Conceptual design of a miniaturized hybrid local actuator for Minimally Invasive Robotic Surgery (MIRS) instruments

The actuation mechanism of the tip of an endoscopic instrument is a major problem in designing miniature scale motorized instruments, especially when a high level of functionality and multi degrees of freedom (DOF) are concerned. We evaluated the different possible actuation methods for an endoscopic needle holder and proposed a new design of hybrid local-actuation, including a micro DC motor and a piezoelectric (PZT) actuator. The DC motor provided the long movement course required for opening-closing function of the gripper while the PZT guaranteed the high gripping force required for holding the needle. A compact serial configuration was considered for the actuators, producing an overall size of 10 mm in diameter and 39 mm in length, so that it could be implemented in the limited space available. The efficacy of the design was analyzed in a simulation study, using FEM and it was shown that the needle holder is capable to apply a sufficiently high gripping force of 22 N.