# Research on Design, Simulation, and Experiment of Separation Mechanism for Micro-Nano Satellites
## 5 Experimental Verification
### Vibration Test  
A vibration test was conducted on the combination of the separation mechanism and the MF satellite to evaluate the separation mechanism's reliability during the launch stage. Six triaxial accelerometers were attached to the surface of the MF satellite and two to the separation mechanism for vibration testing, and the results were compared to those from previous simulations. The test site is depicted in Figure 15, and the vibration-testing procedure is depicted in Figure 16. Individual sine sweeps (Iss) were performed before and after the main tests to assess the separation mechanism and the MF satellite's physical damage.  
Figure 14: The curve of separation angular velocity variation.  
Figure 13: The curve of separation velocity variation.  
The first three-order natural frequencies included in simulations and ground tests are summarized in Table 8. As shown in Table 8, the 1 st mode natural frequency measured by the accelerometers during the first and final Iss tests was greater than 60 Hz for all axes, which is sufficiently high to avoid resonance with the launch vehicle. Additionally, the natural frequency changes in the first mode in the three directions before and following the vibration test are within 10%, which meets the tolerance requirements, indicating that the structure is intact and no damage occurred. Comparing the simulation and experimental values of first-order natural frequencies in three directions reveals that the simulation values are all greater than the experimental values and the error ranges are all within 10%, which meets the design requirements. The reason for this phenomenon is that the stiffness ratio of the connection between the MF satellite and the separation mechanism in the simulation model is greater than that in the actual test, and the finite element model can be modified appropriately in the later stage to account for the test structure.  
The results of the random vibration test are summarized in Table 9. The satellite's equipment has extremely small response values that meet the equipment's requirements. When the test values are compared to the simulation values in Table 7, it is discovered that the test values for the two measuring points on the separation mechanism are very close to the simulation values, whereas the test values for the satellite equipment are all less than the simulation values. This behavior is explained by the fact that the satellite and the separation mechanism are not totally fixed restrictions. There is a slight displacement between the satellite and the separation mechanism during the launch, and this minor displacement and friction absorb the energy that should be transferred to the satellite.  
Figure 16: Vibration testing procedure flow diagram.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Direction** & \multicolumn{1}{c}{**X**} & \multicolumn{1}{c}{**Y**} & \multicolumn{1}{c}{**Z**} \\ \hline \multirow{3}{*}{1 st mode natural frequency} & Numerical analysis & 77.7 & 70.8 & 82.6 \\  & First Iss test & 71.3 & 63.9 & 78.4 \\  & Final Iss test & 72.1 & 62.8 & 72.7 \\ \hline \multirow{3}{*}{Natural frequency change} & Numerical analysis/First ISS test & \(-8.2\%\) & \(-9.7\%\) & \(-5.1\%\) \\  & First/Final Iss test & \(+1.1\%\) & \(-1.8\%\) & \(-7.2\%\) \\ \hline \hline \end{tabular}
\end{table}
Table 8: Summary of natural frequency.