Angle Measurement Method Research Articles

A new method for testing wide range horizontal field angle

In order to solve the problems of small measurement range, large error and low efficiency of laboratory optical field angle testing, a high-precision, easy -operating, high-efficient, and widely used horizontal field angle test method is proposed. It comes to a conclusion that the test method can reduce the experimental error through the analysis of the principle of the field of view error and the calculation of laboratory simulation. The simulation results show that for cameras with a field of view of more than 150 degrees, the measurement error can be reduced by 37 degrees, and when the field of view of the camera under test is close to 170 degrees, the method can reduce the measurement error by nearly 54 degrees. Meanwhile, a wide-range horizontal field angle measurement method is proposed. The camera under test is moved on the supporting mobile platform to image the target test board, and then the imaging target is read by reading the scale value on the test board calculates the angle of the camera under test. This method can effectively avoid the measurement error of the angle caused by the distance between the center of the lens surface and the center of the entrance pupil, so as to quickly obtain the angle of view test results, and improve the testing accuracy, and it is also suitable for cameras that measure a wide range of field angles (wide-angle camera or fisheye camera, etc.) to solve the problem of laboratory testing a wide range of horizontal field angles.

Is Proximal Tibia Sufficient for Accurate Measurement of Tibial Slope Angles on Three-dimensional Tomography-based Anatomical Models?

Tibial slope measurements performed using only the proximal part of tibia ignore the native tibial anatomical axis. Our first aim is to measure the native medial, lateral and total tibial slope angles of gender groups using the whole tibial anatomical axis on computerized tomography-based three-dimensional anatomical models. The second aim is to determine the correlation between proximal and whole tibial anatomical axis for measurement of medial, lateral, and total tibial slope angles. We randomly selected 100 females and 100 males between 18-60 years of age. Three-dimensional anatomical models of right and left tibia were created. The gender-specific differences of medial, lateral, and total tibial slope angles according to proximal and whole tibial anatomical axis were measured. Correlation coefficients (r) of medial, lateral, and total tibial slope angles measured with proximal and whole tibial anatomical axis were calculated. The mean age was 47.1 years. A statistically significant difference was observed between female (7.1 ± 3) and male (8.2 ± 2.5) groups in terms of mean lateral tibial slope angles according to the whole tibial anatomical axis (p=0.008). A strong correlation between proximal and whole tibial anatomical axis for all tibial slope angle measurements was detected. The method we determined for 3D measurement of medial, lateral and total tibial slope angles using proximal tibial anatomical axis has a strong correlation with slope angles measured in accordance with the whole tibial anatomical axis. Our 3D tibial slope angle measurement method on the proximal tibia has high reliability and could be used in the daily practice.

Robust vision-based method for wing deflection angle measurement with defocus images

The accuracy of existing vision-based angle measurement methods is extremely reduced when the images appear defocus. To solve this problem, a robust center location method for defocus circular targets is proposed and sub-pixel accuracy of control points can be obtained even with defocus images. Based on this location method, two vision-based angle measurement methods are proposed to measure deflection angles for fixed-axis and moving-axis wings, respectively. These methods are simple and easy to install with no need of prior information of wings’ structure or rotation axes. Simulation and real experiments show that the proposed methods have good robustness to image noise and can significantly reduce the measurement errors of defocus images. The proposed methods almost keep unchanging to the results at good focus status, and the measurement accuracy under severe defocus blur state is about 60% higher than that of the state-of-art method for comparison.

Automatic software-based 3D-angular measurement for Weight-Bearing CT (WBCT) provides different angles than measurement by hand

BackgroundPurpose of this study was to compare automatic software-based angular measurement (AM, Autometrics, Curvebeam, Warrington, PA, USA) with previously validated measurement by hand (MBH) regarding angle values and time spent for the investigator for Weight-Bearing CT (WBCT). MethodsFive-hundred bilateral WBCT scans (PedCAT, Curvebeam, Warrington, PA, USA) were included in the study. Five angles (1st - 2nd intermetatarsal angle, talo-metatarsal 1-angle (TMT) dorsoplantar and lateral projection, hindfoot angle, calcaneal pitch angle) were measured with MBH and AM on the foot/ankle (side with pathology). Angles and time spent of MBH and AM were compared (t-test, homoscedatic). ResultsThe specific pathologies were ankle osteoarthritis/instability, n = 147 (29%); Haglund deformity/Achillodynia, n = 41 (8%); forefoot deformity, n = 108 (22%); Hallux rigidus, n = 37 (7%); flatfoot, n = 35 (7%); cavus foot, n = 10 (2%); osteoarthritis except ankle, n = 82 (16%). The angles differed between MBH and AM (each p < 0.001) except the calcaneal pitch angle (p = 0.05). The time spent for MBH / AM was 44.5 ± 12 s / 1 ± 0 s on average per angle (p < 0.0011). ConclusionsAM provided different angles as MBH and can currently not be considered as validated angle measurement method. The investigator time spent is 97% lower for AM (1 s per angle) than for MBH (44.5 s per angle). Cases with correct angles in combination with almost no time spent showed the real potential of AM. The AM system will have to become reliable (especially in diminishing positive and negative angle values as defined) and valid which has to be proven by planned studies in the future. Level of evidenceLevel III

Prediction of Dielectric Breakdown of OHTL Insulators Using Contact Angle Measurements

Porcelain insulators used in overhead transmission lines (OHTL) are exposed to pollution when operational. To observe the effect of external pollution on these insulators, the relationship between the flashover voltage and surface contamination was studied. The flashover voltage drops sharply when contaminants in the wind are deposited on the surface of the insulators in a humid environment. Under wet conditions, the flashover voltage demonstrates a difference of approximately 10 kV depending on the contamination levels. The higher the equivalent salt deposit density, the lower the contact angle. In particular, the flashover voltage under wet conditions decreases exponentially when the contact angle is below 30°. In this case, the condensation area becomes considerably wider, thus exhibiting the difference in the area of the electrolytic conductive film layer forming the leakage path on the surface. Depending on the equivalent salt deposit density and contact angle, the area of condensation is more than doubled. To measure the level of contamination on the surface using this principle, a contact angle measurement method was adopted to predict the dielectric breakdown of the insulator.

New ellipse-fitting method for contact angle measurement

In this work, the authors examined the commonly used fitting methods for optical contact angle measurement. It was shown that currently, there is no available fitting method that can measure the contact angle of a non-axisymmetric drop without a clear view of the drop baseline. This work contributes to contact angle measurement methods by providing a new ellipse-fitting method. The new method fits the drop profile with a general equation of an ellipse whose major and minor axes are not necessarily parallel and normal with the substrate, respectively. The advantage of this method is that it can measure the contact angle of a non-axisymmetric drop without a clear view of the drop baseline. The measurement results were validated by comparing against the DropSnake and polynomial fitting methods. Generally good agreement was seen, which is important as it validates this method as the only available method for finding the contact angle of a droplet when the contact line is not visible – for example, in a condensation environment where many drops can block the view of each other’s contact line.

An unconventional approach in investigating wettability contact angle measurement in shale resources

Wettability measurement is important in production development to newly discovered as well as mature reservoirs. Evaluating the wettability is exceptionally important (for its significant-yields in hydrocarbon quantities) in oil and gas production schemes for newly discovered reservoirs such as shale reservoirs and other unconventional plays. Shale wettability has its unique fluid-mineral distribution relationships, which makes both pore morphology as well as mineral composition very significant factors controlling its wettability. The complex shale physical, chemical, and crystollgraphical constituent’s mineralogy as well as its physical pore morphology heterogeneity can complicate the wettability measurement further inside the pore structure fabrication, and hence the ultimate oil/gas recovery. The main objective of this study is to investigate the complexity of heterogeneous mineral structure of shale as well as its complex pore structure and its attributes toward the unconventional imaging method of wettability contact angle measurement.

A contribution to flotation technique as a reliable wettability alteration measurement method for carbonate minerals in separation processes involving hydrocarbons, low salinity water and nanofluids

A reliable flotation method was developed and experimentally evaluated as a fast and repeatable quantitative wettability measurement technique for Enhanced Oil Recovery (EOR) purposes by comparing its performance with the well-known and reliable method of contact angle measurement. In both methods, oil-wet carbonate specimens were contacted with brines of different salinities and nanoparticle concentrations, and the trend of test results were compared. In the salinity tests, it was observed that flotation results are in full consistency with contact angle measurements. In both methods, salinity reduction from seawater (SW) to 10 times diluted seawater (TDSW) resulted in reaching the maximum hydrophilicity while further dilution to 40 TDSW hindered the wettability alteration process. Nanofluid tests in both methods were also in great consistency at nanoparticle concentrations below 0.1%wt due to particle stability limitations. Finally, two flotation mechanisms for the oil/water/rock system were introduced and one of them was empirically confirmed.

Alternative methods for measuring ankle-foot orthosis alignment in clinical care

Changes in gait due to an ankle foot orthosis (AFO) have been shown to be impacted by the sagittal plane alignment of the AFO, but there is variability in practice and lack of consensus as to how this alignment should be measured. The neutral angle is a measure of AFO alignment that has the potential to be used by various specialties that prescribe, provide, and analyze AFOs. Currently, a lack of validated measurement methods prevents the neutral angle from being used in various clinical settings. Two experimental neutral angle measurement methods are proposed to address this shortcoming: a portable low-cost method for use during AFO fabrication and fitting, and a laboratory-based method for use during dynamic three-dimensional gait analysis (3DGA). What is the concurrent validity of the two experimental neutral angle measurement methods against the gold standard? The gold standard neutral angle measurement (NAGOLD) was prospectively collected during a static 3DGA trial for 19 pediatric AFOs from 10 individuals. While NAGOLD was being collected, the neutral angle was simultaneously measured using digital differential inclinometers (NAINCL). Within the same 3DGA session, the neutral angle was also measured during the swing phase of gait (NASWING). The NAINCL and NASWING measurements were compared to NAGOLD using repeated measures ANOVA, ICC, and bootstrapped errors-in-variables regressions. Repeated measures ANOVA indicated no differences between measurement methods (p = 0.43) and ICC analysis indicated good absolute agreement (ICC(A-1) = 0.85). Mean absolute deviations between the NAINCL and NASWING with NAGOLD measurements were 2.4 ° and 1.9 °, with standard deviations of 2.9 ° and 2.7 °, respectively. Maximum observed differences were less than 7 °. The NAINCL and NASWING methods explained 74 % and 81 % of the variance in NAGOLD, respectively. The concurrent validity of two new neutral angle measurement methods provides alternative means to assess AFO alignment in the clinic.

Method of reaching a resolution-controllable micro-angle measurement by using a Michelson interferometer.

A novel, to the best of our knowledge, method is proposed in this study to permit the controllable resolution of a micro-angle measurement by using a Michelson interferometer. The resolution of the proposed system can be adjusted by changing the distances between a pair of parallel mirrors. Through experiments, it was observed that as the distance was changed from 0 to 6 mm, the corresponding resolution was significantly altered from 22.88 to 14.02 µrad. Compared with other small angle measurement methods, the proposed method can realize the conversion of multiple measurement resolutions more easily and conveniently.

Contact angle measurement using a Hele-Shaw cell: A proof-of-concept study

Contact angle is an important property to quantify the wettability of a solid surface with a liquid, which characterizes interactions of the solid-liquid pair. Generally, to measure contact angle, special instruments such as a goniometer are necessary, but they are not readily available in certain research settings. In this study, an alternative method to measure contact angle based on a Hele-Shaw cell, microscopy imaging, and image processing is suggested. In this method, a liquid drop is injected into a transparent Hele-Shaw cell, the meniscus of the drop is captured in the top or bottom view using a brightfield microscope, and the contact angle is measured from the captured image based on a geometrical model of the drop in the Hele-Shaw cell. The proposed method was tested using two different liquids (deionized water and glycerol) and two different solid surfaces (polydimethylsiloxane [PDMS] and commercial water-repellent-coated glass) with various gap heights of Hele-Shaw cells and validated in comparison with a goniometer. Our results show that the proposed method could measure contact angles reasonably well. Although the concept of the proposed quick-and-dirty contact angle measurement method was proven in this study, there is still room to improve the accuracy and reliability of the proposed method.

Characterization of microstructure and surface properties of GLC film deposited in plasma nitriding system

Graphite-like carbon films were deposited on silicon substrates in plasma nitriding system with propane and hydrogen. Scanning electron microscope, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscope, and contact angle measurement method were used to investigate the effect of voltage, duty cycle, and gas composition on the growth thickness, hydrogen content, atomic bond structure, surface roughness, surface morphology, and wettability of the films. It is shown that the thickness of the films decreased with the voltage and duty cycle increasing. The voltage, duty cycle and gas composition have a significant effect on the sp2/sp3 bonds and hydrogen content, which can produce the a-C:H films characterized by sp2 bonding (over 70%). As the voltage and duty cycle improved, the surface morphology of the film progressed from a rugged surface with wide hillsides to a flat level surface. This work will provide a novel method to produce graphite-like carbon films with lubricating and anti-wear properties and give direction on designing high-performance tribo-systems for industrial applications.

Self-compensation method for dual-beam roll angle measurement of linear stages.

In this paper, a self-compensation method for improving the accuracy of roll angle measurement of a linear stage caused by the non-parallelism of dual-beam due to time-dependent mechanical deformation of the support is proposed and integrated into a 5-DOF sensor to verify the feasibility. The non-parallelism between two laser beams is online real-time monitored by a pair of small autocollimator units. Through the ray-tracing analysis, the method to separate the roll angle of the moving stage and non-parallelism induced roll error is determined. A series of experiments under different supporting forces and ambient conditions have been carried out. The compensated P-V values of the roll angles are all within ±4 arc-sec, no matter how bad the originally measured value of the linear stage is. The average improvement of about 95% is significant. The effectiveness and robustness of the proposed measurement system in the changing environment are verified.

A Visual-Based Angle Measurement Method Using the Rotating Spot Images: Mathematic Modeling and Experiment Validation

An angle measurement method based on the rotating spot images and machine vision technology is proposed. This method abandons the traditional coding disk but uses image sensor to capture the images of a spot rotating synchronously with the measured shaft. Assuming the center of the rotation shaft is fixed, the mathematic model of the trajectory of the spot images is an ellipse. N spot images are used to fit the ellipse equation, where the eccentric angle of the ellipse is the measured rotation angle. The basic algorithms and a compact lensless transmission angle measurement structure are also proposed. The simulation and experiment results are verified the feasibility of the measurement method, where the 5.4” accuracy can be obtained and a random collection of N ≥ 36 spot images is recommended. Since the shape of the ellipse trajectory does not affect the measurement accuracy, this method allows the spot disk to be non-concentric with the rotating shaft, and allows the spot disk to be non-parallel to the image sensor. Therefore, the proposed method can achieve precision measurement under non-precision installation.

Distortion correction based on off-axis Schwarzschild two-mirror hyperspectral imager.

A new method of distortion correction based on the off-axis Schwarzschild two-mirror hyperspectral imager is proposed in this paper. The polynomial model is used to indicate the distortion in the pushbroom direction and the correction method is based on linear feature. The radial distortion model is used to indicate the vertical pushbroom direction of distortion and the correction method is based on the cross ratio invariance. Compared with the common precision angle measurement method, this method is simple and efficient. This method can be applied to the distortion correction of the non-mapping pushbroom hyperspectral imager.

Affinity Analysis of Photoacid Generator in the Thin Film of Chemical Amplification Resist by Contact Angle Measurement

In extreme ultraviolet (EUV) lithography development, the reduction of line width roughness (LWR) is a one of the significant issues. It has been reported that the LWR of photoacid generator (PAG) bounded resist is lower than that of PAG blended resist. It is considered that the chemical composition distribution of PAG bounded resist is more uniform than PAG blended resist. However, it has not been evaluated systematically and experimentally. In this study, we introduced the contact angle measurement method for the evaluation of the chemical composition distribution between PAG blended resist and PAG bounded resist. It is clarified that the resist thin film has a different chemical composition distribution from the center to the outside of wafer regardless of the type of resists. In particular, the chemical composition distribution of the bounded resist showed the opposite behavior to that the blended one.

Stray Flux-Based Rotation Angle Measurement for Bearing Fault Diagnosis in Variable-Speed BLDC Motors

Angle of rotation is a key parameter in motor fault diagnosis under varying speed conditions, and is usually measured by an optical encoder. However, the use of encoders is intrusive and in many scenarios its signal is difficult to access due to technical or commercial reasons. In this study, a novel rotation angle measurement method based on stray flux analysis is proposed and applied to bearing fault diagnosis of brushless direct-current (BLDC) motors. The measurement accuracy of the proposed method is comparable to that from an encoder. The developed method is flexible, noninvasive, and nondestructive. It is easy to implement and eliminates the need for long cables and access of the motor control system. The proposed method can be extended to the diagnosis of motor electrical and drive faults. If implemented with an Internet of Things (IoT) or a hand-held device, it can further improve the reliability of sensorless motor drive systems in industrial automation so as to meet Industry 4.0 requirements.

Research on High Precision Angle Measurement and Compensation Technology Based on Circular Grating

In this paper, the angle measurement method of high-precision circular grating is studied. The principle analysis of circular grating angle measurement, the principle analysis of multi reading head, and the design of rotary servo control system are carried out. After analyzing the error model of circular grating angle measurement, the research based on harmonic compensation model is carried out respectively. Aiming at the problem of zero crossing oscillation of compensation algorithm, the piecewise compensation strategy is designed, which fully demonstrates the application value of circular grating angle measurement method in high-precision angle measurement system.

Design of airborne radar Attitude Test System Based on servo drive

This paper presents a design method of airborne radar attitude test system based on servo drive, which can realize the closed-loop test of servo system, the separate test of antenna drive module, the separate test of scanner base and the attitude test. The system adopts the attitude angle measurement method based on fiber laser gyroscope as the core, which can realize scanning angle: azimuth ±0.2° and pitch. By decoupling the disturbance and the measured, the small angle attitude algorithm is designed and corrected. The test results show that the scanning accuracy of the attitude determination system can be controlled ±0.2°, and through the modular instrument of PXI bus, the test efficiency and equipment fault maintenance ability of airborne radar can be improved.

Single-Sensor Vibration-Scanning Method for Assessing the Mechanical Properties of 3D Printed Elements.

This paper considers issues related to the assessment of the mechanical properties of elements made with 3D printing technology. To enable experimental testing, an automated test stand was built to perform amplitude and phase angle measurements of any point of the specimen. A contactless, optical measurement method was selected, as it is especially adequate when it comes to elements with small dimensions and masses. One innovative element of the test stand is the original method of phase angle measurement using a single vibration sensor fitted with a system forcing and ensuring full measurement synchronization and dynamic state repeatability. Additionally, numerical models of tested objects were produced and simulations of their oscillations were performed. Based on that, the properties of the tested material (PLA) were considered, with a special focus on the density, elastic modulus, and damping. The analyses were conducted for a few elements with different dimensions at different vibration frequencies.