Follow-The-Leader Control

Abstract

Surgical procedures are shifting towards Minimal Invasive Surgery (MIS). Surgeons are currently limited in their actions by the straight rigid instruments available to them. Devices capable of navigating along curved trajectories increase a surgeon's workspace, which can benefit surgical performance. This paper shortly goes over the state of the art of Highly Redundant Devices (HRD) capable of Follow-The-Leader (FTL) behaviour. In literature virtual and physical control methods are used. Virtual control relies on computer control in combination with actuators. The actuators control the tip segments via cables running the length of the device. Physical control stores and transfers shape information in a mechanical configuration. From the state of the art it was found that physical control has the potential of reducing the amount of actuators severly. However, it was also found that these mechanisms are, up to now, placed inside the tip. The integration of the physical control inside the tip leads to problems with stiffness, accumulating errors and minimisation. A combination of attributes from both virtual and physical control resulted in a novel mechanical FTL control principle: MemoSlide. This principle essentially captures a software algorithm in a mechanism. The suggested control principle reduces the number of actuators needed for FTL control. A Proof of Concept (PoC) demonstrator model, showcasing the MemoSlide principle in a plane, is designed and fabricated. Friction, Jamming and Locking were identified as crucial aspects to consider while implementing the MemoSlide principle. Experience gained during fabrication and evaluation resulted in a set of design guidelines and a simplification of the MemoSlide principle. Application of the simplified principle and the design guidelines resulted in a conceptual design of a control module. The control module is intended to control a steerable surgical tool tip as inspiration for future applications of the MemoSlide principle.