Real-time Online Measurement Research Articles

Optical fiber evanescent-wave sensing technology of hydrogen sulfide gas concentration in oil and gas fields

For the problems of light source fluctuation noises, zero drift and other problems of H2S gas concentration sensor in optic-fiber evanescent-wave absorption spectroscopy, double-light-path absorption system was designed to theoretically analyze the relationship between evanescent-wave power and gas concentration as well as detection sensitivity. Moreover, the relationship between evanescent-wave power and optical-fiber residual diameter in the optic fiber corrosion process was also studied. The sensing probes with different evanescent-wave power ratios were used to detect experiments of H2S gas concentration. The experimental results show that the sensitivity is up to 0.169μw/ppm when the evanescent-wave power ratio of sensing probe is 10%, detected minimum H2S gas concentration is 5.1ppm, the detection repeatability is good and the response time is only 2.03s. Due to low production cost, high sensitivity and short response time, the optic-fiber evanescent-wave sensor can be used for real-time on-line measurement of H2S gas in the area of the hydrocarbon exploration and development.

Single-Perturbation-Cycle Online Battery Impedance Spectrum Measurement Method With Closed-Loop Control of Power Converter

This paper presents a method for an online real-time electrochemical impedance spectroscopy (EIS) measurement of batteries using closed-loop control of power converter. Unlike the previously proposed method which allows the measurement of the ac impedance for a single frequency, the presented method in this paper allows for obtaining the EIS for a spectrum of frequencies by using the information included in a single perturbation cycle, or a few cycles of perturbation to obtain a more accurate EIS with a very wide frequency range. This will result in faster EIS measurement for a spectrum of frequencies and under the same battery operating conditions. The presented method utilizes closed-loop control operation for the EIS measurement functionality, which allows for better control of the output voltage and for upgrading the concept to be able to achieve no added perturbation ripple at the output of the system. The presented online real-time EIS measurement method utilizes a power converter with closed-loop control in order to create an output voltage step-function perturbation at a given frequency to generate battery voltage and current responses. By applying Fourier analysis to these responses, an EIS can be obtained for a range of frequencies equal or higher than the perturbation frequency of the step function. In addition, this paper presents a method to eliminate the added perturbation ripple when two or more power converters are used. The theoretical basis and experimental prototype results are provided to illustrate and validate the presented method.

Graphene oxide-polymethylmethacrylate polymer waveguide device based on near infrared fingerprint spectrum for refractive index sensing

A graphene oxide-polymethylmethacrylate (GO-PMMA) microfiber sensor is proposed and experimentally demonstrated in this paper, which is based on the absorption principle of near infrared spectra for external refractive index sensing. The sensor was fabricated by splicing a section of 1 mm GO-PMMA between two tapered single mode fibers. The hydrophilic groups of graphene oxide can be used to measure the proportion of water in glycerol solution, and achieve the goal of refractive index measurement indirectly. Experiments were conducted for moisture content of 4.3%~45% (refractive index range from 1.3400 to 1.4054) in glycerin solution. Different concentrations of glycerol solution have different intensities of absorption peaks near 1530 nm wavelength. The absorption peak power near 1530 nm wavelength responses to the external refractive index was experimentally studied. The results show that the sensor possesses a high sensitivity of 167.39 dB/RIU in the refractive index range of 1.34~1.41 and has a good linearity response to external refractive index. The proposed sensor is attractive owing to its high measurement speed, accurate, no pollution and lower cost, and is suited for long-term online real-time measurement.

An improved measurement model of binocular vision using geometrical approximation

In order to improve the precision of a binocular vision measurement system, an effective binocular vision measurement method, named geometrical approximation, is proposed. This method can optimize the measurement results by geometrical approximation operation based on the principles of optimization theory and spatial geometry. To evaluate the properties of the proposed method, both simulative and practical experiments are carried out. The influence of image noise and focal length error on measurement results is discussed. The results show that measurement performance of the proposed method is manifested well. Besides, the proposed method is also compared with Bundle adjustment and least squares method in a practical experiment. The experiment results indicate that the average error, calculated by using the proposed method, is 0.076 mm less than Bundle adjustment’s 0.085 mm, and only half of the least squares method’s 0.146 mm. At the meantime, the proposed method enjoys a high level of computational efficiency when compared to Bundle adjustment. Since no nonlinear iteration optimization is involved, this method can be applied readily to real time on-line measurements.

Gas holdup estimation using Maxwell equation in flotation systems: Revisited

Estimation of gas holdup from electrical conductivity measurements has been used in lab and industrial installations. The approach is based on the application of Maxwell’s model, which relates the concentration of a dispersed phase in a continuous medium to measurements of the electrical conductivity of the dispersed phase, continuous medium and the resulting mixture (dispersion). When applied to inferring the collection zone gas holdup in a three phase system and to facilitate real-time on-line measurement, the slurry is assumed to behave as the continuous medium and gas bubbles as a non-conducting dispersed phase. This article derives an equation for estimating gas holdup in a three phase system, eliminating the assumption that the slurry behaves as a continuous medium but rather as a dispersion of non-conducting solid particles in water. In this formulation only water behaves as the continuous medium in the sense of Maxwell, and gas holdup in a three phase system is then calculated from the application of the Maxwell model twice: (1) to determine solid content in a two-phase system, and (2) to determine solid plus gas holdup in a three phase system. To validate the new equation and quantify the errors incurred by assuming slurry is the continuous phase a laboratory flotation cell was instrumented to continuously measure the conductivity of two and three phase dispersions with known solids contents. As the amount of gas in a lab flotation machine is difficult to measure directly or by another indirect technique such as using pressure signals, 2.5mm dielectric plastic spheres having a density of ca. 1.3g/cm3 were used instead of air bubbles for validation. Experimental results demonstrated that the continuous medium assumption underestimates gas holdup and that the resulting bias error increases linearly with the solid content and decreases with the magnitude of gas holdup.

High Precision Optical Sensors for Real-Time On-line Measurement of Straightness and Angular Errors for Smart Manufacturing

A setup of two reflective-type optical sensors for the on-line real-time measurement of straightness and angular errors of a linear stage is presented. The arrangement is similar to that of a linear encoder and can make on-line measurements of stage errors for the analysis of automatic processes as well as real time monitoring. The reflector used as the sensor reference plane was a rectangular piece of commercial silicon wafer. The wafer fixed to the side of the slide was very flat and had good reflective properties. A silicon wafer is much cheaper than a long optically flat mirror of similar precision. The standard deviation of the straightness sensor and the angular error were verified as 0.06 μm and 0.08 arcsec. The accuracy of the two sensors was verified as ±0.25 μm and ±1 arcsec. The two sensors were integrated with a single axis PZT-based stage for real time straightness compensation experiments and the results showed straightness compensation from 3.5 μm down to 0.4 μm.

Point cloud simplification algorithm based on particle swarm optimization for online measurement of stored bulk grain

The simplification of 3D laser scanning point cloud is an important step of surface reconstruction and volume estimation of bulk grain in granary. This study presented an adaptive simplification algorithm based on particle swarm optimization (PSO). It introduced PSO into the average distance method, a conventional simplification method. The basic idea of this algorithm was to adaptively determine the optimal point reducing intervals of scanning lines according to original point cloud density by PSO. By using the 3D point cloud scanned from bulk grain surface in granary, the proposed algorithm was validated. Compared with the average distance method, the proposed algorithm obtained more evenly distributed point set, smaller reduction ratio (6.96%) and higher volume estimation accuracy (relative error was less than 3‰). The 3D laser scanner (GSLS003, Jilin University and SkyViTech Co., Ltd., Hangzhou, China) used in this study could scan the complete picture of the grain surface in a granary in one time, so the acquired point cloud data do not have to be jointed. For the good simplification performance and capability of updating the reducing interval at any moment, the proposed algorithm and the 3D laser scanner could be used to realize online real-time measurement of stored bulk grain volume in granary. Keywords: point cloud, simplification algorithm, particle swarm optimization (PSO), 3D laser scanning, large object, stored grain DOI: 10.3965/j.ijabe.20160901.1805 Citation: Shao Q, Xu T, Yoshino T, Zhao Y, Yang W, Zhu H. Point cloud simplification algorithm based on particle swarm optimization for online measurement of stored bulk grain. Int J Agric & Biol Eng, 2016; 9(1): 71－78.

Welding deviation detection algorithm based on extremum of molten pool image contour

The welding deviation detection is the basis of robotic tracking welding, but the on-line real-time measurement of welding deviation is still not well solved by the existing methods. There is plenty of information in the gas metal arc welding(GMAW) molten pool images that is very important for the control of welding seam tracking. The physical meaning for the curvature extremum of molten pool contour is revealed by researching the molten pool images, that is, the deviation information points of welding wire center and the molten tip center are the maxima and the local maxima of the contour curvature, and the horizontal welding deviation is the position difference of these two extremum points. A new method of weld deviation detection is presented, including the process of preprocessing molten pool images, extracting and segmenting the contours, obtaining the contour extremum points, and calculating the welding deviation, etc. Extracting the contours is the premise, segmenting the contour lines is the foundation, and obtaining the contour extremum points is the key. The contour images can be extracted with the method of discrete dyadic wavelet transform, which is divided into two sub contours including welding wire and molten tip separately. The curvature value of each point of the two sub contour lines is calculated based on the approximate curvature formula of multi-points for plane curve, and the two points of the curvature extremum are the characteristics needed for the welding deviation calculation. The results of the tests and analyses show that the maximum error of the obtained on-line welding deviation is 2 pixels(0.16 mm), and the algorithm is stable enough to meet the requirements of the pipeline in real-time control at a speed of less than 500 mm/min. The method can be applied to the on-line automatic welding deviation detection.

Online Correction of the Dynamic Errors in a Stored Overpressure Measurement System

The problem encountered in sharp shock testing as a result of inadequate bandwidth must be addressed to obtain an accurate overpressure peak value when measuring the steep signals of shockwaves during explosions. A dynamic compensator can effectively amend the dynamic errors caused by sensor system characteristics; thus, a dynamic compensation method based on improved particle swarm optimization (PSO) algorithm is proposed in this paper. This method can effectively overcome the influence of the initial value derived with PSO algorithm on compensator index. The distributed algorithm is introduced into the hardware structure design of the dynamic compensator to facilitate the application of an optimized compensator to real-time online measurement. This integration realizes the high-speed parallel of the dynamic compensator of the sensor with field-programmable gate array. Experimental results show that a high-speed parallel dynamic compensator can amend the dynamic errors in a sensor accurately and in a timely manner.

Applying Structured Light on Cylinder Straightness Detection Using Break Line Method

Generally after a cylindrical steel bar is made from hot forming process, its contour will look like ‘U’ or ‘wavy’ topography. The preformed steel bar after steelmaking process needs to remove the outside oxide layer by lathe or peeling machine (commonly known as stripping). As a consequence, the deformation of steel bar will cause subsequent problems, such as eccentric rotating of steel bar as the lathe is running. Although it is necessary to remove the oxide layer, the deformation will increase waste materials. To prevent the problems, a straightening machine is usually used to straighten the cylindrical steel bar before the pickling process. However, most current straightening machines cannot measure cylindrical steel bar contour on-line instantly. This study proposed a test method for measure the contour of a large cylindrical steel bar based on multi-line structured light and machine vision. Break line method were performed to measure the contour of the cylindrical steel bar. The experimental result shows that the measurement error is in the range of ±0.4 mm after calibration. The study result concludes that the proposed method can be applied to straightening machine for real-time online measurement to improve straightening efficiency.

Image-based monitoring for early detection of fouling in crystallisation processes

Fouling or encrustation is a significant problem in continuous crystallisation processes where crystal deposits at surfaces impede heat transfer, increase flow resistance and reduce product quality. This paper proposes an automatic algorithm to detect early stages of fouling using images of vessel surfaces from commodity cameras. Statistical analysis of the pixel intensity variation offers the ability to distinguish appearance of crystals in the bulk solution and on the crystalliser walls. This information is used to develop a fouling metric indicator and determine separately induction times for appearance of first crystals at the surfaces and in the bulk. A method to detect process state changes using Bayesian online change point detection is also proposed, where the first change point is used to determine induction time either at the surface or in the bulk, based on real-time online measurements without using any predetermined threshold which usually varies between experiments and depends on data acquisition equipment. This approach can be used for in situ monitoring of early signs of encrustation to allow early warning for corrective actions to be taken when operating continuous crystallisation processes.

分布式光纤温度压力传感器设计

In order to realize fully distributed measurement for temperature and pressure in an oil well,a measurement method of distributed temperature and pressure based on scattering theory of optical fiber is established. The method makes the common optical fiber into the sensing fiber through package design. Since the scattered light in the sensor fiber is modulated by the temperature and pressure of the fluid surrounding the optical fiber sensor,the real-time on-line measurement of the temperature and pressure is accomplished through the demodulation of the parameters of Raman scattering and Brillouin scattering frequency shift within the optical fiber by the optical fiber demodulator. Experimental results indicate that the distributed optical fiber sensor for temperature and pressure measurement can realize that the temperature resolution is 0. 1 ℃ and pressure resolution is 0. 07 MPa. It can satisfy the requirements of fully distributed,real-time,on-line,higherreliability,higher precision and strong anti-jamming for the measurement of temperature and pressure in an oil well.

KPCA-ESN Soft-Sensor Model of Polymerization Process Optimized by Biogeography-Based Optimization Algorithm

For solving the problem that the conversion rate of vinyl chloride monomer (VCM) is hard for real-time online measurement in the polyvinyl chloride (PVC) polymerization production process, a soft-sensor modeling method based on echo state network (ESN) is put forward. By analyzing PVC polymerization process ten secondary variables are selected as input variables of the soft-sensor model, and the kernel principal component analysis (KPCA) method is carried out on the data preprocessing of input variables, which reduces the dimensions of the high-dimensional data. Thek-means clustering method is used to divide data samples into several clusters as inputs of each submodel. Then for each submodel the biogeography-based optimization algorithm (BBOA) is used to optimize the structure parameters of the ESN to realize the nonlinear mapping between input and output variables of the soft-sensor model. Finally, the weighted summation of outputs of each submodel is selected as the final output. The simulation results show that the proposed soft-sensor model can significantly improve the prediction precision of conversion rate and conversion velocity in the process of PVC polymerization and can satisfy the real-time control requirement of the PVC polymerization process.

Electron microscopic study of soot particulate matter emissions from aircraft turbine engines.

The microscopic characteristics of soot particulate matter (PM) in gas turbine exhaust are critical for an accurate assessment of the potential impacts of the aviation industry on the environment and human health. The morphology and internal structure of soot particles emitted from a CFM 56-7B26/3 turbofan engine were analyzed in an electron microscopic study, down to the nanoscale, for ∼ 100%, ∼ 65%, and ∼ 7% static engine thrust as a proxy for takeoff, cruising, and taxiing, respectively. Sampling was performed directly on transmission electron microscopy (TEM) grids with a state-of-the-art sampling system designed for nonvolatile particulate matter. The electron microscopy results reveal that ∼ 100% thrust produces the highest amount of soot, the highest soot particle volume, and the largest and most crystalline primary soot particles with the lowest oxidative reactivity. The opposite is the case for soot produced during taxiing, where primary soot particles are smallest and most reactive and the soot amount and volume are lowest. The microscopic characteristics of cruising condition soot resemble the ones of the ∼ 100% thrust conditions, but they are more moderate. Real time online measurements of number and mass concentration show also a clear correlation with engine thrust level, comparable with the TEM study. The results of the present work, in particular the small size of primary soot particles present in the exhaust (modes of 24, 20, and 13 nm in diameter for ∼ 100%, ∼ 65% and ∼ 7% engine thrust, respectively) could be a concern for human health and the environment and merit further study. This work further emphasizes the significance of the detailed morphological characteristics of soot for assessing environmental impacts.

A NEW TYPE OF HIGH-POWER MICROWAVE IMPEDANCE TUNER BASED ON LOAD-PULL WITH A RAPID CALIBRATION METHOD

For the measurement of microwave device in high-power, traditional methods are inefficient, inaccurate and not on-line real-time measurement. A new type of high-power microwave impedance tuner (26. 5G Hz∼ 40 GHz) based on load-pull technique and a corresponding rapid calibration method based on curve fitting are proposed. A new structure using increased width rectangular waveguide slotted in the center is adopted as the main transmission line. In order to prevent the leak of electromagnetic waves transferring in rectangular waveguide, two choke grooves are added in upper cover plate of the waveguide cavity. The results (standing wave ratio range of 1.02 ∼ 10.98, insertion loss of 0.063 dB at minimum standing wave ratio) show by practical measurement that this structure and method are feasible. The device can meet the requirement of design, and the new method has less time for calibration.

Real-time online measurements of the inorganic and organic composition of haze fine particles with an Aerosol Chemical Speciation Monitor (ACSM)

以霾为代表的空气污染严重危害人体健康. 霾的形成与细颗粒物化学组分的变化密切相关. 本文详细报道了颗粒物化学组分监测仪(ACSM)在表征致霾细粒子化学组分，包括有机物、硫酸盐、硝酸盐、铵盐和氯化物，及其在快速估算大气一次和二次有机组分中的应用. 通过对2012年9月北京亚微米细颗粒物(PM 1 )的观测研究发现，北京秋季重霾污染天和清洁天的化学组分存在显著差异. 有机物是PM 1 的主要化学组分，在清洁天平均贡献PM 1 的约70%，而在重霾污染天，二次无机组分贡献量显著增加，超过50%. 利用有机气溶胶正矩阵因子分解(PMF)源解析结果，进一步建立了适用于北京秋季示踪质荷比 m / z 57 和 m / z 44 快速估算大气一次(HOA)和二次有机气溶胶(OOA)的关系式，即HOA = 26.6×( m / z 57 -0.02 × m / z 44)；OOA = 4.4 × m / z 44. PM 1 总质量浓度与细颗粒物总消光系数高度相关( r 2 = 0.91)，说明亚微米细颗粒物在霾的形成过程中起重要作用，其中消光系数与二次颗粒物的相关性远高于一次颗粒物，说明二次颗粒物化学组分的生成和转化在霾形成中起更为关键的作用.

Investigation of On-line Realtime Measurement of Automotive Exhaust Hazardous Air Pollutants by Proton Transfer Reaction Mass Spectrometry

Investigation of On-line Realtime Measurement of Automotive Exhaust Hazardous Air Pollutants by Proton Transfer Reaction Mass Spectrometry

Quantification of Intracellular Polyhydroxyalkanoates by Virtue of Personalized Flow Cytometry Protocol

Polyhydroxyalkanoates (PHAs) are natural polyesters produced by microbes, a potential alternative to synthetic plastics. Various methods ranging from gravimetry to spectrophotometry are routinely used for qualitative analysis of extracted PHA. There is a great need for accurate quantification of intracellular PHA during bioprocess. Hence, the present study aims to improvise the existing Nile red-based flow cytometry protocol. It was achieved using respective cells in a non-PHA accumulating state as gating control to minimize non-specific staining. The optimal Nile red concentration required for PHA staining is 5×10(3)pgmL(-1), which is ~10(3)-fold less than that of earlier reports. Further, it was inferred that flow-based quantification was more accurate than the gravimetric method. The intracellular PHA content was highest in Pseudomonas sp. MNNG-S (52.06%) among the Pseudomonas strains tested by the flow-based method. Both gravimetric and flow-based cell cycle analyses revealed that DNA synthesis (S phase) and PHA production (log phase) are synchronous at 24-48h of culture. This study supports flow-based PHA quantification for real time online measurement of intracellular PHA for bioreactor monitoring, control and optimization enduing industrial applications.

The 3D Measuring Method Based on the Color Coding Grating

This paper puts forward a new method of 3D measurement which based on the color coding structure light technology, projects the specific color coding grating to a Calibration board in RGB three color space, gets the straight line equation of grating which projected to Calibration board in the world coordinate system, obtains each projection plane of code through plane fitting, then joins the projection planes and the object imaging straight strips which through the camera focus, it can be get that the three dimensional coordinates of the objects. This method is simple and reliable; only need one camera and one projector without scanning; only one image is needed to get the information of a full frame depth image. It is suitable for high speed, real-time online measurement.

New Digital Method of Reverse Engineering about Free from Surface

In this paper, it is proposed a new method of free-from surface’s reverse engineering, making data acquisition and surface reconstruction form closed loop system, solving no feedback problems in the measuring and modeling process, shortening the time of the whole reverse engineering, improving the quality of reconstructed models. The core of this paper is used the CMM adaptive measuring method and non-uniform b-spline surface reconstruction method, integrating the free-from surface measuring and modeling in a closed loop system, realizing the CMM real-time online measurement and reconstructed surface real-time update.