Development of Spatial Parallel Manipulators with Six Degrees of Freedom

Abstract

In the present paper, kinematic structures of spatial 6-degree-of-freedom (dof) parallel manipulators are obtained by a number synthesis of multiloop linkages which consist of pairs with 1, 2 and/or 3 dof and have no moving closed loops. Concerning simple and practical manipulators among the obtained ones, that is, concerning the parallel manipulator consisting of six arms, each of which has three revolute pairs and a spheric pair, analytical equations for inverse and direct kinematics are derived and singular positions where the configurations of the manipulator cannot be defined are discussed. Moreover, taking account of allowable pressure angles and maximum swing angles of spheric pairs, the relation between the working space and parameters of the manipulator is investigated, revealing that the manipulator can operate with larger vertical motions than the Stewart Platform.