Abstract-In this paper, a one-dimensional numerical framework based on Finite-Difference TimeDomain (FDTD) method is developed to model response behaviour of Ground penetrating radar (GPR). The effects of electrical properties such as dielectric constant, conductivity of the media have been evaluated. A Gaussian shaped pulse is used as source which propagates through the 1D array grid, and the pulse interactions at different media interfaces have been investigated. The objective of this paper is to assess the modelling criteria and success rate of detecting buried object using the framework. A real life application of GPR to detect a buried steel bar in one meter thick concrete block has been carried out, and the results present successful detection of the steel bar along with measured depth of the concrete cover. The developed framework could be implemented to model multi-layer dielectric blocks with detection capability of various buried objects.
A miniaturized symmetrical dipole antenna with extra radiating arms is proposed for low frequency operation (100 MHz) in ground penetrating radar applications to achieve high depth penetration at low resolution. The dipole antenna design is of total dimension 66.5 cm × 22 cm. A parametric study of antenna performance is performed via simulation with Agilent Advanced Digital System software which indicates an optimum length of 15 cm for the extra arm with a gap of 5 cm between the dipole arm and extra arm. The results are validated experimentally in room conditions with a prototype antenna fabricated on 1.6 mm thick FRA substrate, copper layer thickness of 17 µm. The antenna operating at a centre frequency of 104 MHz and bandwidth of 8 MHz for VSWR ≤ 2 achieves a 55% reduction in length compared to a conventional dipole operating at 100 MHz while delivering typical dipole radiation pattern with directivity gain of 2.06 dBi.
Only a few attempts have been made to investigate the possibilities of developing chain climbing robot due to the complexity of the structure and physical nature of chain links. Mooring chains are subjected to large tidal waves, harsh environmental conditions and storms on a daily basis. Therefore, periodic inspection of the integrity of chain links is important. Work reported in this paper investigates the possibilities of mooring chain climbing by using tracked wheel locomotion. The permanent magnet adhesion, tracked wheel crawler robot developed for this purpose can climb on mooring chains both in air and underwater with a variable speed according to the inspection requirements (maximum speed of 42cm/minute). It is able to handle an external downward force of 50N during the climbing motion. Numerical modelling based analysis of a magnet adhesion module and the strength of the robot structure is validated with prototyping and testing of the concept.
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