Browsing by Author "Ghorbel, Fathi Hassan"

Now showing 1 - 10 of 10
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    Autonomous robotic crawler for in-pipe inspection
    (2007-02-27) Ghorbel, Fathi Hassan; Dabney, James Bruster; Rice University; University of Houston Clear Lake; United States Patent and Trademark Office
    The specification discloses a robot for inspection adapted to travel virtually unlimited distances through small-diameter enclosed spaces such as conduits or ducts, preferably using a fluid-driven screw-drive propulsion system. The robot preferably includes a plurality of wheels inclined at an angle greater than zero degrees and less than ninety degrees to the longitudinal axis of the pipe, a plurality of wheels aligned parallel to the longitudinal axis of the pipe, and a power system for causing relative rotation of the sections bearing the pitched and non-pitched wheels. The robot may include internal fluid flow passages, notched wheels, multiple retractable wheels, and is configured so as to have an operating diameter less than six and preferably less than two inches.
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    Closed-loop compensation for kinematic error in harmonic driver for precision control applications
    (2002-10-01) Ghorbel, Fathi Hassan; Ghandi, Prasanna S.; Rice University; United States Patent and Trademark Office
    Nonlinear control algorithms to compensate for kinematic error in harmonic drives provide a solid basis to improve their performance of harmonic drives in precision positioning applications. The present closed loop control algorithms compensate for kinematic error irrespective of its form in both set-point and trajectory tracking applications.
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    Hall Effect and Magneto Optical MFL Sensing
    (2013-11-19) Jallouli, Wissem; Ghorbel, Fathi Hassan; O'Malley, Marcia K.; Clark, John W., Jr.; Sarmad, Adnan
    The need for a reliable sensing tool has stimulated countless researchers to develop techniques trying to extract maximum information. In the field of nondestructive testing (NDT), various sensors have been established to fulfill that function. Examples include the ultrasonic, eddy current, and magnetic flux leakage (MFL) based techniques. Because they are extremely reliable, MFL based techniques represent one of the best inspection technologies. These technologies have numerous applications in diverse domains, including petroleum pipeline and tank inspections, airplane inspections, and production quality control. In this work, we will present two technologies based on MFL technique. The first is the Hall Effect sensor. This device has been extensively developed during the last century, especially after the use of integrated circuit technology. Its reliable results even under extreme conditions made it an extremely useful tool. The second technology is Magneto Optical Imaging. This technique rose very recently, and scientists hold high expectations about its performance once proper techniques are developed. The study of these two sensing devices gives a better understanding of the MFL technique by allowing us to investigate the potential of each technology, experience each in studied conditions to derive its characteristics, and discuss its performance.
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    Localization of a swimming robot in a cylindrical above-ground tank
    (2013-11-19) Megdiche, Islem; Ghorbel, Fathi Hassan; Clark, John W., Jr.; O'Malley, Marcia K.; Dabney, James B.
    Hazardous liquid storage tanks are subjected to damages and failures. These tanks need to be inspected for risks of damage and collapse. Many robotic systems have been developed for the technical inspection of these tanks replacing manual inspection based on the classical non destructive techniques. The use of robots in the field still an open research problem. Several related issues are not well studied - for example, the navigation of the robot autonomously within the tank which requires the determination of the robot position and the mapping of the environment. This dissertation addresses the localization problem of the robot using a systematic approach. First, an overview of the sensors used for the localization of Autonomous Underwater Vehicle is done. This overview leads us to choose the appropriate sensors for the robot in oil tank. This dissertation also presents an error analysis study to choose the appropriate number of sensors. Finally, it addresses the implementation issues of these sensors through several experimental studies.
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    Magnetic Flux Leakage Sensing: Modeling & Experiments
    (2015-07-20) Trevino Garcia, David A; Ghorbel, Fathi Hassan; Dick, Andrew J; Clark, John W; O'Malley, Marcia; Dutta, Sushant
    Nondestructive evaluation (NDE) is the inspection of samples for physical defects without altering the sample in question in any aspect. Magnetic Flux Leakage (MFL) has become one of the most widely used NDE techniques in robotic inspection of energy pipelines to prevent catastrophic failures. The MFL technique uses a magnetic field to magnetize ferromagnetic materials and correlates anomalies in the uniform field level to defects in the structure. Defect detection using the MFL technique is a mature area of work. However, defect characterization is an open research problem that can be decomposed into the Forward and Inverse Problems. The first problem deals with the characterization of the MFL signal for known defect shapes and dimensions, while the second one deals with the characterization of the defect shape from a known MFL signal. Several aspects of the MFL technique are not well understood yet, like the interplay of the MFL field for 3-dimensional defects. Another aspect that is not clear yet is the spatial properties of the MFL field components produced by complex 3-dimensional defect shapes. This dissertation addresses three issues identified with the MFL Forward Problem. An analytical 3-dimensional MFL model based on the Magnetic Dipole Model (MDM) and derived from Maxwell’s equations is presented. Under specific conditions, the magnetic field generated by a surface-breaking defect can be mathematically described as if it is caused by magnetic charges on the surface of the defect; such phenomenon can be described through Maxwell’s equations. The improved MDM characterizes the magnetic charges on the surface of the defect by using two parameters instead of one. Consequently, the MFL Forward Problem of complex defect shapes can be solved through the application of the improved model. Likewise, this thesis also studies the nature of the MFL signals in order to have a deep understanding of the Forward Problem. Therefore, a study of the correlation between the MFL signals (axial, radial, and tangential) through the improved MDM is addressed. The analysis exhibits the existence of a correlation between the three components of the MFL signal under some conditions. These results open more avenues in the field to better understand the physics of the MFL phenomenon. Hence, a methodology for the approximation of the behaviors of two MFL signal components from one extracted component is addressed. Additionally, another important approach to the MFL Forward Problem is conducted through experimentation. This dissertation explores a revolutionary 2-D type of sensing technology for application to MFL inspection known as Magneto Optical (MO) film. The feasibility of using the MO sensing in the MFL technique is presented through the development of an analytical model. Experimental and simulation validations are presented for the three approaches related to the MFL Forward Problem. Finally, this dissertation discusses the impact that these different contributions make toward solving the Inverse Problem.
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    Magnetic Flux Leakage System for External Robotic Inspection of Oil and Gas Pipelines
    (2015-04-24) Ben Moallem, Issam; Ghorbel, Fathi Hassan; Dick, Andrew J.; Stanciulescu, Ilinca
    Pipelines transport invaluable energy resources such as crude oil and natural gas over long distances. The integrity of the piping system in terms of safety of the process is then of high importance. However, pipes are prone by time to defects that may degrade their properties and lead to failures. Particularly, wall thinning is a serious anomaly that threatens aging pipelines. Therefore, their inspection plays a critical role to prevent the collapse of the system. Magnetic Flux Leakage (MFL) is by far the most effective technique of nondestructive evaluation for robotic diagnosis of ferromagnetic pipes. This work follows a novel approach to control such problem and assess the condition of the pipe by measuring with a good precision the wall radial thickness based on calibrated curves of reference and using an MFL diagnostic system tool. The proposed technique is generic and can be applied systematically for pipes with different sizes and material properties. It represents an advancement over the current conventional practices which require multiple physical experiments to generate empirical reference curves. Such procedures are cumbersome, time consuming and in consequence costly. The MFL sensing tool will be placed at the end-effector of a mobile robot platform devoted for external pipe inspection in a desert environment. It is based on permanent magnets producing a strong magnetic field that locally magnetizes and saturates the sample in question. At areas where there is metal loss, the magnetic flux flowing in the pipe leaks from the wall, which is detected by a Hall effect sensor and compared to the reference curve to estimate the wall thickness.
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    Measurement of pipe wall thickness using magnetic flux leakage signals
    (2012-03-13) Dutta, Sushant Madhukul; Ghorbel, Fathi Hassan; Rice University; United States Patent and Trademark Office
    An apparatus comprising a processor configured to implement a method comprising obtaining a pipe profile comprising a diameter, a nominal thickness, and a material, receiving a magnetic flux leakage (MFL) indication for a pipe associated with the pipe profile, and determining a wall thickness for the pipe using the pipe profile and the MFL indication. Also disclosed is a method comprising modeling an apparatus comprising a magnet configured to induce a magnetic field in a pipe, and determining a wall thickness measurement (WTM) for the pipe using a model of the apparatus and the pipe, a detected MFL signal, and a simulated MFL signal.
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    Modeling and Analysis of an In-line Pump Jet Thruster for Swimming Robots
    (2015-04-24) Kirmizi, Mehmet; Ghorbel, Fathi Hassan; Akin, John E.; Dick, Andrew J
    Nowadays, underwater robots play a significant role in many aspects of industry such as mine hunting, sea floor mapping, sub-sea pipeline construction and pipe surveys. Ever increasing demand on better control systems of underwater robots ignites engineers on modeling the systems for perfection. Since they are the lowest chain of the control problem, yet the most important ones. Thrusters are the most crucial parts of the underwater robot actuation. The need for maneuvering precision, for small and fast dynamic positioning, for precise motion and position control and for station keeping made developments of thruster modeling inevitable. The fundamental difficulty in modeling of a thruster is that axial flow velocity is an unmeasurable state, yet the model depends on that variable. This work addresses this difficulty. It explores the dynamics of in-line pump jet thrusters which are used for underwater robotic actuation. This work uses impeller geometry characterization, fluid flow analysis through impeller blades and through pump jet, thrust modeling and DC motor modeling. The main contribution of this work is incorporation of axial flow velocity into thruster modeling in order to resolve the unmeasurable state problem, thanks to the dynamical properties of impeller geometry and flow conditions through impeller blades.
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    Modeling and Interpretation Magnetic Flux Leakage
    (2012) Trevino Garcia, David A.; Ghorbel, Fathi Hassan
    This work presents an analysis of Magnetic Flux Leakage (MFL) signal to better understand the forward problem and the physics contributing to the nature of the signals. The analysis of the MFL signal was done through the implementation of two mathematical models such as the Magnetic Dipole Model (MDM) and Finite Element Method (FEM). This thesis shows that MFL signals presents a similar behavior even if the defect's characteristics differ (length, shape and depth). Also, this thesis introduces a Wavelet Analysis (WA) as a tool for further characterization of the MFL signal. This study presents how WA can identify and expose specific characteristics of each defect's MFL signal, even though the signals of different defect shapes were very similar to each other. The main advantage of this work is that it can achieve without changing the current MFL technique, additional information of the defect can be extracted.
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    Optimization of Thruster Configuration for Swimming Robots
    (2015-02-26) Kharrat, Houssem; Ghorbel, Fathi Hassan; Dick, Andrew; Clark, John William
    This thesis presents a design method of thruster configuration for swimming robots. This method can be used to analyze and optimize a given set of thruster configurations using three mathematical indices of measure. These indices measure the maneuverability and efficiency performance of a thruster configuration. Two of the three indices are used during the maneuverability evaluation. The first one uses the Manipulability index to evaluate the overall maneuverability and the second uses the linear programming method to evaluate the directional maneuverability with respect to the principal axes of motion. The third index measures the efficiency performance. In addition to their use in analyzing and optimizing a thruster configuration, these indices are shown to be useful in imposing a force and torque distribution. At first a detailed thruster configuration modeling method is presented. Then, the indices of measure are defined and used to evaluate and analyze a set of thruster configurations. Finally a parametric optimization is performed.