The Dynamic Equations of Motion and Actuation Scheme for the Tetrahedron Based Variable Geometry Truss Manipulator

Abstract

Abstract The Variable Geometry Truss Manipulator (VGTM) is a truss structure composed of tetrahedron elements stacked upon each other. Although this manipulator is geometrically different from a serial link manipulator, it is kinematically equivalent to the serial link manipulator whereby the difference in construction lies in its 120° twist angles instead of the more common 0° or 90°. A study of the dynamic behavior of a manipulator is important for simulation of the motion of the manipulator, designing suitable control equations and for evaluating the kinematic design and structure of the manipulator. In this paper the dynamic equations of motion have been derived for the VGTM. The different components of the torques have been computed using the Lagrange-Euler equations with the intention of studying the contributions of each term. In addition, two actuation schemes for the VGTM have been studied: actuation at each joint axis and actuation at the apex of each triangular element. The motor requirements for each scheme have been obtained and compared. A case study has been performed for a typical trajectory this manipulator.