Structural Synthesis of Robot Manipulators by Using Screw with Variable Pitch

Abstract

This paper focuses on the systematic type synthesis of parallel robot manipulators by using new structural formulas based on the screw theory. New structural formulas as a total number of screw in kinematic pairs <img src=image/15112785_01.gif>, number of screws with variable pitch <img src=image/15112785_02.gif>, total number of screws that represent the contact geometry of lower and higher joint elements (t), mobility equation for robot manipulators (M), dimension of the closed loop <img src=image/15112785_03.gif>, motion of end effector of parallel manipulator <img src=image/15112785_04.gif>, number degree of freedom of kinematic pairs <img src=image/15112785_05.gif>, refers to find the kinematic structure of robot manipulators realizing a specified motion requirement. Twenty kinematic pairs with structural parameters <img src=image/15112785_06.gif> are introduced. History of six structural formulas using for structural synthesis of parallel robot manipulators from space and different subspaces are presented as a table with equations, authors, years and some commentaries. The structural synthesis approach is based on the elementary notions of screw theory. Using the proposed of structural formulas approach, families of platform manipulators are constructed from a set of structural units. This paper is appropriate for engineers with interest in robotics, rovers, space docking parallel manipulators and screw theory.