教師著作

Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/31268

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Author: search.filters.author.Wern-Yarng Shieh

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    A Problem of Infrared Electronic-Toll-Collection Systems: the Irregularity of the LED Radiation Pattern and the Emitter Design
    (IEEE Intelligent Transportation Systems Society, 2011-03-01) Wern-Yarng Shieh; Chen-Chien Hsu; Ti-Ho Wang
    According to our measurements, the radiation pattern of many low-cost commercial light-emitting diodes (LEDs) is not smooth. Some LEDs even have serious irregularities that affect the performance of infrared communication systems. For systems where a definite communication area is required, such as electronic-toll-collection (ETC) applications, this problem is particularly serious. In this paper, we first present our measured results for the radiation pattern of several typical low-cost commercial LEDs, showing that almost all of them are irregular to some extent. We then use the most acceptable model with a suitable half-intensity angle to construct the emitter of an ETC system. The design was calculated with the aid of an optimization algorithm to determine the mounting angle for each LED such that the system has an extended communication area in the longitudinal direction, i.e., in the vehicle traveling direction, and can withstand high signal attenuation. For a typical LED with half-intensity angle Φ1/2 = 13°, a very simple two-group structure for the emitter is obtained, and the analysis results are verified by experimental measurements.
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    Digital redesign of uncertain interval systems based on extremal gain/phase margins via a hybrid particle swarm optimizer
    (Elsevier, 2010-03-01) Chen-Chien Hsu; Wern-Yarng Shieh; Chun-Hwei Kao
    In this paper, a hybrid optimizer incorporating particle swarm optimization (PSO) and an enhanced NM simplex search method is proposed to derive an optimal digital controller for uncertain interval systems based on resemblance of extremal gain/phase margins (GM/PM). By combining the uncertain plant and controller, extremal GM/PM of the redesigned digital system and its continuous counterpart can be obtained as the basis for comparison. The design problem is then formulated as an optimization problem of an aggregated error function in terms of deviation on extremal GM/PM between the redesigned digital system having an interval plant and its continuous counterpart, and subsequently optimized by the proposed optimizer to obtain an optimal set of parameters for the digital controller. Thanks to the performance of the proposed hybrid optimizer, frequency-response performances of the redesigned digital system using the digital controller evolutionarily derived by the proposed approach bare a far better resemblance to its continuous-time counter part in comparison to those obtained using existing open-loop discretization methods.
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    Design of Infrared Electronic-Toll-Collection Systems with Extended Communication Areas and Performance of Data Transmission
    (IEEE Intelligent Transportation Systems Society, 2011-03-01) Wern-Yarng Shieh; Chen-Chien Hsu; Shen-Lung Tung; Po-Wen Lu; Ti-Ho Wang; Shyang-Lih Chang
    Based on our previous works in the design of an infrared emitter for electronic-toll-collection (ETC) applications, we use the unidirectional cosinen functions to approximate the irregular radiation pattern for typical infrared low-cost commercial light-emitting diodes (LEDs) with a half-intensity angle Φ1/2 = 10°. With the aid of this approximation, the main characteristics of the performance of an infrared ETC system utilizing this type of LED as the emitter can be investigated based on the received signal strength of the system. For on-off keying, a simple model connecting the received signal strength and the bit error rate (BER) of the system is further established. From the calculated or the measured received signal strength of the system, it is not difficult to estimate the system performance in terms of the BER by this simple model. Roughly speaking, for a typical setting of the circuit parameters and a typical uplink and downlink data-transmission protocol, the data transmission can be very successful in terms of a very low BER if the received signal strength is 1.3 times stronger than the signal strength received at the communication boundary. The emitter presented in this paper is able to produce a relatively extended communication area in the vehicle-traveling direction, resulting in longer communication time interval for the data transmission between the onboard unit (OBU) and the roadside unit (RSU) than conventional emitters. Furthermore, the design presented in this paper is validated by experimental measurement to demonstrate its effectiveness.