US 11,054,282 B2
Magnetic position sensor for sensing position of a revolute joint
Paul Christopher Roberts, Cambridge (GB); and Edward John Mottram, Cambridge (GB)
Assigned to CMR SURGICAL LIMITED, Cambridge (GB)
Appl. No. 16/319,284
Filed by CMR Surgical Limited, Cambridge (GB)
PCT Filed Jul. 19, 2017, PCT No. PCT/GB2017/052125
§ 371(c)(1), (2) Date Jan. 18, 2019,
PCT Pub. No. WO2018/015750, PCT Pub. Date Jan. 25, 2018.
Claims priority of application No. 1612768 (GB), filed on Jul. 22, 2016.
Prior Publication US 2019/0265069 A1, Aug. 29, 2019
Int. Cl. G01D 5/14 (2006.01); G01D 5/245 (2006.01); G01D 5/249 (2006.01)
CPC G01D 5/145 (2013.01) [G01D 5/2452 (2013.01); G01D 5/2497 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A method of assembling a position sensing arrangement configured to sense the position of a revolute joint attaching a first shaft and a second shaft of an articulated structure, the position sensing arrangement comprising a magnetic sensor assembly and a disc having a first magnetic ring with j magnetic pole pairs and a second magnetic ring with k magnetic pole pairs, where |j−k|>1, a boundary of the disc being constrained by the articulated structure, the method comprising:
determining a number of pole pairs of the first magnetic ring p such that the first magnetic ring is separated from the constrained boundary by at least the magnetic sensor assembly;
determining a number of pole pairs of the second magnetic ring to be an integer q such that the second magnetic ring is separated from the first magnetic ring by a predetermined distance; and
if p and q are co-prime:
selecting j to be p and k to be q; and
assembling the position sensing arrangement by:
mounting the disc to one of the first shaft and the second shaft such that both the disc and the revolute joint are permitted to rotate about the same axis; and
mounting the magnetic sensor assembly to the other of the first shaft and the second shaft so as to enable detection of relative rotation of the first shaft and the second shaft.