# Mechanical Design and Testing of Mobile Monitoring Units for Security Systems
## 3 Results
As the dynamic analysis revealed problems related to the long time intervals necessary to achieve a steady state, tensioning steel wire ropes were added to the design of the mobile monitoring unit. The simulation results for this modified design with the same length of legs and with the same applied force can be seen in Figure 10. In this case, considering a frequency of 6.23 Hz, the velocity in the analyzed point decreased to 486 mm\(\cdot\)s\({}^{-1}\). Figure 10: Dynamic frequency analysis results of the mobile monitoring unit with tensioning steel wire ropes. Figure 9: Dynamic frequency analysis results of the mobile monitoring unit without tensioning steel wire ropes. To confirm the correctness of the simulated FEM model, prototypes of the mobile monitoring units were manufactured. Experiments were performed with both versions, without and with the tensioning steel wire cables, with the same length of legs as in the case of the simulation and with same magnitude of force applied in the same point as was considered in the performed simulations. For the first prototype without the tensioning steel wire cables, the measured frequency was 3.86 Hz and the maximal amplitude in this point was 2221.81 mm\(\cdot\)s\({}^{-1}\). The measurement results can be seen in Figures 11a and 12a, where, in addition to the FFT (fast Fourier transform) analysis, the time response of the measured dynamic characteristics is visualized. As can be seen in Figures 11b and 12b, the measured frequency of the mobile monitoring unit with tensioning steel wire ropes was 6.31 Hz, and the maximal amplitude in this point was 496.31 mm\(\cdot\)s\({}^{-1}\). As can be seen, the results of the simulations and of the measurements are very similar. The simulated and measured frequencies vary only by tenths of a unit (Hertz), and the amplitudes of the velocities determined in the simulations and obtained from the measurements are comparable. \[F.h=R_{A}.r, \tag{1}\]0 Measured dynamic analysis results in the time domain for the mobile monitoring units: (**a**) without tensioning steel wire ropes; (**b**) with tensioning steel wire ropes. \[F.h=R_{A}.r, \tag{1}\]1 Measured dynamic frequency analysis results presented in the form of FFT (fast Fourier transform) analysis results for the mobile monitoring units: (**a**) without tensioning steel wire ropes; (**b**) with tensioning steel wire ropes. For a better visualization of the enhancement of the design, the measured results showing deviations from the steady are shown in \[F.h=R_{A}.r, \tag{1}\]2 From this graph, the significant improvement of time necessary to return to the steady state can also be seen. An overview of the dynamic frequency analysis results is summarized in \[F.h=R_{A}.r, \tag{1}\]3 Measurements were performed with the manufactured prototypes with long legs (with length of 665 mm), short legs (480 mm), and with and without tensioning wire cables at different temperatures. From the data obtained during the measurements, it can be seen that there was no significant difference between the prototype versions with long and short legs. Another important finding was that the construction dissipated heat very well, and therefore, no significant temperature dependence of the frequency was observed. To derive the data in Table 1, showing the measurement results for an ambient temperature of 37 \({}^{\circ}\)C, the solar panel was heated to a temperature of more than 40 \({}^{\circ}\)C, but the temperature measured in