Full Measurement Range Research Articles

Optimization of parameters for a fringe projection measurement system by use of an improved differential evolution method.

Fringe projection 3D measurement is widely used for object surface reconstruction. While improving measurement accuracy is a crucial task. Measurement accuracy is profoundly affected by various optical structural parameters. However, the current practice of system construction lacks theoretical guidelines and often relies on the experience of the operator, inevitably leading to unpredictable error. This paper investigates a theoretical optimization model and proposes an automatic optimization method for qualitatively determining the multiple optimal optical structural parameters in fringe projection measurement system. The aim is to enhance measurement accuracy conducting a rational comprehensive optimal structural parameters design prior to the system construction. Firstly, the mathematical model of the measurement system is established based on the principle of optical triangulation, and the phase sensitivity criterion is defined as the optimization norm. Within the full measurement range, the optimization merit function is formulated by combing three positions: the center position, the left and right boundary of the CCD. The imaging effectiveness criteria and sensor geometric dimensions are taken into account as the constraint boundaries. Subsequently, a combined improved differential evolution and Levy flight optimization algorithm is applied to search for the optimal parameters. The optimal structural parameters of the system were designed based on the optimization process. Experimental results validated the improvement in measurement accuracy achieved by the optimized structural parameters.

Research on High Performance Methane Gas Concentration Sensor Based on Pyramid Beam Splitter Matrix.

Methane gas concentration detection faces the challenges of increasing accuracy and sensitivity, as well as high reliability in harsh environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve methane gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point-signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the four-channel methane gas concentration detection algorithm based on spectral refinement. Through the experiment, it was found that the sensor enables the full-range measurement of CH4; at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the limit of detection is 0.5 ppm. The sensor is still capable of achieving PPM-level detections under extreme conditions in which the sensor's optical window is covered by two-thirds and humidity is 85% or dust concentration is 100 mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Design of a Micro-Electro Mechanical System Quad Mass Gyroscope with Compliant Mechanical Amplification.

In this work, a novel mechanical amplification structure for a MEMS vibratory gyroscope is proposed with the aim of improving their sensitivity. The scheme is implemented using a system of micromachined V-shaped springs as a deflection amplifying mechanism. The effectiveness of the mechanism is first demonstrated for a capacitive fully decoupled quad mass gyroscope. A proof of concept vertical-axis mechanically amplified gyroscope with an amplification factor of 365% has been designed, simulated and fabricated, and results from its evaluation are presented in this paper. Experimental results show that the natural frequency of the gyroscope is 11.67 KHz, and the full scale measurement range is up to ±400°/s with a maximum nonlinearity of 54.69 ppm. The bias stability is 44.53°/h. The experiment results show that this quad mass gyroscope's performance is a very potential new way of reaching the navigation grade in the future.

Research on high performance combustible gas concentration sensor based on pyramid beam splitter matrix.

Combustible gas concentration detection faces challenges of increasing accuracy, and sensitivity, as well as high reliability in harsh using environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve combustible gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the 4-channel combustible gas concentration detection algorithm based on spectral refinement. Through experiment, it is found that the sensor enables full-range measurement of CH4, at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the sensor sensitivity is up to 0.5PPM. The sensor is still capable of achieving PPM-level detections, under extreme conditions in which the sensor's optical window is covered by 2/3, and humidity is 85% or dust concentration is 100mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Water-Cut Measurement Techniques in Oil Production and Processing—A Review

Water cut is a vital monitoring and surveillance parameter with great significance in oil production operations and processing. Water-cut measurements are also challenging due to the significant variations and the harsh measurement environment. The objective of this article is to review the current water-cut measurement techniques and suggest future areas that are expanding to overcome existing measurement challenges. Commercially available online methods such as capacitance-based sensors, tomography techniques, gamma densitometry, ultrasonic meters and infrared meters, and the traditional laboratory offline methods, are discussed, along with their principle of operation, detection range, and sensing resolution. Also, the discussed techniques are summarized, highlighting their main advantages and limitations. Furthermore, future trends and research areas, such as Artificial Intelligence (AI), soft computing, Metamaterials, and Nuclear Magnetic Resonance (NMR), which are integrated with water-cut measurements, are briefly mentioned. The current research hotspots are directed toward integrating full-range measurements with multi-parameter detection, high sensitivity, and reliability.

A Range-Extension Method for an Indoor Standard Device for Large-Scale Length Measurement

The Laser interferometer plays an important role in the field of geometrics for large-size measuring applications. Its linear displacement error can be traced from indoor large-scale standard devices. However, the measuring range of the indoor large-scale standard device is too limited to meet the full range measurement of the laser interferometer. So, the lack of accuracy of the results is one of the key issues of laser interferometers. To solve this problem, the corner reflector is used to extend the range of indoor large-scale standard devices, which meet the indication errors in the effective measuring range of the laser interferometer. The range-extension method not only doubles the effective measuring range, but also provides a way to trace the source of other large-size measuring instruments. This work proposes a significant solution to the field of length measurement.

Accurate Depth Recovery Method Based on the Fusion of Time-of-Flight and Dot-Coded Structured Light

3D vision technology has been gradually applied to intelligent terminals ever since Apple Inc. introduced structured light on iPhoneX. At present, time-of-flight (TOF) and laser speckle-based structured light (SL) are two mainstream technologies applied to intelligent terminals, both of which are widely regarded as efficient dynamic technologies, but with low accuracy. This paper explores a new approach to achieve accurate depth recovery by fusing TOF and our previous work—dot-coded SL (DCSL). TOF can obtain high-density depth information, but its results may be deformed due to multi-path interference (MPI) and reflectivity-related deviations. In contrast, DCSL can provide high-accuracy and noise-clean results, yet only a limited number of encoded points can be reconstructed. This inspired our idea to fuse them to obtain better results. In this method, the sparse result provided by DCSL can work as accurate “anchor points” to keep the correctness of the target scene’s structure, meanwhile, the dense result from TOF can guarantee full-range measurement. Experimental results show that by fusion, the MPI errors of TOF can be eliminated effectively. Dense and accurate results can be obtained successfully, which has great potential for application in the 3D vision task of intelligent terminals in the future.

Installation Quality Inspection for High Formwork Using Terrestrial Laser Scanning Technology

Current inspection for installation quality of high formwork is conducted by site managers based on personal experience and intuition. This non-systematic inspection is laborious and it is difficult to provide accurate dimension measurements for high formwork. The study proposed a method that uses terrestrial laser scanning (TLS) technology to collect the full range measurements of a high formwork and develop a genetic algorithm (GA) optimized artificial neutral network (ANN) model to improve measurement accuracy. First, a small-scale high formwork model set was established in the lab for scanning. Then, the collected multi-scan data were registered in a common reference system, and RGB value and symmetry of the structure were used to extract poles and tubes of the model set, removing all irrelevant data. Third, all the cross points of poles and tubes were generated. Next, the model set positioned on the moving equipment was scanned at different specified locations in order to collect sufficient data to develop an GA-ANN model that can generate accurate estimates of the point coordinates so that the accuracy of the dimension measurements can be achieved at the millimetre level. Validation experiments were conducted both on another model set and a real high formwork. The successful applications suggest that the proposed method is superior to other common techniques for obtaining the required data necessary for accurately measuring the overall structure dimensions, regarding data accuracy, cost and time. The study proposed an effective method for installation quality inspection for high formwork, especially when the inspection cannot be properly operated due to cost factors associated with common inspection methods.

Chirped pulse spectrally resolved interferometry without the direction ambiguity and the dead zone

In this investigation, a simple method is proposed to extend the measurement range of spectrally resolved interferometry, which is limited by the direction ambiguity and the dead zone. By stretching the measurement pulse, a derivative trend is generated to identify the direction using an unequal-path Mach–Zehnder fiber structure. Besides, the dead zone is eliminated by introducing a controllable optical path difference. The experimental results confirme that the full measurement range can be extend to more than twice.

Reflective Optical Fiber Sensor Based on Dual Fabry Perot Cavities for Simultaneous Measurement of Salinity and Temperature

A reflective optical fiber sensor that is composed of two Fabry Perot cavities is proposed for temperature and salinity measurement. One of the Fabry Perot cavity which is fabricated by offset splicing is exposed to the ambient directly to sense the ambient salinity, the other is employed to compensate for the temperature coupling effect. A thin layer of the gold film is coated on the refractive index change interface, which makes the spectrum quality is no longer limited by the refractive index difference between the two sides of the interface. By applying the frequency division multiplexing (FDM) technique and cavity length demodulation technology, the measurement range is no longer restricted to the free spectrum range (FSR), which can realize salinity measurement in the full measurement range. The proposed sensor can realize the salinity sensitivity better than 50 nm/‰ and temperature sensitivity of 6.85 nm/°C in the cavity length domain. It is promising for salinity measurement application for its merits of low cost, easy fabrication, and long sensing distance.

Thermodynamic Properties of Liquid Toluene from Speed-of-Sound Measurements at Temperatures from 283.15 K to 473.15 K and at Pressures up to 390 MPa

We report the speeds of sound in liquid toluene (methylbenzene) measured using double-path pulse-echo apparatus independently at The University of Western Australia (UWA) and Imperial College London (ICL). The UWA data were measured at temperatures between (306 and 423) K and at pressures up to 65 MPa with standard uncertainties of between (0.02 and 0.04)%. At ICL, measurements were made at temperatures between (283.15 and 473.15) K and at pressures up to 390 MPa with standard uncertainty of 0.06%. By means of thermodynamic integration, the measured sound-speed data were combined with initial density and isobaric heat capacity values obtained from extrapolated experimental data to derive a comprehensive set of thermodynamic properties of liquid toluene over the full measurement range. Extensive uncertainty analysis was performed by studying the response of derived properties to constant and dynamic perturbations of the sound-speed surface, as well as the initial density and heat capacity values. The relative expanded uncertainties at 95% confidence of derived density, isobaric heat capacity, isobaric expansivity, isochoric heat capacity, isothermal compressibility, isentropic compressibility, thermal pressure coefficient and internal pressure were estimated to be (0.2, 2.2, 1.0, 2.6, 0.6, 0.2, 1.0 and 2.7)%, respectively. Due to their low uncertainty, these data and derived properties should be well suited for developing a new and improved fundamental Helmholtz equation of state for toluene.

Regulatory Control of Mass Flowrate in an Ore Feeding System with Time-Delayed Gain-Variant Dynamics

Brazil is the world leading producer and exporter of iron ore, mainly due to operations of VALE, a global mining company with several operations in the country, delivering iron, copper, manganese, and nickel ores. Those operations are located mainly in the Northern state of Pará, and in the Southeastern state of Minas Gerais. From 2014 to 2019, the company’s average yearly production of iron ore was about 342 million t/year. Most of such production was exported overseas, mainly to Asian and European countries.Mineral processing plants implement several stages of ore beneficiation, necessary to convert raw ore from the mines into ore products. Those plants comprise several processing facilities as crushing, screening, grinding, flotation, and others, which are operated by means of a plantwide digital control system, either SCADA- or DCS-based, using many process control loops.The most important process variable in a mineral processing plant is the ore mass flowrate, measured in t/h. The transportation of ore between mineral facilities is usually done by belt conveyors, and the ore flowrate is measured by a conveyor weigher (also known as dynamic weigher or belt scale), which is a heavy instrument assembled directly in the conveyor structure [18]. The conveyor weigher has two primary sensors: piezoelectric loading cells to sense the unit weight of material on the belt, in t/m; and an incremental encoder to sense the belt moving speed, in m/s. By combining the unity load and the belt speed measurements, the weigher computes the material flowrate, in t/h, with a typical precision of ±0.5% of its full measurement range. The ore flowrate in a conveyor is not defined by the belt speed, but by the speed of the feeder that discharges the ore on the conveyor belt. Therefore, by changing the feeder (actuator) speed it is possible to control the ore flowrate using its measurements provided by the conveyor weigher (sensor).This work describes the modeling and control of ore flowrate for the ore feeding system “RF-A” of the Fábrica Iron Ore Processing Plant, in the city of Ouro Preto, Minas Gerais state, Brazil, operated by VALE. The next section introduces the industrial process and the control problem.

Метод измерения напряженности неоднородных электрических полей по среднему значению

Measurement and control of the intensity levels of inhomogeneous electric fields with high accuracy is quite a difficult task. The solution to this problem is connected both with the development of new sensors and methods for measuring the electric field strength. The creation of new high-precision electrical induction sensors has exhausted its capabilities at the current level of technology and technology. Therefore, new ideas are needed for solving the problems of high-precision measurement of the electric field strength. One of these ways is the development of new measurement methods. Existing measurement methods characterized by the complexity of the measurement processes, suitability in some cases, and unsuitability in others, do not provide the desired metrological characteristics. Therefore, the work related to the development of methods for measuring the intensity of inhomogeneous electric fields does not stand still, and is relevant. The aim of the study is to create a new method for measuring the strength of electric fields using known sensors, which makes it possible to significantly reduce the error in measuring inhomogeneous electric fields. The idea of constructing a new measurement method is formed. The idea of the method is that in the presence of two physical quantities measured with different sign values of the error, the average value of the physical quantity will always be closer to the true value. Based on this, a new method for measuring the intensity of inhomogeneous electric fields is proposed, associated only with the original measurement process. The measurement method id named «Average value method» (MSZ). The estimation of the error of this method shows a decrease in the measurement error to +5 % with the full spatial measurement range 0a1. Using the «Average value method» it is possible to achieve a significant increase in the accuracy of measuring the strength of inhomogeneous electric fields in a wide spatial range of measurements in comparison with known methods

Direct observation of temperature dependent vortex dynamics in a La0.7Sr0.3MnO3 micromagnet

This work explores the magnetization dynamics in an epitaxial nanomagnet. The authors link the observed vortex core switching dynamics to the critical velocity switching model using micromagnetic modeling.

A Compact and High-Precision Capacitive Absolute Angular Displacement Sensor

The present work proposes a compact capacitive absolute angular displacement sensor design that adopts a stator and rotor configuration with a double capacitive ring structure, where the outer ring is composed of n measurement periods that function as a fine measurement component, providing high precision measurements. The inner ring is composed of a single measurement period that functions as a coarse measurement component, thereby providing an absolute position measurement. High measurement accuracy is obtained by adopting single-row excitation electrodes with induction electrodes that adopt a differential sensing structure to eliminate common-mode interference. In addition to the double-ring structure, the compact size of the proposed sensor is facilitated by integrating the electrodes of the stator and rotor and the peripheral circuits required for their respective signal processing using printed circuit board technology. A prototype of the proposed sensor is fabricated with outer and inner radii, and aggregate thickness dimensions of 30 mm, 7 mm, and less than 10 mm, respectively. The sensor design is optimized accordingly by increasing the radial interval between the outer and inner rings and adding shielding. Finally, the experimental results show that the optimized sensor design achieves a precision of $12^{\prime \prime }$ and resolution of $0.31^{\prime \prime }$ over the full measurement range of 0° to 360°. As such, the proposed sensor design is demonstrated to realize the small mechanical dimensions suffered by absolute angular displacement sensors. Accordingly, the relatively low cost and low power consumption of the proposed sensor have excellent potential for a wide variety of applications.

An Innovative Dual-Axis Precision Level Based on Light Transmission and Refraction for Angle Measurement

Currently, the widely used pendulum-type precision level cannot be miniaturized because reducing the size of the pendulum will reduce its displacement so as to decrease the measurement accuracy and resolution. Moreover, the commercial pendulum-type level can only sense one direction. In this paper, an innovative compact and high-accuracy dual-axis precision level is proposed. Based on the optical principle of light refraction and the reference of the invariant liquid level, the pendulum is no more needed. In addition, based on the light transmission design, there is no reflection signal to interfere with the true signal. Therefore, the level can achieve a high accuracy and small-sized design. The calibration result shows the error of the proposed precision level is better than ±0.6 arc-sec in the measurement range of ±100 arc-sec, and better than ±5 arc-sec in the full measurement range of ±800 arc-sec.

Compensation of Phase-Uncertainty-Induced Impairments in Dispersion-Tuned Swept Laser OCT using Digital Coherent Detection

The dispersion-tuned swept laser (DTSL) is a wavelength-swept source, which can achieve fast sweep without using any mechanical tunable filter. Such fast wavelength-swept sources are highly suitable for swept-source optical coherent tomography (SS-OCT). DTSL-based SS-OCT (DTSL-OCT) can deliver a very fast imaging speed, however, it suffers from a limited imaging depth due to the its limited coherence length. In this article, digital coherent detection techniques are applied to the DTSL-OCT to improve the imaging depth and axial resolution. We show that the two phase-uncertainty-induced impairments, namely, the image degeneracy and the wavelength-sweep-nonlinearity, can be compensated by signal processing on the complex interferometric signals acquired using digital coherent detector. Removal of the mirror images resulting from complex conjugate artifact enables the full-range measurement, and the wavelength-sweep-nonlinearity compensation improves the axial resolution. We experimentally demonstrated that the OPD corresponding to a 6 dB-drop in the point-spread function (PSF) peak level can be improved from 1.4 mm to 7.2 mm.

Programmable synchronization enhanced MEMS resonant accelerometer

Acceleration measurement is of great significance due to its extensive applications in military/industrial fields. In recent years, scientists have been pursuing methods to improve the performance of accelerometers, particularly through seeking new sensing mechanisms. Herein, we present a synchronized oscillator-based enhancement approach to realize a fivefold resolution improvement of a microelectromechanical resonant accelerometer. Through the unidirectional electrical coupling method, we achieved synchronization of the sensing oscillator of the microelectromechanical resonant accelerometer and an external reading oscillator, which remarkably enhanced the stability of the oscillation system to 19.4 ppb and the resolution of the accelerometer to 1.91 μg. In addition, the narrow synchronization bandwidth of conventional synchronized oscillators was discussed, and hence, we propose a novel frequency automatic tracking system to expand the synchronization bandwidth from 113 to 1246 Hz, which covers the full acceleration measurement range of ±1 g. For the first time, we utilized a unidirectional electrical synchronization mechanism to improve the resolution of resonant sensors. Our comprehensive scheme provides a general and powerful solution for performance enhancement of any microelectromechanical system (MEMS) resonant sensor, thereby enabling a wide spectrum of applications.

A high-resolution area-change-based capacitive MEMS tilt sensor

Tilt sensors have been widely used in many applications, such as instrumentation leveling, oil drilling and structural health monitoring. With the rapid development of the micro-electromechanical system (MEMS) technology, MEMS accelerometer-based high-performance tilt sensors are capable of replacing conventional tilt sensors in most of application fields. High-sensitivity MEMS resonant accelerometers (MRAs) are fully qualified for tilt sensing. However, MRA chips have to be vacuum packaged and require complex circuits; therefore, they are difficult to be miniaturized and commercialized. In this case, this paper introduces a commercial-oriented capacitive MEMS accelerometer for tilt sensing with both high-resolution and compact size. The proposed MEMS sensor utilizes simplified fabrication processes, the area-change-based capacitive displacement transducer and the capacitance-to-voltage conversion application specific integrated circuit (ASIC) for low-cost, high-sensitivity, low power consumption and miniaturization. The developed MEMS sensor has a package dimension of 14 mm × 14 mm × 3.6 mm with a single +5 V power supply and analog voltage output. Several evaluation experiments have been conducted with the results showing that the developed MEMS tilt sensor has a full measurement range of ±180°, a linear measurement range of ±30° with a nonlinearity of ±2.8%, a sensitivity of 33.6 mV/°, a noise floor of 2 × 10−4°/√Hz, a bandwidth of 100 Hz and an angle resolution of 7 × 10−4° with an integral time of 0.5 s. Compared with other commercial MEMS tilt sensors, the proposed sensor has a better resolution, a lower noise floor, a larger bandwidth, a lower power consumption and a smaller package. The simplified fabrication process and high performance suggest the developed MEMS tilt sensor is promising to be competitive in the market.

Ultra-small pressure sensors fabricated using a scar-free microhole inter-etch and sealing (MIS) process

This paper presents a tiny 0.4 mm × 0.4 mm piezoresistive absolute pressure sensor chip with a fabrication cost as low as 0.01 US$/die. With the thin-film under bulk-silicon technique, a very thin but uniform poly-silicon pressure-sensing diaphragm is formed beneath a bulk-silicon beam-island structure to accommodate piezoresistors. The thin diaphragm exhibits a high sensitivity, and the beam-island-reinforced structure helps reduce deflection and improve linearity. The sensor is fabricated using a novel scar-free micro-hole inter-etch and sealing (MIS) process. In this newly developed process, seals are removed from the diaphragm area and placed on both the single-crystalline silicon island and single-crystalline silicon frame surrounding the poly-silicon diaphragm. Thus, the thin diaphragm is kept flat and smooth, thereby enhancing the sensing performance and fabrication yield. More importantly, the diaphragm-beam-island structure is small enough to fabricate sensor chips as small as 0.4 mm × 0.4 mm. With the high-yield process, a very low fabrication cost of 0.01 US$/die is realised owing to a high throughput of 90 000 die per 6 inch wafer. The ultra-small and low-cost pressure sensor exhibits sensitivity of 0.88 mV kPa−1/3.3 V, hysteresis of 0.15% full scale (FS), repeatability error of 0.04% FS, and non-linearity of 0.10% FS. Without any additional thermal compensation method, the sensor exhibits a low temperature coefficient of zero-point offset of −0.064%/°C FS and a temperature coefficient of sensitivity (TCS) of −0.22%/°C within the temperature range from −25 °C to +85 °C, at a full measurement range (i.e. full scale) of 100 kPa. With the new scar-free MIS process, the presented pressure sensor looks promising for smartphones, drones, and other consumer-electronic applications.