The singularity principle and property of Stewart Parallel manipulator

Based on the kinematic relationship of rigid body, this paper presents a new principle and method to analyze the singularity of a Stewart parallel manipulator. We study the sufficient and necessary condition that three velocities of three non-collinear points in a body can determine a screw motion. All singularities of the Stewart parallel mechanism are classified into three different linear-complex singularities. The various algebraic and geometrical properties as well as kinematics ones are analyzed in detail in different singular configurations. With the condition above, the singularity loci and distribution characteristics of a 3/6-Stewart parallel manipulator for some orientations of the mobile are studied in an oblique plane and in three-dimensional space. (C) 2003 Wiley Periodicals, Inc.