To mitigate capital equipment investments and enhance product quality, semiconductor manufactures are turning to advanced process control (APC) methods. With the objective of facilitating APC, this paper investigates ...
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To mitigate capital equipment investments and enhance product quality, semiconductor manufactures are turning to advanced process control (APC) methods. With the objective of facilitating APC, this paper investigates a methodology for real-time malfunction diagnosis of reactive ion etching (RIE) employing two types of in situ metrology: optical emission spectroscopy (OES) and residual gas analysis (RGA). Based on metrology data, time series neural networks (TSNNs) are trained to generate evidential belief for potential malfunctions in real time, and Dempster-Shafer (D-S) theory is adopted for evidential reasoning. Successful malfunction diagnosis is achieved, with only a single missed alarm and a single false alarm occurring out of 21 test runs when both sensors are used in tandem. From the results, we conclude that the OES and RGA sensors, in conjunction with the TSNN models, can be effectively used for RIE monitoring and diagnosis. Furthermore, D-S theory is shown to be an appropriate inference methodology.
This paper provides a comparison between two types of linear variable reluctance motors. The coupled flux path configuration has a non-diagonal inductance matrix and is operated with synchronous excitation, whereas th...
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This paper provides a comparison between two types of linear variable reluctance motors. The coupled flux path configuration has a non-diagonal inductance matrix and is operated with synchronous excitation, whereas the uncoupled flux path configuration has a diagonal inductance matrix and is operated with switched excitation. Constrained optimization methods are used to investigate the force production capabilities of both magnetic configurations. The specific measure of performance emphasized here is the ratio of current-limited ripple-free force to moving mass or, equivalently, the maximum achievable fully controllable acceleration. This focus is motivated by robotics applications, e.g. component placement machines used in elec.ronics assembly.
Presented in this paper is an extension to previous work on observer-based sensorless control of synchronous reluctance motors. The extensions include a systematic observer gain calculation that facilitates the use of...
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Presented in this paper is an extension to previous work on observer-based sensorless control of synchronous reluctance motors. The extensions include a systematic observer gain calculation that facilitates the use of gain sch.duling to improve the transient response of the observer over a wide speed range and improve the low speed performance of the closed-loop sensorless controller. Laboratory experiments are used to demonstrate these improvements.
Imperceptibility and robustness against attacks are the foremost qualities desired in any image watermarking sch.me. In this work, a contrast based image watermarking algorithm is proposed based on a human visual syst...
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ISBN:
(纸本)0780382439
Imperceptibility and robustness against attacks are the foremost qualities desired in any image watermarking sch.me. In this work, a contrast based image watermarking algorithm is proposed based on a human visual system model. The algorithm is designed using concepts from attack modelling, and is tested against different attacks. The presented results show that the algorithm is robust to removal based attacks.
Acquisition of very weak GPS signals requires long coherent and incoherent integration. Increasing the coherent, or predetection, integration time (PIT) improves sensitivity, but is limited because of the unknown data...
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Acquisition of very weak GPS signals requires long coherent and incoherent integration. Increasing the coherent, or predetection, integration time (PIT) improves sensitivity, but is limited because of the unknown data and bit edges. Incoherent integration is less sensitive, because of squaring loss. Two algorithms are developed to use a PIT which is a multiple of one data bit interval, without requiring assisting information. Both algorithms estimate the most likely data bit combination and use this to subsequently reverse the data signs over each PIT and synchronize the start of each PIT. The algorithms differ in the method of coherent integration. One uses circular correlation (FFT/IFFT), the other uses double block zero padding (DBZP). Circular correlation requires larger numbers of Doppler bins as the PIT is increased. In contrast, DBZP does not use Doppler bins, but suffers from loss because it does not account for the Doppler effect on the code duration. Consequently, the varying delay between the received signal and the replica will cause subsequent incoherent integrations to be added at the wrong delay. Solutions have been developed for each of these problems. In the case of circular correlation, a small PIT is used initially and after few steps the Doppler bins which have the lowest likelihood are eliminated. Thus, the PIT can be increased without increasing the total number of Doppler bins. In the case of DBZP, an approach is developed to compensate for the change in the code duration and relative delay, with only a small increase in the processing requirement. Simulations indicate that both of these algorithms can acquire signals below 15 dB-Hz. The problem of acquiring weak signals in presence of strong interfering signals is also addressed.
A closed-loop MIMO-OFDM transmitter can exploit channel knowledge using eigenbeamforming to create M N parallel channels, where M is the number of antennas at both ends and N is the number of OFDM tones. We find that ...
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ISBN:
(纸本)0780379543
A closed-loop MIMO-OFDM transmitter can exploit channel knowledge using eigenbeamforming to create M N parallel channels, where M is the number of antennas at both ends and N is the number of OFDM tones. We find that the penalty due to a flat-frequency constraint, which forces each tone to convey the same amount of information, becomes negligible as M grows. We propose low-complexity bit-allocation strategies by combining the flat-frequency constraint with previously-reported spatial bit-allocation strategies. A fixed (nonadaptive) allocation across space and frequency performs remarkably well with M as small as 4.
In a network with quality of service (QoS) support, pricing is an effective means of dealing with congestion control and revenue generation. In the Internet, the needs of the customers and their applications are const...
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In a network with quality of service (QoS) support, pricing is an effective means of dealing with congestion control and revenue generation. In the Internet, the needs of the customers and their applications are constantly evolving. An auction based algorithm is the best choice for this environment because it needs minimal a priori information. In this paper, we propose an auction based pricing algorithm which lets customers choose the price as well as the service required, and in which the service provider decides on the admission price threshold and the service level of the differentiated service provided. We then investigate the system's adaptive behavior by simulating it in various environments and situations.
The high frequency signal injection method in the sensorless position control of Active Magnetic Bearings (AMB), has some merits such in that there is no steady-state error in the estimated position and can control th...
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The high frequency signal injection method in the sensorless position control of Active Magnetic Bearings (AMB), has some merits such in that there is no steady-state error in the estimated position and can control the amplitude of the signals used for position estimation. In this paper, a method to inject a high frequency signal and to process the signal to obtain the position of the rotor has been proposed. In this method, all signal processing is done in the digital domain, and in contrast to the analog method, there is no offset nor are there any continuous tuning problems. The proposed method does not need additional hardware for signal injection and signal processing. The PWM inverter, which is used to regulate coil current, generates the injection signal, and the DSP, which is used to control the system, performs signal processing in a normal sampling cycle. The experimental results show reasonable performance with regard to the 4-degree-of-freedom control of rotor position, while rotating at 30,000 [r/min].
We describe an approach and our experiences in applying federated simulation techniques to create large-scale parallel simulations of computer networks. Using the federated approach, the topology and the protocol stac...
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We describe an approach and our experiences in applying federated simulation techniques to create large-scale parallel simulations of computer networks. Using the federated approach, the topology and the protocol stack of the simulated network is partitioned into a number of submodels, and a simulation process is instantiated for each one. Runtime infrastructure software provides services for interprocess communication and synchronization (time management). We first describe issues that arise in homogeneous federations where a sequential simulator is federated with itself to realize a parallel implementation. We then describe additional issues that must be addressed in heterogeneous federations composed of different network simulation packages, and describe a dynamic simulation backplane mechanism that facilitates interoperability among different network simulators. Specifically, the dynamic simulation backplane provides a means of addressing key issues that arise in federating different network simulators: differing packet representations, incomplete implementations of network protocol models, and differing levels of detail among the simulation processes. We discuss two different methods for using the backplane for interactions between heterogeneous simulators: the cross-protocol stack method and the split-protocol stack method. Finally, results from an experimental study are presented for both the homogeneous and heterogeneous cases that provide evidence of the scalability of our federated approach on two moderately sized computing clusters. Two different homogeneous implementations are described: Parallel / Distributed ns (pdns) and the Georgia Tech Network Simulator (GTNetS). Results of a heterogeneous implementation federating ns with GloMoSim are described. This research demonstrates that federated simulations are a viable approach to realizing efficient parallel network simulation tools.
A modified DCS half-bridge DC-DC converter is proposed to achieve soft switching of all switches and to reduce the leakage-inductance-related power losses. The theoretical analysis and experimental results show that t...
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A modified DCS half-bridge DC-DC converter is proposed to achieve soft switching of all switches and to reduce the leakage-inductance-related power losses. The theoretical analysis and experimental results show that the proposed topology achieves high efficiency at high switching frequencies.
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