The Behaviors Of Suturing And Knot-tying In The Robot-assisted Minimally Invasive Surgery (MIS)

It is difficult to perform robot-assisted suturing and knot-tying tasks although minimally invasive surgery (MIS) robotic systems have been developed greatly. The qualities of the suture and knots formed in robot-assisted MIS are worse than that in MIS performed directly by surgeons. In order to solve the problems of robot-assisted suturing and knot-tying in MIS, the research in this dissertation focuses on the behaviors of MIS robot-assisted suturing and knot-tying tasks. The contents of this dissertation are introduced briefly.1. Analysis and abstract of the motions of robot-assisted suturing and knot-tying tasks in MIS.The motions of the suturing and knot-tying tasks are decomposed and abstracted into six basic types of motions, which are"Reach"(m1),"Rotate & Orient"(m2),"Grasp & Hold"(m3),"Push"(m4),"Pull"(m5), and"Release"(m6). Frequency and effective acting time of each type of the motions in the suturing and knot-tying tasks are analyzed. And the workspace and the end-effectors required by the motions are introduced.2. The presentation of surgical knots: digital code matrix of a knot.According to the analysis of the motions of the suturing and knot-tying tasks and different throws formed in the knot-tying process, based on knot theory, the orientation surgical knot is modeled. The crossing points, the writhe of a throw, the position of the two strands which consist of the throw and other topological information of the throw compose the digital code matrix of a throw. The usual throws of knots are collected into the throw set. Each of the elements of the throw set is named a throw element, which maps to a code matrix of a throw. The code matrix of a knot which comprises of throw elements is the union of the code matrices of the throw elements. The digital representation of surgical knots proposed in this dissertation benefits the surgical robotic systems to identify the configuration of a knot in the knot-tying task. 3. The suturing path planning and the Bending-Twisting Knot-Tying (BTKT)algorithm in a confined workspaceIn the suturing task, the most important factor of the operating workspace is the trajectory of the needle inside the tissue. The path inside the tissue is planned for an 8mm 3/8 needle according to the principles of the suturing task. The BTKT method is a novel method of forming a stable loop. With this method, the suture is grasped by the end-effectors which move along their axes and rotate themselves. Then the suture is bent and twisted with the tendency to reduce its energy. The suture forms a stable loop when its energy reduces to zero. After one end-effector forms a stable loop with BTKT method, the jaws of the other end-effector bending and the whole end-effector rotating, the end-effector adjusts its posture. Then the end-effector grasps the free strand of the suture and pulls the strand through the loop. Thus the preparatory simple knot is formed. Grasping the strands of the suture vertically, the end-effectors both rotate themselves until it makes the strands of the suture enlace the axes of the end-effectors and tighten the knot. The whole knot-tying process is named by BTKT algorithm. The suturing path planning and the BTKT algorithm, which facilitate surgeons to perform the robot-assisted suturing and knot-tying tasks in laryngeal MIS under a thin and long self-retaining laryngoscope, are of the clinical importance.4. Suturing and knot-tying simulation and experiments assisted by MIS surgery robotic systems.Suturing and knot-tying simulation and experiments assisted by"MicroHand"series surgery robotic systems are performed. The factors on the Bending-Twisting Knot-Tying (BTKT) method are analyzed. The simulation and experiments validate the code matrix of a knot, the suturing path planning and the Bending- Twisting Knot-Tying (BTKT) algorithm.