## 4 Results
### Experimental Wireless Transmission of Features Using Edge Processing
From the experimental data, the mean of the 11 N tightening torque interval was 307,968.7 and the mean of the 1 N tightening torque interval was 204,376.7, so a threshold value of 256,172.7 was set. A cycle with a tightening torque of 11 N is judged to be a cycle with a tightening torque of 11 N if it is greater than or equal to this threshold  
Figure 21: Dispersion values immediately after the start of uniform motion from the right end to the left end, as displayed in the web application. value, and a cycle with a tightening torque of 1 N is judged to be a section with a tightening torque of 1 N if it is less than this threshold value. The confusion matrices resulting from the threshold judgement for the 641 cycles in each section are shown in Table 1.  
The number of correctly determined cycles was 1027, giving a correctness rate of 80.0%. This result shows that the correct judgement of the tightening torque can be made with an accuracy of 80% by using a threshold to judge the dispersion value of only one cycle. Focusing on the incorrect judgement results, the proportion of incorrect judgement of the tightening torque 11 N was 24.5 % and the proportion of incorrect judgement of the tightening torque 1 N was 15.3%, with the proportion of incorrect judgement of the tightening torque 11 N being higher. Therefore, there is a high possibility that a false alarm is generated to indicate that a bolt is loose even though it is not loose. To improve this result, a moving average of 20 points was applied in this evaluation experiment to reduce the influence of cycle-by-cycle variations. The visualisation page of the web application when a moving average of 20 points is applied is shown in Figure 22.  
The part where the dispersion value decreased significantly around 17:15 is the part where the ball screw was stopped to change the tightening torque of the support using a torque spanner, which is the effect of the 20-point moving average. The graph shows that the dispersion values in the section with a tightening torque of 11 N exceed the dispersion values in the section with a tightening torque of 1 N. Here, a value between the minimum value in the 11 N tightening torque section and the minimum value in the 1 N tightening torque section is used as the threshold value. From the experimental data, the minimum value in the 11 N tightening torque section was 269,984.3 and the maximum value in the 1 N tightening torque section was 259,078.9, so 258,741.0 is set as the threshold value. The threshold value was used to determine the tightening torque in the same way as in the case where no moving average was applied. The confusion matrices resulting from the threshold judgement for the 621 cycles of each interval are shown in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Results** & \\ \cline{2-4}  & & **11 N** & **1 N** \\ \hline \multirow{2}{*}{Actual torque} & 11 N & 484 & 157 \\ \cline{2-4}  & 11 N & 98 & 543 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Confusion matrix of decisions using thresholds. Figure 22: Variance values immediately after the start of uniform motion from the right end to the left end, as displayed in the web application (20-point average). The number of correctly judged cycles was 1241, giving a correct answer rate of 99.999%. In particular, there was one sample in which a tightening torque of 1 N was incorrectly judged as a tightening torque of 11 N, but there was no sample in which a tightening torque of 11 N was incorrectly judged as a tightening torque of 1 N. The result was that no false alarms were generated when the bolt was not loose. These results indicate that, when detecting bolt looseness on the support side of a ball screw, the average of the dispersion values of 20 consecutive cycles can be used instead of using only the dispersion values of one cycle. The results show that detection with high accuracy is possible by using the average of the dispersion values of 20 consecutive cycles.