A general kinematic method for R — θ type manipulator based on screw theory using dual-quaternion

The kinematic problem is an essential algorithm problem of the manipulator control. To improve the performance of the robots, it has been widely researched in robotics. In this paper, a general kinematic method for R-θ type manipulator is created using the combination of screw theory and dual-quaternion, it can be applied to different type of R-θ robot with different arm length. Screw theory provides a global geometric representation of the kinematics of manipulator which greatly simplifies the analysis of the mechanism and can avoid the singularities due to using local coordinates. With this method, the kinematics of the R-θ type manipulator is expressed by dual-quaternion representing the screw motion of each joint of the manipulator. By dual-quaternion only eight numbers are used to express a screw motion. Meanwhile, the motion transformation by dual-quaternion takes fewer calculations than the homogenous matrix. Thus, comparing with the traditional D-H parameter method, this method provides a compact, computationally efficient algorithm of kinematics of R-θ type wafer transfer robot which needs less storage space and does not suffer from singularity problem.