Low-Pressure Measurement using an Extrinsic Fiber-Based Fabry-Perot Interferometer for Industrial Applications

The development of an extrinsic fiber-based Fabry-Perot interferometer (EFFPI) for low-pressure measurement in the industry applications has been studied in this work. Monochromatic light from a laser diode with a wavelength of 1310 nm is operated as a source for illuminating the EFFPI sensor. A 30 mm diameter PVC pipe is utilized as a target, of which one end is sealed with a rubber balloon and the end is connected to the air pressure flow controlling system. Furthermore, the center point of the balloon is secured with a reflective thin film, which has a reflectance of ~55%. For the performance validation of the fiber sensor, a low-pressure range from 5 to 50 mBar is released onto the target. With 12 rounds repeatability, the experimental results reported that the average measured pressure values from the EFFPI sensor are 4.915 – 50.988 mBar. When compared to the reference instrument, the maximum and average errors in percentage terms are, however, 3.77% and 1.45%, respectively. In addition, results showed that the measured pressure value is directly proportional to the number of interference fringes, giving a sensitivity in the pressure measurement of the EFFPI sensor of 0.248 mBar/fringe

Fiber bragg grating-based system for 2-D analysis of vibrational modes of a steel propeller blade

This paper reports results obtained using fiber Bragg grating (FBG)-based sensors to investigate the displacement mode shapes of a cantilevered steel propeller blade, using FBG arrays for vibration monitoring for the first time. The experimental data obtained are cross compared with those from a finite element analysis of the same blade, undertaken using proprietary software. In the experimental configuration used, a network of gratings, forming a series of sensor arrays, was mounted on the blade under study to monitor its bending modes, while a further set was mounted perpendicular to this array to monitor torsional modes. To obtain the shape of the strain modes generated in the blade at specific frequencies, the dynamic response of the FBG arrays, as a function of time, was captured and then processed using Fourier transform algorithms to show the natural frequencies of the blade. As a result, the displacement modes shapes for the bending, torsional, and coupled modes of the first nine natural frequencies of the plate were obtained. The experimental data show very good agreement with theoretical analysis. This paper demonstrates the potential of using the lightweight, minimally invasive sensing technique described for the analysis of propeller blades and, thus, illustrating an effective method to overcome the deleterious effects of propellers seen in some commercial propeller designs

SUAS: A Novel Soft Underwater Artificial Skin with Capacitive Transducers and Hyperelastic Membrane

The paper presents physical modeling, design, simulations, and experimentation on a novel Soft Underwater Artificial Skin (SUAS) used as tactile sensor. The SUAS functions as an electrostatic capacitive sensor, and it is composed of a hyperelastic membrane used as external cover and oil inside it used to compensate the marine pressure. Simulation has been performed studying and modeling the behavior of the external interface of the SUAS in contact with external concentrated loads in marine environment. Experiments on the external and internal components of the SUAS have been done using two different conductive layers in oil. A first prototype has been realized using a 3D printer. The results of the paper underline how the soft materials permit better adhesion of the conductive layer to the transducers of the SUAS obtaining higher capacitance. The results here presented confirmed the first hypotheses presented in a last work and opened new ways in the large-scale underwater tactile sensor design and development. The investigations are performed in collaboration with a national Italian project named MARIS, regarding the possible extension to the underwater field of the technologies developed within the European project ROBOSKIN

Theoretical design and analysis of a sensing system for high pressure and temperature measurement in subsea underwater applications.

The theoretical design and analysis of a metal coated hybrid sensing system of Fibre Bragg Grating (FBG) and Extrinsic Fabry-Perot Interferometer (EFPI) cavity for high pressure high temperature (HPHT) measurement in subsea underwater applications is reported. The FBG and EFPI are used to measure temperature and pressure respectively. An opto-mechanical model that assesses the measurement of HPHT for subsea underwater applications with hybrid sensing system was developed. In this model, coating of the sensor with metallic materials is studied. The model combines both optical and structural analyses for developing an optimal sensor system design. The optical analysis is carried out to obtain the spectral response of the sensor while the structural analysis is used to obtain the change in optical properties of the sensor due to photo-elastic effect. Analytical results showed that the temperature sensitivity of the hybrid sensor with double layer metal coated FBG increased to 23.89 pm/ {deg}C when compared with single metal coated FBG of 13.95 pm/ {deg}C from previous study and the associated pressure range measured up to 5000 Psi. Furthermore, the proposed sensor design has shown good linearity. While the single coated FBG sensor shows little sensitivity, the sensitivity increases with thickness for double metal coating

Design and Fabrication of Liquid Pressure Sensor using FBG Sensor through Seesaw Hinge Mechanism

Pressure sensors are used in various industrial applications assisting in preventing unintended disasters. This paper presents the design and fabrication of a novel Seesaw device incorporating a diaphragm and Fiber Bragg Grating (FBG) sensor to measure the pressure of liquids. The designed sensor has been tested in a static water column. The proposed design enables the user to easily make and modify the diaphragm based on the required pressure range without interfering with the FBG sensor. The developed pressure sensor produces improved accuracy and sensitivity to applied liquid pressure in both low and high-pressure ranges without requiring sophisticated sensor construction. A finite element analysis has been performed on the diaphragm and on the entire structure at 10 bar pressure. The deformation of the diaphragm is comparable to theoretical deformation levels. A copper diaphragm with a thickness of 0.25 mm is used in the experiments. All experiments are performed in the elastic region of the diaphragm. The sensor’s sensitivity as 19.244 nm/MPa with the linearity of 99.64% is obtained based on the experiments. Also, the proposed sensor’s performance is compared with recently reported pressure sensors.publishedVersio

Scalable Tactile Sensing for an Omni-adaptive Soft Robot Finger

Robotic fingers made of soft material and compliant structures usually lead to superior adaptation when interacting with the unstructured physical environment. In this paper, we present an embedded sensing solution using optical fibers for an omni-adaptive soft robotic finger with exceptional adaptation in all directions. In particular, we managed to insert a pair of optical fibers inside the finger's structural cavity without interfering with its adaptive performance. The resultant integration is scalable as a versatile, low-cost, and moisture-proof solution for physically safe human-robot interaction. In addition, we experimented with our finger design for an object sorting task and identified sectional diameters of 94\% objects within the $\pm$6mm error and measured 80\% of the structural strains within $\pm$0.1mm/mm error. The proposed sensor design opens many doors in future applications of soft robotics for scalable and adaptive physical interactions in the unstructured environment.Comment: 8 pages, 6 figures, full-length version of a submission to IEEE RoboSoft 202