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Ch13-I044963.fm Page 59 Tuesday, August 1, 2006 12:49 PM
Tuesday, August 1,2006
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Forceps manipulator
Forceps manipulator had four DOFs equivalent to the conventional laparoscopic surgery (Figure 1). It adopted
Remote Center of Motion (RCM) mechanism so that forceps could rotate around the pivot point (the incision
hole) without any mechanical joint at the center of rotation. In this study, we used "two linear actuator mecha-
nism" as an RCM mechanism using a couple of ball screws and servomotors. When the feeding ratio of two ac-
tuators was constant, the lines running through the tips of both linear actuators crossed at a certain point, and it was
the pivot point (Figure 3)(Kim D., et al. (2002)). In Figure 3(center), "Rotationl" was realized by rotating the
whole manipulator using a servomotor, and "Rotaion2" was realized using "two linear actuator mechanism". The
center of pivot motion was located at the intersection of each rotational axis. The insertion of the forceps along the
shaft was realized by "double-stage mechanism". It consisted of a couple of linear stage. One was mounted on the
other, and it expanded like a ladder truck (Figure 3). This mechanism realized double-long traveling distance of
the linear stage, and the size of manipulator was miniaturized. In this manipulator, the

6 DOFs

Figure 2: (left) microscope arm, (center) six-DOF precise positioning arm, (right) three arms for each manipulator

Fixed Ratio Feeding

Figure 3: (left) RCM mechanism, (center) prototype, (right) double-stage mechanism

460[mml 160[mm] I Bending2 -
Iwl

Figure 4: (left) prototype, (center) bending joint and grasper, (right) various kinds of forceps