Trigonometric Ratio-Based Remote Center of Motion Mechanism for Bone Drilling

The remote center of motion (RCM) mechanism is a prominent candidate to aid bone drilling. The surgeon can simply place a drill with the RCM mechanism near the entry point to provide drill alignment with the target. Using this assistive mechanism for bone drilling improves drilling accuracy and reduces the complexity of bone drilling robotic systems. However, because most RCM mechanisms have been developed for laparoscopic surgery or needle insertion into soft tissue, they lack rigidity and are unsuitable for bone drilling. One of the most difficult and important surgical procedures in bone drilling is maintaining as well as guiding the orientation of the drill with respect to the target. This paper proposes an improved RCM mechanism in which a pair of linear actuators and a gearless arc-guide are employed to achieve high rigidity and resolution, which enable bone drilling. A vision-guided navigation system is also integrated into the proposed system to automatically guide the orientation. To verify that the proposed RCM mechanism has sufficient rigidity and targeting accuracy, a series of experiments was performed. The results obtained confirm that the proposed mechanism can maintain its tilting angle under up to 50 N, with a targeting error of approximately 0.28mm.