Mathematical modelling of the lateral motions of an automobile, including a method of driver assessment

The work presented in this Thesis is divided into two parts. Part I is concerned with the inclusion of the lateral flexibilities of a suspension system into a mathematical model. The results from this model show that the flexibility effects can be as powerful in modifying the vehicle response as the suspension/ steering geometry. The basic model is then developed to include the tyre force and steering dynamics. The effects of increasing the complexity of the model are investigated, in addition to a further study of the effects of suspension flexibilities. The dynamics of the vehicles are studied by computing the eigenvalues and eigenvectors of the system, and also by determining the frequency response characteristics. The results from these investigations verify that the effects of suspension flexibilities are of sufficient importance to be included into a mathematical model of the lateral motions of an automobile. In the second part, one of the mathematical models developed in Part I is used in an investigation into the theoretical aspects of the assessment of vehicle handling. The first method of assessment proposed is based on the frequency response characteristics of the vehicle. The method involves the use of a single criterion to assess the handling characteristics, and it is shown that this simplified approach is not adequate. The second method is based on a procedure proposed for the assessment of aircraft handling characteristics. This method involves the use of a model for the driver, and evaluating the relative stability of the driver/vehicle system. Knowledge of the damping associated with the system is also required. In this way, a region can be defined within which a vehicle with desirable handling characteristics can be formulated.