“…To develop intuitive and visual methods of axode planning, we especially study the distribution regularity of the screw axes of the general three-system in Euclidean three-space. Furthermore, to build a bridge between axode planning and the motion planning of parallel mechanisms, we have developed a kinematic model of screw rolling between fixed and moving axodes [19,20], which solves the problem, "Given a pair of fixed and moving axodes, how to reproduce the associated continuous rigid motion?" For the distribution zone of the screw axes of higherorder screw systems, perhaps it can be decomposed into that of lower-order screw systems, as Chen [2] has decomposed the four-, five-, and six-systems into the direct sums of several two-and three-systems by the decomposition of the positive semidefinite (PSD) method.…”