Browsing by Author "Chen, FC"

Now showing 1 - 14 of 14

Adaptive control of a class of nonlinear systems using neural networks
(1995)
Chen, FC
;
Khalil, HK
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電控工程研究所
;
Institute of Electrical and Control Engineering
Formation of phase grating in planar aligned cholesteric liquid crystal film
(2002-11-15)
Wu, JJ
;
Wu, YS
;
Chen, FC
;
Chen, SH
;
光電工程學系
Electric-field-induced cholesteric liquid crystal phase gratings were investigated by means of changing the film thickness-to-natural-pitch ratio d/p(0) and the applied voltage. Planar parallel (180degrees)-, antiparallel (0degrees)- and twist (90degrees)-aligned films were fabricated. By varying the d/p(0) value, we found that the stripes of the gratings could only be in two directions. It was interesting that the directions were mutually perpendicular. This device could be used as a grating switch.
General two-stage Kalman filters
(2000-04-01)
Hsieh, CS
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A general two-stage Kalman filter (GTSKF) that is equivalent to, but numerically more efficient than, the standard single-stage Kalman Biter is developed for general, time-varying, linear discrete-time systems. Analytical results defining the reduction in computational burdens are presented. Simulation results that validate the predicted efficiency improvements are shown as well.
Improved CMAC neural network control scheme
(1999-01-21)
Lin, CC
;
Chen, FC
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電控工程研究所
;
Institute of Electrical and Control Engineering
The cerebellar model articulation controller (CMAC) neural network control scheme is a powerful tool for practical real-time nonlinear control applications. However, despite its initial outstanding performance, the CMAC control system can suddenly diverge after a long period of stable tracking. The authors propose a modification to the CMAC control scheme in order to improve stability while preserving the original good performance.
Improving conventional longitudinal missile autopilot using cerebellar model articulation controller neural networks
(2003-09-01)
Lin, CC
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A way to integrate the cerebellar model articulation controller (CMAC) neural network with the missile longitudinal conventional feedback controller (CFC) to compensate for nonlinearities, unmodeled dynamics, parameter variations, etc., is proposed. The inner loop of the CFC will essentially be left unchanged to improve the stability of the missile. The outer loop of CFC, in addition to playing its traditional role, would work with the CMAC to learn quickly to approximate the dynamic inversion from angle of attack to control deflection, to achieve better tracking in normal acceleration. In this arrangement, the well-known CFC acts as a safety net, whereas additional performance is brought about through CMAC learning.
Modified stochastic Luenberger observers
(2000-12-01)
Hsieh, CS
;
Chen, FC
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電控工程研究所
;
Institute of Electrical and Control Engineering
A modified stochastic Luenberger observer (MSLO) structure is proposed to recover the optimal performance of the coventional SLO for obtaining full-state estimates in linear discrete-time stochastic systems. The optimal MSLO (OMSLO) which gives the MMSE estimates is derived by using the general two-stage Kalman filter. A reduced-order form of the OMSLO is also proposed for systems having singular measurement noises. The connection between the OMSLO and the optimal minimal-order observer of Leondes and Novak is also shown. (C) 2000 Elsevier Science Ltd. All rights reserved.
On a new CMAC control scheme, and its comparisons with the PID controllers
(2001)
Lin, CC
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The behaviors and stability of a new CMAC control scheme are studied, whose comparisons with PID controllers are also investigated. Unlike the traditional role of modeling inverse system dynamics, the CMAC controller is proposed to emulate the PD plus gravity-compensation control for robotics. In this new control scheme, the CMAC produces enormous integration action when the input vector moves slowly in the space so that it can respond quickly to large loads. On the other hand, it can also forget efficiently when the input vector moves fast in the space so that it is not burdened by previous integration. It is shown that the CMAC control system can converge into the target position. The systems employed in this study are one-link and two-link robotics.
Optimal minimal-order least-squares estimators via the general two-stage Kalman filter
(2001-11-01)
Hsieh, CS
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A direct derivation of the optimal minimal-order least-squares estimator (OMOLSE) is presented using the recently developed general two-stage Kalman filter (GTSKF). Using this new result, the reduced-order estimators of O'Reilly and Fairman are readily shown to be equivalent. A practical implementation issue to consider these two estimators is also addressed.
Optimal multistage Kalman estimators
(2000-11-01)
Chen, FC
;
Hsieh, CS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
An optimal multistage Kalman estimator (OMSKE) is proposed as a generalization of the optimal two-stage Kalman estimator for the reduction of the computational burden of the Kalman estimator (KE) for discrete-time linear time-varying systems with triangular transition matrices. This new filter is obtained by applying a multistage U - V transformation to decouple the covariances of the KE. It is shown analytically that the computational complexity of the OMSKE is less than that of the KE and is minimum when the system transition matrix has the maximum stage number.
Optimal solution of the two-stage Kalman estimator
(1995)
Hsieh, CS
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Optimal solution of the two-stage Kalman estimator
(1999-01-01)
Hsieh, CS
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The two-stage Kalman estimator was originally proposed to reduce the computational complexity of the augmented state Kalman filter. Recently, it was also applied to the tracking of maneuvering targets by treating the target acceleration as a bias term, Except in certain restrictive conditions, the conventional two-stage estimators are suboptimal in the sense that they are not equivalent to the augmented state filter. In this paper, the authors propose a new two-stage Kalman estimator, i.e. new structure, which is an extension of Friedland's estimator and is optimal in general conditions, In addition, we provide some analytic results to demonstrate the computational advantages of two-stage estimators over augmented ones.
Organic selective-area patterning method for microlens array fabrication
(2006-04-01)
Huang, WK
;
Ko, CJ
;
Chen, FC
;
光電工程學系
;
顯示科技研究所
Refractive microlens arrays (MLAs) are widely used in many electro-optical devices due to their high performance and low optical loss. To fabricate a microlens array effectively, we have proposed a novel fabrication method based on a selective-area patterning method. The surface properties of glass substrates were defined as either hydrophilic or hydrophobic regions by microcontact printing of self-assembled monolayers (SAMs). Consequently, the microlens arrays were self-organized on the hydrophilic regions after the lens materials were nozzle-spread followed by UV curing. As a result, we have demonstrated microlenses with 50, 75, and 100 Pm footprints, and f numbers as low as 5.4. The focused spot size of the 50 mu m lens was 9.82 mu m, which is near the diffraction limit. The optical measurement shows excellent light collecting efficiency of a microlens array, which is suitable for many electro-optical applications. Furthermore, all fabrication steps can be accomplished in ambient environment and at room temperature. It is anticipated that the present proposed method has great potential for mass production. (c) 2006 Elsevier B.V. All rights reserved.
Phase gratings in pretilted homeotropic cholesteric liquid crystal films
(2002-10-01)
Wu, JJ
;
Chen, FC
;
Wu, YS
;
Chen, SH
;
光電工程學系
We studied the fingerprint texture of homeotropic cholesteric liquid crystal (CLC) films. Parallel (360) and antiparallel (180) alignment treatments were adopted for these films such that the molecules at the boundaries had an approximately I pretilt angle to the substrate normal. The experimental results showed that the homeotropic film may be more suitable than the planar-parallel film for use in an electrically controlled phase grating.
Practical stability issues in CMAC neural network control systems
(1996-01-01)
Chen, FC
;
Chang, CH
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The cerebellar model articulation controller (CMAC) neural network is a practical tool for improving existing nonlinear control systems. A typical simulation study is used to clearly demonstrate that the CMAC can effectively reduce tracking error, but can also destabilize a control system which is otherwise stable. Then quantitative studies are presented to search for the cause of instability in the CMAC control system. Based on these studies, methods are discussed to improve system stability, Experimental results on controlling a real world system are provided to support the findings in simulations.