Pukdeboon C.,King Mongkuts University of Technology Bangkok
Asian Journal of Control | Year: 2013
This paper investigates the problem of output feedback attitude tracking control of a rigid spacecraft in the presence of external disturbances. Two optimal control laws with a disturbance estimator are developed to deal with this problem. An adapted extended state observer is used to estimate the angular velocity tracking errors and to allow for compensation for the total disturbances. The proposed control can be expressed as the sum of a nonlinear optimal controller and an estimated disturbance. For the optimal controller, the state-dependent Riccati equation and optimal Lyapunov techniques are employed to solve the infinite-time nonlinear optimal control problem. The developed controllers can minimize a performance index and ensure the stability of the closed-loop system and external disturbance attenuation. On the other hand, using the adapted extended state observer, the asymptotic convergence of estimation error dynamics is proven. An example of multiaxial attitude manoeuvres is given and simulation results are included to demonstrate and verify the usefulness of the proposed controllers. © 2012 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.
Boonloi A.,King Mongkuts University of Technology Bangkok
Modelling and Simulation in Engineering | Year: 2014
A numerical investigation has been carried out to examine the periodic laminar flow and heat transfer characteristics in a three-dimensional isothermal wall square duct with 20° inline V-ribs. The computations are based on the finite volume method, and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the square duct ranging from 100 to 2000. To generate main streamwise vortex flows through the tested section, V-ribs with an attack angle of 20° are mounted in tandem with inline arrangement, pointing downstream (V-Downstream) and pointing upstream (V-Upstream) placed on both the upper and lower walls. Effects of different blockage ratio (b/H, BR) with a single pitch ratio (P/H, PR) of 1 on heat transfer, pressure loss, and performance in the ribbed tube are studied. Apparently in each of the main vortex flows, streamwise twisted vortex flows can induce impinging flows on the walls of the interbaffle cavity leading to drastic increase in heat transfer rate over the square duct. In addition, the rise in the V-baffle height results in the increase in the Nusselt number and friction factor values. The computational results show that the optimum thermal enhancement factor is about 4.2 at BR=0.20 and 0.15 for the V-Downstream and V-Upstream, respectively. © 2014 Amnart Boonloi.
Siengchin S.,King Mongkuts University of Technology Bangkok
Journal of Reinforced Plastics and Composites | Year: 2012
Composites composed of high-density polyethylene, woven flax fiber textiles (flax weave style of 2×2 twill and 4×4 hopsack) and SiO 2 were produced by hot press with nanospraying technique. The SiO 2 slurries were sprayed on the woven flax fiber followed by drying. The related HDPE/woven flax fibers composites were prepared by hot press. The dispersion of SiO 2 particles and flax in the composites was studied by scanning electron microscopy. The related high-density polyethylene based composites were subjected to instrumented falling weight impact test. The thermal resistance, stiffness and tensile strength properties of the composites were determined in thermogravimetric analysis, dynamic-mechanical thermal analysis and tensile tests, respectively. It was found that the impact energy and stiffness value of high-density polyethylene/flax composites was markedly higher than that of high-density polyethylene but reflect the effects of composite structures and flax content. Incorporation of SiO 2 particles enhanced resistance to thermal degradation. It was established that the linear viscoelastic material principle are fairly applicable to convert from the modulus to the creep compliance results. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Thounthong P.,King Mongkuts University of Technology Bangkok |
Davat B.,French National Center for Scientific Research
Energy Conversion and Management | Year: 2010
This paper presents a study of a high power dc distributed system supplied by a fuel cell generator. A proposed parallel power converter with interleaving algorithm is chosen to boost a low dc voltage of fuel cell to a dc bus utility level. The present interleaved step-up converters are composed of two and four identical boost converters connected in parallel. Converters are controlled by interleaved switching signals, which have the same switching frequency and the same phase shift. By virtue of paralleling the converters, the input current can be shared among the cells or phases, so that high reliability and efficiency in power electronic systems can be obtained. In addition, it is possible to improve the system characteristics such as maintenance, repair, fault tolerance, and low heat dissipation. During the past decade, power electronics research has focused on the development of interleaved parallel converters. For an interleaving technique with a real fuel cell source, this work is the first presentation; it is not just a fuel cell simulation. So, the design and experimental verification of 1.2-kW prototype converters at a switching frequency of 25 kHz connected with a NexaTM PEM fuel cell system (1.2-kW, 46-A) in a laboratory is presented. Experimental results corroborate the excellent system performances. The fuel cell ripple current can be virtually reduced to zero. As a result, the fuel cell mean current is nearly equal to the fuel cell rms current. © 2009 Elsevier Ltd. All rights reserved.
Pukdeboon C.,King Mongkuts University of Technology Bangkok
Mathematical Problems in Engineering | Year: 2013
The attitude tracking control problem of a spacecraft nonlinear system with external disturbances and inertia uncertainties is studied. Two robust attitude tracking controllers based on finite-time second-order sliding mode control schemes are proposed to solve this problem. For the first controller, smooth super twisting control is applied to quaternion-based spacecraft-attitude- tracking maneuvers. The second controller is developed by adding linear correction terms to the first super twisting control algorithm in order to improve the dynamic performance of the closed-loop system. Both controllers are continuous and, therefore, chattering free. The concepts of a strong Lyapunov function are employed to ensure a finite-time convergence property of the proposed controllers. Theoretical analysis shows that the resulting control laws have strong robustness and disturbance attenuation ability. Numerical simulations are also given to demonstrate the performance of the proposed control laws. © 2013 Chutiphon Pukdeboon.