Master-slave control of an active catheter instrumented with shape memory alloy actuators

In the recent years, there has been considerable interest in developing active catheters instrumented with shape memory alloy (SMA) actuators to perform angioplasty. The problem, however, with SMA actuators is the extremely non-linear response of the strain with input current. Therefore, control of such an active catheter inside the body is inaccurate and which could lead to unforeseen damage. In this paper, a novel model for SMAs and a robust H_infin loop-shaping controller has been implemented to guarantee robust performance of the active catheter. A closed-loop control algorithm has been implemented to precisely orient the catheter in space based on feedback from a 5-DOF magnetic sensor. The active catheter tracks a reference trajectory generated either by a haptic device under the control of a user or from an image processing algorithm which determines the angle of a branch in the vasculature.