Review of vision-based steel surface inspection systems

Table 2 List of defect classification methods

Method	Reference	Type of steel surface
Supervised classifier
K-nearest neighbour (KNN)	[1]	Cold strip
K-nearest neighbour (KNN)	[37]	Misc
NN-BP	[28, 32, 36]	Hot strip
	[77, 54, 63, 31, 78, 79, 72, 80]	Cold strip
	[59]	Rod/bar
SVM	[64, 65, 33, 67, 47]	Slab, plate, billet
	[70, 24]	Hot strip
	[81, 82, 25, 83, 84]	Cold strip
	[85, 44, 5, 2],	Rod/bar
	[86]	Misc
Max-pooling convolutional NN	[80]	Cold strip
Discriminant function	[42, 35]	Cold strip
Fuzzy logic-based classifier	[25, 87, 76, 88]	Cold strip
Unsupervised classifier
Self-organising map (SOM)	[36]	Hot strip
Self-organising map (SOM)	[43, 34]	Cold strip
Learning vector quantiser (LVQ)	[62]	Hot strip
Learning vector quantiser (LVQ)	[89]	Cold strip