TECHNICAL FIELD

The subject matter described in this specification relates to methods and systems for measuring displacement parameters of rotating shafts and couplings.

BACKGROUND

Many types of systems include a rotatable shaft. For example, electric motors, internal combustion engines, and transmissions of vehicles and manufacturing systems typically include one or more drive shafts. Shafts can be coupled together with rotational couplings, and some rotational couplings are flexible. For example, bellows couplings allow for twisting and misalignment between two shafts. Conventional measurement systems for monitoring rotational couplings measure twist, torque, and misalignment at rotational couplings using, e.g., sensors angularly spaced around the coupling. These conventional measurement systems, however, may have excess noise on the torque signal, and various conventional measurement systems lack an economical system for measuring both twist, torque, and misalignment and other parameters such as axial displacement. There is a need for methods and systems for measuring twist and axial displacement of rotating shafts and couplings.

SUMMARY

In some aspects, a measurement system includes a shaft extended in a longitudinal direction and a target wheel configured to rotate with the shaft. The target wheel includes sensor targets circumferentially distributed around the target wheel. Some of the targets are slanted in the longitudinal direction and some of the targets are parallel to the longitudinal direction. The measurement system includes a sensor array including at least three sensors mounted radially around the shaft and configured to detect the sensor targets as the target wheel rotates with the shaft. The measurement system includes a controller configured to receive sensor signals from the sensors and determine, based on the sensor signals, at least an axial displacement measurement of the shaft in the longitudinal direction and a radial displacement measurement of the shaft.

In some aspects, a method performed by a controller of a measurement system includes receiving sensor signals from each of at least three sensors mounted radially around a shaft on a sensor array. The shaft is extended in a longitudinal direction, and the sensor array is configured to position the at least three sensors for detecting sensor targets circumferentially distributed around a target wheel as the target wheel rotates with the shaft. The sensor targets include a first plurality of targets that are slanted in the longitudinal direction and a second plurality of targets that are parallel to the longitudinal direction. The method includes determining, based on the sensor signals, at least an axial displacement measurement of the shaft in the longitudinal direction and a radial displacement measurement of the shaft.

