| CPC G01L 3/101 (2013.01) | 19 Claims |

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1. A system for sensing torque in a rotatable shaft, the system comprising:
a target region extending along at least a portion of a length of the shaft, the target region comprising a first set of target elements and a second set of target elements, each of which are arranged about the shaft in a circumferential direction thereof, wherein the first set of target elements are on an outer surface of the shaft at a first position and the second set of target elements are attached to the outer surface of the shaft at a second position;
a first sensor and a second sensor, which are configured to measure a circumferential distance between adjacent target elements of the first and second sets of target elements, wherein the distance measured between the adjacent target elements is used to calculate torque transmitted through the shaft over the target region;
a bearing having an inner race and an outer race, the inner race being supported by, and in contact with, the outer surface of the shaft, such that the inner race and the shaft are rotatably locked together;
a frame fixedly mounted to the outer race of the bearing, such that the frame maintains a substantially constant radial distance from the shaft; and
a compliant mount attaching the frame to a fixed structure, such that the frame is configured to move substantially in unison with the shaft, relative to the fixed structure, in at least two dimensions, the at least two dimensions being in a plane perpendicular to a longitudinal axis of the shaft;
wherein the shaft is configured to rotate relative to the frame; and
wherein the first and second sensors are rigidly attached to the frame, such that a gap between each of the first and second sensors and the outer surface of the shaft in the target region is substantially constant.
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