## 7 Results and Discussion
### Results
Aiming to reduce these idle times and enable cooperation, the proposed procedure specifies the time when workers are expected to perform tasks together during the cycle time through proper synchronization of their workloads. Figure 11a shows the cooperation between Workers 1 and 2 of Workstation II as an example. They cooperate for \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{6}{c}{**Workbook of Worker 1 in Workstation II**} \\ \hline \multirow{2}{*}{**Task ID**} & **Start Time** & **End Time** & **Mounting** & **Equipment** & **Needed** & **Collaboration** \\  & **[S]** & **[S]** & **Position** & **Needed** & **Collaboration** \\ \hline
446 & 0 & 225 & HIGH\_13 & - & no \\
78 & 226 & 607 & LOW\_1 & G & no \\
80 & 608 & 676 & LOW\_1 & - & no \\
466 & 677 & 908 & HIGH\_12 & - & no \\
473 & 909 & 972 & MED\_4 & - & no \\
73 & 973 & 1214 & HIGH\_12 & - & no \\
240 & 1215 & 1339 & HIGH\_12 & R & no \\
531 & 1340 & 1397 & HIGH\_12 & - & no \\
558 & 1398 & 3409 & LOW\_1 & - & no \\
582 & 3410 & 3530 & LOW\_1 & - & with Worker 2 \\
632 & 3531 & 3671 & LOW\_1 & F & no \\
563 & 3672 & 3778 & LOW\_1 & - & no \\
279 & 3779 & 3865 & HIGH\_12 & - & no \\
277 & 3866 & 3905 & MED\_13 & - & no \\
66 & 3906 & 3997 & HIGH\_12 & - & no \\
84 & 3998 & 4062 & HIGH\_12 & - & no \\
82 & 4086 & 4217 & HIGH\_12 & - & no \\
104 & 4218 & 4240 & TOP\_3 & - & no \\
120 & 4241 & 4293 & TOP \_2 & - & no \\
127 & 4294 & 4481 & TOP\_2 & - & no \\
138 & 4482 & 4599 & TOP\_2 & - & no \\
143 & 4600 & 4743 & TOP\_2 & - & no \\
137 & 4744 & 4812 & TOP\_2 & - & no \\
648 & 4813 & 5113 & HIGH\_8 & - & no \\
431 & 5114 & 5148 & MED\_12 & - & no \\
583 & 5149 & 5338 & LOW\_1 & - & with Worker 2 \\
69 & 5339 & 5585 & HIGH\_12 & - & no \\
103 & 5586 & 5650 & TOP\_3 & - & no \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Example of an assembly line worker workbook. Figure 10: Equipment, number of workers, and their saturation for each workstation. part of the cycle time (from 3410 s to 3530 s) to complete task 582 and then resume their work individually. Tracking of mounting position and equipment usage throughout the entire cycle time is necessary to provide a feasible task assignment to workers at each individual workstation. This monitoring allows to defining exactly when tasks can start to be processed because all constraints are fulfilled. For sake of exemplification, Figure 11b shows the mounting position _HIGH_12_ occupation in Workstation II over a portion of the cycle time. Worker 2 can start task 253 execution in _HIGH_12_ after completion of task 531 by Worker 1 in the same mounting position to avoid overlap. Similarly, Figure 11c illustrates the utilization of the pieces of equipment assigned to Workstation II. The proposed procedure considers the non-duplication of equipment within a workstation as a constraint. Indeed, only one copy of each piece of equipment is allocated to Workstation II because it is shared by workers who use it at different times. The piece of equipment \(R\) is employed first by Worker 1 to perform task 240 and only later by Worker 2 to complete task 70. The same applies to the piece of equipment \(G\). Figure 11: Examples of the real-world constraints in the assembly line synchronization. (**a**) An example of collaboration between two workers in the same workstation; (**b**) Mounting position HIGH_12 scheduling at workstation II; (**c**) Pieces of equipment scheduling at workstation II.