## Overview Research Topics

The long term objective of the department is the realization of the IMMI project (Interpretation by Measuring, Modelling and Identification), since 1989. Beside this main project, which covers a broad spectrum of several related activities, also some other independent research topics are at stake.

### Experimental investigation of energy absorption behaviour of circular carbon/epoxy composite tubes under quasi-static and dynamic crush loading

Carbon/epoxy composites demonstrate signiﬁcant and promising improvements of the weight-to-performance ratio in the automotive industry. In this paper, their energy absorption performance is thoroughly investigated. Quasi-static and dynamic axial crush tests have been performed on a variety of...

### Unfalsified LTI models with bounded complexity in the behavioral framework

The notion of the most powerful unfalsified model (MPUM), introduced by Jan C. Willems in the late 1980s, led to a growing interest in exact model identification by researchers from the systems and control community. Willems defined the MPUM for a noise-free infinite time series as the least...

### Data-driven linear quadratic tracking control

Data-driven control is an alternative to the classical model-based control paradigm that does not identify a model of the plant. In this paper, we show that linear quadratic tracking control is equivalent to errors-in-variables Kalman filtering. Alternatively, data-driven tracking control is...

### Multi-channel sum-of-exponentials common dynamics estimation

Estimation of common dynamics among several observed signals occurs in signal processing, system theory, and computer algebra problems. In this paper, we propose subspace methods for common linear time-invariant dynamics detection and estimation. First, we consider the deterministic problem of...

### A Lowner tensorization technique for MIMO transfer function decoupling

We address the problem of finding a diagonal representation of a multi-input-multi-output (MIMO) system in the frequency domain, in other words, decomposing a MIMO system into a set of single-input-single-ouput (SISO) systems...

### Nonparametric Identification of Linear Time-Varying Systems using Gaussian processes

Linear time-varying (LTV) systems are a class of systems with dynamics evolving in time. For these systems we can define a time-varying transfer function. Accordingly, for each frequency a time-varying gain can be attributed to the system as opposed to a fixed gain in the case of time-invariant...

### Linear Time-Varying System Identification in the Presence of Nonlinear Distortions

In this research we consider time-varying systems that are nonlinear to some extent. The output spectrum of such a system, when excited by a multisine, consists of skirts around the excited frequencies, but also could have nonlinear contributions at multiples of the multisine’s fundamental...

### Identification of nonlinear continuous-time systems from noisy input/output observations

The identification and control of LTI systems (linear time-invariant systems) is well established among engineers. So, there is no surprise if one tries to model a nonlinear system with a bunch of LTI systems. There are various ways to do so but maybe LPV (linear parameter varying) modeling...

### Estimation of respiratory impedance at low frequencies using the forced oscillation technique

The forced oscillation technique (FOT) is a non-invasive measurement technique to characterize the impedance of a respiratory system (Zrs). Zrs is defined as a frequency dependent ratio of pressure at the airway opening (pao) to air flow (qe) induced by Zrs.

### Realization and identification of autonomous Wiener systems via low-rank approximation

Wiener systems are nonlinear dynamical systems, consisting of a linear dynamical system and a static nonlinear system in a series connection. Existing results for analysis and identification of Wiener systems assume zero initial conditions. In this paper, we consider the response of a Wiener...

### Applications of polynomial common factor computation in signal processing and systems theory

We consider the problem of computing the greatest common divisor of a set of univariate polynomials and present applications of this problem in system theory and signal processing. One application is blind system identification: given the responses of a system to unknown inputs, find the system...

### Identifying Reflections in High Frequency Structures

The goal of this work is to improve the modeling of Lumped Distributed Structures (LDSs) by obtaining a sensible aaccuracy with a reasonably low number of model parameters while identifying the reflections present.

### Developing wave-based calibration for vector network analyzers

### Current state-of-the-art in RF calibration

Calibration is an essential part of any RF, microwave and millimeter wave measurement process. The accuracy of a bare-bones high-frequency measurement instrument is jeopardized by the influences of non-idealities, cabling and instrument drift....

### Data-driven signal processing using the nuclear norm heuristic

Applications in signal processing and control theory are typically model-based and proceed in two steps. In the 'modeling' step, a mathematical model is built from the measured noisy data. In the 'design' step, the model is used to solve a specific application problem. In this project, we will...

### Carrier aggregation intermodulation distortions in Advanced Systems

Achieving greater throughput requires increasing bandwidth. However, due to frequency’s scarcity, the necessary bandwidth may not be available in one contiguous band. LTE Advanced use multiple bands for one user: that is carrier aggregation [1]. However power amplifier’s efficiency is only...