| Puncture interventional surgery is an important technique and development direction of clinical medicine.Compared with the traditional rigid puncture needle,the cannula flexible needle composed of a flexible cannula and an oblique tip flexible needle has the ability to avoid important organs and tissues,correct puncture deviations,and achieve precise targeted puncture.Due to the flexible bending characteristics of the cannula flexible needle,in order to realize the automatic control of the cannula flexible needle for targeted puncture,this paper studies the bending deformation model of the cannula flexible needle and the path planning algorithm based on the bending model.Based on the cannula flexible needle bending model of the theory of large deformation,the model parameters such as the discrete length are measured through experiments.It is compared with the kinematic model(wheel model)commonly used in current path planning algorithms to verify the advantages and accuracy of the mechanical bending model.Furthermore,the influence of different model discrete lengths on the bending model is analyzed.Through puncture experiments on cannula flexible needles with different needle cores extending from the cannula,the function relationship between the discrete length of the model and the length of the needle core extending from the cannula was established.By selecting a series of suitable discrete lengths,a family of mechanical bending model functions can be established as the basis for subsequent path planning research.The puncture path form of the cannula flexible needle is analyzed,and the path form of straight line and arc is selected for path planning.A rapid exploration random tree algorithm based on the mechanical bending model is proposed.Furthermore,the "find nearest function" method is proposed to determine the reachable path.Analyzing the reachable range of the cannula flexible needle,measuring the position and posture of the tip of the needle and the length of the cannula flexible needle.Furthermore,MATLAB was used to simulate the proposed algorithm and the feasibility of the algorithm was verified.Based on the proposed algorithm,a "single needle point multi-target puncture strategy" is proposed.In order to reduce the number of iterations of the algorithm,considering the evaluation criteria of the path,and comparing the difference between Euclidean distance and cosine similarity method,a "find the next target point" algorithm based on cosine similarity is proposed.Furthermore,in view of the situation where the needle entry point cannot reach the target point,the "multiple entry needle point and multiple target point puncture strategy" is proposed.The feasibility of the two methods is verified by simulation.Finally,Nitinol is used to process the cannula flexible needle.Through analysis and comparison of the characteristics of different types of human body simulation tissue materials,a suitable bionic tissue is selected for puncture experiments.Perform error analysis on the results to verify the accuracy and feasibility of the proposed algorithm.This paper mainly studies the path planning algorithm of the cannula flexible needle based on the mechanical bending model.Based on the cannula flexible needle bending model of the large deformation theory,the mechanical bending model function family is obtained,the RRT algorithm based on the mechanical bending model,the multi-target puncture strategy with single needle point and the puncture strategy with multiple needle points and multiple targets are proposed,and experimental verification the effectiveness of the proposed algorithm is provided,which provides theoretical and experimental basis for the realization of automatic control the cannula flexible needle for targeted puncture. |
