A special mechanism
The unique feature of a pulley steering mechanism compared to other mechanisms, is the tight bend. Additionally, in this system, the hinge of the end-effector contribute to the articulation of the tip. The jaw parts are actuated by two cable-loops.
A two-faced challenge
The first challenge in designing such a system is that each cable-loop is related to both a pitch and yaw movement. In a robotic system this is compensated by software. In a purely mechanical system, the mechanism itself has to compensate, in order to design a usable instrument.
The second challenge is that because large forces are required, steel cables are used having a minimal thickness. If the pulleys are too small steel cables will start to fray after a few movements. For this reason, the instruments in robotic systems have a diameter of 8 mm1, which is larger than the common diameters of laparoscopic instruments (5mm).
Dr. Ir. Jules Scheltes, CTO DEAM:
“It was a challenging mechanism. And seeing it realised in a series of prototypes gave joy to my engineering heart.”
Being a company focusing on steerable devices for minimally invasive procedures, our designers investigate multiple options for steering instruments. This project had its main goal increase DEAM’s know-how on steering mechanism. A 5 mm pulley jaw mechanism actuated by a purely mechanical handheld mechanism was designed, prototyped and tested. Figure 1 shows the prototype orienting during a suturing exercise. Figure 2 presents an impression of how the rugged steerable technology could be applied.
 Da Vinci X/Xi Instrument & Accessory Catalog, November 2020
June 2, 2020