Micro-displacement Sensor Research Articles

Design, Analysis, and Implementation of the Subdivision Interpolation Technique for the Grating Interferometric Micro-Displacement Sensor

A high-resolution grating interferometric micro-displacement sensor utilizing the subdivision interpolation technique is proposed and experimentally demonstrated. As the interference laser intensity varies sinusoidally with displacement, subdivision interpolation is a promising technique to achieve micro-displacement detection with a high resolution and linearity. However, interpolation errors occur due to the phase imbalance, offset error, and amplitude mismatch between the orthogonal signals. To address these issues, a subdivision interpolation circuit, along with 90-degree phase-shifter and high-precision DC bias-voltage techniques, converts an analog sinusoidal signal into standard incremental digital signals. This novel methodology ensures that its performance is least affected by the nonidealities induced by fabrication and assembly errors. Detailed design, analysis, and experimentation studies have been conducted to validate the proposed methodology. The experimental results demonstrate that the micro-displacement sensor based on grating interferometry achieved a displacement resolution of less than 1.9 nm, an accuracy of 99.8%, and a subdivision interpolation factor of 208. This research provides a significant guide for achieving high-precision grating interferometric displacement measurements.

Balloon-shaped fiber surface nanoscale axial photonic microresonator for micro-displacement measurement.

In this Letter, we demonstrate a micro-displacement sensor based on a balloon-shaped fiber surface nanoscale axial photonic (SNAP) microresonator. The SNAP microresonator is fabricated by fiber bending to introduce nanoscale effective radius variations (ERVs) on the fiber surface. Displacement measurement based on the balloon-shaped SNAP microresonator is realized based on the ERV modulation resulting from the change in the bending radius of the balloon-shaped structure. An advantage of this approach is that the displacement measurement range is not limited to the axial length of the SNAP region. The experimental results show that the displacement measurement range of the balloon-shaped fiber SNAP microresonator can reach 2500 µm and that the minimum measurement resolution is 0.1 µm. This large-range, high-resolution, and low-cost micro-displacement sensor has the potential to be a promising candidate in high-precision displacement measurement applications.

Research on Temperature-Insensitive Micro-Displacement Sensor Cascaded With Spherical Structure

Research on Temperature-Insensitive Micro-Displacement Sensor Cascaded With Spherical Structure

Single-Ended Eddy Current Micro-Displacement Sensor with High Precision Based on Temperature Compensation.

To measure the micro-displacement reliably with high precision, a single-ended eddy current sensor based on temperature compensation was studied in detail. At first, the principle of the eddy current sensor was introduced, and the manufacturing method of the probe was given. The overall design plan for the processing circuit was induced by analyzing the characteristics of the probe output signal. The variation in the probe output signal was converted to pulses with different widths, and then it was introduced to the digital phase discriminator along with a reference signal. The output from the digital phase discriminator was processed by a low-pass filter to obtain the DC component. At last, the signal was amplified and compensated to reduce the influence of temperature. The selection criteria of the frequency of the exciting signal and the design of the signal conditioning circuit were described in detail, as well as the design of the temperature-compensating circuit based on the digital potentiometer with an embedded temperature sensor. Finally, an experimental setup was constructed to test the sensor, and the results were given. The results show that nonlinearity exists in the single-ended eddy current sensor with a large range. When the range is 500 μm, the resolution can reach 46 nm, and the repeatability error is ±0.70% FR. Within the temperature range from +2 °C to +58 °C, the voltage fluctuation in the sensor is reduced to 44 mV after temperature compensation compared to the value of 586 mV before compensation. The proposed plan is verified to be feasible, and the measuring range, precision, and target material should be considered in real-world applications.

In-Plane and Out-of-Plane 2-D Microdisplacement Sensor Based on a Single Microwave Resonator With Machine Learning

In-Plane and Out-of-Plane 2-D Microdisplacement Sensor Based on a Single Microwave Resonator With Machine Learning

Large-range and high-sensitivity displacement sensing based on a SNAP microresonator by multimode encoding technique

Probe-type micro-displacement sensors with a large range and high sensitivity have important applications in both aerospace and nano-lithography. However, the state-of-the-art measurement range achieved using conventional methods such as charge coupled device imaging and fiber grating demodulation is limited to only tens of micrometers. In this study, we propose and demonstrate a displacement sensing mechanism with a large range and high sensitivity for measuring linear displacements. The mechanism is based on a multimode encoding technique implemented on a surface nanoscale axial photonics (SNAP) microcavity platform. By tracking the transmittance variations of multiple axial modes and employing encoding techniques, we can determine the rough absolute position as well as the axial mode with the highest sensitivity in each region. Moreover, the selected mode for each region is exploited to accurately measure the micro-displacement with a large range and high accuracy. As a proof-of-principle experiment, the results indicate a large sensing range about 346 μm and a high sensitivity ranging up to 0.013 μm−1. Assuming that the transmittance can be resolved by 0.1%, the resolution of the measurement is about 0.1 μm.

Tunable sensitivity microfiber Sagnac loop based on a virtual reference arm for microdisplacement detection

A virtual reference arm-based microfiber Sagnac ring (MFSL) microdisplacement sensor with tunable sensitivity is proposed and demonstrated in this study. We abandon the traditional physical reference arm and build a virtual reference arm to overcome the disadvantage of the physical reference arm being susceptible to environmental influences and to achieve tunable sensitivity. A MFSL with a diameter of 4 μm was fabricated via the winding and tapering process, and a microdisplacement sensitivity of −0.34 nm/μm was obtained in the range of 0–5 μm. Experimental results show that the microdisplacement sensitivity can reach −1.40 nm/μm after cascading the simulated reference arm, which is 4.12 times that of single MFSL. In addition, by changing the parameters of the virtual reference arm without remaking the reference arm, we obtained sensors with sensitivities of −1.74 and −2.30 nm/μm. The sensor has advantages of tunable sensitivity and low cost and has potential applications in microdisplacement measurement.

High-Sensitivity and Direction Recognizable SPR Microdisplacement Sensor Based on Fiber V-Groove

It is difficult to further improve the sensitivity of fiber surface plasmon resonance (SPR) microdisplacement sensor, and it is also unable to identify the direction of microdisplacement. In this article, a high-sensitivity direction recognizable SPR microdisplacement sensor based on fiber V-groove was designed and fabricated. By CO2 laser, the V-groove was fabricated on the graded index multimode fiber, and the SPR effect was produced on the inclined plane of the sensing area by the microdisplacement beam. By controlling the flare angle of the fabricated V-groove, the SPR incident angle was adjusted, so as to effectively increase the microdisplacement sensing sensitivity. The simulation and test results indicate that the sensor with the V-groove flare angle of 88° has the wavelength average sensitivity of 5.26 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and the intensity average sensitivity of 0.032 a.u./ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . In order to solve the problem of microdisplacement direction identification, a dual V-groove structure microdisplacement sensor was designed and fabricated. When the microdisplacement direction is different, the transmission beam contacts different V-grooves, and the microdisplacement direction can be identified by the moving direction of the resonance valley. The proposed sensor greatly improves the sensitivity of optical fiber SPR microdisplacement detection and can identify the direction of microdisplacement, which has the potential application value in the field of precision displacement and positioning.

Micro-displacement sensor based on an asymmetric wavy multimode fiber interferometer

Micro-displacement sensor based on an asymmetric wavy multimode fiber interferometer

Precision Low-Cost Compact Micro-Displacement Sensors Based on a New Arrangement of Cascaded Levers with Flexural Joints

Existing displacement sensors of micrometers to sub-micron precision are expensive and have various limitations. This paper reports the design and development of a new contact type compact micro-displacement sensor of sub-micron precision for a fraction of the cost of commercial devices. The basic concept of the new sensor system applies a mechanical magnifying mechanism to magnify a displacement at sub-micron to micron level and uses a low-cost Hall sensor to measure the magnified displacement. Various conceptual designs for the mechanical magnifying mechanism based on cascaded levers with flexural joints were studied and a final design, featuring side-by-side placement of lever structures in a multi-planar layout with adjacent levers coupled by L-shaped coupling foils, was devised. Prototypes of two different sizes and constructions with mechanical magnification ratios over 100 were made and tested. Measurement repeatability and accuracy to sub-micrometer level and a resolution down to hundredths of a micrometer were demonstrated by a compact Alpha Model prototype. Design modification of parts and a corresponding small lot size production procedure were devised to provide an estimated bill of material cost per unit under US$100.

A Micron-Range Displacement Sensor Based on Thermo-Optically Tuned Whispering Gallery Modes in a Microcapillary Resonator.

A novel micron-range displacement sensor based on a whispering-gallery mode (WGM) microcapillary resonator filled with a nematic liquid crystal (LC) and a magnetic nanoparticle- coated fiber half-taper is proposed and experimentally demonstrated. In the proposed device, the tip of a fiber half-taper coated with a thin layer of magnetic nanoparticles (MNPs) moves inside the LC-filled microcapillary resonator along its axis. The input end of the fiber half-taper is connected to a pump laser source and due to the thermo-optic effect within the MNPs, the fiber tip acts as point heat source increasing the temperature of the LC material in its vicinity. An increase in the LC temperature leads to a decrease in its effective refractive index, which in turn causes spectral shift of the WGM resonances monitored in the transmission spectrum of the coupling fiber. The spectral shift of the WGMs is proportional to the displacement of the MNP-coated tip with respect to the microcapillary's light coupling point. The sensor's operation is simulated considering heat transfer in the microcapillary filled with a LC material having a negative thermo-optic coefficient. The simulations are in a good agreement with the WGMs spectral shift observed experimentally. A sensitivity to displacement of 15.44 pm/µm and a response time of 260 ms were demonstrated for the proposed sensor. The device also shows good reversibility and repeatability of response. The proposed micro-displacement sensor has potential applications in micro-manufacturing, precision measurement and medical instruments.

Ultra-sensitive micro-displacement sensor based on a U-shaped bent SMF

Sensors based on irregularly shaped bent optical fiber devices have attracted considerable interest in many applications. However, the effective interference length and bent radius of the irregular shape fiber have not been given accurately. Here an equivalent arc model is proposed to define the effective interference length and bent radius of the U-shaped fiber device: the U-shaped optical fiber is equivalent to a regular arc. We found that the effective interference length of devices varies greatly with the structure's height changes in some special structure sizes, which is highly useful for micro-displacement measurement. In terms of this model, an ultra-sensitive micro-displacement sensor of -1.2838nm/µm in a measurement range of 0-60 µm has been realized. The sensitivity of this device is one order of magnitude higher than that in any previously reported bent optical fiber work. More importantly, the analysis strategy of the equivalent arc model can be generalized to various irregular bent fiber micro-displacement sensors and other sensing fields.

High sensitivity micro-displacement sensor based on fiber Bragg grating and amplification substrate

High sensitivity micro-displacement sensor based on fiber Bragg grating and amplification substrate

Photonic Barcodes Based on a SNAP Microcavity for Displacement Sensing

Barcodes, as a representation of data describing information of the object, have been demonstrated to have a great value for tracking and identifying large amounts of information in our daily lives. Here, we demonstrate a surface nanoscale axial photonics (SNAP) microcavity multimode displacement sensing technology based on photonic barcodes. Based on the characteristic parameters of each order axial mode in the resonance spectrum of SNAP microcavity, the resonance spectrum is converted into a barcode. The correlation coefficient between the barcode to be detected and the standard barcode is calculated by using the method of cross-correlation function to achieve rapid and accurate identification of microcavity displacement. Simulations demonstrate the feasibility of displacement sensing based on photonic barcodes. When the signal-to-noise ratio (SNR) of the noise-containing spectrum is 10 dB, the identification error of the displacement is ± <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.2 ~\mu \text{m}$ </tex-math></inline-formula> using the discrete wavelet transform (DWT) hard threshold denoising method. This work not only can directly read the displacement from the spectrum, but also has a strong resistance to environmental interference, which lays the foundation for the development of a high-precision, large-range micro-displacement sensor.

Experimental investigation on mechanical characteristics of low-voltage driving traveling-wave ultrasonic motor with the flexible rotor

Classical traveling-wave ultrasonic motors (TWUMs) usually generate the elliptical clusters on the stator surface through the bending vibration of the annular stator on the basis of piezoelectric excitation, and the torque output and power transmission are realized by friction coupling under the rational preload. Stable and reliable working characteristics attracted the focus of various applications. High energy consumption and low efficiency are restricted factors for the service performance of motors. Displacement amplification and stress regulation based on flexible design become a possible approach to improve motor performances. In this study, a TWUM30 prototype was proposed with consideration of (sub) structure optimization, i.e., tooth height and backlash of the stator elastomer. The flexible design of the rotor structure was carried out for consideration of the contact area and stress regulation. After integrated bonding of the stator and PZT4, the electrical and vibration characteristics of the stator prototype are measured by an impedance analyzer and high-precision laser micro-displacement sensor. Results showed that the proposed TWUM30 is capable of operation under low-voltage driving (41.9 kHz @ 80 Vp), and the extreme mechanical performances presented the stall toque of 64mN∙m and the no-load speed of 153.8 rpm. With the combination of the flexible design and systematic integrated manufacturing of the stator/rotor, low-voltage driving of the TWUM30 motor under ultra-low preload was realized at low cost and the adverse effects of excessive preload were suppressed. This study is expected to provide support for high reliability design and long-life service of the TWUMs. It also provides a realistic possibility for the flexible design and application of energy-saving and high-efficient traveling-wave piezoelectric drivers.

Development of a nanoscale displacement sensor based on the shadow method.

A novel, to the best of our knowledge, bionic coaxial micro-displacement sensor based on the shadow method is developed and experimentally demonstrated inspired by the water strider walking on the water. The water is used as the sensitive element to measure the micro- displacement. A meniscus is formed by the superhydrophobic circular plate subjected to a coaxial displacement excitation. Then a shadow is formed because of the refraction when the parallel light illuminates the meniscus. A maximum coaxial displacement sensitivity of 62 nm/pixel over the displacement range of 50 µm is achieved experimentally. The linearity error in the measurement range was 1.58%. Therefore, it is expected that this displacement sensor can be used in many important ultraprecision measurement fields because of the advantages of the easy structure and high resolution.

High-precision micro-displacement sensor based on tunnel magneto-resistance effect

A high-precision micro-displacement sensor based on tunnel magneto-resistance effect is reported.We designed and simulated magnetic characteristics of the sensor, and employed chip-level Au-In bonding to implement low-temperature assembly of the TMR devices. We employed the subdivision interpolation technique to enhance the resolution by translating the sine-cosine outputs of a TMR sensor into an output that varies linearly with the displacement. Simultaneously, using the multi-bridge circuit method to suppress external magnetic and geomagnetic interference. Experimental result shows that the micro-displacement sensor has a resolution of 800 nm, accuracy of 0.14% and a full-scale range of up to millimeter level. This work enables a high-performance displacement sensor, and provides a significant guide for the design of a micro-displacement sensor in practical applications.

Model Analysis of Sandstone Tunnel Cracking Based on Fracture Mechanics Theory and Sensor Testing Technology Research

In this paper, we survey sandstone tunnels using sensor testing technology and conduct an in-depth analysis and research on the model of sandstone tunnel cracking based on the theory of fracture mechanics. This paper systematically investigates the static mechanical properties, energy evolution and distribution law, acoustic emission monitoring, and digital image correlation methods of intact and jointed rock chamber enclosures (including parallel jointed rock chamber enclosures and cross jointed rock chamber enclosures) under static loads, based on physical simulation test methods and combined with other technical means such as acoustic emission monitoring and digital image correlation methods. In this paper, the effects of parallel and cross-joint angles on the static mechanical properties, energy evolution and distribution, acoustic emission variability, progressive destabilization, and their mechanisms are compared and analyzed. This paper takes fiber Bragg grating (FBG) sensing theory and technology research as a breakthrough, relies on major underground engineering geohazard model tests, and proposes a grating spectral reconstruction theory based on the wavelength position constraint of the spectral center and its improvement based on an in-depth analysis of the influence of fiber grating intrinsic parameters and strain distribution on the reflection spectral properties. Based on an in-depth analysis of the influence of spectral center wavelength location and strain distribution on the reflectance spectral properties, we propose the grating spectral reconstruction theory based on the spectral center wavelength location constraint and its improved genetic algorithm optimization method; realize the fast and accurate identification and rejection of the melancholy effect of fiber grating; propose the sensor numerical simulation optimization design method; develop the high sensitivity seepage pressure sensor, new strain sensor, target flow sensor, microdisplacement sensor, and multipoint displacement sensor; and build a large capacity, multi-parameter fiber grating real-time monitoring network.

Balloon-like angle and micro-displacement sensor based on bent single-mode fiber

In this paper, a simple balloon-like fiber sensing system based on a Mach-Zehnder modal interferometer by bending single-mode fiber (SMF) into a balloon-like structure is proposed, and the experiment proves that the system can be used for angle and micro-displacement measurement. The sensor system is only composed of SMF. Firstly, the transmission spectrum curves under different sensitive lengths and bending diameters are analyzed. It is found that the maximum extinction ratio of 24 dB can be achieved when the bending diameter of SMF is 8 mm. Then, by comparing the angle and micro-displacement sensitivity under different sensitivity lengths, it is found that the angle and micro-displacement sensitivity of balloon-like structures increase with the increase of sensitivity lengths. The angle measurement sensitivity is 253.1 pm/°, the detection range is −90° ∼ 90°, and the micro-displacement measurement sensitivity is 327.4 pm/μm. This sensor system has a great potential in the field of angle and micro-displacement measurement, and provides a new idea for angle and micro-displacement measurement.

Magnetoresistive micro-displacement sensor based on magnetorheological fluid

A novel magnetoresistance material based on magnetorheological fluid (MRF) was developed for applications in micro-displacement sensor. The MRF samples were fabricated by dispersing carbonyl iron particles (CIP) into a magnetic ion liquid (MIL) composed of 1-methylethyl ether-3-butylimidazole cation and [Fe2Cl7]− anions. The magnetoresistance characteristics were also systematically tested. It was found that the resistance value of MRF with a CIP content of 20 vol% decreased from 125 to 24.4 KΩ when increasing the magnetic field from 0 to 0.2 T. A sensor device was developed to study the displacement sensing characteristics of MRF, and found that the sensor had a high sensitivity of 0.1 Ω μm−1 and a high resolution of 10.0 μm. The excellent performance can be attributed to the low modulus and good stability of the MIL matrix, allowing for easy change of the resistance by controlling the magnetic field or displacement. In summary, these unique characters make the present MRF a promising magnetoresistance material with potential applications in displacement sensor.