Multi-Axis Force Sensing in Laparoscopic Surgery

This letter presents a novel approach to multi-axis force-sensing in laparoscopic surgery. It requires no modification to the surgical instrument and is therefore adaptable to different surgical tools. The sensing approach relies on a novel cannula design and utilizes a very high-resolution transducer for deflection measurement at the proximal shaft of the surgical instrument. The proposed cannula has an inner tube and an outer tube; the inner tube is attached to the cannula's interface to the robot frame through a compliant leaf spring with adjustable stiffness. It allows bending of the instrument shaft due to the tip forces. The outer tube mechanically filters out the body forces so they do not affect the instrument's bending behavior. An optical transducer with integrated electronics was mounted onto the proximal shaft of a da Vinci EndoWrist. A mathematical model of the sensing system was developed. A setup was built for calibration and testing, and its hardware and software are discussed in detail. Model-based and data-driven calibration approaches were compared. Comprehensive testing was conducted to validate that the sensor can successfully measure the lateral forces and moments and the axial torque applied to the instrument's distal end within the desired resolution, accuracy, and range requirements.