The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
B.c. Chang - One of the best experts on this subject based on the ideXlab platform.
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A Computational Issue and Modified Formulas for Nonlinear Dissipative Controllers
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2003Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW) derived the nonlinear dissipative controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. The assumption is more restrictive than that considered in DGKF In this popery we address the Numerical Difficulty encountered by BHW's controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear dissipative controller and successfully remove the Numerical Difficulty. We also show that the linear version of the proposed controller formulas is identical to the DGKF H ∞ controller. An example is given to demonstrate constructing the proposed controller and simulating the closed-loop pulse responses.
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A Computational Issue in Nonlinear H
1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW) derived nonlinear H, controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. In this paper, we address the Numerical Difficulty encountered by BHWs controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear H, controller and successfully remove the Numerical Difficulty. 1. Introduction It is well-known in the control community that the linear H, control problem can be easily solved by the DGKF (l) state-space approach. Recently, many investigators (2-51 have successfully tackled the much more complicated nonlinear H, problem by the concept of energy dissipation. BHW (5) used a separation principle and the solutions to the Hamilton-Jacobi inequalities (HJIs) to construct a nonlinear H, controller. An assumption was made so that no stable mode is uncontrollable from the exogenous input for the corresponding linearized model. The assumption is more restrictive than those considered in (I). In this paper, we address the Numerical Difficulty encountered by BHWs controller formulas when the assumption is not satisfied. In order to obtain a nonlinear H, controller one needs to solve the Hamilton-Jacobi equations (HJEs) or HJIs. It is very difficult, if not impossible, to find the exact explicit solution for HJE. An approximate soIution (2) is in the form of power series in which the first term is computed via the solution of the corresponding algebraic Riccati equation (ARE). We will explain how the Numerical Difficulty arises in solving the BHW's ARES or inequalities (ARIs). Then we will modify the HJEs and nonlinear H, controller formulas and eliminate the Numerical Difficulty. An illustrative example is also included.
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Modified Nonlinear H- Controller Formulas and the H_ I/O Linearization Problem
1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:A Numerical Difficulty arises when the existing nonlinear H, control formulas are employed to solve the H, VO (input-output) linearization problem, which is formulated as an output feedback nonlinear H, control problem. We propose a modified nonlinear H, controller and successfully remove the Numerical Difficulty. A successive algorithm is also given to solve the HamiltonJacobi equation which is essential in the solution of the nonlinear H, control problem.
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A computational issue in nonlinear H/sub /spl infin// control
Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW, 1993) derived nonlinear H/sub /spl infin// controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. In this paper, we address the Numerical Difficulty encountered by BHW's controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear H/sub /spl infin// controller and successfully remove the Numerical Difficulty.
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Modified nonlinear H/sub /spl infin// controller formulas and the H/sub /spl infin// I/O linearization problem
Proceedings of the 37th IEEE Conference on Decision and Control (Cat. No.98CH36171), 1998Co-Authors: Shu-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:A Numerical Difficulty arises when the existing nonlinear H/sub /spl infin// control formulas are employed to solve the H/sub /spl infin// I/O (input-output) linearization problem, which is formulated as an output feedback nonlinear H/sub /spl infin// control problem. We propose a modified nonlinear H/sub /spl infin// controller and successfully remove the Numerical Difficulty. A successive algorithm is also given to solve the Hamilton-Jacobi equation which is essential in the solution of the nonlinear H/sub /spl infin// control problem.
Pao-hwa Yang - One of the best experts on this subject based on the ideXlab platform.
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A Computational Issue and Modified Formulas for Nonlinear Dissipative Controllers
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2003Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW) derived the nonlinear dissipative controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. The assumption is more restrictive than that considered in DGKF In this popery we address the Numerical Difficulty encountered by BHW's controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear dissipative controller and successfully remove the Numerical Difficulty. We also show that the linear version of the proposed controller formulas is identical to the DGKF H ∞ controller. An example is given to demonstrate constructing the proposed controller and simulating the closed-loop pulse responses.
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A Computational Issue in Nonlinear H
1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW) derived nonlinear H, controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. In this paper, we address the Numerical Difficulty encountered by BHWs controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear H, controller and successfully remove the Numerical Difficulty. 1. Introduction It is well-known in the control community that the linear H, control problem can be easily solved by the DGKF (l) state-space approach. Recently, many investigators (2-51 have successfully tackled the much more complicated nonlinear H, problem by the concept of energy dissipation. BHW (5) used a separation principle and the solutions to the Hamilton-Jacobi inequalities (HJIs) to construct a nonlinear H, controller. An assumption was made so that no stable mode is uncontrollable from the exogenous input for the corresponding linearized model. The assumption is more restrictive than those considered in (I). In this paper, we address the Numerical Difficulty encountered by BHWs controller formulas when the assumption is not satisfied. In order to obtain a nonlinear H, controller one needs to solve the Hamilton-Jacobi equations (HJEs) or HJIs. It is very difficult, if not impossible, to find the exact explicit solution for HJE. An approximate soIution (2) is in the form of power series in which the first term is computed via the solution of the corresponding algebraic Riccati equation (ARE). We will explain how the Numerical Difficulty arises in solving the BHW's ARES or inequalities (ARIs). Then we will modify the HJEs and nonlinear H, controller formulas and eliminate the Numerical Difficulty. An illustrative example is also included.
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Modified Nonlinear H- Controller Formulas and the H_ I/O Linearization Problem
1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:A Numerical Difficulty arises when the existing nonlinear H, control formulas are employed to solve the H, VO (input-output) linearization problem, which is formulated as an output feedback nonlinear H, control problem. We propose a modified nonlinear H, controller and successfully remove the Numerical Difficulty. A successive algorithm is also given to solve the HamiltonJacobi equation which is essential in the solution of the nonlinear H, control problem.
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A computational issue in nonlinear H/sub /spl infin// control
Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998Co-Authors: Shr-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:Ball, Helton, and Walker (BHW, 1993) derived nonlinear H/sub /spl infin// controller formulas with the assumption implying that no stable mode uncontrollable from the exogenous input. In this paper, we address the Numerical Difficulty encountered by BHW's controller formulas when the assumption is not satisfied. Next, we propose a modified nonlinear H/sub /spl infin// controller and successfully remove the Numerical Difficulty.
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Modified nonlinear H/sub /spl infin// controller formulas and the H/sub /spl infin// I/O linearization problem
Proceedings of the 37th IEEE Conference on Decision and Control (Cat. No.98CH36171), 1998Co-Authors: Shu-shiung Hu, Pao-hwa Yang, B.c. ChangAbstract:A Numerical Difficulty arises when the existing nonlinear H/sub /spl infin// control formulas are employed to solve the H/sub /spl infin// I/O (input-output) linearization problem, which is formulated as an output feedback nonlinear H/sub /spl infin// control problem. We propose a modified nonlinear H/sub /spl infin// controller and successfully remove the Numerical Difficulty. A successive algorithm is also given to solve the Hamilton-Jacobi equation which is essential in the solution of the nonlinear H/sub /spl infin// control problem.
Yean-woei Kiang - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic modeling of organic light-emitting devices
Journal of Lightwave Technology, 2006Co-Authors: Hung-chi Chen, C.c. Yang, Chia-chiang Shiau, Yean-woei KiangAbstract:Based on the rigorous electromagnetic wave theory, a Numerical model for simulating the radiation characteristics of organic light-emitting devices (OLEDs) is developed. In particular, a novel method for overcoming the Numerical Difficulty in taking the thick glass substrate into account is proposed. The Numerical results confirm the importance of the effects of the thick glass substrate. The algorithms based on the Numerical model are then used for evaluating the dependencies of OLED radiation characteristics on various parameters, including the thickness of different device layers and the cathode metal variety. In the study of the effect of emission layer (EML) thickness, it is found that the radiation spectral peak red shifts with increasing EML thickness. This trend is consistent with the experimental result.
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Simulations on the radiation characteristics of an organic light emitting diode
CLEO Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003Co-Authors: Hung-chi Chen, Yean-woei Kiang, C.c. Yang, Yih ChangAbstract:The radiation angle and wavelength dependencies of electroluminescence from a multilayer organic light-emitting diode (OLED) are Numerically investigated. The Numerical Difficulty arising from the large thickness of the glass layer in the OLED is carefully overcome.
Noboru Sebe - One of the best experts on this subject based on the ideXlab platform.
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Application of Facial Reduction to H∞ State Feedback Control Problem
IFAC-PapersOnLine, 2020Co-Authors: Hayato Waki, Noboru SebeAbstract:Abstract One often encounters Numerical difficulties in solving linear matrix inequality (LMI) problems obtained from H ∞ control problems. We discuss the reason from the viewpoint of optimization. It is empirically known that a Numerical Difficulty occurs if the resulting LMI problem or its dual is not strongly feasible. In this paper, we provide necessary and sufficient conditions for LMI problem and its dual not to be strongly feasible, and interpret them in terms of control system. For this, facial reduction, which was proposed by Borwein and Wolkowicz, plays an important role. We show that a necessary and sufficient condition closely related to the existence of invariant zeros in the closed left-half plane in the system, and present a way to remove the Numerical Difficulty with the null vectors associated with invariant zeros in the closed left-half plane. Numerical results show that the Numerical stability is improved by applying it.
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CDC - Reduction of SDPs in H ∞ control of SISO systems and performance limitations analysis
2016 IEEE 55th Conference on Decision and Control (CDC), 2016Co-Authors: Hayato Waki, Yoshio Ebihara, Noboru SebeAbstract:In SDP-based H ∞ control, we often encounter Numerical difficulties when solving SDPs by various pieces of software. It is empirically known that such Numerical Difficulty occurs if an SDP at hand or its dual has no interior point feasible solutions, and this is indeed the case of some SDPs in H ∞ control. To conceive a way for getting around such Numerical difficulties in a concrete problem setting, in this paper, we focus on the dual SDP for the H ∞ control problem of the transfer function (1 + PK)-1P and simplify it. More precisely, by actively using the information of unstable zeros (non-minimum phase zeros) of the plant P, we reduce the original dual SDP into a set of simplified SDPs each of which and its dual have interior point feasible solutions. In this way, we show by Numerical experiments that reliable Numerical computation can be done by SDP software. On the other hand, once we have obtained simplified SDPs, it becomes possible to further reduce them into the computation of maximum singular values of matrices determined by unstable zeros. In this way, if the number of unstable zeros is moderate, we can obtain analytical expressions of the best achievable H ∞ performance or its lower bounds in terms of the unstable zeros. Keywords: H ∞ control, SDP, Numerical reliability, best achievable performance.
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Reduction of SDPs in H∞ control of SISO systems and performance limitations analysis
2016 IEEE 55th Conference on Decision and Control (CDC), 2016Co-Authors: Hayato Waki, Yoshio Ebihara, Noboru SebeAbstract:In SDP-based H∞ control, we often encounter Numerical difficulties when solving SDPs by various pieces of software. It is empirically known that such Numerical Difficulty occurs if an SDP at hand or its dual has no interior point feasible solutions, and this is indeed the case of some SDPs in H∞ control. To conceive a way for getting around such Numerical difficulties in a concrete problem setting, in this paper, we focus on the dual SDP for the H∞ control problem of the transfer function (1 + PK)-1P and simplify it. More precisely, by actively using the information of unstable zeros (non-minimum phase zeros) of the plant P, we reduce the original dual SDP into a set of simplified SDPs each of which and its dual have interior point feasible solutions. In this way, we show by Numerical experiments that reliable Numerical computation can be done by SDP software. On the other hand, once we have obtained simplified SDPs, it becomes possible to further reduce them into the computation of maximum singular values of matrices determined by unstable zeros. In this way, if the number of unstable zeros is moderate, we can obtain analytical expressions of the best achievable H∞ performance or its lower bounds in terms of the unstable zeros. Keywords: H∞ control, SDP, Numerical reliability, best achievable performance.
Hung-chi Chen - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic modeling of organic light-emitting devices
Journal of Lightwave Technology, 2006Co-Authors: Hung-chi Chen, C.c. Yang, Chia-chiang Shiau, Yean-woei KiangAbstract:Based on the rigorous electromagnetic wave theory, a Numerical model for simulating the radiation characteristics of organic light-emitting devices (OLEDs) is developed. In particular, a novel method for overcoming the Numerical Difficulty in taking the thick glass substrate into account is proposed. The Numerical results confirm the importance of the effects of the thick glass substrate. The algorithms based on the Numerical model are then used for evaluating the dependencies of OLED radiation characteristics on various parameters, including the thickness of different device layers and the cathode metal variety. In the study of the effect of emission layer (EML) thickness, it is found that the radiation spectral peak red shifts with increasing EML thickness. This trend is consistent with the experimental result.
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Simulations on the radiation characteristics of an organic light emitting diode
CLEO Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003Co-Authors: Hung-chi Chen, Yean-woei Kiang, C.c. Yang, Yih ChangAbstract:The radiation angle and wavelength dependencies of electroluminescence from a multilayer organic light-emitting diode (OLED) are Numerically investigated. The Numerical Difficulty arising from the large thickness of the glass layer in the OLED is carefully overcome.
