Type synthesis of 5-DOF parallel manipulators based on screw theory

Abstract

With the introduction of virtual chains to represent the motion patterns of 5-DOF motions, a classification of 5-DOF PMs (parallel manipulators) is proposed at first. A general method for the type synthesis of 5-DOF PMs is then proposed based on screw theory and using the concept of virtual chains. The type synthesis of US-equivalent PMs is presented in detail to show the application of the proposed approach. US-equivalent PMs are the parallel counterparts of the 5-DOF US serial manipulators. For a US-equivalent PM, the moving platform can rotate arbitrarily about a point moving along a spherical surface. The type synthesis of legs for US-equivalent PKCs (parallel kinematic chains), the type synthesis of US-equivalent PKCs, as well as the selection of actuated joints of US-equivalent PMs are dealt with in sequence. US-equivalent PKCs with and without inactive joints are synthesized. Several US-equivalent PMs as well as other classes of 5-DOF PMs with identical type of legs are obtained. © 2005 Wiley Periodicals, Inc.