A Comparison of Active and Passive Railroad Truck Performance

Abstract

truck model stable stable ' stable at low speed unstable at high speed stable at low speed unstable at high speed region(1)The overall scope of this work is to explore and establish dynamic performance capabilities of conventional and innovative rail passenger vehicles in order that guidelines provided in part as an outcome of this effort realistically indicate not only current performance characteristics but also both future dynamic performance capabilities and limitations. Many fundamental characteristics of overall service and safety are determined by the railcar-track interactions transmitted through the passenger truck which provides the primary means of support and guidance for the car, and determines the vibration level transmitted to the carbody from the track and the force level to the track. At the present time, it is not known whether conventional North American passenger trucks or optimized conventional trucks are capable of meeting projected performance requirements or whether only through actively controlled trucks significant improvements in dynamic performance can be achieved. As a partial answer to this question the performance of conventional trucks, optimized conventional trucks, and actively controlled trucks are compared in terms of the combined suspensionltrack wheel-axle model stable unstable at low speed stable at high speed stable at low speed , unstable at high speed (4) unstable Downloaded by [University of Arizona] at 17:14 05 February 2015 110 KIM MORTLAND and J. KARL HEDRICKmaintenance cost to provide a fixed level of ride quality. The suspension elements are optimized by numerical optimization methods subject to practical constraints on both primary and secondary suspension stroke lengths, maximum wheelset excursion, ride quality, curving performance, maximum critical speed, and the level of wheellrail forces. Preliminary results have indicated that active suspensions can provide improved performance at a reduced total cost. Estimates of the suspensionltrack maintenance costs were made from data collected from the North American rail industry and at best indicate only trends. More specifically, the first objective of this paper is to develop a generic lateral model of the passenger trucks' primary and secondary suspension. The linear model will be reduced to a minimum number of independent stiffness and damping parameters. The second objective is to use this model to compare the performance characteristics of the conventional truck as a baseline model with the performance trends of the other trucks so that possible areas of improvement and limits of performance of new trucks over current truck designs may be indicated. IntroductionThe approach taken by this paper and shown in Fig. 1 is to maximize a combination of both stochastic and deterministic track inputs to the vehicle model while still requiring the dynamic performance characteristic of the vehicle to satisfy a set of given constraints. By maximizing the track input in terms of input amplitude the track maintenance tolerances...