Development of Novel Bevel-Geared 5 mm Articulating Wrist for Micro-Laparoscopy Instrument

A laparoscopic surgery can be made less invasive by utilizing slimmer tools. However, at the size scale of the microlaparoscopic instruments, it has been very challenging to incorporate a wrist mechanism for dexterousmanipulation at the surgical sites. In this letter, we present a 5-mm wristed instrument for microlaparoscopy. Unlike other instruments with wrists utilizing the bending of compliant parts or tendon and pulleys, the instrument has a wrist mechanism using oblique bevel gears driven by two concentric shafts. As a result, the wrist can generate a 2-degrees-of-freedom sharp articulating motion with 1) pitch angle range of +/- 90 degrees and 2) a full rotation along roll direction. Also, the wrist is scalable and easier to assemble compared to the ones using tendon and pulleys. The accuracy and the load carrying capacity of the wrist were evaluated. The wrist was able to orient tools to the commanded direction with an average error of 1.31 degrees and manipulate up to 250 g of the load. The feasibility of the instrument was verified through pick and place experiment and peg transfer test using a teleoperated surgical robot equipped with the instrument. Using the single robot arm with the proposed wrist, it took 98.7 s on average to transfer five objects consecutively to the opposite side of the pegboard. Thus, the articulating wrist widens dexterity in tight anatomic space with the oblique gear mechanism. It is applicable to needlescopic instruments or steerable laparoscope system.