Dynamic model and control of vehicles

Abstract

In this thesis the author develops a 14 degrees-of-freedom (DOF) full-car model. The model draws from and improves upon features and setups of certain existing vehicle dynamics models. The proposed model provides a means to simulate vehicle ride and handling behaviors. An accurate prediction of such behaviors will lead to the proper control and design of vehicles. The vehicle’s kinematics and dynamics are developed to reflect the interactions between the rigid mass elements of the model such as the vehicle body and the wheels. The mathematical model includes the nonlinear characteristics of the tires, the three dimensional motions of the sprung and unsprung masses, the inertial coupling between the sprung and unsprung masses, and the restraints and forces imposed by the suspension components. The frictional forces developed at the road-tire contacts are modeled by the single point contact version of the Lund-Grenoble (LuGre) dynamic friction model. An extension of the LuGre friction model is presented to take into account the coupling between the rotational and translational motions of the wheels. Three different numerical study cases are selected to verify the model’s capability in representing various vehicle dynamic situations with respect to the model’s accuracy and to the model’s range of applicability. The issue of active suspension is subsequently discussed. A non-switching sliding mode controller is incorporated into the proposed vehicle model and a substantial reduction in the spectral intensity of a vibration mode of the vehicle body is achieved. Simulation results suggest that the rigorous modeling and mathematical development yields a model that captures satisfactory ride comfort and vehicle performance.