# Mechanical Design and Testing of Mobile Monitoring Units for Security Systems
## 2 Materials and Methods
### Mobile Monitoring Units  
The construction of the mobile monitoring unit must be designed so it can be used in different environments, involving rugged terrain and difficult weather conditions, and it also has to use strong and durable materials while maintaining a low weight for transportation. To meet all the requirements, several 3D models of the mobile monitoring unit were created. The designs of the mobile monitoring unit were created in Creo-Parametric software 10 to create an accurate and detailed model that would meet the required criteria. Creo-Parametric allows the creation of complex 3D models using parametric tools and thus facilitates the process of the design and simulation of various conditions. In this way, the first design of the mobile monitoring unit was created--see Figure 2a. The second design of the mobile monitoring unit was created based on the first design (see Figure 2b), which provided the basic concept and appearance of the unit. However, this second design considers functionality, assemblage, robustness, the mounting of the construction and, last but not least, the intellectual property rights. The mechanical design was created so it can be assembled from commercially available components and construction parts, simplifying the manufacturing process and reducing manufacturing costs. It was also created with an emphasis on functionality, practicality and the manufacturing process, while the required structural design remained unchanged. This design and the  
Figure 1: Software for the mobile monitoring system—warnings and alarms. 3D model also allow faster and more accurate testing of the mobile monitoring units, and modifications of the mechanical design, if necessary. The mechanical design of the mobile monitoring unit is constructed on a hexagonal base made from aluminum extrusions and plates, which provides a solid foundation and also houses the accumulators. This ensures that the center of gravity of the mobile monitoring units is low enough to offer added stability to the construction. A vertical profile is attached to this basis, which aids in the placement of sensors and the solar panel on the top of the construction. To the lower part of the base, three independently height-adjustable legs are attached to ensure stability. The height of each individual leg is manually adjustable and thus the unit can be leveled and stabilized, even on uneven terrain. The main part of the mobile monitoring unit is made from special anodized aluminum profiles that provide sufficient strength and durability to the construction (Figure 2(a)). These profiles are equipped with longitudinal grooves and holes for fixing the connecting components and different accessories. The surfaces of the profiles are resistant to corrosion and scratching, with an emphasis on material durability and reliability. The concept of these profiles allows for great variability, high precision and strength, and the possibility of repeated use of the system components, while the mounting process is relatively simple. Our design employs profiles of the 8 series, which are basic aluminum profiles. According to the manufacturer's product description, this robust profile can be used for the maximum tensile stress load on the groove of up to 5000 N, with M8 bolts. The base of the construction is sheathed with aluminum sheets, which provide protection for the accumulators, sensors and other devices placed in this part of the unit. As the mobile monitoring units are primarily designed for applications in exterior environments, the aluminum sheet plates ensure protection in various weather conditions, involving rain, snow, or dust. Furthermore, the base is equipped with custom-made rubber seals, which provide additional protection against external influences such as humidity, which is important not only for the accumulators but also for the sensors and related electronics, as water droplets can create undesirable conductive paths, which can result in wrong measurement results or even damage to the sensors or electronics.