Globally independent coordinates for real-time vehicle simulation

Models of the dynamics of multibody systems generally result in a set of di fferential-algebraic equations (DAE). State-space methods for solving the D AE of motion ave based on reduction of the DAE to ordinary differential equ ations (ODE), by means of local parameterizations of the constraint manifol d that must be often modified during a simulation. In this paper it is show n that, for vehicle multibody systems, generalized coordinates that are dua l to suspension and/or control forces in the model are independent for the entire range of motion of the system. Therefore, these additional coordinat es, together with Cartesian coordinates describing the position and orienta tion of the chassis, form a set of globally independent coordinates. In add ition to the immediate advantage of avoiding the computationally expensive redefinition of local parameterization in a state-space formulation, the ex istence of globally independent coordinates leads to efficient algorithms f or recovery of dependent generalized coordinates. A topology based approach to identify efficient computational sequences is presented. Numerical exam ples with realistic vehicle handling models demonstrate the improved perfor mance of the proposed approach, relative to the conventional Cartesian coor dinate formulation, yielding real-lime for vehicle simulation.