Force sensing for surgical instruments

1. A surgical instrument, comprising:

a housing portion configured to interface with a manipulator arm of a robotic surgical system;

a shaft including: a proximal end coupled to the housing portion, a distal end, a distal end portion extending proximally from the distal end, a lengthwise axis defined from the proximal end to the distal end, and an anti-friction outer surface;

a plurality of strain gauges mounted on the distal end portion of the shaft adjacent to the distal end of the shaft;

a wrist joint operably coupled to the distal end of the shaft; and

an end effector operably coupled to the wrist joint.

2. The instrument of claim 1 , wherein the anti-friction outer surface comprises a polyamide, an acetal, polytetrafluoroethylene, or Parylene.

3. The instrument of claim 1 ,

wherein the shaft includes a plurality of grooves along the lengthwise axis of the shaft,

wherein the plurality of strain gauges are mounted in the plurality of grooves,

wherein the shaft includes a cover over the grooves, and

wherein the cover provides the anti-friction outer surface.

4. The instrument of claim 3 , wherein the cover comprises fluorinated ethylene propylene or polytetrafluoroethylene.

5. The instrument of claim 1 , wherein the plurality of strain gauges includes eight strain gauges in two groups of four, with each of the strain gauges in a group being spaced apart by 90 degrees around the shaft.

6. The instrument of claim 1 , wherein the plurality of strain gauges includes six strain gauges in two groups of three, with each of the strain gauges in a group being spaced apart by 120 degrees around the shaft.

7. The instrument of claim 1 , wherein the plurality of strain gauges includes four strain gauges spaced apart by 90 degrees around the shaft.

8. The instrument of claim 1 , wherein the plurality of strain gauges includes three strain gauges spaced apart by 120 degrees around the shaft.

9. The instrument of claim 1 , wherein the plurality of strain gauges includes strain gauges spaced apart by 70 degrees and 110 degrees.

10. The instrument of claim 1 , wherein the plurality of strain gauges is selected from a group consisting of fiber optic, foil resistive, surface acoustic wave, and semiconductor type strain gauges.

11. The instrument of claim 1 , wherein at least one strain gauge of the plurality of stain gauges is selected from a group consisting of a Fabry-Perot strain gauge and a fiber Bragg grating strain gauge.

12. The instrument of claim 1 , wherein the plurality of strain gauges includes at least two fiber Bragg strain gauges along one fiber.

13. The instrument of claim 1 , wherein the end effector of the surgical instrument is selected from a group consisting of jaws, scissors, graspers, needle holders, micro-dissectors, staple appliers, tackers, suction irrigation tools, clip appliers, cutting blades, cautery probes, irrigators, catheters, and suction orifices.

14. The instrument of claim 1 , wherein the housing portion interfaces with a sterile adaptor of a sterile drape, and wherein the sterile drape is configured to cover the manipulator arm.

15. The instrument of claim 1 , further comprising a force sensor proximate the housing portion, wherein the force sensor senses an axial force along the lengthwise axis of the shaft.

16. A robotic surgical system, comprising:

a manipulator assembly including a manipulator arm;

a surgical instrument operably coupled to the manipulator arm, the surgical instrument including:

a housing portion configured to interface with the manipulator arm of the robotic surgical system;

a shaft including: a proximal end coupled to the housing portion, a distal end, a distal end portion extending proximally from the distal end, a lengthwise axis defined from the proximal end to the distal end, and an anti-friction outer surface;

a plurality of strain gauges mounted on the distal end portion of the shaft adjacent to the distal end of the shaft;

a wrist joint operably coupled to the distal end of the shaft; and

an instrument tip operably coupled to the wrist joint; and

a force sensor mounted on the manipulator assembly, wherein the force sensor is configured to sense an axial force along the lengthwise axis of the shaft.

17. The system of claim 16 , further comprising a cannula, including:

a proximal portion having a distal end, and an opening configured to receive an instrument shaft,

wherein the proximal portion is configured to operably couple to a manipulator arm;

a tubular member extending from the distal end of the proximal portion,

wherein the tubular member comprises an inner surface and an opening configured to receive the instrument shaft, and

wherein the tubular member is positionable within body tissue, and

an annular rib extending radially inward from the inner surface of the tubular member.

18. The system of claim 17 , wherein the annular rib includes an interior anti-friction surface.

19. The system of claim 18 , wherein the seal includes a lip portion that provides a friction force which is not direction dependent.

20. The system of claim 17 , further comprising an annular seal within the proximal portion of the cannula, the seal having an anti-friction surface.

21. A method comprising:

positioning a force sensor distal to an annular rib,

wherein the force sensor is located on a distal end portion of a shaft of a robotic surgical instrument, and

wherein the annular rib extends radially inward from an inner surface of a tubular member of a cannula; and

sensing a force on the robotic surgical instrument using the force sensor.