- Vacancy: PHD POSITION “TENSORS FOR SYSTEM IDENTIFICATION” AT ELEC, VRIJE UNIVERSITEIT BRUSSEL (VUB)
‘ELEC’ stands for “Fundamental Electricity and Instrumentation” (in Dutch: “Algemene Elektriciteit en Instrumentatie”) and the name corresponds to the educational and research tasks and objectives of the department. The main research activity of the department is the development of new measurement techniques using advanced signal processing methods, embedded in an identification framework. When we make a measurement, we have to make a number of decisions: firstly a model for the considered part of reality is proposed (e.g. for a resistance measurement Ohm’s law can be selected, describing the relation between the voltage across the resistor and the current through it); next a number of measurements is made (e.g. a number of current and voltage measurements); finally the quantities of interest are extracted from these measurements by matching the model to the data. Often an intuitive approach is used. However, in the presence of measurement errors this can lead to a very poor and even dangerous behaviour: the user wouldn't remark that something is going seriously wrong. This is the major motivation for the development of the identification theory. It offers a systematic approach to ‘optimally’ fit mathematical models to experimental data, eliminating stochastic distortions as much as possible. As such it can be considered as the modern formulation of the measurement problem, and for that reason the identification approach is the “fil rouge” in most of the activities of the department.
Each measurement (or identification session) consists of a series of basic steps:
- Collect information about the system;
- Select a (non) parametric model structure to represent the system;
- Select the model parameters to fit the model as well as possible to the measurements (this requires a “goodness of fit” criterion);
- Validate the selected model.
Most of the research activities of the department are related to one of these problems, but this does not narrow our focus. At this moment we deal with a very wide scope of application fields:
- Systems covering the frequency range from a few MHz up to 50 GHz,
- Linear systems, non-linear systems and time varying systems
- Lumped systems and distributed systems.
We applied the measurement and modelling techniques to the identification of electrical machines (frequency range 0.01 Hz till 1 kHz, linear models, 2 inputs and 2 outputs), mechanical vibrating systems (frequency range below 5 kHz, linear or non-linear, up to 2 inputs/2 outputs), electronic circuits and filters (frequency range up to 5 MHz, linear and non-linear models, single input/single output or multiple input/multiple output), underwater acoustics (frequency range up to a few MHz, 1 input and 2 outputs), distributed systems (telecommunication lines, up to a few hundreds MHz), microwave applications (frequency range up to 50 GHz, non-linear, 6-port measurements). Since a few years we apply those methods also to the analysis of biological samples used as records of global climate change. For some of these applications the efforts are focused on the development of new measurement instruments (measurement of telecommunication lines, non-linear microwave analyser), for others we focused completely on the development of new data processing and modelling techniques, or even worked on the underlying fundamental theoretical aspects.
To cover this wide application range, we make use of an extensive measurement park. Most of it nowadays consists of VXI-or PXI-based data-acquisition systems, although we have also some classical instruments like network and spectrum analysers. All these instruments are computer controlled in a MatlabTM environment.
The Research teams of ELEC are:
There are no formal research groups in the department ELEC. There are 3 research teams that cooperate intensively with each other.
- Team A: Data driven modeling (Rik Pintelon, J. Schoukens)
- Team B: Applied signal processing for engineering, telecommunications and Microwave systems (Gerd Vandersteen, Yves Rolain and Leo Van Biesen)
- Team C: Structured low-rank approximation (Ivan Markovsky)
The Research topics are:
- Automatic Measurement Systems
- Telecommunication: application of information theory in data telecommunication by wire problems (xDSL)
- Telecommunication: environmental G.I.S. development
- Telecommunication: 4G communication
- Telecommunication: navigation techniques
- Telecommunication: positioning Techniques using the cellular network (focus on GSM)
- Telecommunication: proactive Location-based Services (LBS) using multiple positioning technologies
- System identification and parameter estimation of linear, nonlinear and time varying systems
- Experiment design
- Time and frequency domain system identification
- Development and distribution of a system identification toolbox
- Identification of time- and parameter-varying systems
- Applied Signal Processing for Engineering: instrumentation setup contributions
- Applied Signal Processing for Engineering: instrumentation calibration contributions
- Structured Low-rank approximation
- Modelling high frequency nonlinear systems
- Medical Measurements and Signal Analysis
- Linear and nonlinear modelling techniques for medical and high-frequency applications