Study On The Structure Design And Motion Control Of Active Flexible Needle Driven By Flexible Cable

At present,minimally invasive intervention is a new medical technology developed rapidly in recent years.It is widely used in clinical surgery and has become a hot subject.The use of "flexible needle" instead of traditional "rigid needle" is a groundbreaking thinking that overcomes the above drawbacks of rigid needle.However,there is also a bottleneck problem for oblique flexible needle: the bending radius is relatively fixed,which leads to the limitation of ability to correct the deviation of path and inflexible puncture path form.An active flexible needle driven by a flexible cable is proposed,which can change the magnitude and direction of the force acting on tissue by actively driving the oblique tip to swing,so as to change the bending radius of flexible needle puncturing in tissue and effectively solve the bottleneck problem of passive flexible needle..Firstly,the structure of cable-driven active flexible needle is designed and optimized.Unlike ordinary puncture needles,the active flexible needle consists of an outer needle and an inner needle slotted on both sides,and there are two thin flexible cables in the inner needle grooves that pass through and pull the needle tip.The structure and force between them are relatively complex,and there will be coupling between the inner and outer flexible needle cable when bending and deforming.The structure optimization of active flexible needle was studied,aiming at the flexibility of bending and the stability of stress and deformation,the structure of active flexible needle was optimized.The optimization is mainly divided into the optimization of the angle of oblique tip,the optimization of needle tip length,and the verification of slotted structure of the inner needle.The structure optimization of cable-driven active flexible needle is realized by experiment and ANSYS static simulation..Secondly,the transmission characteristics of flexible cable are basis of the research on precise control of active flexible needle.Starting from the mechanical properties of material,the mechanical properties of thin flexible cable are studied in depth.And they are improved and optimized by means of materials and mechanics.Based on this,the transmission characteristic model of cable is established.The key problems of the cable transmission characteristics are studied.Firstly,according to the Euler formula in ideal states,the tension ratio of cable is studied.Then,under non-ideal states,the bending stiffness,nonlinear friction and elastic extension are considered respectively to study the mechanical characteristics of thin flexible cable.The cable's tension ratio formula is obtained.Next,the control equation of cable's extension is deduced.Finally,the transmission characteristics of thin flexible cable are studied,and the specific relationship between the cable tension and the coefficient of friction between the cable and sheave is obtained.Thirdly,kinematic modeling and related kinematic calculations of cable-driven active flexible needle are carried out.The skew unicycle model is proposed and the kinematics modeling,kinematics calculation and parameter identification of the skew unicycle model are conducted.Finally,experiments simulating human tissue puncture were carried out,relevant bionic tissue were prepared and puncture experiments were conducted.The puncture experiments using active flexible needle were carried out to verify the proposed skew unicycle model,and the result of parameter identification was verified.The correctness and rationality of the proposed kinematic model and parameter identification results were finally proved.In this paper,the research on the puncture of cable-driven active flexible needle is carried out.The basic structure of cable-driven active flexible needle is designed and optimized.The suitable flexible cable is chosen from the perspective of the mechanics of materials.The mechanical characteristics and key problems involved in the cable drive are studied.Then,the kinematics modeling and parameter identification of cable-driver active flexible needle are carried out.Finally,the rationality of kinematics modeling and parameter identification of active needle are verified by experiments.