The Design and Validation of an Admittance-Controlled Dual-Phase Force-Amplifying Laparoscopic Grasper

Abstract

This study aimed to design and validate a novel laparoscopic grasper as part of the Adlap project, which seeks to develop a versatile modular laparoscopy robot platform with reusable instruments. The main goal was to create an end effector grasper that amplifies pinching force in two stages: a low transmission Phase 1 and a high transmission Phase 2. This approach reduces the force required on the tension rod, thereby minimizing wear on the internal mechanism of the SATA LRS articulation mechanism. Additionally, the study aimed to incorporate a mechanical force-adaptive phase controller, eliminating the need for separate instruments by combining the functions of a low-force tissue grasper and a high-force needle holder. Two prototypes were developed at a 3:1 scale: the Rigid Concept and the Compliant Concept, each utilizing different mechanisms based on the force amplification properties of a wedge. The Rigid Concept featured a 3D-printed housing with all-metal internal components, achieving a Phase 1 transmission value of 0.33 and a Phase 2 transmission value of 0.45, resulting in a force amplification ratio of 1.34. Efficiency during Phase 1 was measured at 66%, while the phase-switching efficiency was 57%. These results suggest that the design successfully met its goals, with potential for further optimization with only minor adjustments. Integrating this compact mechanism offers significant advantages for both robotic operation and manual surgery. While the Compliant Concept showed no force amplification during testing, it theoretically offers a simpler manufacturing process and holds promise for future improvements. The study indicates that the Rigid Concept has significant potential to advance laparoscopic surgery, enhancing instrument reliability, surgical efficiency, and patient outcomes.