Browsing by Author "Chang, CM"

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A new illumination optical system for liquid crystal projectors
(1997)
Chang, CM
;
Lin, KW
;
Chen, KV
;
Shieh, HPD
;
交大名義發表
A high efficient illumination optical system is designed to generate;In uniform and rectangular light source for liquid crystal light valve projectors. A short are and an optimized reflector design enable the total system to be highly efficient while a rectangular-pillar-like glass rod is used to transform a circular beam into a uniform and rectangular cross-section one. The optical system from the light source through the projection optimized to achieve optical efficiencies of 57% and uniformity of 70%.
A wavelet network control method for disk drives
(2006-01-01)
Chang, CM
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
This paper proposes a wavelet network control method to online learn and cancel repetitive errors in disk drives. In contrast to Fourier transforms, wavelet transforms can provide detailed local information of signals. Based on the wavelet transform, wavelets can approximate any finite energy function. This paper proposes wavelet networks to approximate periodic functions. Accordingly, a wavelet network controller is developed to eliminate repetitive error caused by repetitive disturbance. Experiments for flying height control of a disk drive system are implemented to demonstrate the present method in comparison with another method using Fourier series based network control.
Anti-control of chaos of single time scale brushless dc motors and chaos synchronization of different order systems
(2006-03-01)
Ge, ZM
;
Chang, CM
;
Chen, YS
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機械工程學系
;
Department of Mechanical Engineering
Anti-control of chaos of single time scale brushless dc motors (BLDCM) and chaos synchronization of different order systems are studied in this paper. By addition of an external nonlinear term, we can obtain anti-control of chaos. Then, by addition of the coupling terms, by the use of Lyapunov stability theorem and by the linearization of the error dynamics, chaos synchronization between a third-order BLDCM and a second-order Duffing system are presented. (c) 2005 Elsevier Ltd. All rights reserved.
Application of discrete wavelet transform to repetitive control
(2002)
Chang, CM
;
Liu, TS
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機械工程學系
;
Department of Mechanical Engineering
This study aims to apply the discrete wavelet transform to reduce the memory size of a repetitive controller. The repetitive error signal is decomposed. Only the highest-level approximation coefficients in a tree-structured wavelet transform have to be saved and hence the error signal is compressed. The compressed error signal is in turn reconstructed to compensate the control system. Simulation results are presented to demonstrate effectiveness of the proposed method.
Chaos synchronization and parameters identification of single time scale brushless DC motors
(2004-05-01)
Ge, ZM
;
Chang, CM
;
機械工程學系
;
Department of Mechanical Engineering
Chaos synchronization and parameters identification of single time scale brushless dc motors are studied in this paper. In order to analyze a variety of periodic and chaotic phenomena, we employ several numerical techniques such as phase portrait, bifurcation diagram, and Lyapunov exponents. By the adaptive control, the improved backstepping design method, the Gerschgorin theorem, and by addition of a monitor, chaos synchronization of two identical BLDCM systems are presented. Then, by the adaptive control, and the random optimization method, parameters identification is approached. (C) 2003 Elsevier Ltd. All rights reserved.
Design of illumination and projection optics for projectors with single digital micromirror devices
(2000-07-01)
Chang, CM
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
We present a new optical system design for a projector with a single digital micromirror device (Texas Instruments Digital Micromirror Device) that improves on previous designs in terms of optical efficiency, uniformity, and contrast while yielding a low-profile and compact system. A rod integrator is incorporated with a compact relay system to maximize light efficiency and to increase illumination uniformity. The uniformity achieved by the optimized optical system was calculated to he 94%. In addition, this unique light-separator design has dual output channels to increase the image contrast by steering the off-state light away from the projection lens. This projector design provides very efficient light utilization, and we discuss how the geometrical optical efficiency of the system can be boosted to approach the theoretical maximum. (C) 2000 Optical Society of America. OCIS codes: 080.2740, 080.3620, 220.2740, 220.3620, 120.2040, 230.6120.
High-efficiency polarized light illumination system for liquid-crystal-display projectors
(2000-12-01)
Chang, CM
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
We present a new optical system with two identical s- and p-polarized light paths for converting a random polarized beam into a linearly polarized one. The system also provides a uniform and rectangular cross-section beam on the light valve. The geometrical factor of the polarization-conversion efficiency of 190% and the uniformity at the liquid crystal display (LCD) plane of above 90% has been achieved by this optimized optical system.
Simple formulas for calculating wave propagation and splitting in anisotropic media
(2001-11-01)
Chang, CM
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
A general method for dealing with the propagation of waves in homogeneous anisotropic media is presented. The formulas were derived and applied to determine the reflected and transmitted waves resulting from a plane wave obliquely incident at an interface between two anisotroptic media with arbitrarily oriented principal axes. The validity of the formulas was also demonstrated by calculating the reflection and refraction at a biaxial-biaxial interface.
Study on wavelet repetitive control
(2004-05-01)
Chang, CM
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
Repetitive control has been applied to robots, disk drives, etc. However, the memory size in repetitive controllers linearly increases with both the repetition time and the sampling frequency. Hence, the authors aim to apply discrete wavelet transforms to lower the memory requirements of repetitive controllers. The repetitive error signal is decomposed using a wavelet transform. Only the highest-level approximation coefficients and a few detail coefficients in the wavelet transform have to be saved and hence the error signal is compressed. The compressed error signal is in turn reconstructed to compensate the control system. Simulation results are presented to demonstrate the effectiveness of the proposed method.