Fig. 3. Working process5. Results and Discussion5.1. Accuracy comparison
Fig.
4 is the result of HS model predicting the total lifetime failure rate
of 98 ship engines. Spots are points of failure with 98 data.
Considering the missing data in the early period due to Âwarranty repair
(as in section 3.1), they are bathtub-formed, as some previous
literature has suggested (as in section 2.2). Among the models
introduced in section 2.2, Prophet and Arima are selected as baseline
models each for its high accuracy and popularity, respectively.
Accuracy comparison was performed in two ways considering the model’s
application situation. In general, when it is necessary to introduce a
new ship engine or predict the ship engine in use, refer to the data of
the same engine type. The prediction accuracy of the ship engine is used
as a reference to predict the spare parts of the ship engine in use, and
the prediction accuracy between the engine type and the ship engine is
used as a reference when introducing a new ship engine. Therefore, first
(Table 1), the accuracy of ship engine predicted and ship engine actual
values were compared, and second (Table 2), the accuracy of engine type
predicted and ship engine actual values were compared. RMSE (Root Mean
Square Error) was used for the error measure.
Table 1. RMSE (Ship engine predicted VS Ship engine actual)