Kinematic and Static Characteristics of In-parallel Actuated Manipulators at Singular Points and in their Neighborhoods.

Abstract

In the process of mechanism design and trajectory planning of in-parallel actuated manipulators, it is necessary to grasp the locations of all of singular points in the working space. This paper proposes a new method for numerically searching for the singular points of in-parallel actuated manipulators based on the pressure angle. A singular-point curve is defined as a set of singular points. Since the working space is divided into multiple regions by the singular-point curves, the end-effector cannot move freely from one region to any other regions. Kinematic and static characteristics at singular points are analyzed by pressure angles and instantaneous screw axes. Singular points of the Stewart-Platform are investigated based on the proposed method. Characteristics in the neighborhoods of singular points are analyzed from the points of view of output error, isotropy of output force and driving force, and the practical working space is defined.