Study on active catheter for minimally invasive surgery based on large deflection theory

A kind of active catheter used for minimally invasive surgery and actuated by shape memory alloy (SMA) was developed in this paper. The outer diameter of the catheter is 1.25 mm. The catheter was designed to consist of several bending units for achieving a large bending angle, but at the same time not increasing the outer diameter too much. It was considered that the deflection curve of axis of the catheter is determined by the output force of the SMA actuators. Based on large deflection theory, the deflection curve equation of the axis of the catheter was set up using precise form of the curvature. Through integral transform, the length and output force of each SMA actuator under the anticipative attitude of the tip of the active catheter were obtained, and the accurate coordinate of the center of the joint was givein. This study has provided great convenience to get control of the catheter, and has improved, to a certain extent, the design philosophy of problems such as active catheter.