Research On An Interventional Active Catheter Based On SMA And Cable Hybrid Driven

Minimally invasive interventional surgery serves as an effective solution in clinical surgeries,such as cardiac disease, abdominal organs disease etc, due to its merits of little trauma, fast recoveryand less recurrence. Considering complex and changeable characteristics of the operatingenvironment for the surgical intervention, the paper proposes a SMA (Shape memory alloy) and thecable hybrid-driven modular catheter to improve the versatility of interventional devices.The catheter composes of a skeleton spring in the center and three SMA actuators or driven ropesdistributed on the tube cross-section direction. The bending direction is determined by behaviors oftwo adjacent SMA actuators or driven ropes. According to the operation objects and environment ofindividual differences, multiple bending units are reconstructed to increase the degree of freedom andachieve a large bending angle.The motion characteristics of the active bending unit are analyzed with D-H parameter method,while, Screw and POE (product of exponentials formula) method are used to establish the kinematicsmodel of a three-joint interventional active catheter. Inverse kinematics is analyzed by use of thegenetic algorithm, the results verified the accuracy of the kinematics model.According to the working characteristics of the SMA actuator, the resistance feedback controlsystem of interventional active catheter robot based on ATMEGA16microcontroller is developed.Then, the resistance feedback system modules are designed and debugged by adopting the modularprogramming method. The rope tension equipment and motor drive system are designed inaccordance with the requirements of rope drive. The active catheter transporting system is developedand the push force and speed are analyzed, finally, the safety and reliability of the transporting systemis verified by experiment.Under the hypothesis of constant curvature arc, the output displacement and output force of SMAactuator are deduced in detail under the known bending angle of the interventional active catheter forthe robot design parameters.The control circuit board of SMA and rope drive system are produced and tested, the relationshipbetween the length of SMA actuator and resistance is measured by use of the board. A prototype ofcatheter robot is developed, and the relationship between bending angle and length of actuators isanalyzed. Finally, the results verify the effectiveness and correctness of the kinematics model，andshow the design of both the structure and control system are feasible.