# Mechanical Design and Testing of Mobile Monitoring Units for Security Systems
## 4 Discussion  
To date, the monitoring of different physical, chemical and biological quantities using mobile and portable systems has been undertaken mainly for environmental purposes. The main goal of this research was to create a mobile monitoring system consisting of self-standing mobile units equipped with different types of sensors to protect the perimeter of the area of interest against intruders, or on the contrary, to prohibit individuals from leaving the monitored areas. Even though the main motivation originated in the pandemic situation and the necessity to protect endangered groups of people or to secure areas suffering outbreaks of pandemics, the developed mobile monitoring security system can be used to monitor, any perimeter and thanks to the UAVs involved in the system, it can also verify alarm situations or, if necessary, track intruders or escapers. The main goal of the research presented in this article was to design mobile monitoring unit structure. The initial design with a triangular base had to be modified to meet the requirements related to the amount of accumulators needed for the functioning of the mobile monitoring unit, and also due to possible similarities with existing solutions that are a subject of intellectual property rights. Therefore, the second design with a hexagonal base was designed and analyzed, and for the confirmation of the performed analyses, it was also manufactured and tested. From the simulation and test results, it can be seen that it was necessary to modify the design, as the dynamic characteristics show that after deviation from the equilibrium state (caused, for example, by wind gusts), an inappropriately long time is necessary for the mobile monitoring unit's stabilization. However, very similar results were obtained with two tested versions of the mobile monitoring unit, with varying lengths of legs. Moreover, very good results were also obtained during the temperature dependence testing, where, due to the very good conductivity of the aluminum, with increasing exterior temperature, the resonant frequency changes were only negligible, although the solar panels were warmed significantly. This is a very important finding impacting the setting of the alarm ranges of the chosen sensors, such as accelerometers or magnetometers, which are a part of the mobile monitoring unit. The possible problems related to humidity were solved by the application of sealings, so there are no problems with, for example, changing the accumulator in cases of long-term adverse weather, or due to the placement of the mobile monitoring unit in non-ideal positions. Due to the need to optimize the design of the mobile monitoring unit, adjustable tensioning steel wire cables were added. As the correctness of the simulation model was verified during previous experiments, it was also possible to simulate versions with different tensions applied. From the simulation results, a significant improvement can be seen not only in the overall displacement amplitude, but also in the time necessary to achieve the steady state. Furthermore, the whole construction of the mobile monitoring unit was designed in pursuit of simplicity in the manufacturing process, starting from commercially available aluminum extrusion profiles to which different types of sensor holders and other attachments can be added. In the bases of the mobile monitoring units, accumulators are accommodated; therefore, the opening of the base for servicing or after transportation is possible thanks to the removable parts of the base with integrated sealings. The legs of the mobile monitoring units are height-adjustable, which enables them to be placed on uneven terrain, and thanks to the sensor equipment, the units can be easily aligned. The mounting process of the mobile monitoring unit assembly is relatively simple, which is advantageous not only to the manufacturing process, but also to the transportation of the mobile monitoring units, or the possible repair or replacement of damaged components.