A Multibody Dynamics Program for Truck Simulation

This paper presents the application of a multibody formulation program to generating equations of motion for commercial vehicles. The formulation procedure adopts the separated-form virtual work principle. Equations are expanded using generalized coordinate partitioning through a Jacobian matrix expansion. The inertia force vector is separated into nonlinear, linear and time-dependent terms, and the generalized force vector is derived from virtual energies. Friction forces are included in the formulation. Nonlinear and linearized models are provided in a symbolic FORTRAN form allowing the control design be implemented with second-order or first-order equations. A fourth-fifth order Runge-Kutta-Fehlberg's algorithm with self-adjustable step sizes is utilized to numerically integrate the reduced systems. An example, a six-axle tractor-semitrailer model is demonstrated.