Simplifying Dynamic Models for Parallel Robots by Introducing Virtual Degrees of Freedom

This paper analyzes a simplified dynamic modeling method based on the Newton-Euler method for parallel robots, in which additional virtual degrees of freedom (DOFs) are introduced to reduce the number of unknowns in the force/torque equations. These virtual DOFs can release the redundant constraints for over-constrained robots. For statically determined robots, the extra DOFs should be introduced as local DOFs to retain the original kinematic properties of the end-effector. For some robots, based on virtual DOFs, a simple point mass assumption can further reduce the number of unknowns in the dynamic model at the expense of accuracy. Besides, the processes to solve the dynamic model of such robots can be drastically simplified by some model-solving strategies.