Spine-kinematics with constraint guidance for robot supported MIS-instruments

Feedback of interaction forces/torques in robot supported minimally invasive surgery (MIRS) meanwhile is a widely accepted advantage. To avoid parasitic effects on the according force/torque sensor, e. g. due to friction in the trocar, a sensor integration as distal as possible is advisable. Since common sensor principles are based on wire or fibre connection and since an axisymmetrical instrument's distal end has to be actuated in at least one additional degree of freedom (DoF) for full dexterity inside the patient, cable (or fibre) break is a serious problem. A constraint guided spine-kinematics without rotatory DoF at its distal end is proposed to reduce the danger of cable (or fibre) break due to a curved flection instead of a sharply bending joint. The properties of a constraint spine-kinematics with one DoF adapted to the special requests of an in-house developed MIRS-system is presented, verification data acquired in a specially developed test bed are shown. The results seem suitable for MIRS applications and for a progress towards a 2 DoF solution with the presented constraint principle.