Passive preload and capstan drive for surgical instruments
A system comprises a medical instrument including a rotatable capstan. The rotatable capstan includes a first coupling feature and a drive system including a rotatable drive element. The rotatable drive element includes a second coupling feature. The first and second coupling features have an aligned engagement configuration in which rotation of the rotatable drive element induces rotation of the rotatable capstan and a non-aligned engagement configuration in which rotation of the rotatable drive element does not induce rotation of the rotatable capstan.
1 . A robotically controlled medical system, comprising:
a plurality of drive motors, each drive motor having a drive shaft with a drive shaft coupling member; and
a medical instrument, comprising:
a flexible tubular shaft comprising a proximal end and a distal end;
a backend mechanism coupled to the proximal end of the flexible tubular shaft, the backend mechanism comprising a plurality of capstans, each capstan including a bore sized for concentric engagement with a drive shaft coupling member of a respective drive motor of the plurality of drive motors such that rotation of the drive shaft of the respective drive motor causes rotation of the capstan about a drive axis concentric with the bore; and
a plurality of tendons including a first tendon and a second tendon, wherein the first tendon is coupled to a first capstan of the plurality of capstans and the second tendon is coupled to a second capstan of the plurality of capstans, wherein the first tendon and the second tendon are coupled to a member disposed at the distal end of the flexible tubular shaft and are configured to move the member in opposing directions.
2 . The robotically controlled medical system of claim 1 , wherein the drive shaft coupling member of each drive motor is configured to fit tightly within the bore of a respective one of the plurality of capstans.
3 . The robotically controlled medical system of claim 2 , wherein each capstan of the plurality of capstans is elastic and the bore is configured to reduce in radius when constricted by a respective tendon.
4 . The robotically controlled medical system of claim 1 , wherein the drive shaft coupling member of each drive motor is configured to form a friction connection with the bore of a respective one of the plurality of capstans.
5 . The robotically controlled medical system of claim 1 , wherein the drive shaft coupling member comprises a pinion.
6 . The robotically controlled medical system of claim 1 , wherein the first capstan is configured to rotate when driven by a first respective drive motor to bend the flexible tubular shaft in a first direction, and the second capstan is configured to rotate when driven by a second respective drive motor to bend the flexible tubular shaft in a second direction.
7 . The robotically controlled medical system of claim 6 , wherein the first capstan is configured to rotate freely while the second capstan is driven by the second respective drive motor, and the second capstan is configured to rotate freely while the first capstan is driven by the first respective drive motor.
8 . The robotically controlled medical system of claim 1 , wherein the plurality of tendons further includes a third tendon and a fourth tendon, wherein the plurality of capstans further includes a third capstan and a fourth capstan, wherein the third tendon is configured to wrap around the third capstan and the fourth tendon is configured to wrap around the fourth capstan, and wherein the third tendon and the fourth tendon are coupled to the member and are configured to move the member in second opposing directions.
9 . The robotically controlled medical system of claim 1 , wherein each of the first and second tendons is secured to the backend mechanism proximally of the first and second capstans.
10 . The robotically controlled medical system of claim 1 , wherein the member comprises an end effector.
11 . The robotically controlled medical system of claim 1 , wherein the member comprises a link of a joint mechanism of the flexible tubular shaft.
12 . The robotically controlled medical system of claim 1 , wherein an axis of rotation of each of the first and second capstans is oriented parallel to a longitudinal axis of the flexible tubular shaft.
13 . The robotically controlled medical system of claim 1 , wherein an axis of rotation of each of the first and second capstans is oriented perpendicular to a longitudinal axis of the flexible tubular shaft.
14 . The robotically controlled medical system of claim 1 , further comprising a shape sensor extending along a length of the flexible tubular shaft and a length of the member.
15 . The robotically controlled medical system of claim 1 , further comprising a manipulator comprising a base member and the plurality of drive motors, and wherein the drive shafts of the plurality of drive motors are arranged in a plurality of rows extending from the base member.
16 . The robotically controlled medical system of claim 1 , further comprising a passive preload mechanism providing a tension in the first and second tendons when the first and second capstans are disengaged from respective drive motors.
17 . The robotically controlled medical system of claim 1 , further comprising a passive preload system providing a tension in the first and second tendons, wherein the passive preload system comprises a plurality of springs.
18 . The robotically controlled medical system of claim 1 , wherein each tendon of the plurality of tendons extends through a respective sheath inside the flexible tubular shaft.
19 . The robotically controlled medical system of claim 1 , further comprising a sterile barrier, wherein the backend mechanism engages the plurality of drive motors through the sterile barrier.
20 . The robotically controlled medical system of claim 1 , wherein each of the first and second tendons comprises a stranded cable secured to a tube.