Time filter

Source Type

Kumar M.,Center for Life Science Automation | Stoll N.,University of Rostock | Stoll R.,University of Rostock
IEEE Transactions on Fuzzy Systems | Year: 2011

The application of nonlinear optimization to the estimation of fuzzy model parameters is well known. To do the reverse of this, the concept of stationary fuzzy Fokker-Planck learning (SFFPL) is introduced, i.e., SFFPL applies the fuzzy modeling technique in nonlinear optimization problems. SFFPL is based on the fuzzy approximation of the stationary cumulative distribution function of a stochastic search process associated with the nonlinear optimization problem. A carefully designed algorithm is suggested for SFFPL to locate the optimum point. This paper also considers the variational Bayes (VB)-based inference of a stochastic fuzzy filter whose consequents, as well as antecedents, are random variables. The problem of VB inference of stochastic antecedents, because of the nonlinearity of the likelihood function, is analytically intractable. The SFFPL algorithm for high-dimensional nonlinear optimization that does not require the derivative of the objective function can be used to numerically solve the stochastic fuzzy filtering problem. © 2011 IEEE.

Kumar M.,Center for Life Science Automation | Stoll N.,University of Rostock | Stoll R.,University of Rostock
IEEE Transactions on Fuzzy Systems | Year: 2010

This study, under the variational Bayes (VB) framework, infers the parameters of a Takagi-Sugeno fuzzy filter having deterministic antecedents and stochastic consequents. The aim of this study is to take advantages of the VB framework to design fuzzy-filtering algorithms, which include an automated regularization, incorporation of statistical noise models, and model-comparison capability. The VB method can be easily applied to the linear-in-parameters models. This paper applies the VB method to the nonlinear fuzzy filters without using Taylor expansion for a linear approximation of some nonlinear function. It is assumed that the nonlinear parameters (i.e., antecedents) of the fuzzy filter are deterministic, while linear parameters are stochastic. The VB algorithm, by maximizing a strict lower bound on the data evidence, makes the approximate posterior of linear parameters as close to the true posterior as possible. The nonlinear deterministic parameters are tuned in a way to further increase the lower bound on data evidence. The VB paradigm can be used to design an algorithm that automatically selects the most-suitable fuzzy filter out of the considered finite set of fuzzy filters. This is done by fitting the observed data as a stochastic combination of the different Takagi-Sugeno fuzzy filters such that the individual filters compete with one another to model the data. © 2006 IEEE.

Kumar M.,Center for Life Science Automation | Neubert S.,University of Rostock | Behrendt S.,University of Rostock | Rieger A.,University of Rostock | And 4 more authors.
IEEE Transactions on Fuzzy Systems | Year: 2012

Quantifying stress levels of an individual based on a mathematical analysis of real-time physiological data measurements is challenging. This study suggests a stochastic fuzzy analysis method to evaluate the short time series of R-R intervals (time intervals between consecutive heart beats) for a quantification of the stress level. The 5-min-long series of R-R intervals recorded under a given stress level are modeled by a stochastic fuzzy system. The stochastic model of heartbeat intervals is individual specific and corresponds to a particular stress level. Once the different heartbeat interval models are available for an individual, an analysis of the given R-R interval series generated under an unknown stress level is performed by a stochastic interpolation of the models. The stress estimation method has been implemented in a mobile telemedical application employing an e-health system for an efficient and cost-effective monitoring of patients while at home or at work. The experiments involve 50 individuals whose stress scores were assessed at different times of the day. The subjective rating scores showed a high correlation with the values predicted by the proposed analysis method. © 1993-2012 IEEE.

Liu H.,University of Rostock | Stoll N.,Center for Life Science Automation | Junginger S.,University of Rostock | Thurow K.,Center for Life Science Automation
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2013

In life science laboratories, mobile robots are adopted to do transportation tasks among distributed automated islands or rooms. To use those mobile robots effectively, a number of technology issues have to be considered, such as path planning of transportation and charging, localization, communication, etc. In this paper an application of charging management for mobile robot transportation is presented. In this application: (a) to localize the mobile robots accurately and fast in life science environments, a method using ceiling landmarks is adopted; (b) to measure the power status from all running robots, a power module for the server and client sides is designed; (c) to let mobile robots go charging automatically, an automated charging station is utilized; and (d) to select the best installing positions for the charging stations, an intelligent method based on the Artificial Immune Algorithm (AIA) is proposed, which considers both of the distances among the expected working positions and their distribution of transportation tasks. A real case shows that the presented application is effective for mobile robot charging management in life science environments. © 2013 IEEE.

Neubert S.,University of Rostock | Arndt D.,Center for Life Science Automation | Thurow K.,Center for Life Science Automation | Stoll R.,University of Rostock
Telemedicine and e-Health | Year: 2010

In this article, the development of a system for online monitoring of a subject's physiological parameters and subjective workload regardless of location has been presented, which allows for studies on occupational health. In the sector of occupational health, modern acquisition systems are needed. Such systems can be used by the subject during usual daily routines without being influenced by the presence of an examiner. Moreover, the system's influence on the subject should be reduced to a minimum to receive reliable data from the examination. The acquisition system is based on a mobile handheld (or smart phone), which allows both management of the communication process and input of several dialog data (e.g., questionnaires). A sensor electronics module permits the acquisition of different physiological parameters and their online transmission to the handheld via Bluetooth. The mobile handheld and the sensor electronics module constitute a wireless personal area network. The handheld allows the first analysis, the synchronization of the data, and the continuous data transfer to a communication server by the integrated mobile radio standards of the handheld. The communication server stores the incoming data of several subjects in an application-dependent database and allows access from all over the world via a Web-based management system. The developed system permits one examiner to monitor the physiological parameters and the subjective workload of several subjects in different locations at the same time. Thereby the subjects can move almost freely in any area covered by the mobile network. The mobile handheld allows the popping-up of the questionnaires at flexible time intervals. This electronic input of the dialog data, in comparison to the manual documentation on papers, is more comfortable to the subject as well as to the examiner for an analysis. A Web-based management application facilitates a continuous remote monitoring of the physiological and the subjective data of the subject. © 2010 Mary Ann Liebert, Inc.

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