Browsing by Author "Tang, PC"

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A sliding mode current control scheme for PWM brushless DC motor drives
(1999-05-01)
Chen, J
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Tang, PC
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交大名義發表
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National Chiao Tung University
This paper proposes a sliding mode current control scheme for pulsewidth modulation (PWM) brushless de motor drives. An improved "equivalent control" method is used in this scheme. A simple algorithm is proposed that differs from the original equivalent control method, which requires extensive calculation to estimate the load parameters. This algorithm can be implemented using logic circuits. Moreover, using autotuning, the proposed algorithm can be applied without load information. An operating principle for the power stage switching devices called single-side firing is also proposed. Single-side firing solves the dead-time problem, allowing the PWM frequency to be increased and the sampling rate to be raised. This paper explains the current control algorithm, single-side firing principle, and implementation of the proposed scheme in detail. Simulations and experimental results are given to show the validity of this scheme.
Electronic compensation for nonideal spatial light modulator characteristics
(2000-10-01)
Budgett, DM
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Sharp, JH
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Tang, PC
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Young, RCD
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Scott, BF
Compensation for spatial light modulator device imperfections can be achieved using digital electronics. Optical computing applications, requiring accurate phase or amplitude modulation, can then make use of low-cost, enhanced devices. Using electronic compensation, corrections can be made for a nonsquare aspect ratio in the aperture window and a nonlinear phase response-which may also be nonuniform over the aperture. The corrections for these imperfections are implemented using low-cost field programmable gate arrays. This technology enables real-time compensation and is easily adapted to suit a wide range of display devices. The performance enhancement is demonstrated using a popular Seiko-Epson liquid crystal television display operating as a phase modulating spatial light modulator. These developments greatly extend the utility of readily available, inexpensive, spatial light modulators. (C) 2000 Society of Photo-Optical instrumentation Engineers. [S0091-3286(00)02509-5].