Torque sensing in a surgical robotic wrist

1. A surgical robotic component comprising an articulated terminal portion, the terminal portion comprising:

a distal segment having an attachment for an instrument to be connected thereto, wherein the attachment is fixed relative to the distal segment such that it maintains a fixed relative orientation between the distal segment and the instrument;

an intermediate segment;

a basal segment;

a first articulation between the distal segment and the intermediate segment, the first articulation permitting relative rotation of the distal segment and the intermediate segment about a first axis; and

a second articulation between the intermediate segment and the basal segment, the second articulation permitting relative rotation of the intermediate segment and the basal segment about a second axis,

wherein:

the intermediate segment comprises a third articulation permitting relative rotation of the distal segment and the basal segment about third and fourth axes; and

the first, second and third articulations are arranged such that in at least one configuration of the third articulation:

the first and second axes are collinear;

the third and fourth axes are transverse to the first axis;

the third and fourth axes are transverse to each other;

the third and fourth axes intersect each other; and

the surgical robotic component is configured to determine torque about the third and fourth axes.

2. A surgical robotic component as claimed in claim 1 , the terminal portion being attached to the remainder of the surgical robotic component by the basal segment.

3. A surgical robotic component as claimed in claim 2 , wherein the attachment is only articulable relative to the basal segment by the first, second and third articulations.

4. A surgical robotic component as claimed in claim 2 , wherein the attachment is located on the first axis.

5. A surgical robotic component as claimed in claim 2 , the surgical robotic component being located at the end of a surgical robot arm, and further comprising a surgical instrument attached to the attachment.

6. A surgical robotic component as claimed in claim 5 , wherein the surgical instrument extends in a direction along the first axis.

7. A surgical robotic component as claimed in claim 2 , the surgical robotic component being located at the end of a surgical instrument, and further comprising a surgical end effector attached to the attachment.

8. A surgical robotic component as claimed in claim 7 , wherein the surgical end effector extends in a direction along the first axis.

9. A surgical robotic component as claimed in claim 1 , the intermediate segment comprising a first torque sensor configured to sense torque about the third axis.

10. A surgical robotic component as claimed in claim 1 , the intermediate segment comprising a second torque sensor configured to sense torque about the fourth axis.

11. A surgical robotic component as claimed in claim 1 , the terminal portion further comprising a third torque sensor configured to sense torque about the first axis.

12. A surgical robotic component as claimed in claim 1 , the terminal portion further comprising a fourth torque sensor configured to sense torque about the second axis.

13. A surgical robotic component as claimed in claim 1 , wherein in the said configuration the third and fourth axes are perpendicular to each other.

14. A surgical robotic component as claimed in claim 1 , wherein in the said configuration the third and fourth axes are perpendicular to the first axis.

15. A surgical robotic component as claimed in claim 1 , wherein the first articulation is a revolute joint.

16. A surgical robotic component as claimed in claim 1 , wherein the second articulation is a revolute joint.

17. A surgical robotic component as claimed in claim 1 , wherein the third articulation is a spherical joint or a pair of revolute joints.

18. A surgical robotic component as claimed in claim 17 , wherein the third articulation is a universal joint.