# Development of Piezoelectric Inertial Rotary Motor for Free-Space Optical Communication Systems
## 5 Conclusions  
A novel piezoelectric inertial motor was designed, developed, and tested for operation in low Earth Orbit (LEO) temperature conditions. The motor, based on the inertial stick-slip principle using the first bending mode of the piezoelectric bimorph plates, is compact and lightweight with a total volume of 443 cm\({}^{3}\) and a mass of 28.14 g, which makes it highly applicable for small satellite applications. The experimental results show that the motor resonance frequency decreases from 12,810 Hz at \(-20\)\({}^{\circ}\)C to 12,640 Hz at 40 \({}^{\circ}\)C, a deviation of 170 Hz. The stator's displacement amplitude increases from 12.61 \(\upmu\)m at \(-20\)\({}^{\circ}\)C to 13.31 \(\upmu\)m at 40 \({}^{\circ}\)C, demonstrating enhanced mechanical responsiveness at higher temperatures. The motor achieved a maximum angular speed of 1178 RPM and a stall torque of 13.1 N\(\cdot\)mm at 180 V\({}_{\text{P-P}}\). Despite these variations, the motor maintained consistent performance, confirming its mechanical stability and adaptability to temperature fluctuations in space environments. The low mass, compact design, and ability to operate reliably over a wide range of temperatures make this motor a promising solution for small satellite applications. It is particularly well suited for tasks requiring precision, such as satellite orientation and free-space optical (FSO) communications, where size, efficiency, and stability are critical.  
Conceptualization, L.S., A.C., and D.M.; methodology, L.S. and A.C.; software, L.S. and D.M.; validation, L.S. and A.C.; formal analysis, D.M. and S.B.; investigation, L.S. and A.C.; resources, D.M.; data curation, L.S. and S.B.; writing--original draft preparation, L.S. and A.C.; writing--review and editing, D.M. and S.B.; visualization, L.S.; project administration, D.M. All authors have read and agreed to the published version of the manuscript.  
This project has received funding from the Research Council of Lithuania, agreement no. S-MIP-22-61.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Proposed Motor** & **[PERSON] et al. (2016)** & **[PERSON] et al. (2017)** & **[PERSON] et al. (2018)** \\ \hline Motor operation & & & & \\ principle & Inertial & Inertial & Inertial & Traveling wave \\ Footprint area & & & & \\ (mm\({}^{\circ}\)) & 1384 & 2827 & 8850 & 5600 \\ Weight (g) & 28.14 & 50 & 1200 & 300 \\ Angular speed & 1178 @ 180 V\({}_{\text{P-P}}\) & 2360 & 3 & 53.86 @ 250 V\({}_{\text{P-P}}\) \\ (RPM) & 13.1 @ 180 V\({}_{\text{P-P}}\) & 1.3 & 93 & 110 @ 250 V\({}_{\text{P-P}}\) \\ Torque (N\(\cdot\)mm) & 0.22 @ 40 V\({}_{\text{P-P}}\) & 0.66 \(\upmu\)rad & 3.8 \(\times\) 10\({}^{-5}\) & 1.29 @ 250 V\({}_{\text{P-P}}\) \\ Resolution & & & & \\ (\({}^{\circ}\)/V\({}_{\text{P-P}}\)) & 0.22 @ 40 V\({}_{\text{P-P}}\) & 0.66 \(\upmu\)rad & 3.8 \(\times\) 10\({}^{-5}\) & 1.29 @ 250 V\({}_{\text{P-P}}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison between piezoelectric motors.