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This paper presents the development of a front-end converter and its control for a battery powered switched-reluctance motor (SRM) drive. In motoring mode, the converter is operated as a dc-dc boost converter to establish dynamically boostable and well-regulated dc-link voltage from battery. The digital control schemes of boost converter and motor drive are implemented using a common digital signal processor. A proper voltage boosting feedback controller is designed to effectively enhance the SRM winding current and speed dynamic responses. Then the robust speed control performance is achieved by the proposed control scheme consisting of robust disturbance feedforward control and variable-structure system control. In addition, an effective regenerative braking control scheme for SRM is developed. In idle charging mode, the proposed front-end converter is arranged to act as a buck-type switch-mode rectifier (SMR) for charging the battery with good line power quality. Four diodes embedded in the SRM converter and the two motor phase winding inductances are employed to form the necessary constituted components of the SMR. The circuit and controller designs are presented, and good charging power conditioning performance is demonstrated experimentally. Index Terms--Battery, buck switch-mode rectifier, charger, digital signal processor (DSP), front-end converter, regenerative braking, robust control, switched-reluctance motor (SRM), variable-structure system (VSS) control.

What we believe to be a new principle is introduced for the design and selection of gradient-index antireflection profiles that are effective over a wide range of incident angles as well as wavelengths at a given physical film thickness. It is shown that at oblique incidence the smoothness of the optical path of incident light inside a gradient-index film has a crucial effect on the overall reflection. Thus the smoothness of variations in refractive angle (rather than that of the index profile itself) needs to be maximized for wide-angle operation. As an example, the performance of Gaussian and Quintic profiles at large incident angles are considered in light of this point of view. OCIS codes: 310.1210, 310.1620.

For fused tapered fiber couplers with weakly fused cross sections, power coupling takes place between two touching tapered cladding cylinders embedded in the air, and the cylinders then become a strongly guiding structure. We provide accurate polarization-dependent coupling coefficients for such a structure, on the basis of a rigorous vectorial numerical calculation. Our results for the corresponding weakly guiding structure are compared with previous vector perturbation methods base on scalar fields. It is found that the scalar theories are not applicable to those cases with large normalized frequencies or with small fiber separations when the polarization-splitting effect is concerned.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2007.01.013 Byline: Yun-Chi Tang, Hung-Chun Chang, Manajit Hayer-Hartl, F. Ulrich Hartl

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2007.01.001 Byline: Hung-Chun Chang, Yun-Chi Tang, Manajit Hayer-Hartl, F. Ulrich Hartl