Optical Force Sensing In Minimally Invasive Robotic Surgery

This paper evaluates the feasibility of a novel optical sensing concept to measure forces applied at the tip of daVinci EndoWrist instruments. An optical slit is clamped onto the instrument shaft, in-line with an infrared LED-bicell pair. Deflection of the shaft moves the slit with respect to the LED-bicell pair and modulates the light incident on each active element of the bicell. The differential photocurrent is conditioned and monitored to estimate the tip forces. The feasibility evaluation consists of a flexible beam model to quantify the required sensor performance, experimental results with a 3D printed prototype and estimation of the sensor limitations including the measurement bandwidth due to the structural dynamics. The proposed approach requires no modifications to the instrument, is adaptable to different instruments and robot platforms, and leads to high-resolution, high-dynamic range sensing without hysteresis.