# 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
#### 4.2.1 The Construction of Reference Degradation Model  
For the convenience of explanation, according to Step 1 in Section 3, select three similarity reference samples from the historical samples through measuring the similarity between the samples to be  
Figure 5: The information of the simulation dataset. (**a**) The partition of different operating condition. Three axes respectively denote three operating parameters, and each point in the figure denotes one specific operating condition decided by three different parameters. (**b**) The measured value of the sensor. (**c**) The standardization of measured value.  
Figure 6: The information of the selected life-cycle data. (**a**) The selected life-cycle data in set #2 of the turbofan engine simulation data. (**b**) The first 2/3 of the selected life-cycle used as the sample to be predicted. (**c**) The latter 1/3 of the selected life-cycle used to validate the result.  
predicted, which is shown in Figure 6b, and the historical sample. One of the similarity reference samples (as shown in Figure 7a) is used as an example to illustrate the construction process of the reference degradation model.  
As the description in Section 4.1, the simulation data have six operating conditions. Therefore, partition the similarity reference sample shown in Figure 7a into six parts according to the 3 operating parameters. The partitioned results are shown in Figure 7b. Then, as shown in Figure 7c, the standardized samples of the partitioned operating condition are obtained according to Equation (1). Extract the maximum value of each standardized sample as listed in Table 1. Select the maximum of the maximum values of each operating condition and calculate the threshold of each operating condition according to Equation (3). The thresholds are listed in Table 1. The reason for this treatment is that the  
Figure 7: The construction process of the reference degradation model. **(a)** One of the similarity reference samples, which is selected from the historical sample by measuring the similarity between the sample to be predicted and the historical sample. **(b)** The operating condition partition of the similarity reference sample. **(c)** The standardization of operating conditions. **(d)** The predicted degradation trend of each constant operating condition by RVM.  
original operating conditions are at different levels, while the standardized operating conditions are at the same level and have a uniform end point of life, as shown in Figure 5c. Therefore, the maximum of the standardized operating conditions is chosen as the end point of life to calculate the life threshold of each operating condition, respectively. The following step is that each operating condition is predicted by RVM according to the life threshold of each operating condition, as shown in Figure 7d. Finally, the reference degradation model is constructed based on the predicted degradation trend and lifecycle. The remaining two similar reference samples are also processed in the same way to construct the degradation models.