| In this paper,we present a novel MRI-compatible needle insertion robot for breast cancer.Base on the clinical surgery requirements and restricted conditions in the MRI environment,a cable-driven robot mechanism and control system were designed.Next,experimental studies about needle insertion accuracy and MRI compatibility test were performed to validate the performance of the new robot.The main contents and research results are as follows:First,according to the clinical requirements and modularization design idea,a compact three degree-of-freedom(DOF)serial mechanism was designed,including the body support structure module,the main implement structure module and the breast holder module.Nest,Optimal path planning algorithm based on the breast holder was proposed.In this paper,the Denavit-Hartenberg(D-H)method was applied to analyse the kinematics.The appropriate workspace of the robot was calculated by using the forward kinematics final equation.The joint variables were calculated by the inverse kinematics.Furthermore,a physical prototype of the robot was manufactured and assembled.Secondly,the cable transmission was proposed to confirm the large enough workspace and compact mechanism.To confirm the cable-driven robot can work steadily,a series of critical technical problems about cable transmission were proposed.An ideal cable material named Kevlar was selected to transfer motion and torque in this robot according to the MRI compatibility test of cable materials and cable transmission test.Furthermore,in this paper,the curve interpolation and fitting method was applied to compensate for the cable-driven error,which can improve mechanical accuracy.Thirdly,the control system based on the motion control card was completed,according to the requirements of the control system design in the MRI environment,including the hardware and software design.The hardware design: ultrasonic motors were applied in the control system.In addition,fibre optic encoders can obtain the rotation angle information.The MRI compatibility of the control system can be improved by the means described above.The software design: the design of software program based on the LabVIEW and logic control flow were completed.Finally,the experimental studies about needle insertion accuracy in the laboratory environment and MRI compatibility test in the MRI environment were performed.The results show that the robot can be applied in the MRI environment and the mean needle insertion accuracy is 0.77 mm which can meet the clinical requirements. |
