Active Handheld Flexible Fetoscope-Design and Control Based on a Modified Generalized Prandtl-Ishlinski Model

Julie Legrand, Dries Dirckx, Maarten Durt, Mouloud Ourak, Jan Deprest, Sébastien Ourselin, Jun Qian, Tom Vercauteren, Emmanuel B. Vander Poorten

Abstract: Flexible fetoscopes have been introduced in prior literature as a new surgical tool to limit the stresses applied on the fetal membrane during fetoscopic laser surgery and therefore avoid iatrogenic preterm premature rupture of membranes. However, previous flexible fetoscopes are either too large or do not foresee all the tools that are essential to the success of the targeted procedure. This study proposes the design and control of a single-handed active flexible fetoscope. The instrument is equipped with a camera, a light source, and a working channel while remaining compact (350 mm length and 30 mm wide, with a shaft of 3 mm diameter) and lightweight (87g). It is proposed to use a modified generalized PrandtlIshlinski model for hysteresis compensation as control method. The experimental results indicate that this method allows the instrument to reach a positioning accuracy of up to 4.5%. This suggests that a modified generalized Prandtl-Ishlinski model can therefore be used to compensate for an entire system (e.g. a fetoscope) affected by hysteresis and friction.