Abstract
This report presents the author’s research work as a contribution to his PhD degree. The major objective of the research is to develop and simulate comprehensive and efficient vehicle dynamics models of rigid and articulated vehicles for sensitivity analyses of tyres/wheels and vehicle suspension parameters. These dynamics models include both linear and non-linear formulations and rigid and articulated configurations. Previous research work in the same field has been reviewed and a literature survey of the work carried out by several authors is presented. Especially, the material regarding the effects of tyres/wheels, suspension parameters and vehicle layouts on handling performance is discussed. In the first part of the report simpler but generic versions of linear vehicle models for rigid and articulated vehicle are developed and simulated for the analyses of the effect vehicle layout and number of axles/tyres. A detailed discussion on the structure and behaviour of the linear models inclusive of tyre delay/lag is present. These linear models are used to analyse the performance of different layouts of heavy vehicles, including rigid and articulated configurations. Frequency response (i. e. using Bode diagrams) analyses for the handling characteristics, specifically vehicle yaw rate, vehicle body sideslip angle and towing-angle (in case of articulated vehicles only) have been carried out. The linear models are further extended by introducing the tyre lag/delay dynamics within the vehicle models and effect of first order and second order tyre dynamics on vehicles dynamic response in time and frequency domain is examined. It has been noticed that the tyre lag characteristics significantly alter the vehicle handling behaviour specifically in terms of damping of the vehicle yaw rate response. Further to the advancement of linear vehicle models, more comprehensive non-linear vehicle dynamics models are developed and simulated. Non-linear simulations for vehicle handling behaviours are carried out to investigate the effects of a range of vehicle non-linearities present in tyres, suspension and overall structure of the vehicles. These non-linearities include the profiles lateral force vs. tyre slip angle characteristics, toe angles, static and dynamic camber angles, suspension stiffness, dampers characteristics and vehicle centre of gravity position. Non-linear studies also include rigid and articulated vehicle layouts. Finally conclusions and a future plan for the research activity are presented.