Fiber Bragg Grating Pressure Sensor Research Articles

Membrane-based optical fiber Bragg grating pressure sensor for health monitoring of pile foundations

A fiber Bragg grating (FBG) pressure sensor is proposed, designed, and fabricated for lateral earth pressure sensing, in which the FBG sensor is mounted on a 3D printed trestle structure combined with a membrane. The applied pressure can cause a deformation on the membrane, and then this deformation applied on the trestle structure causes tensile strain on the FBG. The proposed sensor is functionalized as a high-sensitive pressure transducer capable of converting the pressure into strain on the FBG. Here, the performance of the proposed sensor is numerically and experimentally investigated. The results show that the pressure sensitivity at 30°C is 10.62 pm/kPa within a range of 0–0.6 MPa. Due to the thermal expansion of the structure, the pressure sensitivity coefficient decreases with the increase of temperature; however, the cross effect between the temperature and strain on the sensing sensitivity is investigated and can be eliminated. The fabricated sensor has advantages of high sensitivity, good stability, and high pressure resolution, so it has potential in the field of structural health monitoring.

Blast wave pressure measurement and analysis in air and granular media inside a shock tube using a fiber Bragg grating sensor.

In this work, we have demonstrated the use of a fiber Bragg grating (FBG) sensor to measure the pressure profile of blast waves generated inside a vertical shock tube (VST). An FBG pressure sensor probe has been designed and developed that can be incorporated into the wall of the VST. The VST facility is used to generate blast waves with decay times of the order of a few milliseconds to simulate explosive events. Pressure measurement experiments have been carried out at different incident blast wave peak pressures inside the VST. The FBG pressure sensor measurements are validated against a standard piezoelectric pressure transducer at an acquisition rate of 1MHz. The pressure signals of both sensors are found to match well with similar rise times and decay profiles. The validated FBG pressure sensor is then incorporated into a sand column mounted in the test section of the VST to measure the pressure profile of blast wave-induced stress waves in granular media. The FBG and piezoelectric pressure sensor data are compared using fast Fourier transform analysis and continuous wavelet transform. The feasibility of FBG sensors for blast pressure measurement under harsh conditions imposed inside shock tube environments is established.

Improved pressure sensitivity prediction of a rubber-based diaphragm FBG pressure sensor using theoretical model and finite element analysis

Rubber-based diaphragm fibre Bragg grating (FBG) pressure sensor has been widely reported for low pressure sensing with high pressure sensitivity. However, the types of adhesives use and bonding layer thickness always result in large discrepancy between predicted and experimental pressure sensitivity. To investigate this, the pressure sensitivity of the FBG pressure sensor was first calculated using theoretical modelling. The theoretical pressure sensitivity was calculated at 0.5273 nm/kPa. The theoretical modelling was then improved using finite element analysis (FEA). Adhesive strain transfer coefficient was introduced into the theoretical modelling. Experimental pressure sensitivities were obtained to verify the theoretical pressure sensitivity with and without improved method. Experimental pressure sensitivities were obtained to verify the theoretical pressure sensitivity, both with and without the implementation of an improved method. The results revealed a significant discrepancy of more than 78% when comparing the experimental pressure sensitivities with the initially calculated theoretical pressure sensitivity. The introduction of an adhesive strain transfer coefficient has improved the theoretical pressure sensitivity reducing the discrepancy to within 10%. In addition, the results demonstrated that cyanoacrylate adhesive with minimal possible thickness is the best option for achieving the highest achievable pressure sensitivity.

Temperature interference in improved FBG pressure sensor for towing tank test

Because of EEDI regulations for ships and SDGs, it is of vital importance to develop ships with good propulsion performance, not only in still water, but also in waves. To predict the propulsion and seakeeping performance in waves, and in particular ship motions and added resistance, various theoretical calculation methods and CFD codes have been developed. To validate these estimation methods, experimental data on details of the flow induced by the ship disturbance are required. To meet this demand, the authors developed an innovative method for measuring and analyzing the spatial pressure distribution over the ship-hull surface using a large number of Fiber Bragg Grating (FBG) pressure sensors. However, pressure measurements with the conventional FBG pressure sensors are largely influenced by the difference in the temperature between water and air, referred to as the temperature interference. To resolve this issue, the authors developed a new FBG pressure sensor that incorporates three improvements and is significantly less influenced by temperature interference. Its performance was confirmed through comparisons with measured pressures obtained using existing strain-type and conventional FBG pressure sensors. Furthermore, the effects of different materials used for manufacturing ship models on the pressure measurement were investigated experimentally in towing tank tests. Finally, an experimental study was conducted to determine which of the three improvements in the latest FBG pressure sensor is essential for reducing the temperature interference.

Fiber Bragg grating pressure sensors: a review

Fiber Bragg grating (FBG) pressure sensors have the potential to replace conventional voltage sensors due to their compact size, resistance to electromagnetic interference, excellent safety, distributed sensing, and numerous other intrinsic benefits. It is frequently employed in the domains of civil engineering, aerospace, and medicine. Our work examines two types of sensitized FBG pressure sensors, namely FBG pressure sensors with innately improved sensitivity and FBG pressure sensors with extrinsically increased sensitivity. Our work examines microstructured fiber Bragg grating pressure sensors and polymer fiber Bragg grating pressure sensors for FBG pressure sensors with innately heightened sensitivity. Our research examines metal-mechanical FBG pressure sensors and polymer-mechanical FBG pressure sensors for extrinsically sensitized FBG pressure sensors. This report also summarizes the benefits and drawbacks of various FBG pressure sensors and temperature compensation techniques. Finally, the future of FBG pressure sensors is examined.

Research on Hydraulic Support Attitude Monitoring Method Merging FBG Sensing Technology and AdaBoost Algorithm

The hydraulic support is the key equipment of surrounding rock support in a stope, and thus monitoring the attitude of the hydraulic support has an important guiding role in the support selection, operation control and rock pressure analysis of the working face. At present, attitude monitoring technology for hydraulic support mainly includes inertial measurement, contact measurement and visual measurement. Aiming at the technical defects of imperfect attitude perception models, incomplete perception parameters and the low decision-making ability of such systems, the fiber Bragg grating (FBG) pressure sensor and the FBG tilt sensor are developed independently by combining with FBG sensing theory. The pressure sensitivity of the FBG pressure sensor is 35.6 pm/MPa, and the angular sensitivity of the FBG tilt sensor is 31.3 pm/(°). Additionally, an information platform for FBG sensing monitoring for hydraulic support attitude is constructed based on. NET technology and C/S architecture. The information platform realizes real-time monitoring, data management, report management, production information management and data querying of hydraulic support attitude monitoring data. An AdaBoost neural network hydraulic support working resistance prediction model is established using MATLAB. The AdaBoost neural network algorithm successfully predicts the periodic pressure of the coal mining face by training with the sample data of the working resistance of the hydraulic support. The predicting accuracy is more than 95%.

Investigation of Strain-Temperature Cross-Sensitivity of FBG Strain Sensors Embedded Onto Different Substrates

The strain-temperature cross-sensitivity problem easily occurs in the engineering strain monitoring of the self-sensing embedded with fiber Bragg grating (FBG) sensors. In this work, a theoretical investigation of the strain-temperature cross-sensitivity has been performed using the temperature reference grating method. To experimentally observe and theoretically verify the problem, the substrate materials, the preloading technique, and the FBG initial central wavelength were taken as main parameters. And a series of sensitivity coefficients calibration tests and temperature compensation tests have been designed and carried out. It was found that when the FBG sensors were embedded on different substrates, their coefficients of the temperature sensitivity were significantly changed. Besides, the larger the coefficients of thermal expansion (CTE) of substrates were, the higher the temperature sensitivity coefficients would be. On the other hand, the effect of the preloading technique and FBG initial wavelength was negligible on both the strain monitoring and temperature compensation. In the case of similar substrates, we did not observe any difference between temperature sensitivity coefficients of the temperature compensation FBG with one free end or two free ends. The curves of the force along with temperature were almost overlapped with minor differences (less than 1%) gained by FBG sensors and pressure sensors, which verified the accuracy of the temperature compensation method. We suggest that this work can provide efficient solutions to the strain-temperature cross-sensitivity for engineering strain monitoring with the self-sensing element embedded with FBG sensors.

Enhanced sensitivity of bare FBG pressure sensor based on oval-shaped 3D printed structure

A bare Fiber Bragg Grating (FBG) pressure sensor based on an oval-shaped 3D printed structure was proposed and experimentally demonstrated in this study. The whole structure was housed in a well-controlled pressure chamber, and the FBG signals were recorded by an Optical Spectrum Analyzer (OSA). Strains of the oval-shaped structure were simulated numerically using Ansys to optimize its performance. When under pressure, deformation of this 3D printed structure leads to response of FBG sensor, and the experimental results showed that Bragg wavelength shift is linearly proportional to the change in pressure. The proposed sensor shows a good sensitivity of 6.834 nm/MPa, corresponding to 4.43 × 10-3 MPa−1 in the pressure range from 0 to 0.45 MPa. The sensor’s linear fit coefficient is also good, reaching a mean value of 98.57 % and the repeatability with negligible mean hysteresis error is ± 0.16 nm (equivalent to 2.3 %). The proposed pressure sensor has high potential to be used in related industrial applications and is highly customizable to meet the requirements of different pressure ranges.

Design of a Fiber Bragg Grating Pressure Sensor Based on a Metal Diaphragm and Lever Structure.

In this paper, a pressure sensor based on a metal diaphragm and lever structure is designed, the sensing principle and mechanical structure of this sensor are analyzed and simulated, and its sensitization effectiveness and temperature compensation are verified. The maximum deflections of metal diaphragms of different sizes and materials were compared, and it was found that the square beryllium bronze diaphragm with a thickness of 1 mm and a side length of 20 mm had good elastic properties. The influence of the FBG in different positions of the lever on the center wavelength is analyzed. The sensitivity of the bare FBG is markedly improved under the influence of the two structures of the square elastic diaphragm and the lever, with a typical pressure sensitivity of 3.35 nm/MPa at 3 mm to the left of the lever center. The purpose of temperature compensation is achieved by adding another FBG that measures the temperature, and the sensing sensitivity can be tuned by adjusting the position of the FBG. It can meet the detection needs of a small range and high sensitivity.

An FBG Pressure Sensor Based on Spring-Diaphragm Elastic Structure for Ultimate Pressure Detection

We demonstrate a fiber Bragg grating (FBG) pressure sensor based on a spring-diaphragm elastic structure (SDES) for measuring ultimate pressure. The spring-diaphragm elastic structure model can effectively prevent the fiber Bragg grating from being broken under large pressure situations. The geometrical parameters of the sensor are optimally optimized by analyzing the structure of the spring and the diaphragm. By analyzing the results based on the spring-diaphragm elastic structure, the pressure sensor is manufactured and experimentally verified for extreme pressure conditions. For the first time, the fiber Bragg grating pressure sensor was operated at the ultimate pressure. The ultimate pressure experiment demonstrates a stable linear relationship between the fiber Bragg grating central wavelength and external pressure in the range of 0&#x2013;100 MPa, and the sensitivity of the pressure sensor is 79.7 pm/MPa with a linear correlation coefficient of 0.9998. In addition, the relative temperature sensitivity coefficients of the FBGs were obtained as <inline-formula> <tex-math notation="LaTeX">${K}_{P} =5.99 \times 10^{-6}/^{\circ }\text{C}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">${K}_{T} =6.265 \times 10^{-6}/^{\circ }\text{C}$ </tex-math></inline-formula> respectively to eliminate the temperature cross-sensitivity effect. The pressure sensor can be used for ultimate pressure detection, especially for deep sea detection, oil exploration, and chemical monitoring.

Design and Research on Variable Cross-section Cantilever Fiber Bragg Grating Pressure Sensor

Design and Research on Variable Cross-section Cantilever Fiber Bragg Grating Pressure Sensor

Design of Fiber Bragg Grating Pressure Sensor for Dynamic Track Weighing

Design of Fiber Bragg Grating Pressure Sensor for Dynamic Track Weighing

Diaphragm-type Fiber Bragg Grating Pressure Sensor with a Temperature Compensation Structure

Diaphragm-type Fiber Bragg Grating Pressure Sensor with a Temperature Compensation Structure

An Improved Temperature Compensation Method for Fiber Bragg Grating Pressure Sensor Based on Extreme Learning Machine

According to the problem of the sensor nonlinear changes occur at high temperatures, extreme learning machine model, is presented in this thesis the pressure sensitive grating and removing the temperature of the grating experiment data for training, establish a nonlinear model of wavelength, temperature, predict the experimental temperature, then the temperature data of pressure-sensitive grating the training set of training samples, the nonlinear model, temperature - wavelength prediction test set sample output wavelength, achieve the goal of improved temperature compensation method. The experimental results show that the algorithm can achieve a more ideal temperature compensation effect.

Pressure Membrane FBG Sensor Realized by 3D Technology.

The publication describes the design, production, and practical verification of an alternative pressure sensor suitable for measuring the pressure of gas, based on a combination of fiber-optic technology and 3D printing methods. The created sensor uses FBG (Fiber Bragg Grating) suitably implemented on a movable membrane. The sensor is equipped with a reference FBG to compensate for the effect of ambient temperature on the pressure measurement. The sensor is characterized by its immunity to EM interference, electrical passivity at the measuring point, small size, and resistance to moisture and corrosion. The FBG pressure sensor has a pressure sensitivity of 9.086 pm/mbar in the range from 0 to 9 mbar with a correlation coefficient of 0.9982. The pressure measurement in the specified range shows an average measurement error of 0.049 mbar and a reproducibility parameter of 0.0269 ± 0.0135 mbar.

Development of FBG pressure sensors using FDM technique for monitoring sleeping postures

There are various methods used in 3D printing technology for its molding, prototyping, and fabrication applications, but fused deposition modeling (FDM) is most famous for its customized uses. In this research work, fiber Bragg grating (FBG) based pressure sensors were fabricated by embedding FBG sensors through the FDM process and Polylactic Acid (PLA) raw material was used during the fabrication of the pressure sensor. These FBG pressure sensors were placed into the smart bed for monitoring the sleeping postures. The loading and unloading tests were conducted for validating this new FBG pressure sensor. The Calibration tests showed that the maximum applied load on the pressure sensor was categorized by a measurement pressure range of ±58−352 N and the measurement sensitivity of two FBG sensors was around 0.00053 nm/N and 0.0012 nm/N. It is found that the most significant error of the FBG sensor is 13.3 % carrying out the vertical load of 0.35 K N. The measured wavelength changes exhibit a step-by-step increase and decrease during the sleeping postures which also agrees with the calibration data, and the measurement sensitivity of both FBG sensors remained approximately 0.00315 nm/N and 0.008 nm/N. The absolute errors of the sensor were less than 4% against the applied load during sleeping postures. FMD process is a new alternative method for its fast and straightforward embedment of FBG sensors fabrication for numerous applications. It is also initiated that FBG sensors can be adequately protected with molten PLA raw materials without losing their sensing performance and damage which has the advantage of easily washing smart sensors.

Fiber Bragg Grating Pressure Sensor Integrated with Epoxy Diaphragm.

A fiber Bragg grating (FBG) sensor integrated with an epoxy diaphragm was developed for the measurement of pressure and water level. The bending strain of a circular diaphragm induced by uniform pressure was transferred to the FBG sensor. The response of the FBG sensor to the pressure was observed in terms of the Bragg wavelength shift which is linearly proportional to the strain. The effect of epoxy diaphragm thickness on the sensitivity and accuracy was investigated. The experimental results show that the sensitivity of FBG/epoxy diaphragm pressure sensor is decreasing with the increase of the diaphragm thickness. The sensitivities of the FBG pressure sensors with diaphragm thicknesses of 0.5 mm, 0.7 mm, and 1.0 mm were 175.5 pm/kPa, 89.5 pm/kPa, and 43.7 pm/kPa, respectively. The pressure measured by the proposed FBG sensor was compared with theoretical prediction and a close agreement was observed.

Sensitivity-Enhanced Fiber Bragg Grating Pressure Sensor Based on a Diaphragm and Hinge-Lever Structure

A high-sensitivity and small-size pressure sensor based on dual fiber Bragg grating (FBG), a diaphragm and hinge-lever structure is proposed. Its measurement principle is described and simulation analysis is conducted. We compensate for temperature cross-sensitivity by using an additional FBG to accurately measure the ambient temperature. Sensing experiments indicate that the pressure sensitivity is 5.227 pm/kPa within the range of 0-1.0 MPa, which is three times greater than that of a single-diaphragm pressure sensor without a flexible hinge lever. The sensor is suitable for accurate and stable pressure measurement in oil and gas pipelines and similar environments.

Highly sensitive FBG pressure sensor based on square diaphragm

A highly sensitive fiber Bragg grating (FBG) based square diaphragm pressure sensor has been designed and verified both in theory and experiment. The square diaphragm deflects due to the pressure difference generated at both sides of the square, and causes the compression along the axis of the pre-stretched FBG. The experimental results indicate that the pressure sensitivity of the proposed sensor reaches 3.402 pm/kPa in the range of 0–200 kPa with a higher coefficient of determination of 0.9985. Meanwhile, the sensor is found to present low hysteresis, good repeatability and resolution. Relative error recorded at 3.13 % represents that the effect of the temperature compensation is remarkable. Furthermore, the designed pressure sensor is simple, cost-effective and suitable for low pressure measurement.

Rotary Ventricular Assist Device Control With a Fiber Bragg Grating Pressure Sensor

Current ventricular assist devices (VADs) are rotary blood pumps used to treat end-stage heart failure. VADs are operated at a constant speed that is manually adjusted by a clinician based on the patient's cardiac demand during routine medical examinations. VADs operated at a constant speed have inadequate passive flow regulation due to the inherent mechanical pressure-flow characteristics of the pump; this can lead to harmful situations where the VAD is overpumping or underpumping. Typically, patients on long-term VAD support are discharged to an outpatient setting where the VAD speed can remain the same for weeks or months at a time, impacting patient safety and quality of life. Previously, physiological controllers for VADs have been proposed, which automatically adjust VAD speed to meet patient cardiac demand. Clinical implementation of physiological control is currently hindered by the lack of clinically available, implantable, and continuous hemodynamic sensors. This study describes the physiological control of a VAD using a fiber Bragg grating (FBG) sensor previously developed for measuring VAD inlet pressure. The FBG sensor was used as a feedback to a Starling-like physiological controller, and the control quality was compared against the same controller with feedback from a nonimplantable industrial pressure sensor (Omega sensor). Experiments were conducted in a bench-top cardiovascular simulator under various simulated patient scenarios. The average steady-state difference in VAD flow across all experiments was 0.1 L/min with a maximum difference of -0.4 L/min. Similarly, the average steady-state difference in left ventricular end-diastolic pressure was 0.02 mmHg with a maximum difference of -0.2 mmHg. The clinically insignificant differences found between the two feedback methods indicate that the FBG pressure sensor is viable for the physiological control of VADs.