Massless links with external forces and bushing effect for multibody dynamic analysis

When the contribution of lightweight components to the total energy of a system is small, the inertia effects are sometimes ignored by replacing them to massless links. For example, a revolute-spherical massless link generates two kinematic constraint equations between adjacent bodies and allows four relative degrees of freedom. In this paper, to implement a massless link systematically in a computer program using the velocity transformation technique, the velocity transformation matrix of massless links is derived and numerically implemented. The velocity transformation matrix for a revolute-spherical massless link and a revolute-universal massless link are appeared as a 6X4 matrix and a 6X3 matrix, respectively. A massless link model in a suspension composite joint transmitting external forces is also developed and the numerical efficiency of the proposed model is compared to a conventional multibody model. For a massless link transmitting external forces, forces acting on links are resolved and transmitted to the attached points with a quasi-static assumption. Numerical examples are presented to verify the formulation.