High-precision Real-time Measurement Research Articles

Structural simulation and performance evaluation of self-priming electrostatic diesel vehicle emission particle sensor

Here is reported a self-priming electrostatic particulate matter (PM) sensor for real-time monitoring of diesel exhaust under different operating conditions. Initially, a multi-physics coupling model for the sensor was established. By varying the exhaust flow and temperature, the emissions of diesel vehicles were simulated to evaluate the sensor. The results showed that within the typical velocities (5 to 60 m/s) and temperature ranges (100 to 500 °C) of diesel exhaust, the sensor outlet pressure was consistently below the inlet pressure, with a maximum differential pressure of 259 Pa, indicating the capability for self-priming sampling of exhaust under different operating conditions. Additionally, the calibration platform was constructed using a miniature inverted soot generator which produced a series of samples to calibrate the relationship between current and mass concentration with a correlation coefficient of 0.99. From 0 to 100 mg/m3, the PM sensor exhibited a relative error between −6.00% and 6.00% with good stability and consistency for samples of different sizes and concentrations, with correlation coefficients exceeding 0.98. The results between the self-developed sensor and a commercial instrument revealed that the former provided high-precision real-time measurement of diesel exhaust.

Automatic fabrication system of optical micro-nanofiber based on deep learning

<sec>The wide range, high precision, and dynamic real-time measurement of micro-/nanofiber diameter are crucial for achieving low loss transmission and controlling dispersion in the preparation process of micro-nanofiber. In view of the problems of small diameter regulation range, complex operation and long-time consumption of the existing preparation methods, the automatic detection system of micro-nanofiber is realized based on deep learning neural network algorithm in this work. The image segmentation method in computer vision is used to make high-quality multi-scale micro-/nanofiber datasets, and the improved YOLOv8-FD (You Only Look Once version 8-Fiber Detection) algorithm based on small target detection is used to automatically detect the diameter of micro-nanofiber.</sec><sec>Through image segmentation and identification of the target of single pixel size in the microscopic image, the diameter detection of micro-nanofiber is finally realized. In this process, the real-time diameter of micro-nanofiber is obtained through image information, and then the micro-nanofiber small target is accurately segmented to achieve the precise detection of mAP<sup>IoU</sup><sup>=50</sup> = 0.975 and mAP<sup>IoU</sup><sup>=50—95</sup> = 0.765 on the micro-nanofiber multi-scale target dataset with extremely high accuracy. The algorithm-based construction of a high-precision micro-nanofiber automatic preparation system enables real-time accurate segmentation of fiber edges, calculation of fiber diameter, and feedback to the control system for achieving automated preparation of fibers with arbitrary diameters. Additionally, it facilitates the detection of micro-nanofiber in a range from 462 nm to 125 μm. The average response time for reasoning is 9.6 ms, and the detection error is kept below 2.95%.</sec><sec>In addition, compared with other micro-/nanofiber diameter detection methods based on optical imaging and mode cutoff, this method shows advantages of high precision, high speed and arbitrary diameter preparation for diameter detection based on deep learning neural networks. The system is very suitable for high-precision real-time measurement and automatic and accurate preparation of micro-/nanofibers, thereby providing a novel method of developing micro-nanofiber devices with low-loss transmission and adjustable dispersion. </sec>

Ultra high precision in-vacuum long trace profiler for real time slope determination of optical surface

The development of an in-vacuum long trace profiler (IVLTP) which can provide ultra high precision real time measurements on the surface slope of optical elements is reported. The unique features of this instrument include a specifically designed ultra high repeatability linear slide, a pentamirror composed of two plane mirrors of ultra low slope error, and an ultra high vacuum (UHV) compatible complementary metal oxide semiconductor (CMOS) image sensor. The mechanical system is made of Invar 36 alloy to reduce the room temperature drift effect during data acquisitions. Each IVLTP scan completes in 120 seconds, covering a 168 mm of surface length and generating more than 5000 slope data points. The root mean square (RMS) of the difference between two consecutive scans was found to be 0.0081 μrad on average and 0.0045 μrad RMS at its best. The main application of this IVLTP is to provide the real time feedback signals needed for controlling the 25-actuator surface benders of the active mirrors and active gratings installed in the ultra high resolution soft X-ray beamlines at the Taiwan Photon Source (TPS).

Space-to-plane decoupling method for six-degree-of-freedom motion measurements

The advantages of the Stewart platform in bearing capacity, dynamic response, structural rigidity, and stability make it widely used in many fields, such as motion simulators, parallel machine tools, assembly docking. In order to ensure that the spatial positioning accuracy of the Stewart platform to meet the application requirements in various fields, it is necessary to measure its pose in real time. However, the six degrees of freedom are highly coupled, it is difficult to obtain reliable six-degree-of-freedom information through mathematical decoupling. In this study, a machine vision measurement method based on physical decoupling is proposed. The spatial motion measurement of the Stewart platform is mapped to the plane motion measurement by three feature points through the laser pointer and the rear-projection screen. It realizes the dimension reduction equivalently, and simplifies the mathematical model. A lot of experimental analyses show that the proposed method can reliably achieve high-precision real-time measurement of six-degree-of-freedom, which has the accuracy of 0.21 mm (displacement) and 0.045° (rotation) at frequency between 0.1 and 1 Hz. In addition, the space-to-plane decoupling method provides a new way to implement the traceability of the six-degree-of-freedom spatial motion measurement.

Visual measurement system for three dimensional rotation attitudes of the air float turntable

A visual method for 3D attitude measurement of air float turntable based on space vector is proposed. By installing a laser pointer on the surface of the air float turntable, the projection line and the reference plane generate intersection points (light spots) to construct feature points, and use a high-speed camera to achieve the spot’s displacement at different times, the three-dimensional attitude of the air float turntable can be calculated at any time. The turntable’s rotation attitudes are measured by projection method, and the measurement baseline is increased to avoid the adverse influence on the measurement result caused by the nearer feature points distance. A global calibration of the world coordinates for the measurement model is performed to construct an attitudes measurement system. The experimental results show that the measurement system does not affect the functions of other systems on the air float turntable. Adopt 2 mm step calibration in the 2 m × 4 m field of view, the spots’ positioning accuracy is better than 0.09 mm. The maximum standard error of the centroid extraction is 0.0095 pixels, the field of view range is up to ±15°, the yaw angle error is better than ±1.2′, the pitch angle is better than ±1.8′, and the roll angle error is better than 0.42′. The attitude’s information can be transmitted in real time via UDP communication. The results show that the wide-field attitude angle visual measurement system is designed reasonably and can meet high-precision real-time measurement requirements.

Calibration of Large-Scale Spatial Positioning Systems Based on Photoelectric Scanning Angle Measurements and Spatial Resection in Conjunction with an External Receiver Array

Positioning systems providing high-precision real-time measurements over very large spatial scales are urgently required for large-scale industrial manufacturing applications. While large-scale positioning systems (LSPSs) employing laser transmitter stations have been employed in engineering practice, the introduction of an LSPS into an existing industrial manufacturing setting must first solve the problems of docking with existing control points and external parameter calibration. However, calibrating the external parameters of a measurement system is very difficult under extreme and complicated working conditions due to the limited visibility of transmitter stations and the measurement distances involved. This problem is addressed in this paper by proposing a single transmitter station calibration method based on a photoelectric scanning multi-angle resection positioning model that combines photoelectric scanning angle measurements and spatial resection in conjunction with an external receiver array. Positioning information is obtained by solving the unknown parameters of the model according to a nonlinear optimization approach using the Levenberg–Marquardt least-squares fitting algorithm. The feasibility and spatial positioning accuracy of the proposed method are verified experimentally. The experimental results demonstrate that the principles of the proposed method are correct, and the method can achieve millimeter measurement accuracy, which meets the requirements of measurement tasks in engineering applications.

Grid Deformation Real-Time Measurement System of Ion Thruster Based on Videometrics

In order to conduct high-precision measurement of the LIPS-300 ion thruster grid deformation in a vacuum, high-temperature, and plasma environment, a noncontact videometrics system using a telemicroscope was designed. Based on the captured image, the interactive partitioning edge detection method (IPEDM) was used to obtain stable and clear edges of multiple circular cooperative targets. Meanwhile, magnification factor calibration, rotation angle correction, and subpixel-level grid deformation measurement were performed with cooperative targets. The measurement results show that under the power of 750 W in the discharge chamber, the maximum thermal deformation of the screen grid is 1120 μm, and the gap between the screen grid and the accelerator grid is reduced by 420 μm. An accuracy assessment of the system shows that the grid deformation measurement accuracy is better than 12 μm, and the system satisfies the requirement of high-precision real-time measurements of the grid thermal deformation of the ion thruster under the discharge-chamber-running condition and the plasma-beam-extraction condition.

Low-Cost Highly Sensitive Refractive Index Measurement Based on Deep Frequency Modulation Interferometry

A novel low-cost technique for refractive index (RI) measurement is proposed and experimentally demonstrated based on the concept of deep frequency modulation (DFM). By omitting electro-optic modulator from conventional DFM, the frequency modulation is realized by direct current modulation of a laser diode which leads to cost reduction. The flicker noise effect on the DFM performance, which is considered as a major obstacle of homodyne detection, has been considered in our numerical analysis; hence, a realistic analysis of the results is presented. Hereby, a modification in the DFM signal processing has been suggested to mitigate the flicker noise effect. Through proper selection of higher harmonics of the wideband detected DFM signal, the normalized error can be reduced more than 10 dB. We have implemented this method for a Michelson interferometer to measure RI of an aqueous solution. An interference signal is formed on the photodetector, which is then processed to measure RI by estimating the optical path length difference between the two interferometer arms. It is shown that this setup provides a resolution of better than $2.1 \times {10^{-5}}$ in RI unit. The proposed cost-effective measurement technique can be readily integrated in applications, where high precision real-time measurements over a wide measurement range are required.

Research on high-precision hole measurement based on robot vision method

A high-precision vision detection and measurement system using mobile robot is established for the industry field detection of motorcycle frame hole and its diameter measurement. The robot path planning method is researched, and the non-contact measurement method with high precision based on visual digital image edge extraction and hole spatial circle fitting is presented. The Canny operator is used to extract the edge of captured image, the Lagrange interpolation algorithm is utilized to determine the missing image edge points and calculate the centroid, and the least squares fitting method is adopted to fit the image edge points. Experimental results show that the system can be used for the high-precision real-time measurement of hole on motorcycle frame. The absolute standard deviation of the proposed method is 0.026 7 mm. The proposed method can not only improve the measurement speed and precision, but also reduce the measurement error.

A Novel Three Coding-pitches Triangular Patterns Phase-shifting Profilometry based on Modified Sunzi Theorem

In order to realize the high precision real-time measurement for the static objects, three coding-pitches triangular patterns phase-shifting profilometry based on modified Sunzi Theorem (ST) was proposed in this paper. First, according to Sunzi Theorem, the triangular pattern is designed. This Sunzi Theorem was adopted to unwrap three wrapped coordinate acquired from triangular patterns fringe images. The greatest common divisor of codingpitches is obtained by the used projector. In unwrapping processing, the wrapped coordinate is considered as remainder of the absolute coordinate modulo of the coding-pitch. Generally there are two kinds of rounding policies for the remainder in real number set. If the rounding policy selection is wrong, the rounding result of remainder containing decimal fraction error which can lead the unwrapping result to quite away from the correct one. In order to solve the high sensitivity of the decimal fraction error, the decimal fraction difference is recognized as the criterion of the rounding policy selection for real number erroneous remainder. To verify the presented method in this paper, a 3D shape measurement experimental system is constructed using projector and camera. The experiment results shown that, a maximum standard deviation of measurement error to the rule 3D objects is 0.62mm, and the complex surface reconstruction with different surface reflectivity can be realized very well.