On-line Measurement Method Research Articles

Research on the method of vision online distance measurement of laser holes in solar base cell

To address the low efficiency of the current off-line laser hole distance method for solar cells (SC), an on-line distance measurement method of laser holes based on image processing is proposed. First, a forward irradiation imaging method with surface light is provided for the SC images. A line detection method of SC edge fitting is proposed and then the sub-pixel coordinates of feature points are obtained according to the laser point extraction algorithm based on the local area, and the distance between the laser hole and edge is calculated. Finally, the precise distance is obtained according to calibrated results between the pixel and millimetre. The experimental results show that this method can accurately measure the laser distances of SC holes, and is more accurate than the existing sub-pixel corner detection algorithm, which verifies the feasibility and accuracy of this method.

Cross section measurement of neutron capture reaction based on back-streaming white neutron source at China spallation neutron source

The data of neutron capture cross section are very important for the research of nuclear astrophysics, advanced nuclear energy development. Owing to the limitation of neutron source and detector, the experimental data of neutron capture cross section in an energy range of 1 eV–10 keV were almost blank in China. The first Chinese gamma-ray total absorption facility has been constructed in the key laboratory of nuclear data at China institute of atomic energy, which consists of 40 BaF<sub>2</sub> detector units. The BaF<sub>2</sub> crystal shell with a thickness of 15 cm and an inner radius of 10 cm covers 95.2% of the solid angle. On-line measurement method of neutron capture reaction cross section is established on the back-streaming white neutron source of China spallation neutron source by using the upgraded facility. The cross section of <sup>197</sup>Au neutron capture reaction is measured for the first time under the experimental condition of irregular 30 mm neutron beam spot. The measured position of resonance peak is well consistent with the relevant data of ENDF evaluation database, which verifies the reliability of the measurement device and measurement technology, and thus laying the foundation for the acquisition of high precision cross section in future.

On-line monitoring of mine tunnel deformation using laser radar

Mine tunnel deformation blocks underground coal mine traffic, or even cause serious security incidents. Aiming at the problem of lack of monitoring method of tunnel deformation, this paper presents a method of tunnel deformation measurement based on laser-radar technology. The measurement method is a non-contact and on-line measurement method. The system is mainly composed of two parts, the host part is composed of computer, ZigBee module and processing software system based on Processing, the slave part is composed of four-rotor craft, STM32 microprocessor, laser radar, ZigBee wireless communication module and power supply module. The new tunnel deformation measurement method based on radar proposed in this paper has the advantage of smaller measurement data error, the data communication and processing speed is qualified and suitable for on-line monitoring.

On-line measurement method of transmission backlash based on angular velocity and double-end angular position information

Backlash is the inherent characteristic of gear transmission system. It is an important mean to measure and compensate backlash to improve transmission performance. When the driving gear reverses, due to the existence of backlash, the driven gear will still keep its original steering due to inertial motion until the driven gear collision with the driving gear. In this paper, based on the analysis of the tooth gap of the driving gear and the driven gear, an on-line measurement method of the meshing tooth gap combining the angular velocity of the load end with the information of the Angle position of the two axes of the master-slave gear is presented. This method uses the gyroscope at the load end (driven wheel) to monitor the sudden change of angular velocity at the moment of gear reverse impact and re contact, and the signal is used as the judgment basis for the reverse contact moment of the driving gear and driven gear. Then, the angular position data of driving gear and driven gear are fused at the time of reverse rotation and contact impact, and the backlash of the gear is calculated online. Finally, setting up an experimental platform for measuring backlash, and the proposed method is verified. The experimental results show that the proposed method can achieve accurate backlash measurement.

An on-line measurement method of injection rate of high pressure common rail system

This paper presents a new on-line measurement method of injection rate based on the injector inlet pressure. The Riemann wave theory is applied to the fuel system, and the mathematical relationship of injection rate (G) and pressure (P) under single Riemann wave is put forward. The correction algorithm of the interference wave and the decoupling method of the superposition wave are proposed, which improves the accuracy of the algorithm and realizes the calculation of the fuel injection rate during the long injection energizing time. The identification algorithm of the needle maximum upstroke position moment and the needle starting downstroke moment are proposed and taken as the key time characteristics of the injection process. Compared to the experiments, the errors of the injection mass by this method were within 3%, and the fitting goodness of injection rate curve exceeded 0.93, proving quite good precision for the method.

A high-accuracy non-contact online measurement method of the rotor-stator axial gap based on the microwave heterodyne structure

Rotor-stator axial gap is a key design parameter that affects the efficiency and safety of large rotating machines. An optimal axial gap value should be determined so that the rotating machines could work at the highest efficiency. To realize active clearance control (ACC) of rotating machines, high-accuracy non-contact online measurement of the axial gap must be carried out. However, direct current (DC) offset signals in absolute distance measurement, limited working space of sensors, and extremely harsh working environment all pose challenges to the realization of high-accuracy, non-contact, and online performance required by the axial gap measurement. Therefore, no mature measurement method exists at present. In this paper a rotor-stator axial gap measurement method was proposed based on the phase difference ranging principle. The structure of microwave heterodyne could effectively eliminate the errors caused by DC noise during absolute distance measurement. To break through the bottleneck of axial gap measurement accuracy, an axial gap measurement error model was established, and a signal carrier frequency error processing method along with a phase measurement error processing method based on spatial distance scanning were proposed. A platform modeled on the rotating machines’ structure of edge labyrinth gas seal was built in the laboratory to carry out room temperature rotor-stator axial gap measurement. A prototype of the axial gap measurement based on a microstrip type sensor was developed, and the system’s calibration and measurement performance evaluation experiments were carried out. Experimental results verified the effectiveness and accuracy of the proposed method. The measurement accuracy is better than 30 μm (at 0.5–3 mm) and better than 1% (at 3–18.5 mm).

Online measurement of dissolved carbon monoxide concentrations reveals critical operating conditions in gas fermentation experiments

Syngas fermentation is one possible contributor to the reduction of greenhouse gas emissions. The conversion of industrial waste gas streams containing CO or H2 , which are usually combusted, directly reduces the emission of CO2 into the atmosphere. Additionally, other carbon-containing waste streams can be gasified, making them accessible for microbial conversion into platform chemicals. However, there is still a lack of detailed process understanding, as online monitoring of dissolved gas concentrations is currently not possible. Several studies have demonstrated growth inhibition of Clostridium ljungdahlii at high CO concentrations in the headspace. However, growth is not inhibited by the CO concentration in the headspace, but by the dissolved carbon monoxide tension (DCOT). The DCOT depends on the CO concentration in the headspace, CO transfer rate, and biomass concentration. Hence, the measurement of the DCOT is a superior method to investigate the toxic effects of CO on microbial fermentation. Since CO is a component of syngas, a detailed understanding is crucial. In this study, a newly developed measurement setup is presented that allows sterile online measurement of the DCOT. In an abiotic experiment, the functionality of the measurement principle was demonstrated for various CO concentrations in the gas supply (0%-40%) and various agitation rates (300-1100 min-1 ). In continuous stirred tank reactor fermentation experiments, the measurement showed reliable results. The production of ethanol and 2,3-butanediol increased with increasing DCOT. Moreover, a critical DCOT was identified, leading to the inhibition of the culture. Thus, the reported online measurement method is beneficial for process understanding. In future processes, it can be used for closed-loop fermentation control.

In-Process Monitoring of Changing Dynamics of a Thin-Walled Component During Milling Operation by Ball Shooter Excitation

During the milling of thin-walled workpieces, the natural frequencies might change radically due to the material removal. To avoid resonant spindle speeds and chatter vibration, a precise knowledge of the instantaneous modal parameters is necessary. Many different numerical methods exist to predict the changes; however, small unmodelled effects can lead to unreliable results. The natural frequencies could be measured by human experts based on modal analysis for an often interrupted process; however, this method is not acceptable during production. We propose an online measurement method with an automatic ball shooter device which can excite a wide frequency range of the flexible workpiece. The method is presented for the case of blade profile machining. The change of the natural frequencies is predicted based on analytical models and finite element simulations. The measurement response for the impulse excitation of the ball shooter device is compared to the results of impulse modal tests performed with a micro hammer. It is shown that the ball shooter is capable of determining even the slight variation of the natural frequencies during the machining process and of distinguishing the slight change caused by different clamping methods. An improved FE model is proposed to include the contact stiffness of the fixture.

On-Line Measurement Method for Diameter and Roundness Error of Balls

This paper presents an on-line measurement method for the diameter and roundness error of balls. An easy-installation rotary scanning system, which integrates the principles of the diameter and the roundness measurements, is constructed. The rotary scanning system consists of a rotary stage, a linear stage, and two sensors with a flat probe. Two sensors are initially installed on the linear stage and contact each other. The outputs of two sensors are reset to zero at first. The ball is then mounted on the rotary stage and positioned between two flat probes. The variations of the diameter and the roundness error of the ball at each angular position can be directly recorded by two sensors when the ball is rotated by the rotary stage. Substituting the outputs of two sensors into the proposed mathematical models, the diameter and roundness error can be evaluated. The effects of the alignment error induced by the spindle error of the rotary stage and the titling error and the eccentric error of the ball on the measurement accuracy can be self-separated in the proposed on-line measurement method. A series of experiments are carried out to verify the effectiveness and the capability of the proposed on-line measurement method and the designed rotary scanning system. The designed system is easy to construct both in the laboratory environment and the factory field.

Characterization of lysozyme PEGylation products using polarized excitation-emission matrix spectroscopy.

The growing use of therapeutic proteins requires accurate analytical techniques for measuring biophysical and structural changes during manufacturing. This is particularly true for the PEGylation of proteins, because characterization of PEGylation reactions and products can often be difficult due to the relatively small impact on protein structure, the lack of an accessible polyethylene glycol (PEG) chromophore, and the heterogeneous final product mixtures. Intrinsic fluorescence spectroscopy is one potential solution due to its relatively high sensitivity to small changes in protein structure and its suitability for online or atline measurements. In this study, we use the PEGylation of lysozyme as a model system to determine the efficacy of polarized excitation-emission matrix (pEEM) spectroscopy as a rapid tool for characterizing the structural variability of the lysozyme (LZ) starting materials and PEGylated products with varying PEG-to-protein ratios (PPR). Dynamic light scattering showed that as PPR increased from 0 to 2.8, the hydrodynamic radius increased from ∼2.2 to 4.8 nm. pEEM measurements provided several sources of information: Rayleigh scattering to identify size changes and aggregate/particle formation, and fluorescence emission to assess chemical and structural changes. PEGylation induced sufficient physicochemical changes in LZ, which produced changes in the pEEM spectra, largely due to variations in the hydrophobic environments of tryptophan residues close to a PEG attachment site. These significant spectral changes when modeled using conventional multivariate analysis methods were able to easily discriminate the raw product solutions according to the degree of PEGylation and were also able to predict PPR with reasonable accuracy (root mean square error for calibration ∼10%, relative error of prediction < 20%), considering the reference size exclusion chromatography method error of ∼7.2%. The variable selection of the pEEM data suggests that equivalent predictions could be obtained with faster and simpler two-dimensional spectra, making the method a more viable online measurement method.

Small Anechoic Chamber Design Method for On-Line and On-Site Passive Intermodulation Measurement

A design method is proposed in this article for on-line (online measurement: measurement when producing devices) and on-site (on-site measurement: measurement when using devices) passive intermodulation (PIM) measurement with a small-size anechoic chamber. In a PIM measurement, the role of an anechoic chamber is to shield extraneous electromagnetic signal and reduce reflection, so that an accurate measurement result can be obtained. However, the chamber itself may introduce new PIM sources due to the nonlinearity in absorbing material and shielding enclosure. The traditional method to lower the influence of chamber to PIM measurement is to design a large-size PIM test chamber in order to reduce the PIM level by path loss. In this article, an innovative design concept of the PIM test chamber is presented by controlling the PIM source level of the anechoic chamber instead of increasing the size of the chamber. It can significantly reduce the chamber size using this method, particularly suitable for on-line and on-site PIM measurement. To implement the concept, absorbing material and shielding enclosure structure with extremely low PIM are developed. The design concept includes defining the worst-case reflection level, estimating the PIM level due to reflected signals, and determining the smallest size of the chamber that meets the design specifications. Finally, two PIM test chambers are built to demonstrate the design concept. PIM measurement results are given to verify the theoretical analysis.

Contactless moisture content measurement on green veneer based on laser light scattering patterns

The wood structure anisotropy and moisture content variation within the volume create different patterns of light scattering inside the wood. The objective of this study was to assess the suitability of a laser method for online measurement of green veneer moisture content based on the so-called tracheid effect. Beech and poplar veneers with thicknesses of 1, 2 and 3 mm were subsequently laser scanned and weighed to obtain various humidities. The results show that the measured laser scattering profile, such as the major axis, minor axis and ellipse area on the veneer surface, increases with moisture. The laser scattering profile provides a reliable and precise prediction of the moisture content. Out of the three ellipse parameters evaluated, the ellipse area provides the best prediction of the moisture content of the green veneer for both beech and poplar.

Response of thermal diffusion to gas–liquid stratified/wave flow and its application in measurement

This paper presents an online and non-contact measurement method for gas–liquid stratified/wave flow. A horizontal steel pipe installed with several wall temperature sensors and two ring-like heaters was used as meter. When the gas–liquid flow flowed through the pipe, the heat was transferred from the wall to the fluid, and the temperature distribution and fluctuation on the wall were measured by sensors. A thermal diffusion model was established to explain the relationships between temperature distribution/fluctuation and gas–liquid flow. Flow velocity and gas–liquid phase interface locations were calculated according to the axial and circumferential temperature distribution, respectively. This novel measurement method was experimentally verified using air–water flow. The average measurement errors were 6%/7% and 14% for the phase interface locations of stratified/wave flow and flow rate with maximum values of 9%/14% and 30%, respectively.

Temporal release behavior of potassium during pyrolysis and gasification of sawdust particles

The potassium release from sawdust in pyrolysis and gasification was studied using an online measurement method. The final results suggested that the potassium releases more in pyrolysis than that in CO2 gasification environment at 800-900 °C. The overall activation energies and pre-exponential factors of potassium release in pyrolysis and gasification were further derived. In addition, the additive chlorine influence on potassium release had been evaluated, and the results showed that the promoting effect of chlorine during pyrolysis was higher than the case during CO2 gasification. Thermodynamic calculations were done to predict the possible potassium species during pyrolysis and gasification. The K2CO3 (s) formation mostly contributed to the higher potassium release proportion in pyrolysis than that during CO2 gasification.

Novel Methods for Modeling and Online Measurement of Effective Bulk Modulus of Flowing Oil

Oil is a key medium for transmitting power and coupling information in the hydraulic transmission system. Accurate calculation and measurement of the dynamic compressibility of the oil have profound significance to the system performance analysis. The present study primarily focuses on the effect of steady pressure on the bulk modulus of static oil. However, changing pressure and flowing oil are the general working conditions in most of hydraulic apparatus. There are few researchers paying attention to the influence of pressure on the compressibility of flowing oil. Considering the log-normal distribution of bubble size in oil, an improved static oil model (Model B) is developed to calculate the bulk modulus of the motionless oil under the dynamic pressure. Then, by deriving Model B, this paper proposes an original flowing oil model (Model C) to determine the effective bulk modulus of flowing oil. Finally, based on the inherent pressure pulsation of the axial piston pump, an innovative online method for measurement of the bulk modulus of flowing oil is presented as it has the advantage of avoiding interference with flow stability. It has been proved that the changes in the flow velocity corresponds to the crucial effect on the effective bulk modulus of flowing oil, especially under the low-flow and low-pressure operation conditions. Those results and analysis provide promoting support for identifying and determining the effective bulk modulus of oil, analyzing the system stiffness, improving the control accuracy, as well as optimizing the mathematical models.

Design and Experiment of Dynamic Measurement Method for Bulk Material of Large Volume Belt Conveyor Based on Laser Triangulation Method

In order to improve the measurement accuracy and efficiency of bulk material transported by large-capacity belt conveyor, an online dynamic non-contact metering system based on laser triangulation is designed on the belt conveyor platform. The system includes: laser Scanners, industrial camera, signal processing software, mechanical assemblies. High-precision basic measurement data is an important guarantee for the accuracy of bulk flow measurement. The laser scanner is used as a line source, and the scanning frequency is set to 300HZ, which is installed on the belt conveyor. Industrial camera accepts images produced by a line source projected onto the bulk surface. The signal processing software system analyzes the images, and uses the triangulation method directly calculate the three-dimensional contour information and volume flow of the bulk material. The flow filtering algorithm filters the instantaneous flow, smoothing the fluctuation of the flow data to reflect the real changes of the dry and wet degree of the bulk material on the belt, the degrees of surface cracking and shapes. Establish a mathematical model based on neural network and apply the belt shaking elimination algorithm to correct the previously calculated flow data to reduce the measurement error. In order to restore the actual belt conveyor bulk transportation conditions, a test belt with length 20m and speed 2m/s was produced according to the actual size. The physical simulation test of bulk material for potassium salt was carried out, the results show that the on-line measurement method based on laser triangular method has high efficiency and stable operation, and eliminates the influence of bulk density. The measurement error is ≤3.

基于Bragg光栅的电力电缆温度在线测量方法研究

基于Bragg光栅的电力电缆温度在线测量方法研究

Online measurement of CO2 and total gas production in parallel anaerobic shake flask cultivations

Online measurements of off-gas streams are often crucial for studying bioconversion processes. However, for anaerobic processes, options for online off-gas analysis are typically restricted to lab-scale bioreactors or larger systems, while gas measurements at smaller scales typically do not discriminate between different gases. In this work, a method for online measurement of CO2 and total gas production in anaerobic fermentations at the shake flask scale is described, extending capabilities of a previously reported device developed for aerobic processes to anaerobic bioprocesses. The novel design allows anaerobic fermentations to be performed in multiple parallel vessels, all of which collect online gas signals. The online gas signals are used to calculate the transfer rates, allowing near real-time visualization of the progress of eight fermentations operating in parallel. Conditions such as carbon source depletion, inhibition of growth, and exhaustion of a single carbon source in a dual-substrate fermentation can all be clearly distinguished. The combination of online signals and offline analysis allowed for carbon balances to be performed with high degrees of closure. The new design allows for higher throughput screening of anaerobic bioprocesses, an area lacking in small-scale options with off-gas analysis capabilities.

On-line micro-vibration measurement method for Lorentz-type magnetic-bearing space actuators

A novel, cost-effective, real-time and on-line method for measuring the generated micro-vibrations and identifying the forces in a magnetic bearing space actuator is proposed. For its validation, an actively-controlled electrodynamic (Lorentz-type) magnetic bearing reaction wheel (MBRW) demonstrator is used, where the magnetic bearing coils’ current is used as a measurable magnitude to identify the exertion of forces to the satellite’s structure. Due to the Lorentz-type magnetic bearing, a linear relation between current and force is considered and a validation campaign is undertaken, taking a micro-vibration test set-up as a reference. The results obtained using the proposed method are comparable, to a sub-newton level, to the micro-vibration amplitude measured using a state-of-the-art piezoelectric-based dynamometric equipment, which is usually employed for reaction wheel on-ground qualification. The proposed method does not rely on any external and costly measurement equipment, as it only employs internal sensors, already required for control purposes in any active magnetic bearing (AMB), and it can be used for control or on-line and in-situ monitoring purposes.

Online Frequency Response Measurements of Grid-Connected Systems in Presence of Grid Harmonics and Unbalance

Grid characteristics have a drastic impact on the stability and control performance of grid-connected systems. Because the grid conditions typically vary over time, online measurements are most desirable for the stability assessment, protection design, and control system optimization of the systems. Previous studies have presented methods based on Fourier techniques and broadband sequences, with which the frequency responses of the grid-connected systems, such as the grid impedance or inverter control loops, can be measured. However, online measurements under unbalanced grids with harmonic voltages have not been comprehensively considered. This letter demonstrates how the previously applied online measurement methods fail in the presence of unbalanced grid and voltage harmonics due to the spectral leakage caused by the Fourier transform. This letter also proposes a simple signal design method to avoid the leakage. Experimental results based on a high-power grid-connected system are shown to demonstrate the effectiveness of the proposed method.