Underwater mobile sensor node localization is a key enabling technology for several subsea missio... more Underwater mobile sensor node localization is a key enabling technology for several subsea missions. A novel scalable underwater localization scheme, called Best Suitable Localization Algorithm (BLSA), is proposed to dynamically fuse multiple position estimates of sensor nodes using fuzzy logic, aiming at improving localization accuracy and availability along the whole trajectory in missions. Numerical simulation has been conducted to demonstrate significant improvement in localization accuracy and availability by using the proposed fuzzy inference system. The proposed method provides a costeffective localization system by harnessing all available localization methods on-board.
Transactions of The Canadian Society for Mechanical Engineering, Sep 1, 2009
In this paper, we present experimental results of implementing five bilateral control schemes, wi... more In this paper, we present experimental results of implementing five bilateral control schemes, widely used for electro-mechanical systems, to a hydraulic actuator. The goal is to investigate the applicability of each control scheme to a hydraulic actuator and compare their performances on a common system. The considered schemes are 'force reflection', 'position error', 'shared compliant control', 'force reflection with passivity' and 'four channels architecture' schemes. The evaluation is conducted in terms of position tracking, force tracking, and fidelity of perceived stiffness by the operator. It is shown that force reflection and four channels architecture control schemes perform best in terms of both position tracking and force tracking during interaction with an environment emulated by different springs. Position error scheme, on the other hand, exhibits good position tracking capability, but cannot track environmental force encountered at the master site. It, however, produces a feel to the operator, based on position error between the slave and the master arms, which is potentially desirable during unconstrained motion control of the actuator.
In this paper, the effects of time delay and packet loss incurred in communication channel, are e... more In this paper, the effects of time delay and packet loss incurred in communication channel, are examined on the performance of bilaterally controlled hydraulic actuators under various control schemes. The controllers are force reflection (FR), position error (PE), combined force reflection and position error (FP), and four channels (FC). The performance of each control scheme is evaluated by performing a set of experiments on a test rig comprising haptic device, simulated valve-controlled hydraulic actuator, and communication channel. The performances are then compared using three criteria: position tracking, force tracking, and fidelity of the perceived stiffness. The experiments are performed under time delays ranging from 100 to 1,000 ms and percentage of packet losses up to 75%. It is shown that packet loss affects the signal oscillations, while time delay increases the steady-state tracking error. The FP controller shows the best performance with the least tracking error and signal oscillation in both position and force tracking. The FC scheme is shown to be least effective due to large tracking oscillations in the presence of packet loss and/or time delay. The value of stiffness perceived by the operator is found to decline with increasing time delays or packet losses in all controllers.
This paper proposes a sliding mode control with a disturbance estimation for an underwater robot.... more This paper proposes a sliding mode control with a disturbance estimation for an underwater robot. The mobility performance of an underwater robot is influenced by modeling error, observation noise, and several disturbances such as ocean current and tidal current. Therefore, a robust control system is needed for precise motion control of an underwater robot. This paper uses a sliding mode control, which is one of the robust control methods. In a sliding mode control, chattering tends to occur, if the switching gain is set to a high value. On the other hand, it is desirable to set the switching gain high from the viewpoint of robustness. Therefore, there is a trade-off between the switching gain and robustness. In the proposed method, the disturbance is estimated in real-time, and this estimated value is added to the control input. Most of the disturbances are compensated by this estimated value, and the sliding mode control is used for the rest of the disturbances. As a result, the robust control system is achieved by using the proposed method, even if the switching gain is set to a low value. The validity of the proposed method was confirmed from the simulation and experimental results.
Wireless Control of a Teleoperated Hydraulic Manipulator With Application Towards Live-Line Maintenance
ABSTRACT This paper presents the procedure of establishing performance charts for effective utili... more ABSTRACT This paper presents the procedure of establishing performance charts for effective utilization of a teleoperated hydraulic manipulator working under wireless communication channels. A teleoperated system, comprising a master haptic device and an industrial hydraulic manipulator, is constructed. The master and slave communicate through a communication channel emulated using the NS2 simulator. Two sets of experiments are designed to construct performance charts that guide us to select appropriate parameters of wireless network setup by which a particular value of position error appears at the slave hydraulic manipulator end-effector. The network parameters are: configuration of environment obstruction, transmission power of the router, and distance between the master and slave sites. The first set of experiments is conducted to define three regions of tracking quality, and to construct the performance charts. The second set of experiments confirms satisfactory performance, when the teleoperated system is located within the recommended regions in the established charts. One application of this study is live-line maintenance using remotely-operated hydraulic manipulators.
Artificial intelligence has significantly enhanced the research paradigm and spectrum with a subs... more Artificial intelligence has significantly enhanced the research paradigm and spectrum with a substantiated promise of continuous applicability in the real world domain. Artificial intelligence, the driving force of the current technological revolution, has been used in many frontiers, including education, security, gaming, finance, robotics, autonomous systems, entertainment, and most importantly the healthcare sector. With the rise of the COVID-19 pandemic, several prediction and detection methods using artificial intelligence have been employed to understand, forecast, handle, and curtail the ensuing threats. In this study, the most recent related publications, methodologies and medical reports were investigated with the purpose of studying artificial intelligence’s role in the pandemic. This study presents a comprehensive review of artificial intelligence with specific attention to machine learning, deep learning, image processing, object detection, image segmentation, and few-sh...
The absence of Global Positioning System in underwater environment predominates in the challenges... more The absence of Global Positioning System in underwater environment predominates in the challenges of underwater vehicles navigation or sensor nodes tracking. Localization of single or few underwater vehicles has been fostered in recent years. However, online simultaneous tracking of large-scale mobile sensor network is still a very challenging research area due to the high cost and the very limited number of vehicles that can be simultaneously localized using Ultra-Short Base Line (USBL) system. We propose a confidence-based localization algorithm for large-scale underwater mobile sensor networks that employs high precision localized sensor nodes in neighboring sensor nodes localization. Numerical simulation shows that a swarm of 100 sensor nodes can be tracked using a single USBL system, range measurement sensors and communication modems.
Fibre Bragg Grating (FBG) is a key technology for condition monitoring of different offshore oil ... more Fibre Bragg Grating (FBG) is a key technology for condition monitoring of different offshore oil and gas structures. FBG sensors are used to sense different physical parameters such as strain, temperature, vibration, etc. This paper investigates the effect of FBG sensor positions on the reflected sensing signal, to optimise the sensor positioning plan for structural health monitoring of offshore structures. Theoretical investigations were carried out on a cantilever beam to analyze the strain effects. Effect of different cantilever beam shapes, materials and their thickness on strain was investigated. Theoretical studies were also carried out to evaluate the strain sensitivities of FBG sensors. Furthermore, micrometer displacement based strain analysis of cantilever beam was carried out using FBG sensors and electrical strain gauges to study the positional influence and compared it with the theoretical results obtained.
2020 27th IEEE International Conference on Electronics, Circuits and Systems (ICECS), 2020
A low-complexity wavelet-based visual saliency model to predict the regions of human eye fixation... more A low-complexity wavelet-based visual saliency model to predict the regions of human eye fixations in images using low-level features is proposed. Unlike the existing wavelet-based saliency detection models, the proposed model requires only two channels - luminance (Y) and chrominance (Cr) in YCbCr colour space for saliency computation. These two channels are decomposed to their lowest resolution using Discrete Wavelet Transform (DWT) to extract local contrast features at multiple scales. These features are integrated at multiple levels using 2D entropy based combination scheme to derive a combined map. The combined map is normalised and enhanced using natural logarithm transformation to derive a final saliency map. The experimental results show that the proposed model has achieved better prediction accuracy with significant complexity reduction compared to the existing benchmark models over two large public image datasets.
2017 IEEE International Conference on Real-time Computing and Robotics (RCAR), 2017
This paper presents a heterogeneous computing framework to interface single board computers (SBC)... more This paper presents a heterogeneous computing framework to interface single board computers (SBC) to (i) distinct type of computing nodes, (ii) distinct operating systems, and (iii) distinct software applications for aeronautical surveillance system for drone delivery. The implementation platform selected is the Beagle Bone Black (BBB) having the operating system (OS) Linux Ubuntu 14. The computing nodes the BBB interfaces to are: (i) a personal laptop (MacBook Pro), (ii) a virtual machine, and (iii) two servers with distinct OSs. The software applications the BBB interfaces to are: (i) Gqrx, (ii) GNURadio, (iii) Google Earth, (iv) systems took kit (STK), and (v) Matlab. This heterogeneous computing framework, with the potential for incorporating specialized processing and networking capabilities, allows scalability for system integration to existing surveillance system for manned aircrafts. The proposed system successfully decodes the location of aircraft in real-time.
Numerical study of pipeline leak detection for gas-liquid stratified flow
Journal of Natural Gas Science and Engineering, 2021
Abstract Multiphase flows are of paramount importance in the oil and gas industry, considering th... more Abstract Multiphase flows are of paramount importance in the oil and gas industry, considering that most petroleum industries produce and transport oil and gas simultaneously. However, systematic research on pipeline leakage conveying more than one phase at a time is lacking attention. In this work, a numerical method is proposed to investigate the effect of two-phase gas-liquid leak flow behaviour in a subsea natural gas pipeline. The results of the simulations have been validated against the latest experimental and numerical data reported in the literature, and a good agreement has been obtained. The effect of leak sizes, longitudinal leak locations, multiple leakages and axial leak positions on the pressure gradient, flow rate and volume fractions in the pipeline were systematically investigated. The results show that the flow field parameters provide pertinent indicators in pipeline leakage detection. In particular, the upstream pipeline pressure could serve as a critical indicator for detecting leakage even if the leak size is small. Whereas, the downstream flow rate is a dominant leakage indicator if the flow rate monitoring is chosen for leak detection. The results also reveal that when two leaks with different sizes co-occur in a single pipe, detecting the small leak becomes difficult if its size is below 25% of the large leak size. However, in the event of a double leak with equal sizes, the leak closer to the pipe upstream is easier to detect.
This article proposes a holistic localisation framework for underwater robotic swarms to dynamica... more This article proposes a holistic localisation framework for underwater robotic swarms to dynamically fuse multiple position estimates of an autonomous underwater vehicle while using fuzzy decision support system. A number of underwater localisation methods have been proposed in the literature for wireless sensor networks. The proposed navigation framework harnesses the established localisation methods in order to provide navigation aids in the absence of acoustic exteroceptive sensors navigation aid (i.e., ultra-short base line) and it can be extended to accommodate newly developed localisation methods by expanding the fuzzy rule base. Simplicity, flexibility, and scalability are the main three advantages that are inherent in the proposed localisation framework when compared to other traditional and commonly adopted underwater localisation methods, such as the Extended Kalman Filter. A physics-based simulation platform that considers environment’s hydrodynamics, industrial grade ine...
Multi-objective optimization of confidence-based localization in large-scale underwater robotic s... more Multi-objective optimization of confidence-based localization in large-scale underwater robotic swarms. 2018 SABRA, A., FUNG, W.-K. and CHURN, P. 2018. Multi-objective optimization of confidence-based localization in large-scale underwater robotic swarms.
A new PD-like control law is proposed in this paper to control a multistable impacting system. Th... more A new PD-like control law is proposed in this paper to control a multistable impacting system. This control law can switch the system from a current, undesired state to a desired one by using the differences of the displacement and velocity between the current and desired states. The control law can control the multistable system without affecting its original dynamics, and its stability is proved by using the Lyapunov direct method. Numerical results are compared with the results obtained by using the intermittent control studied in [1]. The proposed PD-like control shows a better performance in terms of the smoothness of its control signal, which is easier to be implemented in practical applications.
Pipelines are widely used for the transportation of hydrocarbon fluids over millions of miles all... more Pipelines are widely used for the transportation of hydrocarbon fluids over millions of miles all over the world. The structures of the pipelines are designed to withstand several environmental loading conditions to ensure safe and reliable distribution from point of production to the shore or distribution depot. However, leaks in pipeline networks are one of the major causes of innumerable losses in pipeline operators and nature. Incidents of pipeline failure can result in serious ecological disasters, human casualties and financial loss. In order to avoid such menace and maintain safe and reliable pipeline infrastructure, substantial research efforts have been devoted to implementing pipeline leak detection and localisation using different approaches. This paper discusses pipeline leakage detection technologies and summarises the state-of-the-art achievements. Different leakage detection and localisation in pipeline systems are reviewed and their strengths and weaknesses are highl...
Pipelines are widely used for transportation of hydrocarbon fluids over millions of miles over th... more Pipelines are widely used for transportation of hydrocarbon fluids over millions of miles over the world. The structures of the pipelines are designed to withstand several environmental loading conditions to ensure safe and reliable distribution from point of production to the shore or distributions deport. However, leaks in pipeline networks are one of the major causes of innumerable losses in pipeline operators and nature. Incidents of pipeline failure can result in serious ecological disasters, human casualties and financial loss. In order to avoid such menace and maintain safe and reliable pipeline infrastructure, substantial research efforts have been devoted to implementing pipeline leak detection and localisation using different approaches. This paper discusses on pipelines leakage detection technologies and summarises the state-of-the-art achievements. Different leakage detection and localisation in pipeline systems are reviewed and their strengths and weaknesses are highlig...
IOP Conference Series: Materials Science and Engineering, 2017
Photonic Crystal Fibres (PCFs) developed using nanostructured composite materials provides specia... more Photonic Crystal Fibres (PCFs) developed using nanostructured composite materials provides special optical properties which can revolutionise current optical sensing technologies. The modal and propagation characteristics of the PCF can be tailored by altering their geometrical parameters and material infiltrations. A drawback of commercially available PCF is their limited operating wavelengths, which is mostly in the infrared (IR) spectral band. Nanostructured composite materials manipulates the optical properties of the PCF, facilitating their operation in the higher sensitivity near infrared (NIR) wavelength regime. Hence, there arises a need to closely investigate the effect of nanostructure and composite materials on various optical parameters of the PCF sensor. This paper presents a hexagonal PCF designed using COMSOL MULTIPHYSICS 5.1 software, with a nanostructured core and microstructured cladding. Propagation characteristics like confinement loss and mode field diameter (MFD) are investigated and compared with various geometrical parameters like core diameter, cladding hole diameter, pitch, etc. Theoretical study revealed that a nanostructured PCF experiences reduced confinement losses and also improved mode field diameter. Furthermore, studies are also carried out by infiltrating the cladding holes with composite materials (liquid crystal and glass). These simulations helped in analysing the effect of different liquid crystal materials on PCF bandwidth and spectral positions.
Photonic crystal fibers (PCFs) developed using nanostructured composite materials provide special... more Photonic crystal fibers (PCFs) developed using nanostructured composite materials provide special optical properties. PCF light propagation and modal characteristics can be tailored by modifying their structural and material parameters. Structuring and infusion of liquid crystal materials enhances the capabilities of all silica PCFs, facilitating their operation in different spectral regimes. The wavelength tunability feature of nanostructured PCFs can be utilized for many advanced sensing applications. This paper discusses a new approach to modify the optical properties of PCFs by periodic nanostructuring and composite material (liquid crystal-silica) infiltration. PCF characteristics like confinement wavelength, confinement loss, mode field diameter (MFD) and bandwidth are investigated by varying the structural parameters and material infiltrations. Theoretical study revealed that composite material infusion resulted in a spectral band shift accompanied by an improvement in PCF bandwidth. Moreover, nanostructured PCFs also achieved reduced confinement losses and improved MFD which is very important in long-distance remote sensing applications.
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Papers by Wai-keung Fung