Dynamics simulation of humanoid robots with position-controlled joints and closed kinematic chains

This paper presents a dynamics simulator that can handle complex robotic systems including position-controlled joints and closed kinematic chains. We first extend our prevous algorithm for linear-time forward dynamics algorithm to handle closed kinematic chains. The extended algorithm is formally presented for the first time. We then present another extension that allows position-controlled joints, whose angles exactly follow the reference by perfect servo controllers. This feature is often useful for simple trial simulations only using joint angle commands because the user does not have to design low-level servo controllers for simulation. The simulation can also be performed without precise friction parameters. The algorithm is tested on a humanoid robot having toe joints with four-bar linkage structure.