Type synthesis and analysis of rotational parallel mechanisms with a virtual continuous axis

Having virtual continuous axes is an important mechanism performance required by the motion tracking and simulating mechanisms for large-scale heavy-weight apparatus. Mathematical criteria for a virtual continuous axis using virtual coefficient theory is proposed through geometric modeling continuous rotation of the constrained rigid body and a virtual continuous axis. A type of synthesis approach for rotational parallel mechanisms (RPMs) with a virtual continuous axis is given and a type of RPM with arc-rail-slider or cross slipper is constructed. On the basis of screw theory, degree of freedom (DoF) and properties of the axes of a typical RPM with a virtual continuous axis are analyzed, and the inputs selection and arrangement are also discussed. The kinematic and dynamic models of the RPM are established. Finally, a numerical example and a solution to the motion simulation for super-large-scale heavy-weight apparatus are given.