Wrist articulation by linked tension members
Surgical tools having a two degree-of-freedom wrist, wrist articulation by linked tension members, mechanisms for transmitting torque through an angle, and minimally invasive surgical tools incorporating these features are disclosed. An elongate intermediate wrist member is pivotally coupled with a distal end of an instrument shaft so as to rotate about a first axis transverse to the shaft, and an end effector body is pivotally coupled with the intermediate member so as to rotate about a second axis that is transverse to the first axis. Linked tension members interact with attachment features to articulate the wrist. A torque-transmitting mechanism includes a coupling member, coupling pins, a drive shaft, and a driven shaft. The drive shaft is coupled with the driven shaft so as to control the relative orientations of the drive shaft, the coupling member, and the driven shaft.
1. A surgical tool comprising:
an elongate shaft extending along a longitudinal axis and having a proximal end and a distal end, the longitudinal axis extending through the proximal and distal ends;
an end effector movably coupled to the distal end of the elongate shaft to rotate about a first axis and a second axis, the first axis being orthogonal to the longitudinal axis, the second axis being orthogonal to the first axis and transverse to the longitudinal axis, the second axis being offset from the first axis along the longitudinal axis, the end effector including four attachment features, each of the four attachment features including a curved portion, each of the four curved portions having a center-of-curvature and a curved ordinary centerline, each of the four center-of-curvatures being located in a plane containing the second axis, and each of the four curved ordinary centerlines being tangent to a plane containing the first axis;
four tension members extending along the elongate shaft, each of the four tension members being interfaced with a respective one of the four curved portions;
control cables drivingly coupled with the end effector;
an intermediate member pivotally coupled with the elongate shaft to rotate relative to the elongate shaft about the first axis, the intermediate member being pivotally coupled with the end effector so that the end effector rotates relative to the intermediate member about the second axis, the intermediate member having internal passages shaped to constrain cross-sectional positions of the control cables; and
a support member to which the intermediate member is pivotally coupled to rotate about the first axis, the elongate shaft comprising the support member.
2. The surgical tool of claim 1 , wherein each respective curved ordinary centerline passes through cross-sectional centers of the respective curved portion.
3. The surgical tool of claim 1 , wherein each of the four tension members is configured to:
slide along the respective curved portion in conjunction with rotation of the end effector about the second axis; and
rotate around the respective curved ordinary centerline in conjunction with rotation of the end effector about the first axis.
4. The surgical tool of claim 3 , wherein each of the four tension members comprises a lug having an aperture through which the respective curved portion extends.
5. The surgical tool of claim 3 , wherein the four tension members are arranged around the longitudinal axis in a first diagonally opposed pair and a second diagonally opposed pair, each of the four tension members being under tension induced by a force applied to the tension member and transferred to the respective one of the attachment features by the tension member.
6. The surgical tool of claim 5 , wherein:
rotation of the end effector about the first axis occurs in conjunction with proximal displacement of one of each of the first and second diagonally opposed pairs of the tension members that is equal in magnitude to distal displacement of the other of each of the first and second diagonally opposed pairs of the tension members; and
rotation of the end effector about the second axis occurs in conjunction with proximal displacement of one of each of the first and second diagonally opposed pairs of the tension members that is equal in magnitude to distal displacement of the other of each of the first and second diagonally opposed pairs of the tension members.
7. The surgical tool of claim 1 , wherein the first and second axes are separated by 2 mm or less.
8. The surgical tool of claim 1 , wherein:
angular rotation of the intermediate member relative to the elongate shaft about the first axis is limited via contact between the intermediate member and the support member; and
angular rotation of the end effector about the second axis is limited via contact between the end effector and the intermediate member.
9. A surgical instrument for use with a surgical robot of a minimally invasive surgical system, the surgical instrument comprising:
an elongate shaft having a proximal end and a distal end, wherein a longitudinal axis extends through the proximal and distal ends;
an actuation assembly disposed at the proximal end of the elongate shaft, the actuation assembly being configured to be mounted to the surgical robot;
an end effector movably coupled to the distal end of the elongate shaft to rotate about a first axis and a second axis, the first axis being orthogonal to the longitudinal axis, the second axis being orthogonal to the first axis and transverse to the longitudinal axis, the second axis being offset from the first axis along the longitudinal axis, the end effector including four attachment features, each of the four attachment features including a curved portion, each of the four curved portions having a center-of-curvature and a curved ordinary centerline, each of the four center-of-curvatures being located in a plane containing the second axis, and each of the four curved ordinary centerlines being tangent to a plane containing the first axis;
four tension members extending along the elongate shaft between the actuation assembly and the end effector, each of the four tension members being interfaced with a respective one of the four curved portions and configured to:
slide along the respective curved portion in conjunction with rotation of the end effector about the second axis; and
rotate around the respective curved ordinary centerline in conjunction with rotation of the end effector about the first axis;
control cables drivingly coupled with the end effector;
an intermediate member pivotally coupled with the elongate shaft to rotate relative to the elongate shaft about the first axis, the intermediate member being pivotally coupled with the end effector so that the end effector rotates relative to the intermediate member about the second axis, the intermediate member having internal passages shaped to constrain cross-sectional positions of the control cables; and
a support member to which the intermediate member is pivotally coupled to rotate about the first axis, the elongate shaft comprising the support member.
10. The surgical instrument of claim 9 , wherein each respective curved ordinary centerline passes through cross-sectional centers of the respective curved portion.
11. The surgical instrument of claim 9 , wherein each of the four tension members comprises a lug having an aperture through which the respective curved portion extends.
12. The surgical instrument of claim 9 , wherein the four tension members are arranged around the longitudinal axis in a first diagonally opposed pair and a second diagonally opposed pair, each of the four tension members being under tension induced by a force applied to the tension member and transferred to the respective one of the attachment features by the tension member.
13. The surgical instrument of claim 12 , wherein:
rotation of the end effector about the first axis occurs in conjunction with proximal displacement of one of each of the first and second diagonally opposed pairs of the tension members that is equal in magnitude to distal displacement of the other of each of the first and second diagonally opposed pairs of the tension members; and
rotation of the end effector about the second axis occurs in conjunction with proximal displacement of one of each of the first and second diagonally opposed pairs of the tension members that is equal in magnitude to distal displacement of the other of each of the first and second diagonally opposed pairs of the tension members.
14. The surgical instrument of claim 9 , wherein the first and second axes are separated by 2 mm or less.
15. The surgical instrument of claim 9 , wherein:
angular rotation of the intermediate member relative to the elongate shaft about the first axis is limited via contact between the intermediate member and the support member; and
angular rotation of the end effector about the second axis is limited via contact between the end effector and the intermediate member.
16. The surgical instrument of claim 9 , further comprising a first actuation mechanism at least partially disposed within the actuation assembly and a second actuation mechanism at least partially disposed within the actuation assembly, the first actuation mechanism including a first rotatable capstan drivingly coupled with a first diagonally opposed pair of the four tension members, the second actuation mechanism including a second rotatable capstan drivingly coupled with s second diagonally opposed pair of the four tension members, and wherein controlled rotation of each of the first and second capstans is used to angularly reorient the end effector about the first and second axes.