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Adaptive Technique (adaptive + technique)
Selected AbstractsIndirect adaptive control of a class of marine vehiclesINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 4 2010Yannick Morel Abstract A nonlinear adaptive framework for bounded-error tracking control of a class of non-minimum phase marine vehicles is presented. The control algorithm relies on a special set of tracking errors to achieve satisfactory tracking performance while guaranteeing stable internal dynamics. First, the design of a model-based nonlinear control law, guaranteeing asymptotic stability of the error dynamics, is presented. This control algorithm solves the tracking problem for the considered class of marine vehicles, assuming full knowledge of the system model. Then, the analysis of the zero-dynamics is carried out, which illustrates the efficacy of the chosen set of tracking errors in stabilizing the internal dynamics. Finally, an indirect adaptive technique, relying on a partial state predictor, is used to address parametric uncertainties in the model. The resulting adaptive control algorithm guarantees Lyapunov stability of the errors and parameter estimates, as well as asymptotic convergence of the errors to zero. Numerical simulations illustrate the performance of the adaptive algorithm. Copyright © 2009 John Wiley & Sons, Ltd. [source] Interactive magnetic resonance cholangiography (MRC) with adaptive averaging,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2006Martin J. Graves MSc Abstract Purpose To implement and evaluate a technique for adaptively averaging 2D magnetic resonance cholangiography (MRC) images obtained using an interactive imaging system with a view to improving image quality at reduced fields of view (FOVs). Materials and Methods Images were obtained using an interactive implementation of a single-shot half-Fourier rapid acquisition with relaxation enhancement (RARE) technique. Software was developed for adaptively averaging images, and an evaluation was performed in a phantom and a cohort of 10 patients referred for standard MRC. Adaptively averaged and standard single-shot MRC images were evaluated with respect to their ability to demonstrate the common bile duct and main left and right intrahepatic duct branches. Results In all patient studies there was no difference in the ability of either the adaptive technique or the standard single-shot method to demonstrate the common bile duct and the main left and right intrahepatic duct branches. However, in seven of the 10 patient studies the adaptive technique provided better visualization of the peripheral bile duct system (P = 0.035; sign test). There was no difference in the diagnostic confidence of the two techniques (P = 0.32, Wilcoxon signed-rank test). Conclusion Adaptive averaging of MRC images obtained using an interactive imaging paradigm significantly improves visualization of peripheral intrahepatic ducts. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Lempel-Ziv compression of highly structured documentsJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 4 2007Joaquín Adiego The authors describe Lempel-Ziv to Compress Structure (LZCS), a novel Lempel,Ziv approach suitable for compressing structured documents. LZCS takes advantage of repeated substructures that may appear in the documents, by replacing them with a backward reference to their previous occurrence. The result of the LZCS transformation is still a valid structured document, which is human-readable and can be transmitted by ASCII channels. Moreover, LZCS transformed documents are easy to search, display, access at random, and navigate. In a second stage, the transformed documents can be further compressed using any semistatic technique, so that it is still possible to do all those operations efficiently; or with any adaptive technique to boost compression. LZCS is especially efficient in the compression of collections of highly structured data, such as extensible markup language (XML) forms, invoices, e-commerce, and Web-service exchange documents. The comparison with other structure-aware and standard compressors shows that LZCS is a competitive choice for these type of documents, whereas the others are not well-suited to support navigation or random access. When joined to an adaptive compressor, LZCS obtains by far the best compression ratios. [source] ADAPTIVE VARIABLE STRUCTURE CONTROL OF UNCERTAIN SYSTEMS CONTAINING UNKNOWN GAIN REDUCTION TOLERANCEASIAN JOURNAL OF CONTROL, Issue 1 2007Jun-Juh Yan ABSTRACT In this paper, an adaptive variable structure controller (AVSC) is presented for a class of uncertain systems subjected to input nonlinearities. Using an adaptive technique, an AVSC is then proposed to ensure the asymptotical convergence of the switching quantity even without involving the bound of the gain reduction tolerance. On the switching surface, the investigated uncertain system still bears the insensitivity to the uncertainties and disturbances as the systems with linear input. An illustrative example is given to demonstrate the effectiveness of the proposed AVSC design method. [source] | ||||||||||