Study On The Modeling And Control System Of Magnetic Resonance Imaging Guided Needle Insertion Robot For Breast Surgery

In this research,a surgical robotic system,which is used in biopsy and brachytherapy for small core breast cancer under magnetic resonance imaging(MRI)guidance is developed.This system belongs to an interdisciplinary between medicine and mechanical engineering,whose contents consist of designing,modeling and controlling of MRI guided robot.The main research work and achievements in this paper are as follow:Firstly,robot designing is accomplished.The robot is a kind of serial mechanism and is divided into 3 main modules.We apply tendon-transmission into the system to provide actuation power for the robot.In this way,the robot manipulator will be smaller and more compatible in MRI device.The forward and inverse kinematics of the robot are carried out through D-H method,which also proves the feasibility of the designing.Then a prototype of the robot has been manufactured using non-ferromagnetic materials.Secondly,dynamical model is built.Dynamics of the robot manipulator are modeled through Lagrange method,and the dynamical characteristics of the robot can be observed by simulating the proposed results.Based on LuGre friction model,a consistent dynamical model for tendon-sheath transmission has been built by dividing the tendon into n segments.The results of simulating the tendon-sheath transmission shows 4 phases which are called the hysteresis behavior.Thirdly,controlling algorithm is designed.After simplifying the dynamical model of the robotic system,we design a kind of sliding mode controller(SMC),and then add fuzzy logic into the controller for the purpose of reducing chattering problem in SMC.Moreover,a kind of friction compensator is designed to offset the influence from simplifying dynamical model.At last,experiments are conducted.An experiment on 1-dof tendon-sheath transmission has been done to provide experience about how to install the system and place the robot actuator.Results of the experiment shows that tracking error of 1-dof tendon-sheath transmission remains less than 0.55 mm.Another experiment on needle insertion has also been done to investigate the efficiency of the whole robotic system,whose results show that the average error of insertion is 0.68 mm.