Detecting Singularities of Stewart Platforms

Abstract

A Stewart platform, also known as a hexapod positioner, is a parallel manipulator using an octahedral assembly of struts. There are six independently actuated legs, whose lengths determine the position and orien- tation of the platform. These devices may display instabilities associated with architectural singularities and the purpose of the present study is to propose an approach for their detection. The main point is the formulation of the di- rect problem (given the leg lengths, find the position and orientation, velocity and acceleration of the platform) in an appropriate coordinate system based on quaternions.