@article{MTMT:33432672,
	title = {Using scientific machine learning for experimental bifurcation analysis of dynamic systems},
	url = {https://m2.mtmt.hu/api/publication/33432672},
	author = {Beregi, Sándor and Barton, David A. W. and Rezgui, Djamel and Neild, Simon},
	doi = {10.1016/j.ymssp.2022.109649},
	journal-iso = {MECH SYST SIGNAL PR},
	journal = {MECHANICAL SYSTEMS AND SIGNAL PROCESSING},
	volume = {184},
	unique-id = {33432672},
	issn = {0888-3270},
	abstract = {Augmenting mechanistic ordinary differential equation (ODE) models with machine-learnable structures is a novel approach to create highly accurate, low-dimensional models of engineering systems incorporating both expert knowledge and reality through measurement data. Our exploratory study focuses on training universal differential equation (UDE) models for physical nonlinear dynamical systems with limit cycles: an aerofoil undergoing flutter oscillations and an electrodynamic nonlinear oscillator. We consider examples where training data is generated by numerical simulations, whereas we also employ the proposed modelling concept to physical experiments allowing us to investigate problems with a wide range of complexity. To collect the training data, the method of control-based continuation is used as it captures not just the stable but also the unstable limit cycles of the observed system. This feature makes it possible to extract more information about the observed system than the open-loop approach (surveying the steady state response by parameter sweeps without using control) would allow. We use both neural networks and Gaussian processes as universal approximators alongside the mechanistic models to give a critical assessment of the accuracy and robustness of the UDE modelling approach. We also highlight the potential issues one may run into during the training procedure indicating the limits of the current modelling framework.},
	keywords = {NONLINEAR DYNAMICS; machine learning; Bifurcation analysis; Universal differential equations},
	year = {2023},
	eissn = {1096-1216},
	orcid-numbers = {Beregi, Sándor/0000-0002-3167-9250}
}

@article{MTMT:32572363,
	title = {Stability and local bifurcation analyses of two-wheeled trailers considering the nonlinear coupling between lateral and vertical motions},
	url = {https://m2.mtmt.hu/api/publication/32572363},
	author = {Horváth, Hanna Zsófia and Takács, Dénes},
	doi = {10.1007/s11071-021-07120-9},
	journal-iso = {NONLINEAR DYNAM},
	journal = {NONLINEAR DYNAMICS},
	volume = {107},
	unique-id = {32572363},
	issn = {0924-090X},
	abstract = {The nonlinear dynamics of two-wheeled trailers is investigated using a spatial 4-DoF mechanical model. The non-smooth characteristics of the tire forces caused by the detachment of the tires from the ground and other geometrical nonlinearities are taken into account. Beyond the linear stability analysis, the nonlinear vibrations are analyzed with special attention to the nonlinear coupling between the vertical and lateral motions of the trailer. The center manifold reduction is performed leading to a normal form up to third degree terms. The nature of the emerging periodic solutions, and, thus, the sense of the Hopf bifurcations are verified semi-analytically and numerically. Simplified models of the trailer are also used in order to point out the practical relevance of the study. It is shown that the linearly independent pitch motion affects the sense of the Hopf bifurcations at the linear stability boundary. Namely, the constructed spatial trailer model provides subcritical bifurcations for higher center of gravity positions, while the commonly used simplified mechanical models explore the less dangerous supercritical bifurcations only. Domains of loss of contact of tires are also detected and shown in the stability charts highlighting the presence of unsafe zones. Experiments are carried out on a small-scale trailer to validate the theoretical results. A good agreement can be observed between the measured and numerically determined critical speeds and vibration amplitudes.},
	year = {2022},
	eissn = {1573-269X},
	pages = {2115-2132},
	orcid-numbers = {Horváth, Hanna Zsófia/0000-0002-9427-3565; Takács, Dénes/0000-0003-1226-8613}
}

@article{MTMT:30840377,
	title = {Bifurcation analysis of wheel shimmy with non-smooth effects and time delay in the tyre–ground contact},
	url = {https://m2.mtmt.hu/api/publication/30840377},
	author = {Beregi, Sándor and Takács, Dénes and Stépán, Gábor},
	doi = {10.1007/s11071-019-05123-1},
	journal-iso = {NONLINEAR DYNAM},
	journal = {NONLINEAR DYNAMICS},
	volume = {98},
	unique-id = {30840377},
	issn = {0924-090X},
	year = {2019},
	eissn = {1573-269X},
	pages = {841-858},
	orcid-numbers = {Beregi, Sándor/0000-0002-3167-9250; Takács, Dénes/0000-0003-1226-8613; Stépán, Gábor/0000-0003-0309-2409}
}

@article{MTMT:30893747,
	title = {Theoretical and experimental study on the nonlinear dynamics of wheel-shimmy},
	url = {https://m2.mtmt.hu/api/publication/30893747},
	author = {Beregi, Sándor and Takács, Dénes and Gyebrószki, Gergely and Stépán, Gábor},
	doi = {10.1007/s11071-019-05225-w},
	journal-iso = {NONLINEAR DYNAM},
	journal = {NONLINEAR DYNAMICS},
	volume = {4},
	unique-id = {30893747},
	issn = {0924-090X},
	year = {2019},
	eissn = {1573-269X},
	pages = {2581-2593},
	orcid-numbers = {Beregi, Sándor/0000-0002-3167-9250; Takács, Dénes/0000-0003-1226-8613; Gyebrószki, Gergely/0000-0002-0263-7510; Stépán, Gábor/0000-0003-0309-2409}
}

@article{MTMT:2991438,
	title = {Tyre induced vibrations of the car-trailer system},
	url = {https://m2.mtmt.hu/api/publication/2991438},
	author = {Beregi, Sándor and Takács, Dénes and Stépán, Gábor},
	doi = {10.1016/j.jsv.2015.09.015},
	journal-iso = {J SOUND VIB},
	journal = {JOURNAL OF SOUND AND VIBRATION},
	volume = {362},
	unique-id = {2991438},
	issn = {0022-460X},
	year = {2016},
	eissn = {1095-8568},
	pages = {214-227},
	orcid-numbers = {Beregi, Sándor/0000-0002-3167-9250; Takács, Dénes/0000-0003-1226-8613; Stépán, Gábor/0000-0003-0309-2409}
}

@article{MTMT:2187047,
	title = {Micro-shimmy of towed structures in experimentally uncharted unstable parameter domain},
	url = {https://m2.mtmt.hu/api/publication/2187047},
	author = {Takács, Dénes and Stépán, Gábor},
	doi = {10.1080/00423114.2012.691522},
	journal-iso = {VEHICLE SYST DYN},
	journal = {VEHICLE SYSTEM DYNAMICS},
	volume = {50},
	unique-id = {2187047},
	issn = {0042-3114},
	abstract = {In this paper, the lateral instability of towed structures (trailers, caravans and articulated buses) is investigated with special attention to the small amplitude lateral vibration that leads to a higher energy consumption in certain parameter domains. A low degree-of-freedom mechanical model of a shimmying towed tyre is used that describes the dynamics of the tyre-ground contact patch by the time delayed differential equation. Stability charts are calculated and the theoretically predicted linear unstable islands of small amplitude shimmy motions are validated by laboratory experiments. A tyre is towed by a relatively long caster, and its temperature and the input current of the conveyor belt are measured in order to show the increased value of the rolling resistance.},
	keywords = {SYSTEMS; DYNAMICS; simulation; Friction; MOTION; shimmy; Thermal effects; tyre models; car; rolling-sliding; tyre-road interaction},
	year = {2012},
	eissn = {1744-5159},
	pages = {1613-1630},
	orcid-numbers = {Takács, Dénes/0000-0003-1226-8613; Stépán, Gábor/0000-0003-0309-2409}
}

@article{MTMT:1234370,
	title = {Delay effects in shimmy dynamics of wheels with stretched string-like tyres},
	url = {https://m2.mtmt.hu/api/publication/1234370},
	author = {Takács, Dénes and Orosz, Gábor and Stépán, Gábor},
	doi = {10.1016/j.euromechsol.2008.11.007},
	journal-iso = {EUR J MECH A-SOLID},
	journal = {EUROPEAN JOURNAL OF MECHANICS A-SOLIDS},
	volume = {28},
	unique-id = {1234370},
	issn = {0997-7538},
	year = {2009},
	eissn = {1873-7285},
	pages = {516-525},
	orcid-numbers = {Takács, Dénes/0000-0003-1226-8613; Stépán, Gábor/0000-0003-0309-2409}
}

@article{MTMT:106066,
	title = {Chaotic motion of wheels},
	url = {https://m2.mtmt.hu/api/publication/106066},
	author = {Stépán, Gábor},
	doi = {10.1080/00423119108968994},
	journal-iso = {VEHICLE SYST DYN},
	journal = {VEHICLE SYSTEM DYNAMICS},
	volume = {20},
	unique-id = {106066},
	issn = {0042-3114},
	abstract = {Trolleys have wheels which can choose the direction of their rolling. Studying the motion of a wheel like this, we can often find periodic motions ('shimmy') or even chaotic ones. It has also been experienced that the chaotic motions sometimes disappear quite unexpectedly. A strongly simplified model of these systems is analysed in the paper by means of the methods of bifurcation theory. Analytical and numerical results are shown to characterize the system, including simulation results. Similar behaviour can be found in more complicated systems as well, like the trailers or the nosegears of aeroplanes. The development of the so-called transient chaotic motion is explained in these systems.},
	year = {1991},
	eissn = {1744-5159},
	pages = {341-351},
	orcid-numbers = {Stépán, Gábor/0000-0003-0309-2409}
}