Mechanism Design And Dynamics Analysis Of A MRI-guided Surgery Robot

This paper is focused on the magnetic resonance imaging (MRI) guided needleinsertion robot for prostate brachytherapy. The mechanical subsystem of the robot isdeveloped and the kinematics and dynamics of the robot are researched. The maincontents contain the selection of the robot structure material, drive method and sensor,mechanism design, kinematics and dynamics modeling and so on. Combined with thecontrol system which has been established, acupuncture experiment to the robot forkinematic accuracy is verified. The main research contents and achieved results aredescribed as follows:Firstly, in order to meet the design requirement of MRI-guided prostate needleinsertion surgery robot, polyformaldehyde (POM) is chosen as the main material forthis robot prototype, and hierarchical modular design is adopted for integral structureof the robot. MR compatible encoder is selected for the mechanism position sensor,and hybrid drive method with combination of pneumatic and ultrasound motor isemployed, realizing the adjustment of needle space pose.Secondly, base on the robot kinematic analysis, the forward and inverseequations and Jacobin matrix are deduced, and then the workspace of the robot iscalculated, verifying the rationality of robot design theoretically. A dexterityevaluation index which gives attention to the mechanism and workspace dexterity isdeveloped, and an optimal kinematics performance evaluation index which minimizesthe global and comprehensive conditioning number is proposed. The kinematicdimensional synthesis is carried out by the above methods and the main dimensionalparameters of the optimal structure are obtained.Finally, Lagrange method is used for establishing the dynamic model of therobot. Base on the model and the frictions between main kinematic pairs, the cylinderdrive force is analyzed in the process of the mechanism motion. Needle insertionexperiments are conducted to verify the correctness of mechanism kinematicsderivation and control theory, and evaluate the needle insertion accuracy of themechanism at the same time.The research results of this paper have high theoretical significance and practicalapplication value. The research results have a certain exploratory significance in the design of MRI-guided surgical robot. The results described in the paper also lay goodfoundations for the following up work.