Self-calibrating Technique Research Articles

Self-calibrating technique for 3D displacement measurement using monocular vision and planar marker

Although the vision-based displacement measurement of structures has been widely studied for decades, it still poses challenges for practical applications, including the issues of calibration and automatic long-term monitoring. This paper introduces a monocular-vision based self-calibrating technique for accurately measuring the 3D structural displacement. The technique utilizes a tailor-made planar marker with unique graph patterns, enabling precise image recognition and PnP resolution. The proposed technique automatically estimates the 3D position and 3D orientation of the marker. The limitations of marker-free techniques in terms of long-term monitoring have also been discussed. The accuracy and robustness of the proposed technique are systematically examined by Monte-Carlo simulation, and then verified by experiments. Results show that accuracy of the proposed technique for 3D displacement measurement is 0.049 mm, which indicates the effectiveness of the technique for automatically measuring and calibrating stereo displacement of structures using monocular vision.

Contribution to a New Algorithm to Perform an Automatic Self-Calibration of Current Sensors

Abstract Sensors calibration plays a crucial role in controlling systems and achieving fault-tolerant control by ensuring accuracy, performance, safety, energy efficiency, and compliance with standards. It is an essential to maintain the reliability and effectiveness of modern control systems across various applications. In this paper, we represent a new algorithm that processes a set of raw data collected by a sensor to find the mapping function that relates the raw data to the real value of the measured signal by the sensor. Working on sensors with an unknown mapping function, unknown parameters, or with external disturbances, that affects their behaviour, represents a problem; moreover, it takes a lot of time and effort to calibrate the sensor before each use. Several techniques were used to overcome these aspects mostly by recording the output of the sensor for different input values that change manually, to calibrate the sensor. However, the represented technique in this paper can easily provide us with the input/output model of a specific sensor by doing only one experiment; it also improves the accuracy of the measurements as it is a self-calibrating technique that reduces the nonlinearity and noise problems to deliver a better estimation of the measured signal, which is validated in this paper experimentally using a low-cost current sensor by comparing the obtained results from this algorithm with the results using the extracted input/output model illustrated in the datasheet. Furthermore, if the sensor is pretty poor, and if the application requires more precision, the provided estimation by the mapping function can be mixed with other sensor/s readings using sensor fusion algorithms to find a more precise value of the input. The represented algorithm can also perform self-calibration while evaluating the functionality of the application and the variations of the temperature and other external disturbances that affect the sensor.

Honey–Water Content Analysis by Mixing Models Using a Self-Calibrating Microwave Method

Microwave techniques, as an indirect approach, can be applied for analyzing water content in honey by way of permittivity measurements. However, these techniques require proper calibration to accurately perform such indirect evaluation. Improper calibration standards used in this calibration process could naturally result in a reduction in the accuracy and thus the performance of dielectric characterization using microwaves. Self-calibrating microwave techniques can reduce the effects of imprecise standards and thus improve the performance of microwave measurements by bypassing the requirement of calibration standards. In this study, we develop a self-calibrating microwave measurement technique to determine the relative permittivity of honey samples and implement binary mixing models to predict adulteration levels of water-adulterated honey. From this implementation, it is observed that the parallel-capacitance mixing model could efficiently be applied to determine the concentration of water adulteration by examining the differences between absolute values of the real parts of the measured and predicted complex permittivities of adulterated honey.

Principal and performance analysis of three typical comparators

This paper discussed 3 innovative comparator topologies proposed in last several years. Depends on the target applications, each of the 3 designs achieved significant performance gains. Compared with conventional design, the comparator with self-calibrating technique has low offset voltage, small die area, low noise, and low power consumption. The comparator with regeneration operating midway realizes dramatically low operation delay with acceptable power consumption. The comparator with latch structure on amplifier stage implements circuit with high speed under low supplied voltage.

A novel approach to high-speed high-resolution on-chip mass sensing

The state-of-the-art mass sensing so far has been rather developed along the resolution axis, reaching atomic-scale detection, than into the direction of high-speed. This paper reports a novel self-calibrating technique, making high-speed inertial mass sensors capable of instant high-resolution particle detection and weighing. The sensing nanoelectromechanical resonator is embedded into a phase-locked loop and the sensor-inherent nonlinear phase–frequency relation is exploited for auto-calibration. A tunable on-chip carbon nanotube based mass balance serves as a case study of small-size and low-cost environmental and healthcare applications. Tunability and a phase-locked loop topology make the system widely universal and invariant to nanotube characteristics. Operational for tube eigenfrequencies up to 385MHz, the circuit integration in a 180nm technology achieves instantaneous zeptogram resolution, while yoctogram precision is obtained within the tenth of a second. These figures of merit range at the physical limits of carbon nanotube resonators, in both mass- and time-resolution.

Simultaneous High-Speed High-Resolution Nanomechanical Mass Sensing

Mass sensing has so far rather developed along the resolution axis, reaching atomic-scale detection, than into the direction of high speed. This letter reports on a novel self-calibrating technique that makes high-speed inertial mass sensors capable of instant high-resolution detection and weighing. The sensing nanoelectromechanical resonator is embedded into a phase-locked loop and the sensor-inherent nonlinear phase-frequency relation is exploited for autocalibration.

A simple self-calibrating method to measure the height of fluorescent molecules and beads at nanoscale resolution.

We describe a simple self-calibrating technique, incident-beam interference sweeping, for measuring the height of fluorescent labels. Using a tilted back-reflecting mirror and a scanning laser beam, a modulated fluorescence emission allows height determination of a label from a surface with a resolution of ∼ 3 nm. In addition, we show that the absolute distance of a label from the top-mounted mirror can be determined with a resolution of a few tens of nanometers over a micrometer range.

Development of Broadband Cavity Ring-Down Spectroscopy for Biomedical Diagnostics of Liquid Analytes

We present a spectrometer for sensitive absorption measurements in liquids across broad spectral bandwidths. The spectrometer combines the unique spectral properties of incoherent supercontinuum light sources with the advantages of cavity ring-down spectroscopy, which is a self-calibrating technique. A custom-built avalanche photodiode array is used for detection, permitting the simultaneous measurement of ring-down times for up to 64 different spectral components at nanosecond temporal resolution. The minimum detectable absorption coefficient was measured to be 3.2 × 10(-6) cm(-1) Hz(-1/2) at 527 nm. We show that the spectrometer is capable of recording spectral differences in trace levels of blood before and after hemolysis.

Self-calibrating technique for terahertz time-domain material parameter extraction

This manuscript introduces a self-calibrating technique for terahertz (THz) time-domain material characterization in transmission mode. The self-calibrating technique utilizes the relations between the multiple transmissions of a transient plane wave through a sample under test in order to extract its material properties. The method presented in this paper is particularly useful in reducing the time required for simultaneous imaging and spectroscopy scans, since existing characterization methods require the knowledge of the waveform of both the plane wave transmitted through a reference sample and the waveform of the plane wave transmitted through the sample under test. The technique presented also ameliorates the problem caused by differences between sample and reference signals due to power and time drifts inherent in a THz system, hence reducing artifacts in the characterization results.

Regularized Least Squares Estimating Sensitivity for Self-calibrating Parallel Imaging

Calibration of the spatial sensitivity functions of coil arrays is a crucial element in parallel magnetic resonance imaging (pMRI). The self-calibrating technique for sensitivity extraction has complemented the common calibration technique that uses a separate pre-scan. In order to improve the accuracy of sensitivity estimate from small number of self-calibrating data, which is extracted from a fully sampled central region of a variable-density k-space acquisition in self-calibrating parallel images, a novel scheme for estimating the sensitivity profiles is proposed in the paper. On consideration of truncation error and measurement errors in self-calibrating data, the issue of calculating sensitivity would be formulated as a regularized least squares estimation problem, which is solved by the preconditioned conjugate gradients algorithm. When applying the estimated coil sensitivity to reconstruct full field-of-view(FOV) image from the under-sampling simulated and in vivo data, the normalized signal-to-noise ratio (NSNR) of reconstruction image is evidently improved, and meanwhile the normalized mean squared error (NMSE) is remarkably reduced, especially when a rather large accelerate factor is used.

Contrast-enhanced whole-heart coronary magnetic resonance angiography at 3 T with radial EPI

Whole-heart coronary magnetic resonance angiography is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (typically 10-15 min). The goal of this study was to implement a radial echo planar imaging sequence for contrast-enhanced whole-heart coronary magnetic resonance angiography, with the aim of combining the scan efficiency of echo planar imaging with the motion insensitivity of radial k-space sampling. A self-calibrating phase correction technique was used to correct for off-resonance effects, trajectory measurement was used to correct for k-space trajectory errors, and variable density sampling was used in the partition direction to reduce streaking artifacts. Seven healthy volunteers and two patients were scanned with the proposed radial echo planar imaging sequence, and the images were compared with a traditional gradient echo and X-ray angiography techniques, respectively. Whole-heart images with the radial EPI technique were acquired with a resolution of 1.0 × 1.0 × 2.0 mm(3) in a scan time of 5 min. In healthy volunteers, the average image quality scores and visualized vessel lengths of the RCA and LAD were similar for the radial EPI and gradient echo techniques (P value > 0.05 for all). Anecdotal patient studies showed excellent agreement of the radial EPI technique with X-ray angiography.

Determination of the Metallic/Semiconducting Ratio in Bulk Single-Wall Carbon Nanotube Samples by Cobalt Porphyrin Probe Electron Paramagnetic Resonance Spectroscopy

A simple and quantitative, self-calibrating spectroscopic technique for the determination of the ratio of metallic to semiconducting single-wall carbon nanotubes (SWCNTs) in a bulk sample is presented. The technique is based on the measurement of the electron paramagnetic resonance (EPR) spectrum of the SWCNT sample to which cobalt(II)octaethylporphyrin (CoOEP) probe molecules have been added. This yields signals from both CoOEP molecules on metallic and on semiconducting tubes, which are easily distinguished and accurately characterized in this work. By applying this technique to a variety of SWCNT samples produced by different synthesis methods, it is shown that these signals for metallic and semiconducting tubes are independent of other factors such as tube length, defect density, and diameter, allowing the intensities of both signals for arbitrary samples to be retrieved by a straightforward least-squares regression. The technique is self-calibrating in that the EPR intensity can be directly related to the number of spins (number of CoOEP probe molecules), and as the adsorption of the CoOEP molecules is itself found to be unbiased toward metallic or semiconducting tubes, the measured intensities can be directly related to the mass percentage of metallic and semiconducting tubes in the bulk SWCNT sample. With the use of this method it was found that for some samples the metallic/semiconducting ratios strongly differed from the usual 1:2 ratio.

Shot Noise Thermometry for Thermal Characterization of Templated Carbon Nanotubes

A carbon nanotube (CNT) thermometer that operates on the principles of electrical shot noise is reported. Shot noise thermometry is a self-calibrating measurement technique that relates statistical fluctuations in dc current across a device to temperature. A structure consisting of vertical, top, and bottom-contacted single-walled carbon nanotubes in a porous anodic alumina template was fabricated and used to measure shot noise. Frequencies between 60 and 100 kHz were observed to preclude significant influence from Vf noise, which does not contain thermally relevant information. Because isothermal models do not accurately reproduce the observed noise trends, a self-heating shot noise model has been developed and applied to experimental data to determine the thermal resistance of a CNT device consisting of an array of vertical single-walled CNTs supported in a porous anodic alumina template. The thermal surface resistance at the nanotube-dielectric interface is found to be 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> K/W, which is consistent with measurements by other techniques.

An 8-Bit 600-MSps Flash ADC Using Interpolating and Background Self-Calibrating Techniques

This paper describes a flash ADC using interpolation (IP) and cyclic background self-calibrating techniques. The proposed IP technique that is cascade of capacitor IP and gate IP with dynamic double-tail latched comparator reduces non-linearity, power consumption, and occupied area. The cyclic background self-calibrating technique periodically suppresses offset mismatch voltages caused by static fluctuation and dynamic fluctuation due to temperature and supply voltage changes. The ADC has been fabricated in 90-nm 1P10M CMOS technology. Experimental results show that the ADC achieves SNDR of 6.07bits without calibration and 6.74bits with calibration up to 500MHz input signal at sampling rate of 600MSps. It dissipates 98.5mW on 1.2-V supply. FoM is 1.54pJ/conv.

Joint image reconstruction and sensitivity estimation in SENSE (JSENSE)

Parallel magnetic resonance imaging (pMRI) using multichannel receiver coils has emerged as an effective tool to reduce imaging time in various applications. However, the issue of accurate estimation of coil sensitivities has not been fully addressed, which limits the level of speed enhancement achievable with the technology. The self-calibrating (SC) technique for sensitivity extraction has been well accepted, especially for dynamic imaging, and complements the common calibration technique that uses a separate scan. However, the existing method to extract the sensitivity information from the SC data is not accurate enough when the number of data is small, and thus erroneous sensitivities affect the reconstruction quality when they are directly applied to the reconstruction equation. This paper considers this problem of error propagation in the sequential procedure of sensitivity estimation followed by image reconstruction in existing methods, such as sensitivity encoding (SENSE) and simultaneous acquisition of spatial harmonics (SMASH), and reformulates the image reconstruction problem as a joint estimation of the coil sensitivities and the desired image, which is solved by an iterative optimization algorithm. The proposed method was tested on various data sets. The results from a set of in vivo data are shown to demonstrate the effectiveness of the proposed method, especially when a rather large net acceleration factor is used.

Inverse analysis of ultrasonic signals of ceramics based on ultrasonic self-compensating technique

An ultrasonic self-calibrating technique for the characterization of a ceramic which was fabricated by change pressing time during the HIP process has been applied by using the ratio of the reflection and transmission coefficients of normal incidence longitudinal waves. The ratio of ultrasound by the transducer and the condition of the couplant. The insensitive direction in parameter space is defined as the direction in which the variation of the ratio to changes of two parameters vanishes. For inverse problem the distribution of minima in an error surface is investigated.

Improved direct measurement of the parity-violation parameter Ab using a mass tag and momentum-weighted track charge.

We present an improved direct measurement of the parity-violation parameter A(b) in the Z boson-b-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z-->bb events via the topological reconstruction of the B hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of A(b) to be made independently of other Z-pole coupling parameters. From the 1996-1998 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A(b)=0.906+/-0.022(stat)+/-0.023(syst).

A simple self-calibrating cold cloud duration technique applied in West Africa and Bangladesh

Two satellite-based rainfall estimation routines (RI1 and RI2) have been applied in two different climatic environments: the semi-arid to sub-humid conditions of the Senegal River basin in West Africa and the humid conditions of Bangladesh. Both routines are based on bi-hourly thermal infra-red data from METEOSAT satellites. The RI1 and RI2 models are both variants of Cold Cloud Duration (CCD) techniques and employ two parameters for rainfall estimation: a rain rate and a rain threshold temperature, where the latter is used to identify rain areas. The RI1 model, like ordinary CCD algorithms, assumes an equal amount of rain falls from all clouds colder than the temperature threshold, whereas the RI2 model assumes that clouds precipitate more with decreasing temperatures. Continuous calibration of rain rates and temperature thresholds is suggested to capture short term variations in rain cloud properties. Results are compared to a well-established CCD routine, the GOES Precipitation Index (GPI) that uses constant values of rain rate and temperature threshold. Tests of RI1. RI2 and GPI shows that neither RI1 nor RI2 produces better results than the GPI in Bangladesh, while in the Senegal River basin the continuously calibrated RI1 model performs best.

Intercomparison of ozone profiles measurements by a differential absorption lidar system and satellite instruments at Buenos Aires, Argentina

A ground-based DIfferential Absorption Lidar (DIAL) system has been implemented at CEILAP (CITEFA-CONICET) laboratory (34°33′S, 58°30′W), located in the Buenos Aires industrial suburbs. The goal is to perform measurements of the stratospheric ozone layer. Systematic measurements of ozone concentration profiles from ∼18 to ∼35 km altitude are performed since early 1999. Our measurements are carried out in 5 h in average during the night and in cloudless conditions. The DIAL system allows us to calculate directly the ozone profile from the lidar backscattering radiation since it is a self-calibrating technique. The signal processing takes into account the influence of the temperature profile on the ozone cross section. The temperature data are obtained from the radiosondes measurements performed at Ezeiza International Airport (34°30′S, 58°18′W), 27 km from DIAL station. The evolution of the stratospheric ozone profile is studied for different months. Results are compared with the data obtained by different satellites SAGE II, HALOE and GOME. The comparisons between our DIAL system and the satellite measurements show an agreement better than 20% for 20–35 km altitude range.

레이저 유도 초음파 및 자기보상 기법을 이용한 재료의 표면균열 깊이 비파괴 평가

It is required to evaluate nondestructively the crack depth of surface-breaking cracks for the assurance of safety of structure. Optical generation of ultrasound produces well defined pulses with a repeatable frequency content, that are free of any mechanical resonances; they are broad band and are ideal for the measurement of attenuation and scattering over a wide frequency range. Self-calibrating surface signal transmission measurement is very sensitive and practical tool for surface-breaking crack depth. In this paper, the self-calibrating technique by laser-based ultrasound is used to evaluate the depth of surface-breaking crack of material. It is suggested that the relationship between the signal transmission and crack depth can be used as a practical model for predicting the surface-breaking crack depths from the signal transmission measured in structure.