Position-Based Time-Integrator for Frictional Articulated Body Dynamics

Abstract

We present a new time-integrator for modeling the frictional dynamics of articulated bodies. Our formulation represents the configuration of the articulated body using position variables and then uses those variables to model the friction forces between the articulated body and the environment. Our approach corresponds to a Newton-type optimization scheme that is guaranteed to converge so that it is stable with large timestep sizes. We evaluate the accuracy and stability of our time-integrator by comparing it with a conventional formulations based on the Newton-Euler equation and demonstrate the benefits on standard controller-optimization applications. We achieve 3-5 times speedup over a Newton-Euler-based simulator on a CPU. Our approach can be easily parallelized on a GPU and results in additional 4-15 times performance improvement.