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Kaohsiung, Taiwan

Chang Y.,Kao Yuan University
IEEE Transactions on Automatic Control | Year: 2011

Based on the Lyapunov stability theorem, a methodology of designing the block backstepping controller for a class of multi-input multi-output (MIMO) systems is proposed to solve the tracking problem. Some adaptive mechanisms are embedded both in the virtual input controller and in the backstepping controllers so that not only are the perturbations suppressed, but also some knowledge of the upper bound of perturbations is not required. Finally, an example of controlling a two-axis piezoelectric microposition is used to demonstrate the feasibility of the proposed methodology. © 2011 IEEE. Source

The biodegradability, morphology, and mechanical properties of composite materials made from maleic anhydride-grafted poly(hydroxyalkanoate) (PHA-g-MA) and treated (crosslinked) tea plant fibre (t-TPF) were evaluated. Composites containing PHA-g-MA (PHA-g-MA/t-TPF) had noticeably superior mechanical properties compared with those of PHA/TPF because of greater compatibility with TPF. The dispersion of t-TPF in the PHA-g-MA matrix was more homogeneous because of ester formation and the consequent creation of branched and crosslinked macromolecules between the anhydride carboxyl groups of PHA-g-MA and hydroxyl groups in t-TPF. Additionally, the PHA-g-MA/t-TPF composites were more easily processed because of their lower melt viscosities. The water resistance of PHA-g-MA/t-TPF was higher than that of PHA/TPF, although the weight loss of composites buried in soil compost indicated that both were biodegradable, especially at high levels of TPF substitution. The PHA/TPF and PHA-g-MA/t-TPF composites were more biodegradable than pure PHA, which implied a strong connection between TPF content and biodegradability. © 2013 Elsevier Ltd. All rights reserved. Source

Wu C.-S.,Kao Yuan University
Carbohydrate Polymers | Year: 2012

The biodegradability, morphology, mechanical, and thermal properties of composite materials composed of maleic anhydride-grafted poly(butylene adipate-co-terephthalate) (PBAT) and cellulose acetate (CA) were evaluated. Composites containing maleic anhydride-grafted PBAT (PBAT-g-MA/CA) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of CA in the PBAT-g-MA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules between the anhydride carboxyl groups of PBAT-g-MA and hydroxyl groups in CA. Each composite was buried in soil and monitored to assess biodegradability. Both the PBAT and the PBAT-g-MA/CA composite films were eventually completely degraded, and severe disruption of film structure was observed after 60-100 days of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable, even with high levels of CA, the higher water resistance of PBAT-g-MA/CA films indicated that they were more biodegradable than those made of PBAT. © 2011 Elsevier Ltd. All rights reserved. Source

Chen P.-C.,Kao Yuan University
International Journal of Hydrogen Energy | Year: 2011

This paper is on the dynamics analysis and controller design for the PEM fuel cell under the flowrate constraints of the supplied hydrogen and oxygen. By linearization around the equilibrium trajectories defined by the quantities of hydrogen and oxygen input flowrate, the nonlinear dynamics of the PEM fuel cell can be expressed as a linear parameter varying system with the output current and temperature as the system parameters. The state-feedback controller design is performed based on the linear time-invariant model obtained from the derived linear parameter varying system evaluated at the half load operation condition. The control objective is to achieve a maximized relative stability or equivalently the maximum decay rate under the specified magnitude constraints on the input flowrate of hydrogen and oxygen. The convex linear matrix inequality algorithm is utilized for numerical construction of the state-feedback control law. Under the fixed load resistance corresponding to the half load condition, the time response simulations are conducted for both the cases of initial condition regulation and external command tracking. For the simulation of regulation, the initial deviation of state variables diminishes quickly that agrees with the obtained large delay rate during controller design. In the case of command tracking for the same amount of state variables, the controlled system can follow the issued command in the right direction but leave large tracking error, which is due to the weak controllability of the gas flowrates on the activation overvoltage for the PEM fuel cell system dynamics. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. Source

Chen P.-C.,Kao Yuan University
Energy Conversion and Management | Year: 2013

This paper presents a robust control approach for proton exchange membrane (PEM) fuel cell systems. In a linear parameter varying system representation of the nonlinear PEM fuel cell dynamics, the system matrices are dependent on the system varying parameters, the output current and the stack temperature. To obtain guaranteed design performance, system uncertainties caused by the variational system parameters are addressed during controller design. The voltage tracking performance is expressed in terms of H∞ optimization of the ratio of the tracking error to the issued command. The controller is constructed numerically in terms of the convex tractable linear matrix inequalities. Due to the parameter-dependent system matrices of the PEM fuel cells, the formulated matrix inequalities in denoting various design specifications are also dependent on the system varying parameters. Using the affinely dependent property of these matrix inequalities, design performance can be established by evaluating only the matrix inequalities in the extremes of the varying parameters. Both nominal and robust controller designs are verified through time response simulation for both nominal PEM fuel cell and nonlinear PEM fuel cell dynamics. © 2012 Elsevier Ltd. All rights reserved. Source

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