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Efficient fault tolerant estimation using the IMM methodology

IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2007年第2期43卷 492-508页

作者： Rapoport, Ilia Oshman, Yaakov Technion Israel Inst Technol Dept Aerosp Engn IL-32000 Haifa Israel

Space systems are characterized by a low-intensity process noise resulting from uncertain forces and moments. In many cases, their scalar measurement channels can be assumed to be independent, with one-dimensional internal dynamics. The nominal operation of these systems can be severely damaged by faults in the sensors. A natural method that can be used to yield fault tolerant estimates of such systems is the interacting multiple model (IMM) filtering algorithm, which is known to provide very accurate results. However, having been derived for a general class of systems with switching parameters, the IMM filter does not utilize the independence of the measurement errors in different channels, nor does it exploit the fact that the process noise is of low intensity. Thus, the implementation of the IMM in this case is computationally expensive. A new estimation technique is proposed herein, that explicitly utilizes the aforementioned properties. In the resulting estimation scheme separate measurement channels are handled separately, thus reducing the computational complexity. It is shown that, whereas the IMM complexity is exponential in the number of fault-prone measurements, the complexity of the proposed technique is polynomial. A simulation study involving spacecraft attitude estimation is carried out. This study shows that the proposed technique closely approximates the full-blown IMM algorithm, while requiring only a modest fraction of the computational cost.

关键词： FAULT tolerance (Engineering) ESTIMATION theory NOISE ELECTRONIC measurements computer algorithms FILTERING software computer simulation GAUSSIAN processes AEROSPACE engineering

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A criterion for atomicity revisited

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ACTA INFORMATICA 2007年第2期44卷 123-151页

作者： Hesselink, Wim H. Univ Groningen Dept Math & Comp Sci NL-9700 AV Groningen Netherlands

Concurrent and reactive programs are specified by their behaviours in the presence of a nondeterministic environment. In a natural way, this gives a specification (ARW) of an atomic variable in the style of Abadi and Lamport. Several implementations of atomic variables by lower level primitives are known. A few years ago, we formulated a criterion to prove the correctness of such implementations. The proof of correctness of the criterion itself was based on Lynch's definition of atomicity by serialization points. Here, this criterion is reformulated as a specification HRW in the formal sense. Simulations from HRW to ARW and vice versa are constructed. These now serve as a constructive proof of correctness of the criterion. Eternity variables are used in the simulation from HRW to ARW. We propose so-called gliding simulations to deal with the problems that appear when occasionally the concrete implementation needs fewer steps than the abstract specification.

关键词： PROGRAMMING languages (Electronic computers) VARIABLES (Mathematics) MATHEMATICAL programming algorithms computer algorithms

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On selection of nonmultiplicative prolongations in computation of janet bases

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PROGRAMMING AND computer SOFTWARE 2007年第3期33卷 147-153页

作者： Gerdt, V. P. Blinkov, Yu. A. Joint Inst Nucl Res Informat Technol Lab Dubna 141980 Russia Saratov NG Chernyshevskii State Univ Dept Math & Mech Saratov 410071 Russia

We consider three modifications of our basic involutive algorithm for computing polynomial Janet bases. These modifications, which are related to degree-compatible monomial orders, yield specific selection strategies for nonmultiplicative prolongations. Using a standard database of benchmarks designed for testing programs computing Grobner bases, we compare these algorithmic modifications (in terms of their efficiency) with Faugere's F-4 algorithm, which is built in the Magma computer algebra system.

关键词： FUNCTIONS (Mathematics) POLYNOMIALS computer mathematics algorithms computer algorithms computer programming ALGEBRA

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Elliptical-Tukey chirp signal for high-resolution, air-coupled ultrasonic imaging

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 2007年第8期54卷 1530-1540页

作者： Pallav, Prakash Gan, Tat Hean Hutchins, David A. Univ Warwick Sch Engn Coventry CV4 7AL W Midlands England

A new signal processing method, which uses a modified chirp signal for air-coupled ultrasonic imaging, is described. A combination of the elliptical and Tukey window functions has been shown to give a better performance than the Harming windowing used in most pulse-compression algorithms for air-coupled applications. The elliptical-Tukey chirp signal provides an improvement in both the resolution of images and signal-to-noise ratios. In addition, this type of signal also reduces the level of signal voltages required to drive the source transducer while maintaining the performance of the system. This approach, thus, may have wide interest in all forms of wide bandwidth ultrasonic imaging.

关键词： ULTRASONIC imaging SIGNAL processing WINDOWS (Graphical user interfaces) computer algorithms SIGNAL-to-noise ratio TRANSDUCERS BANDWIDTHS

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Randomized algorithms for 3-SAT

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THEORY OF COMPUTING SYSTEMS 2007年第3期40卷 249-262页

作者： Hofmeister, Thomas Schoening, Uwe Schuler, Rainer Watanabe, Osamu Univ Dortmund D-44221 Dortmund Germany Univ Ulm Abt Theoret Informat D-89069 Ulm Germany Tokyo Inst Technol Dept Math & Comp Sci Tokyo 1528552 Japan

In [S1] Schoning proposed a simple yet efficient randomized algorithm for solving the k-SAT problem. In the case of 3-SAT, the algorithm has an expected running time of poly(n) center dot (4/3)(n) = 0(1.334(n)). In this paper we present randomized algorithms and show that one of them has 0(1.3302(n)) expected running time, improving Schoning's algorithm. (Note. At this point, the fastest randomized algorithm for 3-SAT is the one given by Iwama and Tamaki [IT] that runs in 0(1.324(n)).)

关键词： algorithms computer science -- Study & teaching ARITHMETIC -- Foundations computer programming computer algorithms

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An investigation on the application of predictive control for controlling screw position and velocity on an injection molding machine

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POLYMER ENGINEERING AND SCIENCE 2007年第4期47卷 390-399页

作者： Dubay, Rickey Pramujati, Bambang Han, Jianguo Strohmaier, Franz Univ New Brunswick Dept Mech Engn Fredericton NB E3B 5A3 Canada Sepuluh Nopember Inst Technol Dept Mech Engn Surabaya 60111 East Java Indonesia Engel Canada Inc Guelph ON N1K 1C2 Canada

Injection velocity is one of the key parameters in the injection molding process that has significant effect on part quality, influencing common problems, such as flashing and short shots. Different products require specific molding conditions, including mold and melt temperatures, velocity profiles, and polymers, making the injection velocity dynamics vary significantly and difficult for high precision velocity control. Two predictive controllers were developed to control the screw injection velocity. The first approach uses a position sensor as feedback and a simplified predictive controller to track an injection velocity setpoint profile. The controller was developed and implemented utilizing single-step change and multistep change open loop tests. The second strategy uses a multimodel dynamic matrix predictive controller to overcome the nonlinear characteristics of the injection velocity dynamics as the mold is being filled. Velocity feedback is provided by high speed processing of the position analog signal. This approach utilizes several open loop injection velocity profiles to generate corresponding dynamic matrices for the controller. As a result, this controller is modified or retuned automatically when setpoint changes in injection velocity occur, as well as when using different polymers and molds. The close loop results for both simulations and real time control have demonstrated that the two predictive controllers provided good setpoint tracking performance for wide ranging position and velocity profiles.

关键词： DEPENDENT ADAPTIVE CONTROLLER OPTIMAL ANTICIPATORY CONTROL RAM VELOCITY CONTROL ALGORITHM FILLING VELOCITY MODEL VELOCITY PROFILING Injection molding position sensor setpoint Controllers Predictive controllers Predictive control Injections filling velocity RAM VELOCITY OPEN-LOOP computer algorithms

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A general control algorithm for cooling towers in cooling plants with electric and/or gas-driven chillers

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HVAC&R RESEARCH 2007年第4期13卷 581-598页

作者： Braun, James E. Purdue Univ Ray W Herrick Labs W Lafayette IN 47907 USA

A hybrid chiller plant employs a combination of chillers that are "powered" by electricity and natural gas. This paper presents an algorithm for determining cooling tower fan settings in hybrid plants in response to loadings on individual chillers. Parameters of the algorithm are evaluated using design information for the chillers and cooling tower fans. In addition to reducing operating costs, use of the open-loop control strategy simplifies the control and improves the stability of the tower control compared with the use of a constant condenser water supply or approach to wet-bulb. Simulated plant cooling costs associated with the algorithm were compared with costs for optimized settings and were within 1% of the minimum costs. The control method is general, in the sense that it also applies to cooling plants that have all electric or all natural gas chillers.

关键词： GAS DRIVE control strategy algorithms Control Methods COOLING EQUIPMENT CHILLER Water cooling towers Manufacturing costs computer algorithms Bulb (plant) Electricity

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Active control of repetitive transient noise

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JOURNAL OF SOUND AND VIBRATION 2007年第3-5期307卷 513-526页

作者： Pinte, G. Desmet, W. Sas, P. Katholieke Univ Leuven Dept Mech Engn B-3001 Heverlee Belgium

This paper presents the possibilities of active noise control techniques to reduce repetitive transient noise. Although there is a significant difference in nature between periodic and transient noise, up till now no specific research on active noise control of transient noise was reported. The presented research focuses on the development of control algorithms, dedicated for the control of repetitive transient noise. The effectiveness of the control algorithms is demonstrated for the reduction of impulse noise in a duct by a secondary loudspeaker. A linear time-invariant feedback controller is developed to drive this loudspeaker. The performance of this time-invariant controller is limited for several reasons: time variance of the system parameters, limited controller bandwidth, nonlinearities, etc. However, when the noise consists of successive impulsive sounds that exhibit a repetitive character, it is possible to extend the developed time-invariant feedback controller with a learning behaviour, based on the additional information about the repetitiveness. At each pulse, the control signal for the secondary loudspeaker can be adapted on the basis of the residual noise at the previous pulses, such that the radiated noise is reduced. This latter control technique, called iterative learning control, can significantly increase the performance of a feedback active noise control system. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： ITERATIVE LEARNING CONTROL FEEDBACK-CONTROL IMPACT NOISE SOUND active control transient noise Iterative learning control system parameter feedback control computer algorithms Active noise control time-invariant Learning behavior Control technology feedback controller SOUND Repetitive residual noise

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Analytic performance bounds on estimates of scattering center parameters

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2007年第2期43卷 813-826页

作者： Zhou, Jianxiong Zhao, Hongzhong Sri, Zhiguang Fu, Qiang Natl Univ Def Technol Dept 4 ATR Lab Changsha 410073 Peoples R China

Cramer-Rao bounds (CRBs) on the estimates of the main scattering center parameters, i.e., the position, intensity and geometry type, are presented in analytic forms. The resolution limit for wideband radar and the SNR threshold for the correct identification of the geometry type parameter of scattering centers are further deduced. Though the results are obtained from the CRB matrix for damped exponentials;(DE) after many approximations and simplifications, their validity and adaptability for geometric theory of diffraction (GTD) based scattering center model have been verified both numerically and experimentally.

关键词： RADAR SCATTERING (Physics) MATRICES OPTICAL diffraction ESTIMATION theory EXPONENTIAL functions computer algorithms MONTE Carlo method BROADBAND communication systems

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Single-pass die-to-database tritone reticle inspection

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SOLID STATE TECHNOLOGY 2007年第5期50卷 56-60页

作者： Heumann, Jan Reese, Bryan Schmidt, Norbert AMTC Dresden Germany KLA Tencor Corp San Jose CA USA

Wafer fabs are under constant pressure to deliver semiconductor products as quickly as possible to an eagerly awaiting consumer market. As a result, mask suppliers are often required to reduce their delivery time for high-end reticles used in the fabrication of silicon wafers. By reducing the optical inspection time (a critical step needed to ensure no defects are present within the designed mask patterns), precious manufacturing time can be saved. This time savings is especially important for tritone reticles that require extra manufacturing and inspection steps over traditional binary masks. By using a recently developed reticle inspection system, database optical inspection of tritone reticles can be achieved in nearly half the time previously needed.

关键词： ENGINEERING inspection SEMICONDUCTOR wafers DATABASES computer algorithms

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