Laboratory of Modelling and Identification of Dynamic and Mechatronic Systems

Department:   Department D 3 - Dynamics and Vibration
Head:   Ing. Jan Kozánek, CSc.

Laboratory is engaged in the identification and tuning of complicated and mechatronic dynamical systems, the development of mathematical and physical modelling methods, and their optimisation. The mathematical models are considered to be linear with the corresponding spectral and modal characteristics, weak and stronger nonlinearities, and applications in the dynamics of machines with an emphasis on rotational machines with both classic and contactless bearings (e.g. energy storage systems focusing on flywheel technologies using radial and axial superconducting bearings), on vibration stability and especially on the magnetorheological squeeze film damping devices for vibration suppression of rotors. We cooperate with Physical Institute of Czech Academy od Sciences.


Ing. Jan Kozánek, PhD. – head of  laboratory, spectral and modal identification, the evaluation of measured dates, numerical problems, mathematical modelling of discrete dynamic systems

Prof. Jaroslav Zapoměl, DrSc. – applied dynamics, dynamics of rotors, computer modelling and simulations, smart damping elements of rotating systems

Ing. Jan Košina – project work, the problems of electric drives and electro-mechanical systems, laboratory measurements

Jan Cibulka – technical tasks, pickups, measurement in the laboratory and in industrial conditions

Identification and tuning of complicated and mechatronic dynamical systems, the development of mathematical and physical modelling methods

 

The parametric identification in mechanical engineering and approximate identification of dynamical systems were studied. Usually, as the input data of the parametric identification methods in the frequency domain, the corresponding pairs of the “unit harmonic force excitation”—“ steady state harmonic response” are considered. This new proposition deals with approximate identification of linear dynamical systems by time response on unknown initial displacement (or velocity) with the help of the Fourier transform.

Spektrální vlastnosti a identifikace aerodynamických ložisek, stabilitní problémy.

a)

Spektrální vlastnosti a identifikace a aerostatických ložisek, stabilitní problémy.

b)

Fig. 1. The spectral properties and identification of aerodynamic  (a) and aerostatic bearings (b), the stability

 

 

In recent years, the self-excited oscillation properties of the airfoil profile NACA0015 in subsonic flow were investigated, especially modal analysis and flutter characteristics, and the identification of the start of flutter and limits of the aeroelastic stability. Experiments were carried out both in the laboratory and in aerodynamic tunnel of the Institute of Thermomechanics. The identified eigenvalues and eigenmodes for zero flow velocity are compared with measured flutter properties (frequency, modes and time evolutions) of the airfoil.

Proudové pole působící na profil při nástupu flutteru, aerodynamické síly a momenty, vyhodnocení interferogramů.Fig. 2. The flow field acting on the fluttering profile, aerodynamic forces and moments, evaluation of interferograms

 

 

The magnetorheological squeeze film damping devices for vibration suppression of rotors were studied and published in prestigious scientific journals. It's about solutions of a complex interaction between mutually coupled mechanical, hydraulic, magnetic and electric phenomena. The corresponding mathematical models (with composite materials affected by a magnetic field) were proposed and numerically verified for a wide range of the rotor operating speeds. During the solution it was obtained a number of pieces of knowledge about the nonlinear effects, time delays, and complex influences of the electromagnetic phenomena occurring in magnetorheological damping devices used in the vibration attenuation of rotors.

 

Tuhý rotor tlumený magnetoreologickými vrstvami oleje

 

Tuhý rotor tlumený magnetoreologickými vrstvami oleje

 

Tuhý rotor tlumený magnetoreologickými vrstvami oleje

Fig. 3. Rigid rotor damped by magnetorheological squeeze film dampers

 

 

During the cooperation with Prague Musical Academy, Department of Acoustics, Prague, the identification of dynamic properties of tonewood, have been carried out. Dynamic experiments are based on the impulse excitation and the steady state harmonic response is calculated by Fourier transform of time-sampled measured signals (excitation and response). Frequency transfer function fitting identification method determines complex modal and spectral eigen-parameters, mainly eigenfrequencies and eigendampings. The results are prepared for the comparison (at least what concerns the identified eigenfrequencies) with the models created by FEM.

Radiální ohybový tvar obdélníkové dřevěné desky.

a)

 

Radiální kroutící tvar obdélníkové dřevěné desky.

b)

Fig. 4. Radial and twisting mode of a rectangular plate

 

 

Aspects of energy storage systems focusing on flywheel technologies were studied in the project of the Czech Academy of Sciences “Strategy AV21”, programme “Efficient Energy Transformation and Storage”  The evaluation of the vibration stability is the essential part of the design process of vertical flywheel devices.

 

Axiální a radiální uložení na principu supravodivých magnetů.

a)

 

Axiální a radiální uložení na principu supravodivých magnetů.

b)

Fig. 5. Axial and radial contactless suspension using superconducting principle

4channels analyzer VT-80 - Bruel&Kjaer, sensors

Cryogenic system CH-110 and compressor F-704, SUMITOMO Cryogenics Europe

Vacuum pump (PM 015 886AT, CKF00041), Pfeiffer VACUUM, Austria