Raquel Dormido

Development of a Web-Based Control Laboratory for Automation Technicians: The Three-Tank System

This paper introduces a Web-based control laboratory for experimentation on a nonlinear multiple-input-multiple-output (MIMO) system: the three-tank plant. Using this application, automation technician students can learn in a practical way many fundamental aspects of control processes. The client-side of the virtual laboratory has been developed using the programming support provided by Easy Java Simulations (EJS), an open-source tool for teachers with limited programming skills who want to create Java applications and applets. The lab has been integrated in the collaborative Web-based experimentation environment eMersion which provides more flexibility for the students performing the laboratory experiments.

A Systematic Two-Layer Approach to Develop Web-based Experimentation Environments for Control Engineering Education

This paper introduces the systematic approach currently used by the Department of Computer Science and Automatic Control of the Spanish University of Distance Learning (UNED) to develop Web-based laboratories for distance learning of topics with high technical contents such as control engineering. This approach differentiates two layers in the construction of web- based laboratories: the experimentation layer and the e-learning layer. For the experimentation layer, LabVIEW and data acquisition boards from National Instruments are used to create the server-side applications and Easy Java Simulations for the client-side interfaces. For the e-learning layer, the eMersion environment is used to support the required flexible educational scheme. This paper describes the programming techniques implemented and the design considerations that justify these particular choices. As an llustrative case-study, an example of development of a web-based application is discussed, in which an electrical drive servo-motor is introduced as a convenient setup to practice with motion control applications. Other significant examples of web-based experiments developed by the authors are also reported.

An Integrated Virtual and Remote Control Lab: The Three-Tank System as a Case Study

Internet-based technologies can supplement traditional laboratories with remote or simulated experimentation sessions. The authors describe their virtual and remote laboratory, which uses a nonlinear system that students can run from anywhere on the Internet. The implementation integrates both open source and commercial software tools.

Search and retrieval of plasma wave forms: Structural pattern recognition approach

Databases for fusion experiments are designed to store several million wave forms. Temporal evolution signals show the same patterns under the same plasma conditions and, therefore, pattern recognition techniques can allow identification of similar plasma behaviors. Further developments in this area must be focused on four aspects: large databases, feature extraction, similarity function, and search/retrieval efficiency. This article describes an approach for pattern searching within wave forms. The technique is performed in three stages. Firstly, the signals are filtered. Secondly, signals are encoded according to a discrete set of values (code alphabet). Finally, pattern recognition is carried out via string comparisons. The definition of code alphabets enables the description of wave forms as strings, instead of representing the signals in terms of multidimensional data vectors. An alphabet of just five letters can be enough to describe any signal. In this way, signals can be stored as a sequence of ch...

Developing and Implementing Virtual and Remote Labs for Control Education: The UNED pilot experience

Last years, research efforts on the development of virtual and remote laboratories in control engineering education have been reported in many conferences, workshops and journals. However, it is observed that pilot experiences about the utilization of web-based laboratories are not habitual practices. In this paper it is described the pilot experience of the Department of Computer Science and Automatic Control of the Spanish University of Distance Learning (UNED) about the introduction of three web- based laboratories in a course on process control. This experience begins with descriptions of the tools employed to develop client and server-sides and the collaborative environment used to publish the labs in Internet. Attention is due to the concept of task protocol. It consists essentially of an ordered list of activities that students must execute in the virtual and remote mode of each one of the three web-based laboratories. To conclude, results of the pilot experience are given by means of evaluation questionnaires.

Event-Based Control Strategy for Mobile Robots in Wireless Environments.

In this paper, a new event-based control strategy for mobile robots is presented. It has been designed to work in wireless environments where a centralized controller has to interchange information with the robots over an RF (radio frequency) interface. The event-based architectures have been developed for differential wheeled robots, although they can be applied to other kinds of robots in a simple way. The solution has been checked over classical navigation algorithms, like wall following and obstacle avoidance, using scenarios with a unique or multiple robots. A comparison between the proposed architectures and the classical discrete-time strategy is also carried out. The experimental results shows that the proposed solution has a higher efficiency in communication resource usage than the classical discrete-time strategy with the same accuracy.

Distributed control for large-scale systems with adaptive event-triggering

Abstract The asymptotic stability of distributed-event triggered control for large-scale interconnected systems can be achieved with time-dependent trigger functions. The choice of some of the parameters in the trigger functions relies on some properties of the overall system, which are not known a priori by the individual nodes. This paper presents an iterative method for the distributed estimation of such parameters, which allows the event-triggered control algorithm to evolve to a less conservative design. We provide proofs of convergence while the asymptotic stability and the existence of a lower bound for the inter-event times are preserved. The complexity of the proposed approach is analyzed, and the results are illustrated through simulations.

Image classifier for the TJ-II thomson scattering diagnostic: evaluation with a feed forward neural network

There are two big stages to implement in a signal classification process: features extraction and signal classification. The present work shows up the development of an automated classifier based on the use of the Wavelet Transform to extract signal characteristics, and Neural Networks (Feed Forward type) to obtain decision rules. The classifier has been applied to the nuclear fusion environment (TJ-II stellarator), specifically to the Thomson Scattering diagnostic, which is devoted to measure density and temperature radial profiles. The aim of this work is to achieve an automated profile reconstruction from raw data without human intervention. Raw data processing depends on the image pattern obtained in the measurement and, therefore, an image classifier is required. The method reduces the 221.760 original features to only 900, being the success mean rate over 90%. This classifier has been programmed in MATLAB.

Determination of the optimal number of clusters using a spectral clustering optimization

In this paper, we present a new method, called Spectral Global Silhouette method (GS), to calculate the optimal number of clusters in a dataset using a Spectral Clustering algorithm. It combines both a Silhouette Validity Index and the concept of Local Scaling. First, the GS algorithm has first been tested using synthetic data. Then, it is applied on real data for image segmentation task. In addition, three new methods for image segmentation and two new ways to calculate the optimal number of groups in an image are proposed. Our experiments have shown a promising performance of the proposed algorithms. A new approach to find the optimal number of clusters is presented.This approach is used for the Spectral Clustering algorithm.The method is tested using synthetic data and images.Two ways to calculate the optimal number of groups in an image are presented.Three methods for image segmentation are proposed.

Recent results on structural pattern recognition for Fusion massive databases

Physics studies in fusion devices require statistical analyses of a large number of discharges. Given the complexity of the plasma and the non-linear interactions between the relevant parameters, connecting a physical phenomenon with the signal patterns that it generates can be quite demanding Up to now, data retrieval has been typically accomplished by means of signal name and shot number. The search of the temporal segment to analyze has been carried out in a manual way. Manual searches in databases must be replaced by intelligent techniques to look for data in an automated way. Structural pattern recognition techniques have proven to be very efficient methods to index and retrieve data in JET and TJ-II databases. Waveforms and images can be accessed through several structural pattern recognition applications.