  Condition-based maintenance of rotating mechanics requests efficient bearings
degradation monitoring. The accuracy of bearings degradation measure depends
largely on degradation indicators. To extract efficient indicators, in this
paper we propose a method based on the discarded projected space information
and piecewise linear representation (PLR) to build three bearings degradation
monitoring indicators which are named SDHT2, VSDHT2 and NVSDHT2. The discarded
projected space information is measured by the segmented discarded Hotelling T
square we propose in this paper. For illustration, the IEEE PHM 2012 benchmark
dataset is used in this paper. The results show that the three new indicators
are all sensitive and monotonic during the bearings whole lifecycle. They
describe the whole degradation process history and carry the real-time
information of bearings degradation. And NVSDHT2 is the generalised version of
VSDHT2, which is promising to monitor bearings degradation.
