# A New Life Prediction Scheme for Mechanical System with Considering the Mission Profile Switching
## 4 Results and Discussion
### The Life Prediction Under Mission Profile Switching
#### 4.2.2 The Life Prediction According to Specific Task Requirement  
First, consistent with the operating condition partition of similarity reference samples, the sample to be predicted (as shown in Figure 6b) is partitioned into six parts according to the 3 operating parameters. For each constant operating condition of the sample to be predicted, the life candidate sets and weights under corresponding operating condition are obtained by STM according to the corresponding operating condition in reference degradation models. For the sample shown in Figure 6b, the weights of each operating condition are shown in Table 2. Since the initial state of the data in set #2 is different, the life candidate sets are the difference between the initial point of similarity and the lifecycle of corresponding operating condition of historical sample. The initial points and lifecycle of the similarity reference samples are shown in Table 3 and the life candidate sets of each operating condition are shown in Table 4. Then, according to the weights and life candidate sets, the life of each operating condition can be obtained by Equation (4) and the results are listed in Table 5. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Operating Condition** & **1** & **2** & **3** & **4** & **5** & **6** \\ \hline The maximum value & 2.7825 & 2.8591 & 2.2072 & 2.9129 & 1.7876 & 2.6509 \\ The threshold & 1364.9 & 1379.3 & 1610.8 & 1497.9 & 1276.1 & 1514.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The maximum value and threshold of each operating condition. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Operating Condition**} & \multicolumn{4}{c}{**Similarity Reference Sample**} \\ \cline{2-5}  & **1** & **2** & **3** \\ \hline
1 & 14 & 406 & 3 & 362 & 31 & 334 \\
2 & 7 & 351 & 18 & 339 & 12 & 356 \\
3 & 5 & 380 & 4 & 322 & 10 & 353 \\
4 & 6 & 342 & 18 & 310 & 8 & 336 \\
5 & 9 & 353 & 13 & 338 & 9 & 364 \\
6 & 9 & 375 & 3 & 358 & 2 & 346 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The life information of similarity reference sample. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Operating Condition**} & \multicolumn{4}{c}{**Similarity Reference Sample**} \\ \cline{2-5}  & **1** & **2** & **3** \\ \hline The maximum value & 2.7825 & 2.8591 & 2.2072 & 2.9129 & 1.7876 & 2.6509 \\ The threshold & 1364.9 & 1379.3 & 1610.8 & 1497.9 & 1276.1 & 1514.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The maximum value and threshold of each operating condition. For the sample to be predicted, as shown in Figure 6b, the mission profile in the prediction is assumed to be that experienced by the latter 1/3 data. The mission profile of the latter 1/3 data (shown in Figure 6c) is shown in Figure 8 according to the 3 operating parameters, and the proportions of each operating condition in the mission profile are listed in Table 6. According to Equation (5), the life of the sample to be predicted under the mission profile experienced by the latter 1/3 data is 334.1180 cycle, which is very close to the actual life of the sample to be predicted. In addition, the proposed method not only can obtain the prediction results under the above mission profile, but can also obtain the corresponding results even if the mission profile is switched during the prediction process. According to the predicted life of each operating condition and the proportions of the operating conditions in the mission profile, the corresponding results can be obtained by Equation (5). As shown in Table 7, the sample to be predicted (shown in Figure 6b) is assumed to be in the following 3 mission profiles in the prediction. The information of the mission profile is listed in Table 7, and the predicted result under the corresponding mission profile is also listed in Table 7. Therefore, the proposed method can deal well with the problem of mission profile switching in the prediction.