**6. Conclusions**

In this paper, a set of three different metaheuristic search algorithms have been considered for failure detection and identification purposes. This work was aimed at testing new algorithms to identify some suitable ones. After having introduced the scenario in which this kind of PHM system could provide useful insights, a brief description of the models have been reported. Particular attention has been given to failure description and implementation, as well as the general methodology overview. A detailed description of the three algorithm has also been reported, in order to enable the reader to understand the most important aspect of each MSA, without the need of additional resources. Finally, the results are shown in a schematic way, highlighting the methodology performance with the use of purpose built coefficients. Further research should focus on the ideal interval between prognostic checks, in order not to jeopardize mission safety and not overloading the PHMC. On top of that, the running time of these routines can definitely be improved with other models or with more performing algorithms. This is why future work should consider other MSAs and other failures inside the EMA, as well as investigate on the unexpected result, regarding the multiple failure condition running time. Finally, if we compare the results of this study (specifically for PMSM-based EMAs) with the outcomes obtained in [23] for BLDC-based EMAs, it is clear that PSO is confirmed as the best performing algorithm, even though the core of the system has changed.

**Author Contributions:** Conceptualization, M.D.L.D.V.; methodology, M.D.L.D.V.; software, M.D.L.D.V.; validation, I.Q.; formal analysis, I.Q.; investigation, I.Q.; resources, I.Q.; data curation, I.Q.; writing—original draft preparation, L.B.; writing—review and editing, L.B.; visualization, L.B.; supervision, M.D.L.D.V.; project administration, M.D.L.D.V.; funding acquisition, P.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare that they have no known conflict of interest nor competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
