Study On A Parallel Robot For Minimally Invasive Spine Surgery

Robot technology has been widely applied in the medical field due to to its high precision and high stability and other characteristics. However in the field of minimally invasive spinal surgery, the application of robot for clinical application is still rare because of some obstiacles such as the challenge of mobility of adjacent centrums. Even so, to apply the robot in minimally invasive spinal surgery is still appealing to both the surgeons and the patients because the robot can avoid the doctor in the operation of the wrong operation, can improve the operational flexibility, can eliminate the hand Tremor and reduce the doctor's learning curve, so spine minimally invasive surgery robot has become a hot topic in recent years in the field of medical robots.The paper has firstly finished the kinematic synthesis of a parallel mechanism for spinal surgery. A 6-SPS parallel mechanism has been choosen as the design prototype based on the particularity of the robot for minimally invasive spine surgery; and its kinematic synthesis has been achieved in terms of the specific size requirements, quality requirements,load requirements, workspace requirements and accuracy requirements; during which, the appropriate structural parameters has been determined elaborately. Try to solve the the problem that the precision and accuracy of the ball joint processing are difficult to be guaranteed, the design scheme of Hooke hinge and cylinder pair is adopted.In order to solve the inverse kinematics problem of the parallel robot, the basic theory of the motion description of the structure has been adopted , and the inverse solution of the parallel robot is deduced; while the a sufficient theoretical derivation and calculation has been presented, which lays the foundation for the following research on forwared kinematics , motion planning,and static analysis.The biggest obstacle of study on the paralle mechanism is the solution of the problem of forward kinematics. The analysis of analytic solution of forward kinematics has been proceed; and then it solve the problem via a positive solution based on numerical method to calculate the position of the BP neural network model, which establishes a mapping from the joint variable space to parallel robot platform pose variable space. The feasibility and validity of the forward kinematics solution of the model has been verified by the analysis of a large number of inverse sample data and model prediction data.In order to solve the problem of trajectory planning of the robot, the paper adoptes the maximum speed, the maximum acceleration and the maximum impact of each member as the reference index, and the trajectory planning of each member in the joint space has been carried out, while use a kind of acceleration interpolation function as the planning scheme of the combined curve, and makes full use of the advantages of various interpolation curves.Finally, the feasibility of the program is verified by Matalab graphical tools.Finally, the static analysis of the robot has been given. The geometric characteristics of 6-SPS parallel mechanism have been studied, based on the screw theory for the static equilibrium equation of force vector, which is established on the platform and 6 bars on the reaction mathematical relation between calculated static first order coefficient matrix and the axial force. Some cases has been given to verify the effectiveness ot this method, which is also provides means for the selection of driving parts.