The Design And Master-slave Control Of Interventional Catheter

With the rapid growth in the incidence of cardiovascular disease, vascular interventionalprocedures, as a safe, efficient and low-cost surgical method, has became a research hotspot in recentyears. However, conventional minimally invasive surgery has deficiencies in many aspects.Structurally, the traditional interventional catheter’s poor versatility and initiative seriously affect theeffectiveness of interventional procedures. In the control mothd, the traditional catheter is difficult tomanipulate and keep accuracy, which set a higher requirement for the operators’ techniques.Additionly, effective detection of the contact force between vessel and interventional catheter end failto realize in the traditional surgery, which buried security risks in the procedure.According to traditional interventional catheters’ poor versatility and initiative, a modularhybrid-driven interventional catheter is presented in this paper, which consists of one cable-driveninitiative unit and several SMA-driven initiative units in series. Each initiative unit is connected by adetachable elastic structure, the surgery operators can select appropriate units for certain surgicalenvironment, then quickly assemble them. The control of each catheter unit’s posture can be realizedthrough driving the catheters or SMA springs, and this structure solves the coupling problem ofdrivers’ length, which improves the control precision of the catheter.Basing on the designed structure, the forward kinematics models for the single and multiplesegements catheter units are established through D-H parameter method, and their workspace aresolved. The single catheter unit’s inverse kinematics, Jacobian matrix and singular configuration isalso solved in this paper. This initiative units’ assembly structure makes the drives’ length can realizedecoupling control, thus the relation between the length of the initiative units’ drives and the initiativeunits’ posture is studied in this paper. According to the characteristics of the drives, two models areestablished in which the drive is equivalent to line and arc. By comparing the simulation andexperimental results, the relationship between the lengths of drives, including cables and SMAsprings, and the posture angles of catheter unit is fitted out, setting the foundation for master-slavecontrol.Three DOF haptic devices falcon is selected as the master handle of the system. The positiontracking program for the handle is made under VS08environment with C++language, through whichthe workspace is measured. According to the measured workspace of the handle, point-to-ponitmapping relation is established from the workspace of handle to the workspace of the catheter end, and its transform matrix is solved. The open-loop incremental control mode and the closed-loopJacobi control mode for the end catheter unit is also established in this paper, as well as theincremental master-slave mapping realition and its control diagram. The specific operating steps forthe closed-loop Jacobi control is explained. To achieve successful intervention, the three-point pathplanning algorithm and the integral path planning algorithm are established in this paper. Accordingto these two algorithms, the path planning procedures for the catheter interventional is established.In order to achieve virtual force feedback between the catheter end and the vessel, four classicbounding box collision detection algorithms is studied, including bounding box along the axisalgorithm, oriented bounding box algorithm, sphere algorithm, and fixed direction hull algorithm, andtheir algorithm performance is analyzed and compared. In order to ensure real-time simulation, themass-spring feedback force calculation model is established. The vessel model is established through3ds MAX software and pretreated through Netfabble and Meshlab software, and its three-dimensionalmodel data file is obtained. The virtual force feedback simulation program is made with C++language on VS08software, including the rigid vessels force feedback simulation program usingAABB bounding box algorithm, and flexible vessels virtual force feedback program using ball-filledapproach. The simulation shows the flexible force feedback has good real-time and verisimilitude.Finally, an experimental prototype of the catheter system is built. The control system isdebugged, and multi-axis motion control of the PMAC motion control card is realized through theoperating of master handle falcon. The bending experiment of a single cable-driven unit is conductedand the results are analyzed. The intervention experiment with open-loop incremental control iscarried out in vascular model to verify well controllability and precision of the catheter system. Theexperimental results show that the system performance basiclly meets the design requirements.