Method of controlling a surgical robot
A method of controlling movement of the tip of a surgical endoscope from a first position (E) to an intermediate position (E′), the field of view from the tip of the endoscope being at an angle (α) relative to a longitudinal shaft of the endoscope, the method comprising: receiving a command to move from the first position in a first direction; identifying a nominal view point (N) from the tip of the endoscope in the first position; calculating a tip movement path from the first position based on the received command, the identified nominal view point and the angle (α); determining the intermediate position; and moving the tip to the intermediate position, the intermediate position being such that the nominal view point remains within the field of view from the tip.
1. A method of controlling movement of the tip of a surgical endoscope from a first position (E) to an intermediate position (E′), the field of view from the tip of the endoscope being at an angle (a) relative to a longitudinal shaft of the endoscope, the method comprising:
receiving a command to move from the first position in a first direction;
identifying a nominal view point (N) from the tip of the endoscope in the first position;
calculating a curved tip movement path from the first position based on the received command, the identified nominal view point and the angle (a);
determining the intermediate position; and
moving the tip to the intermediate position, the intermediate position being such that the nominal view point remains within the field of view from the tip,
wherein the curved tip movement path is either elliptical or a circle passing through a pivot point (V), the first position (E) and the nominal view point (N).
2. A method according to claim 1 , wherein the calculating step includes calculating a tangent to the curved path at E.
3. A method according to claim 2 , wherein the tangent lies in a plane containing V, E and N.
4. A method according to claim 2 , wherein the intermediate position is along the tangent.
5. A method according to claim 1 , wherein movement of the tip is along the tip movement path.
6. A method according to claim 2 , wherein the movement of the tip to the intermediate position is along the tangent.
7. A method according to claim 1 , wherein, once the tip is in the intermediate position, the method further comprises (i) recalculating the tip movement path from the intermediate position, (ii) determining a new intermediate position and (iii) moving the tip to the new intermediate position.
8. A method according to claim 7 , wherein steps (i) to (iii) are repeated until the intermediate position becomes the final position.
9. A method according to claim 1 , wherein the nominal view point (N) is at a distance (n) from the tip, wherein n is fixed.
10. A method according to claim 1 , wherein the nominal view point (N) is at a distance (n) from the tip, wherein n is variable.
11. A method according to claim 10 , wherein the first direction includes a component of motion that changes n.
12. A method according to claim 1 , wherein the command includes a command to either zoom in towards the nominal view point or zoom out away from the nominal view point.
13. A method according to claim 1 , wherein the nominal view point does not alter.
14. A method according to claim 1 , wherein the angle (a) is plus or minus 30, 45 or 60 degrees relative to the longitudinal shaft of the endoscope.
15. A method according to claim 1 , wherein, during the moving step, the endoscope moves axially through a pivot point through which the endoscope must pass.
16. A method according to claim 1 , wherein the first direction comprises one or more components of motion from the following: motion in the x axis; motion in the y axis; motion in the z axis; pitch; roll; or yaw.
17. A method according to claim 1 , wherein the step of calculating the intermediate position includes determining the centre O of the circle using the following:
O
W
=
V
W
+
[
±
r
2
-
(
d
2
)
2
0
d
/
2
]
where r is the radius of the circumcircle of triangle (V, E, N) and d is the depth of the endoscope within the patient.
18. A method according to claim 1 , wherein the radius (r) is determined using the depth (d) of the endoscope from the V and the predetermined distanced (n) using the following:
r
=
d
2
+
n
2
+
dn
3
19. A surgical robot having a controllable arm on which a surgical endoscope can be mounted and a control unit configured to carry out a method of controlling movement of the tip of a surgical endoscope from a first position (E) to an intermediate position (E′), the field of view from the tip of the endoscope being at an angle (a) relative to a longitudinal shaft of the endoscope, the method comprising:
receiving a command to move from the first position in a first direction;
identifying a nominal view point (N) from the tip of the endoscope in the first position;
calculating a curved tip movement path from the first position based on the received command, the identified nominal view point and the angle (a);
determining the intermediate position; and
moving the tip to the intermediate position, the intermediate position being such that the nominal view point remains within the field of view from the tip,
wherein the curved tip movement path is either elliptical or a circle passing through a pivot point (V), the first position (E) and the nominal view point (N).