Dynamic active constraints for robot assisted minimally invasive surgery

摘要

In recent years, robot assisted Minimally Invasive Surgery (MIS) is playing an increasingly important role in surgery. Although the benefit of reduced patient trauma and hospitalisation with improved prognosis has been achieved through the enhanced dexterity and accuracy of instrument manipulation by the introduction of robotic assistance, the use of current master-slave platform has inevitably imposed the increased physical separation that deteriorates the hand-eye coordination due to a lack of haptic feedback. To this end, the concept of Virtual Fixtures (VFs) and Active Constraints has attracted significant research interests. It provides in situ effective guidance of access routes to the target anatomy safely. However, its clinical potential is only well established for procedures such as orthopaedic surgery, which are conducted under a static frame-of-reference due to the relatively rigid anatomy involved. The main focus of this thesis is concerned with modelling spatial constraints that are adaptive to tissue deformation. These constraints define safe manipulation margins for an entire robot rather than just its end-effector. An analytical framework is proposed to control an articulated flexible robotic device. Provided with these dynamic active constraints, the framework enables the operator to perform smooth articulation or steady navigation along curved anatomical pathways even under rapid tissue deformation. The challenges induced by hyper-kinematic redundancy of the robot and increased computational burden of real-time haptic rendering are addressed so that they facilitate seamless interaction with the robot by using lower degree-of-freedom (DoF) haptic interfacing device. Furthermore, the use of a gaze contingent paradigm is also investigated to enhance the human-robot interaction by linking the manipulation constraints with visual track. To demonstrate the practical nature of the proposed framework, detailed quantitative validations were conducted on groups of subjects. Future directions and potential improvements to the proposed techniques are finally outlined.