Magnetic position sensor mounting arrangement

Abstract

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 complises 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 momlted 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 comprising:
 a disc comprising a mounting arrangement by which the disc is configured to be mounted to a jig during manufacture and an articulated structure during operation, the mounting arrangement permitting the disc to be mounted to the jig and articulated structure in a single orientation only.   
     
     
         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 a set of mounting features which form a rotationally asymmetrical pattern on the disc. 
     
     
         6 . A position sensing arrangement as claimed in  claim 5 , wherein the mounting features are through-holes. 
     
     
         7 . A position sensing arrangement as claimed in  claim 5 , wherein the mounting features are pins. 
     
     
         8 . 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 jig and articulated structure. 
     
     
         9 . A position sensing arrangement as claimed in  claim 1 , wherein:
 the disc is configured to be mounted to the jig during manufacture and the articulated structure during operation such that during operation the disc rotates about an axis; and   the mounting arrangement permits the disc to be mounted to the jig and articulated structure in a single rotational orientation about the axis only.   
     
     
         10 . A position sensing arrangement as claimed in  claim 1 , wherein the mounting arrangement permits the disc to be mounted to the jig and articulated structure in a single orientation only in order that the mounting arrangement is configured to ensure that the disc is mounted to the jig during manufacture and to the articulated structure during operation in the same orientation. 
     
     
         11 . A position sensing arrangement as claimed in  claim 1 , wherein the jig is a magnetisation jig. 
     
     
         12 . A position sensing arrangement as claimed in  claim 1 , wherein the disc further comprises a first magnetic ring with m magnetic pole pairs, and a second magnetic ring with n magnetic pole pairs. 
     
     
         13 . A position sensing arrangement as claimed in  claim 12 , where m and n are co-prime. 
     
     
         14 . A position sensing arrangement as claimed in  claim 12 , wherein the first magnetic ring and the second magnetic ring are magnetised when the disc is mounted to the jig during manufacture. 
     
     
         15 . A position sensing arrangement as claimed in  claim 12 , wherein the first magnetic ring and the second magnetic ring are concentric. 
     
     
         16 . A position sensing arrangement as claimed in  claim 12 , wherein the second magnetic ring is radially separated from the first magnetic ring by a predetermined distance. 
     
     
         17 . A position sensing arrangement as claimed in  claim 12 , wherein the predetermined distance is at least the length of a magnetic pole pair. 
     
     
         18 . A position sensing arrangement as claimed in  claim 12 , where |m-n|>7. 
     
     
         19 . A position sensing arrangement as claimed in  claim 12 , wherein the first and second magnetic rings are disposed on the same surface of the disc. 
     
     
         20 . A position sensing arrangement as claimed in  claim 12 , wherein the first and second magnetic rings are disposed on opposing surfaces of the disc.