area makes it difficult to maintain contact with operators. AUVs depend on batteries, so their power consumption should be reduced to extend exploration time. Power for conventional marine instrument systems is incorporated in their waterproof sealing. External intermittent control of this power source until termination of exploration is challenging due to limitations imposed by the underwater environment. Thus, the AUV must have a power control system that can improve performance and maximize use of battery capacity. The authors developed such a power control system with a three-step algorithm. It automatically detects underwater operational states and can limit power, effectively decreasing power consumption by about 15%.展开更多
In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effect...In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace(PCS) and residual subspace(RS). Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator's hydraulic system.展开更多
Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the proble...Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.展开更多
Chang’e-5 mission is China’s first lunar sample return mission.It contains several new flight phases compared with the previous lunar missions,such as the lunar take-off and orbit insertion phase,the rendezvous and ...Chang’e-5 mission is China’s first lunar sample return mission.It contains several new flight phases compared with the previous lunar missions,such as the lunar take-off and orbit insertion phase,the rendezvous and docking phase,etc.Chang’e-5 mission is extremely complicated and full of new challenges.This paper sorts out the characteristics and the difficulties in telemetry,tracking,and command(TT&C)of Chang’e-5 mission.The main technical contribution is a reliable general design of the TT&C system,including the application of X-band TT&C in launch and early orbit phase(LEOP),multiple targets simultaneous TT&C in X-band,lunar surface benchmark calibration,high-precision and rapid orbit trajectory determination for the lunar surface take-off,remote guidance rendezvous and docking,the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner,and the design of the reentry measurement chain.Based on this scheme,a global deep space TT&C network and interplanetary reentry measurement chain have been established for China,and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized,ensuring reliable tracking,accurate measurement and accurate control.The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration(NASA)and European Space Agency(ESA)for subsequent lunar and deep space exploration missions.The techniques of rapid trajectory determination of lunar take-off and orbit entry,as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.展开更多
基金The National Natural Science Foundation of China(No.40702047)
文摘In order to obtain the reasonable undrained shear strength Su for geotechnical analyses of bridge foundations in Yangtze River floodplain clayey soils, a site-specific study is conducted using the imported piezocone penetration test (CPTu) with dissipation phases at the Fourth Nanjing Yangtze River Bridge construction sites. Taking the values of Su from laboratory tests as references, several existing Su-predicted methods based on CPTu are compared and evaluated. To verify the presented cone factor Nk, additional test sites are selected and examined. The results show that the values of cone factors such as Nkt, Nke, and Nau, depend on the shear test mode and disturbance. Generally, the values of Nke show more scattering than those of Nkt and N△u. For the stratified and layered sediments of the Yangtze River floodplain, it is recommended using the net cone resistance qT to estimate Su and the preliminary cone factor values Nkt are from 7 to 16, with an average of 11. It is also confirmed that the CPTu test, as a new technique in site characterization, can present reasonable parameters for bridge foundations.
文摘The structure of 3 D range sensor system for unmanned vehicle is introduced.Several key technologies are described in detail.The ultrasonic signal is processed from different angles.Image edges are extracted by the multiple scale method.Image noises are recognized and cleared by using multilayer forward neural network with fuzzy logic.The method of information fusion for multiple sensors is discussed.This paper also gives some ultrasonic signal curves and image results.
文摘Aim To describe a news system for measuring the and pitch angles of rocket during the launch phase Methods Optical system was to reflect the spot that represents the angular movement of rocket to the position sensitive detector that can convert analogue signal into digital one.Results Compared with conventional optical lever test system which had been applied to measure rocket attitude angle,the new system used the position sensitive detector to replace the screen and high-speed photographic instrumentation as grapher,which can avert photointerpretive data reduction and apply to field experiment more easily and pre- cisely .Conclusion Experimental results show that the test system can be used in measuring the yaw and pitch angles of rocket effectively.
基金sponsored by the National Oil and Gas Major Projects(No.2011ZX05020-009)
文摘A new three-dimensional laterolog array sonde(3D-LS) is presented. The 3DLS is based on existing high-resolution laterolog array and azimuthal resistivity imaging sondes with radial, longitudinal, and circumferential detection abilities. Six investigation modes are designed using the 3D finite-element method and different investigation depths are simulated based on the pseudo-geometrical factor of the six modes. The invasion profile is described using multi-array radial logs. From the analysis of the pseudo-geometrical factor, the investigation depth of the 3D-LS is about 1.5 m for conductive invasion, which is close to that of the dual laterolog tool but greater than that of the highly integrated azimuthal laterolog sonde. The vertical and azimuthal resolution is also analyzed with the same method. The 3DLS can detect low-resistivity anomalies of 0.5 m thickness and 15? around the borehole for infinitely thick formations. This study lays the foundation for more work on 3D laterolog array sonde for evaluating low-resistivity anomalies.
文摘To aim at the multimode character of the data from the airplane detecting system, the paper combines Dempster- Shafer evidence theory and subjective Bayesian algorithm and makes to propose a mixed structure multimode data fusion algorithm. The algorithm adopts a prorated algorithm relate to the incertitude evaluation to convert the probability evaluation into the precognition probability in an identity frame, and ensures the adaptability of different data from different source to the mixed system. To guarantee real time fusion, a combination of time domain fusion and space domain fusion is established, this not only assure the fusion of data chain in different time of the same sensor, but also the data fusion from different sensors distributed in different platforms and the data fusion among different modes. The feasibility and practicability are approved through computer simulation.
文摘In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high. In order to drill large-diameter rocksocketed pile holes faster at relatively low cost, the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-clasa award by Ministry of Geology and Mineral Resources in 1991. Since it was innovated the drilling system has been used in more than twenty important and tough pro- jects on land, and wonderful results were acquired. At the same time the large-diameter DTH air hammer drilling system was improved continuously. The FGC15D is the latest version of the technique.
基金supported by National Key S&T Special Projects of Marine Carbonate 2008ZX05000-004CNPC Projects 2008E-0610-10
文摘Quantitative thickness estimation below tuning thickness is a great challenge in seismic exploration. Most studies focus on the thin-beds whose top and bottom reflection coefficients are of equal magnitude and opposite polarity. There is no systematic research on the other thin-bed types. In this article, all of the thin-beds are classified into four types: thin-beds with equal magnitude and opposite polarity, thin-beds with unequal magnitude and opposite polarity, thin-beds with equal magnitude and identical polarity, and thin-beds with unequal magnitude and identical polarity. By analytical study, an equation describing the general relationship between seismic peak frequency and thin-bed thickness was derived which shows there is a Complex implicit non-linear relationship between them and which is difficult to use in practice. In order to solve this problem, we simplify the relationship by Taylor expansion and discuss the precision of the approximation formulae with different orders for the four types of thin-beds. Compared with the traditional amplitude method for thin-bed thickness calculation, the method we present has a higher precision and isn't influenced by the absolute value of top or bottom reflection coefficient, so it is convenient for use in practice.
文摘The principle and accuracy of 3-D coordinates acquisition using one single camera and the Aided Measuring Probe(AMP) are discussed in this paper. Using one single camera and one AMP which has several embedded targets and one tip with known coordinates, the single camera′s orientation and location can be calculated. After orientation, the global coordinate system is obtained. During measurement, the camera is fixed firstly, then the AMP is held and the feature point is touched.The camera is triggered lastly. The position and orientation of the AMP are therefore calculated from the size and position of its image on the sensor. Since the tip point of AMP has known relation with the embedded targets, the feature point can be measured. Tests show that the accuracy of length measurement is 0.2 mm and accuracy for flatness measurement in XSY-plane is 0.1 mm.
基金Supported by the National Natural Science Foundation of China (Nos.40406028, 40706044)
文摘Mitochondrial cytochrome b (Cytb), one of the few proteins encoded by the mitochondrial DNA, plays an important role in transferring electrons. As a mitochondrial gene, it has been widely used for phylogenetic analysis. Previously, a 949-bp fragment of the coding gene and mRNA editing were characterized from Prorocentrum donghaiense, which might prove useful for resolving P. donghaiense from closely related species. However, the full-length coding region has not been characterized. Ih this study, we used rapid amplification of cDNA ends (RACE) to obtain full-length, 1 124 bp cDNA. Cytb transcript contained a standard initiation codon ATG, but did not have a recognizable stop codon. Homology comparison showed that the P. donghaiense Cytb had a high sequence identity to Cytb sequences from other dinoflagellate species. Phylogenetic analysis placed Cytb from P. donghaiense in the clade of dinoflagellates and it clustered together strongly with that from P. minimum. Based on the full-length sequence, we inferred 32 editing events at different positions, accounting for 2.93% of the Cytb gene. 34.4% (11) of the changes were A to G, 25% (8) were T to C, and 25% (8) were C to U, with smaller proportions of G to C and G to A edits (9.4% (3) and 6.2% (2), respectively). The expression level of the Cytb transcript was quantified by real-time PCR with a TaqMan probe at different times during the whole growth phase. The average Cytb transcript was present at 39.277.46 copies of cDNA per cell during the whole growth cycle, and the expression of Cytb was relatively stable over the different phases. These results deepen our understanding of the structure and characteristics of Cytb in P. donghaiense, and confirmed that Cytb in P. donghaiense is a candidate reference gene for studying the expression of other genes.
基金National Natural Science Foundation ofChina (No.60 2 740 5 8)
文摘Based on a new special co-inner-outer factorization, a factorization approach for design fault detection observer for LSFDJ was proposed. It is a simple state-space method and can deal with time-varying LSFDJ with sensor noise and sensor faults. The performance of the fault detection observer is optimized in an H ∞ setting, where the ratio between the gains from disturbance and fault to residual respectively is minimized. The design parameters of the detection observer were given in terms of the solution to the Riccati differential equation with jumps.
文摘Valuable mineral resources are widely distributed throughout the seabed. autonomous underwater vehicles (AUVs) are preferable to remotely-operated vehicles (ROVs) when probing for such mineral resources as the extensive exploration area makes it difficult to maintain contact with operators. AUVs depend on batteries, so their power consumption should be reduced to extend exploration time. Power for conventional marine instrument systems is incorporated in their waterproof sealing. External intermittent control of this power source until termination of exploration is challenging due to limitations imposed by the underwater environment. Thus, the AUV must have a power control system that can improve performance and maximize use of battery capacity. The authors developed such a power control system with a three-step algorithm. It automatically detects underwater operational states and can limit power, effectively decreasing power consumption by about 15%.
基金Project(2003AA430200) supported by the National High-Tech Research and Development Program of China
文摘In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace(PCS) and residual subspace(RS). Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator's hydraulic system.
基金National Key Research and Development Program of China(No.2018YFE0208200)National Natural Science Foundation of China(Nos.61971307,61905175,51775377)+5 种基金National Key Research and Development Plan Project(No.2020YFB2010800)The Fok Ying Tung Education Foundation(No.171055)China Postdoctoral Science Foundation(No.2020M680878)Guangdong Province Key Research and Development Plan Project(No.2020B0404030001)Tianjin Science and Technology Plan Project(No.20YDTPJC01660)Project of Foreign Affairs Committee of China Aviation Development Sichuan Gas Turbine Research Institute(Nos.GJCZ-2020-0040,GJCZ-2020-0041)。
文摘Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.
文摘Chang’e-5 mission is China’s first lunar sample return mission.It contains several new flight phases compared with the previous lunar missions,such as the lunar take-off and orbit insertion phase,the rendezvous and docking phase,etc.Chang’e-5 mission is extremely complicated and full of new challenges.This paper sorts out the characteristics and the difficulties in telemetry,tracking,and command(TT&C)of Chang’e-5 mission.The main technical contribution is a reliable general design of the TT&C system,including the application of X-band TT&C in launch and early orbit phase(LEOP),multiple targets simultaneous TT&C in X-band,lunar surface benchmark calibration,high-precision and rapid orbit trajectory determination for the lunar surface take-off,remote guidance rendezvous and docking,the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner,and the design of the reentry measurement chain.Based on this scheme,a global deep space TT&C network and interplanetary reentry measurement chain have been established for China,and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized,ensuring reliable tracking,accurate measurement and accurate control.The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration(NASA)and European Space Agency(ESA)for subsequent lunar and deep space exploration missions.The techniques of rapid trajectory determination of lunar take-off and orbit entry,as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.