Instantaneous Rotational Speed Measurement Using Image Correlation and Periodicity Determination Algorithms

Dynamic and accurate measurement of instantaneous rotational speed is desirable in many industrial processes for both condition monitoring and safety control purposes. This paper presents a novel imaging based system for instantaneous rotational speed measurement. The low-cost imaging device focuses on the side surface of a rotating shaft without the use of a marker, entailing benefits of non-contact measurement, low maintenance and wide applicability. Meanwhile, new periodicity determination methods based on the Chirp-Z transform and parabolic interpolation based auto-correlation algorithm are proposed to process the signal of similarity level reconstructed using an image correlation algorithm. Experimental investigations are conducted on a purpose-built test rig to quantify the effects of the periodicity determination algorithm, frame rate, image resolution, exposure time, illumination conditions, and photographic angle on the accuracy and reliability of the measurement system. Experimental results under steady and transient operating conditions demonstrate that the system is capable of providing measurements of a constant or gradually varying speed with a relative error no greater than ±0.6% over a speed range from 100 to 3000 RPM (Revolutions Per Minute). Under step change conditions the proposed system can achieve valid speed measurement with a maximum error of 1.4%

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

Development of a wafer geometry measuring system : a double sided stitching interferometer

The drive for miniaturization of electrical devices and the increased production size of chips has forced lithographic production techniques to improve continuously. With this the requirements for silicon wafers, which form the basis of chips, have increased continuously as well. To ??nd a cost e??ective solution for the characterization of large diameter double side polished silicon wafers, the development of a measurement machine has been started. The measurement machine should measure the free form ??atness and thickness variations of wafers with a diameter of up to, and possibly beyond, 300 mm. The proposed measurement concept should have the potential to achieve a high throughput and a low measurement uncertainty, while reducing the cost of ownership signi??cantly compared to currently available systems on the market. The designed measurement setup which is described in this thesis is intended to demonstrate the potential of a chosen measurement concept for measuring double side polished silicon wafers. In the innovative measurement concept a double sided stitching Fizeau type interferometer has been adopted. A surface interferometer o??ers the required high accuracy and the scanning principle of a small aperture stitching interferometer allows the use of relatively small and low cost optical components which can measure with a high spatial resolution. The self referencing capability of a double sided Fizeau interferometer is important for achieving high accuracy when measuring thickness variations. In the proposed measurement concept the aperture of a single interferometer is split to measure the frontside and backside ??atness of a wafer simultaneously. The thickness variations can be derived from the measured ??atness measurements. A prototype measurement setup has been designed, built and tested. All major mechanical and optical error sources have been eliminated by using advanced calibration techniques. By using proper measurement principles and advanced software a robust and traceable wafer thickness and ??atness measurement instrument is created for measuring nominally ??at objects. The developed calibration techniques enable low uncertainty measurements to be taken while using relatively low quality optical and mechanical components. Several measurement method have been applied to derive accurate geometrical parameters from the recorded interferograms. Besides the processing of interferograms and development of calibration techniques a surface stitching software package has been developed which combines many subaperture ??atness maps into a large scale ??atness map of the entire wafer

Molecular-Based Optical Measurement Techniques for Transition and Turbulence in High-Speed Flow

High-speed laminar-to-turbulent transition and turbulence affect the control of flight vehicles, the heat transfer rate to a flight vehicle's surface, the material selected to protect such vehicles from high heating loads, the ultimate weight of a flight vehicle due to the presence of thermal protection systems, the efficiency of fuel-air mixing processes in high-speed combustion applications, etc. Gaining a fundamental understanding of the physical mechanisms involved in the transition process will lead to the development of predictive capabilities that can identify transition location and its impact on parameters like surface heating. Currently, there is no general theory that can completely describe the transition-to-turbulence process. However, transition research has led to the identification of the predominant pathways by which this process occurs. For a truly physics-based model of transition to be developed, the individual stages in the paths leading to the onset of fully turbulent flow must be well understood. This requires that each pathway be computationally modeled and experimentally characterized and validated. This may also lead to the discovery of new physical pathways. This document is intended to describe molecular based measurement techniques that have been developed, addressing the needs of the high-speed transition-to-turbulence and high-speed turbulence research fields. In particular, we focus on techniques that have either been used to study high speed transition and turbulence or techniques that show promise for studying these flows. This review is not exhaustive. In addition to the probe-based techniques described in the previous paragraph, several other classes of measurement techniques that are, or could be, used to study high speed transition and turbulence are excluded from this manuscript. For example, surface measurement techniques such as pressure and temperature paint, phosphor thermography, skin friction measurements and photogrammetry (for model attitude and deformation measurement) are excluded to limit the scope of this report. Other physical probes such as heat flux gauges, total temperature probes are also excluded. We further exclude measurement techniques that require particle seeding though particle based methods may still be useful in many high speed flow applications. This manuscript details some of the more widely used molecular-based measurement techniques for studying transition and turbulence: laser-induced fluorescence (LIF), Rayleigh and Raman Scattering and coherent anti-Stokes Raman scattering (CARS). These techniques are emphasized, in part, because of the prior experience of the authors. Additional molecular based techniques are described, albeit in less detail. Where possible, an effort is made to compare the relative advantages and disadvantages of the various measurement techniques, although these comparisons can be subjective views of the authors. Finally, the manuscript concludes by evaluating the different measurement techniques in view of the precision requirements described in this chapter. Additional requirements and considerations are discussed to assist with choosing an optical measurement technique for a given application

Development of temporal phase unwrapping algorithms for depth-resolved measurements using an electronically tuned Ti:Sa laser

This thesis is concerned with (a) the development of full-field, multi-axis and phase contrast wavelength scanning interferometer, using an electronically tuned CW Ti:Sa laser for the study of depth resolved measurements in composite materials such as GFRPs and (b) the development of temporal phase unwrapping algorithms for depth re-solved measurements. Item (a) was part of the ultimate goal of successfully extracting the 3-D, depth-resolved, constituent parameters (Young s modulus E, Poisson s ratio v etc.) that define the mechanical behaviour of composite materials like GFRPs. Considering the success of OCT as an imaging modality, a wavelength scanning interferometer (WSI) capable of imaging the intensity AND the phase of the interference signal was proposed as the preferred technique to provide the volumetric displacement/strain fields (Note that displacement/strain fields are analogous to phase fields and thus a phase-contrast interferometer is of particular interest in this case). These would then be passed to the VFM and yield the sought parameters provided the loading scheme is known. As a result, a number of key opto-mechanical hardware was developed. First, a multiple channel (x6) tomographic interferometer realised in a Mach-Zehnder arrangement was built. Each of the three channels would provide the necessary information to extract the three orthogonal displacement/strain components while the other three are complementary and were included in the design in order to maximize the penetration depth (sample illuminated from both sides). Second, a miniature uniaxial (tensile and/or compression) loading machine was designed and built for the introduction of controlled and low magnitude displacements. Last, a rotation stage for the experimental determination of the sensitivity vectors and the re-registration of the volumetric data from the six channels was also designed and built. Unfortunately, due to the critical failure of the Ti:Sa laser data collection using the last two items was not possible. However, preliminary results at a single wavelength suggested that the above items work as expected. Item (b) involved the development of an optical sensor for the dynamic monitoring of wavenumber changes during a full 100 nm scan. The sensor is comprised of a set of four wedges in a Fizeau interferometer setup that became part of the multi-axis interferometer (7th channel). Its development became relevant due to the large amount of mode-hops present during a full scan of the Ti:Sa source. These are associated to the physics of the laser and have the undesirable effect of randomising the signal and thus preventing successful depth reconstructions. The multi-wedge sensor was designed so that it provides simultaneously high wavenumber change resolution and immunity to the large wavenumber jumps from the Ti:Sa. The analysis algorithms for the extraction of the sought wavenumber changes were based on 2-D Fourier transform method followed by temporal phase unwrapping. At first, the performance of the sensor was tested against that of a high-end commercial wavemeter for a limited scan of 1nm. A root mean square (rms) difference in measured wavenumber shift between the two of ∼4 m-1 has been achieved, equivalent to an rms wavelength shift error of ∼0.4 pm. Second, by resampling the interference signal and the wavenumber-change axis onto a uniformly sampled k-space, depth resolutions that are close to the theoretical limits were achieved for scans of up to 37 nm. Access of the full 100 nm range that is characterised by wavelength steps down to picometers level was achieved by introducing a number of improvements to the original temporal phase unwrapping algorithm reported in ref [1] tailored to depth resolved measurements. These involved the estimation and suppression of intensity background artefacts, improvements on the 2-D Fourier transform phase detection based on a previously developed algorithm in ref [2] and finally the introduction of two modifications to the original TPU. Both approaches are adaptive and involve signal re-referencing at regular intervals throughout the scan. Their purpose is to compensate for systematic and non-systematic errors owing to a small error in the value of R (a scaling factor applied to the lower sensitivity wedge phase-change signal used to unwrap the higher sensitivity one), or small changes in R with wavelength due to the possibility of a mismatch in the refractive dispersion curves of the wedges and/or a mismatch in the wedge angles. A hybrid approach combining both methods was proposed and used to analyse the data from each of the four wedges. It was found to give the most robust results of all the techniques considered, with a clear Fourier peak at the expected frequency, with significantly reduced spectral artefacts and identical depth resolutions for all four wedges of 2.2 μm measured at FWHM. The ability of the phase unwrapping strategy in resolving the aforementioned issues was demonstrated by successfully measuring the absolute thickness of four fused silica glasses using real experimental data. The results were compared with independent micrometer measurements and showed excellent agreement. Finally, due to the lack of additional experimental data and in an attempt to justify the validity of the proposed temporal phase unwrapping strategy termed as the hybrid approach, a set of simulations that closely matched the parameters characterising the real experimental data set analysed were produced and were subsequently analysed. The results of this final test justify that the various fixes included in the hybrid approach have not evolved to solve the problems of a particular data set but are rather of general nature thereby, highlighting its importance for PC-WSI applications concerning the processing and analysis of large scans

Asteroseismology and Interferometry

Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like pulsators, have boosted the impact of this field of research within Astrophysics and have led to a significant increase in the size of the research community. In the present paper we start by reviewing the basic observational and theoretical properties of classical and solar-like pulsators and present results from some of the most recent and outstanding studies of these stars. We centre our review on those classes of pulsators for which interferometric studies are expected to provide a significant input. We discuss current limitations to asteroseismic studies, including difficulties in mode identification and in the accurate determination of global parameters of pulsating stars, and, after a brief review of those aspects of interferometry that are most relevant in this context, anticipate how interferometric observations may contribute to overcome these limitations. Moreover, we present results of recent pilot studies of pulsating stars involving both asteroseismic and interferometric constraints and look into the future, summarizing ongoing efforts concerning the development of future instruments and satellite missions which are expected to have an impact in this field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume 14, Issue 3-4, pp. 217-36

The quantitative analysis of transonic flows by holographic interferometry

This thesis explores the feasibility of routine transonic flow analysis by holographic interferometry. Holography is potentially an important quantitative flow diagnostic, because whole-field data is acquired non-intrusively without the use of particle seeding. Holographic recording geometries are assessed and an image plane specular illumination configuration is shown to reduce speckle noise and maximise the depth-of-field of the reconstructed images. Initially, a NACA 0012 aerofoil is wind tunnel tested to investigate the analysis of two-dimensional flows. A method is developed for extracting whole-field density data from the reconstructed interferograms. Fringe analysis errors axe quantified using a combination of experimental and computer generated imagery. The results are compared quantitatively with a laminar boundary layer Navier-Stokes computational fluid dynamics (CFD) prediction. Agreement of the data is excellent, except in the separated wake where the experimental boundary layer has undergone turbulent transition. A second wind tunnel test, on a cone-cylinder model, demonstrates the feasibility of recording multi-directional interferometric projections using holographic optical elements (HOE’s). The prototype system is highly compact and combines the versatility of diffractive elements with the efficiency of refractive components. The processed interferograms are compared to an integrated Euler CFD prediction and it is shown that the experimental shock cone is elliptical due to flow confinement. Tomographic reconstruction algorithms are reviewed for analysing density projections of a three-dimensional flow. Algebraic reconstruction methods are studied in greater detail, because they produce accurate results when the data is ill-posed. The performance of these algorithms is assessed using CFD input data and it is shown that a reconstruction accuracy of approximately 1% may be obtained when sixteen projections are recorded over a viewing angle of ±58°. The effect of noise on the data is also quantified and methods are suggested for visualising and reconstructing obstructed flow regions

Investigation of bipolar charge distribution of pharmaceutical dry powder aerosols using the phase doppler anemometry system

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.Electrostatic properties of formulation component materials and blends play an important role in dry powder inhalation (DPI) products, and that valid measurement of charge distribution will lead to more precise control of powder behavior in DPI manufacturing processes. Ultra-fine powders are known to be bipolarly charged, have non-spherical shapes and tend to be highly cohesive. Real time, non-invasive techniques need to be developed to obtain a precise and accurate time-history characteristic of electrically charged powders as they aerosolize from a DPI product, and how this measure relates to materials behavior throughout the various steps of a manufacturing process i.e. from drug micronisation, blending with lactose, through to filling dose units. A novel non-invasive technique for simultaneous measurement of size and charge of pharmaceutical powders is considered which employs the Phase Doppler Anemometry (PDA) system. Previous research demonstrated the advantages of this technique in measuring the bipolar charge distribution on a population of particles. These findings led to significant improvements in understanding performance of dry powder formulations, manufacturing processes and development of new platforms for inhaled drug delivery. The main aim of this research is to perform an investigation of electrostatic propertiesof pharmaceutical dry aerosols using the PDA system. The PDA technique was used to track the motion of charged particles in the presence of an electric field. The magnitude as well as the polarity of the particle charge can be obtained by solving the equation of particle motion in DC and AC fields combined with the simultaneous measurement of its size and velocity. The results show the capability of the technique to allow real-time size and charge distribution in the control of dry powder attributes that are critical to fully understanding manufacturing design space. The data obtained from initial investigations of electrical properties of pharmaceutical powders and bipolar charge measurements was used to perform an in-depth study of electrostatic properties of pharmaceutical aerosols dispensed by dry powder inhaler (DPI) devices. The delivery of a drug to the lungs can only be achieved by a combination of inhaler device and drug formulation which is capable of producing an aerosol of an aerodynamic diameter smaller than 5 μm and of appropriate charge. The aerosols generated by these devices are often bipolarly charged and can influence specific site deposition in human lung. By controlling the electrostatic charge generated by tribielectrification, it may be possible to achieve the desired drug deposition in the airways. Bipolary charged dispensed ultrafine particles are inhaled through the extrathoracic and tracheobronchial airways down into the alveolar region. Anatomically realistic respiratory airways and computation fluid dynamics (CFD) models have been created to study airflow structures and predict aerosol deposition within the human respiratory system using visible human data sets, human casts and morphometric data. Many theoretical studies of charged aerosol deposition in human respiratory systems have been developed, however getting real time, non-intrusive data of bipolar charge levels on aerosols dispensed from DPI’s within the human respiratory system represents a challenging issue. This research project presents a simplified human upper airway model which combined with the modified Phase Doppler Anemometry (PDA) system is able to provide real time bipolar charge distributions of aerosols delivered from several commercially available DPI devices. A three dimensional (3D) reconstruction of the upper respiratory system was performed from two dimensional (2D) images obtained from computerized tomography (CT), magnetic resonance imaging (MRI) and cryosectioned images available from Visible Human Server data set (Ecole Polytechnique Fédérale de Lausanne). The resulting dimensions of the model were consistent with morphometric data from the literature from which the simplified upper airway model consisting of two connected segments, i.e., the oral airways from the mouth to trachea (Generation G0), was created. The findings of this study provided a better understanding of the interaction between specific active ingredients and DPI devices. These results may be used in designing future generation DPI devices and a better understanding of aerosol transport and deposition efficiency within the human airways.Engineering and Physical Sciences Research Council. Pfizer team, U

Applied Measurement Systems

Measurement is a multidisciplinary experimental science. Measurement systems synergistically blend science, engineering and statistical methods to provide fundamental data for research, design and development, control of processes and operations, and facilitate safe and economic performance of systems. In recent years, measuring techniques have expanded rapidly and gained maturity, through extensive research activities and hardware advancements. With individual chapters authored by eminent professionals in their respective topics, Applied Measurement Systems attempts to provide a comprehensive presentation and in-depth guidance on some of the key applied and advanced topics in measurements for scientists, engineers and educators