Research On Torsional Deformation Modeling And Angular Displacement Error Compensation Of Flexible Needle

The research object of this paper is the torsional deformation during flexible needle twisting inside tissue.The angular displacement error formula of the flexible needle under a steady state is derived.The finite element simulation for the deformation of flexible needle and soft tissue are conducted.In addition,the experimental verifications of angular displacement error compensation methods are conducted.The detailed research contents and results of this paper are as follows:Firstly,the frictional torque is measured under needle straight trajectory and curving trajectory inside tissue,and the influence of various factors on frictional torque is analyzed.The torsional friction model is established when the needle is rotated under a steady state inside tissue,and the formula of angular displacement error between needle tip and needle base is derived.Secondly,the models of flexible needle and soft tissue are established in the finite element analysis.The needle twisting deformation and tissue deformation are analyzed,and the values of flexible needle angular displacement error and tissue two-dimensional deformation are obtained.The tissue deformation simulation is extended to three-dimensional pelvic organ groups by combining the anatomical knowledge with 3D reconstruction technique,and the deformation value of prostate under needle rotation is calculated.At last,the experimental platform is built,and the experimental verifications of angular displacement error compensation methods are conducted.The valid value of needle retraction distance is analyzed,and the experimental results show that the frictional torque can be reduced by 63.4% when the needle is retracted 3 mm.The torsional dynamic model of flexible needle is derived,and the angular displacement error compensation experiment is conducted by combing torsional dynamic model with control system.It turns out that the needle tip offset can be reduced by 65%.The research results are contributed to understand the mechanism and compensation method of the flexible needle angular displacement error during operation and promote the accuracy of flexible needle control.It is of great significance for the error control of medical operation and the acquisition of better surgical results.