Magnetic position sensor mounting arrangement
A position sensing arrangement for sensing the position of a revolute joint of an articulated structure. The position sensing arrangement comprises a disc and a magnetic sensor assembly. The disc comprises a first magnetic ring with m magnetic pole pairs, and a second magnetic ring with n magnetic pole pairs, where m and n are co-prime, and a mounting arrangement by which the disc is mountable to a magnetisation jig during manufacture and the articulated structure during operation, the mounting arrangement permitting the disc to be mounted to the magnetisation jig and articulated structure in a single orientation only. The magnetic sensor assembly comprises a first magnetic sensor array for detecting the magnetic pole pairs of the first magnetic ring, and a second magnetic sensor array for detecting the magnetic pole pairs of the second magnetic ring.
1. A position sensing arrangement configured to sense the position of a revolute joint of an articulated structure, the position sensing arrangement comprising:
a disc comprising:
a first magnetic ring with m magnetic pole pairs, and a second magnetic ring with n magnetic pole pairs, where m and n are co-prime, and
a mounting arrangement by which the disc is mountable to a magnetisation jig during manufacture and the articulated structure during operation, the mounting arrangement permitting the disc to be mounted to the magnetisation jig and articulated structure in a single orientation only; and
a magnetic sensor assembly comprising: a first magnetic sensor array configured to detect the magnetic pole pairs of the first magnetic ring, and a second magnetic sensor array configured to detect the magnetic pole pairs of the second magnetic ring.
2. A position sensing arrangement as claimed in claim 1 , wherein the mounting arrangement comprises a set of mounting features which form an asymmetrical pattern on the disc.
3. A position sensing arrangement as claimed in claim 2 , wherein the mounting features are through-holes.
4. A position sensing arrangement as claimed in claim 2 , wherein the mounting features are pins.
5. A position sensing arrangement as claimed in claim 1 , wherein the mounting arrangement comprises an alignment notch in the disc configured to align with a corresponding feature of the magnetisation jig and articulated structure.
6. A position sensing arrangement as claimed in claim 1 , wherein the first magnetic ring and the second magnetic ring are concentric.
7. A position sensing arrangement as claimed in claim 1 , wherein the second magnetic ring is radially separated from the first magnetic ring by a predetermined distance.
8. A position sensing arrangement as claimed in claim 7 , wherein the predetermined distance is at least the length of a magnetic pole pair.
9. A position sensing arrangement as claimed in claim 1 , where |m−n|>1.
10. A position sensing arrangement as claimed in claim 1 , where |m−n|>7.
11. A position sensing arrangement as claimed in claim 1 , wherein the first and second magnetic rings are disposed on the same surface of the disc.
12. A position sensing arrangement as claimed in claim 1 , wherein the first and second magnetic rings are disposed on opposing surfaces of the disc.
13. A position sensing arrangement as claimed in claim 1 , wherein the length of each of the first and second magnetic sensor arrays is the same as or smaller than the length of a magnetic pole pair.
14. A position sensing arrangement as claimed in claim 1 , wherein the first magnetic sensor array has a radial extent less than the radial extent of the first magnetic ring, and the second magnetic sensor array has a radial extent less than the radial extent of the second magnetic ring.
15. A position sensing arrangement as claimed in claim 1 , wherein each of the first and second magnetic sensor arrays is rectilinear.
16. A position sensing arrangement as claimed in claim 1 , wherein each of the first and second magnetic sensor arrays comprises four sensors.
17. A position sensing arrangement as claimed in claim 1 , wherein the disc further comprises a third magnetic ring having h magnetic pole pairs, wherein m, n and h are co-prime and |h−m|>1 and |h−n|>1.
18. A position sensing arrangement as claimed in claim 17 , wherein the first, second and third magnetic rings are concentric.