Crossed-cylinder wrist mechanism with two degrees of freedom
According to an aspect, a device may include a first member, a second member, and a wrist mechanism disposed between the first member and the second member. The wrist mechanism may include a first cylinder portion coupled to the first member, and a second cylinder portion coupled to the second member. The first cylinder portion may be rollably engaged with the second cylinder portion such that movement of the first cylinder portion with respect to the second cylinder portion is configured to cause the first member to move in at least two directions with respect to the second member. The second cylinder portion may be positioned with respect to the first cylinder portion such that a longitudinal axis of the second cylinder portion is orthogonal to a longitudinal axis of the first cylinder portion.
1. A medical device comprising:
a first member;
a second member;
a first cylinder portion coupled to the first member;
a second cylinder portion coupled to the second member; and
a plurality of cables coupled to the first cylinder portion and providing force to ensure the first cylinder portion stays rollably engaged with the second cylinder portion, the plurality of cables configured to actuate movements in two or more degrees of freedom such that the first member moves in two or more directions with respect to the second member;
the second cylinder portion being positioned such that a longitudinal axis of the second cylinder portion is orthogonal to a longitudinal axis of the first cylinder portion;
a first degree of freedom of the two or more degrees of freedom comprising a rolling translation of the first cylinder portion along a surface of the second cylinder portion parallel to the longitudinal axis of the second cylinder portion; and
a second degree of freedom of the two or more degrees of freedom comprising a rolling translation of the first cylinder portion on the surface of the second cylinder portion around the longitudinal axis of the second cylinder portion;
wherein a first pulling force on each cable of a first pair of the cables actuates a first movement consisting of the rolling translation of the first cylinder portion along the surface of the second cylinder portion parallel to the longitudinal axis of the second cylinder portion; and
wherein a second pulling force on each cable of a second pair of the cables actuates a second movement consisting of the rolling translation of the first cylinder portion on the surface of the second cylinder portion around the longitudinal axis of the second cylinder portion.
2. The medical device of claim 1 , wherein each of the first cylinder portion and the second cylinder portion defines a rounded surface portion having a cross section shaped as a segment of a cylinder.
3. The medical device of claim 1 , wherein each of the first cylinder portion and the second cylinder portion defines a rounded surface portion, the rounded surface portion defining a plurality of gear teeth.
4. The medical device of claim 3 , wherein each gear tooth of the plurality of gear teeth comprises a first gear profile and a second gear profile, the second gear profile being different than the first gear profile.
5. The medical device of claim 4 , wherein the first gear profile is an involute profile, and the second gear profile is a rack profile.
6. The medical device of claim 3 , wherein the plurality of gear teeth are arranged into a plurality of rows of gear teeth comprising a first row of gear teeth and a second row of gear teeth, the second row of gear teeth being offset from the first row of gear teeth.
7. The medical device of claim 6 , wherein the plurality of rows of gear teeth comprises a third row of gear teeth aligned with the first row of gear teeth.
8. The medical device of claim 1 , wherein the plurality of cables ensure the first cylinder portion stays rollably engaged with the second cylinder portion while actuating the movements in the two or more directions.
9. The medical device of claim 8 , wherein the pulling forces on the plurality of cables provides the force to ensure the first cylinder portion stays rollably engaged with the second cylinder portion.
10. The medical device of claim 8 , wherein the plurality of cables are coupled to a platform of the first cylinder portion.
11. The medical device of claim 1 , wherein the first member comprises a surgical end effector of a surgical instrument, and the second member comprises a shaft of the surgical instrument.
12. The medical device of claim 1 , wherein the first degree of freedom comprises the first cylinder portion moving in a direction parallel to the longitudinal axis of the second cylinder portion, and the second degree of freedom comprises the first cylinder portion moving in a direction around the longitudinal axis of the second cylinder portion such that the longitudinal axis of the first cylinder portion moves around the longitudinal axis of the second cylinder portion within a plane that is orthogonal to the longitudinal axis of the second cylinder portion.
13. The medical device of claim 1 , wherein the two or more directions comprise a first direction and a second direction orthogonal to the first direction.
14. The medical device of claim 1 , wherein each of the first cylinder portion and the second cylinder portion comprises a plurality of stacked carbon nanotube composite sheets or a plurality of stacked stainless steel sheets.
15. The medical device of claim 1 , wherein a distance between the longitudinal axis of the first cylinder portion and the longitudinal axis of the second cylinder portion is within a range of 1-5 millimeters.
16. The medical device of claim 1 , wherein the first cylinder portion and the second cylinder portion are comprised in a wrist mechanism, and wherein the wrist mechanism has a diameter within a range of 1-5 millimeters.
17. A wrist mechanism comprising:
a first cylinder portion;
a second cylinder portion; and
a plurality of cables coupled to the first cylinder portion;
wherein each of the first cylinder portion and the second cylinder portion defines a rounded surface portion, the rounded surface portion defining a plurality of rows of gear teeth, the plurality of rows of gear teeth comprising a first row of gear teeth and a second row of gear teeth adjacent to the first row, the gear teeth of the second row being offset from the gear teeth of the first row;
wherein the plurality of cables provide force to ensure that the first cylinder portion is rollably engaged with the second cylinder portion such that the gear teeth of the first cylinder portion are engaged with the gear teeth of the second cylinder portion;
wherein the second cylinder portion is positioned such that a longitudinal axis of the second cylinder portion is orthogonal to a longitudinal axis of the first cylinder portion; and
wherein the plurality of cables are configured to actuate movements of the first cylinder portion with respect to the second cylinder portion by: (i) rollably translating the first cylinder portion along a surface of the second cylinder portion parallel to the longitudinal axis of the second cylinder portion, and (ii) rollably translating the first cylinder portion on the surface of the second cylinder portion around the longitudinal axis of the second cylinder portion;
wherein a first pulling force on each cable of a first pair of the cables actuates a first movement consisting of the rolling translation of the first cylinder portion along the surface of the second cylinder portion parallel to the longitudinal axis of the second cylinder portion; and
wherein a second pulling force on each cable of a second pair of the cables actuates a second movement consisting of the rolling translation of the first cylinder portion on the surface of the second cylinder portion around the longitudinal axis of the second cylinder portion.
18. The wrist mechanism of claim 17 , wherein, as the first cylinder portion rolls in a direction on the surface of the second cylinder portion around the longitudinal axis of the second cylinder portion, the longitudinal axis of the first cylinder portion moves around the longitudinal axis of the second cylinder portion within a plane that is orthogonal to the longitudinal axis of the second cylinder portion.
19. The medical device of claim 17 , wherein each gear tooth of the plurality of rows of gear teeth comprises a first gear profile and a second gear profile, the second gear profile being different than the first gear profile.