Kinematics analysis for a hybrid robot in minimally invasive surgery

This paper focuses on kinematics analysis for the 7-DOF (degree of freedom) hybrid robot in minimally invasive surgery. The serial structure of the hybrid robot has three DOF; the parallel structure of the hybrid robot has four DOF. First, the traditional method `D-H method´ is used to try to solve the kinematics of hybrid robot, but without success. Then a kinematics modeling method based on the ST (spinor theory) is presented. This method is named METM (multi-layer exponential transformation method). The process of solving the inverse displacements for all joints is analyzed. With this method, the joint displacements of 7-DOF hybrid robot are calculated. The METM method can be applicable for the kinematics of many hybrid robots, especially for redundant robots with more than six DOF.