# Structural Optimization of MicroMED Dust Analyzer
## 5 Conclusions  
This research work proposed the redesign of the optical bench for the MicroMED Dust Analyzer, an OPC developed for the ESA ExoMars 2022 mission to Mars. Topology optimization was exploited to achieve either a mass saving on the component (i.e., Model A) or a maximization of its dynamic performance (i.e., Model B). The optimal proposals allowed a reduction of about 55% of the mass budget of the considered design domain, or a first natural frequency improvement of about 50% than the current optical bench design. Both of the solutions were positively assessed via a set of FEAs (i.e., modal, quasi-static, and thermoelastic analyses) applying the conditions identified as design constraints within the mission framework and highlighting large safety factors about the limit stress for both the foreseen mechanical and thermal environment. Moreover, the thermo-elastic analyses showed that computed thermal deformation is negligible with respect to the instrument's measurement volume size, therefore validating the thermo-mechanical structural design.  
The Model A was considered the most promising proposal for the MicroMED future development. Indeed, applying the mass reduction to the overall instrument is foreseen to provide the largest benefit to MicroMED. Any additional mass saving among the mechanical hardware would allow either the possibility of proposing a cost-competitive instrument, or a redistribution of the gained mass elsewhere to enhance the functionalities of the instrument. Considering the latter option, one very attractive feature would be the possibility to quickly and easily dismount or replace the instrument components even after the integration is completed.  
Considering the attractiveness of the Model A proposal, a mockup of the optical bench was manufactured and tested to prove the robustness of the redesign workflow as well. An experimental setup was put in place to measure the mockup-free natural frequencies, obtaining a good agreement with the ones predicted via a numerical free modal analysis, i.e., a percentage error lower than 5% was found for the first four natural frequencies.  
Nevertheless, both Model A and Model B proved the effectiveness of the adopted structural optimization approach. Thus, as this research activity develops in the future, the redesign methodology will be extended to the main mechanical components of the instrument.  
Conceptualization, M.G.C. and D.S.; methodology, M.G.C., B.S. and D.S.; validation, M.G.C., B.S., F.E., G.F., C.P., G.M., F.C. and D.S.; formal analysis, M.G.C., B.S. and D.S.; investigation, M.G.C., B.S., F.E., G.F., C.P., G.M., F.C. and D.S.; writing--original draft preparation, M.G.C.; writing--review and editing B.S., F.E., G.F., C.P., G.M., F.C. and D.S.; supervision, D.S; funding acquisition, B.S. and F.E. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Italian Space Agency (ASI) with the contract ASI-INAF n. 2023-3-HH.0, project name \"Attivita Scientifica di Preparazione all'Esplorazione Marziana\" CUP F83C2300003005.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Vibrating Mode** & **Numerical [Hz]** & **Experimental [Hz]** & \(\Delta\) \\ \hline
1 st & 392 & 405 & +3.32\% \\
2 nd & 747 & 740 & \(-\)1.00\% \\
3 rd & 898 & 891 & \(-\)0.74\% \\
4 th & 990 & 986 & \(-\)0.42\% \\
5 th & 1159 & 953 & \(-\)**17.8\%** \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison between the numerical and the experimental natural frequency values.