Author

Wonchang Choi

Department of Architectural Engineering, Gachon University, Seongnamsi, Korea

7 articles in our journals

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Research ArticleOpen accessFeedback Control of Quad-Rotors with a Matlab-Based SimulatorStephen Armah, Sun Yi, Wonchang Choi, Dongchul ShinPrecise regulation of position and attitude (roll, pitch and yaw) is one of the most critical tasks to be considered in designing controllers for quadrotor types of Unmanned Aerial Vehicles (UAVs). The MATLAB-based simulator for quadrotors using PD-feedback control to achieve stabilization was developed. MATLAB/Simulink models are used to design and validate the control algorithms and the simulation results are … …American Journal of Applied Sciences, Vol. 13, Issue 6 · 23 Jun 2016 · 7,871 accessesView PDF Cite

Research ArticleOpen accessRobust Positioning of Laser Beams Using Proportional Integral Derivative and Based Observer-Feedback ControlKwabena A. Konadu, Sun Yi, Wonchang Choi, Taher Abu-LebdehHigh-precision positioning of laser beams has been a great challenge in industry due to inevitable existence of noise and disturbance. The work presented in this study addresses this problem by employing two different control strategies: Proportional Integral Derivative (PID) control and state feedback control with an observer. The control strategies are intended to stabilize the position of a laser beam … …American Journal of Applied Sciences, Vol. 10, Issue 4 · 19 Apr 2013 · 6,874 accessesView PDF Cite

Research ArticleOpen accessTime-Delay Estimation using the Characteristic Roots of Delay Differential EquationsSun Yi, Wonchang Choi, Taher Abu-LebdehProblem statement: For ordinary dynamic systems (i.e., non-delayed), various methods such as linear least-squares, gradient-weighted least-squares, Kalman filtering and other robust techniques have been widely used in signal processing, robotics, civil engineering. On the other hand, time-delay estimation of systems with unknown time-delay is still a challenging problem due to difficulty in formulation caused. Approach: The presented method makes use … …American Journal of Applied Sciences, Vol. 9, Issue 6 · 7 Apr 2012 · 8,090 accessesView PDF Cite

Research ArticleOpen accessLow Cycle Fatigue Behavior of a Reduced End Plate Moment Connection (T-Stub)Chemin Lim, Wonchang Choi, Emmett A. Sumner, Taher Abu-LebdehProblem statement: In this research, four reduced End Plate Moment Connection (EPMC) specimens (T-stubs) are tested to verify the numerical and theoretical methods for preanalysis of the Low Cycle Fatigue (LCF) behavior of a four-bolt extended unstiffened EPMC. Approach: The T-stub specimens are bolted to a support frame and a monotonic load is applied to the stem plate. Yield line … …American Journal of Engineering and Applied Sciences, Vol. 4, Issue 4 · 12 Jan 2012 · 7,402 accessesView PDF Cite

Research ArticleOpen accessDetection of Subsurface Defects in Concrete Bridge Deck JointsWonchang Choi, Larry Rickard, Taher Abu-Lebdeh, Miguel PicornellProblem statement: The integrity of deck joints in highway bridges plays a major role to determine overall performance of bridge system. As the bridge maintenance program, the defects in deck joints have historically been detected by conventional non-destructive testing and evaluation methods such as visual inspection, chain-dragging and by the detecting sounds under the traffic. Future bridge maintenance challenges will … …American Journal of Engineering and Applied Sciences, Vol. 4, Issue 4 · 31 Dec 2011 · 7,777 accessesView PDF Cite

Research ArticleOpen accessUse of Recycled Aggregate and Fly Ash in Concrete PavementMyle Nguyen James, Wonchang Choi, Taher Abu-LebdehProblem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55) the compressive strength, … …American Journal of Engineering and Applied Sciences, Vol. 4, Issue 2 · 12 Jul 2011 · 9,315 accessesView PDF Cite

Research ArticleOpen accessHigh Rate-Dependent Interaction Diagrams for Reinforced Concrete ColumnsTaher Abu-Lebdeh, Sameer Hamoush, Wonchang Choi, Moayyad Al NasraProblem statement: There is a need to better understand the rate dependence behavior of reinforced concrete structures in order to improve their response to impact and blast loads. Analysis and design of reinforced concrete structures subjected to seismic loadings has been recommended in many FEMA guidelines. However, reevaluation of design becomes extremely important in cases where large deformations are expected … …American Journal of Engineering and Applied Sciences, Vol. 4, Issue 1 · 27 Jan 2011 · 8,023 accessesView PDF Cite