Global adaptive output regulation of a class of nonlinear systems with nonlinear exosystems

This paper deals with global output regulation with nonlinear exosystems for a class of uncertain nonlinear output feedback systems. The circle criterion is exploited for the internal model design to accommodate the nonlinearities in the exosystems, and the explicit conditions are given for the exosystems such that the proposed internal model design can be applied. The uncertainties of the output feedback systems are in the form of unknown constant parameters, and adaptive control techniques are used to ensure the global stability of the proposed control design for output regulation.     

Maximum likelihood identification of noisy input-output models

This work deals with the identification of errors-in-variables models corrupted by white and uncorrelated Gaussian noises. By introducing an auxiliary process, it is possible to obtain a maximum likelihood solution of this identification problem, by means of a two-step iterative algorithm. This approach allows also to estimate, as a byproduct, the noise-free input and output sequences. Moreover, an analytic expression of the finite Cràmer-Rao lower bound is derived. The method does not require any particular assumption on the input process, however, the ratio of the noise variances is assumed as known. The effectiveness of the proposed algorithm has been verified by means of Monte Carlo simulations.     

Principles of 2-sliding mode design

Second-order sliding modes are used to keep exactly a constraint of the second relative degree or just to avoid chattering, i.e. in the cases when the standard (first order) sliding mode implementation might be involved or impossible. Design of a number of new 2-sliding controllers is demonstrated by means of the proposed homogeneity-based approach. A recently developed robust exact differentiator being applied, robust output-feedback controllers with finite-time convergence are produced, capable to control any general uncertain single-input-single-output process with relative degree 2. An effective simple procedure is developed to attenuate the 1-sliding mode chattering. Simulation of new controllers is presented.     

Control of dynamic keyhole welding process

Weld joint penetration control is a basic research topic in the welding research community. The authors propose using an innovative plasma arc welding process referred to as the quasi-keyhole process to achieve less application-dependent weld joint penetration sensing and control. To control the quasi-keyhole process, the peak current and keyhole sustaining current are selected as the control variables to maintain the keyhole establishment and sustaining periods at desired values. The dynamic quasi-keyhole process is approximated by a linear model with interval parameters. A control algorithm has been developed for the multivariable interval quasi-keyhole process based on a predictive control algorithm for interval SISO models. Experiments have been conducted to test the effectiveness of the control system developed.     

Estimation of skew angles for scanned documents based on piecewise covering by parallelograms

We propose a fast and robust skew estimation method for scanned documents that estimates skew angles based on piecewise covering of objects, such as textlines, figures, forms, or tables. The method first divides a document image into a number of non-overlapping slabs in which each object is covered by parallelograms. It then estimates the skew angle based on these parallelograms or, equivalently, their complementary regions. Putting our method to a systematic test and comparing it with some alternatives, we find that it yields favorable results in terms of accuracy, sensitivity to non-textual objects, effectiveness in dealing with documents of unspecified reading order, and computational efficiency. Some work is also conducted to find an effective way to further shorten its computation time at the expense of an extremely small loss of accuracy.     

A discriminant analysis using composite features for classification problems

In this paper, we propose a new discriminant analysis using composite features for pattern classification. A composite feature consists of a number of primitive features, each of which corresponds to an input variable. The covariance of composite features is obtained from the inner product of composite features and can be considered as a generalized form of the covariance of primitive features. It contains information on statistical dependency among multiple primitive features. A discriminant analysis (C-LDA) using the covariance of composite features is a generalization of the linear discriminant analysis (LDA). Unlike LDA, the number of extracted features can be larger than the number of classes in C-LDA, which is a desirable property especially for binary classification problems. Experimental results on several data sets indicate that C-LDA provides better classification results than other methods based on primitive features.     

Improvement of jitter transfer characteristics of a 9.95328 Gb/s data recovery DLL using saw filter

This paper presents a design of a high-speed data recovery circuit for non return zero (NRZ) data transmission using delay-locked loop (DLL) with SAW filter. The jitter generation of the circuit is decreased by adjusting the loop gain in DLL whereas surface acoustic wave (SAW) filter with low centered frequency (f_c) improves the jitter transfer function of DLL. It is seen that the circuit using SAW filter of f_c = 1.24416 GHz and Q = 1000 provides the cut off frequency of about 600 kHz which is ∼10 times lower than that of conventional DLL circuit.     

Fraternities and ITexts: Composing in the post-industrial turn

Web sites are a ubiquitous Internet genre employed by student organizations. This article investigates the role of a web site in an Interfraternity Council at a large midwestern university in the United States. The web site is examined through the work of Anthony Giddens, specifically his structuration theory, and the recent research on ITexts. In turn, the composing process required for such IText creation and maintenance is considered in light of the complicated network of forces and restraints surrounding the Interfraternity Council and the web site. By positioning the web site as an IText, the article revisits the field's understanding of genre as well as the knowledge creation surrounding such genres. Ultimately, the article contends that it may be in everyday (I)texts, such as organization web sites, where the intertwined shifts to post-industrialism and an emphasis on multiliteracies are most recognizable and accessible for teachers of writing.     

Efficient registration of optical and infrared images via modified Sobel edging for plant canopy temperature estimation

Automatic optical and infrared (IR) image registration is a crucial requirement in the estimation of plant canopy temperature. The latter is used to compute the plant water stress status which can potentially be applied to an automated control system for optimal crop irrigation management. Due to the nature of image sources and plant scene, it is difficult to find enough common features between the pair of images to register them using a simple method. In this paper an improved registration algorithm is described, where a modified Sobel edge detector is adopted and a variable resolution scheme is applied. The algorithm can improve the registration efficiency considerably compared to our previous developed registration method. Experiment results show that the modified algorithm can achieve the same registration accuracy and a better success rate compared to that from the original algorithm with a substantial reduction of computational complexity.