# Remote Sensing of Sewing Work Levels Using a Power Monitoring System
## 3 Methodology
### Experiments  
Experiments measuring \(L_{S}\) and \(L_{D}\) were performed on a sample production line at a garment manufacturing factory in Indonesia. According to the judgment of expert line managers, fifteen sewing machine operators were selected with three operators in each skill level from \(L_{S}\)1 to \(L_{S}\)5. In addition, the sewing line design experts recommended five tasks for each difficulty level from \(L_{D}\)1 to \(L_{D}\)5, representing the different levels of difficulty in sewing a single type of hooded jacket, excluding the final assembly work. The test operators were selected by considering the manager's empirical observations based on the working period, and the production tasks were selected by the production department after considering the detailed work procedures. However, the details considered in selecting the targets are closely related to the company's sensitive business information; therefore, they are not recorded in detail in this study. In addition, the experimental results may be distorted if the operators recognize that their performance is being measured. The power monitoring system proposed in this study is always connected to the sewing machine so that operators do not recognize when their performance is being measured. Therefore, a more reliable experiment is possible than the manual measurement method. Table 1 shows the experimental targets selected for \(L_{S}\) and \(L_{D}\) measurements.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Operator No.** & **Skill Level** & **Process No.** & **Diffoculty Level** & **Task Figure** & **Estimated Task Time (Sec)** \\ \hline
2 & \(L_{S}\)1 & 1 & \(L_{D}\)1 & & 19 \\ \hline
3 & & & & & \\ \hline
4 & & & & & \\ \hline
5 & \(L_{S}\)2 & 2 & \(L_{D}\)2 & & 14 \\ \hline
6 & & & & & \\ \hline
7 & & & & & \\ \hline
8 & \(L_{S}\)3 & 3 & \(L_{D}\)3 & & 115 \\ \hline
9 & & & & & \\ \hline
10 & & & & & \\ \hline
11 & \(L_{S}\)4 & 4 & \(L_{D}\)4 & & 115 \\ \hline
12 & & & & & \\ \hline
13 & & & & & \\ \hline
14 & \(L_{S}\)5 & 5 & \(L_{D}\)5 & & 94 \\ \hline \end{tabular}
\end{table}
Table 1: Experimental operators and selected tasks.  
Before the experiment, the experts who selected the experimental targets provided their opinions regarding appropriate weights for \(L_{S}\) and \(L_{D}\). These weight factors are used to account for the relative difference between skill/difficulty levels. For example, assuming a reference value of 3 as being in the middle of levels 1 to 5, the weight factor would be defined as \"1\". The \(L_{S}\) and \(L_{D}\) weight factors can then be applied when calculating the performance of the operator (\(P_{O}\)) to derive a more realistic level of production. Although they rely on empirical knowledge and thus use no clear, quantifiable criteria for time and quality, the weights for each level were assumed by the experts as shown in Figure 4.  
The experiment was conducted over two days. On the first day, the PMS was used to measure the performance of three tasks by three operators at each skill level (\(L_{S}\)1 to \(L_{S}\)5) at every level of difficulty (\(L_{D}\)1 to \(L_{D}\)5). After the measurements, the quality of each work result was evaluated according to three grades: A, B, or C, where A is a work product completely free of defects, B is a work product that can be vaguely judged to be defective but only partially lacking in quality, and C is an unsuccessful work product. On the second day, three additional measurements were performed for each operator at every level of difficulty using the PMS following the same procedure as on the first day. As a result, a total of 30 jobs were measured for each operator at \(L_{D}\)1 to \(L_{D}\)5, and the time and quality of a total of 450 jobs performed by 15 operators were measured.