For the improvement of monitoring accuracy, a vibration monitoring for aircraft wing model using a fiber Bragg grating (FBG) array packaged by vacuum-assisted resin transfer molding (VARTM) is proposed. The working principle of the vibration monitoring using FBG array has been explained, which can theoretically support the idea of this paper. VARTM has been explained in detail, which is suitable for not only the single FBG sensor but also the FBG array within a relatively large area. The calibration experiment has been performed using the FBG sensor packaged by VARTM. The strain sensitivity of the VARTM package is 1.35 pm/μϵ and the linearity is 0.9999. The vibration monitoring experiment has been carried out using FBG array packaged by VARTM. The measured rate of strain changes across the aluminum test board used to simulate the aircraft wing is 0.69 μϵ/mm and the linearity is 0.9931. The damping ratio is 0.16, which could be further used for system performance evaluation. Experimental results demonstrate that the vibration monitoring using FBG sensors packaged by VARTM can be efficiently used for the structural health monitoring. Given the validation and great performance, this method is quite promising for in-flight monitoring and holds great reference value in other similar engineering structures.
Gold nanorod has generated great research interests due to its tunable surface plasmon resonance (SPR). The mechanism of the SPR effect on the enhancements of optical performance for the volume holographic polymer is investigated. The resonance wavelength is dependent on the aspect ratio of the nanorod. Theoretical model for the localized surface plasmon resonance effect are developed and simulated for the interactions between the photopolymer components and nanorods in the gold nanorod doped volume holographic photopolymer. The experimental evaluation of the material suggests a novel candidate for potential applications in high-density optical data storage and high-resolution holographic display.
A metallic packaging technique of fiber Bragg grating (FBG) sensors is developed for measurement of strain and temperature, and it can be simply achieved via one-step ultrasonic welding. The average strain transfer rate of the metal-packaged sensor is theoretically evaluated by a proposed model aiming at surface-bonded metallic packaging FBG. According to analytical results, the metallic packaging shows higher average strain transfer rate compared with traditional adhesive packaging under the same packaging conditions. Strain tests are performed on an elaborate uniform strength beam for both tensile and compressive strains; strain sensitivities of approximately 1.16 and 1.30 pm/μϵ are obtained for the tensile and compressive situations, respectively. Temperature rising and cooling tests are also executed from 50°C to 200°C, and the sensitivity of temperature is 36.59 pm/°C. All the measurements of strain and temperature exhibit good linearity and stability. These results demonstrate that the metal-packaged sensors can be successfully fabricated by one-step welding technique and provide great promise for long-term and high-precision structural health monitoring.
A new relative orientation w local parameter optimization method of the essential matrix for the large scale close range photogrammetry is presented in this paper to improve the accuracy and stability of the measurement system. For the matched images, according to the closed-loop polynomial algorithm, the essential matrix is initialized, and an iterative algorithm based on local parameter optimization is proposed. Then the relative exterior orientation parameters are solved from the essential matrix, and only one correct solution is determined by the Cheirality constraints. The orientation experiment of the expandable truss microwave antenna profile measurement is carried out to verify the accuracy and reliability of the new method. Compared with the traditional methods, this new method has minimum projection error and the least iterations, and it will play a key role in the performance improvement of the whole system.
The research showed the simulation of position error when assembling a reflective mirror of parabolic trough concentrator. The shape of a reflective mirror is like a parabolic cylinder model, relying on the back of the four-point mounted on a special setup, making it unable to move. Therefore, it is of great importance of the machining precision of special bracket. We need to analyze the influence of reflective mirror‘s intercept factor in order to guide the processing precision. It is assumed that each reflective mirror is rigid, we have calculated the intercept factor of reflector with mounting points’ random error of different standard deviation, comparing the simulating results with TRACEPRO. As a sequence, we can approve the feasibility of the algorithm, and give the effect of different random errors on the light-gathering efficiency. On the basis, we provide the machining accuracy of bracket. The simulation results show that when the mounting points’ standard deviation of position error is less than 0.5 mm, the intercept factor of receiver has reached upwards of 92% with 60 mm diameter for receiver, which can satisfy the design requirements.
This paper proposes a new method which is called variable weighted centroid method for locating the center of retro reflective target. It is based on centroid method. This method adapts itself to different measurement environments by varying the weight coefficients α, which is determined by different factors associated with measuring environment. The coefficient α is optimized by experiment. The evaluation criterion (lower is better) under the proposed method is reduced by at least 25% compared with the traditional method. Experiment results show that this variable weighted centroid method provides higher locating accuracy than old methods.
Determination of image point coordinates has a strong influence on the accuracy of photogrammetry. It will be helpful if we could choose a kind of locating method with highest accuracy in specific environment. As it is difficult to measure the image point location accuracy directly, researchers generally acquire this accuracy by simulation which may deviate greatly from real environment. This paper proposes a more practical method - to evaluate the accuracy of image point center location from practical scenario based on linear fitting. This method promises to evaluate a higher accuracy in the image space via a lower accuracy in the object space through projection rules. In this paper we perform an experiment with retro-reflective targets (RRT), a coordinate measuring machine (CMM) and a CCD camera. The target locations are centroid, squared centroid and ellipse fitted center. Their accuracy, in descending order, is: squared centroid, centroid, and ellipse fitted center.
An all fiber Q-switched Ytterbium-Doped Fiber （YDF） laser in Master Oscillator Power-Amplifier (MOPA) configuration is proposed theoretically and demonstrated experimentally, and the principle analysis and experimental verification are presented in details. Firstly, the system configuration is designed. The system is composed of the seed and the amplifier stage. Two 915nm LDs are used for pumping light, and the light is coupled into the gain medium of the seed and the amplifier stage by two combiners, respectively. Two Fiber Bragg Gratings (FBGs) are used as ends of the cavity of the seed. One Q-switch is used to modulate output laser of the seed, and the amplifier stage is adopted to amplify the light behind the seed. Then, 10m YDF with single mode is selected for the gain medium of the seed, and 8m YDF with multimode is used as the gain medium of the amplifier stage. The output laser of the seed with a 1.02W average power is realized when the seed pump power is 5.74W, the repetition rate is 20KHz and the action time of the Q-switch is 3.5μs. Meanwhile, a 7.58W pump power of the amplifier stage is used to amplify the seed laser. Finally, output laser with the pulse width of 90ns and the average output power of 4.93W are achieved.
It would be very challenging for a designer to select desirable structure parameters for a laser triangulation probe, the parameters which have an appreciable or noticeable impact on probe’s measuring range, resolution and accuracy. The challenge is aggravated by the trade-offs between the measuring range and resolution since there is interdependency and a delicate balance among them. Therefore, this paper focuses on building the relationship between the measuring range and resolution, and tries to optimize the structure parameters to improve measuring accuracy within a certain measuring range. In order to verify the validity and feasibility of this method, single-triangulation probe simulation experiments are also performed in 3dsmax platform. In addition, a double-triangulation probe simulation system is proposed and the experimental results confirm that the slope error can be compensated effectively. The conclusions presented in this paper provide useful guidance for designing a high-precision triangulation probe.
The precision of centroid location for infrared LED point images is an important factor, which affects the precision of the light-pen Coordinate Measuring Machining (CMM) .In this paper, the error model using the traditional center of mass (COM) algorithm is analyzed and it is shown that there are systematic error and random error. This paper analyzes the systematic error and random error, and then adopts the Gaussian surface fitting (GSF) algorithm and weighted centre-ofgravity (WCOG) algorithm to compensate systematic errors, meanwhile it analyzes how to reduce random error. The simulation results show that the accuracy of the infrared LED point position can be enhanced from 1/ 20 pixel to 1/100 pixel using the new algorithm.
Digital shearography has demonstrated great potential in direct strain measurement and, thus, has become an industrial tool for nondestructive testing (NDT), especially for NDT of delaminations and detection of impact damage in composite materials such as carbon fiber reinforced plastics and honeycomb structures. The increasing demand for high measurement sensitivity has led to the need for real-time monitoring of a digital shearographic phase map. Phase maps can be generated by applying a temporal, or spatial, phase shift technique. The temporal phase shift technique is simpler and more reliable for industry applications and, thus, has widely been utilized in practical shearographic inspection systems. This paper presents a review of the temporal phase shift digital shearography method with different algorithms and the possibility for real-time monitoring of phase maps for NDT. Quantitative and real-time monitoring of full-field strain information, using different algorithms, is presented. The potentials and limitations for each algorithm are discussed and demonstrated through examples of shearographic testing.
A photoelectric autocollimator employing an area Charge Coupled Device (CCD) as its target receiver, which is specially used in numerical stage calibration is optimized, and the various error factors are analyzed. By using the ZEMAX software, the image qualities are optimized to ensure the spherical and coma aberrations of the collimating system are less than 0.27mm and 0.035mm respectively; the Root Mean Square (RMS) radius is close to 6.45 microns, which is identified with the resolution of the CCD, and the Modulation Transfer Function (MTF) is greater than 0.3 in the full field of view, 0.5 in the centre field at the corresponding frequency. The errors origin mainly from fabrication and alignment, which are all about 0.4" . The error synthesis shows that the instrument can meet the demands of the design accuracy, which is also consistent with the experiment.
The study of hemorheology is becoming the hot spot of medical research and biomedical engineering. A high
performance full-automatic capillary blood rheological measurement system which is based on the principle of the
Hagen-Poiseuille law is introduced in this paper. The system integrates the computer control technology and the
precision measurement technology. The slave module of the system hardware and software are designed by the module
idea. The application program in the computer achieves man-machine interaction and the lower computer controls the
slave module of the system. The experimental results demonstrate that the repeatability error of the system is 1.309% and
the quoted error of the system is 0.021%.
In close range photogrammetry and vision metrology, several images which are taken at different stations are required
for high accuracy. Before camera calibration and 3D reconstruction, the targets in the images must be recognized and
located with high accuracy firstly. Furthermore, in order to monitor the deformation of the surface, real-time and on-line
photogrammetry system is needed, in which high speed is necessary. So, the image processing method and speed will
affect the accuracy and speed of the photogrammetry system. This paper describes a fast target location method for the
photogrammetry system. Experimental results show that the target edge pixels preserve the important geometric
information for subpixel centroid, which can reach accuracies to 2-3% of the pixel size. The process time of an image
with 3008x2000 pixels is about 0.1S, much higher than other similar methods.
In digital photogrammetry and computer vision, for high accuracy, several images obtained from the different positions are required. The targets in the images are recognized and matched by the computer automatically. This paper present a new method based on the bundle adjustment for the targets matching. It transforms the problem solving space from the 2D images into the 3D world space. With a few targets matched manually, the projection lights can be reconstructed with the interior and exterior parameters provided by the bundle adjustment. More targets are matched based on the correlations of the reconstructed lights. With the new matched targets, the bundle adjustment runs again and the parameters are revised. Repeat these steps until all targets are matched. Experimental results are shown to testify its feasibility and validity. In the experiments, the matching rate of the new method can reach 100%, while the missing rate is very low.
The coded target design is geometrically constructed only of circular elements, i.e. circular marked point, circular reference point and circular coding points. Marked point is surrounded by a reference point and some coding points with bit position at equally spaced angular interval. The circular radius of the reference point is bigger than that of coding points. Marked point represents the point location itself. Reference point provides a start bit for coding points. Coding points provide robust identification of the target anti-clockwise, starting from reference point. The design method provides a sufficient number of identification points by introducing a reference point. Finally, the application of the proposed coded targets to 3D data registration is described. Experimental results show that the developed coded targets are independent to location, rotation and change of scale, and the marked points are easily and accurately detected.
Proc. SPIE. 7130, Fourth International Symposium on Precision Mechanical Measurements
KEYWORDS: Error analysis, Data modeling, Teeth, Information science, Information technology, Precision measurement, Fluctuations and noise, Lutetium, Current controlled current source, Spherical lenses
Helicoidal surfaces are very useful in many aspects, their error assessment has become more and more important. In this
paper, studied the method of the error assessment, and the key point was focused on how much number of measuring
points to be enough. Firstly, the current methods of the error assessment were analyzed. Then, the study was spread out
from general equation of the helicoidal surfaces to general model of the error and the error assessment, and pointed out
the number of the measuring points could be determined with the variations of the means and the variances of the errors.
Finally, took a worm as an example to explain that the method is feasible.
A method of distortion correction based on parallel lines is presented, not only for radial distortion coefficient but also for tangential distortion coefficients. Firstly, an approximate line passing through the center is approached by anamorphic curves. The coefficient of distortion is combined with the vision process to correct an anamorphic image for the final calibration of the liner model. Secondly, the point with only tangential distortion is gained by the actual point minus radial distortion. The distances from the point with tangential distortion and the ideal point to the principal point are equivalent. The Least-squares method is used to fit lines in theory, and the coefficients of tangential distortion are gotten.
In order to get good accuracy, designer used to consider how to place cameras. Usually, cameras placement design is a
multidimensional optimal problem, so people used genetic algorithms to solve it. But genetic algorithms could result in
premature or convergent problem. Sometime we get local minimum and observe vibrating phenomenon. Those will get
inaccurate design. So we try to solve the problem using the changing environment genetic algorithms. The work
proposes giving those species groups difference environment during difference stage to improve the property. Computer
simulation result shows the acceleration in convergent speed and ability of selecting good individual. This work would
be used in other application.
This work proposes an algorithm to measure the smoothness of three-dimensional object. Firstly use computer vision
technology to reconstruct the three-dimensional surface. Then construct high order vanishing moment wavelet to analyze
the data. In order to detect the discontinuous derivative points, this paper proposes an algorithm based on wavelet
transform. Wavelet is used to descript surface smoothness and detect abnormal data. When using different vanishing
moment wavelets to deal with data, we would get different value at those points with different smoothness value. That
surface with same smoothness would become a plane. Meanwhile, in order to improve the algorithm validity, this paper
proposes using Daubechies wavelet. This algorithm resolved our project problem. It can be used in other projects that
require the surface with good smoothness.
In order to test the rheological property of biological fluid more simply and more accurately test, a cone plate speed
attenuation method is put forward on the base of spinning cone plate method. The cone plate is firstly driven by an eddy
coil to a preset value. Then the cone plate attenuates freely under the action of a fluid viscosity force. In the system,
standard viscosity oil is applied to calibrate measurement parameters and thus to eliminate systematic errors. The system
employs an upper computer and a lower microprocessor and adopts broadcast communication in a master/slave manner
based on RS485 serial links. The microprocessor is a LPC2131 for measuring the angular speed and the angular
acceleration of the cone plate and for controlling sampling and cleaning. The upper computer is programmed with the
language of Visual c++ 6.0, for data processing, data storage and data displaying. The repeatability error of the system, in
which the measurement is conducted with a standard non-Newtonian fluid, is 0.57%.
In order to accurately position the nodes of a SAR(synthetic aperture radar), a special assemble workbench is designed
and a laser tracker named LTS-1100 from the API is used to measure it. The two stations layout of laser tracker along the
lengthways center line of the workbench are adopted. The six common points used when the laser tracker moving from
one station to the other are selected based on the stability experiment under the working environment. The laser tracker
measures the positions of all the points real time and directs their adjustments. The distance error of the points from the
ideal on the workbench is less than ±0.105mm. The close range photogrammetric method is then used to measure the
nodes position of the SAR antenna assembled on the workbench. The result indicates the coincidence with that obtained
by the laser tracker.
Absorbency measurement is the most important step in the ELISA analysis. Based on the spectrophotometry,
absorbency photometer system used in a fully automatic ELISA analyzer is developed. The system is one core
module of the fully automatic ELISA analyzer. The principle and function of the system is analyzed. Three main units
of the system, the photoelectric transform unit, the data processing unit and the communication and control unit, are designed and
debugged. Finally, the test of the system is carried out using the verification plate. The experiment results agree well
with the requirements.
This paper introduces the principle and configuration of an auto urine analysis system. The system employs an
ARM-LPC2214 as CPU and a color linear-CCD as sensor. A CPLD is used to produce pulses for the CCD and for
other circuits in the system. The CPLD is programmed through Verilog HDL language. The sick is determined
according to the color change of test strips. Principle of color test circuit and design of software for identifying
color data are also described. The software uses the principle of CIE Colorimetry to identify the color. Experiments
show that test speed is fast and the result is precise. This system is suitable for the situations in which a large
number of samples are to be treated.
This paper introduces the scheme of a control system for a fully automatic ELISA (Enzyme-linked Immunosorbent
Assay) tester. This tester is designed to realize the movement and positioning of the robotic arms and the pipettors and to
complete the functions of pumping, reading, washing, incubating and so on. It is based on a MSP430 flash chip, a 16-bit
MCU manufactured by TI Co, with very low power consumption and powerful functions. This chip is adopted in all
devices of the workstation to run the controlling program, to store involved parameters and data, and to drive stepper
motors. To the MCUs, motors, sensors, valves and fans are extended. A personal computer (PC) is employed to
communicate with the instrument through an interface board. Relevant hardware circuits are provided. Two programs,
one running in PC performs users' operation about assay options and results, the other running in MCU initiates the
system and waits for commands to drive the mechanisms, are developed. Through various examinations, this control
system is proved to be reliable, efficient and flexible.
The measurement of helicoidal surfaces is very important for the manufacture and utilization of fine mechanical parts. It
usually employs the feature line error to represent the helicoidal surfaces' error. Two methods, commonly used to assess
the character line error, least-square method and accumulative sum method, are analyzed and compared here by
combining with practical data processing.
The measurement of helical surfaces is used not only to evaluate the precision of the surfaces, but also to analyze the sources of its deviation from the specification. In this article, many aspects of helical surfaces are contained, as the mathematical principle of forming the surface, the measuring equipment, the measuring methods and our research status. First the forming principle of the helical surface is given and the classification methods by the mathematical equations are shown. Then the equipment is summarized, and the classification and the working principles of the measurement of the helical surface is given. At third we introduce our research status, and also give a measurement example of a hobbing cutter and a concise analysis. From the analysis we derive a method to improve the quality of the helical surface. Finally, we discuss the future development of the measurement of the helical surface.
In order to enhance the precision of videogrammetry for the profile of large-scale antenna, multi-station network is
necessary, which will also affect the reliability, efficiency and stability of the results. In this paper, the impacts of normal
and convergent configurations on the precision of space targets are discussed. Constraints, including image scale, depth
of field, field of view, and distribution of image points, which affect the network configurations, must be taken into
account. Specific network configurations for the large-scale gossamer inflatable antenna are designed and experimental
data results verify the conclusions.
In this paper we propose a uniform mathematic model of helicoidal surfaces. We describe the spacing surface and the properties of helicoidal surfaces. We studie the description of real surfaces and on this basis, we derive the deviations from helicoidal surfaces and its uniform model. We provide an algorithm for the compensation of the stylus radius. This research is useful to unify the measurement of all kinds of helicoidal parts and to simplify the measuring procedures.
A point matching method in photogrammetry for microwave antenna with non-metric cameras is presented. The method with coded points and epipolar constrain is described. To solve the point matching in large measurement range, the idea of the dividing area is presented. The circular coded points as identifiers are used to identify different subareas, and subarea matching is preformed. Then, the measured points are matched with epipolar constraint in each subarea of left and right images. In order to reduce the influence of lens distortion to epipolar constraint, a control points grid as frame of reference is used to correct all image points using a distortion model. Experimental result indicates that this method is valid and reliable to reduce data processing time, and to improve image matching veracity and automatic degree. The points matching ratio is 100%. This method has provided one excellent solution for point matching problem in large object photogrammetry with non-metric cameras.
Recent progress of images taken by non-metric digital cameras encourages amateurs to utilize it for 3D measurements, but also introduces the difficulties of calibration. The ideal camera projection model is based on the pinhole linear model which proceeds on the assumption that the object point, the perspective center of the lens and the ideal image point all lie on a straight line. However, real camera lenses introduce nonlinear distortions that affect the accuracy of the transformation unless proper corrections are applied. In this paper, we present a new camera calibration method adopting a linear projection model and a nonlinear lens distortion model. Experiments are conducted on real data to compare the proposed method with the non-linear bundle adjustment and DLT (Direct Linear Translation), which shows that the accuracy obtained with the proposed method is close to the former, and much higher than the latter.
A digital close range photogrammetric method for space deployable microwave antenna is presented. The planning of multi-camera stations, 3D data connection of images of different view field and the calibration of the cameras are discussed. The procedure of calibration has two steps: direct linear transformation and the bundle adjustment. The measurement error resulted from lens distortion can be corrected. The relative accuracy of 1 part in 1000 can be achieved using on site automatic calibration during measurement. The profile of the space deployable microwave antenna was obtained through the least squares fitting of the adjusted observations.