A Novel Method For Knot Tying Of Suture With Surgical Robot

A surgical robotic system can make the best use of both a doctor's experience and the characteristics of precise positioning, stable performance and dexterous manipulability of a robot, which make it possible for a surgeon to accomplish a fine operation with a comfortable manipulation environment. The surgical robotic systems have greatly extened the surgeon's capability, improved the quality and security of a surgery, shorten the cure time and reduced the cost. Suture and knot tying is an important and difficult task for a surgical robot. Because of the nolinear deformation of the suture during a robotic knot tying, the operation time is much prolonged. In order to improve the precision and efficiency, we must study the rules of robotic knot tying of the suture.Based on the design principle and the required workspace of the clinical microsurgery, we develop the master-slave microsurgical robotic system,"MicroHand"system. The slave manipulator adopts the RCM (Remote Center-of-motion) structural style. The orientation mechanism applies three rotating axes intersecting at one point, the position mechanism can implement the kinematic characteristics of a double parallelagram mechanism driven by a cable, which can decouple the position and posture of the slave manipulator and ensures that the surgical tools have enough dexterity at any position in the workspace.According to the kinematic conditioning index, we make the dimensional synthesis of the"MicroHand"system and draw the following conclusions: If the first three links have equal length, and link I and link III are orthogonal, the position mechanism has the best kinematic conditioning index.According to the kinematics equations of the master and slave manipulators, we obtain the single and cooperation workspaces of them with Monte Carlo method. With the maximal co-workspace as the objective function, we can deterimine the optimal layout of the"MicroHand"system and the appropriate proportional coefficient of master and slave manipulators is determined as 6:1.According to the force analysis of the sututre, we present a model of the suture taking its gravity into account, which can work out the optimal suture length during the robotic knot tying, and introduce the conception of"suitability regulation ratio of...