Modeling the dynamic behavior of a shape memory alloy actuated catheter

In this paper we investigate the transient behavior of a simple active catheter: a central tube actuated by a single nitinol tendon enclosed by an outer sleeve. Dynamic models are developed to characterize the transient behavior and optimize the design of an experimental prototype. The bending mechanics are derived using a circular arc model and are experimentally validated. Nitinol actuation is described using the Seelecke-Muller-Achenbach model for single-crystal shape memory alloys using experimentally determined parameters. The dynamic characteristics of this active catheter system are simulated and compared with experimental results. Joule heating is used to generate tip deflections, which are computed in real time using a dual-camera imaging system. The effects of outer sleeve thickness on heat transfer and transient response characteristics are studied.