Research On The Distal Orientation Of Active Catheter In Minimally Invasive Endovascular Surgery

Recently minimally invasive vascular surgery (MIVS) has become an indispensable therapy to cardiac diseases, which possesses advantages of less scarring, less bleeding and shorter hospital stay. Because the shape of catheter's distal tip is unchangeable in traditional MIVS, however, surgeons must have plenty of clinical experiences and be proficient at catheterization. Every misoperation of the surgery could do great harm to the vessels of patients. What's worse, during MIS process the surgeons have been seriously suffering from X rays. To overcome such shortcomings, two types of catheters were studied in this paper, which aims at improving the catheter's maneuverability, reducing the difficulties of MIVS, as well as protecting the surgeons from X rays through a master/slave catheterization. Details of research are as follows:The shape memory alloy (SMA) spring actuated active catheter was studied. Based on the Brinson one-dimensional constitutive equation, the constitutive equation of SMA springs was builted and revised the equation according to the phase transition condition. Then, considering the characteristics of phase transition, we built the mechanical and thermal equations of SMA active catheter. Furthermore, combining these equations, the model of the SMA catheter was set up and simulated using Simulink. We did the experiment of SMA catheter, and the result well matched up with that of simulation, which validated the effectiveness of the SMA model.Both the ordinary PID controller and the PID controller based on ANFIS were used to control the angle of catheter tip, and their performance were simulated.a novel pull-wire catheter with position sensors was designed and devised. Then according to the mechanical construction of catheter handle, we designed two kinds of control device, differential gear operating mechanism and sliding feed table operating mechanism, to replace the surgeons to steer the catheter.Using the 3DOF master manipulator and motion control card, we built the hardware platform of catheter control. After the study on control strategy, two kinds of methods were proposed: speed follow control and step-by-step local adjustment control. In VC++ environment we built a master/slave control system for catheter operating mechanism and used the master manipulator to control the orientation of catheter.