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The traditional method of joint calibration of fixed baseline interferometer with multiple errors requires more than three calibration emitters to achieve real-time calibration of the interferometer in orbit, but the performance of the traditional method will be reduced or even failed when the number of calibration emitters is insufficient. For the situation that the number of calibration emitters is insufficient, a single or double emitters calibration method for fixed baseline interferometer is proposed. Under the condition of relative motion between the interferometer and the calibration emitters, a set of phase differences of calibration signals is obtained firstly by multiple measurements, and a set of equations about the systematic errors of the interferometer is listed by using the obtained phase differences, finally the systematic errors are solved by the Penrose inverse matrix assisted iterative least squares method. The simulation results verify the feasibility of the proposed method. On this basis, the influence of the emitter selection on the positioning performance of the interferometer after calibration is analyzed qualitatively by means of numerical simulation, decomposing the parameters of the emitter selection. The analysis results show that the calibration emitter located near the sub-star in the single emitter case or two calibration emitters located far apart both can make the interferometer obtain better positioning performance after calibration.

To prevent severe safety accidents caused by primary coolant leakage in pressurized water reactors (PWRs), it is necessary to monitor the leakage rate of key parts of the reactor coolant pressure boundary (RCPB) in order to take timely countermeasures. The primary coolant of PWRs is usually high-pressure supercritical water containing boron, which can produce 18F in the high neutron flux environment of the reactor. The leak rate of the RCPB can be inferred by measuring the activity concentration of the radioactive 18F aerosol produced by the coolant leaking into the containment. A measurable sample source is usually obtained by extracting sample gas containing 18F aerosol from the containment and filtering it in the monitor. The measurement method used by the monitor is to screen the γ signal by using the β signal as the gate signal, which is actually a γ relative measurement method using the coincidence method to reduce the background. The electronic design of the monitor prevents the β-channel signal from being recorded, which makes it impossible to achieve the absolute measurement as with conventional coincidence methods. To ensure the accuracy of the monitoring results, the 18F aerosol monitor needs to be calibrated. In this paper the monitor was calibrated using a standard 18F surface source produced by the intermittent spot method on a filter paper base. By means of the decay of the 18F source and the automatic recording function of the monitor, the indication number of the monitor was measured at six source activities of different orders of magnitude, i.e. the count of the energy spectrum at the position of the 511 keV γ-window. The data were used to obtain the activity response and uncertainty of the monitor's readings and to verify the feasibility of such a calibration scheme on the monitor. Two standard point sources of 22Na and 68Ge/68Ga were also used to calibrate the monitor to verify the feasibility of using long-lived nuclides to make alternative sources for calibration. Sets of 511 keV γ-window count data from γ and coincidence channels were recorded to investigate the effect of the γ coincidence additive effect and different β emission spectra on the activity response, and to determine which long-lived positron nuclides should be used in the field calibration. Calibration with a standard 18F surface source shows that the monitor can give stable and reliable readings of this type of standard source over different orders of magnitude within the range. The extended uncertainty (k=2) of the displayed activity response is 6.0%, which meets manufacturing requirements. And the calibration of the long-lived positron nuclide standard point sources shows that the positron spectrum has a great influence on the activity response of the monitor, and the γ coincidence additive effect is not very significant. Therefore, it is recommended to use 22Na with β energy close to 18F to make point sources or surface sources for field calibration.

ObjectiveThis study proposes a design scheme for an underwater magnetic sensor calibration device. The device is composed of an electromagnetic coil and integrated navigation equipment which can be carried on a mobile platform to sail on the water surface, and realize the high-precision calibration of the position and attitude of the underwater magnetic sensor.MethodsAccording to information on the coil's attitude, orientation and trajectory, and the measured values of the magnetic field generated by the coil at the magnetic sensor, the position and attitude of the underwater magnetic sensor can be calculated using a nonlinear optimization algorithm. The mathematical model of the whole system is established and numerical verification tests are carried out, considering the effects of the measuring accuracy of the coil's position and attitude, the magnetic sensor's noise and measuring error, and geomagnetic interference.ResultsWhen the device is used and the magnetic sensor is at a depth of 30 m underwater, the mean value of position error is not more than 0.06 m, and the mean value of attitude error is not more than 0.20°; the accuracy of the magnetic sensor itself is the main factor affecting the calibration accuracy. ConclusionsThe proposed calibration device can achieve the high-precision calibration of the position and attitude of an underwater magnetic sensor at the same time, giving it great application value. It can be widely used in underwater magnetic target detection, resource exploration, medicine and other fields, especially scenarios involving the attitude deviation of underwater magnetic sensors.

Radon is sensitive to the change of strata stress before and after the earthquake. It is an effective element for tracing the structure and seismic activity, and accounts for a large proportion in China’s earthquake precursor observation network. In recent years, due to the aging and updating of instruments, the calibration of radon meters at many stations has been restricted, which further affects the accuracy and reliability of radon observation data. In this paper, the high-precision AlphaGUARD radon meter is used to calibrate the BG2015R radon meter in Ningde No.1 well by using fresh well water and fixed sources with a certain concentration. The relative errors between the new K value and the old K value are 2.83% and 1.1% respectively, and the calibration results meet the observation requirements of China Earthquake Networks Center; At the same time, the average and consistency of the measured values of AlphaGUARD radon meter and BG2015R radon meter in the calibration experiment are calculated and analyzed, and the value suggestions for the calibration of the two sets of instruments are given. The flow and method of the calibration experiment described in this paper can provide a certain technical reference for the calibration of the radon meter operating in the network.

To solve the problem that the flow of robot spraying liquid damping glue cannot automatically adapt to the actual situation in the process of automobile manufacturing, a relational mapping model between spraying flow and production vehicle serial number was established based on robot Karel program and production big data. By compiling the bottom code program executable by the robot, the functional relationship between the serial number of production vehicle and the proportional coefficient of the original spraying flow value for each vehicle and the monitored flow value was automatically calculated, and the actual spraying flow value for each vehicle was automatically calibrated based on the original process parameters. Finally, automatic flow calibration of robot spraying liquid damping glue was realized. The actual spraying flow of each production vehicle fluctuated up and down around the monitored flow value, and the fluctuation range was controlled within ±3%, which met the requirements of automobile manufacturing regarding the stability of spraying quality.

Reliable dynamic simulation model is an important means of vibration improvement. Taking the dynamics model of 5.2 MW wind turbine gearbox bench transmission chain as an example，the dynamics modeling，response evaluation and calibration are described based on the empirical modeling methods in the industry. Based on the sensitivity optimization method，the gear meshing dynamics model is corrected，and the vibration response accuracy of the corrected dynamics model is better，indicating that the empirical modeling method combined with the sensitivity optimization method can establish a relatively reliable dynamics model，and it is an effective method.

Software for calibration and calculation of underground fluid water level based on Android mobile phone APP is a water level calibration table system with calculation，recording，storage and other functions. Its functions include calculation of water level calibration data，calibration information archiving，and inquiry of calibration information and other functions.

The array InSAR system obtains a three-dimensional image of an observed scene using a combination of pulse compression and synthetic and real aperture techniques. However, Antenna Phase Center (APC) errors can occur within a practical array InSAR system, which thus degrades the imaging quality in a height direction. The aim of this paper is to improve calibration problems occurring with APC errors. The effect of APC errors is analyzed, and a calibration method based on the orthogonal subspace principle is proposed that utilizes SAR Single Look Complex (SLC) to obtain the noise subspace through eigenvalue decomposition. The subspace orthogonal principle is then used to solve the APC positions of multiple channels simultaneously. In addition, a calibration scheme for the APC position is presented for application with an array InSAR system. The effectiveness of the proposed calibration method is verified using simulations and experimental results.

There will be different loads along the structure surface when it impacts on the water,which has an important effect on the safety of the capsule structure and the people inside. So the research of water impact has a practical significance in the field of aerospace and military. Base on wedge and arc body model,the test of free fall on the water has been investigated on different situations. Firstly the parameter of PVDF is calibrated in the static and dynamic state,using which the distribution of surface pressure is obtained. Then different situations of the experiment are simulated by LS-DYNA and the test pressures are proved further. The pressures are analyzed by different factors. Finally base on the similarity criteria,the impact response of real aircraft structure are obtained by the test data,which has a valuable reference for the design of structure.

Considering geometry structure characteristics of the manipulator being calibrated and using modified 5-parameter method to describe its geometric patameter errors,an end position error model of the manipulator is proposed. After the zero position calibration of the manipulator,measurement data used in calibration process is obtained by one time ballbar installation.An error identification model is built based on the geometric constraints of closed kinematic chain—composed of the manipulator and ballbar as well as the end position error model,then the manipulator geometric parameters errors are calculated using nonlinear least square iterative method. A calibration experiment is completed,and the errors of the manipulator are compensated by integrated error compensation method. Along two given test end point paths,the ballbar length variation decreased from0. 395 mm,0. 456 mm to 0. 005 mm,0. 010 mm respectively before and after calibration. The research shows that the calibration method is effective and correct,and the position accuracy of the manipulator is improved.

Intends to accurately identify joint stiffness parameters of industrial robot under heavy load condition,firstly,dexterity of the robot in joint space and workspace is determined based on the Frobenius norm of Jacobian matrix,then,the integrated model of load and robot are built by using equivalent torque method,and finally,a deformation error compensation method by directly calculating joint deformation and compensating is put forward. The laser tracker and ABB IRB 6 640 robot are used to conduct kinematic error compensation experiment,joint stiffness identification experiment and joint deformation compensation experiment. The results show this method can effectively compensate joint deformation and thus improve the absolute accuracy of the robot. The positioning error of the robot is significantly reduced from 0. 694 mm to 0. 230 mm,with an accuracy improvement by roughly 67%.

Conventional distributed-target-based polarimetric calibration algorithms estimate polarimetric distortions by assuming that the measured spatially averaged covariance matrix takes a specific form. However, when the underlying surface contains targets that do not satisfy the assumptions employed by those algorithms, the averaged covariance matrix may deviate from the desired form. As a result, poor estimates of distortion parameters may yield. It is known that spherically truncated covariance matrix is robust to outliers. Thus, we introduce it to the polarimetric SAR calibration routine. Experiment results on the airborne SAR data confirm that this method can effectively reduce the uncertainty of distortion estimates, hence improve the robustness of the calibration.

The application performance of Synthetic Aperture Radar (SAR) instruments is generally limited in their capability to acquire radar images with both high-resolution and wide swath coverage. The available swath width of Polarimetric SAR (PolSAR) systems is even more restricted. Recently, a new PolSAR architecture called the Hybrid-Polarity (HP) architecture has attracted worldwide attentions. Compared with conventional linearly-polarized PolSARs, HP architecture based PolSARs have significant advantages such as wider swath coverage and lower hardware requirement. In this paper, the principles of the HP architecture, including system designs, system models and calibration methods are first reviewed. Two implementation difficulties of the HP architecture, concerning calibration issue and transmit configuration are illustrated. In order to overcome these problems, an improved version of the HP architecture is proposed. A prototype system based on this improved HP architecture developed for experimental validation is also introduced. In the latter part of this paper, applications suitable for the HP architecture based PolSARs are reviewed. Since the quadrature-polarimetric (quad-pol) data provided by an HP architecture based PolSAR system may be directly transformed into conventional linearly-polarized quad-pol data, this part of review is mainly focused on the corresponding dual-pol applications, i.e. Compact Polarimetry (CP) applications.

As a new radar technology, the distributed aperture coherent radar would be the next generation radar, which is more easily to transport and less expensive than the traditional large aperture radar. However, the time synchronization and phase synchronization are the key issues for the distributed aperture coherent radar. In the paper, the error sources of time synchronization and phase synchronization are analyzed and the corresponding mathematical models are derived firstly. And then, the impact of synchronization errors on the coherent performance is simulated and the accuracy of time and phase synchronization is presented based on the simulation results. At last, the noncorrelation transmission scheme and the calibration scheme based on the wired transmission are respectively proposed to realize the time synchronization and the phase synchronization. The research on the synchronization problem could be very helpful to realize the new radar technology of distributed aperture coherent radar.

Joint three-dimensional location algorithm aims to get the north, east and height coordinates of each pixel in several adjacent Interferometric Synthetic Aperture Radar (InSAR) scenes simultaneously. Joint calibration is a key procedure to achieve an accurate three-dimensional location. It can ensure the continuity of three-dimensional location among adjacent scenes, and achieve the location of large areas with few Ground Control Points (GCPs) by using Tie Points (TPs). In this paper, a new joint calibration algorithm for airborne interferometric SAR is proposed. It calibrates north, east and height coordinates simultaneously. It employs weighted optimization method to carry out calibration, and introduces weights to calibration to discriminate GCPs and TPs with different coherences and locations. The experimental results on airborne InSAR data show that the three-dimensional location accuracy by using the proposed calibration algorithm is better than that by the traditional method.

The single-transmitting-dual-receiving polarimetric SAR system has only two receving channels, which induces lack of prior information for calibration. Due to the polarization diversity of this kind of system (which operates on different dual and compact polarimetric modes), there has not a general algorithm currently. In this paper, a new general calibration algorithm is proposed for single-transmitting-dual-receiving polarimetric SAR system, which can be widely applied to diverse polarization modes. The transmitting and receiving distortion can be estimated using trihedral, 0° dihedral and 45° dihedral as ideal point targets without any assumption on the scene and system. The basic principle of this new algorithm is induced theoretically. The effect of calibrator error on the distortion estimation is analyzed by simulation. Point targets’calibration results and polarization signatures verify this algorithm.

Ground plane range is a kind of outdoor Radar Cross Section (RCS) test range used for static measurement of full-size or scaled targets. Starting from the characteristics of ground plane range, the impact of environments on targets and calibrators is analyzed during calibration in the RCS measurements. The error of relative calibration produced by the different illumination of target and calibrator is studied. The relative calibration technique used in ground plane range is to place the calibrator on a fixed and auxiliary pylon somewhere between the radar and the target under test. By considering the effect of ground reflection and antenna pattern, the relationship between the magnitude of echoes and the position of calibrator is discussed. According to the different distances between the calibrator and target, the difference between free space and ground plane range is studied and the error of relative calibration is calculated. Numerical simulation results are presented with useful conclusions. The relative calibration error varies with the position of calibrator, frequency and antenna beam width. In most case, set calibrator close to the target may keep the error under control.

The paper introduced structure, working principle, method of installation and calibration of electronic belt weigher, and analyzed causes for error of the electronic belt weigher. Meanwhile, it also put forward methods of reducing errors in metering combined with usage experience of electronic belt weigher.