Multibody Modeling and Simulation of a 4WID Differential-Steering Prototype Vehicle

This thesis presents the development of a multibody model of a four-wheel-independent drive (4WID) prototype vehicle that employs differential steering as its sole steering mechanism. Dynamic modeling and control design have been integrated within a single environment, MATLAB/Simulink, using the Simscape Multibody library and its capability to import CAD models. A tire–ground contact model requiring few parameters has been developed for non standard tires, due to their specific dimensions and construction. The model is derived from a revised Dugoff formulation presented in an SAE technical paper and has been extended to account for the self-aligning moment. Additional work has been done to integrate it into a multibody simulation, including the computation of the vertical force, the static–dynamic transition, frame-of-reference consistency, and numerical refinements to improve stability. It has been designed as a versatile plug-and-play tool for other tires in cases where conventional models such as Pacejka’s cannot be applied due to the lack of empirical data. The suspension configuration of the prototype—designed to minimize the differential torque required to steer the wheels and characterized by asymmetry with respect to the vehicle’s longitudinal midplane—motivates the implementation of a yaw-rate control strategy. This controller should distribute motor torques to ensure straight-line motion and could potentially be employed to generate the torque inputs required for basic maneuvers. Overall, this work provides a flexible simulation framework for studying unconventional vehicle architectures and supporting control development when standard automotive templates prove inadequate.