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A robust polysilicon-assisted SCR in ESD protection application
CUI Qiang, HAN Yan, DONG Shu-rong, LIOU Juin-jie
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1879-1883.
https://doi.org/10.1631/jzus.2007.A1879
A novel polysilicon-assisted silicon-controlled rectifier (SCR) is presented and analyzed in this paper, which is fabricated in HHNEC’s 0.18 μm EEPROM process. The polysilicon-assisted SCRs take advantage of polysilicon layer to help bypass electro-static discharge (ESD) current without occupying extra layout area. TLP current-voltage (I-V) measurement results show that given the same layout areas, robustness performance of polysilicon-assisted SCRs can be improved to 3 times of conventional MLSCR’s. Moreover, one-finger such polysilicon-assisted SCRs, which occupy only 947 μm2 layout area, can undergo 7-kV HBM ESD stress. Results further demonstrate that the S-type I-V characteristics of polysilicon-assisted SCRs are adjustable to different operating conditions by changing the device dimensions. Compared with traditional SCRs, this new SCR can bypass more ESD currents and consumes smaller IC area.
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Equalization for continuous phase modulation over frequency-selective fading channels
JIN Xiao-dong, ZHAO Min-jian, SUN Ling, SHEN Wen-li
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1884-1888.
https://doi.org/10.1631/jzus.2007.A1884
This paper presents an equalization algorithm for continuous phase modulation (CPM) over frequency-selective channels. A specific training sequence is first embedded in each data packet. By recursive least-squares (RLS) estimation, the channel information parameters can be acquired, and a fractionally spaced equalizer performs joint decoding and equalization. Simulation results show that the proposed algorithm can acquire the channel information parameters rapidly and accurately, and that the fractionally spaced equalizer can eliminate the intersymbol interference (ISI) effectively, and is not sensitive to timing inaccuracy, so this algorithm can be exploited for demodulation system in burst mode.
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Multiobjective extremal optimization with applications to engineering design
CHEN Min-rong, LU Yong-zai, YANG Gen-ke
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1905-1911.
https://doi.org/10.1631/jzus.2007.A1905
In this paper, we extend a novel unconstrained multiobjective optimization algorithm, so-called multiobjective extremal optimization (MOEO), to solve the constrained multiobjective optimization problems (MOPs). The proposed approach is validated by three constrained benchmark problems and successfully applied to handling three multiobjective engineering design problems reported in literature. Simulation results indicate that the proposed approach is highly competitive with three state-of-the-art multiobjective evolutionary algorithms, i.e., NSGA-II, SPEA2 and PAES. Thus MOEO can be considered a good alternative to solve constrained multiobjective optimization problems.
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Iterative learning control of SOFC based on ARX identification model
HUO Hai-bo, ZHU Xin-jian, TU Heng-yong
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1921-1927.
https://doi.org/10.1631/jzus.2007.A1921
This paper presents an application of iterative learning control (ILC) technique to the voltage control of solid oxide fuel cell (SOFC) stack. To meet the demands of the control system design, an autoregressive model with exogenous input (ARX) is established. Firstly, by regulating the variation of the hydrogen flow rate proportional to that of the current, the fuel utilization of the SOFC is kept within its admissible range. Then, based on the ARX model, three kinds of ILC controllers, i.e. P-, PI- and PD-type are designed to keep the voltage at a desired level. Simulation results demonstrate the potential of the ARX model applied to the control of the SOFC, and prove the excellence of the ILC controllers for the voltage control of the SOFC.
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Pressure observer based adaptive robust trajectory tracking control of a parallel manipulator driven by pneumatic muscles
ZHU Xiao-cong, TAO Guo-liang, CAO Jian
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1928-1937.
https://doi.org/10.1631/jzus.2007.A1928
This paper presents a pressure observer based adaptive robust controller (POARC) for posture trajectory tracking of a parallel manipulator driven by three pneumatic muscles without pressure sensors. Due to model errors of the static forces and friction forces of pneumatic muscles, simplified average flow rate characteristics of valves, unknown disturbances of entire system, and unmeasured pressures, there exist rather severe parametric uncertainties, nonlinear uncertainties and dynamic uncertainties in modeling of the parallel manipulator. A nonlinear pressure observer is constructed to estimate unknown pressures on the basis of a single-input-single-output (SISO) decoupling model that is simplified from the actual multiple-input-multiple-output (MIMO) coupling model of the parallel manipulator. Then, an adaptive robust controller integrated with the pressure observer is developed to accomplish high precision posture trajectory tracking of the parallel manipulator. The experimental results indicate that the system with the proposed POARC not only achieves good control accuracy and smooth movement but also maintains robustness to disturbances.
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Designing reduced beacon trajectory for sensor localization
HUANG Wen-liang, LI Shi-jian, LIU Duo
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1971-1982.
https://doi.org/10.1631/jzus.2007.A1971
Localization is one of the substantial issues in wireless sensor networks. The key problem for the mobile beacon localization is how to choose the appropriate beacon trajectory. However, little research has been done on it. In this paper, firstly, we deduce the number of positions for a beacon to send a packet according to the acreage of ROI (region of interest); and next we present a novel method based on virtual force to arrange the positions in arbitrary ROI; then we apply TSP (travelling salesman problem) algorithm to the positions sequence to obtain the optimal touring path, i.e. the reduced beacon trajectory. When a mobile beacon moves along the touring path, sending RF signals at every position, the sensors in ROI can work out their position with trilateration. Experimental results demonstrate that the localization method, based on the beacon reduced path, is efficient and has flexible accuracy.
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Content subscribing mechanism in P2P streaming based on gamma distribution prediction
GUO Tong-qiang, WENG Jian-guang, ZHUANG Yue-ting
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1983-1989.
https://doi.org/10.1631/jzus.2007.A1983
P2P systems are categorized into tree-based and mesh-based systems according to their topologies. Mesh-based systems are considered more suitable for large-scale Internet applications, but require optimization on latency issue. This paper proposes a content subscribing mechanism (CSM) to eliminate unnecessary time delays during data relaying. A node can send content data to its neighbors as soon as it receives the data segment. No additional time is taken during the interactive stages prior to data segment transmission of streaming content. CSM consists of three steps. First, every node records its historical segments latency, and adopts gamma distribution, which possesses powerful expression ability, to express latency statistics. Second, a node predicts subscribing success ratio of every neighbor by comparing the gamma distribution parameters of the node and its neighbors before selecting a neighbor node to subscribe a data segment. The above steps would not increase latency as they are executed before the data segments are ready at the neighbor nodes. Finally, the node, which was subscribed to, sends the subscribed data segment to the subscriber immediately when it has the data segment. Experiments show that CSM significantly reduces the content data transmission latency.
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Performance of beacon safety message dissemination in Vehicular Ad hoc NETworks (VANETs)
YOUSEFI Saleh, FATHY Mahmood, BENSLIMANE Abderrahim
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 1990-2004.
https://doi.org/10.1631/jzus.2007.A1990
Currently, there is a growing belief that putting an IEEE 802.11-like radio into road vehicles can help the drivers to travel more safely. Message dissemination protocols are primordial for safety vehicular applications. There are two types of safety messages which may be exchanged between vehicles: alarm and beacon. In this paper we investigate the feasibility of deploying safety applications based on beacon message dissemination through extensive simulation study and pay special attention to the safety requirements. Vehicles are supposed to issue these messages periodically to announce to other vehicles their current situation and use received messages for preventing possible unsafe situations. We evaluate the performance of a single-hop dissemination protocol while taking into account the quality of service (QoS) metrics like delivery rate and delay. We realize that reliability is the main concern in beacon message dissemination. Thus, a new metric named effective range is defined which gives us more accurate facility for evaluating QoS in safety applications specifically. Then, in order to improve the performance, the effects of three parameters including vehicle’s transmission range, message transmission’s interval time and message payload size are studied. Due to special characteristics of the safety applications, we model the relationship between communication-level QoS and application-level QoS and evaluate them for different classes of safety applications. As a conclusion, the current technology of IEEE 802.11 MAC layer has still some challenges for automatic safety applications but it can provide acceptable QoS to driver assistance safety applications.
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Implementing VLPR systems based on TMS320DM642
ZHU Le-qing, ZHANG San-yuan, YE Xiu-zi
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 2005-2016.
https://doi.org/10.1631/jzus.2007.A2005
This paper gives a practical schema for using DSP boards to construct Vehicle License Plate Recognition (VLPR) modules that could be embedded in any Intelligent Transportation System (ITS). Using DSP can avoid the heavy investment in dedicated VLPR system and improve the computational power compared to PC software environment. Low cost, high computational power, and high flexibility of DSP provide the License Plate Recognition System (LPRS) an excellent cost-effective solution to execute the major part of the recognition tasks. This paper describes a successful implementation of VLPR system based on Texas Instruments (TI)’s TMS320DM642. The DSP board acquires video (which could be output to a monitor for surveillance) from a camera, captures images from the video, locates and recognizes the license plates in images, and then sends the recognized results and related images after compression to a host PC through the network. Finally, the overall software is optimized according to the features of DM642 chip. Experiments showed that the DSP VLPR system performs well on the local license plates, and that the processing speed and accuracy can meet the requirement of practical applications.
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Visual odometry for road vehicles—feasibility analysis
SOTELO Miguel-angel, GARCÍA Roberto, PARRA Ignacio, FERNÁNDEZ David, GAVILÁN Miguel, ÁLVAREZ Sergio, NARANJO José-eugenio
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(12): 2017-2020.
https://doi.org/10.1631/jzus.2007.A2017
Estimating the global position of a road vehicle without using GPS is a challenge that many scientists look forward to solving in the near future. Normally, inertial and odometry sensors are used to complement GPS measures in an attempt to provide a means for maintaining vehicle odometry during GPS outage. Nonetheless, recent experiments have demonstrated that computer vision can also be used as a valuable source to provide what can be denoted as visual odometry. For this purpose, vehicle motion can be estimated using a non-linear, photogrametric approach based on RAndom SAmple Consensus (RANSAC). The results prove that the detection and selection of relevant feature points is a crucial factor in the global performance of the visual odometry algorithm. The key issues for further improvement are discussed in this letter.
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22 articles
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