Primary Workspace of Industrial Robots With Roll-Pitch-Yaw Wrists

Abstract

This paper presents a new method to identify the primary workspace of six-link industrial robots with Roll-Pitch-Yaw wrists in conjunction with four basic types of regional structures: the Cartesian, the cylindrical, the spherical and the articulated. The approach is to divide a robot into two subsystems, the regional structure and the wrist. Each subsystem is studied independently and then reassembled via a vector field analysis. Geometrical criteria are established to determine whether or not the kinematic connection between the wrist and the regional structure is valid. Conditions for a robot to access a point from a specified direction are derived first. The primary workpoints are then identified. Consequently, the boundaries of the primary workspaces (on the conservative side) of robots with Roll-Pitch-Yaw wrists, for the first time, can be analytically drawn. Some regional structures adopted in commercial robots which differ slightly from the standard ones are also included.