The effect of manipulator gripper stiffness on teleoperated task performance

During robot-assisted minimally invasive surgery, surgeons perform challenging dexterous tasks, including the manipulation of soft tissue and suture tying. In the absence of environment force sensing of tool-tissue interaction forces to provide force feedback, surgeons must rely on visual feedback to modulate the grip force they apply on the environment. Clinical systems, like the da Vinci Surgical System (Intuitive Surgical, Inc.), use physical springs to provide closing resistance on the gripper degree-of-freedom (DOF) of the master manipulator. This feedback provides increasing force resistance as the gripper is closed. To determine the effect of master manipulator gripper stiffness on performance in a teleoperated manipulation task, we designed a new and open source gripper, the OmniGrip. The OmniGrip attaches to a SensAble Phantom Omni (now available as Geomagic Touch), replacing the stySensAble Phantom Omnilus end effector, and providing the ability for user programmable force characteristics. We conducted a study in which participants used an OmniGrip to teleoperate a Raven II surgical robRaven II surgical robotic systemotic system in a pick-and-place task. Increasing the stiffness of the OmniGrip resulted in reduced interaction forces at the slave-side environment. Additionally, these interaction forces were significantly lower when the OmniGrip as compared to when using the Phantom Omni stylus.