Research On Path Planning Methods Of Flexible Needle Puncture System

Minimally invasive treatment technology as a new medical technology is developing rapidly in recent years for living tissue pathology, directed drugs delivery in some organs. Needle insertion is perhaps the most widely used technique in these surgeries. However, the rigid needle used in the traditional surgery can only be punctured straightly so that many complex surgeries can’t be implemented.A special nickel-titanium alloy bevel needle is adopted in this thesis. This type of flexible needle can bend and generate arc trajectory, due to the lateral force of tissue on the needle bevel. This bending property of the needle can be used to avoid some sensitive obstacles (nerve, vein, bones and other vital organs) and reach the target accurately. Flexible needle must be combined with the ability of precisely control to perform an operation that human cannot complete. In this thesis, the robot-assisted puncture system with flexible needle is regarded as the research object. Based on kinematic model of the flexible needle, the path planning including two-dimensional plane and three-dimensional space are studied.Firstly, the flexible needle body coordinate system and the world coordinate system are proposed based on the characteristics of flexible needle trajectory, and transformation matrix between two coordinate systems is deduced as well. On the basis of the kinematic model deduced from unicycle model of the flexible needle, the multiform path styles including the straight, the circular trajectory and the multiple circular trajectories are analyzed, and the path planning of flexible needle based on three arcs is realized in the plane. Viewing minimally invasive operation and some reality issue, such as, multiple focuses of infection, multilayer tissue are deeply analyzed in the plane trajectory planning in this thesis. And the feasibility of the planning method is verified in this thesis.Secondly, aiming at the reality issue of flexible needle, three-dimensional space path planning is further studied. Three path planning strategies are proposed.1) Since the three-dimensional space can be composed by multiple discrete two-dimensional planes, the two-dimensional path planning can be directly generalized to three-dimensional path planning.2) According to the inverse kinematics of the robot,3D spatial optimal path with two arcs is proposed.3) Considering the advantages/disadvantages of the dynamic programming method and rapidly-exploring random trees (RRT) method, three-dimensional path planning of flexible needle based on rapidly exploring method is proposed. So the feasible path of local optimization can be quickly found. And then the feasibility of the three planning methods is verified in this thesis.Finally, the experimental platform is set up to complete the experiment. Using the path planning of two-dimensional plane, the path that leads to target and avoids obstacle can be obtained. The feasibility of this method is testified.In conclusion, the path planning of robot-assisted flexible needle puncture system is studied systematically. A series of trajectory planning method, including two-dimensional plane and three-dimensional space are proposed. During real needle motions the multiple focuses and multilayer can be solved in two-dimensional plane. And the path planning in three-dimensional space is proposed. This thesis has achieved good results, and part of the results has been testified by experiments. These achievements play an important role to advance the technology of robot-assisted flexible needle puncture.