Self-excited oscillation in locomotive transmission systems under loss of adhesion

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Self-excited oscillation in locomotive transmission systems under loss of adhesion

Harwood, N.A. / Keogh, P.S.

A study is made of the problem of self-excited torsional oscillations in locomotive transmission systems caused by loss of adhesion between wheels and rails. The control of such oscillations is important because any sustained high levels may constitute a fatigue problem for the components in the transmission drive line. The model used to simulate loss of adhesion incorporates the main components in a drive line. Solutions from this model are also compared with levels of oscillation predicted by a simplified approach and by those obtained by measurements on a trial locomotive. The results of the analysis show that the onset of any oscillations and their levels are critically dependent upon the wheel/rail adhesion characteristic, the drive torque/speed characteristic, and the level of damping in the drive line. Furthermore, should any oscillations occur then the peak to peak levels are approximately proportional to the mean slip-speed of the wheelset. It is established that the oscillations may be controlled either passively by having sufficient drive line damping, or actively by controlling the wheelset mean slip-speed. The latter may be achieved by designing a drive torque/speed characteristic which decreases at a sufficient rate from any steady setting.