The running-state of a wheel-set is characterised by structural vibrations superposed on its rigid-body motions. In practise, the input of an identification is restricted to accelerations measured at the left and fight axle-box. An analysis of the structural vibrations shows, that only bending modes have a sufficient large influence on the journal's deflections. Therefore, bending modes in combination with rigid-body motions are taken into account. The identification consists of a decomposition into symmetric and antimetric components to separate symmetric and antimetric bending motions from each other. A subsequent time- frequency analysis based on the start-time Fourier transform provides information about the frequencies and envelopes of all symmetric and antimetric motions involved. The contribution points out, that the short-time Fourier transform exhibits a uniform resolution in time and frequency. In terms of a detailed vibration analysis, this property is more suitable than the non-uniform resolution of wavelet transforms. The validation of the identification is carried out by experiments on a full-scale test rig and simulations. The comparison shows discrepancies with respect to frequency content, envelopes and magnitudes. They are caused by the additional structural elasticities of the test rig as well as stochastic effects in the wheel-rail contact. A significant similarity between experiments and simulations consists of self excited oscillations of the first and second symmetric bending in longitudinal direction. Another important conclusion can be de-rived from the modal description of the wheel-set: The switch of the bending gradient's principal component with respect to time from longitudinal to vertical and backwards might excite structural vibrations. A direct identification of the torsional modes is not possible. In ease of a laterally displaced wheel-set the dynamic interaction via the contact patches causes yawing, which forces the wheel-set to twist. Therefore, the wheel-set's torsion al modes can be observed from the yaw motion. This enables an extended identification of the running-state consisting of rigid-body motions, bending and torsional modes. The restriction of structural vibrations to bending and torsional modes is also confirmed by investigations on the limit cycle of railway wheel-sets. Future work will contain a steady improvement of the simulation tool, an extension of simulation and ex-periment to impressed forces as well as yaw motions and a faithful investigation of the structural vibration's exciting mechanism. The aim consists of the development of a simple dynamic model describing bending and torsional modes and its integration into an observer or Kalman filter layout.
Identification of the running-state of railway wheelsets
Identifikation des Laufzustandes von Eisenbahn-Radsätzen
2006
15 Seiten, 13 Bilder, 7 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
Mechanik , Eisenbahnfahrzeug , Radsatz , Identifikation , Beschleunigungsmessung , Frequenzanalyse , Messung mechanischer Größen , dynamisches Verhalten , Wechselwirkung , mathematisches Modell , Fourier-Transformation , DFT (diskrete Fourier-Transformation) , Wavelet-Transformation , experimentelle Untersuchung , Versuchsaufbau , numerische Simulation , nichtlinearer Effekt , Auslenkung , Frequenzbereich , Torsion , Kalman-Filter
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