FreeDyn - A Software for Advanced Multibody Simulation: Applications in the Field of Vehicle Dynamics

In the last few years, the complexity of models in multibody dynamics (MBD) has grown tremendously. In particular, industrial simulations of large systems including several flexible bodies, such as complete vehicles result in models with a vast number of degrees of freedom. In most cases, multibody systems are described by a system of differential algebraic equations (DAE). Due to the algebraic constraints C(q,u,t) = 0, the equations of motion are extended by constraint forces of the form CTq λ, where Cq represents the constraint Jacobian and the vector λ includes the Lagrange multipliers. Moreover, u is a vector of parameters or of time-dependent control signals actuating the system. Virtual prototypes, as the multibody model of a mechanical system may be interpreted, should allow the industrial users to figure out all details and hidden potentials of the system under consideration. However, commercial software packages hardly support such investigations and therefore are not always applicable. Due to the demand for customized methods, e.g., for sensitivity analysis, the development of an Independent research code for MBD (FreeDyn) was started at the University of Applied Sciences Upper Austria. Hence, the developers have the opportunity to directly operate on the program code implementing the multibody model as well as mathematical solution strategies. This contribution especially addresses the application of FreeDyn in vehicle dynamics.