Dynamic modeling of a two-DoF rotational parallel robot with changeable rotational axes

Abstract

Because of the outstanding capabilities to realize flexible orientations, the specific category of rotational parallel robots with changeable rotational axes have a wide application in design of bionic eyes, dexterous wrists, tracking and pointing devices. A two-DoF parallel robot in this category called Helix is studied in this paper. Employing a finite and instantaneous screw based method, dynamic modeling and analysis of Helix robot is presented, which provides a theoretical foundation for performance design and dynamic control. Firstly, concept description and inverse kinematics of Helix robot is given, which is the prerequisite for dynamic modeling and analysis. Secondly, twist and wrench based velocity, force and acceleration analysis of this robot is carried out, resulting in the Jacobian and Hessian matrices which are obtained through directly differentiating the finite screw based topological model. Then, using these matrices, its dynamic equation is formulated considering the gravity of each component. Finally, the obtained dynamic model of Helix robot is verified through comparing the simulation results in ADAMS and Matlab software. The finite and instantaneous screw based method used in this paper is a generic one which is suitable for dynamic modeling of different serial and parallel robots.