Review Article

The Importance of Feature Processing in Deep-Learning-Based Condition Monitoring of Motors

Table 7

Strengths and drawbacks of DL models.

DL modelStrengthsDrawbacks

MLP [47, 83](i) Can work with clean, balanced, and scaled data, regardless of the data type
(ii) Integration in real-time systems is easy and allows one-dimensional data analysis
(i) Requires a lot of tuning to work on dirty or unscaled data
AE [118, 127](i) Allows to learn rich representations and reduces dimensionality
(ii) Can work as a denoising technique to get cleaner data
(iii) Easy implementation
(i) Requires massive training data and training time
(ii) Poses difficulty in discriminating relevant data
DBN [76, 77](i) Can achieve higher level of generalization on one-dimensional raw data(i) Slow training and inefficient
DBM [75, 128](i) Allows for one-dimensional data analysis
(ii) Combined optimization of all the layer parameters
(i) Slower training than DBN and inefficient
(ii) Combined optimization becomes impractical for large data
CNN [10, 83](i) Fits well for multidimensional data analysis
(ii) Enables for feature extraction from raw data
(i) Complex architecture
(ii) Requires large datasets and takes long training time
(iii) Estimations of continuous data are poor
RNN/LSTM/GRU [83, 113, 129](i) Performs well with time series or sequential data
(ii) Better forecasting ability in time series and sequential data
(i) Without proper constraints on weights and gradient clipping, might suffer from the gradient either vanishing or becoming unbounded
GAN [115, 116, 130](i) Learns underlying representation of data well
(ii) Seems to achieve a discriminator with less generalization error where its generator output (fake data) provides a regularization effect
(iii) Only algorithm that can work in semisupervised or even unsupervised setting to identify under observation clusters
(iv) Model with high fidelity
(i) Very complex architecture and implementation is even difficult
(ii) Difficult to model discrete data
(iii) Perhaps not suitable for real-time implementation