IEEE 1856-2017 pdf download

IEEE 1856-2017 pdf download.IEEE Standard Framework for Prognostics and Health Management of Electronic Systems.
d) PHM system performance is measured for its contribution to achieving or improving object system goals. PHM system performance shall be measured in terms of metrics chosen from the following categories:
I) Accuracy: Accuracy is a measure of deviation of a prognostic or diagnostic output of current object system state from measured, observed, or inferred ground truth. Accuracy shall be measured by comparing prognostic and diagnostic outputs from measured ground truth using several metrics (Saxena, et al., 2010 [B14]7) such as, hut not limited to, detection accuracy, isolation accuracy, and prognostic system accuracy. These terms are defined in the normative definitions section above.
2) Timeliness: Timeliness is a measure of how quickly the PHM system’s functions produce their outputs in relation to the failure effects that they are mitigating. Overall timeliness includes the total time of state estimation and control for the PHM Control Loop. The timeliness from prediction or detection through response shall be summed up to compare to the time required for the thilure mitigation. If desired, comparisons for the prognostics function and the health management function shall he made separately by grouping the relevant sub-functions. The timeliness aspects of the PHM sub-functions that contribute to the total PHM Loop include detection time, diagnostic time, prognostic time, decision time, and response time. These terms are defined in the normative definitions section above.
3) Confidence: Confidence is a measure of trust (or, conversely, a measure of uncertainty) in a PHM system’s output. For detection and diagnostic functions, it is computed through, but not limited to, robustness, sensitivity, and uncertainty metrics. For prognostics it is specified by including the estimation of uncertainty in predictions and stability of predictions over time, in addition to sensitivity and robustness measures (Saxena, et al., 2010 [B 14]).
4) Effectiveness: Effectiveness is a measure of the PHM system’s ability to preserve or attain relevant system goals. Typical effectiveness goals include system reliability, safety, performance, cost, or schedule. The sub-metrics of accuracy, timeliness, and confidence shall be combined for specific PHM mechanisms and for the PHM as a whole for the system to generate the PHM effectiveness measured against the relevant system goals, as allocated to PHM.
5) And, any additional metrics as defined in the PHM or object system specifications.
e) PHM system performance shall be tracked over time to determine if a need exists to either update the PHM system (e.g., models, instrumentation, algorithms, rules, etc.) or performance measurement methods and metrics. The tracking system shall be capable of documenting all anomalies and failures during testing and operation, including tests and analyses to confirm them. The tracking system shall also document the outcomes and reports of the resulting investigations, design and operational modifications, and the results of tests of these modifications. Finally, the tracking system shall be capable of generating metrics regarding all of the above.
NOTE—The illustrations and notes presented in this Clause are provided to help the reader to understand the concepts and are not a requirement of the standard.
Figure 1 presents the times related to health monitoring and prediction events in the operational life of an object system. First of all, the designer specifies the upper and lower failure thresholds, and the upper and lower off-nominal thresholds for the PHM sensor in the system. Here, t0 can be assumed to start at any time, e.g., when the system is turned on, and tE is the occurrence of the off-nominal event. Off-nominal events occur when the PHM sensor measures an exceedance of the threshold limits specified by the PHM designer. The PHM metrics are initiated when such an event is detected at time (tD) by a PHM system. The PHM system
TThe numbers in brackets correspond to those of the bibliography in Annex B.