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256. Robust observer-based fault estimation and accommodation of discrete-time piecewise linear systems

Author

Tabatabaeipour, Mojtaba, Bak, Thomas, Tabatabaeipour, Mojtaba, and Bak, Thomas

Abstract

In this paper a new integrated observer-based fault estimation and accommodation strategy for discrete-time piecewise linear (PWL) systems subject to actuator faults is proposed. A robust estimator is designed to simultaneously estimate the state of the system and the actuator fault. Then, the estimate of fault is used to compensate for the effect of the fault. By using the estimate of fault and the states, a fault tolerant controller using a PWL state feedback is designed. The observer-based fault-tolerant controller is obtained by the interconnection of the estimator and the state feedback controller. We show that separate design of the state feedback and the estimator results in the stability of the overall closed-loop system. In addition, the input-to-state stability (ISS) gain for the closed-loop system is obtained and a procedure for minimizing it is given. All of the design conditions are formulated in terms of linear matrix inequalities (LMI) which can be solved efficiently. Also, performance of the estimator and the state feedback controller are minimized by solving convex optimization problems. The efficiency of the method is demonstrated by means of a numerical example.

Published
2013

257. Lecture Notes:Estimation and Sensor Fusion

Author

Bak, Thomas

Abstract

This note discusses multi-sensor fusion. Through sensor fusion we may combine readings from different sensors, remove inconsistencies and combine the information into one coherent structure. This kind of processing is a fundamental feature of all animal and human navigation, where multiple information sources such as vision, hearing and balance are combined to determine position and plan a path to a goal. While the concept of data fusion is not new, the emergence of new sensors, advanced processing techniques, and improved processing hardware make real-time fusion of data increasingly possible. Despite advances in electronic components, however, developing data processing applications such as automatic guidance systems has proved difficult. Systems that are in direct contact and interact with the real world, require reliable and accurate information about their environment. This information is acquired using sensors, that is devices that collect data about the world around them. The ability of one isolated device to provide accurate reliable data of its environment is extremely limited as the environment is usually not very well defined in addition to sensors generally not being a very reliable interface. Sensor fusion seeks to overcome the drawbacks of current sensor technology by combining information from many independent sources of limited accuracy and reliability to give information of better accuracy and reliability. This makes the system less vulnerable to failures of a single component and generally provide more accurate information. In addition several readings from the same sensor are combined, making the system less sensitive to noise and anomalous observations

Published
2000

264. Delaying Onset of Dementia: Are Two Languages Enough?

Author

Freedman, Morris, primary, Alladi, Suvarna, additional, Chertkow, Howard, additional, Bialystok, Ellen, additional, Craik, Fergus I. M., additional, Phillips, Natalie A., additional, Duggirala, Vasanta, additional, Raju, Surampudi Bapi, additional, and Bak, Thomas H., additional

Published
2014
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267. Studying synapses in human brain with array tomography and electron microscopy

Author

Kay, Kevin R, primary, Smith, Colin, additional, Wright, Ann K, additional, Serrano-Pozo, Alberto, additional, Pooler, Amy M, additional, Koffie, Robert, additional, Bastin, Mark E, additional, Bak, Thomas H, additional, Abrahams, Sharon, additional, Kopeikina, Katherine J, additional, McGuone, Declan, additional, Frosch, Matthew P, additional, Gillingwater, Thomas H, additional, Hyman, Bradley T, additional, and Spires-Jones, Tara L, additional

Published
2013
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273. Bilingualism, social cognition and executive functions: A tale of chickens and eggs.

Author

Cox, Simon R., Bak, Thomas H., Allerhand, Michael, Redmond, Paul, Starr, John M., Deary, Ian J., and MacPherson, Sarah E.

Subjects
*BILINGUALISM, *SOCIAL perception, *EXECUTIVE function, *COGNITIVE ability, *MONOLINGUALISM, *SOCIAL classes
Abstract

The influence of bilingualism on cognitive functioning is currently a topic of intense scientific debate. The strongest evidence for a cognitive benefit of bilingualism has been demonstrated in executive functions. However, the causal direction of the relationship remains unclear: does learning other languages improve executive functions or are people with better executive abilities more likely to become bilingual? To address this, we examined 90 male participants of the Lothian Birth Cohort 1936; 26 were bilingual, 64 monolingual. All participants underwent an intelligence test at age 11 years and were assessed on a wide range of executive and social cognition tasks at age 74. The only notable differences between both groups were found for the Simon Effect (which indexes stimulus-response conflict resolution; β =−.518, p =0.025) and a trend effect for the Faux Pas task (a measure of complex theory of mind; ToM, β =0.432, p =0.060). Controlling for the influence of childhood intelligence, parental and own social class significantly attenuated the bilingual advantage on the Faux Pas test ( β =0.058, p =0.816), whereas the Simon task advantage remained ( β =−.589, p =0.049). We find some weak evidence that the relationship between bilingualism and cognitive functions may be selective and bi-directional. Pre-existing cognitive and social class differences from childhood may influence both ToM ability in older age and the likelihood of learning another language; yet, bilingualism does not appear to independently contribute to Faux Pas score. Conversely, learning a second language is related to better conflict processing, irrespective of initial childhood ability or social class. [ABSTRACT FROM AUTHOR]

Published
2016
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285. Use of second-person pronouns and schizophrenia

Author

Watson, Andrew R., primary, Defteralı, Çaǧla, additional, Bak, Thomas H., additional, Sorace, Antonella, additional, McIntosh, Andrew M., additional, Owens, David G. C., additional, Johnstone, Eve C., additional, and Lawrie, Stephen M., additional

Published
2012
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286. Towards an interdisciplinary lifetime approach to multilingualism: From implicit assumptions to current evidence

Author

Mehmedbegovic, Dina and Bak, Thomas H.

Abstract

Abstract:Many types of human behaviour, from scientific research to political decision-making, are based on implicit assumptions, considered to be so self-evident that they do not need any further justification. Such assumptions are particularly powerful in topics related to language: one of the most universal and fundamental human abilities and a prerequisite for social life, civilisation and culture. They become a driving force in the current debates about multilingualism.We identify three central assumptions underlying key controversies related to language: (a) the "limited resources model" assuming that learning languages has a detrimental effect on learning other subjects, (b) the notion that the "normal" state of human brain, mind and society is either monolingualism, or a strong dominance of a "mother tongue", accompanied by less relevant "additional" languages, (c) the belief that the aim of language learning is a "native-like" proficiency and anything that fails to reach it has only limited value.Combining radically different academic backgrounds (education and cognitive neuroscience) and methodologies (qualitative and quantitative) we examine how these assumptions influence attitudes towards multilingualism. We evaluate the available empirical evidence and explore conceptual common ground, from the design of school curricula to the promotion of healthy ageing. We conclude that our perspectives complement each other, providing a valuable tool to inform language policy.Résumé:Bien des comportements humains, des recherches scientifiques aux prises de décisions politiques, sont basés sur des hypothèses implicites, considérées comme si évidentes en elles-mêmes qu'elles ne nécessitent donc pas de justifications supplémentaires. Ces hypothèses sont particulièrement pertinentes sur les sujets concernant le langage, capacité humaine la plus universelle et la plus fondamentale, et pré-requis pour la vie en société, la civilisation et la culture. Ces hypothèses jouent un rôle moteur dans les débats actuels sur le multilinguisme.On distingue trois hypothèses majeures subordonnées aux controverses clés liées au langage: a) "le modèle à ressources limitées" qui défend l'idée que l'apprentissage des langues se fait au détriment de l'apprentissage d'autres matières, b) la notion selon laquelle l'état "normal" du cerveau humain, de la pensée et de la société est, soit le monolinguisme, soit une forte domination de la langue maternelle, accompagnée de langues additionnelles moins pertinentes, c) la croyance selon laquelle le but de l'apprentissage des langues est d'atteindre le niveau de compétence d'un locuteur natif et que tout échec à y parvenir en limite la valeur.L'association de nos formations académiques (éducation et neurosciences cognitive) et de nos méthodologies (qualitative et quantitative) qui sont radicalement différentes, nous permettent d'examiner comment ces hypothèses influencent les nombreuses théories au sujet du multilinguisme. Nous analysons les résultats empiriques disponibles et explorons les points communs conceptuels depuis l'élaboration des programmes scolaires jusqu'à la sensibilisation au vieillissement sain. Nous en concluons que nos perspectives se complètent les unes les autres et offrent un précieux outil qui contribue au développement de la politique linguistique.

Published
2017

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