# Reconfiguration Decision-Making of IoT based Reconfigurable Manufacturing Systems
## 6 Experimental Verification
### Result Analysis  
The system suggested in this study provided its efficiency in various reconfiguration situations. The experimental results according to IoT application and reconfiguration situations are presented in Table 7. The 'performance ratio compared without reconfiguration' means a value when the number of the demands fulfilled without reconfiguration within the due date is compared with the number of the fulfilled demands with reconfiguration. The mean value of the satisfied demands without reconfiguration was 35.62 and was used as a reference value for performance comparison. The IoT based system in four reconfiguration situations was expected to spend an additional cost. However, there was no big difference in cost, however, in performance comparison, the system performance was significantly different before reconfiguration and after reconfiguration. Situations 1 and 2 (changes in demands) had lower average performance than situations 3 and 4 (changes in machines), which seems to be because of delays in the schedule made by the forced reconfiguration of machines, and more machine replacement caused more cost. When IoT was not applied, situations 2 and 4 (easy prediction and the prior application to a plan) were less different from situations 1 and 3. There were more delayed demands and lower cost gains when IoT was not applied than when IoT was applied. This is because the delay made was due to a situational awareness delay and the prolonged time for stabilization after reconfiguration often caused the demand to exceed the deadline in reconfiguration situation 3. The different performance of the model according to the number of processes for production is presented in Table 8. When there were more processes, it took more time to devise a reconfiguration plan. The greater the number of processes, the lower the reconfiguration performance. This is because, in a greater number of processes, individual demands are highly likely to be influenced by reconfiguration delay, which in turn leads to a higher cost. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & & **Situation** & **Prediction** & **Remarks** \\ \hline
1 & Change of production ratio & Unpredicted ratio changes one week after starting & Unpredictable & \\
2 & Introduction of additional & Insert additional processes one week after starting & Predictable & \\  & & & & Delay in \\
3 & Breakdown & Sudden breakdown of the machine and & & \\  & & subsequent reconfiguration & Unpredictable & \\
4 & Preventive maintenance & Preventive maintenance and reconfiguration are & Predictable & \\  & & planned after one week & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Reconfiguration situations in simulation experiment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**IoT** & **Situation** & \begin{tabular}{c} **Number of** \\ **Satisfied** \\ **Demands** \\ \end{tabular} & \
\begin{tabular}{c} **Performance Ratio** \\ **Compared without** \\ **Reconfiguration (\%)** \\ \end{tabular} & **Total Cost** &
\begin{tabular}{c} **Calculation** \\ **Time (sec)** \\ \end{tabular} \\ \hline \multirow{4}{*}{Applied} & 1 & 29.53 & 82.92 & 2047.3 & 92.02 \\  & 2 & 30.69 & 86.15 & 2057.1 & 89.25 \\  & 3 & 28.19 & 79.14 & 3972.4 & 97.6 \\  & 4 & 29.97 & 84.15 & 4020 & 93.68 \\  & 1 & 27.37 & 76.85 & 2116.9 & 97.81 \\ Not applied & 2 & 29.91 & 83.96 & 1975.5 & 87.17 \\  & 3 & 22.77 & 63.92 & 1884.8 & 89.38 \\  & 4 & 28.12 & 78.94 & 2025.3 & 86.91 \\ \hline \hline Average & & 28.32 & 79.50 & 2,512.41 & 91.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Experimental result according to IoT application and reconfigurable situations. The experimental results, according to scheduling rules, are presented in Table 9 where it can be observed that the results followed the characteristics of the scheduling rules. According to the experiment, the rule that showed the best performance in terms of the number of satisfied demands was EDD, which was directly related to the due date. FIFO and SPT had similar performances, though SPT was a little better.