scholarly journals X-ray Computed Tomography InstrumentPerformance Evaluation, Part I: Sensitivity to Detector Geometry Errors

2019 ◽  
Vol 124 ◽  
Author(s):  
Bala Muralikrishnan ◽  
Megan Shilling ◽  
Steve Phillips ◽  
Wei Ren ◽  
Vincent Lee ◽  
...  
Keyword(s):  
Single Point ◽  
Optimal Placement ◽  
Test Procedures ◽  
Error Sources ◽  
Form Errors ◽  
Sphere Center ◽  
Detector Geometry ◽  
Dimensional Measurements ◽  
Rotation Stage ◽  
Center Distance

X-ray computed tomography (XCT), long used in medical imaging and defect inspection, is now increasingly used for dimensional measurements of geometrical features in engineering components. With widespread use of XCT instruments, there is growing need for the development of standardized test procedures to verify manufacturer specifications and provide pathways to establish metrological traceability. As technical committees within the American Society of Mechanical Engineers (ASME) and the International Organization for Standardization (ISO) are developing documentary standards that include test procedures that are sensitive to all known error sources, we report on work exploring one set of error sources, instrument geometry errors, and their effect on dimensional measurements. In particular, we studied detector and rotation stage errors in cone-beam XCT instruments and determined their influence on sphere center-to-center distance errors and sphere form errors for spheres located in the tomographically reconstructed measurement volume. We developed a novel method, called the single-point ray tracing method, that allows for efficient determination of the sphere center-to-center distance error and sphere form error in the presence of each of the different geometry errors in an XCT instrument. In Part I of this work, we (1) describe the single-point ray tracing method, (2) discuss optimal placement of spheres so that sphere center-to-center distance errors and sphere form errors are sensitive to the different detector geometry errors, and (3) present data validating our method against the more conventional radiograph-based tomographic reconstruction method. In Part II of this work, we discuss optimal placement of spheres so that sphere center-to-center distance errors and sphere form errors are sensitive to error sources associated with the rotation stage. This work is in support of ongoing standards development activity within ASME and ISO for XCT performance evaluation.

scholarly journals X-ray Computed Tomography Instrument Performance Evaluation, Part II: Sensitivity to Rotation Stage Errors

2019 ◽  
Vol 124 ◽  
Author(s):  
Bala Muralikrishnan ◽  
Megan Shilling ◽  
Steve Phillips ◽  
Wei Ren ◽  
Vincent Lee ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Performance Evaluation ◽  
Test Procedures ◽  
X Ray ◽  
Measurement Volume ◽  
Form Errors ◽  
Sphere Center ◽  
X Ray Computed ◽  
Rotation Stage ◽  
Center Distance

The development of standards for evaluating the performance of X-ray computed tomography (XCT) instruments is ongoing within the American Society of Mechanical Engineers (ASME) and the International Organization for Standardization (ISO) working committees. A key challenge in developing documentary standards is to identify test procedures that are sensitive to known error sources. In Part I of this work, we described the effect of geometry errors associated with the detector and determined their influence through simulations on sphere center-to-center distance errors and sphere form errors for spheres located in the tomographically reconstructed measurement volume. We also introduced a new simulation method, the single-point ray tracing method, to efficiently perform the distance and form error computations and presented data validating the method. In this second part, also based on simulation studies, we describe the effect of errors associated with the rotation stage on sphere center-to-center distance errors and sphere form errors for spheres located in the tomographically reconstructed measurement volume. We recommend optimal sphere center locations that are most sensitive to rotation stage errors for consideration by documentary standards committees in the development of test procedures for performance evaluation.

scholarly journals X-Ray Computed Tomography Instrument Performance Evaluation, Part III: Sensitivity to Detector Geometry and Rotation Stage Errors at Different Magnifications

2021 ◽  
Vol 126 ◽  
Author(s):  
Prashanth Jaganmohan ◽  
Bala Muralikrishnan ◽  
Meghan Shilling ◽  
Edward Morse
Keyword(s):  
Computed Tomography ◽  
Performance Evaluation ◽  
Standardized Test ◽  
Optimal Placement ◽  
Test Procedures ◽  
X Ray ◽  
Measurement Volume ◽  
Detector Geometry ◽  
X Ray Computed ◽  
Rotation Stage

With steadily increasing use in dimensional metrology applications, especially for delicate parts and those with complex internal features, X-ray computed tomography (XCT) has transitioned from a medical imaging tool to an inspection tool in industrial metrology. This has resulted in the demand for standardized test procedures and performance evaluation standards to enable reliable comparison of different instruments and support claims of metrological traceability. To meet these emerging needs, the American Society of Mechanical Engineers (ASME) recently released the B89.4.23 standard for performance evaluation of XCT systems. There are also ongoing efforts within the International Organization for Standardization (ISO) to develop performance evaluation documentary standards that would allow users to compare measurement performance across instruments and verify manufacturer’s performance specifications. Designing these documentary standards involves identifying test procedures that are sensitive to known error sources. This paper, which is the third in a series, focuses on geometric errors associated with the detector and rotation stage of XCT instruments. Part I recommended positions of spheres in the measurement volume such that the sphere center-to-center distance error and sphere form errors are sensitive to the detector geometry errors. Part II reported similar studies on the errors associated with the rotation stage. The studies in Parts I and II only considered one position of the rotation stage and detector; i.e., the studies were conducted for a fixed measurement volume. Here, we extend these studies to include varying positions of the detector and rotation stage to study the effect of magnification. We report on the optimal placement of the stage and detector that can bring about the highest sensitivity to each error.

Evaluation Method to Determine Radial Error of Spindle Units on Simulation Turntable

2011 ◽  
Vol 460-461 ◽  
pp. 311-316
Author(s):  
Zhi Yong Qu ◽  
Jun Wei Han
Keyword(s):  
Small Angle ◽  
Evaluation Method ◽  
Simulation System ◽  
Transformation Matrix ◽  
Hardware In The Loop ◽  
Error Sources ◽  
Know How ◽  
Form Errors ◽  
Radial Error ◽  
Error Motion

Many errors including radial error influence the accuracy of simulation turntable, which is a crucial equipment in hardware-in-the-loop simulation system. The aim of this paper is to propose a new method of radial error motion separation of rotating spindle on a simulation turntable. Based on transformation matrix and small angle approximation, gesture transformation matrix with various error items is achieved. As a result of this analysis, form errors of master ball are corrected and the eccentricity from the rotation error of a spindle is separated. This radial error analysis is carried out when this measurement result is applied to a simulation turntable. Furthermore, this study also permits the user to know how to minimize some error sources of the spindle system.

An Empirical Approach for Identification of Sources of Machining Errors in Ultra-Precision Raster Milling

2007 ◽  
Vol 364-366 ◽  
pp. 986-991 ◽  
Author(s):  
Suet To ◽  
Hao Wang ◽  
Bing Li ◽  
Chi Fai Cheung
Keyword(s):  
Surface Roughness ◽  
High Precision ◽  
Surface Finish ◽  
Error Compensation ◽  
Diamond Tool ◽  
Empirical Approach ◽  
Error Sources ◽  
Form Errors ◽  
Machining Errors ◽  
Ultra Precision

Ultra-precision raster milling is one of the most significant techniques for the fabrication of high precision components with the surface roughness less than 10nm and form errors less than 0.2 um, without the need for any subsequent polishing. However, no matter how well a machine may be designed, there is a limit to the accuracy that can be achieved. This paper studies the machining errors caused by the diamond tool and the axis motions using Freeform 705G. With an empirical approach, the error sources are separated based on their effects on the surface finish. The main source leading to poor surface finish is identified. This establishes a basis for subsequent error compensation and equipment maintenance.

Assuring Molded Accuracy of Plastic Involute Worm Gears

2007 ◽  
Author(s):  
Michael T. Weiss ◽  
Roderick E. Kleiss
Keyword(s):  
Single Point ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Error Sources ◽  
Analysis Techniques ◽  
Gear Mesh ◽  
Package Size ◽  
Worm Gears ◽  
High Reduction ◽  
Gear Geometry

Many plastic geared transmissions contain crossed-axis worm drives in the first stage. The purpose is usually to achieve high reduction and/or tailored package size. The need for precision control of worm and helical gear geometry is just as important for this gear mesh as for any other. A myriad of molded flaws can degrade or destroy the performance of these gears. Pitch, tooth thickness, and lead errors are only a few possibilities. Barrel shaped, tapered, or hourglass bodies must be identified and controlled. Asymmetrical teeth are a distinct possibility as well. The only proper way to detect and evaluate these conditions is to scan and analyze these gears in three dimensions. The traditional method of scanning only one section of the tooth on a worm and then scanning the lead at the pitch line will not reveal many molded gear error sources. Measuring pitch or tooth thickness by taking single point measurements around the gear will also miss many errors. We have developed scanning and analysis techniques to accurately map the size and accuracy of these truly three-dimensional involute gear shapes.

Optimization of Well Placement

1999 ◽  
Vol 122 (2) ◽  
pp. 64-70 ◽  
Author(s):  
Baris Guyaguler ◽  
Roland Horne
Keyword(s):  
Hybrid Algorithm ◽  
Single Point ◽  
Optimization Technique ◽  
Search Space ◽  
Complex Problem ◽  
Production Optimization ◽  
Optimal Placement ◽  
Optimization Approach ◽  
Injection Wells ◽  
Well Placement

Optimal placement of oil, gas or water wells is a complex problem that depends on reservoir and fluid properties, well and surface equipment specifications, as well as economic parameters. An optimization approach that enables the evaluation of all these information is presented. A hybrid of the genetic algorithm (GA) forms the basis of the optimization technique. GA operators such as uniform, single-point, two-point crossover, uniform mutation, elitism, tournament and fitness scaling were used. An additional operator that employs kriging is proposed. The GA was hybridized with the polytope algorithm, which makes use of the trends in the search space. The hybrid algorithm was tested on a set of mathematical functions with different characteristics in order to determine the performance sensitivity to GA operators and hybridization. Simple test cases of oil production optimization on 16×16 simulation grids with known optimum well locations were carried out to verify the hybrid GA results. Next, runs were carried out for a 32×32 problem. The locations of a production and injection well were optimized in the case of three existing producers. Exhaustive runs were carried out for these cases to determine the effects of the operators, hybridization and the population size on the performance of the algorithm for well placement problems. Subsequently, the optimum configuration of two injection wells were determined with two existing producers in the field. It was observed that the hybrid algorithm is able to reduce the required number of simulations substantially over simple GA. [S0195-0738(00)00502-1]

Research note: Measurement of blue light hazard risk level using a hyperspectral camera

2019 ◽  
Vol 52 (5) ◽  
pp. 692-697
Author(s):  
T Shibuya ◽  
T Akiba ◽  
T Iwanaga
Keyword(s):  
Blue Light ◽  
Evaluation Method ◽  
Single Point ◽  
Spectral Radiance ◽  
Risk Level ◽  
Light Illumination ◽  
Risk Levels ◽  
Hazard Risk ◽  
Dimensional Measurements ◽  
Hyperspectral Camera

Using a calibrated hyperspectral camera, we evaluated the hazard risk level of blue light illumination using the IEC TR 62778:2014 method. The risk levels obtained using the hyperspectral camera were compared with those obtained using the method described in the IEC 62471:2006 guidelines. The IEC TR 62778:2014 risk level of each test product was the same as that obtained using the IEC 62471:2006 method. Compared with the evaluation method implemented using a conventional single-point measurement, our approach using a hyperspectral camera obtained spectral radiance measurements in a much shorter time, of the order of several seconds, via two-dimensional measurements.

Improvement of Single-Frequency GPS Positioning Performance Based on EGNOS Corrections in Algeria

2020 ◽  
Vol 73 (4) ◽  
pp. 846-860 ◽  
Author(s):  
Lahouaria Tabti ◽  
Salem Kahlouche ◽  
Belkacem Benadda ◽  
Bilal Beldjilali
Keyword(s):  
Global Positioning System ◽  
Single Point ◽  
Single Frequency ◽  
Positioning System ◽  
Ionospheric Correction ◽  
Error Sources ◽  
Positioning Accuracy ◽  
Gps Positioning ◽  
Global Positioning ◽  
Differential Corrections

The main objective of the European Geostationary Navigation Overlay System (EGNOS) is to improve the positioning accuracy by correcting several error sources affecting the Global Positioning System (GPS) and to provide integrity information to GPS signals for users in real time. This research presents analysis used to investigate improvement in the performance of single-frequency GPS positioning using EGNOS corrections in Algeria. In this study, we performed position measurements with two calculation approaches, the first based on GPS single-point positioning and the second using EGNOS differential corrections. Positioning accuracy was determined by comparison with the known precise coordinates of the sites; and then the improved ionospheric correction using EGNOS was investigated. The results revealed that GPS + EGNOS performance was significantly improved compared with GPS alone, when measurements of horizontal and vertical accuracy were taken into account, and that the EGNOS corrections improved east and north components slightly, and the up component significantly.

Quantifying Confidence Envelopes for Efficiency Values in the SR-30 Turbojet Engine

2011 ◽  
Author(s):  
Greg Buchan ◽  
Jenn Rossmann
Keyword(s):  
Combustion Chamber ◽  
Fluid Dynamic ◽  
Single Point ◽  
Outer Region ◽  
Optimal Placement ◽  
Thermodynamic Efficiency ◽  
Temperature Profiles ◽  
Fluid Dynamic Equation ◽  
Turbine Efficiency ◽  
Turbojet Engine

Turbojet engines power most of the large military and commercial aircraft in production today. These types of engines are chosen over conventional piston-driven engines because of the turbojet’s superior fuel economy and thrust. To understand how turbojet engines can be compared and optimized, it is necessary to fully characterize their performance. This is generally achieved by calculating thermodynamic efficiency values for each component in the engine, and for the engine as a whole. For this research project, the Turbine Technologies SR-30 centrifugal flow turbojet engine was investigated. An adjustable coupling was designed to permit a single-point thermocouple to be moved and secured within the engine. From the data taken at multiple locations and throttle settings, temperature profiles of the compression and combustion chambers were created. A thermal/fluid dynamic equation routine was developed using Engineering Equation Solver (EES), in order to propagate these temperature profiles through efficiency and thrust calculations. The temperature profiles did not significantly affect theoretical thrust values. However, the dependence of component efficiency values on spatial temperature variation within the engine was significant. In the compression chamber, it was found that a 30°C variation in the temperature across the chamber resulted in a 15% variation in the calculated compressor efficiency. In the inner region of the combustion chamber, a variation in 20°C yielded a 20% variation in calculated turbine efficiency. In the outer region of the combustion chamber, where the temperature varied by almost 400 degrees Celsius, the turbine efficiency varied by about 600%. This work suggests optimal placement of the compression and combustion stage thermocouples when the SR-30 turbojet is to be used for undergraduate laboratories. It also highlights the risks posed by relying on single-point measurements to characterize complex flows.

Error Sources in Atomic Force Microscopy for Dimensional Measurements: Taxonomy and Modeling

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
F. Marinello ◽  
S. Carmignato ◽  
A. Voltan ◽  
E. Savio ◽  
L. De Chiffre
Keyword(s):  
Mathematical Model ◽  
Atomic Force Microscopy ◽  
Scanning System ◽  
Thermal Drift ◽  
Scaling Effects ◽  
Error Sources ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dimensional Measurements ◽  
Squareness Errors

This paper aimed at identifying the error sources that occur in dimensional measurements performed using atomic force microscopy. In particular, a set of characterization techniques for errors quantification is presented. The discussion on error sources is organized in four main categories: scanning system, tip-surface interaction, environment, and data processing. The discussed errors include scaling effects, squareness errors, hysteresis, creep, tip convolution, and thermal drift. A mathematical model of the measurement system is eventually described, as a reference basis for errors characterization, with an applicative example on a reference silicon grating.

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