The general-linear-complex singularity of Stewart mechanism is a veryimportant problem in the parallel manipulator. Its general regularity is not found yet during thepast two decades. St-Onge and Gosselin pointed Out that the singularity locus of the Stewartmechanism at some given orientations of the moving platform should be polynomial expressions withvaried degrees in 2000, but they didn't formulate the expression. Based on the kinematicssingularity principle and the geometry condition proposed by Huang Zhen in 1999, firstly thesingularity equation in degree two is derived. It is a hyperbola when the orientation of the movingplatform is given. This result is also proved using screw theory. Then some singularity surfaces aregotten in three-dimensional space. This result is of important significance.
Li Yanwen Huang ZhenRobotics research Center,Yanshan University,Qinhuangdao 066004, China
