Real-time Calibration Method Research Articles

A real-time calibration method based on time-to-digital converter for accelerator timing system

A real-time calibration method based on time-to-digital converter for accelerator timing system

Accurate relative measurement of multitarget poses by monocular vision for nonmodel-based real-time calibration of industrial robot

On basis of multitarget poses measured by monocular vision, a nonmodel-based real-time calibration method for six-DoF industrial robot is presented. Markers fixed on base and joints of robot are measured by a camera synchronously, at each measurement configuration selected with constraints of marker visibility and work trajectory, to provide decoupled pose data. The accuracy problem due to low precision of camera is addressed by substituting absolute measurement of movable markers with relative measurement from a static marker to the movable ones. On this basis, the deviated pose of each joint can be obtained accurately and the actual kinematic parameters of robot are obtained. The simulation verifies the selection algorithm of measurement configurations and evaluates the effects of decisive error sources on measurement accuracy. The experiment demonstrates the advantage of relative pose measurement using the low-cost camera on calibration accuracy by comparison with typical model-based calibrations using a precise laser tracker.

Enhancing inter-subject reproducibility in insulin bioavailability measurements through real-time calibration

A real-time calibration to enhance the inter-subject reproducibility of insulin bioavailability measurements was proposed and validated on a diabetic patient with more than 49000 impedance values. The measurement method monitors drug absorption through a transducer consisting of a sensitive material (human abdominal tissue) and an impedance spectrometer. The in-vivo experiments revealed a statistically significant negative second-order polynomial trend in impedance magnitude corresponding to the amount of rapid-acting insulin injected. To manage the uncertainty inherent in the sensing block, the method integrates real-time calibration. Implementing a real-time calibration method based on a customized model identification at each insulin administration resulted in a reduction in deterministic error by a factor of 18. A further reduction in deterministic error for clinical application (46%) was achieved with a customized parameter second-order polynomial model with respect to the customized parameter linear model. Lastly, when less conductive long-acting insulin was administered, an increasing trend in impedance magnitude was observed, aligned with the theoretical framework of the proposed method.

A three-dimensional vision measurement method based on double-line combined structured light

In this paper, a structured light vision measurement method using a scanning laser line and a positioning laser line is proposed. The novel method enables the scanning laser plane to slide along a slide rail while maintaining intersection with the positioning laser plane, eliminating the need to determine the scanning direction and moving step. During the measurement process, the laser plane equations need to be recalibrated for each new position, so a real-time calibration method is given. Initially, the geometric barycenter method is employed to detect the subpixel coordinates of the light stripe intersection point. Subsequently, these coordinates are projected into the camera coordinate system using the initial equations of the positioning laser plane. Finally, leveraging the normal information of the initial equation of the scanning laser plane and the three-dimensional coordinates of the light stripe intersection point, the real-time calibration of the scanning laser plane equations can be accomplished. The proposed method enables the three-dimensional reconstruction of objects, and its accuracy is verified through measurements on gauge blocks. Experimental results demonstrate that this method achieves precise and stable three-dimensional reconstruction of object surface shape.

Real-time Bayesian model calibration method for C/SiC mechanical behavior considering model bias

The mechanical behavior of C/SiC composites has significant nonlinear and dispersion. To obtain the real mechanical behavior of C/SiC composites in actual structure, a real-time calibration method for mechanical behavior of C/SiC composites based on the dynamic Bayesian network (DBN) is proposed. The epistemic uncertainty of the mechanical behavior is introduced in the form of model bias. The method comprises offline and online phases. Firstly, the surrogate model of the mechanical behavior is built based on the proper orthogonal decomposition and the Gaussian process model offline. Then, based on the DBN, model parameters can be continuously calibrated by the sensor data online. The validity of the method is verified by the uniaxial tensile test of C/SiC composites. The results show that the proposed method can real-time accurately calibrate and predict the mechanical behavior of all the C/SiC samples and the introduction of the model bias is of great significance.

A real-time calibration method for the numerical pollen forecast model COSMO-ART

Technologies for monitoring pollen concentrations in real-time made substantial advances in the past years and become increasingly available. This opens the possibility to calibrate numerical pollen forecast models in real-time and make a significant step forward regarding the quality of pollen forecasts. We present a method to use real-time pollen measurements in numerical pollen forecast models. The main idea is to calibrate model parameterizations and not to assimilate measurements in a nudging sense. This ensures that the positive effect persists throughout the forecast period and does not vanish after a few forecast hours. We propose to adapt in real-time both the model phenology scheme and the overall tuning factor that are present in any numerical pollen forecast model. To test this approach, we used the numerical pollen forecast model COSMO-ART (COnsortium for Small-scale MOdelling-Aerosols and Reactive Trace gases) on a mesh size of 1.1 km covering the greater Alpine domain. Test runs covered two pollen seasons and included Corylus, Alnus, Betula and Poaceae pollen. Comparison with daily measurements from 13 Swiss pollen stations revealed that the model improvements are large, but fine-tuning of the method remains a challenge. We conclude that the presented approach is a first valuable step towards comprehensive real-time calibration of numerical pollen forecast models.

Sound pressure level real-time monitoring of outdoor directional noise

A single microphone can’t select an efficient target signal from a mixed sound source when measuring the sound pressure level (SPL) of a target noise source in an outdoor environment. Therefore, a microphone array is used to enhance the target signal through beamforming to restrain the interference of non-target signals effectively. Owing to their advantages of small size and low price, micro-electro-mechanical system (MEMS) microphone arrays are widely used. However, MEMS microphone mismatch commonly occurs due to production tolerances as well as aging effects. To calibrate the SPL measurement difference caused by the whole mismatch microphone array when outdoor noise monitoring is performed, a real-time calibration method was introduced in this study by compensating for the SPL difference between the reference microphone and MEMS microphone array. The circular harmonics domain-multiple signal classification sound source localization algorithm was utilized to select the effective target signal component in the time–frequency domain, and the standard transfer functions of the reference microphone were utilized to correct the SPL measurement bias of the array. To verify the feasibility of the method, the consistency of the compensating SPL difference between multi-noise and single-target noise environments was experimentally investigated. The calibration method exhibited good accuracy and robustness based on the results and can also be applied to spherical microphone array noise monitoring device.

A real-time calibration method of magnetometer array’s misalignment errors with ac modulated three-axis coil

The misalignment errors of magnetometer array are vulnerable to vibrations, which deteriorates the magnetic anomaly detection performance severely and brings strong demands for real-time calibrations. We propose a real-time calibration method of magnetometer array’s misalignment errors, which utilizes a standard three-axis coil to generate an alternating current magnetic field with varied magnitudes and directions. Then the misalignment errors are calibrated by minimizing the difference between experimentally calibrated magnetic fields of magnetometers and theoretically calculated magnetic fields of coils with the Levenberg–Marquardt algorithm and Biot-Savart’s law. It does not require the expensive high-precision non-magnetic rotation platform, homogenous magnetic environment and additional scalar magnetometer compared to the conventional methods, which facilitates the real-time calibration with ambient magnetic fluctuations. The investigations demonstrate that the X-axis magnetic field gradient is decreased from 3665 nT to 68 nT and localization error is reduced from 1.6 m to 0.11 m with the proposed calibration method.

Process-oriented SWMM real-time correction and urban flood dynamic simulation

The real-time calibration of SWMM runoff parameters is of great significance for the accurate simulation and prediction of urban flooding. Many studies correct SWMM based on the characteristic indicators of the flood. The model parameters do not change during the flooding process, making the model effective in simulating historical flooding but poor performance in the prediction process. By analyzing the distribution characteristics of urban waterlogging points, a real-time model calibration method is proposed to adjust the model parameters from time to time during the flooding process to minimize the error between the water depth of the waterlogging point and the measured water depth. A practical application in the central area of Zhengzhou, China, the results show that the method can accurately fit the water depth process within 4 iterations and final Nash efficiency coefficients (NSE) are all above 0.8. The process-oriented real-time calibration of SWMM runoff parameters can endow the model with dynamic correction capability and improve the simulation accuracy of the flooding process, which has important fundamental significance for flood loss assessment and risk assessment.

0.79\u2009ppm scale-factor nonlinearity whole-angle microshell gyroscope realized by real-time calibration of capacitive displacement detection

Whole-angle gyroscopes have broad prospects for development with inherent advantages of excellent scale factor, wide bandwidth and measurement range, which are restrictions on rate gyroscopes. Previous studies on the whole-angle mode are based mostly on the linear model of Lynch, and the essential nonlinearity of capacitive displacement detection is always neglected, which has significant negative effects on the performance. In this paper, a novel real-time calibration method of capacitive displacement detection is proposed to eliminate these nonlinear effects. This novel method innovatively takes advantage of the relationship between the first and third harmonic components of detective signals for calibration. Based on this method, the real-time calibration of capacitive displacement detection is achieved and solves the problems of traditional methods, which are usually related to the vibration amplitude, environmental variations and other factors. Furthermore, this novel calibration method is embedded into a whole-angle control system to restore the linear capacitive response in real time and then combined with a microshell resonator for the first time to exploit the enormous potential of an ultrahigh Q factor and symmetric structure. The effectiveness is proven because the angle drift is reduced significantly to improve the scale-factor nonlinearity by 14 times to 0.79 ppm with 0.0673°/h bias instability and a 0.001°/s rate threshold, which is the best reported performance of the MEMS whole-angle gyroscope thus far. More importantly, this novel calibration method can be applied for all kinds of resonators with the requirement of a linear capacitive response even under a large resonant amplitude.

Improving the Structure of a Signal Used for Real-Time Calibrating of the Receiving Channels of Digital Transceiver Modules in Digital Phased Antenna Arrays

Introduction. Modern digital phased array antenna (DPAA) systems incorporate a large number of identical transceiver modules (TMs). These modules require real-time calibration with a high level of accuracy. In a previous work, we proposed a real-time calibration method for all receiver channels, which is based on the use of a calibration signal (CalSig) of the same frequency spectrum as the reflected signal and modulated in phase and amplitude by BPSK and OOK codes, respectively. This method was found to have a number of advantages over conventional approaches. However, the use of the same CalSig sample for all receiving channels increases the noise power gain at the output of a digital beam-forming unit (DBU). To overcome this limitation, we set out to improve the structure of CalSigs by making them pseudo-orthogonal. As a result, the noise power gain at the DBU output can be significantly reduced compared to that obtained in our previous work.Aim. To propose an improved design of a controlled amplitude modulation code OOK generator, which allows creation of pseudo-orthogonal CalSigs. As a result, the noise power gain at the output will increase insignificantly, thus having no negative effect on the quality of digital beam forming, signal processing and calibration.Materials and methods. Theory of system engineering and technology; theory of digital signal processing; system analysis; mathematical modeling.Results. An improved CalSig for calibrating the receiving channels of TMs was obtained. A structural diagram allowing the formation of pseudo-orthogonal CalSigs was synthesized.Conclusions. We proposed a new approach to improving the structure of signals used for real-time calibrating the DPAA receiving channels. A structural diagram of an amplitude-modulated OOK code generator for pseudo-orthogonal CalSigs was developed.

Real-time continuous calibration method for an ultraviolet camera.

The accuracy of SO2 cameras is significantly determined by the ability to obtain an accurate calibration. This work presents a real-time continuous calibration method for SO2 cameras with a moderate resolution spectrometer by taking realistic radiative transfer into account. The effectiveness and accuracy of the proposed method have been verified through simulations and experiments. The calibration error can be reduced by about 20-80% compared with the commonly used cell calibration, especially for situations of long distance, poor visibility, or optically thick plumes.

A real-time calibration method for the systematic errors of a star sensor and gyroscope units based on the payload multiplexed

With the star sensor and gyroscope units integrated for attitude determination, it will provide continuous and accurate attitude information for satellites with a high update rate. This integration could take full advantage of each other. In order to guarantee the accuracy of satellite attitude determination, the calibration of its systematic errors is of critical importance. In this paper, a calibration method for the star tracker and GUs integrated system is proposed based on the satellite payload multiplexed. Firstly, the satellite attitude kinematics model is introduced. Then the measurement model with respect to the systematic errors including the installation errors and GUs drift errors is built for the star sensor, the payload and the GUs. Finally, the state model and observation model are established, according to which the systematic errors are calibrated by a Kalman filter. Simulation results indicate that the proposed method is effective at estimating the systematic errors of the star sensor and GUs integrated system.

On-line real-time mistuning identification and model calibration method for rotating blisks based on blade tip timing (BTT)

Identifying the mistuning parameters and calibrating the finite element model (FEM) of the mistuned blisk in real-time is a meaningful way to acquire the blisk’s dynamic characteristics and predict its stress response. Because of the wearing and other reasons, the blisk’s mistuning is changing during the operation. Hence a BTT based rotating-blisk mistuning identification and model calibration (BR-IDC) method in real-time has become a necessity. The rotating effects (stiffening, softening and Coriolis force) are considered in the BR-IDC. The synergistic effect of the mass and stiffness mistuning is analyzed, and the effect is presented by a standard mistuning coefficient. Based on the BR-IDC, the on-line real-time mistuning identification for the rotating blisk is realized. Furthermore, the FEM was calibrated by the identification results. The BR-IDC approach is verified by FEM simulation and experimental work. The precision of the FEM is improved through the calibration.

On-Orbit Calibration Method for Redundant IMU Based on Satellite Navigation & Star Sensor Information Fusion

Aiming at the long term and high-precision performance maintenance requirements of the satellite-borne four-axis redundant inertial measurement unit (IMU) in space, the satellite navigation velocity information, the attitude information provided by the star sensor and the redundant measurement output are used as references to derive the measurement model, including the star sensor installation error. Three rotation sequences of optimal observation, sub-optimal observation, and under-observation are designed and compared. The Kalman filter is used to calibrate the redundant IMU in the orbit. The numerical simulation shows that all three rotation sequences can calibrate more than 91% of the constant error, which meets the requirements of the use, and the calibration accuracy of the optimal rotation sequence is the highest. The ground repeatability calibration experiment is carried out 10 times for the optimal rotation sequence. The calibration results show that the range of all the error terms is less than its threshold, illustrating that the calibration result is stable and reliable. It is a real-time calibration method for all error terms on orbit, providing a reference method for the high-precision performance maintenance of the spacecraft integrated navigation system.

Real-Time Estimation and Calibration of GLONASS Inter-Frequency Phase and Code Bias

The frequency division multiple access (FDMA) strategy used in GLONASS causes inter-frequency phase bias (IFPB) and inter-frequency code bias (IFCB) between receivers from different manufacturers. The existence of IFPB and IFCB significantly increases the difficulties of fixing GLONASS ambiguity and limits the accuracy and reliability of GLONASS positioning. Moreover, the initial value of IFPB and IFCB may be unavailable or unreliable with the increasing number of receivers from different manufacturers in recent years. In this study, a real-time and reliable calibration algorithm of IFPB and IFCB based on multi-GNSS assistance is proposed by providing a fixed solution. Real-time IFPB rate and IFCB can be obtained using this algorithm without the initial IFPB and IFCB. The IFPB rate for all GLONASS satellites and IFCB for each GLONASS satellite are estimated due to different characteristics of IFPB and IFCB. IFPB calibration can be divided into constant and real-time IFPB calibrations to meet the different positioning requirements. Results show that constant IFPB rate has only 2 mm difference from the mean value of real-time IFPB rate. The IFPB rate and IFCB estimated by this algorithm have excellent stability, and the change in reference satellite cannot affect the results of IFPB rate and the stability of IFCB. The centimetre-level positioning results can be obtained using two calibration methods, and the positioning results with real-time calibration method are 10%–20% better than those with the constant calibration method. Under satellite-deprived environments, the improvements of multi-GNSS positioning accuracy with constant inter-frequency bias calibration gradually increase as the satellite cut-off elevation angle increases compared with GPS/BDS, which can reach up to 0·9 cm in the vertical direction.

Fully Digital Beamforming Receiver With a Real-Time Calibration for 5G Mobile Communication

This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication. In the real-time calibration method, the received signals of all chains are adjusted to correct the errors of phase and amplitude using the in-band signal other than operating frequency for calibration. The proposed FDBR with real-time calibration is designed and fabricated. The FDBR consists of eight chains of the tapered slot antenna (TSA) element, low noise block (LNB), and software defined radios (SDRs). The $1 \times 8$ array TSA with the directional coupler and the 1:8 divider is designed to send eight uniform calibration signals along with the received signal of all the chains. In SDR, the digital phase shifter and the real-time calibration blocks are implemented to realize digital beamforming. The digital phase shifter has an extremely high resolution of 0.72°. After using the real-time calibration method, the average of measured phase and amplitude error between each chain is less than 0.9° and 0.5 dB, respectively. To verify the beamforming performance of the FDBR, the simulation radiation pattern and the measurement radiation pattern are compared for 0°, ±15°, ±30°, and ±45° beam angles. The simulation results are in good agreement with the measured results. An excellent beamforming performance is achieved in the $1 \times 8$ array FDBR using the real-time calibration.

A Real-time Robotic Calibration Method for Vision-based Bin-picking

A Real-time Robotic Calibration Method for Vision-based Bin-picking

Real-time self-adaptive calibration method for high speed acquisition system.

The main factors that enable capture of complex and transient signals in real-time are improved sampling rates and processing speeds. The time-interleaved architecture is an effective method that allows systems to break through the speed bottleneck of single analog-to-digital converters (ADCs) and go beyond the state-of-the-art process technology limit. However, the performance of the acquisition system may be reduced because of the offset, gain, and time mismatch errors that occur in time-interleaved ADC systems. To correct these errors, this paper first proposes a self-adaptive correction algorithm and then introduces real-time solutions for this algorithm. Finally, the proposed calibration method is implemented in a digital phosphor oscilloscope. Simulations and experimental testing indicate that this system shows good real-time performance and provides a high dynamic performance with an effective number of bits of 7.3 bits and a signal-to-noise ratio of 45.5574 dB.

Real-time rapid initial phase calibration method of phased array in near field

Real-time rapid initial phase calibration method of phased array in near field