set membership identification: A survey

Robustness had become in past years a central issue in system and control theory, focusing the attention of researchers from the study of a single model to the investigation of a set of models, described by a set of perturbations of a “nominal” model. Such a set, often indicated as an uncertainty model set or model set for short, has to be suitably constructed to describe the inherent uncertainty about the system under consideration and to be used for analysis and design purposes. H_∞ identification methods deliver uncertainty model sets in a suitable form to be used by well-established robust design techniques, based on H_∞ or μ optimization methods. The literature on H_∞ identification is now very extensive. In this paper, some of the most relevant contributions related to assumption validation, evaluation of bounds on unmodeled dynamics, convergence analysis and optimality properties of linear, two-stage and interpolatory algorithms are surveyed from a deterministic point of view.     

Asymptotic properties of set membership identification algorithms

This paper addresses the asymptotic worst-case properties of set membership identification (SMID) algorithms. We first present a set membership identification algorithm which can be used with a model structure consisting of parametric and nonparametric uncertainty, as well as output additive disturbances. This algorithm is then studied in the context of asymptotic worst-case behavior. We derive lower bounds on the worst-case achievable identification error measured by the volume, as well as the sum-of-sidelengths of the identified ellipsoidal uncertainty sets. We then show that there exist inputs which can shrink the uncertainty sets to these lower bounds.     

A QFT framework for nonlinear robust stability

The problem of deriving conditions for a stabilizing linear compensator in a uncertain nonlinear control system is addressed, for some types of memoryless nonlinearities like the saturation or the dead zone. The approach is to incorporate to QFT conditions given by the application of harmonic balance and multiplier techniques, providing the designer with a very transparent tool for synthesizing nonlinear stabilizing compensators, balancing between different possible alternatives. Copyright © 2002 John Wiley & Sons, Ltd.     

A synthesis framework for robust gain-scheduling controllers

We present a general framework for the systematic synthesis of robust gain-scheduling controllers by convex optimization techniques and for uncertain dynamical systems described by standard linear fractional representations. We distinguish between linear time-varying parameters, which are assumed to be available online as scheduling parameters for the controller, and genuine uncertainties, not necessarily time-varying, parametric or linear, that are not available online. Under the rough hypothesis that the control channel is not affected by the unmeasurable uncertainties and that the properties of the uncertainties and scheduling variables are captured by suitable families of integral quadratic constraints, this paper reveals how controller synthesis can be turned into a genuine semi-definite program. The design framework is shown to encompass a rich class of concrete scenarios.     

Computational complexity analysis of set membership identification of Hammerstein and Wiener systems

This paper analyzes the computational complexity of set membership identification of Hammerstein and Wiener systems. Its main results show that, even in cases where a portion of the plant is known, the problems are generically NP-hard both in the number of experimental data points and in the number of inputs (Wiener) or outputs (Hammerstein) of the nonlinearity. These results provide new insight into the reasons underlying the high computational complexity of several recently proposed algorithms and point out the need for developing computationally tractable relaxations.     

A framework for robust active super tier systems

The scenario in which services are obtained by combining sub services is of a great importance. Reliability and fault tolerance are important concerns in the design of such distributed systems. This paper proposes a framework for designing robust client–server tier systems. First, we suggest implementing robust tier automata for each tier τ _i used by the processors that the tier contains. The robust tier automata are useful abstractions that allow distribution of the tier’s tasks (and its stubs) in a way that ensures availability, consistency, and recovery in the presence of faults. Then we suggest an active tier framework in which the computation of a user request progresses on several paths in the tier system; those paths may intersect, leaving footprints for each other. And last, we propose the super tier architecture, which correlates equivalent tiers in order to gain more robustness and load balancing. We present and analyze optimistic, pessimistic, and semi-optimistic approaches for computing over the active tier system with super tiers.     

A robust efficient tracing scheme for triangulating trimmed parametric surfaces

An efficient, robust parametric trimmed surface triangulation method is presented. Efficiency is gained during trimmed curve tracing by minimising the number of cells processed. Key feature is the efficient tracing algorithm, and knowledge of orientation of the trimming curves is not required. The method is applicable to NURBS surfaces and operates on the untrimmed surface, constructing a rectangular parametric grid onto which the trimming curves are traced. This approach also minimises the occurrence of degenerate triangles and copes with holes independently of the grid size.     

A syllable-scale framework for language identification

Whilst several examples of segment based approaches to language identification (LID) have been published, they have been typically conducted using only a small number of languages, or varying feature sets, thus making it difficult to determine how the segment length influences the accuracy of LID systems. In this study, phone-triplets are used as crude approximates for a syllable-length sub-word segmental unit. The proposed pseudo-syllabic length framework is subsequently used for both qualitative and quantitative examination of the contributions made by acoustic, phonotactic and prosodic information sources, and trialled in accordance with the NIST 1996 LID protocol. Firstly, a series of experimental comparisons are conducted which examine the utility of using segmental units for modelling short term acoustic features. These include comparisons between language specific Gaussian mixture models (GMMs), language specific GMMs for each segmental unit, and finally language specific hidden Markov models (HMM) for each segment, undertaken in an attempt to better model the temporal evolution of acoustic features. In a second tier of experiments, the contribution of both broad and fine class phonotactic information, when considered over an extended time frame, is contrasted with an implementation of the currently popular parallel phone recognition language modelling (PPRLM) technique. Results indicate that this information can be used to complement existing PPRLM systems to obtain improved performance. The pseudo-syllabic framework is also used to model prosodic dynamics and compared to an implemented version of a recently published system, achieving comparable levels of performance.     

A unified framework for structure identification

We propose a general framework for structure identification, as defined by Dechter and Pearl. It is based on the notion of prime implicate, and handles Horn, bijunctive and affine, as well as Horn-renamable formulas, for which, to our knowledge, no polynomial algorithm has been proposed before. This framework, although quite general, gives good complexity results, and in particular we get for Horn formulas the same running time and better output size than the algorithms previously known.     

A fuzzy set theoretic framework for knowledge-based simulation

Complex systems such as an industrial enterprise operating in a physical, biological, socioeconomic environments generally have many ill defined or imprecisely known parameters which are typically approximated by exact numbers or represented with random variables. Fuzzy set theory is a promising alternative for explicitly treating these aspects of a system. This paper describes a fuzzy set theoretic formalism for knowledge-based simulations. A prototype system is being implemented in Mathematica.     

A robust unsupervised anomaly detection framework

Applied Intelligence - Anomaly detection plays an essential role in monitoring dependable systems and networks such as computer clusters, water treatment systems, sensor networks, etc. However,...     

鲁棒辨识研究的现状

综述了鲁棒辨识问题的研究进展，介绍 了鲁棒辨识问题产生的背景，对各种不同的辨识方法进行了评述，并指出各自的特点，最后总结了今后的发展方向。     

A robust statistical set of features for Amazigh handwritten characters

The main problem in the handwritten character recognition systems (HCR) is to describe each character by a set of features that can distinguish it from the other characters. Thus, in this paper, we propose a robust set of features extracted from isolated Amazigh characters based on decomposing the character image into zones and calculate the density and the total length of the histogram projection in each zone. In the experimental evaluation, we test the proposed set of features, to show its performance, with different classification algorithms on a large database of handwritten Amazigh characters. The obtained results give recognition rates that reach 99.03% which we presume good and satisfactory compared to other approaches and show that our proposed set of features is useful to describe the Amazigh characters.     

From set membership to group membership: a separation of concerns

We revisit the well-known group membership problem and show how it can be considered a special case of a simple problem, the set membership problem. In the set membership problem, processes maintain a set whose elements are drawn from an arbitrary universe: They can request the addition or removal of elements to/from that set, and they agree on the current value of the set. Group membership corresponds to the special case where the elements of the set happen to be processes. We exploit this new way of looking at group membership to give a simple and succinct specification of this problem and to outline a simple implementation approach based on the state machine paradigm. This treatment of group membership separates several issues that are often mixed in existing specifications and/or implementations of group membership. We believe that this separation of concerns greatly simplifies the understanding of this problem.     

A set of standard modeling commands for the history-based parametric approach

The current version of STEP standard cannot exchange the parametric information of CAD models. Only pure boundary representations that cannot be parametrically edited are transferable [Geometric Modeling: Theory and Practice (1997)]. There are two approaches for the exchange of design intents such as parameters, features, and constraints. The first is an explicit approach based on constraints between pre-defined parameters and features. The second is a procedural approach based on the sequence of operations issued to construct the models. The authors have previously proposed a macro-parametric approach [International Journal of CAD/CAM 2 (2002) 23], which is a variation of the procedural approach. In this approach, CAD models can be exchanged in the form of macro files, which include the history of modeling commands. To exchange CAD models using the macro-parametric approach, a set of standard modeling commands should be defined. This paper introduces a set of standard commands and explains the process of developing the set.     

A robust software watermarking framework using shellcode

Multimedia Tools and Applications - Watermarks have long been applied to ensure the authenticity of media contents. Computer software is an intellectual outcome in the digital domain. Therefore, it...     

A framework for multiple robust explicit MPC controllers for linear systems

This article presents a multi-mode explicit controller for constrained linear systems with bounded disturbances using a switching strategy based on Model Predictive Control (MPC). In the proposed approach, the system switches among several MPC controllers having different performance levels. The switching is done so as to achieve increasing levels of performance as time evolves, reaching the desired controller in finite time steps. The conditions needed for switching and robust convergence of the multi-mode MPC controllers are provided. Compared with standard robust explicit MPC implementations, the proposed approach has the flexibility of having a large domain of attraction, a good asymptotic behaviour and a small number of partitions.