Design of Remote Center of Motion Endoscope Manipulators With Mechanical Safety Features

Abstract Robot-assisted surgical systems comprising manipulators with remote centers of motion are quite popular in minimally invasive surgery applications. This article examines the mechanical safety features for such manipulators in three levels: design of the mechanism with a remote center of motion that does not interfere with the surgical tools and the surgeon, gravity balancing of the mechanism, and utilization of series elastic actuators with variable stiffness. First, alternative kinematic structures in the literature are examined, and a novel serial kinematic architecture for minimally invasive surgery applications is proposed as a serial three degrees-of-freedom manipulator with a circular arc. Gravity-balancing solutions with springs and/or counter-masses are evaluated. Series elastic actuator designs are discussed, and a new solution developed for gradually softening behavior is presented. The investigated safety measures are applied to an endoscope-holder manipulator for endonasal skull base surgeries as a case study. The design and prototype tests of the gravity-balanced manipulator and series elastic actuators are presented. The effectiveness of the mechanical safety measures is verified via the test results.