Browsing by Author "Chan, C. W."

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A procedure for power consumption estimation of multi-rotor unmanned aerial vehicle
(2020-01-01)
Chan, C. W.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
Unmanned aerial vehicles (UAVs) have the potential to find many commercial applications, which may require relatively long mission times. Therefore, it is important to make UAVs that can complete the mission in an efficient and power saving way. To achieve a prescribed flight mission, a UAV has to perform a number of maneuvers/movements, which will consume a certain amount of power. To maximize the cruising time, not only the power source is able to provide enough amount of power to the UAV but also the parts of the UAV can perform efficiently to save power. Before the minimum power capacity can be determined, it is required that the power consumptions of the UAV parts for the required mission be evaluated in a proper way. In this paper, a procedure is presented to estimate the power consumption of a composite UAV. The configuration as well as the fabrication of the UAV using truss-type parts made of carbon strand/epoxy composite material will be briefly introduced. The power consumptions of the propeller system and electric parts will be evaluated in a systematic way. Experiments were conducted to verify the theoretical predictions. Flight tests were also performed to study the power consumption of the UAV and the suitability of the proposed procedure for power consumption calculation.
VIBRATION ANALYSES OF CRACKED PLATES BY THE RITZ METHOD WITH MOVING LEAST-SQUARES INTERPOLATION FUNCTIONS
(2014-03-01)
Huang, C. S.
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Chan, C. W.
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土木工程學系
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Department of Civil Engineering
The solutions for the vibrations of cracked thin plates are obtained by the Ritz method with admissible functions. Based on the classical plate theory, the basis functions comprising polynomials and crack functions are adopted to generate the admissible functions by the moving least-squares approach for a set of nodes randomly distributed in the domain. The crack functions account for the singular behaviors of stress resultants at crack tip(s), which are discontinuous in displacement and slope across the crack. The present solutions are validated through convergence tests of frequencies and by comparison with the published results for simply-supported cracked rectangular plates. The solutions are further employed to determine the natural frequencies of cantilevered skewed rhombic and isosceles triangular plates and completely free circular plates, each with a crack of varying length, location and orientation. The numerical results are tabulated and some corresponding mode shapes are also presented, by means of nodal patterns. Most of the results shown here are new to the literature.
Vibrations of rectangular plates with internal cracks or slits
(2011-06-01)
Huang, C. S.
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Leissa, A. W.
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Chan, C. W.
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土木工程學系
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Department of Civil Engineering
This work applies the famous Ritz method to analyze the free vibrations of rectangular plates with internal cracks or slits. To retain the important and useful feature of the Ritz method providing the upper bounds on exact natural frequencies, the paper proposes a new set of admissible functions that are able to properly describe the stress singularity behaviors near the tips of the crack and meet the discontinuous behaviors of the exact solutions across the crack. The validity of the proposed set of functions is confirmed through comprehensive convergence studies on the frequencies of simply supported square plates with horizontal center cracks having different lengths. The convergent frequencies show excellent agreement with published accurate results obtained by an integration equation technique, and are more accurate than those obtained by a previously published approach using the Ritz method combined with a domain decomposition technique. Finally, the present solution is employed to obtain accurate natural frequencies and mode shapes for simply supported and completely free square plates with internal cracks having various locations, lengths, and angular orientations. Most of the configurations considered here have not been analyzed in the previously published literature. The present results are novel, and are the first published vibration data for completely free rectangular plates with internal cracks and for plates with internal cracks, which are not parallel to the boundaries. (C) 2011 Elsevier Ltd. All rights reserved.