Abstract

In the Montreal metro system, the metro cars operate on pneumatic tires as opposed to the steel wheels and rail tracks used in most subway systems. This type of traction system provides relatively quieter and smoother operation. Despite the use of pneumatic tires and a very smooth concrete track, the Montreal metro cars exhibit complex vibration environment, that arises from dynamic tire-track interactions, and coupled dynamics of vehicle components, namely, axle, bogie and the car body. In this investigation, a 23 degrees-of-freedom, three dimensional ride dynamic mathematical model of the Montreal metro car is developed to study the ride performance under deterministic as well as measured track excitations. The model integrates excitations due to left- and right track surface roughness, and wheel non-uniformity. The wheel non-uniformity is modeled as a combination of an equivalent mass unbalance and out-of-roundness of the tread geometry. The validity of the model is demonstrated by comparing the response characteristics with available measured data. The ride quality of the vehicle at operator's level is assessed in relation to the proposed guidelines upon applying the recommended frequency-weighting filters. The ride responses revealed comprehensive vertical vibration in the vicinity of 6 Hz to which the human body is known to be more sensitive. High magnitude of vertical s vibration near 6 Hz became evident at near the nominal operating speed of 60 km/h, and was associated with wheel non-uniformity and vertical mode resonance of the bogie. The influence of variations in design and operating variables on the ride performance of the metro car is investigated through a comprehensive parametric study. The variations in operating conditions include the forward speed of the metro car and passenger load. The parametric study on design variables includes the variations in the inertial properties of the vehicle components, namely, car body, bogie and axle and variations in suspension properties. The results of the study are discussed to highlight the contributions of these parameters on the ride quality, and to identify most desirable design and operating conditions. Finally, a set of optimal parameters is identified and then comparison is made between nominal and optimal set of design parameters.