Noise-dependent ranking of prognostics algorithms based on discrepancy without true damage information

In this paper, an interesting observation on the noise-dependent performance of prognostics algorithms is presented. A method of evaluating the accuracy of prognostics algorithms without having the true degradation model is proposed. This paper compares the four most widely used model-based prognostics algorithms, i.e., Bayesian method, particle filter, Extended Kalman filter, and nonlinear least squares, to illustrate the effect of random noise in data on the performance of prediction. The mean squared error (MSE) that measures the difference between the true damage size and the predicted one is used to rank the four algorithms for each dataset. We found that the randomness in the noise leads to a very different ranking of the algorithms for different datasets, even though they are all from the same damage model. In particular, even for the algorithm that has the best performance on average, poor results can be obtained for some datasets. In absence of true damage information, we propose another metric, mean squared discrepancy (MSD), which measures the difference between the prediction and the data. A correlation study between MSE and MSD indicates that MSD can be used to estimate the ranking of the four prognostics algorithms without having the true damage information. Moreover, the best algorithm selected by MSD has a high probability of also having the smallest prediction error when used for predicting beyond the last measurement. MSD can thus be particularly useful for selecting the best algorithm for predicting into the near future for a given set of measurements.