MODELLING AND ANALYSIS OF A SEMI-ACTIVE SUSPENSION SYSTEM FOR PASSENGER TRAINS

Abstract

Speed and transport capacity of rail vehicles keep on increasing. Passengers demand more comfortable and safer travel through rail vehicles at higher speeds. However, faster speeds of a rail vehicle on irregular track cause larger motion of the car body that can result in an uncomfortable ride. Thus the role of a suspension system is important because a suspension system improves ride comfort and reduces vibration of a rail vehicle on irregular tracks. As the vibration of a train becomes fierce when the train runs at high speed, it is crucial to develop a novel suspension system to negotiate train’s vibration. In this dissertation work, the ride quality of an existing rail vehicle in lateral vibration using modified Bouc-Wen type magnetorheological fluid damper is investigated. The railway vehicle is modelled as a full-scale nine degrees of freedom system considering lateral, yaw and roll motions of car body, front and rear bogies. Tracks with two different types of irregularity are considered for a train speed of 160 km/h and 200 km/h. The track input is given to the multibody system in VI-Rail software and the wheel response is generated. The wheel motions are input to the mathematical model represented in MATLAB/SIMULINK. Four types of analysis are performed (i) with conventional passive lateral damper, (ii) with semi-active low MR lateral damper (0 V), (iii) with semi-active high MR lateral damper (12 V), and (iv) with semi-actively controlled MR lateral damper in secondary suspension. The disturbance rejection and continuous state controller algorithms were applied to control the damper force to reduce the lateral vibration. The responses in terms of displacement and acceleration of the car body center of gravity are compared in terms of vibration reduction index. It is found that there is a significant improvement in the index using a semi-active lateral damper. The results clearly imply that the proposed semi-active suspension system improves the vibration attenuation ability and ride quality of the vehicle.