# Human-Robot Interaction for Improving Fuselage Assembly Tasks: A Case Study
## 3 Case Study
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Before HRI**} & \multicolumn{2}{c}{**After HRI**} \\ \hline
**Operation Code** & **Human** & **Robot** & **Human** & **Robot** \\ \hline \multirow{4}{*}{OP10} & Assembly of shear ties, frames and aluminum & & Assembly of shear ties, frames and aluminum & NA \\  & strings on CFRP skin & & stringers on CFRP skin & \\  & Drilling the entire & NA & NA & Drilling the entire \\  & fuselage panel & & & fuselage panel \\  & Countersinking the & & NA & Countersinking the \\  & entire fuselage panel & NA & NA & entire fuselage panel \\  & Hole inspection & NA & NA & Hole inspection \\  & Disassembling of & NA & Disassembling of & NA \\  & aluminum stringers & & aluminum stringers & \\  & Cleaning of aluminum & & Cleaning of aluminum & NA \\  & stringers & NA & stringers & \\  & Deburring of & & Deburring of & \\  & aluminum stringers & & aluminum stringers & NA \\  & Application of sealant & NA & Application of sealant & NA \\  & Reassembling of & & Reassembling of & NA \\  & stringers on skin & & stringers on skin & NA \\  & Riveiting the entire & & & Riveiting the entire \\  & fuselage panel & NA & NA & fuselage panel \\ \hline \hline \end{tabular}
\end{table} 
Table 2: General aircraft panel assembling operations before and after HRI. speed, but its speed is modulated according to the distance from the worker and even the minimum separation distance S is adjusted in real time again on the basis of the actual robot and human relative positions and velocities (see [38] for more details). As suggested by the Step 2 of the procedure in Figure 1, also the constraints due to operations precedencies were considered for each working zone and for the whole fuselage panel in order to create a feasible working cycle. The typical sequence performed in assembling a fuselage panel is represented in Figure 3, where operations code reported in Table 2 are represented. OP10 is a preliminary operation, not considered for the analyses in this study. In some areas, the panel is reinforced with aluminum elements (see Figure 4) and the human carries out working tasks only in these areas. For this reason, in Figure 3, two paths are represented:  
1. Path 1 is followed when there are not aluminum elements in the working zone and human operations are not required;
2. Path 2 is followed when aluminum elements, such as stringers or frames, are in the working zone and also human operations are required. Figure 3: Precedence graph for operations of Table 2.  
Figure 2: (**a**) Human-hand detection by robot sensors and cameras; (**b**) trend of normalized robot speed in proximity of human (plot courtesy of [37]). The entire working cycle for HRI was defined by respecting both constraints due to standards and due to operations precedence and it was simulated in order to evaluate the working times for panel assembling and ergonomics issues. Moreover, according to Step 3 of the procedure in Figure 1, the 3D CAD models representing the new workstation were implemented for simulation in Tecnomatix Process Simulate by Siemens(r) software environment. Figure 4 represents a generic fuselage panel, for privacy reasons. In figure, a zoom of one of the working sections is represented at the bottom. Here, different working zones are visible, namely yellow and blue to indicate, respectively, the zones where only robots' operations are needed (path 1 of Figure 3), and zones where also human operations must be performed (path 2 of Figure 3). This approach has been used for each section of the panel: robots work in small areas in order to respect tolerances. Figure 5 shows a schematic configuration of the workstation in which the human and the robot share the same working area. For privacy reason, it is not represented the real station, which is provided with a scaffolding, which allows human to reach far working zones, and one of the two robots moves on a horizontal support.