A recent single-center retrospective study proposed novel combinations of hematological parameters and scoring systems for predicting severe acute pancre-atitis.While these combinations showed promising predictive per...A recent single-center retrospective study proposed novel combinations of hematological parameters and scoring systems for predicting severe acute pancre-atitis.While these combinations showed promising predictive performance,several limitations warrant consideration,including the lack of calibration,the absence of key inflammatory markers such as procalcitonin,and practical challenges in integrating these models into routine clinical workflows.To improve predictive accuracy and clinical applicability,prospective validation and the inclusion of additional variables are recommended.展开更多
In order to get rid of the dependence on high-precision centrifuges in accelerometer nonlinear coefficients calibration,this paper proposes a system-level calibration method for field condition.Firstly,a 42-dimension ...In order to get rid of the dependence on high-precision centrifuges in accelerometer nonlinear coefficients calibration,this paper proposes a system-level calibration method for field condition.Firstly,a 42-dimension Kalman filter is constructed to reduce impact brought by turntable.Then,a biaxial rotation path is designed based on the accelerometer output model,including orthogonal 22 positions and tilt 12 positions,which enhances gravity excitation on nonlinear coefficients of accelerometer.Finally,sampling is carried out for calibration and further experiments.The results of static inertial navigation experiments lasting 4000 s show that compared with the traditional method,the proposed method reduces the position error by about 390 m.展开更多
Traditional calibration method for the digital inclinometer relies on manual inspection,and results in its disadvantages of complicated process,low-efficiency and human errors easy to be introduced.To improve both the...Traditional calibration method for the digital inclinometer relies on manual inspection,and results in its disadvantages of complicated process,low-efficiency and human errors easy to be introduced.To improve both the calibration accuracy and efficiency of digital inclinometer,an automatic digital inclinometer calibration system was developed in this study,and a new display tube recognition algorithm was proposed.First,a high-precision automatic turntable was taken as the reference to calculate the indication error of the inclinometer.Then,the automatic inclinometer calibration control process and the digital inclinometer zero-setting function were formulated.For display tube recognition,a new display tube recognition algorithm combining threading method and feature extraction method was proposed.Finally,the calibration system was calibrated by photoelectric autocollimator and regular polygon mirror,and the calibration system error and repeatability were calculated via a series of experiments.The experimental results showed that the indication error of the proposed calibration system was less than 4",and the repeatability was 3.9".A digital inclinometer with the resolution of 0.1°was taken as a testing example,within the calibration points'range of[-90°,90°],the repeatability of the testing was 0.085°,and the whole testing process was less than 90 s.The digital inclinometer indication error is mainly introduced by the digital inclinometer resolution according to the uncertainty evaluation.展开更多
In clinical environments,the prolonged utilization of polarization equipment can result in theaccumulation of errors over extended periods.The absence of expeditious calibration techniques in clinical practice present...In clinical environments,the prolonged utilization of polarization equipment can result in theaccumulation of errors over extended periods.The absence of expeditious calibration techniques in clinical practice presents a significant obstacle in preserving the precision and dependability of these instruments.To address this challenge,we propose an innovative research study that presents a comprebersive calibration system specifically designed for the calibration of the backscattering Muellet matrix measurement system,enabling swift online calibration acroes various scenarios.This system employs an external calibration framework for rmal-time adjust-ment of the polarizer's initial angle,oversecing the rotation of PSG and PSA motors through position measurement and control procedures,with light intensity monitored by a camera.By incorporating moment um concepts and the Adam optimization algorithm,we enhance conver-gence speed,mitigate noise,and improve calibration accuracy.Experimental results showcase the exceptional precision,speed,and robustness of oрroposed method,achieving high acсuracy and minimal error,thereby offering a promising solution for maintaining the reliabilit y of polarization equipment in clinical settings.展开更多
Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them requ...Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them require altering the magnetic vector in the vehicle coordinate system.Exploring the use of geomagnetic variation to change the geomagnetic vector in the vehicle coordinate system,this paper proposes a novel vector magnetic measurement calibration method.In this method,a vector magnetometer mounted on a vehicle and an accurate vector magnetometer separately measure the geomagnetic field at diff erent locations within the same area.Based on the physical principle that the geomagnetic variation at two nearby locations is equal,the calibration parameters of the magnetometer on the vehicle can be determined through a set of equations containing the measurements from the two magnetometers.The theoretical derivation and simulation experiment results demonstrate the feasibility of this method.Therefore,it can serve as a new alternative calibration method,especially in scenarios where a high degree of accuracy in the estimation of calibration parameters is not required.展开更多
To address the installation challenges of a 2-m ring Gregorian telescope system,and similar optical systems with a small width-to-radius ratio,we propose a detection method combining local interferometry with a compar...To address the installation challenges of a 2-m ring Gregorian telescope system,and similar optical systems with a small width-to-radius ratio,we propose a detection method combining local interferometry with a comparison model.This method enhances the precision of system calibration by establishing a dataset that delineates the relationship between secondary mirror misalignment and wavefront aberration,subsequently inferring the misalignment from interferometric detection results during the calibration process.For the 2-m ring telescope,we develop a detection model using five local sub-apertures,enabling a root-mean-square detection accuracy of 0:0225λ(λ=632:8 nm)for full-aperture wavefront aberration.The calibration results for the 2-m Ring Solar Telescope system indicate that the root-mean-square value of sub-aperture wavefront aberration reaches 0.104λ,and the root-mean-square value of spliced full-aperture measurement yields reaches 0.112λ.This method offers a novel approach for calibrating small width-toradius ratio telescope systems and can be applied to the calibration of other irregular-aperture optical systems.展开更多
Based on error analysis, the influence of error sources on strapdown inertial navigation systems is discussed. And the maximum permissible component tolerances are established. In order to achieve the desired accuracy...Based on error analysis, the influence of error sources on strapdown inertial navigation systems is discussed. And the maximum permissible component tolerances are established. In order to achieve the desired accuracy (defined by circular error probability), the types of appropriate sensors are chosen. The inertial measurement unit (IMU) is composed of those sensors. It is necessary to calibrate the sensors to obtain their error model coefficients of IMU. After calibration tests, the accuracy is calculated by uniform design method and it is proved that the accuracy of IMU is satisfied for the desired goal.展开更多
A new distributed test system composed of multiple test nodes was designed by adopting storage test technology to test shock waves in explosion field. The advantage of the system is the application of sensor lattice w...A new distributed test system composed of multiple test nodes was designed by adopting storage test technology to test shock waves in explosion field. The advantage of the system is the application of sensor lattice whose rise time is microsecond level, which can quickly response to transient shock wave signals. In order to reduce dynamic response error, shock tube is employed to conduct dynamic calibration on the system. The overpressure peak values of the explosion shock wave collected by sensor lattice were used to construct a shock wave pressure field with B-spline interpolation algorithm.展开更多
A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, ...A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, spe cified in spherical coordinates, is generated first, which is then used to calibrate the tracking results by a two dimensional interpolation. The scheme can effectively correct the static errors in the magnetic tracking system. The employment of spherical coordinates significantly reduces the calculation complexity in calibration.展开更多
A plane-based and linear camera calibration technique without considering lens distortion is proposed in a greedy and intuitive framework for the binocular camera system. Characteristic homography matrix and consisten...A plane-based and linear camera calibration technique without considering lens distortion is proposed in a greedy and intuitive framework for the binocular camera system. Characteristic homography matrix and consistency constraints in close range are employed in this calibration. First, in order to calculate the internal geometries of the cameras, total least-square fitting as a robust tool for the geometrical cost function is exploited to recover the accurate principal point of each camera from all the characteristic lines of the homography matrices for all model planes. Secondly, generic prior knowledge of the aspect ratio of pixel cells is incorporated into the system to obtain the exact principal length in each camera. Thirdly, extrinsic geometries are accurately computed for all planar patterns with respect to each monocular camera. Finally, the rigid displacement between binocular cameras can be obtained by imposing the consistency constraints in 3-space geometry. Both simulation and real image experimental results indicate that reasonably reliable results can be obtained by this technique. And the proposed method is sufficient for applications where high precision is not required and can be easily performed by common computer users who are not experts in computer vision.展开更多
A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine. This machine is designed to serve a specific purpose to attain high accuracy and high efficien...A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine. This machine is designed to serve a specific purpose to attain high accuracy and high efficiency grinding of turbine blades by eliminating the hand grinding process. Although its topology is RPPPR （P： prismatic; R： rotary）, its design is quite distinct from the competitive machine tools. As error quantification is the only way to investigate, maintain and improve its accuracy, calibra- tion is recommended for its performance assessment and acceptance testing. Systematic geometric error modeling technique is implemented and 52 position dependent and position independent errors are identified while considering the machine as five rigid bodies by eliminating the set-up errors of workpiece and cutting tool. 39 of them are found to have influential errors and are accommodated for finding the resultant effect between the cutting tool and the workpiece in workspace volume. Rigid body kinematics techniques and homogenous transformation matrices are used for error synthesis.展开更多
At present,dental implant surgery mainly relies on the clinical experience of the doctor and the assistance of preoperative medical imaging.However,there are some problems in dental implant surgery,such as narrow spac...At present,dental implant surgery mainly relies on the clinical experience of the doctor and the assistance of preoperative medical imaging.However,there are some problems in dental implant surgery,such as narrow space,sight obstruction,inaccurate positioning,and high requirements of doctors’proficiency.Therefore,a dental implant robot system(DIRS)guided by optical navigation is developed in this study,with an x-shaped tool and an irregular pentagonal tracer are designed for spatial registration and needle tip positioning strategy respectively.The coordinate system of each unit in DIRS is unified through system calibration,spatial registration,and needle tip positioning strategy.Then the surgical path is planned on the computed tomography(CT)images in the navigation software before operation.The automatic positioning method and the auxiliary positioning method can be used in the operation to achieve accurate positioning and assist doctors to complete the operation.The errors of spatial registration,needle tip positioning strategy,and the overall accuracy of the system were evaluated respectively,and the results showed that they all met the needs of clinical surgery.This study preliminarily verified the feasibility of the precise positioning method for dental surgery robots and provided certain ideas for subsequent related research.展开更多
This paper deals with the design and development of the observational system of geo-electrical resistivity on the basis of the demands for exploring the temporal variations of electrical properties of Earth media in t...This paper deals with the design and development of the observational system of geo-electrical resistivity on the basis of the demands for exploring the temporal variations of electrical properties of Earth media in the fixed points of the networks, which would be associated with the earthquake preparation. The observation system is characterized by the high accuracy in measurement, long term stability in operation and high level of rejection to the environmental interference. It consists of three main parts, configuration system measurement system, the calibration and inspection system.展开更多
Multi-sensor vision system plays an important role in the 3D measurement of large objects.However,due to the widely distribution of sensors,the problem of lacking common fields of view（FOV） arises frequently,which m...Multi-sensor vision system plays an important role in the 3D measurement of large objects.However,due to the widely distribution of sensors,the problem of lacking common fields of view（FOV） arises frequently,which makes the global calibration of the vision system quite difficult.The primary existing solution relies on large-scale surveying equipments,which is ponderous and inconvenient for field calibrations.In this paper,a global calibration method of multi-sensor vision system is proposed and investigated.The proposed method utilizes pairs of skew laser lines,which are generated by a group of laser pointers,as the calibration objects.Each pair of skew laser lines provides a unique coordinate system in space which can be reconstructed in certain vision sensor＇s coordinates by using a planar pattern.Then the geometries of sensors are computed under rigid transformation constrains by taking coordinates of each skew lines pair as the intermediary.The method is applied on both visual cameras with synthetic data and a real two-camera vision system;results show the validity and good performance.The prime contribution of this paper is taking skew laser lines as the global calibration objects,which makes the method simple and flexible.The method need no expensive equipments and can be used in large-scale calibration.展开更多
This paper reviews the data quality and impact of observations from the FY-3 satellite series used operationally in the ECMWF system. This includes data from the passive microwave radiometers MWHS-1, MWHS-2 and MWRI, ...This paper reviews the data quality and impact of observations from the FY-3 satellite series used operationally in the ECMWF system. This includes data from the passive microwave radiometers MWHS-1, MWHS-2 and MWRI, as well as observations from the radio occultation receiver GNOS. Evaluations against background equivalents show that the quality of the observations is broadly comparable to that of similar instruments on other polar-orbiting satellites, even though biases for the passive microwave observations can be somewhat larger and more complex for some channels. An observing system experiment shows that the FY-3 instruments jointly contribute significantly to the forecast skill in the ECMWF system. Positive impact of up to 2% is seen for most variables out to the day-2 forecasts over hemispheric scales, with significant benefits for total column water vapor or for temperature and wind in the stratosphere out to day 4.展开更多
The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test rea...The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test reactor,and HL-2 A.Neutron fluxes can provide real-time parameters for nuclear fusion,including neutron source intensity and fusion power.Corresponding to different nuclear reaction periods,neutron fluxes span over seven decades,thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously.Therefore,it is crucial to design a real-time NFM system to encompass such a wide dynamic range.In this study,a high-precision NFM system with a wide measurement range of neutron flux is implemented using realtime multipoint linear calibration.It can automatically switch between counting and Campbelling modes with variations in the neutron flux.We established a testing platform to verify the feasibility of the NFM system,which can output the simulated neutron signal using an arbitrary waveform generator.Meanwhile,the accurate calibration interval of the Campbelling mode is defined well.Based on the above-mentioned design,the system satisfies the requirements,offering a dynamic range of 10~8 cps,temporal resolution of 1 ms,and maximal relative error of 4%measured at the signal-to-noise ratio of 15.8 dB.Additionally,the NFM system is verified in a field experiment involving HL-2 A,and the measured neutron flux is consistent with the results.展开更多
A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarizati...A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarization radar （[PR） has inherent cross-polarization measurement error. The proposed method can effectively eliminate this error, and thus enhance the polarization scattering matrix （PSM） measurement precision. The phase error caused by digital receiver＇s direct IF sampling and mixing of two orthogonal polarization channels can be removed. Consequently, the inherent error of target polarization scattering measurement of the instantaneous polarization radar system is well revised. It has good reference value for further ploarimetric calibration and high practical application prospect.展开更多
The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating ...The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating the local cooling rate of M42 high-speed steel(HSS)in the ESR process.After resolidification at different cooling rates under high-temperature laser confocal microscopy,the carbide network spacing of the specimen was observed using a scanning electron microscope.A functional relationship between the cooling rate and average carbide network spacing was established.The average local cooling rate of the solidification process of the M42 HSS ingot was calibrated.The results show that the higher the cool-ing rate,the smaller the network spacing of the carbides.For the steel ingot with a diameter of 360 mm,the average local cooling rate was 0.562℃/s at the surface,0.057℃/s at the position of 0.25D(where D is the diameter of the ingot),and 0.046℃/s at the center of the ingot.展开更多
Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-t...Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-time coordinate of an object in a certain coordinate system can be obtained, and further dynamic displacement data and curve of the object can also be achieved. That is, automatic gathering and real-time processing of data can be carried out by this system simultaneously. For this system, first, an untouched monitoring technique is adopted, which can monitor or detect objects several to hundreds of meters apart; second, it has flexible installation condition and good monitoring precision of sub-millimeter degree; third, it is fit for dynamic, quasi-dynamic and static monitoring of large engineering structures. Through several tests and applications in large bridges, good reliability and dominance of the system is proved.展开更多
Doped elements in alloys significantly impact their performance.Conventional methods usually sputter the surface material of the sample,or their performance is limited to the surface of alloys owing to their poor pene...Doped elements in alloys significantly impact their performance.Conventional methods usually sputter the surface material of the sample,or their performance is limited to the surface of alloys owing to their poor penetration ability.The X-ray K-edge subtraction(KES)method exhibits great potential for the nondestructive in situ detection of element contents in alloys.However,the signal of doped elements usually deteriorates because of the strong absorption of the principal component and scattering of crystal grains.This in turn prevents the extensive application of X-ray KES imaging to alloys.In this study,methods were developed to calibrate the linearity between the grayscale of the KES image and element content.The methods were aimed at the sensitive analysis of elements in alloys.Furthermore,experiments with phantoms and alloys demonstrated that,after elaborate calibration,X-ray KES imaging is capable of nondestructive and sensitive analysis of doped elements in alloys.展开更多
文摘A recent single-center retrospective study proposed novel combinations of hematological parameters and scoring systems for predicting severe acute pancre-atitis.While these combinations showed promising predictive performance,several limitations warrant consideration,including the lack of calibration,the absence of key inflammatory markers such as procalcitonin,and practical challenges in integrating these models into routine clinical workflows.To improve predictive accuracy and clinical applicability,prospective validation and the inclusion of additional variables are recommended.
基金supported by the National Natural Science Foundation of China(42276199).
文摘In order to get rid of the dependence on high-precision centrifuges in accelerometer nonlinear coefficients calibration,this paper proposes a system-level calibration method for field condition.Firstly,a 42-dimension Kalman filter is constructed to reduce impact brought by turntable.Then,a biaxial rotation path is designed based on the accelerometer output model,including orthogonal 22 positions and tilt 12 positions,which enhances gravity excitation on nonlinear coefficients of accelerometer.Finally,sampling is carried out for calibration and further experiments.The results of static inertial navigation experiments lasting 4000 s show that compared with the traditional method,the proposed method reduces the position error by about 390 m.
基金the National Natural Science Foundation of China(No.61927822)。
文摘Traditional calibration method for the digital inclinometer relies on manual inspection,and results in its disadvantages of complicated process,low-efficiency and human errors easy to be introduced.To improve both the calibration accuracy and efficiency of digital inclinometer,an automatic digital inclinometer calibration system was developed in this study,and a new display tube recognition algorithm was proposed.First,a high-precision automatic turntable was taken as the reference to calculate the indication error of the inclinometer.Then,the automatic inclinometer calibration control process and the digital inclinometer zero-setting function were formulated.For display tube recognition,a new display tube recognition algorithm combining threading method and feature extraction method was proposed.Finally,the calibration system was calibrated by photoelectric autocollimator and regular polygon mirror,and the calibration system error and repeatability were calculated via a series of experiments.The experimental results showed that the indication error of the proposed calibration system was less than 4",and the repeatability was 3.9".A digital inclinometer with the resolution of 0.1°was taken as a testing example,within the calibration points'range of[-90°,90°],the repeatability of the testing was 0.085°,and the whole testing process was less than 90 s.The digital inclinometer indication error is mainly introduced by the digital inclinometer resolution according to the uncertainty evaluation.
基金the Knowledge Innovation Program of Basic Re-search Projects of Shenzhen for their support under Grant No.JCYJ20200109142805928the funding provided by the Basic and Applied Basic Research Foundation of Guangdong Provinæunder Grant No.2021A1515220113partially supported by the Guangzhou Municipal Science and Technology Project under Grant 202102010421.
文摘In clinical environments,the prolonged utilization of polarization equipment can result in theaccumulation of errors over extended periods.The absence of expeditious calibration techniques in clinical practice presents a significant obstacle in preserving the precision and dependability of these instruments.To address this challenge,we propose an innovative research study that presents a comprebersive calibration system specifically designed for the calibration of the backscattering Muellet matrix measurement system,enabling swift online calibration acroes various scenarios.This system employs an external calibration framework for rmal-time adjust-ment of the polarizer's initial angle,oversecing the rotation of PSG and PSA motors through position measurement and control procedures,with light intensity monitored by a camera.By incorporating moment um concepts and the Adam optimization algorithm,we enhance conver-gence speed,mitigate noise,and improve calibration accuracy.Experimental results showcase the exceptional precision,speed,and robustness of oрroposed method,achieving high acсuracy and minimal error,thereby offering a promising solution for maintaining the reliabilit y of polarization equipment in clinical settings.
基金General Project of Basic Research Plan for Natural Sciences in Shaanxi Province,grant number 2023-JC-YB-244Youth Project of Basic Research Plan for Natural Sciences in Shaanxi Province,grant number 2024JC-YBQN-0253.
文摘Vector magnetic measurement is increasingly widely used.In order to improve the accuracy of vector magnetic measurement system on board a vehicle,researchers have proposed various calibration methods.Most of them require altering the magnetic vector in the vehicle coordinate system.Exploring the use of geomagnetic variation to change the geomagnetic vector in the vehicle coordinate system,this paper proposes a novel vector magnetic measurement calibration method.In this method,a vector magnetometer mounted on a vehicle and an accurate vector magnetometer separately measure the geomagnetic field at diff erent locations within the same area.Based on the physical principle that the geomagnetic variation at two nearby locations is equal,the calibration parameters of the magnetometer on the vehicle can be determined through a set of equations containing the measurements from the two magnetometers.The theoretical derivation and simulation experiment results demonstrate the feasibility of this method.Therefore,it can serve as a new alternative calibration method,especially in scenarios where a high degree of accuracy in the estimation of calibration parameters is not required.
基金supported by the Jiangsu Provincial Key Research and Development Program(BE2022072)the National Natural Science Foundation of China(12141304)the Natural Science Foundation of Jiangsu Province(BK20231134).
文摘To address the installation challenges of a 2-m ring Gregorian telescope system,and similar optical systems with a small width-to-radius ratio,we propose a detection method combining local interferometry with a comparison model.This method enhances the precision of system calibration by establishing a dataset that delineates the relationship between secondary mirror misalignment and wavefront aberration,subsequently inferring the misalignment from interferometric detection results during the calibration process.For the 2-m ring telescope,we develop a detection model using five local sub-apertures,enabling a root-mean-square detection accuracy of 0:0225λ(λ=632:8 nm)for full-aperture wavefront aberration.The calibration results for the 2-m Ring Solar Telescope system indicate that the root-mean-square value of sub-aperture wavefront aberration reaches 0.104λ,and the root-mean-square value of spliced full-aperture measurement yields reaches 0.112λ.This method offers a novel approach for calibrating small width-toradius ratio telescope systems and can be applied to the calibration of other irregular-aperture optical systems.
文摘Based on error analysis, the influence of error sources on strapdown inertial navigation systems is discussed. And the maximum permissible component tolerances are established. In order to achieve the desired accuracy (defined by circular error probability), the types of appropriate sensors are chosen. The inertial measurement unit (IMU) is composed of those sensors. It is necessary to calibrate the sensors to obtain their error model coefficients of IMU. After calibration tests, the accuracy is calculated by uniform design method and it is proved that the accuracy of IMU is satisfied for the desired goal.
文摘A new distributed test system composed of multiple test nodes was designed by adopting storage test technology to test shock waves in explosion field. The advantage of the system is the application of sensor lattice whose rise time is microsecond level, which can quickly response to transient shock wave signals. In order to reduce dynamic response error, shock tube is employed to conduct dynamic calibration on the system. The overpressure peak values of the explosion shock wave collected by sensor lattice were used to construct a shock wave pressure field with B-spline interpolation algorithm.
文摘A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, spe cified in spherical coordinates, is generated first, which is then used to calibrate the tracking results by a two dimensional interpolation. The scheme can effectively correct the static errors in the magnetic tracking system. The employment of spherical coordinates significantly reduces the calculation complexity in calibration.
文摘A plane-based and linear camera calibration technique without considering lens distortion is proposed in a greedy and intuitive framework for the binocular camera system. Characteristic homography matrix and consistency constraints in close range are employed in this calibration. First, in order to calculate the internal geometries of the cameras, total least-square fitting as a robust tool for the geometrical cost function is exploited to recover the accurate principal point of each camera from all the characteristic lines of the homography matrices for all model planes. Secondly, generic prior knowledge of the aspect ratio of pixel cells is incorporated into the system to obtain the exact principal length in each camera. Thirdly, extrinsic geometries are accurately computed for all planar patterns with respect to each monocular camera. Finally, the rigid displacement between binocular cameras can be obtained by imposing the consistency constraints in 3-space geometry. Both simulation and real image experimental results indicate that reasonably reliable results can be obtained by this technique. And the proposed method is sufficient for applications where high precision is not required and can be easily performed by common computer users who are not experts in computer vision.
文摘A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine. This machine is designed to serve a specific purpose to attain high accuracy and high efficiency grinding of turbine blades by eliminating the hand grinding process. Although its topology is RPPPR （P： prismatic; R： rotary）, its design is quite distinct from the competitive machine tools. As error quantification is the only way to investigate, maintain and improve its accuracy, calibra- tion is recommended for its performance assessment and acceptance testing. Systematic geometric error modeling technique is implemented and 52 position dependent and position independent errors are identified while considering the machine as five rigid bodies by eliminating the set-up errors of workpiece and cutting tool. 39 of them are found to have influential errors and are accommodated for finding the resultant effect between the cutting tool and the workpiece in workspace volume. Rigid body kinematics techniques and homogenous transformation matrices are used for error synthesis.
基金Natural Science Foundation of Guangdong Province(Grant No.2021A1515011208)National Natural Scientific Foundation of China(Grant No.81671788)+1 种基金National Science Foundation for Young Scientists of China(Grant No.81701662)The Joint Found of National Science Foundation of China and GuangDong Provincial Government(Grant No.U1301258).
文摘At present,dental implant surgery mainly relies on the clinical experience of the doctor and the assistance of preoperative medical imaging.However,there are some problems in dental implant surgery,such as narrow space,sight obstruction,inaccurate positioning,and high requirements of doctors’proficiency.Therefore,a dental implant robot system(DIRS)guided by optical navigation is developed in this study,with an x-shaped tool and an irregular pentagonal tracer are designed for spatial registration and needle tip positioning strategy respectively.The coordinate system of each unit in DIRS is unified through system calibration,spatial registration,and needle tip positioning strategy.Then the surgical path is planned on the computed tomography(CT)images in the navigation software before operation.The automatic positioning method and the auxiliary positioning method can be used in the operation to achieve accurate positioning and assist doctors to complete the operation.The errors of spatial registration,needle tip positioning strategy,and the overall accuracy of the system were evaluated respectively,and the results showed that they all met the needs of clinical surgery.This study preliminarily verified the feasibility of the precise positioning method for dental surgery robots and provided certain ideas for subsequent related research.
文摘This paper deals with the design and development of the observational system of geo-electrical resistivity on the basis of the demands for exploring the temporal variations of electrical properties of Earth media in the fixed points of the networks, which would be associated with the earthquake preparation. The observation system is characterized by the high accuracy in measurement, long term stability in operation and high level of rejection to the environmental interference. It consists of three main parts, configuration system measurement system, the calibration and inspection system.
基金supported by National Natural Science Foundation of China (Grant No. 60804060)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200800061003)
文摘Multi-sensor vision system plays an important role in the 3D measurement of large objects.However,due to the widely distribution of sensors,the problem of lacking common fields of view（FOV） arises frequently,which makes the global calibration of the vision system quite difficult.The primary existing solution relies on large-scale surveying equipments,which is ponderous and inconvenient for field calibrations.In this paper,a global calibration method of multi-sensor vision system is proposed and investigated.The proposed method utilizes pairs of skew laser lines,which are generated by a group of laser pointers,as the calibration objects.Each pair of skew laser lines provides a unique coordinate system in space which can be reconstructed in certain vision sensor＇s coordinates by using a planar pattern.Then the geometries of sensors are computed under rigid transformation constrains by taking coordinates of each skew lines pair as the intermediary.The method is applied on both visual cameras with synthetic data and a real two-camera vision system;results show the validity and good performance.The prime contribution of this paper is taking skew laser lines as the global calibration objects,which makes the method simple and flexible.The method need no expensive equipments and can be used in large-scale calibration.
基金We acknowledge funding from the EUMETSAT Fellowship Programme for Heather LAWRENCE,Katrin LONITZ and David DUNCAN.
文摘This paper reviews the data quality and impact of observations from the FY-3 satellite series used operationally in the ECMWF system. This includes data from the passive microwave radiometers MWHS-1, MWHS-2 and MWRI, as well as observations from the radio occultation receiver GNOS. Evaluations against background equivalents show that the quality of the observations is broadly comparable to that of similar instruments on other polar-orbiting satellites, even though biases for the passive microwave observations can be somewhat larger and more complex for some channels. An observing system experiment shows that the FY-3 instruments jointly contribute significantly to the forecast skill in the ECMWF system. Positive impact of up to 2% is seen for most variables out to the day-2 forecasts over hemispheric scales, with significant benefits for total column water vapor or for temperature and wind in the stratosphere out to day 4.
基金supported by the National Natural Science Foundation of China(Nos.11475131,11975307,and 11575184)the National Magnetic Confinement Fusion Energy Development Research(No.2013GB104003)。
文摘The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test reactor,and HL-2 A.Neutron fluxes can provide real-time parameters for nuclear fusion,including neutron source intensity and fusion power.Corresponding to different nuclear reaction periods,neutron fluxes span over seven decades,thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously.Therefore,it is crucial to design a real-time NFM system to encompass such a wide dynamic range.In this study,a high-precision NFM system with a wide measurement range of neutron flux is implemented using realtime multipoint linear calibration.It can automatically switch between counting and Campbelling modes with variations in the neutron flux.We established a testing platform to verify the feasibility of the NFM system,which can output the simulated neutron signal using an arbitrary waveform generator.Meanwhile,the accurate calibration interval of the Campbelling mode is defined well.Based on the above-mentioned design,the system satisfies the requirements,offering a dynamic range of 10~8 cps,temporal resolution of 1 ms,and maximal relative error of 4%measured at the signal-to-noise ratio of 15.8 dB.Additionally,the NFM system is verified in a field experiment involving HL-2 A,and the measured neutron flux is consistent with the results.
基金supported by the National Natural Science Priority Foundation of China(60736006)National Natural Science Foundation of China for Youth(60802078)+1 种基金National Basic Research Program(973 Program)(51314)Hunan Provincial Innovation Foundation for Postgraduate
文摘A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarization radar （[PR） has inherent cross-polarization measurement error. The proposed method can effectively eliminate this error, and thus enhance the polarization scattering matrix （PSM） measurement precision. The phase error caused by digital receiver＇s direct IF sampling and mixing of two orthogonal polarization channels can be removed. Consequently, the inherent error of target polarization scattering measurement of the instantaneous polarization radar system is well revised. It has good reference value for further ploarimetric calibration and high practical application prospect.
基金the National Natural Science Foundation of China(Nos.51974153,U1960203,and 51974156)the Joint Fund of State Key Laboratory of Marine Engineering and University of Science and Technology Liaoning(SKLMEA-USTL-201901,SKLMEA-USTL-201707)China Scholarship Council(201908210457).
文摘The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating the local cooling rate of M42 high-speed steel(HSS)in the ESR process.After resolidification at different cooling rates under high-temperature laser confocal microscopy,the carbide network spacing of the specimen was observed using a scanning electron microscope.A functional relationship between the cooling rate and average carbide network spacing was established.The average local cooling rate of the solidification process of the M42 HSS ingot was calibrated.The results show that the higher the cool-ing rate,the smaller the network spacing of the carbides.For the steel ingot with a diameter of 360 mm,the average local cooling rate was 0.562℃/s at the surface,0.057℃/s at the position of 0.25D(where D is the diameter of the ingot),and 0.046℃/s at the center of the ingot.
基金Supported by the National Natural Science Foundation of China （No.50378041） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.2003487016）.
文摘Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-time coordinate of an object in a certain coordinate system can be obtained, and further dynamic displacement data and curve of the object can also be achieved. That is, automatic gathering and real-time processing of data can be carried out by this system simultaneously. For this system, first, an untouched monitoring technique is adopted, which can monitor or detect objects several to hundreds of meters apart; second, it has flexible installation condition and good monitoring precision of sub-millimeter degree; third, it is fit for dynamic, quasi-dynamic and static monitoring of large engineering structures. Through several tests and applications in large bridges, good reliability and dominance of the system is proved.
基金supported by the National Key Research and Development Program of China(Nos.2017YFA0403801,2017YFA0206004,2018YFC1200204)the National Natural Science Foundation of China(NSFC)(Nos.81430087,11775297,U1932205).
文摘Doped elements in alloys significantly impact their performance.Conventional methods usually sputter the surface material of the sample,or their performance is limited to the surface of alloys owing to their poor penetration ability.The X-ray K-edge subtraction(KES)method exhibits great potential for the nondestructive in situ detection of element contents in alloys.However,the signal of doped elements usually deteriorates because of the strong absorption of the principal component and scattering of crystal grains.This in turn prevents the extensive application of X-ray KES imaging to alloys.In this study,methods were developed to calibrate the linearity between the grayscale of the KES image and element content.The methods were aimed at the sensitive analysis of elements in alloys.Furthermore,experiments with phantoms and alloys demonstrated that,after elaborate calibration,X-ray KES imaging is capable of nondestructive and sensitive analysis of doped elements in alloys.
