Enlargement of the Translational and Rotational Workspace of Parallel Robots

Parallel robot has excellent characteristics such as high speed, high precision and high rigidity. However, mechanical collisions between limbs, and complexly existing singular configurations restrict its workspace. In this paper, firstly, methods for expanding the translational workspace of the parallel robot are discussed. Parallel robot has multiple solutions of the inverse and forward kinematics. By changing its configurations from one solution to another, the parallel robot can expand its translational workspace. However, conventional non-redundant parallel robot encounters singularity during the mode change. Singularity free mode changes of the parallel robot by redundant actuation and asymmetrical design are introduced. Next, methods for expanding the rotational workspace of the parallel robot are shown. In order to achieve the large rotation, mechanical gimmicks by gears, pulleys, and helical joints have been embedded in the moving part. A differential screw-nut mechanism for expanding the rotational workspace of the parallel robot is introduced.