Mohd Zafri Baharuddin

Development of in-pipe inspection robot: A review

This paper reviewed several previous papers on work that have been done on the development of in-pipe inspection robot for the last 20 years. By sorting the types of the inspection robots they can be divided into several groups according to their locomotion. Each prototype has its own advantages and disadvantages depending on its design requirements and purpose of inspection. The prototypes have been tested in several experiments in order to verify its functionality and efficiency of inspection task. Some of the researchers ran simulations to validate the kinematic and modeling the mechanism of their own prototype. Developing in-pipe inspection robot can overcome the issues of human factor in labour intensive or dangerous work and also to act in inaccessible environment during repair and maintaining inside the pipeline.

Determination of Auto-Recloser Location Using Cost Analysis in the Sabah Electricity Distribution Network

Sabah electricity (SESB) operates a vertically integrated electricity utility in East Malaysia. It is currently embarking on an initiative to improve the reliability of its 11 kV distribution network which is prone to trippings due to vegetation growth along their long spur lines, Apart from rentice management, another proposed solution is to install auto-reclosers (AR) at appropriate locations in their network. This work deals in developing a methodology to determine the most economic location of ARs and their numbers to be installed. In order to do that, data in the form of customer types, load levels and network topology were collected from site visits at SESB. The study then used an estimated value of lost load (VoLL) to quantify the financial losses that customers suffer given a loss of supply. These losses would then be summed with the cost of ARs for a particular AR placement scenario to form an objective function. The best placement and numbers of AR can be decided by determining the least cost option from the said objective function.

Application of Lightning Performance Analysis for a Tropical Climate Country

A tropical climate country experience high lightning related activities. This can be represented in terms of the keraunic level which lies within the region of 100 to 150 thunderstorm days per year. For a utility company, the high keraunic level would contribute to high possibility of power interruptions. These outages would ultimately lead to loss of revenue and reduced network reliability. These lightning related interruptions may be in terms of direct strikes to the line. Apart from that a consequent back flashover may result from an indirect lightning strike near the vicinity of the line. The aggregate of the direct and indirect lightning strikes would contribute to the overall lightning performance of the line. This paper outlines the application of a lightning performance analysis tool based upon the IEEE Std 1410-2004 conditioned for a tropical climate country. Results and analysis indicates factors that would affect the lightning performance of the line. The contributing factors found from these analyses would be dependent upon the environment at which the line is located, e.g. presence of tall objects which ultimately acts as a lightning shield would improve the lightning performance whereas if the lines are located in an open field, the probability of lightning strikes would be high. Based upon these factors, a list of possible mitigating actions is presented in improving the lightning performance of the line.

Development of circularly polarized synthetic aperture radar on-board UAV JX-1

ABSTRACT We developed L band (frequency 1.275 GHz) circularly polarized synthetic aperture radar (circularly polarized SAR) on-board unmanned aerial vehicle (UAV). This paper explains the configuration of system, antenna, and car-based experiment of circularly polarized SAR. The comparison of circularly polarized SAR and linearly polarized SAR by full polarimetric scattering experiment in anechoic chamber was done and discussed. The result shows circular polarization has less effect of orientation angle of target and could avoid the misalignment of transmitter and receiver antenna during UAV operation. Axial ratio and ellipticity images are also derived and introduced as novel classification technique in microwave remote sensing field using circularly polarized SAR or ellipticity characteristic of scattering wave.

Development of robotic boiler header inspection device

This paper discusses the development and actual site testing of an inspection robot designed for boiler header inspections in thermal power plants in Malaysia owned by Tenaga Nasional Berhad (TNB). The purpose of boiler headers are to tie up multiple boiler tubes together. Boiler headers are enclosed cylindrical pipes made of carbon steel, horizontal in nature, can range up to 25 m (from TNB database). These boiler headers are highly pressurized and high in temperature during operation, where the pressure goes up to a few bars and the temperature ranges between 500°C until 800°C. Due to the severe working conditions, these boiler headers are exposed to threats of possible failure due to corrosion, pitting and cracks. During outage, after acquiring approval from Department of Safety and Health (DOSH), a small cut is made on the entry point and a boiler header inspection robot (BHIR) is then deployed into the boiler header, carrying a fiber optic camera. BHIR is developed to visually inspect the inner wall of boiler headers and check for signs of failures. This paper discusses the limitations and requirements of the robot, the prototype and also the procedures for actual site testing. Lastly, the site testing results is explained.

The Development and Comparison of Two Polarimetric Calibration Techniques for Ground-Based Circularly Polarized Radar System

Two techniques are described for the calibration of ground-based (GB) circularly polarized (CP) full polarimetric radars. The techniques are based on the point target calibration approach that uses various types of canonical reflectors with different orientations. Specifically, the calibration methods for linearly polarized (LP) radar proposed by Wiesbeck et al. and Gau et al. are selected and adapted to CP with suitable reflectors. The applicability of the techniques is examined through C-band scatterometric and synthetic aperture radar (SAR) measurements in an anechoic chamber. For the scatterometric mode, comparisons of calibrated channel imbalances with theoretical values show agreement within ±0.3 dB in amplitude and ±5◦ in phase. The crosstalk between the channels is also reduced by ∼ 5 to 30 dB after calibration. For the SAR mode, calibrated scattering matrix of a vertical wire target exhibits significant elimination of distortions between channel amplitudes and phases. The effect of calibration on target parameter retrieval is also investigated through the Cloud-Pottier eigenvector-based decomposition. Both calibration techniques are shown to yield improved accuracy of entropy-alpha (H-ᾱ) distributions and orientation angle (β̄) values.

Analysis of Circular Polarization Backscattering and Target Decomposition Using GB-SAR

Currently, most full-polarimetric synthetic aperture radar (SAR) systems adopt linear polarization (LP). On the other hand, circular polarization (CP) is also becoming popular due to its various benefits over LP. However, since CP-SAR is an emerging technique, there are not many imaging and polarimetric analysis results in the literature. As a fundamental study on CP-SAR, this paper presents the results of an investigation on the CP properties of ground-based SAR (GB-SAR) echoes from various canonical targets and a rice paddy sample. The C-band data acquired in a laboratory environment are analyzed and interpreted by means of several factors such as calibration performance, experimental verification of theoretical scattering matrices, imaging quality and accuracy of scattering decomposition results. The eigenvector-based decomposition of the coherency matrix is adopted, and the performance of CP in retrieving the targets’ dominant scattering mechanisms and physical parameters is evaluated from entropy-alpha (H -ᾱ) plane and orientation angle (β̄) value. Results demonstrate the effectiveness of CP in interpreting and discriminating the SAR image features mainly owing to its distinct advantage of highly reliable received signal strength.

The polarimetric calibration method for ground-based circularly polarized synthetic aperture radar

A polarimetric calibration method for circularly polarized (CP) synthetic aperture radar (CP-SAR), where both transmitting and receiving antennas are CP, is proposed in this paper. The proposed CP polarimetric calibration method is based on a conventional polarimetric calibration method proposed by Wiesbeck et al. where only canonical targets are used. Experimental results applied with the proposed calibration method show improvement over uncalibrated measurements in radar cross-section (RCS), amplitude ratio and phase difference of between channel.

Axial ratio enhancement of equilateral triangular-ring slot antenna using coupled diagonal line slots

Wideband circularly polarized antenna is required for many satellite applications. Circularly polarized (CP) Equilateral Triangular-Ring Slot (ETRS) antenna has narrow 3-dB axial ratio bandwidth (ARBW) compared to its impedance bandwidth. Two diagonal line slots were introduced to ETRS for enhancing its 3-dB ARBW. The diagonal line slots were inserted on the left and right side of ETRS. Lengths of the left and right line slots correspond to the lowest and highest frequencies of ETRS antenna 3-dB ARBW, respectively. Both diagonal line slots have successfully improved 3-dB ARBW of ETRS antenna by achieving 680MHz or 37% fractional bandwidth. Measured results of x-z and y-z planes of radiation patterns also confirm that the antenna has bidirectional radiation and presents good CP performance within its 3-dB ARBW. ETRS antenna RHCP gain is also improved thanks to the diagonal line slots insertion.

Image Acquisition System for Boiler Header Inspection Robot

This paper aims to present development of an image acquisition in the task of power plant boiler header inspection. Among the content of this paper includes hardware selection and software selection and integration of both systems to form a complete image acquisition system. The real challenge behind the project is the miniature scale of the robot that will be used to carry the image acquisition system into the boiler header, since a boiler header entrance is normally only about 80 mm in diameter. Hardware system needs to be small enough to fit into the boiler header entrance. This paper also discusses the results from testing in Stesen Janakuasa Sultan Ismail, Paka as a verification of the workability of the designed system.