Parameter Estimation and Tracking of an Expandable Cable-Driven Parallel Mechanism for Minimally Invasive Interventions

Conventional catheter-based procedures suffer from inaccurate device steering, and navigation limitations as the long and flexible devices are manipulated remotely from outside the patient body. A recently developed approach aims to overcome these limitations by using an expandable cable-driven parallel mechanism for local device manipulation and tracking relative to the anatomy. However, as the frame of this system is flexible and may be constrained by unknown anatomical constraints inside the patient body, accurate system identification is a key and critical step which would ultimately determine the accuracy in device steering and tracking. In this paper, we present an optimization approach to identify the parameters of an expandable cable-driven parallel mechanism deployed in an unknown environment, merely based on measurements of the cable length variations that would be available outside the patient body. We have verified and validated the proposed approach in terms of accuracy in the prediction of the frame shape and cable anchor locations, as well as its tracking accuracy. Both simulations and experimental studies have been performed, and we have demonstrated that the proposed method allows for rapid frame shape and anchor position estimation with unknown anatomical constraints and permits localized device tracking and steering with submillimeter accuracy.