A mathematical model an automobile is described, which permits the study simultaneous concerning and ride motions on irregular terrain. A major departure from previous analytical treatments of vehicles is abandonment of the concept of a vehicle-fixed "hinge" to approximate the changing virtual axis about which roll takes place. Eleven degrees of freedom and al major non linearities are included in the equations of motion, which are programmed for time-history solutions on a digital computer. Empirical relationship used to generate tire forces over extreme ranges of operating conditions, are presented in detail. To ease the task of interpretation of the extensive output information, a computer graphics display technique has been developed to produce detailed perspective drawings of the vehicle and terrain at selected intervals of time during a simulated manoeuvre. Comparisons are presented of analytically predicted vehicle responses and test results. Future applications of the described mathematical model, in research related to highway safety, are briefly discussed.
Abstract