Ph.D. Thesis Colloquium
DEPARTMENT OF INSTRUMENTATION AND APPLIED PHYSICS
Ph.D. Thesis Colloquium
NAME OF THE CANDIDATE : Mr. Om Prakash Parida
DEGREE : Ph.D.(ERP)
TITLE OF THE THESIS : Design, Development and Validation of High Performance
Fiber Bragg Grating Accelerometers”
SUPERVISORS : Prof. S. Asokan & Dr. Jaganath Naik (DRDO)
DATE & TIME : Monday, 10th February 2020 at 11:00 A.M.
VENUE : Lecture Hall – 1, Dept. of Instrumentation and Applied
Fiber Bragg grating (FBG) accelerometers have attracted the attention of researchers as an efficient and attractive alternative to conventional electrical accelerometers as they exploit the remarkable sensing capabilities of the FBG in combination with a varieties of novel mechanical sensor heads. The FBG being an intrinsic optical sensor that provides measurand information in wavelength encoded format makes the FBG accelerometers light, compact, less noisy, immune to electromagnetic interference, capable to sense efficiently in harsh environments, fit to carry out distributed sensing and highly sensitive. These remarkable and promising characteristics have generated a lot of interest to use the FBG accelerometers in various fields of science and technology like seismic vibration measurement, acceleration measurement for inertial navigation, structural health monitoring of medium to large scale civil, aerospace and defense structures. Though various types of FBG accelerometers are proposed by different researchers to achieve certain characteristic, there is a need to realize a high performance accelerometer which is not only highly sensitive but also provides temperature compensation along with reasonably good overall performance.
In order to achieve the objectives, the concept and configurations of a novel modular double-L cantilever based, a monolithic T-cantilever based and a composite triangular cantilever based FBG accelerometers are proposed. Mathematical models and designs are analyzed through numerical simulations using MATLAB and finite element method (FEM) simulations using ANSYS. Precise fabrication sequences are adopted for realizing the mechanical sensors heads (MSH) and the FBGs. The FBGs are carefully integrated with the MSHs in optical differential sensing configuration to realize the novel FBG accelerometers. The accelerometers are characterized for their static, dynamic and temperature characteristics. Close matching of the experimental results with the theoretical predictions proved the concepts and validated the designs.
For the double-L cantilever based FBG accelerometer (DLC-FBGA), sensitivity of 406.7 pm/g with a linearity of 99.86% over full scale range of ± 6 g, cross-axis sensitivity of 0.7% of in-axis sensitivity, natural frequency of 86 Hz with a usable bandwidth of 5-45 Hz and self-temperature compensation with an error of 0.016 pm/oC are achieved. For the monolithic T-cantilever based FBG accelerometer (MTC-FBGA), sensitivity of 821 pm/g with a linearity of 99.7% over full scale range of ± 4g, cross-axis sensitivity of 0.3% of in-axis sensitivity, natural frequency of 64 Hz with a usable bandwidth of 5-45 Hz and self-temperature compensation with an error of 0.07 pm/oC are achieved. For the composite triangular cantilever based FBG accelerometer (CTC-FBGA), very high sensitivity of 1721.6 pm/g with a linearity of 99.3%, cross-axis sensitivity of 0.7% of in-axis sensitivity, natural frequency of 23 Hz with a usable bandwidth up to 10 Hz are achieved. Its symmetrical and optical differential sensing configuration provides self-temperature compensation.
These highly sensitive self-temperature compensated high performance accelerometers can faithfully sense and measure low amplitude and low frequency vibrations as well as accelerations related to inertial navigation, seismic vibration and varieties of structural health monitoring applications. These designs also provide enough flexibility to further optimize the design parameters to achieve specific desired performance characteristics.
ALL ARE WELCOME
Date(s) - 10/02/2020
11:00 am - 12:15 pm
Lecture Hall-1, Dept. of Instrumentation & Applied Physics.
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