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Angle of arrival estimation system for radiation pattern reconfigurable antenna with modified gaussian membership function
No full textDoctor of Philosophy in Computer EngineeringThis research focuses on developing angle of arrival (AOA) estimation system
(AES) through incoming received signal strength indication (RSSI). Proposed AES is
developing on a single board computer (SBC) using an open source GNU Linux
operating system (OS). The good AOA estimation systems must able to covered 360°
with many estimation points. However, previous AOA estimation systems prototype
suffers from a major drawback to achieve 360° angle covered due to limitation of
antenna radiation pattern. Therefore, radiation pattern reconfigurable (RPR) antenna
operates at 2.45 GHz that capable to cover the wide AOA estimation angle is
introduced. Nevertheless, the RPR antenna on AES prototype provides lack of
estimation points. Thus, this thesis infuses Fuzzy Inference System (FIS) to further
improve decision making and increase the number of AOA estimation points. The FISAES
is the first effort in realizing the advantages of FIS with only three sets of RPR
antenna abilities without any intelligent algorithm support to cover 360° angle
estimation. The FIS-AES algorithm is develop by Python 2.7 programming supported
by SciKit library. The proposed Fuzzy Inference System of AOA estimation system
(FIS-AES) successfully increases number of estimation from nine to 18 estimation
points. Four types of membership function (MF) are trained to obtain response between
fuzzifier and defuzzfier of FIS-AES algorithm. A novel MF based Gaussian-MF curve
named as the Pattern-MF is introduced. The response between fuzzifier and defuzzfier
of FIS-AES algorithm of proposed Pattern-MF approximately ~80% to ~85%, which is
the highest compared than existed MF in SciKit library. Moreover, adopted the FIS
offers more AOA estimation points, thus it helps FIS-AES capable to improve the
absolute error of AOA estimation and root mean square error (RMSE) is ±5° and less
than 10 respectively. The investigation of SBC performance is important to verify that
SBC competent to act as the main platform of AES. The SBC performance is verified in
terms of CPU and memory utilization. In this work, the Raspberry-Pi has successfully
completed all tasking with average CPU and average memory utilization less than 10%
and less than 31% respectively for S11 measurement and less than 10% and less than
37% respectively for AES measurement. With all capabilities demonstrated and
discussed, the FIS-AES have great potential as one of the best options for realizing
applications such as localization system man computer interaction
Development of kaolin based geopolymer coating for lumber wood applications
No full textDoctor of Philosophy in Materials EngineeringThe use of ordinary Portland cement is evident for centuries now especially in civil industries. Lacking of greener option with equal or enhanced properties forced consumers to ignore the shortcomings of ordinary Portland cement. Investigation of kaolin based geopolymer coating was aimed to not only increase the productivity and applications of
geopolymer but also to potentially replace the use of ordinary Portland cement in terms
of coating technology. Initial aim for this study was to prepare an optimum geopolymer
coating paste made up of kaolin, as the aluminosilicate source and alkaline activator
solution. The optimum mix design was mainly judged by its mechanical strength,
followed by physical, phase analysis and scanning electron microscopy micrographs as
crucial parameters of sodium chloride concentration, solids-to-liquid (S/L) ratio and
alkaline activator ratio was studied. Kaolin, the geopolymer source material was
characterized by using particle size analysis, phase, chemical composition, and scanning
electron microscopy testing. Kaolin geopolymer paste with 8 M sodium hydroxide
molarity, solids-to-liquid (S/L) ratio of 0.9 and alkaline activator ratio of 0.40 cured at 70
°C for 24 hours, gave highest strength values of 2.4 MPa (7 days), 2.98 MPa (28 days)
and 4.56 MPa (90 days). This mix design also proven to have good workability, density,
semi crystalline phase, and homogeneous compacted geopolymer matrix through
morphology micrographs, in agreement to strength values. Continues improvement of
kaolin geopolymer paste over time showed promising potentials towards preparation of
kaolin based geopolymer coating. To the best of our knowledge, no attempts have been
made previously to produce kaolin based geopolymer coating for lumber wood
application, thus making it a novel work. The geopolymer paste were then coated on most
unlikely substrate to investigate the extent of its bonding capabilities. This was evidently
studied through bonding, physical, mechanical and morphological results. Optimum
kaolin geopolymer coating successfully adhered to lumber wood substrate and provided
high strength value of 4.3 MPa (7 days), 4.9 MPa (28 days) and 5.96 MPa (90 days).
Early mechanical strength of kaolin geopolymer coated lumber wood differs from
mechanical strength exhibited by kaolin geopolymer paste due to moisture absorption
into substrate as supported by interfacial layer micro images. Hardness value was in
agreement with flexural strength of kaolin geopolymer coated lumber wood and phase
analysis of kaolin geopolymer paste. Zeolite peak contributes to high early strength
development but disrupts geopolymer structure over time that leads to drop in strength
upon sample age. Investigation of sample over different time period is proven to be
important for long term usage of geopolymer coating. Ultimately, this study clearly
demonstrated the processing and feasibility of kaolin geopolymer coating material
Optimal control of the attitude maneuvering for Razaksat class satellite based on rigid and flexible model
No full textDoctor of Philosophy in Mechanical EngineeringThe increase in demand for performance for satellite capabilities has pushed the design of the system to be more and more power consuming. This is the case for RazakSAT-2, which is a new satellite program that will be equipped with bigger solar panel to generate sufficient power. Thus, this translates to a higher flexibility in the satellite. Satellite mission is known to be highly sensitive to the flexible motions and it is time constrained. Hence, understanding the behavior of the system is required to solve the time constrain flexibility problem. The Floating Reference Frame is applied to obtain the mathematical model of the system which consists of three solar panels. In addition, the model for the actuator is also developed for a four-reaction-wheel system and the Eigen-axis Quaternion Feedback control is also derived. The obtained model is simulated using the MATLAB and ANSYS software for verification of the model. The obtained Percentage Root Mean Square Error falls between 2.015% to 4.841% which is low. Hence, this signifies that the model is sufficient to describe the dynamic of the system. From the model, the control of the minimum time optimal control is developed to minimize the time to achieve desired orientation while minimizing the amplitude of the flexible solar panel. GPOPS toolbox is applied to obtain the optimal control solution. The optimal control is shown to decrease the maneuver time by 3.49% to 25.11% depending on the Eigen Axis of the rotation compared to the conventional Eigen-axis Quaternion Feedback controller. This phenomenon is contributed by two factors. Firstly, the optimal control is able to fully utilize the all the capacity of the reaction wheel while the Eigen-axis Quaternion Feedback controller is plagued by the pseudo-inverse limitation which allows a maximum 35% increases in performance. Secondly, the application of optimal control allows the trajectory to deviate from the effective Eigen axis to achieve faster maneuver by utilizing the torque that is unavailable to the effective Eigen axis maneuver. In terms of the performance of the rigid and flexible model in the optimal control, it shown that the flexible motion converges at 10.53% faster for the flexible model. The primary factor that affects the maneuver time is the natural frequency of the system. The effect of the natural frequency is observed in this section and is shown that maneuver times increase when the natural frequency decreases. For future works, additional parameters such as the stiffening effect, external disturbances and the imbalance mass distribution on the rigid and flexible due to the deflection are studied. This can contribute to a more refined flexible model that would further increase the accuracy of the model
