Operating self-antagonistic drives of medical instruments
A medical instrument including a shaft and an actuated structure mounted at a distal end of the shaft can employ a pair of tendons connected to the actuated structure, extending down the shaft, and respectively wound around a capstan in opposite directions. A passive preload system may maintain minimum tensions in the tendons.
1. A medical instrument comprising:
an instrument shaft;
an actuated structure at a distal end of the instrument shaft;
a backend mechanism at a proximal end of the instrument shaft, comprising:
a backend shaft rotatable in a first direction and a second direction that is opposite of the first direction;
a first one-way clutch coupled to the backend shaft, the first one-way clutch configured to slip when the backend shaft is rotated in the second direction;
a second one-way clutch coupled to the backend shaft, the second one-way clutch configured to slip when the backend shaft is rotated in the first direction;
a first length of tendon connected to the actuated structure and extending down the instrument shaft, the first length of tendon wound around the first one-way clutch in the first direction; and
a second length of tendon connected to the actuated structure and extending down the instrument shaft, the second length of tendon wound around the second one-way clutch in the second direction; and
a drive element operably coupled to the backend shaft and configured to drive the first length of tendon by rotating the backend shaft in the first direction and drive the second length of tendon by rotating the backend shaft in the second direction to drive the actuated structure.
2. The medical instrument of claim 1 , wherein the drive element comprises a motor.
3. The medical instrument of claim 1 , wherein the drive element comprises a hand-operated manipulator.
4. The medical instrument of claim 3 , wherein the hand-operated manipulator includes a knob or a lever.
5. The medical instrument of claim 1 , further comprising a preload system configured to eliminate slack or tension build-up in at least one of the first and second lengths of tendon.
6. The medical instrument of claim 5 , wherein the first length of tendon comprises a first tendon, the second length of tendon comprises a second tendon, and the preload system comprises first and second spring-loaded mountings, a proximal end of the first tendon connected to the first spring-loaded mounting and a proximal end of the second tendon connected to the second spring-loaded mounting.
7. The medical instrument of claim 5 , wherein the backend shaft includes a slide mounting that permits linear movement of the backend shaft, and the preload system is coupled to the backend shaft.
8. The medical instrument of claim 7 , wherein the preload system comprises a spring-loaded mounting coupled to the backend shaft.
9. The medical instrument of claim 5 , wherein the drive element includes a slide mounting that permits linear movement of the drive element, and the preload system is coupled to the drive element.
10. The medical instrument of claim 9 , wherein the preload system comprises a spring-loaded mounting coupled to the drive element.
11. The medical instrument of claim 5 , wherein the preload system comprises a pulley within the backend mechanism, the first and second lengths of tendon being connected to the pulley and the pulley being movable to adjust a tension in at least one of the first length of tendon or the second length of tendon.
12. The medical instrument of claim 11 , wherein the pulley comprises a slide mounting that permits linear movement of the pulley to adjust the tension; and the preload system further comprises a spring-loaded mounting attached to the pulley.
13. The medical instrument of claim 11 , wherein the first length of tendon and the second length of tendon are connected together to form a single continuous tendon looped around the pulley.
14. The medical instrument of claim 5 , wherein the first length of tendon and the second length of tendon are connected together to form a single continuous tendon, and the preload system comprises:
a pulley fixed within the backend mechanism, the single continuous tendon looped around the pulley; and
a spring, ends of the single continuous tendon connected to ends of the spring such that the spring is in-line with the single continuous tendon.
15. The medical instrument of claim 1 , wherein the actuated structure comprises an end effector.
16. The medical instrument of claim 1 , wherein the actuated structure comprises a joint; and the drive element is configured to drive the first length of tendon by rotating the backend shaft in the first direction and drive the second length of tendon by rotating the backend shaft in the second direction to drive the joint of the actuated structure.
17. The medical instrument of claim 16 , wherein the joint is a first joint of the actuated structure, the first length of tendon and the second length of tendon correspond to a first pair of tendons, and the medical instrument further comprises a second pair of tendons connected to a second joint of the actuated structure.
18. The medical instrument of claim 17 , wherein the first pair of tendons comprises a first preload system, and the second pair of tendons comprises a second preload system.
19. The medical instrument of claim 1 , wherein the instrument shaft comprises a flexible shaft.
20. The medical instrument of claim 1 , wherein the instrument shaft comprises a rigid shaft.