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New multipoint algorithm for eliminating chaotic vibrations in complex non-linear systems

Basiński Radosław, Siwek Krzysztof

Przegląd Elektrotechniczny

2021

R. 97, nr 6

91--96

The paper presents a very effective algorithm for stabilizing unstable periodic orbits, consisting of slight changes in selected parameters of a chaotic system at any time of sampling. Modification of the parameters leads to minimization of the distance of the phase trajectory from the fixed point on the cross-section of the generalized Poincaré map. By modifying several parameters, it is possible to effectively eliminate chaotic vibrations in complex non-linear dynamical systems in the presence of strong disturbances and noise.

W pracy przedstawiono efektywny algorytm stabilizacji niestabilnych orbit okresowych, polegający na niewielkich zmianach wybranych parametrów układu chaotycznego w każdej chwili próbkowania. Modyfikacja parametrów prowadzi do minimalizacji odległość trajektorii fazowej od punktu stałego na przekroju uogólnionego odwzorowania Poincarégo. Realizacja zagadnienia sterowania poprzez zmianę kilku parametrów umożliwia efektywną eliminację drgań chaotycznych w złożonych nieliniowych układach dynamicznych w obecności silnych zakłóceń i szumów.

Nonlinear dynamic dnalysis of high speed rolling element bearings due to cage run-out

Harsha S. P., Kankar P. K., Purohit R. K.

Computer Assisted Mechanics and Engineering Sciences

2005

Vol. 12, No. 1

31-48

The paper presents an analytical model to investigate the nonlinear dynamic behavior of rotor bearing system due to cage run-out. Due to run-out of the cage, the rolling elements no longer stay equally spaced. The mathematical model takes into account the sources of nonlinearity such as Hertzian contact force and cage run-out, resulting transition from no contact-to-contact state between rolling elements and races. The contact between the rolling elements and races is treated as nonlinear springs. The nonlinear stiffness is obtained by application of Hertzian contact deformation theory. The implicit type numerical integration technique Newmark-j3 with Newton Raphson method is used to solve the nonlinear differential equations iteratively. The results are presented in the form of Fast Fourier Transformations (FFT) and contact force-time responses. It is implied from the obtained FFT that due to the cage run-out, the ball passage frequency is modulated with the cage frequency.

Nonlinear dynamic behaviors of high speed rotor supported by rolling element bearings

Harsha S. P., Prakash R., Sandeep K.

International Journal of Applied Mechanics and Engineering

2003

Vol. 8, no 4

705-720

The paper presents a model for investigating structural vibrations in rolling element bearings. The mathematical formulation accounted for tangential motions of rolling elements as well as inner and outer races with the sources of nonlinearity such as the Hertzian contact force, surface waviness and internal radial clearance transition resulting from no contact to contact state between rolling elements and the races. The contacts between the rollers and races are treated as nonlinear springs and the springs act only in compression to simulate the contact deformation and resulting force. The nonlinear stiffness is obtained by using the equations for the Hertzian elastic contact deformation theory. As the nonlinear bearing forces act on the system, a new reduction method and corresponding integration technique is proposed to increase the numerical stability and decrease computer time for system analysis. The effects of various defects of a rotor bearing system in which the rolling element bearings show the periodic, quasi-periodic and chaotic behavior are analyzed. Poincare maps and Fourier spectra are used to elucidate and to illustrate the diversity of the system behavior. It is shown that due to defects such as surface waviness and internal radial clearance the system exhibits an undesirable jump phenomenon with quasi-periodic, subharmonic and chaotic motions.