Comprehensive analysis of gross vehicle dynamics, stability and control under different road and operating conditions

The study reported in this thesis deals with developing a comprehensive model for evaluating the tire forces and dynamic equilibrium condition of a vehicle under general operating conditions. A computer-based scheme is also developed for the automatic control of the braking forces and the steering angles to insure the best dynamic performance, handling characteristics and stability of the vehicle under adverse conditions.; The pneumatic tire of the vehicle in this study is first considered as a deformable element and is modeled by springs. The vehicle body is then treated as a rigid body supported by springs at the position of each wheel. The Linear Programming algorithm is employed to evaluate the dynamic behavior of a vehicle under different road and operating conditions. The vertical load on each tire is also evaluated for the different conditions.; With the objective of achieving vehicle directional stability, controllability and commanded acceleration/braking performance from driver, an optimum distribution of tractive/braking forces will be found. Based on this distribution of tractive/braking forces and applying a nonlinear tire model, a four wheel steering control algorithm with the objective of achieving zero-sideslip-angle of vehicle body is developed. This four wheel steering system makes the vehicle more robust and provides much better handling characteristics. The computer simulation shows that the proposed approach is feasible and can considerably enhance the safety of motion especially under slippery road conditions.