Preliminary Estimation of the Friction between Force-sensing Forceps and Cornea

摘要

Continuous curvilinear capsulorhexis (CCC) is a delicate ophthalmic procedure that may benefit from robot technology. In CCC, surgeons make an incision in the cornea, insert forceps into the anterior segment through the incision, and peel the anterior lens capsule (ALC) from the lens. The absence of perception of axial peeling force applied to ALC is challenging in developing robot-assisted CCC. A potential way to deal with this challenge is measuring axial force with a mercantile force sensor, which has the advantage of sub-millinewton precision, high axial stiffness, high stability, and ease of use. However, the measured results of the mercantile force sensor contain the axial peeling force and forceps-cornea friction. Therefore, we seek to estimate the friction at the incision with the distributed LuGre friction model. The normal force and friction at incision are measured by fiber bragg grating (FBG) sensors and a mercantile force sensor, respectively. Then, the parameters of the LuGre model are identified by applying a low-frequency sinusoidal movement on the forceps. An identification experiment is performed on ex-vivo pig cornea samples. Finally, friction during inserting forceps into the anterior segment of ex-vivo pig eyes is estimated. The root mean square error of friction identification and estimation are 0.59 mN and 1.59 mN, respectively.