Design And Experimental Research Of Cable-Driven Puncture Surgical Robot For Flexible Needle

Targeted puncture surgery is minimal invasive surgery using puncture needle.The medicine,ablation probe and radioactive seeds can be taken to focus finishing biopsy sampling and tumor-targeted therapy.The flexible needle can be controlled to puncture along curvilinear path in tissue.The blood vessel,bone,organ and other non targeted tissue are avoided.Flexible needle is applicable to more complex surgeries and reduces postoperative pain and sequela.However,the accuracy and efficiency are lower when the surgeon manually manipulates the flexible needle due to the microsize and hand shake.Therefore,it’s necessary to design robotassisted puncture device for flexible needle which is beneficial to improve the targeted puncture accuracy and efficiency.To address the above issues,this paper conducted researches on puncture mechanism synthesis,path planning,prototype test and other works for flexible needle.Design of robotic cable-driven mechanism.Firstly,the controllable bending principle of flexible needle in tissue is explored.Kinematic model of flexible needle is established.The design requirements of cable-driven puncture robot are clarified.Taking the advantages and design methods of cable-driven mechanism in surgical robots,the cable-driven mechanism synthesis is conducted.Keeping the mass drive module away from the joints.In view of motion coupling of cable-driven mechanism,the coupling principle between needle insertion joint and needle-tip orientation joint is conducted.Motion decoupling mechanism synthesis based on movable pulley is also conducted.The motion decoupling reliability is improved.In order to avoid buckling during needle insertion,a buckling suppression method using combined needle is proposed.The needle core with higher elastic modulus is inserted into needle tube,the critical load of needle is improved without reducing the needle stroke.Robot kinematics and cable-driven system modeling.The robot kinematic model is established based on screw theory.The area with higher manipulability of robot workspace is analysed.Transmission error modeling of cable-driven system is conducted.The relationships between capstan speed,radius,pitch and transmission error are determined which is utilized to complete the optimal design of cable-driven mechanism.To control needle insertion force more precisely,the cable transmission efficiency model is established on the basis of tension loss caused by cable bending.The relationships between pulley radius,cable radius,material parameters of transmission parts and tension transmission efficiency are determined.The optimal design and lectotype of cable transmission parts are finished.Puncture path planning and construction of motion control system.Based on rapidlyexploring random tree algorithm(RRT),motion constraints of flexible needle are introduced into puncture path planning.In view of needle-tip position change during needle body rotating around the needle axis,priority is given to expanding the puncture depth in the current bending direction during path planning.The number of needle-tip orientation is reduced and multiple feasible paths are obtained ultimately.The comprehensive optimal path is selected using multiobjective optimization algorithm.Based on the above work,a path planning GUI for flexible needle is developed.Drive motor lectotype is carried out,and motion control system of flexible needle puncture is established.A motion control interface based on LabVIEW is also developed.Prototype test and puncture experiments.The prototype with optimized mechanism parameters is processed and assembled.The motion performances of needle insertion joint and needle-tip orientation joint are tested.The coupling error can be eliminated effectively by the proposed motion decoupling mechanism within the allowable error range.Error compensation control experiment is conducted which introduces cable transmission error model and joint motion hysteresis into robot motion control algorithm.The joint motion accuracy is improved.Repeated puncture experiment of flexible needle is carried out,needle puncture data with different insertion length are obtained and puncture repeatability within 3σ confidence interval is calculated.Finally,the obstacle avoidance path planning and puncture experiment of flexible needle is conducted.In multiple puncture experiments with insertion length of approximately 100 mm,the flexible needle can be driven to avoid obstacles and reach the target area along the planned path.