Page 191 - Flexible Robotics in Medicine

178 Chapter 7

diameter cylindrical area for the surgical instrument actuation mechanism, as shown in
Fig. 7.6A. However, this method had its drawbacks. Since the tubes were anchored to three
rings of the spring (Fig. 7.6B), the flexibility of the compression was reduced at the
anchoring points. Furthermore, since the contact surface between the spring and the sheets
is small, the contact tends to break over time due to the compression force exerted on the
contact points.

7.3.2.5 Aluminum sheet guides
The fifth method that was prototyped and tested was using guides made from aluminum
sheet metal. A guide of 3 mm diameter with a center hole of 0.3 mm diameter and three
tendon guide holes of 0.2 mm diameter spaced 120 degrees apart from each other on its
2
circumference was fabricated from a piece of 1 mm sheet metal, as shown in Fig. 7.7A.As
shown in Fig. 7.7B, this sheet metal guide was sandwiched between two springs to provide
a guide hole for the tendons to avoid tendon entanglement and to ensure that the

Figure 7.6
(A) Hollow tube guides; (B) regions of flexibility and rigidity as a result of guides.

Figure 7.7
(A) Sheet metal guide; (B) sandwich of sheet metal guide between two springs.