## 4 System-Level Design
### Functional and Logical Architecture Definition  
The system was analyzed from an internal point of view to define progressively its architecture. The main functions of the system were established starting from the set of the functional requirements previously defined. Each function must meet one or more requirements. The identified functions are  
1. **Data acquisition and elaboration**: the system acquires and elaborates data coming from the external interfaces to give the command signal to move or stop. 2. **Measurement**: in this phase, data about motion, such as position and speed, are collected and sent as feedback. Data are also relative to the power consumption of the electric motor. 3. **Motion**: it is a rotation around its own axis that starts when a signal commands motion. 4. **Safety stop**: this activity takes place when an impact occurs. In this case, an alert is sent to the human operator. \begin{table}
\begin{tabular}{l l} \hline \hline
**ID** & **Requirement** \\ \hline
1 & The system shall allow the integration between cobots and mobile robots belonging to target groups, by improving safety and minimizing cost, height, and energy consumption. \\ \hline
1.1 & The system shall allow the relative motion of cobot with respect to mobile robot around a vertical axis. \\ \hline
1.1.1 & The system shall have a part rigidly fixed to mobile robot \\ \hline
1.1.2 & The system shall have a part rigidly fixed to cobot \\ \hline
1.1.3 & The system shall be actuated \\ \hline
1.2 & The system shall adapt to cobot and mobile robot. \\ \hline
1.2.1 & The system shall have dimensions compatible with cobot and mobile robot. \\ \hline
1.2.2 & The system shall hold the weight of cobot. \\ \hline
1.3 & The system shall be safe for human operators. \\ \hline
1.3.1 & The system shall recognize possible collision with a human operator. \\ \hline
1.3.1.1 & The system shall alert the human operator in case of a possible collision. \\ \hline
1.3.1.2 & The system shall slow down or stop in case of possible collision \\ \hline
1.3.2 & The system shall determine limited impact force with human operator \\ \hline
1.4 & The system shall have a minimum cost. \\ \hline
1.5 & The system shall have a minimum height. \\ \hline
1.6 & The system shall work with energy-saving. \\ \hline
2 & The system shall be maintainable. \\ \hline
3 & The system shall be easily assembled and disassembled fulfilling ergonomic constraints. \\ \hline
4 & The system shall be protected from dust and dirt. \\ \hline
5 & he system shall ensure a high accuracy in the cobot motion. \\ \hline
6 & The system shall have a minimum weight. \\ \hline
7 & The system shall operate autonomously. \\ \hline
8 & The system shall be powered by a mobile robot battery. \\ \hline
9 & The system shall receive data about the requested task and send data about its status. \\ \hline
9.1 & The system shall receive information when the mobile robot reached its position. \\ \hline
9.2 & The system shall receive information about the required cobot rotation. \\ \hline
9.3 & The system shall send data to cobot when the rotation is completed. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: System level requirements. Based on the identified functions, the system is defined in terms of logical components. Each function is entrusted to a logical component belonging to a general technological class (e.g., motors, controllers, sensors) but not yet fully defined. This process is called \"Logical breakdown and allocation\"; the results arising from it are summarized in Table 2.  
Then, logical components interaction resulting in the logical architecture of the system was defined (Figure 11). At this point, the most suitable physical components have to be allocated to define the physical architecture of the whole system. Consistency must be guaranteed by associating the physical components with the related logical ones. However, physical components of the interface have been designed and selected after the simulation of the system.