University of Southern California – Los Angeles, CA 90089-1453, USA
▪ Ph.D. in Aerospace Engineering (December 2012)
◦ Supervisor: Prof. Firdaus E. Udwadia
◦ Dissertation: New Approaches to Satellite Formation-Keeping and the Inverse Problem of the Calculus of Variations
Yonsei University – Seoul 120-749, Republic of Korea
▪ M.S. in Astronomy and Space Science (February 2008)
◦ Supervisor: Prof. Sang -Young Park
◦ Thesis: Analytic Solutions to Fuel-Optimal Reconfiguration of Satellite Formation Flying
▪ B.S. in Astronomy and Space Science (major) and Physics (minor) (February 2006)
Samsung Techwin Co., Ltd., Power Systems Division, Control Group (March 2013 – )
– Gyeonggi-do 463-400, Republic of Korea
▪ Works as a senior research engineer. Develops control algorithms for propulsion control and monitoring systems of MUAVs (Medium-altitude Unmanned Aerial Vehicles) together with Korean Agency for Defense Development. Main work includes 1) analysis of the control requirements, 2) design of controllers using Matlab/Simulink, and 3) verification of the designed controllers via software testing and HILS (Hardware-In-the-Loop Simulations).
▪ Udwadia, F. E., Wanichanon, T., and Cho, H., “Methodology for Satellite Formation-Keeping in the Presence of System Uncertainties,” Journal of Guidance, Control, and Dynamics.
(Accepted for publication)
▪ Udwadia, F. E. and Cho, H., “First Integrals and Solutions of Duffing-Van der Pol Type Equations,” Journal of Applied Mechanics, Vol. 81, No. 3, 2014, pp. 034501-1 – 034501-4.
▪ Cho, H. and Udwadia, F. E. , “Explicit Control Force and Torque Determination for Satellite Formation-Keeping with Attitude Requirements,” Journal of Guidance, Control, and Dynamics, Vol. 36, No.2, 2013, pp. 589-605.
▪ Udwadia, F. E. and Cho, H., “Lagrangians for Damped Linear Multi-Degree-of-Freedom Systems,” Journal of Applied Mechanics, Vol. 80, No.4, 2013, pp. 041023-1 – 041023-10.
▪ Cho, H., Park, S. –Y., Yoo, S. –M., and Choi, K. –H., “Analytical Solution to Optimal Relocation of Satellite Formation Flying in Arbitrary Elliptic Orbits,” Aerospace Science and Technology, Vol. 25, No.1, 2013, pp. 161-176.
▪ Cho, H., Park, S. –Y., Park, H. –E, and Choi, K. –H., “Analytic Solution to Optimal Reconfigurations of Satellite Formation Flying in Circular Orbit under J2 Perturbation,” IEEE Transactions on Aerospace and Electronic Systems, Vol. 48, No. 3, 2012, pp. 2180-2197.
▪ Udwadia, F. E., Leitmann, G., and Cho, H., “Some Further Remarks on Hamilton’s Principle,” Journal of Applied Mechanics, Vol. 78, No. 1, 2011, pp. 011014-1 – 011014-4.
▪ Cho, H. and Udwadia, F. E., “Explicit Solution to the Full Nonlinear Problem for Satellite Formation-Keeping,” Acta Astronautica, Vol. 67, No. 3-4, 2010, pp. 369-387.
▪ Cho, H. and Yu, A., “New Approach to Satellite Formation-Keeping: Exact Solution to the Full Nonlinear Problem,” Journal of Aerospace Engineering, Vol. 22, No. 4, 2009, pp. 445-455.
▪ Cho, H. –C. and Park, S. –Y., “Analytic Solution for Fuel-Optimal Reconfiguration in Relative Motion,” Journal of Optimization Theory and Applications, Vol. 141, No. 3, 2009, pp. 495-512.
▪ Cho, H., Park, S. –Y., and Choi, K. –H., “Application of Analytic Solution in Relative Motion to Spacecraft Formation Flying in Elliptic Orbit,” Journal of Astronomy and Space Sciences, Vol. 25, No. 3, 2008, pp. 255-266.
▪ Cho, H., and Udwadia, F. E., (ASME 2012 International Mechanical Engineering Congress & Exposition, IMECE 2012, Houston, Texas, November 2012) Inverse Problem for Lagrangian Dynamics for Multi-Degree-of-Freedom Systems with Linear Damping.
▪ Udwadia, F. E., and Cho, H. (The 13 th ASCE Earth and Space 2012 Conference, Pasadena, California, April 2012) New Solutions to the Exact Formation-keeping Control of Satellites with Attitude Constraints.
▪ Cho, H., and Udwadia, F. E., (AIAA SPACE 2011 Conference & Exposition, Long Beach, California, September 2011) New Approach to Formation-Keeping Problem of Multiple Satellites with Attitude Requirements.
▪ Wanichanon, T., Cho, H., and Udwadia, F. E., (AIAA SPACE 2011 Conference & Exposition, Long Beach, California, September 2011) Satellite Formation-Keeping Using the Fundamental Equation in the Presence of Uncertainties in the System.
▪ Cho, H., and Udwadia, F. E., (Engineering Mechanics Institute (EMI) 2010 Conference, Los Angeles, California, August 2010) Explicit Solution to Satellite Formation-Keeping Problem with Attitude Constraints.
▪ Cho, H., and Park, S. –Y., (The 16th Mediterranean Conference on Control and Automation, Corsica, France, June 2008) Simple Analytic Solution to the Optimal Reconfigurations in General Relative Motions.
▪ Cho, H., Park, S. –Y., and Choi, K. –H., (The Annual Spring Conference of the Korean Space Science Society, Cheongju, Rep. of Korea, April 2008) Simple Analytic Solutions for Optimal Reconfigurations in General Relative Motion.
▪ Cho, H., Park, S. –Y., and Choi, K. –H., (The Annual Fall Conference of the Korean Space Science Society, Daegu, Rep. of Korea, October 2007) An Analytic Solution to FuelOptimal Reconfiguration of Satellite Formation Flying in the Presence of J2 Geopotential Disturbance.
▪ Cho, H. –C., Yoo, S. –M., Park, S. –Y., and Choi, K. –H., (The Annual Spring Conference of the Korean Space Science Society, Busan, Rep. of Korea, April 2007) Applications of Analytical Solutions into Reorienting, Resizing, and Retargeting of Formation Flying.
▪ Yoo, S. –M., Cho, H. –C., Park, S. –Y., and Choi, K. –H., (The Annual Spring Conference of the Korean Space Science Society, Busan, Rep. of Korea, April 2007) Numerical Validation of Analytical Solution to Optimal Reconfiguration of Satellite Formation Flying in Arbitrary Elliptical Orbits.
▪ Cho, H. –C., Park, S. –Y., Yoo, S. –M., and Choi, K. –H., (The 17th AAS/AIAA Space Flight Mechanics Meeting, Sedona, AZ, January 2007) Analytical Solution to Optimal Relocation of Satellite Formation Flying in Arbitrary Elliptical Orbits.
▪ Cho, H., and Udwadia, F. E., (The 12th ASCE Earth and Space 2010 Conference, Honolulu, Hawaii, March 2010) Explicit Analytic Solution to the Satellite Formation-Keeping Problem.
Matlab/Simulink, C/C++, Fortran, LabVIEW, Maple, Mathematica, SolidWorks, Solid Edge, PLC
▪ Brain Korea 21 Fellowship, Korean Science and Engineering Foundation, 2006 – 2008
▪ National Research Lab Fellowship, Korean Science and Engineering Foundation, 2006 – 2008
▪ Academic Excellence Scholarship, Yonsei University, 2005
▪ Academic Excellence Scholarship, Yonsei University, 2004
EXTERNAL REVIEWER FOR:
▪ Journal of Aerospace Engineering (8 papers)
▪ Applied Mathematics and Computation (5 papers)
▪ Journal of Optimization Theory and Applications (2 papers)
▪ ASME Applied Mechanics Reviews (1 paper)
▪ Journal of Sound and Vibration (1 paper)
Astrodynamics, Optimal Control, Trajectory Optimization, Satellite Formation Flying, Nonlinear Dynamical Systems, Multi-body Dynamics and Control, Linear, Nonlinear, and Random Vibrations, Numerical Integration of Ordinary/Partial Differential Equations
▪ Teaching Assistant for the junior-level Computer-Aided Analyses for Aero-Mechanical Design.
(Instructor: Dr. Yann Staelens): Duties included grading , hands-on training of SolidWorks and Solid Edge, and holding office hours
(Spring 2011, Spring 2012)
▪ Teaching Assistant for the junior-level Dynamics. (Instructor: Prof. Roger G. Ghanem, Dr. David C. Wilcox): Duties included lectures and holding office hours
(Spring 2010, Fall 2010, Fall 2011)
▪ Teaching Assistant for the graduate-level Linear Control Systems II. (Instructor: Prof. Henryk Flashner): Duties included grading, lectures, and holding office hours
(Fall 2009, Fall 2010)
▪ Teaching Assistant for the graduate-level Engineering Analytical Methods. (Instructor: Prof. Satwindar S. Sadhal): Duties included grading and holding office hours
▪ Teaching Assistant for the graduate-level Engineering Analysis. (Instructor: Prof. Charlie Campbell): Duties included grading and holding office hours
▪ Teaching Assistant for the senior-level Control Systems Laboratory. (Instructor: Dr. Jerry Chen): Duties included grading and holding office hours
▪ Teaching Assistant for the senior-level Space Flight Dynamics. (Instructor: Prof. Sang-Young Park) Duties included grading, lectures, and hands-on training of STK (Satellite Tool Kit®)
University of Southern California, Los Angeles, CA 90089-1453
▪ New methodology for satellite formation-keeping with attitude requirements in the presence of system uncertainties (August 2008 – May 2012)
The purpose of this research is to analytically develop exact formation-keeping guidance schemes that determine control inputs and state trajectories in the presence of both orbital and attitude requirements. The obtained solution is new in that 1) it is assumed that the leader satellite’s reference orbit can be any arbitrary one and the follower satellites are required to point to an arbitrarily chosen specific spot in space that may be time-varying, 2) a method to correct initialcondition misalignment problems due to sensor measurement noise is developed so that both the orbital and attitude control requirements are asymptotically satisfied at any desired rate of convergence, and 3) the effect of model uncertainties is also considered by augmenting an additional additive controller based on a generalization of the notion of sliding surface control. It should be stressed that nonlinear relative dynamics is considered in its entirety without any linearizations/approximations and the solution is obtained in an explicit form, which shows the possibility of precisely controlling nonlinear multi-body systems.
▪ New approaches to the inverse problem of the calculus of variations (August 2010 – December 2012)
To develop the equations of motion for a mechanical system, it is usual to define a Lagrangian function first and then obtain the equations of motion by applying the Lagrange equation when the forces are derivable from a potential function. However, it is interesting and useful to investigate the types of forces that can be engendered when substituting the forces into the Lagrange equation guarantees the proper equations of motion even when the forces do not arise from a potential, that is, when they are nonconservative. In this inverse problem of the calculus of variations, by extending the existing Bolza’s approach, a more general and systematic way of handling the problem is found for single-degree-of-freedom (SDOF) systems. Then, new results for linearly damped multi-degree-of-freedom (MDOF) systems are obtained using extensions of results for SDOF systems. Conservation laws for these damped MDOF systems are also found using the Lagrangians obtained, and the first integrals and the analytical solutions of some nonlinear oscillators (ex. Duffing-van der Pol oscillator) are newly proposed. These new findings can be used for development of approximate solutions of nonlinear differential equations or various numerical techniques.
Yonsei University, Seoul 120-749, Republic of Korea
▪ Analytical analysis of fuel-optimal reconfiguration of formation flying (Sponsor: Korean Science and Engineering Foundation) (March 2006 – July 2008)
The problem of relative motion, formation flying, and rendezvous has been studied. The most significant advantage of the research has been the development of completely analytical results, by use of the Fourier series and the Pontryagin’s minimum principle. The major contributions have been the solutions to the fuel-optimal rendezvous problem for satellite. The results are also valid when the orbits of the satellites are non-circular with arbitrary eccentricity. The J2-perturbed case has been also considered. These findings allow us to predict the form of the optimal solutions in advance without having to solve the problem and significantly reduce the amount of calculations required.
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