The present invention is directed to a tool having a
wrist mechanism that provides
pitch and
yaw rotation in such a way that the tool has no singularity in roll,
pitch, and
yaw. A positively positionable multi-disk
wrist mechanism includes a plurality of disks or vertebrae stacked in series. Each
vertebra is configured to rotate in
pitch or in
yaw with respect to each neighboring
vertebra. Actuation cables are used to manipulate and control movement of the vertebrae. In specific embodiments, some of the cables are distal cables that extend from a proximal
vertebra through one or more intermediate vertebrae to a distal vertebra, while the remaining cables are medial cables that extend from the proximal vertebra to one or more of the intermediate vertebrae. The cables are actuated by a pivoted plate cable
actuator mechanism. In specific embodiments, the
actuator mechanism includes a plurality of small
radius holes or grooves for receiving the medial cables and a plurality of large
radius holes or grooves for receiving the distal cables. The holes or grooves restrain the medial cables to a small
radius of motion and the distal cables to a large radius of motion, so that the medial cables to the medial vertebra move only a fraction of the amount as the distal cables to the distal vertebra, so as to achieve precise control and manipulation of the vertebrae.