High-precision Displacement Sensor Research Articles

Study on fracture behaviour of pipeline girth welds based on curved wide plate specimens: Experimental and numerical analysis

Understanding the fracture characteristics and strain capacity of pipelines with girth welds under external loads is crucial for evaluating pipeline safety. The use of curved wide plate (CWP) specimens closely resembling full-scale (FS) pipelines in geometry provides a more realistic representation of crack tip constraint states compared to small-size fracture toughness test specimens in laboratory settings. This study aims to investigate the ductile fracture characteristics of center cracks on the outer surface of girth welds in high-grade steel pipelines under external loads through large-scale CWP tensile tests and advanced numerical simulations. Tensile tests were conducted on CWP specimens using a kiloton tensile testing machine, with double crack opening displacement (COD) gauge monitoring crack mouth opening displacement (CMOD), and high-precision displacement sensors and strain gauges tracking deformation and strains at various positions. The study yielded significant experimental results, and a finite element (FE) model of the CWP was developed using the nonlinear finite element method (FEM) to validate the experimental data against simulation results. The FE model was then used to investigate the influence of material properties on crack propagation resistance and driving force curves. A method for determining the ultimate tensile strain capacity (UTSC) of pipelines based on actual material fracture toughness was proposed. This research contributes valuable experimental data for further exploration of fracture behaviour in large-scale pipeline girth welds and offers insights for safety evaluations of such welds.

Development of Simplified Methods for Levitation Force Distribution in Maglev Vehicles Using Frequency Ratio Tests.

Maglev vehicles apply the entire vehicle load uniformly onto bridges through levitation forces. In assessing the dynamic characteristics of the maglev train-bridge coupling system, it is reasonable to simplify the distributed levitation force as a concentrated force. This article theoretically derives the analytical response of bridge dynamics under the action of a single constant force and conducts numerical simulations for a moving single constant force and a series of equally spaced constant forces passing over simply supported beams and two-span continuous beams, respectively. The topic of discussion is the response of bridge dynamics when different degrees of force concentration are involved. High-precision displacement and acceleration sensors were utilized to conduct tests on the Shanghai maglev line to verify the accuracy of the simulation results. The results indicate that when simplifying the distributed levitation force into a concentrated force model, a frequency ratio can be used to analyze the conditions for resonance between the train and the bridge and to calculate the critical speed of the train; the levitation distribution force of a high-speed maglev vehicle can be simplified into four groups of concentrated forces based on the number of levitation frames to achieve sufficient accuracy, with the dynamic response of the bridge being close to that under distributed loads.

High-Precision Capacitive Displacement Sensor for Gravitational Wave Detection: Sensitive Probe Modeling, Analysis, and Optimization

High-Precision Capacitive Displacement Sensor for Gravitational Wave Detection: Sensitive Probe Modeling, Analysis, and Optimization

Design of high-precision displacement safety monitoring and three-dimensional spatial alarm system for Beidou based on intelligent algorithms

The purpose of this study is to design a system that can monitor the displacement changes of engineering structures in real time and provide timely alarms when abnormal displacement is detected, in order to provide efficient safety monitoring and early warning functions and reduce the safety risks of engineering structures. The study adopted a combination of intelligent algorithms and the Global Satellite Navigation System (Beidou). By installing high-precision displacement sensors, monitor the displacement changes of the engineering structure. Then, intelligent algorithms are used to analyze and process the data collected by the sensors in real time, in order to extract the characteristics of displacement changes. At the same time, combined with the positioning data of the BeiDou navigation system, high-precision displacement monitoring is achieved. When the monitoring results exceed the set threshold, the system will automatically trigger an alarm mechanism to promptly notify relevant personnel for processing. Through experiments and comparative analysis, the Beidou high-precision displacement safety monitoring and 3D spatial alarm system based on intelligent algorithms designed in this study can effectively monitor and alarm displacement changes. The system has the characteristics of high accuracy, real-time performance, and reliability, which can timely detect displacement anomalies and provide reliable safety monitoring and warning functions.

Novel Information-Driven Smoothing Spline Linearization Method for High-Precision Displacement Sensors Based on Information Criterions.

A noise-resistant linearization model that reveals the true nonlinearity of the sensor is essential for retrieving accurate physical displacement from the signals captured by sensing electronics. In this paper, we propose a novel information-driven smoothing spline linearization method, which innovatively integrates one new and three standard information criterions into a smoothing spline for the high-precision displacement sensors' linearization. Using theoretical analysis and Monte Carlo simulation, the proposed linearization method is demonstrated to outperform traditional polynomial and spline linearization methods for high-precision displacement sensors with a low noise to range ratio in the 10-5 level. Validation experiments were carried out on two different types of displacement sensors to benchmark the performance of the proposed method compared to the polynomial models and the the non-smoothing cubic spline. The results show that the proposed method with the new modified Akaike Information Criterion stands out compared to the other linearization methods and can improve the residual nonlinearity by over 50% compared to the standard polynomial model. After being linearized via the proposed method, the residual nonlinearities reach as low as ±0.0311% F.S. (Full Scale of Range), for the 1.5 mm range chromatic confocal displacement sensor, and ±0.0047% F.S., for the 100 mm range laser triangulation displacement sensor.

Design and implementation of a measuring system used to evaluate the mechanical performance of the bone fixators

PurposeThis measuring system is designed to effectively simulate the mechanical reliability of the operated bone fixators. It can be used to pre-evaluate the mechanical performance of the operated fixator on the patients, including the static mechanical properties and fatigue properties when the patient walks after the operation.Design/methodology/approachIt is mainly composed of a one-dimensional platform, a force sensor, a high measuring precision displacement sensor and a servo motor. Loading (which is used to simulate the loading status of the fixators after the operation) of the system is realized by the rotation of the servo motor. It can be read by a high precision force sensor. The relative displacement of the broken bone is obtained by a high precision laser displacement sensor. Corresponding theoretical analysis is also carried out.FindingsCalibrated results of the system indicate that the output voltage and the measured force of the force sensors possess an excellent linear relationship, and the calculated nonlinear error is just 0.0002%. The maximum relative displacement between the operated broken bone under 700 N axial force is about 1 mm. Fatigue test under 550 N loading for 85,000 cycles also indicates the feasibility of the design.Originality/valueThis device is successfully designed and fabricated to pre-evaluate the mechanical performance of the bone fixators. High precision force sensor and displacement sensor are used to successfully increase the measuring ability of the system. This will offer some help to pertinent researchers.

Splicing Measurement and Compensation of Straightness Errors for Ultra-Precision Guideways.

The straightness error of guideways is one of the key indicators of an ultra-precision machine, which plays an important role in the machining accuracy of a workpiece. In order to measure the straightness error of a long-distance ultra-precision guideway accurately, a splicing measurement for the straightness error of a guideway using a high-precision flat mirror and displacement sensor was proposed in this paper, and the data splicing processing algorithm based on coordinate transformation was studied. Then, comparative experiments on a splicing measurement and direct measurement of the straightness error were carried out on a hydrostatic guideway grinder. The maximum difference between the two measurements was 0.3 μm, which was far less than the straightness error of 5.8 μm. The experiment demonstrated the correctness of the proposed splicing measurement method and data processing algorithm. To suppress the influence of the straightness error on machining accuracy, a straightness error compensation algorithm based on error rotation transformation and vertical axis position correction was proposed, and the grinding experiment of a plane optics with a size of 1400 mm × 500 mm was carried out. Without error compensation grinding, the flatness error of the element was 7.54 μm. After error compensation grinding, the flatness error was significantly reduced to 2.98 μm, which was less than the straightness errors of the guideways. These results demonstrated that the straightness error of the grinding machine had been well suppressed.

Broadband transverse unidirectional scattering and large range nanoscale displacement measuring based on the interaction between a tightly focused azimuthally polarized beam and a silicon hollow nanostructure.

We theoretically propose a broadband transverse unidirectional scattering scheme based on the interaction between a tightly focused azimuthally polarized beam (APB) and a silicon hollow nanostructure. When the nanostructure is located at a specific position in the focal plane of the APB, the transverse scattering fields can be decomposed into contributions from transverse components of the electric dipoles, longitudinal components of magnetic dipoles and magnetic quadrupole components. In order to satisfy the transverse Kerker conditions for these multipoles within a wide infrared spectrum, we design a novel nanostructure with hollow parallelepiped shape. Through numerical simulations and theoretical calculations, this scheme exhibits efficient transverse unidirectional scattering effects in the wavelength range of 1440 nm to 1820 nm (380 nm). In addition, by adjusting the position of the nanostructure on the x-axis, efficient nanoscale displacement sensing with large measuring ranges can be achieved. After analyses, the results prove that our research may have potential applications in the field of high-precision on-chip displacement sensors.

High-precision micro-displacement measurement in a modified reversal shearing interferometer using vortex beams

We propose a novel micro-displacement measurement system that employs a modified reversal shearing interference structure based on vortex beam interference. The micro-displacement in the measurement path caused a change in the light path and resulted in an optical path difference (OPD) between the reference and measurement paths. This OPD led to the rotation of the petal-like pattern obtained by the interference between two paths. The rotation angle of the petal-like pattern was proportional to the OPD caused by micro-displacement. We used the virtual phase-shifting method to extract the helical phase front, and the Radon transform to measure the angle of the helical phase front. We achieved a high-accuracy micro-displacement measurement with a measurement error of less than 0.067 nm when using a vortex beam with a topological charge of six. This system has an extremely simple structure and is easy to adjust. It is of great significance to the miniaturized design of high-precision displacement sensors.

Impact behavior of nylon kernmantle ropes for high-altitude fall protection

Aiming at the problem that the existing rope falling device can only detect the impact force and cannot synchronously detect the impact displacement, this paper introduces a large-range high-precision displacement sensor and constructs a rope impact force-displacement detection device. Taking the nylon kernmantle rope for high-altitude fall protection commonly used in aerial work and rock climbing as the research object, the impact response behavior of the rope when drop mass is dropped once and repeatedly is systematically studied, and the impact force and impact displacement are discussed. Further, the evolution of the elastic modulus of the rope is discussed and this could provide theoretical support for the design of the impact-resistant rope structure and the rope impact protection.

In-Situ Measurement and Slow-Tool-Servo Compensation Method of Roundness Error of a Precision Mandrel.

This paper describes a method for measuring and compensating the roundness error of a larger mandrel manufactured by an ultra-precision diamond-turning lathe aimed to obtain a calibration cylinder with a roundness of less than 0.1 μm. The diamond-turning machine has a cross-stacked hydrostatic guideway, produces a cutting depth and feed movement direction, and a dual-spindle system that is firmly connected to the bed. Due to the good repeatability of aerostatic spindles, only in situ rather than online real-time measurements are required. To this end, three high-precision capacitance displacement sensors were utilized to detect the cross-section of the workpiece and the time domain via the three-point error separation technique to separate the roundness error from the rotation motion error. The slow tool servo (STS) cutting technique was employed to compensate for the roundness error, which did not require extra axes, only the excellent dynamic response of the feed axis; hence, the servo control parameters could be suitably adjusted. The experimental results reveal that the low-order harmonic error, often caused by aerostatic spindles, is almost removed completely. For this particular lathe, the experiments indicate that about 60% of the rotational error motion is compensated, and the roundness error is reduced to less than 0.1 μm, which is evaluated by the least-squares circle method.

Redundant Parallel Beam Multiaxis Force Sensor—Accuracy Space

The principle of the redundant parallel beam multi-axis force sensor is a transformation from displacement domain to force domain. This paper proposed a general force error model of a distributed force measurement system with redundant multi-axis force sensors based on the measurement <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula> surveying adjustment method to transform displacement sensor errors to force errors. The optimum accuracy space is defined according to the error model. According to the accuracy space, the torque error increase sharply when the measuring point is far away from the optimum accuracy space, but the force error remains constant. A long-distance arrangement of displacement sensors can increase the size of the optimum accuracy space and a high-precision displacement sensor can increase the measurement accuracy in the whole space. A deformation filter can minimize the affection of the loading platform deformation on the measurement accuracy. A dual-measurement system is recommended to increase both the force accuracy and the torque accuracy when the measuring point is far from the optimum accuracy space of the main multi-axis force sensing system. The error point cloud is used to verify the proposed error model.

Centrifuge Model Tests and Numerical Simulations of the Landslide Evolution Process

Centrifuge model tests and numerical simulations were performed to study the landslide evolution process and failure mechanism. A TLJ-500 geotechnical centrifuge was used for the experiments and landslide deformation and stress was monitored using high-precision differential displacement sensors and earth pressure micro-sensors. Discrete element numerical simulations were performed using PFC2D based on the experimental results. The findings show that the landslide evolution process can be divided into three stages: 1) compaction and consolidation; 2) uniform deformation; and 3) accelerated deformation and failure. The numerical simulation results verify the distinct stage characteristics of the landslide evolution process. According to the migration of microscopic soil mass particles within the landslide, stage 3) can be further divided into a deformation development stage and instability and failure stage. The simulation displacement monitoring curves and displacement map show distinct deformation characteristics and displacement indicators from stages 2) to 3) and from the deformation development stage to the instability and failure stage. The experimental and numerical results reveal the landslide failure mechanism: the upper part of the landslide thrusts and slides; the middle part squeezes; the lower part collapses; and shear plane penetration leads to landslide failure.

A 22-bit image encoder with optoelectronic integrated chip

This study aims to design an optoelectronic integrated chip to read absolute code information. A detector array matching the code disk was designed to better realize high-speed low-light detection. For the pseudo-random code channel, the readout circuit adopted a linear array CMOS image sensor architecture, where each pixel corresponded to an independent readout unit, making the readout signal more advantageous in terms of both reading speed and noise. For the incremental code channel, the readout circuit followed a distributed arrangement design, and a two-stage pipelined amplifier architecture was adopted to eliminate the influence of even harmonics and ensure the quality of the read signal. Finally, a high-precision angular displacement sensor test platform based on an optical continuous closed-loop was built to test the encoder prototype equipped with the chip. The results show that an angular resolution of 22 bits and a subdivision accuracy of 5.64″ have been achieved.

A framework to obtain the formulas of the conductivity and aperture of rough fractures under thermohydromechanical conditions

In this investigation, a framework is proposed to find the equations to describe the fracture conductivity and fracture aperture as the functions of effective stress (the difference between geo-stress and fluid pressure), temperature difference (the difference between rock temperature and fluid temperature), and the rock mechanical properties. The framework consists of several lab experiments and a numerical model, which is time-saving to study the influences of the aforementioned influential factors on the fracture conductivity and aperture. After analyzing the lab experimental data, we find that it’s almost impossible to accurately measure the fracture aperture even with high-precision displacement sensors. Therefore, the numerical model coupling the fluid flow in the rough fracture, the solid deformation, and the heat transfer between the hot rock and the injected fluid is built. Three different distributions of the fracture surfaces are analyzed, and we find that the fracture surface roughness fits the normal distribution. After the data matching between the lab experimental data and the numerical results, a large number of numerical experiments using the numerical model are carried out to study the influences of the effective stress, temperature difference and the rock properties, including the elasticity and Poisson's ratio. When fitting the single variable analysis results, we find that the fracture conductivity and aperture are in different function forms of the aforementioned factors. But the reduction of fracture aperture and the natural logarithm of the normalized fracture conductivity can be described using the binary linear function of the effective stress and the temperature difference. Two key strengths of the research lie with the fact that it is time-saving to obtain the exact formulas of fracture conductivity and fracture aperture, and it can measure the dynamic fracture aperture accurately.

Accelerated life reliability evaluation of grating ruler for CNC machine tools based on competing risk model and incomplete data

Grating rulers are high-precision linear displacement sensors used in the servo control system of CNC machine tools. Due to the long lifetime of these rulers, evaluating their reliability level by using traditional methods takes huge amounts of time and resources. Meanwhile, some incomplete data are observed in the failure data, which will cause inaccurate evaluation results. In this study, an accelerated life reliability evaluation method of a grating ruler based on a competing risk model and incomplete data is proposed. Firstly, according to the characteristics of the grating ruler, the life distribution model based on competitive risk is established. The representation and conversion methods of failure data, considering incomplete data, are also proposed. Secondly, the accelerated life test (ALT) system is set up, and the 4500 h step stress ALT is conducted. Results indicate that the reliability level of the grating ruler is MTBFt = 8864.12 h, and that of each subsystem is MTBFt(MS) = 13,351.98 h, MTBFt(OS) = 14,283.48 h and MTBFt(ES) = 17,038.65 h. The advantages of the proposed method are that it is helpful in determining the subsystem with the highest failure rate in each stage and puts forward targeted suggestions for subsequent improvement designs.

Study of a high-precision displacement sensor based on a configured moving light field with uniform scanning

A new measuring method for uniform scanning is proposed in this paper. This method uses a moving light field to establish the relationship between displacement and time, and the displacement is measured by the time difference of the traveling wave signal. The high-precision moving light field is configured by the time and spatial orthogonal modulation of the light intensity. Experiments verified the feasibility of the proposed sensor, and the primary measurement error components were summarized. Combined with the experimental results and the mathematical model, the error rule of the uniformity of the moving light field was analyzed in detail, and the optimization scheme of a differential structure was proposed. Finally, a differential structure sensor was fabricated with a pitch of 0.6 mm in the range of 120 mm. After optimizing the design and the error correction, the measurement accuracy reached ±0.4 µm with a 1 nm resolution within the range of 120 mm, and the results demonstrated that high-precision measurement was achieved using sub-millimeter periods.

High-precision displacement sensor based on resonant cavities through an electronic interface based on Arduino

A novel stand-alone, high-precision, compact and cost-effective positioning sensor based on resonant cavities is described. It consists of two parts: the transducer based on radio frequency resonant cavities; and an electronic system that uses a voltage-controlled oscillator (VCO), a mixer as phase detector, and an Arduino interface to find the voltage through which the VCO operates the transducer. The resonant frequency of the device is directly related to a voltage null in the mixer output signal, in such a way that its measurement allows to deduce the correct driving signal value. This value represents the complete system displacement.Experimental tests have proven the effectiveness of the presented system in proposed displacement measurement tests performed in the range of micrometers.

High-Precision Large-Displacement Measuring Method with Walking Pattern

A method for measuring large displacements >800 mm with a precision of 0.0094% and an accuracy of 0.0125%, realizing the principle of measurement with walking pattern and utilizing two analog high-precision small displacement sensors as the measuring unit is presented. A self-tuning fuzzy PID controller with high adaptability is used to make two identical measuring subsystems work coordinately for reaching a large displacement measurement. A series of tests are conducted to verify the effectiveness of the method. The results show that this method has a good performance. The influence of the mechanical deformation on measuring precision is discussed, and the functional relationship between mechanical structural deformation and measuring error is found in the experiment. A feasible compensation scheme is built to eliminate the error caused by mechanical deformation.

Development of Under–anchorage Effective Prestress Detecting Instrument and Engineering Application

For detecting under–anchorage effective prestress of steel strand by lift–off test convenient. Revealing the testing principle of lift–off text and developing the testing in strument. The instrument consists of data acquisition card, oil pressure sensor, high precision displacement sensor and electric oil pump. Based on the graphical software platform LabVIEW, the test program is compiled by using G language. And further gives the program source code. Integrating the texting instrument (LTF 1.0) of under–anchorage effective prestress based on the software and hardware. So the engineering application is carried out. The research results show that the instrument can detect the under-anchorage effective prestress effectively by the load–displacement curve. Meanwhile it has the advantages of high precision, good safety and convenient operation. Through field application, the effective prestress of prestressed steel strand anchor was increased from 54.4% to 94.7%, and same strand dispersion was reduced from 10.2% to 1.7%.