Contact Force Modeling Between Non Convex Objects Using a Nonlinear Damping Model

Abstract

At Sandia National Laboratories, the authors are developing the ability to accurately predict motions for arbitrary numbers of bodies of arbitrary shapes experiencing multiple applied forces and intermittent contacts. In particular, they are concerned with the simulation of systems such as part feeders or mobile robots operating in realistic environments. Preliminary investigation of commercial dynamics software packages led us to the conclude that they could use a commercial code to provide everything they needed except for the contact model. They found that ADAMS best fit the needs for a simulation package. To simulate intermittent contacts, they need collision detection software that can efficiently compute the distances between non-convex objects and return the associated witness features. They also require a computationally efficient contact model for rapid simulation of impact, sustained contact under load, and transition to and from contact conditions. This paper provides a technical review of a custom hierarchical distance computation engine developed at Sandia, called the C-Space Toolkit (CSTk). In addition, the authors describe an efficient contact model using a non-linear damping term developed at Ohio State. Both the CSTk and the non-linear damper have been incorporated in a simplified two-body testbed code, which is used to investigate how to correctly model the contact using these two utilities. They have incorporated this model into ADAMS SOLVER using the callable function interface. An example that illustrate the capabilities of the 9.02 release of ADAMS with the extensions is provided