EFFECT OF SUSPENSION SYSTEM ON DYNAMICS OF MOTOR-CYCLES

Abstract

In respect of stability prediction of a motorcycle by mathematical modelling, at higher speeds, considering lateral degrees of freedom only, it was found that eventhough the model predicted the motion to be stable, the actual motion was found to be unstable. Research works of Sharp and Koenen and Pacejka suggest that occurrence of high speed• instability of vehicle is because of interaction of vertical modes with lateral modes of vehicle motion. Therefore, it was suggested that for realistic prediction of stability of motorcycle, it is important to include vertical degrees of freedom also in the mathematical model. As a transmitter of force from unsprung mass to sprung mass, the suspension system plays an important tole in vertical dynamics of motorcycle and hence affect the lateral stability of the motorcycle also if the inplane and out of plane motions are coupled. In this dissertation work, the method suggested by Sharp has been used to get the information about the interaction of vertical and lateral modes of vehicle motion for a TVS-SUZUKI Ax-100 motorcycle. Effect of various parameters such as suspension characteristics, rake-angle and castor trail have been studied, to minimise the coupling between vertical and lateral modes of vehicle motion. and 1V also, to improve stability and control characteristics of the motorcycle in lateral motion. Investigations have been carried out for the motorcycle both under free rolling and under braking conditions. The various motorcycle parameters and aerodynamic forces required for the analysis are obtained by actual laboratory measurements on a TVS-SUZUKI motorcycle.